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International audience; Plasma lipid content and composition are studied in dairy cows and goats fed similar diets inducing milk fat depression (MFD) only in cows. Twelve cows and 15 goats are fed a diet without additional lipids (control), or supplemented with fish oil (FO), or supplemented with sunflower oil plus starch (SOS) in a 3 × 3 Latin square design. A high‐performance thin‐layer chromatography (HP‐TLC) methodology is used to separate and quantify the following plasma lipid classes: cholesterol esters (CE), triglycerides (TG), free fatty acids (FFA), cholesterol (Chol), and phospholipids (PL). The plasma lipid composition reveales that TG concentration is 193% higher in the goats compared to the cows. For cows and goats, FO increases CE (+31%) and Chol levels (+33.7%) compared to the control. The TG concentration is differentially regulated by FO between cows (−23.5%) and goats (no change). In the goats, SOS increases CE (+25.7%), Chol (+46.7%), and FFA levels (+71.7%) compared to the control. These results suggest the existence of different mechanisms of lipid digestion, absorption, and transport between cows and goats and contribute to better understand the differences in the regulation of milk fat secretion responses to lipid supplementation between cows and goats. Practical Applications: A robust HP‐TLC methodology for plasma lipid separation and analysis in automated and reproducible conditions is developed which constitutes an original part of the present study. It has been shown that intake of plant‐derived lipids associated with starch‐rich diets decreases the milk fat content in cows but not in goats. Therefore, the direct species comparison model used in the present study constitutes an interesting tool to compare the responses of plasma lipid concentrations and FA composition in cows and goats fed fish oil or sunflower oil and starch supplemented diets. The direct comparison between cows and goats in plasma lipid class composition is reported for the first time in the present study, with in addition new information about the contribution of intermediary metabolism to differences between the two species in the regulation of milk fat secretion in response to lipid supplementation.

International audience; We investigated the effects of increasing extruded linseed supply in diets based on hay (H; experiment 1) or corn silage (CS; experiment 2) on enteric methane (CH4) emission, rumen microbial and fermentation parameters, and rumen and total-tract digestibility. In each experiment, 4 lactating Holstein cows fitted with cannulas at the rumen and proximal duodenum were used in a 4 x 4 Latin square design (28-d periods). Cows were fed ad libitum a diet [50:50 and 60:40 forage:concentrate on a dry matter (DM) basis for experiments 1 and 2, respectively] without supplementation (H0, CS0) or supplemented with extruded linseed at 5% (H5, CS5), 10% (H10, CS10), and 15% (H15, CS15) of dietary DM (i.e., 1.8, 3.6 and 5.4% total fatty acids added, respectively). All measurements were carried out during the last 8 d of each period. Linseed supply linearly decreased daily CH4 emission in cows fed H diets (from 486 to 289 g/d for H0 to H15, on average) and CS diets (from 354 to 207 g/d for CS0 to CS15, on average). The average decrease in CH4 per kilogram of DM intake was, respectively, 7, 15, and 38% for H5, H10, H15 compared with the H0 diet, and 4, 8, and -34% for CS5, CS10, and CS15 compared with the CS0 diet. The same dose-response effect was observed on CH4 emission in percent of gross energy intake, per kilogram of nutrient digested, and per kilogram of 4% fat- and 3.3% protein-corrected milk (FPCM) in both experiments. Changes in the composition of rumen volatile fatty acids in response to increasing linseed supply resulted in a moderate or marked linear decrease in acetate:propionate ratio for H or CS diets, respectively. The depressive effect of linseed on total protozoa concentration was linear for H diets (-15 to -40%, on average, for H5 to H15 compared with H0) and quadratic for CS diets (-17 to -83%, on average, for CS5 to CS15 compared with CS0). Concentration of methanogens was similar among H or CS diets. The energetic benefits from the decreased CH4 emission with linseed supply in diets based on hay or corn silage did not improve digestibility or milk yield. Milk efficiency (kg of FPCM/kg of DM intake) was improved with linseed supply up to H10 in H diets and was unchanged in CS diets. Lower CH4 enteric emission from dairy cows fed linseed helps limit the environmental footprint of ruminant livestock.

Background: Fatty acid (FA) composition plays a crucial role in milk nutritional quality. Despite the known nutritional regulation of ruminant milk composition, the overall mammary mechanisms underlying this regulation are far from being understood. The aim of our study was to determine nutritional regulation of mammary transcriptomes in relation to the cow milk composition. Methods: Twelve cows received diets differing in the forage-to-concentrate ratio [high forage (HF) and low forage (LF)] supplemented or not with lipids [HF with whole intact rapeseeds (RS) and LF sunflower oil (SO)] in a 4 × 4 Latin square design. Milk production and FA composition were determined. The gene expression profile was studied using RT-qPCR and a bovine microarray. Results: Our results showed a higher amplitude of milk composition and mammary transcriptome responses to lipid supplementation with the LF-SO compared with the LF diet than with the HF-RS compared with the HF diet. Forty-nine differentially expressed genes, including genes involved in lipid metabolism, were identified with LF-SO versus LF, whereas RS supplementation to the HF diet did not affect the mammary transcriptome. Conclusions: This study highlights different responses to lipid supplementation of milk production and composition and mammary transcriptomes depending on the nature of lipid supplementation and the percentage of dietary concentrate.

International audience; Nutrition is a major factor that regulates ruminant milk components, particularly its fatty acid (FA) composition, which is an important determinant of milk nutritional quality. In the mammary gland, milk component biosynthesis involves a large number of genes under nutritional regulation that are not well understood. Thus, the objective of the present study was to evaluate the effects of extruded linseeds (EL) alone or in combination with fish oil (ELFO) on goat mammary gene expression. In total, 14 goats were fed one of the following three diets: a natural grassland hay basal diet (CTRL) alone, CTRL supplemented with 530 g/day of EL, or 340 g/day of EL plus 39 g/day of fish oil (ELFO). Mammary secretory tissues were collected after slaughter on day 28, to determine the expression of 14 lipogenic genes and five lipogenic enzyme activities and transcriptomic profiles. The mRNA abundance decreased for SCD1 ( P

n-3 highly unsaturated fatty acids (n-3 HUFA) directly and indirectly regulate lipid metabolism, energy balance and the inflammatory response. We investigated changes to the n-3 HUFA score of healthy adults, induced by different types and amounts of conjugated linoleic acid (CLA)-enriched (ENCH) cheeses consumed for different periods of time, compared to dietary fish oil (FO) pills (500 mg, each containing 100 mg of eicosapentaenoic and docosahexaenoic acids&mdash, EPA+DHA) or &alpha, linolenic acid (ALA)-rich linseed oil (4 g, containing 2 g of ALA). A significant increase in the n-3 HUFA score was observed, in a dose-dependent manner, after administration of the FO supplement. In terms of the impact on the n-3 HUFA score, the intake of ENCH cheese (90 g/day) for two or four weeks was equivalent to the administration of one or two FO pills, respectively. Conversely, the linseed oil intake did not significantly impact the n-3 HUFA score. Feeding ENCH cheeses from different sources (bovine, ovine and caprine) for two months improved the n-3 HUFA score by increasing plasma DHA, and the effect was proportional to the CLA content in the cheese. We suggest that the improved n-3 HUFA score resulting from ENCH cheese intake may be attributed to increased peroxisome proliferator-activated receptor alpha (PPAR-&alpha, ) activity. This study demonstrates that natural ENCH cheese is an alternative nutritional source of n-3 HUFA in humans.

International audience; Based on the potential benefits for long-term human health, there is interest in developing sustainable nutritional strategies for lowering medium-chain saturated fatty acids (FA) and increasing specific unsaturated FA in ruminant milk. Dietary supplements of extruded linseeds (EL), fish oil (FO) or a mixture of EL and FO increase cis-9,trans-11 CLA and long-chain n-3 polyunsaturated FA in bovine milk. Supplements of FO cause milk fat depression in lactating cows, but information for dairy goats is limited. A total of 14 Alpine goats were used in a replicated 3×3 Latin square with 28-days experimental periods to examine the effects of EL alone or in combination with FO on animal performance, milk fat synthesis and milk FA composition. Treatments comprised diets based on natural grassland hay supplemented with no additional oil (control), 530 of EL or 340 g/day of EL and 39 g/day of FO (ELFO). Compared with the control, ELFO tended (P=0.08) to lower milk fat yield, whereas EL increased (P

Impaired quality due to a high content of free fatty acids (FFA) and off-flavors has caused challenges in the development of Norwegian goat milk products. The present study aimed to examine the effect of lipid-supplemented concentrates on milk fat content, fatty acid composition, FFA, lipoprotein lipase activity, sensory properties, and size of milk fat globules of goat milk. Thirty goats assigned to 3 experimental groups were fed different concentrates from 60 d in milk (DIM) until late lactation (230 DIM). The diets were (1) control concentrate (no added fat); (2) control concentrate with 8% (added on air-dry basis) hydrogenated palm oil enriched with palmitic acid (POFA); and (3) control concentrate with 8% (added on air-dry basis) rapeseed oil (RSO). The POFA group produced milk with the highest fat content, and fat content was positively correlated with the mean size of milk fat globules. Goats in the RSO group had a higher content of long-chain and unsaturated fatty acids, whereas milk from goats in the POFA group had a higher content of palmitic and palmitoleic acids (C16:0 and C16:1 cis). The control group produced milk with a higher content of short-, medium-, odd-, and branched-chain fatty acids compared with the 2 other groups. The content of FFA in milk was low in early and late lactation and peaked in mid lactation (90 DIM). A high content of FFA was correlated with poor sensory properties (tart/rancid flavor). The RSO group produced milk with lower content of FFA and off-flavors in mid lactation and a higher proportion of unsaturated fatty acids. Therefore, replacement of palm oil with rapeseed oil as a lipid source in dairy goat feed would be favorable.

14 páginas, 6 tablas., A direct comparison of cow and goat performance and milk fatty acid (FA) responses to diets known to induce milk fat depression in the bovine has suggested interspecies differences in rumen and mammary lipid metabolism. Thus, this study was conducted to infer some potential mechanisms responsible for the differences in mammary lipogenesis due to diet and ruminant species. To meet this objective, 12 cows and 15 goats were fed a basal diet (control), a similar diet supplemented with 2.2% fish oil (FO), or a diet containing 5.3% sunflower oil and additional starch (+38%; SOS) according to a 3 × 3 Latin square design with 26-d experimental periods. Milk yield, milk composition, FA profile, and FA secretion were measured. On the last day of each period, the mRNA abundance of 19 key genes in mammary metabolism or the enzyme activity or both were measured in mammary tissue sampled by biopsy or at slaughter or both. The results show significant differences in the response of cows and goats to the dietary treatments. In cows, milk fat content and yield were lowered by FO and SOS (−31%), whereas only FO decreased milk fat content in goats (−21%) compared with the control. In cows and to a lesser extent in goats, FO and SOS decreased the secretion of C16 FA output (mmol/kg of BW). However, SOS increased the secretion of >C16 FA in goats. These changes in milk fat content and FA secretion were not associated with modifications in mammary expression or the activity of 19 proteins involved in the major lipogenic pathways. This absence of variation may be attributable to posttranscriptional regulation for these genes or related to the time of sampling of the mammary tissue relative to the previous meal and milking. Otherwise, the abundances of 15 mRNA among the 19 encoding for genes involved in lipid metabolism in the mammary gland were different among species, with 9 more abundant in cows (FASN, FADS1, SCD1, GPD1, LALBA, SREBF1, LXRA, PPARA, and PPARG1) and 6 more abundant in goats (G6PD, GPAM, SCD5, XDH, CSN2, and SP1). Similarly, a significant effect of the species was observed in the 4 enzyme activities measured; glycerol-3-phosphate dehydrogenase and malic enzyme were higher in cows, and FA synthase and glucose-6-phosphate dehydrogenase activities were higher in goats. In conclusion, the differences between cow and goat performance and milk FA responses to the FO and SOS treatments were not related to changes in the measured mammary lipogenic gene expression. Furthermore, the data provide evidence that the major mammary lipogenic pathways differ between the caprine and the bovine, whose biological significance remains to be unraveled., This study is dedicated to Kevin Shingfield, who passed away during the redaction of the paper. Kevin collaborated for a while with our team and added much to our work. Pablo G. Toral was granted a postdoctoral fellowship from the Fundación Alfonso Martín Escudero (Madrid, Spain). The authors gratefully acknowledge Jacques Rouel for assistance during the animal feeding experiment and with statistics; the staff of Unité Expérimentale des Ruminants de Theix [L’Institut National de la Recherche Agronomique INRA, SaintGenes-Champanelle, France] for the diligent care of the experimental animals; Philippe Gaydier, Simon Collange, Julien Mongiat, Dominique Roux, and Denys Durand for the collection of the mammary biopsies; and Sébastien Bes, Cyril Labonne, and Yannick Faulconnier from UMR 1213 Herbivores (INRA, Theix, France) for assistance in sampling collection and laboratory analysis. The advice of Christine Leroux (UMR 1213 Herbivores, INRA, Theix, France) during this work is acknowledged and appreciated.

Trabajo presentado al: 15th Euro Fed Lipid Congress. Oil, fats and lipids: new technologies and applications for a healthier life. ANIM-001. (Uppsala, Suecia. 27-30 agosto 2017).

The objective of this experiment was to examine how supplements of rapeseed oil or palm oil fatty acids would affect milk production and composition, body lipid stores, and energy balance in 30 multiparous goats of Norwegian dairy goat breed. The experiment lasted 230 d, with 1 to 120 d in milk (DIM) for indoor feeding (P1), 120 to 200 DIM for mountain grazing (P2), and 200 to 230 DIM for indoor feeding (P3). Grass silage was fed according to appetite during indoor feeding periods. After an adjustment period (1-60 DIM) when the control diet was given to the goats, the animals were subdivided into 3 groups of 10 goats. Treatments (60-230 DIM) were (1) basal concentrate (control; no added fat); (2) control concentrate with 8% (added on air-dry basis) hydrogenated palm oil enriched with palmitic acid (POFA); and (3) control concentrate with 8% (added on air-dry basis) rapeseed oil (RSO). Individual energy balances based on energy intake and milk production were estimated on 10, 30, 60, 90, 120, 200, and 230 DIM. At the same times, body weight (BW), body condition score (BCS), body mass index, and body tissue stores using computed tomography were monitored. Silage intake was depressed by POFA throughout the experimental period. Reduced BW and body mass index were observed in the POFA and RSO groups, whereas no effect on BCS or body composition was observed throughout lactation. Generally, a minor decrease in BW was observed from 10 to 120 DIM (only 0.6 kg on average) and the total amount of body lipid was reduced by 4.4 kg. During the mountain grazing period, a further reduction in body lipid stores (2.7 kg) was observed, and BW was reduced by 3.9 kg in the same period. The goats mobilized, on average, 72% of their fat reserves during the first 200 DIM. In this period, dietary fat supplementation did not reduce the mobilization of adipose tissue but resulted in greater milk fat yield (2 kg more, on average, compared with the control group). Milk yield was not affected by POFA or RSO supplementation. Milk fat content was higher in the POFA group than in the control and RSO groups. Milk protein and lactose contents were not affected by lipid supplements. In late lactation, a rapid accumulation of fat deposits followed the intense mobilization during the grazing period. Dietary lipid supplements had no effect on milk fat yield at this stage. Milk production depends heavily on the ability to mobilize body lipid stores, and neither POFA nor RSO supplements at rates used in our study affected this mobilization.

This study compares two groups of 23 and 24 goats with different CSN1S1 genotypes, matched for lactation number and stage. During the first experimental period (4 weeks) half of the goats of each genotype received the control diet (CT) and the second half received a similar diet containing extruded linseed (EL diet). During the second experimental period, the two groups of goats were switched from the CT to the EL diet and from the EL to the CT diet, respectively. Results confirm the lower milk protein (-4.8 g/kg) and fat (-6.5 g/kg) concentrations in the low genotype group, whereas milk yield was slightly higher (+0.49 kg/d) and lactose concentration was unchanged. Between the genotype groups, there were differences in milk fat proportions of at least 25 FAs, particularly the C7 to C13 saturated FAs and C16:0, C18:0, C18:2n-6 and cis9,trans11-C18:2 acids. In addition, delta-9 desaturation ratios were higher in the low CSN1S1 group for C10:0, C14:0, C18:0, trans11-C18:1 and trans13-C18:1. This strongly suggests an effect on mammary delta-9 desaturase activity, especially for C18:0 and trans11-C18:1. It is likely that higher desaturation ratios in the low genotype, as well as observed changes in other FAs, could compensate for the lower synthesis of medium-chain FAs (C7:0-C13:0), thus contributing to maintenance of the melting point of milk fat in this genotype. The effect of the EL diet on milk FA proportions was highly significant for almost all FAs, along with increased milk fat content and decreased post-milking free FA concentration. Numerous interactions (significant but Of limited quantitative extent) between the CSN1S1 genotype and EL feeding were shown on milk composition, including 26 FA proportions or delta-9 desaturation ratios, and post-milking free FA concentration. (C) 2013 Elsevier B.V. All rights reserved.

International audience; The effect of supplementation of increasing amounts of extruded linseed in diets based on hay (H; experiment 1) or corn silage (CS; experiment 2) was investigated in regard to dairy performance and the milk fatty acid (FA) composition. In each experiment, 4 lactating multiparous Holstein cows were used in a 4 x 4 Latin square design (28-d periods). The cows were fed a diet (50:50 and 40:60 concentrate:forage ratio for experiments 1 and 2, respectively; dry matter basis) without supplementation (H0 or CS0) or supplemented with 5% (H5 or CS5), 10% (H10 or CS10), or 15% (H15 or CS15) of extruded linseed. Regardless of the forage type, diet supplementation with increasing amounts of extruded linseed had no effect on the dry matter intake, milk yield, or protein content or yield. In contrast, the milk fat content decreased progressively from H0 to H10 diets, and then decreased strongly with the H15 diet in response to increasing amounts of extruded linseed. For CS diets, the milk fat content initially decreased from CS0 to CS10, but then increased with the CS15 diet. For the H diets, the milk saturated FA decreased (-24.1 g/100 g of FA) linearly with increasing amounts of extruded linseed, whereas the milk monounsaturated FA (+19.0 g/100 g), polyunsaturated FA (+4.9 g/100 g), and total trans FA (+14.7 g/100 g) increased linearly. For the CS diets, the extent of the changes in the milk FA composition was generally lower than for the H diets. Milk 12:0 to 16:0 decreased in a similar manner in the 2 experiments with increasing amounts of extruded linseed intake, whereas 18:0 and cis-9 18:1 increased. The response of total trans 18:1 was slightly higher for the CS than H diets. The milk trans-10 18:1 content increased more with the CS than the H diets. The milk cis-9,trans-11 conjugated linoleic acid response to increasing amounts of extruded linseed intake was linear and curvilinear for the H diets, whereas it was only linear for the CS diets. The milk 18:3n-3 percentage increased in a similar logarithmic manner in the 2 experiments. It was concluded that the milk FA composition can be altered by extruded linseed supplementation with increasing concentrations of potentially health-beneficial FA (i.e., oleic acid, 18:3n-3, cis-9,trans-11 conjugated linoleic acid, and odd- and branched-chain FA) and decreasing concentrations of saturated FA. Extruded linseed supplementation increased the milk trans FA percentage.

Indirect comparisons from studies in vivo have suggested that caprine mammary tissue is less sensitive than bovine mammary tissue to the anti-lipogenic effect of long-chain fatty acids (LCFA), including specific rumen biohydrogenation (RBH) intermediates of polyunsaturated fatty acids (PUFA). Our objective was to investigate the effects on lipogenesis of 18-carbon LCFA differing in the degree of unsaturation and/or double bond conformation using cultured slices of bovine and caprine mammary tissues. Mammary tissues were collected from five multiparous Holstein × Normande cows and six multiparous Alpine goats in mid lactation. The expression of genes involved in milk component synthesis was measured in tissues collected at slaughter and after slice preparation:FASN, SCD1, CD36, SREBF1andPPARG1mRNA levels were higher in bovine than caprine samples, whereas the opposite was observed forCSN2mRNA levels. Bovine and caprine mammary slices were incubated for 20 h in a medium with BSA (control), cis-9-18 : 1, 18 : 2n-6, 18 : 3n-3, cis-9, trans-11-CLA, or trans-10, cis-12-CLA (the latter at 3 increasing concentrations: C1 (0·11 mm), C2 (0·16 mm), C3 (0·37 mm)). Lipogenesis was estimated by measuring the incorporation of14C-acetate into total lipid. Significant differences of individual LCFA (P

12 páginas, 3 tablas., Based on the potential benefits for long-term human health, nutritional strategies have been developed in order to increase the milk fat concentrations of bioactive fatty acids (FA) in ruminants. Dietary supplements of fish oil (FO), extruded linseed (EL) or a mixture of EL and FO increase c9,t11-CLA and n-3 PUFA in milk from bovine and caprine. These supplements associated with a high level of starch from concentrates cause milk fat depression in cows, but information for dairy goats is limited. An experiment was performed to investigate the effects of addition of extruded linseed to a diet containing fish oil in interaction with the type and level of starch concentrate on dairy goat performance and milk fatty acid (FA) profile. Following a 2 × 3 factorial design, 72 goats were allocated to 6 experimental diets based on alfalfa hay and with concentrates including fish oil (40 g/d) without or with extruded linseed (360 g/d) and either rich in starch from barley grain or extruded wheat or that were low in starch from barley grain. In contrast to cows, in goats adding extruded linseed to low-or high-starch diets based on hay and containing fish oil increases milk fat content and changes the milk FA composition in particular by increasing some bioactive FA with 18 carbons. In these conditions FA changes were characterized by decreases in SFA (on average 22% decrease) and increases in 18:0, c9-18:1, t11-18:1, c9,t11-CLA and 18:3n-3. The milk t10-18:1 concentration remained low (, P.G. Toral was granted a post-doctoral fellowship from Fundación Alfonso Martín Escudero (Madrid, Spain).

International audience; The aim of this study was to evaluate the effects of long-term supplementation with different oilseeds rich in 18:1 cis-9 or 18:3n-3 fatty acids on dairy cow performance over 2 consecutive lactations. This trial involved 58 Holstein cows during the first year and 35 during the second year. During the first 5 wk of the first year, all of the cows were fed the same diet; after a 4-wk transition period, the cows received 1 of 5 treatments for 2 consecutive lactations, including the dry period. Their basal diet was supplemented or not with extruded linseeds or with different forms of rapeseeds: extruded seeds, cold-pressed fat-rich meal, or whole unprocessed seeds. Oilseed amount was calculated to provide 2.5 to 3.0% additional oil in ration dry matter. Cows were fed a grass-based diet (75% grass silage and 25% hay) during indoor periods and grazed during outdoor periods. For the first year of experimentation, oilseed supplementation had no effect on milk, fat, protein, and lactose yields, body weight, or body condition score compared with the control treatment (no oilseed supplementation). During the indoor period, extruded linseed tended to decrease dry matter intake (—1.5 kg/d), whereas all of the oilseed treatments decreased milk protein content without changing protein yield. Cold-pressed fat-rich rapeseed meal decreased milk protein content independently of the period (—0.29 and ―0.19 g/100 g for indoor and outdoor periods, respectively), and whole unprocessed rapeseed increased milk fat content during the outdoor period (+0.53 g/100 g compared with the control treatment). During the second year of experimentation, the effects of oilseed supplementation during the outdoor period were similar to those observed during the first outdoor period, but the effects of oilseed supplementation differed between the 2 indoor periods. This was likely due to changes in forage quality and composition and percentage in the ration of the concentrate mixtures. Thus, the effects of oilseed supplementation depended on oilseed nature (rapeseed or linseed) and form (extruded seeds, cold-pressed fat-rich meal, or whole unprocessed seeds) in interaction with the type of basal diet (grass silage and hay or pasture) and the concentrate composition and percentage in the ration. Effects were stable during the first indoor period, repeatable between the 2 outdoor periods, and were similar to effects observed previously in short-term studies (1 to 3 mo).

Epidemiological and fetal programming studies point to the role of fetal growth in adult adipose tissue (AT) mass in large mammals. Despite the incidence of fetal AT growth for human health and animal production outcomes, there is still a lack of relevant studies. We determined the cellular and large-scale-molecular features of bovine fetal perirenal AT sampled at 110, 180, 210, and 260 days post-conception (dpc) with the aim of identifying key cellular and molecular events in AT growth. The increase in AT weight from 110 to 260 dpc resulted from an increase in adipocyte volume and particularly adipocyte number that were concomitant with temporal changes in the abundance of 142 proteins revealed by proteomics. At 110 and 180 dpc, we identified proteins such as TCP1, FKBP4, or HSPD1 that may regulate adipocyte precursor proliferation by controlling cell-cycle progression and/or apoptosis or delaying PPARγ-induced differentiation. From 180 dpc, the up-regulation of PPARγ-induced proteins, lipogenic and lipolytic enzymes, and adipokine expression may underpin the differentiation and increase in adipocyte volume. Also from 180 dpc, we unexpectedly observed up-regulations in the β-subunit of ATP synthase, which is normally bypassed in brown AT, as well as in aldehyde dehydrogenases ALDH2 and ALDH9A1, which were predominantly expressed in mouse white AT. These results, together with the observed abundant unilocular adipocytes at 180 and 260 dpc, strongly suggest that fetal bovine perirenal AT has much more in common with white than with brown AT.

International audience; Linseed supplementation of dairy cows' diet increases unsaturated fatty acid (FA) concentrations, which could lead to oxidised off-flavours in dairy products if antioxidant content is low. The FA profiles and sensory properties of milk and uncooked pressed cheese (Saint-Nectaire type) from four groups of six cows receiving a corn silage-based diet with no additional lipid (control), or supplemented with extruded linseeds (5% of additional fat-in-dry matter intake; EL), EL and vitamin E (7500 IU per cow per day of DL-alpha-tocopherol; ELE), or ELE and plant extracts rich in carotenoids and polyphenols (1% of dry matter intake) were compared. Feeding EL decreased milk and cheese 4- to 16-carbon saturated FA, and increased 18:1 cis-9, 18:3n-3 and total trans FA concentrations. Extruded linseeds did not induce oxidised off-flavours but led to a less firm and more meltable texture in cheese. Vitamin E supplementation increased a-tocopherol concentration, but did not affect sensory properties.

La supplémentation en lin des rations des vaches laitières est une pratique qui se développe, avec pour objectifs l'amélioration de la qualité nutritionnelle du lait et la diminution des rejets de méthane. En effet, la recherche de laits moins riches en Acides Gras (AG) saturés et avec un rapport plus faible entre acide linoléique et acide linolénique, incite à utiliser des aliments riches en acides gras polyinsaturés (et en particulier en acide alpha-linolénique C18:3 n-3) pour corriger des rations insuffisamment riches en cet AGPI. Parmi les aliments des vaches laitières, le lin est un aliment particulièrement riche en C18:3 n-3. La diminution des rejets de gaz à effet de serre (dont le méthane) est également une préoccupation actuelle des filières animales. De nombreux essais de supplémentation en lin, sous différentes formes, ont été publiés ces dernières années, et les données disponibles permettent de tirer des conclusions sur ces effets attendus. Le présent article fait le point sur les disponibilités en lin et sur les différentes formes d'apport dans les rations. Les effets du lin sur la production laitière, sur la composition du lait et des produits laitiers, la production de méthane et la reproduction sont passés en revue. L’analyse des effets sur le lait s’appuie sur 41 essais zootechniques publiés. La culture de lin oléagineux est peu importante en France. L’approvisionnement est fait dans des pays européens et au Canada. Les variétés présentent des teneurs variables en acide alpha-linolénique. Résumé L’introduction de lin dans la ration diminue un peu la quantité de MS ingérée mais ne modifie en général pas la production laitière (volumes et taux). La teneur du lait en AG saturés diminue et le pourcentage en C18:1-trans est augmenté, et ce d’autant plus que l’apport de lipides se fait sous forme non protégée (graines extrudées, huile) et avec des rations riches en amidon (pour les AG trans). La teneur en C18:2 n-6 n’est en moyenne pas modifiée, sauf par l'apport d'huile. La proportion en C18:3 n-3 du lait est multipliée en moyenne par 2 ou 3 pour les formes pratiques les plus efficaces (graines aplaties, farine), et peut atteindre jusqu’à 1,4% des AG du lait avec ce type de supplémentations. Il n’apparaît pas d’effet dose de lipides apportée pour le C18:2 n-6 et le C18:3 n-3, alors qu’il en existe un pour les C18:1-trans. Le beurre et les fromages ont la même composition en AG que le lait dont ils proviennent. Les qualités organoleptiques de beurres et fromages ne sont pas modifiées par l’addition de lin dans la ration. Différents effets sont cités dans la bibliographie pour expliquer une augmentation potentielle de la fertilité, qui reste à confirmer. La production ruminale de méthane est diminuée par l'ajout de lin dans la ration. En conclusion, l'ajout de lin à la ration des vaches laitières a des effets analogues à ceux d’introduction d’herbe dans le régime fourrager, à l’exception d’une teneur en AG trans supérieure., Supplementation of the dairy cow diet with linseed products is developing, aiming at increasing milk nutritional quality and decreasing methane output. Feedstuffs rich in polyunsatured fatty acids (FA) (especially linolenic acid) are used to complement diets poor in these FA, to produce a milk lower in saturated FA and with a lower linoleic/linolenic ratio. Linseed is indeed rich in linolenic acid. Greenhouse gas mitigation (including methane) is also a concern for the animal sector. Many studies involving linseed supplementation (with various processing treatments) have been published, and now enable to draw some conclusions about its effects. This article focuses on the supply of linseed and the various processing treatments. The effects of linseed on milk production, the composition of milk and dairy products, methane production and reproduction are reviewed. The results on milk production and composition are based on 41 published trials. Linseed cultivation is of little importance in France. Linseed in France is mainly supplied from European countries and Canada. Linseed varieties have different levels of linolenic acid. Dietary supplementation of cows with linseed slightly decreases dry matter intake, without significant effects on milk production. Milk saturated FA content is decreased and milk C18:1-trans are increased, especially with unprotected supplements (oil, extruded seeds). The C18:2 n-6 content is generally unchanged (except with oils) and starch-rich diets(for trans FA). The proportion of C18:3 n-3 is multiplied by 2 to 3 with the most effective treatments (seeds, flour), and can reach 1.4% of milk FA, with this type of supplement. The amount of lipid added does not significantly affect the milk content in C18:2 n-6 and C18:3 n-3, while it does for the C18: 1-trans. Butter and cheeses have the same FA composition as the milk used for their production. The organoleptic properties of butters and cheeses are not affected by linseed addition. Different effects are reported in the literature to explain a potential increase in fertility, which remains to be confirmed. Dietary linseed supplementation decreases the production of methane. In conclusion, dietary linseed supplementation of dairy cows has the same effects as those with the addition of grass in the diet, except for a higher content of trans FA.

This experiment was conducted to investigate the difference between ruminal (solid feed, SF) and abomasal (liquid feed, LF) feeding on the plasma leptin concentration in sheep. The experiment consisted of 2 weeks to adapt the animals to SF, 4 weeks of feeding on SF, 2 weeks adaptation to LF, 8 weeks of feeding on LF, 2 weeks of adaptation to SF, and 4 weeks of feeding on SF. The LF directory flowed into the abomasums of sheep by bottle feeding. Plasma leptin concentration before morning feeding was almost constant in the SF periods, whereas it showed between-day variations when measured during the LF periods. Mean plasma leptin levels were higher for LF (7.77 ± 0.76 ng/mL; mean ± SE) than for SF periods (3.95 ± 0.16 ng/mL; mean ± SE). Although plasma leptin concentration did not show any change after feeding in the SF and LF periods, plasma insulin and glucose levels increased within 15 min after liquid abomasal feeding, but not after solid ruminal feeding. The high plasma leptin concentration during the LF periods in weaned sheep could be due to change of digestible energy intake and changes in plasma insulin and glucose levels accompanying the changes in digestive processes and nutrient supply.

The potential benefits on human health have prompted an interest in developing nutritional strategies for specifically increasing rumenic acid (RA) in ruminant milk. The aims of the present study were to (i) compare two dietary treatments with lipid supplements on milk yield and composition, (ii) measure thein vivoΔ9-desaturation of vaccenic acid (VA) to RA using13C-labelled VA and (iii) determine the effect of the dietary treatments on this variable. Treatments were 90 g sunflower-seed oil (SO) per d or 60 g sunflower-seed oil and 30 g fish oil per d plus additional starch (SFO), in a grassland hay-based diet given to eight Alpine goats in a 2 × 2 cross-over design with 21 d experimental periods. Milk yield and composition were similar between treatments. Goats fed SFO had higher milk 6 : 0–16 : 0 concentration, lower milk ΣC18 concentrations and showed no effect on milk VA and RA, compared with SO. At the end of the experiment, intravenous injection of 1·5 g [13C]VA followed by measurements of milk lipid13C enrichment showed thatin vivo31·7 and 31·6 % of VA was Δ9-desaturated into milk RA in the caprine with the SO and SFO treatments, respectively. The expression of genes encoding for Δ9-desaturase (or stearoyl-CoA desaturase;SCD1,SCD5) in mammary tissues and four milk Δ9-desaturation ratios were similar between treatments. In conclusion, the present study provides the first estimates ofin vivoendogenous synthesis of RA (63–73 % of milk RA) from VA in goats, and shows no difference between the two lipid supplements compared.

National audience; Fat is an important constituent contributing to the organoleptic, processing and physical properties of ruminant milk. Understanding the regulation of milk fat synthesis is central to the development of nutritional strategies to enhance the nutritional value of milk, decrease milk energy secretion and improve the energy balance of lactating ruminants. Nutrition is the major environmental factor regulating the concentration and composition of fat in ruminant milk. Feeding low-fibre/high-starch diets and/or lipid supplements rich in polyunsaturated fatty acids induce milk fat depression (MFD) in the bovine, typically increase milk fat secretion in the caprine, whereas limited data in sheep suggest that the responses are more similar to the goat than the cow. Following the observation that reductions in milk fat synthesis during diet-induced MFD are associated with increases in the concentration of specific trans fatty acids in milk, the biohydrogenation theory of MFD was proposed, which attributes the causal mechanism to altered ruminal lipid metabolism leading to increased formation of specific biohydrogenation intermediates that exert anti-lipogenic effects. Trans-10, cis-12 conjugated linoleic acid (CLA) is the only biohydrogenation intermediate to have been infused at the abomasum over a range of experimental doses (1.25 to 14.0 g/day) and shown unequivocally to inhibit milk fat synthesis in ruminants. However, increases in ruminal trans-10, cis-12 CLA formation do not explain entirely diet-induced MFD, suggesting that other biohydrogenation intermediates and/or other mechanisms may also be involved. Experiments involving abomasal infusions (g/day) in lactating cows have provided evidence that cis-10, trans-12 CLA (1.2), trans-9, cis-11 CLA (5.0) and trans-10 18:1 (92.1) may also exert anti-lipogenic effects. Use of molecular-based approaches have demonstrated that mammary abundance of transcripts encoding for key lipogenic genes are reduced during MFD in the bovine, changes that are accompanied by decrease in sterol response element binding protein 1 (SREBP1) and alterations in the expression of genes related to the SREBP1 pathway. Recent studies indicate that transcription of one or more adipogenic genes is increased in subcutaneous adipose tissue in cows during acute or chronic MFD. Feeding diets of similar composition do not induce MFD or substantially alter mammary lipogenic gene expression in the goat. The available data suggests that variation in mammary fatty acid secretion and lipogenic responses to changes in diet composition between ruminants reflect inherent interspecies differences in ruminal lipid metabolism and mammary specific regulation of cellular processes and key lipogenic enzymes involved in the synthesis of milk fat triacylglycerides.

International audience; We conducted experiments to evaluate the effects of lipid supplementation and the nature of starchy concentrate on the regulation of leptin synthesis in lactating goats. Multiparous goats in mid- to late lactation received diets based on different forages and containing plant oil or seeds rich in either 18:1c9, 18:2n-6 or 18:3n-3 corresponding to 3%-7% dry matter (DM) as lipid supplements, or diets based on concentrate as either rapidly or slowly degradable starch. The isoenergetic replacement of a part of the concentrate by either oleic sunflower-seed oil, formaldehyde-treated linseeds, or linseed oil did not modify leptinemia and the leptin mRNA concentration in adipose tissues, suggesting a lack of effect of 18:1c9, 18:3n-3, or their biohydrogenation products. Conversely, leptinemia and the leptin mRNA abundance were increased (by 20% and 140%, respectively, P

International audience; Numerous experiments have studied the use of oilseed supplements in cow diets to alter milk fatty acid (FA) composition, but no quantitative synthesis of these studies is currently available. This article reports a meta-analysis of the response of cow milk FA composition to oilseed lipid supplements from linseed, rapeseed, soybeans, and sunflower seed. First, from a database of 145 oilseed supplementation experiments, we collected the mean FA percentages observed with unsupplemented diets and diets supplemented with the 4 oilseeds given as seeds (after various types of processing), as oils (including Ca salts and amides), or in protected forms. Second, we studied the response of the major milk FA percentages to increasing amounts of supplemental lipids from the 4 oilseeds. Responses were nonsignificant, linear, or quadratic, depending on the FA studied and the supplement. Effects of interfering factors, such as supplement form, forage component of the diet, or lactation stage, were difficult to assess from the available data. Third, we studied the response of the major milk FA percentages to increasing dietary intakes of linoleic or linolenic acids, taken separately. Overall, these results confirm the high plasticity of milk FA composition, with the widest variations being observed in the percentages of medium-chain versus C18 FA, and among the C18 in 18: 0, cis-18:1, and trans-18:1. The percentages of the polyunsaturated FA cis-9 cis-12-18:2 and 18:3 were less variable, except when protected lipids (mostly formaldehyde treated) were supplied. However, trans-18:1 and polyunsaturated FA (including conjugated linoleic acid) exhibited the greatest variations when expressed relative to their respective basal values (for unsupplemented diets). Oils, compared with seeds, induced greater percentages of trans-18: 1 and tended to decrease C6 to C12 FA more. Intakes of 18:2- and 18:3- rich lipid sources did not differ greatly in their effects on short- and medium-chain FA and trans-18:1 percentages, although the profiles of individual 18:1 and 18:2 isomers in milk differed. This meta-analysis provides quantitative estimates, obtained from the extensive literature produced over more than 40 yr, of the impact of oilseed supplements on milk FA composition.

This experiment studied the effect of 3 forms of presentation of linseed fatty acids (FA) on methane output using the sulfur hexafluoride tracer technique, total tract digestibility, and performance of dairy cows. Eight multiparous lactating Holstein cows (initial milk yield 23.4 +/- 2.2 kg/d) were assigned to 4 dietary treatments in a replicated 4 x 4 Latin square design: a control diet (C) consisting of corn silage (59%), grass hay (6%), and concentrate (35%) and the same diet with crude linseed (CLS), extruded linseed (ELS), or linseed oil (LSO) at the same FA level (5.7% of dietary DM). Each experimental period lasted 4 wk. All the forms of linseed FA significantly decreased daily CH(4) emissions (P 0.05) but was decreased with ELS and LSO (-3.1 and -5.1 kg/d, respectively; P < 0.001). Milk yield and milk fat content were similar for LSO and ELS but less than for C and CLS (19.9 vs. 22.3 kg/d and 33.8 vs. 43.2 g/kg, on average, respectively; P < 0.01 and P < 0.001). Linseed FA offer a promising dietary means to depress ruminal methanogenesis. The form of presentation of linseed FA greatly influences methane output from dairy cows. The negative effects of linseed on milk production will need to be overcome if it is to be considered as a methane mitigation agent. Optimal conditions for the utilization of linseed FA in ruminant diets need to be determined before recommending its use for the dairy industry.

The main objective of this study was to investigate the relationships between changes in plasma leptin concentration and feed intake or bodyweight in female and castrated male lambs with fattening. Four female and four castrated male lambs were used and were fed roughage and concentrate supplemented with beef tallow ad libitum for 28 weeks. Although the feed intake and bodyweight increased with fattening in both the castrated male and female lambs, they decreased at 24-28 weeks in the female lambs. At the end of fattening, the crude fat content in the muscle (loin) of the female lambs was significantly higher than in the castrated male lambs (P < 0.05), while the crude protein content in the loin and fillet meat was higher in the castrated male than in the female lambs (P < 0.05). The plasma leptin concentration showed high values at a later stage of fattening (P < 0.05). In the female lambs the plasma insulin concentration increased at a later stage of fattening (P < 0.05) and was positively correlated (P < 0.0001, r = 0.78) with plasma leptin. Plasma metabolites (glucose, nonesterified fatty acid, total cholesterol and triglyceride) concentrations were also changed with fattening. Plasma total cholesterol was positively related to plasma leptin, more closely in the female than in the castrated male lambs (in females, r = 0.63, P < 0.001; in males, r = 0.38, P < 0.01). The accumulation of body fat was probably accelerated by the consumption of a lot of concentrate feed supplemented with treated beef tallow and by the stimulation of insulin with fattening. Consequently, the plasma leptin concentration increased, especially toward the end of the fattening period. The decrease in feed intake and bodyweight after the 24th week of fattening was possibly caused by an increase in leptin that is involved in the homeostatic regulation of body energy by regulating appetite.

This work investigated the metabolic basis for the variability of carcass and i.m. adiposity in cattle. Our hypothesis was that the comparison of extreme breeds for adiposity might allow for the identification of some metabolic pathways determinant for carcass and i.m. adiposity. Thus, 23- to 28-mo-old steers of 3 breeds, 2 with high [Angus or Japanese Black x Angus (J. Black cross)] and 1 with low (Limousin) i.m. and carcass adiposity, were used to measure activities or mRNA levels, or both, of enzymes involved in de novo lipogenesis [acetyl-coA carboxylase, fatty acid synthase (FAS), glucose-6-phosphate dehydrogenase (G6PDH), malic enzyme], circulating triacylglycerol (TAG) uptake (lipoprotein lipase), and fatty acid esterification (glycerol-3-phosphate dehydrogenase), as well as the mRNA level of leptin, an adiposity-related factor. In a first study, enzyme activities were assayed in the s.c. adipose tissue (AT), the oxidative rectus abdominis, and the glycolytic semitendinosus muscles from steers finished for 6 mo. Compared with Angus or J. Black cross, Limousin steers had a 27% less (P = 0.003) rib fat thickness, and 23 and 29% less (P < or = 0.02) FAS and G6PDH activities in s.c. AT. In rectus abdominis and semitendinosus, the 75% less (P < 0.001) TAG content was concomitant with 50% less (P < 0.001) G6PDH activity. In a second study, enzyme activities plus mRNA levels were assayed in an oxido-glycolytic muscle, the longissimus thoracis (LT), in the i.m. AT dissected from LT, and in s.c. AT from the same Limousin steers and from Angus steers finished for 10 mo. Compared with Angus, the 50% less (P < 0.001) rib fat thickness in Limousin contrasted with the 1.1- to 5.8-fold greater (P < or = 0.02) mRNA levels or activities, or both, of acetyl-coA carboxylase, G6PDH, lipoprotein lipase, and glycerol-3-phosphate dehydrogenase in s.c. AT. Conversely, the 90% less (P < 0.001) TAG content in Limousin LT was concomitant to the 79 and 83% less (P < or = 0.002) G6PDH activity and leptin mRNA level. Such differences could arise from a greater number of adipocytes in LT from Angus steers because no difference was found between Limousin and Angus for G6PDH activity and leptin mRNA in i.m. AT. We conclude that FAS and G6PDH in s.c. AT could be involved in differences in carcass adiposity, but this relationship disappeared when the fatness increased strongly. Leptin and G6PDH are related to the expression of marbling whatever the body condition and thus could be relevant indicators of marbling in beef cattle.

This study reports a quantitative analysis of two experiments comparing the effects of different dietary forage/concentrate ratios and lipid supplements on cow lipid digestion and milk fatty acid (FA) secretion. We studied, on an individual cow basis, the relationship between digestive variables [fiber intake and duodenal 18-carbon (C 18 ) FA flows], plasma FA content, milk FA yield and composition. Milk short- and medium-chain FA (C 4 -C 16 ) secretion depended mainly on additive effects of dietary fiber intake and lipid supplementation level. For high-lipid diets (3-5% oil in dry matter intake), milk C 18 secretion was proportional to C 4 -C 16 secretion, independently of C 18 dietary supply. For the low-forage high-lipid diet, C 4 -C 16 secretion apparently limited C 18 secretion, which represented only 36% of absorbed C 18 , compared to 79% with a high-forage high-lipid diet (higher C 4 -C 16 secretion). Despite these high variations in total C 18 secretion, the composition of milk C 18 was not significantly different, within cows, from the duodenal C 18 composition, when substrates and products of A-9 desaturase were summed. Mammary desaturation activity (expressed in mol/day) was a linear function of the estimated mammary uptake of the substrates, and this endogenous production represented more than 75% of the milk secretion of the A-9 desaturated products.

The potential to modify the milk fatty acid (FA) composition by changing the cow or goat diets is reviewed. Ruminal biohydrogenation (RBH), combined with mammary lipogenic and A-9 desaturation pathways, considerably modifies the profile of dietary FA and thus milk composition. The pasture has major effects by decreasing saturated FA and increasing FA considered as favorable for human health (c9-18:1, 18:3n-3 and c9t11-CLA), compared to winter diets, especially those based on maize silage and concentrates. Plant lipid supplements have effects similar to pasture, especially linseed, but they increase to a larger extent, simultaneously several trans isomers of 18:1 and, conjugated or non-conjugated 18:2, especially when added to maize silage or concentrate-rich diets. The goat responds better for milk 18:3n-3 and c9t11-CLA, and sometimes less for c9-18:1, and is less prone to the RBH trans-11 to trans-10 shift, which has been shown to be time dependent in the cow. The respective physiological roles of most milk trans FA have not been studied to date, and more studies in rodents and humans fed dairy products modified by changing ruminant diet are required before recommending a larger use of lipid sources and how to combine them with the different feeding systems used by dairy farmers.

Animal nutrition considerably affects milk composition that influences its nutritional quality. Milk component synthesis and secretion by the mammary gland involve expression of a large number of genes whose nutritional regulation remains poorly defined. In this study, we examined the effect of food deprivation (FD) on the expression of 8379 genes in caprine mammary gland using a bovine oligonucleotide microarray. Twelve lactating goats were assigned to 2 groups based on their feeding level (control diet ad libitum vs. 48-h FD). We identified 161 genes whose expression was altered by FD. Most of these genes (88%) were downregulated, suggesting a stress response by the mammary gland. In particular, the decrease in expression of genes involved in milk protein, lactose, and lipid metabolism could contribute together with the shortage of nutrients to the drop in milk protein, lactose, and fat secretion. In addition, this study highlights modification of the expression of at least 14 genes that could be responsible for a slowdown in mammary cell proliferation and differentiation and/or an increase in programmed cell death in response to 48-h FD in goats.

It is well known that any quantitative (energy and protein levels) and qualitative (nature of the diet, nutrient dynamic) changes in the feeding of animals affect metabolism. Energy expenditure and feed efficiency at the whole-body level, nutrient partitioning between and within tissues and organs and, ultimately, tissue and organ characteristics are the major regulated traits with consequences on the quality of the meat and milk produced. Recent progress in biology has brought to light important biological mechanisms which explain these observations: for instance, regulation by the nutrients of gene expression or of key metabolic enzyme activity, interaction and sometimes cross-regulation or competition between nutrients to provide free energy (ATP) to living cells, indirect action of nutrients through a complex hormonal action, and, particularly in herbivores, interactions between trans-fatty acids produced in the rumen and tissue metabolism. One of the main targets of this nutritional regulation is a modification of tissue insulin sensitivity and hence of insulin action. In addition, the nutritional control of mitochondrial activity (and hence of nutrient catabolism) is another major mechanism by which nutrients may affect body composition and tissue characteristics. These regulations are of great importance in the most metabolically active tissues (the digestive tract and the liver) and may have undesirable (i.e. diabetes and obesity in humans) or desirable consequences (such as the production of fatty liver by ducks and geese, and the production of fatty and hence tasty meat or milk with an adapted fatty acid profile).

21 páginas, 8 tablas, 2 figuras, A study with 2 ruminant species (goats and cows) with inherent differences in lipid metabolism was performed to test the hypothesis that milk fat depression (MFD) due to marine lipid supplements or diets containing high amounts of starch and plant oil is caused by different mechanisms and that each ruminant species responds differently. Cows and goats were allocated to 1 of 3 groups (4 cows and 5 goats per group) and fed diets containing no additional oil (control) or supplemented with fish oil (FO) or sunflower oil and wheat starch (SOS) according to a 3 x 3 Latin square design with 26-d experimental periods. In cows, milk fat content was lowered by FO and SOS (-31%), whereas only FO decreased milk fat content in goats (-21%) compared with the control. Furthermore, FO and SOS decreased milk fat yield in cows, but not in goats. In both species, FO and SOS decreased the secretion of C16 FA output. However, SOS increased milk secretion of >C16 FA in goats. Compared with the control, SOS resulted in similar increases in milk trans-10, cis-12 conjugated linoleic acid (CLA) in both species, but caused a 2-fold larger increase in trans-10 18:1 concentration in cows than for goats. Relative to the control, responses to FO in both species were characterized by a marked decrease in milk concentration of 18:0 (-74%) and cis-9 18:1 (-62%), together with a similar to 5-fold increase in total trans 18:1, but the proportionate changes in trans-10 18:1 were lower for goats. Direct comparison of animal performance and milk FA responses to FO and SOS treatments demonstrated interspecies differences in mammary lipogenesis, suggesting a lower sensitivity to the inhibitory effects of trans-10, cis-12 CLA in goats and that ruminal biohydrogenation pathways are more stable and less prone to diet-induced shifts toward the formation of trans-10-containing intermediates in goats compared with cows. Even though a direct cause and effect could not be established, results suggest that regulation of milk fat synthesis during FO-induced MFD may be related to a shortage of 18:0 for endogenous mammary cis-9 18:1 synthesis, increase in the incorporation of trans FA in milk triacylglycerols, and limitations in the synthesis of FA de novo to maintain milk fat melting point. However, the possible contribution of biohydrogenation intermediates with putative antilipogenic effects in the mammary gland, including trans-9,cis-11 CLA, trans-10 18:1, or cis-11 18:1 to FO-induced MFD cannot be excluded., P. G. Toral was granted a post-doctoral fellowship from Fundacion Alfonso Martin Escudero (Madrid, Spain). The authors gratefully acknowledge the staff of Unite Experimentale des Ruminants de Theix (INRA, Saint-Genes-Champanelle, France) for the diligent care of the experimental animals, and D. Bany, C. Delavaud, E. Tixier, and M. Tourret from UMR 1213 Herbivores (INRA) for assistance in sampling collection and laboratory analysis. The contribution of Laura Ventto and Minna Aalto (Natural Resources Institute Finland, Jokioinen, Finland, formerly MTT Agrifood Research Finland) to the analysis of milk fat composition is acknowledged and appreciated.

International audience; The aims of this work were to elucidate the potential of using milk fatty acid (FA) concentration to predict cow diet composition and altitude of bulk milk collected in 10 different European countries and to authenticate cow-feeding systems and altitude of the production area using a data set of 1,248 bulk cow milk samples and associated farm records. The predictions based on FA for cow diet composition were excellent for the proportions of fresh herbage [coefficient of determination (R-2) = 0.81], good for hay, total herbage-derived forages, and total preserved forages (R-2 > 0.73), intermediate for corn silage and grass silage (R-2 > 0.62), and poor for concentrates (R-2 < 0.51) in the cow diet. Milk samples were assigned to groups according to feeding system, level of concentrate supplementation, and altitude origin. Milk FA composition successfully authenticated cow-feeding systems dominated by a main forage (>93% of samples correctly classified), but the presence of mixed diets reduced the discrimination. Altitude prediction reliability was intermediate (R-2

Published online: 02 December 2014.--10 páginas, 7 tablas., There are very few studies in ruminants characterizing mammary and adipose tissue (AT) expression of genes and gene networks for diets causing variations in milk fatty acid (FA) composition without altering milk fat secretion, and even less complementing this information with data on tissue FA profiles. This work was conducted in sheep to investigate the response of the mammary gland and the subcutaneous and perirenal AT, in terms of FA profile and mRNA abundance of genes involved in lipid metabolism, to a diet known to modify milk FA composition. Ten lactating Assaf ewes were randomly assigned to 2 treatments consisting of a total mixed ration based on alfalfa hay and a concentrate (60:40) supplemented with 0 (control diet) or 25 (SO diet) g of sunflower oil/kg of diet DM for 7 weeks. Milk composition, including FA profile, was analysed after 48 days on treatments. On day 49, the animals were euthanized and tissue samples were collected to analyse FA and mRNA abundance of 16 candidate genes. Feeding SO did not affect animal performance but modified milk FA composition. Major changes included decreases in the concentration of FA derived from de novo synthesis (e.g., 12:0, 14:0 and 16:0) and increases in that of long chain FA (e.g., 18:0, c9-18:1, trans-18:1 isomers and c9,t11-CLA) but they were not accompanied by significant variations in the mRNA abundance of studied lipogenic genes (i.e., ACACA, FASN, LPL, CD36, FABP3, SCD1 and SCD5) and transcription factors (SREBF1 and PPARG), or in the constituent FA of mammary tissue. Regarding the FA composition of AT, the little influence of SO did not appear to be linked to changes in gene mRNA abundance (decreases of GPAM and SREBF1 in both tissues, and of PPARG in the subcutaneous depot). Similarly, the great variation between AT (higher contents of saturated FA and trans-18:1 isomers in the perirenal, and of cis-18:1, c9,t11-CLA and n-3 PUFA in the subcutaneous AT) could not be related to differences in gene mRNA abundance due to tissue site (higher LPL and CD36, and lower SREBF1 in perirenal than in subcutaneous AT). Overall, these results suggest a marginal contribution of gene expression to the nutritional regulation of lipid metabolism in these tissues, at least with the examined diets and after 7 weeks on treatments. It cannot be ruled out, however, that the response to SO is mediated by other genes or post-transcriptional mechanisms., This study was supported by the Spanish Ministry of Economy and Competitiveness (AGL2011-23700), the Council of Castile and Leon (CSI023U13), and the INRA (UMR1213; France). T. Castro-Carrera was granted a predoctoral fellowship from the Spanish National Research Council (CSIC; JAE Programme) supported by European Social Fund.

International audience; The effects of conjugated linoleic acid isomers (CLA) and endurance training on lean body mass are expected to result from their action on tissue protein metabolism. The aim of this study was to analyze their effects on protein metabolism in 2 muscles, the small intestine and liver of adult rats. Four-month-old male Wistar rats were fed diets containing either no CLA, cis-9, trans-11 CLA isomer (1 g.100 g$^{-1})$, trans-10, cis-12 CLA isomer (1 g.100 g$^{-1})$ or both isomers (1 g.100 g$^{-1}$ each) for 6 weeks. Half of the rats were subjected to endurance training by running on a treadmill. At the end of this period, the rats were injected with a flooding dose of $^{13}$C-valine to determine protein synthesis rates in the post-absorptive (experiment 1) and in the post-prandial (experiment 2) states. No effect of CLA or endurance training were detected in the small intestine. Training reduced food intake and protein synthesis rates in the liver but no effect was found on the protein synthesis rates in muscles. In the post-absorptive state, protein synthesis rate was increased by feeding the trans-10, cis-12 CLA isomer alone in the liver (+9%) or in combination with the cis-9, trans-11 isomer in the gastrocnemius (+30%), mostly in sedentary rats. In the post-prandial state, the cis-9, trans-11 CLA isomer tended to reduce the protein synthesis rate in the gastrocnemius muscle. However, no effect of CLA was found on muscle protein amounts. In conclusion, CLA isomers would have limited but differential effects on tissue protein metabolism in adult rats.

It is well established that plant oils reduce milk saturated fatty acid content and enhance concentrations of conjugated linoleic acid (CLA) and trans C18:1in milk fat, but there is increasing evidence to suggest that milk fat CLA responses are often transient and decline over time. It is probable that time dependent adaptations in ruminal biohydrogenation and changes in milk fatty acid composition to lipid supplements are, at least in part, related to the composition of the basal diet. To test this hypothesis, 18 Holstein cows were used in a continuous randomized block design to examine changes in milk fatty acid composition over time in response to plant oils included in diets of variable composition. Cows were randomly allocated to one of three basal diets containing (g/kg dry matter (DM)) maize silage (267) and concentrates (733) (diet C); maize silage (332), grass hay (148) and concentrates (520) (diet M), or grass hay (642) and concentrates (358) (diet H). Basal rations were offered for 21 days, after which diets were supplemented with 50 g sunflower per kg DM (diets C-S and M-S) or 50 g linseed oil per kg DM (diet H-L). Oils were included in all rations incrementally over a five day period (days 0–4), and responses to 50 g/kg DM of the respective oils were evaluated for 17 days (days 4 to 20). Milk fatty acid composition was intensively monitored from days −2 to 20. In contrast to the H-L diet, both C-S and M-S treatments decreased (PPcis-9,trans-11 CLA andtrans-11 C18:1contents were enhanced on the C-S and M-S treatments but the increases were transient reaching the highest concentrations between days 4 and 6 (cis-9,trans-11 CLA: 1·94 and 2·18 g per 100 g total fatty acids;trans-11 C18:1: 4·88 and 6·23 g per 100 g total fatty acids, respectively) but declined thereafter. In marked contrast, concentrations ofcis-9,trans-11 CLA andtrans-11 C18:1in milk from the H-L diet increased gradually over time, responses that were maintained until the end of the experiment (2·89 and 7·49 g per 100 g total fatty acids, respectively).Decreases in milk fatcis-9,trans-11 CLA andtrans-11 C18:1after day 6 on the M-S and C-S diets were associated with concomitant increases in milk fattrans-10 C18:1content reaching 7·22 and 18·62 g per 100 g total fatty acids on day 18, respectively, whereas concentrations oftrans-10 C18:1in milk on the H-L diet remained low throughout the experiment (0·70 g per 100 g total fatty acids on day 18). Furthermore, milk fattrans-11,cis-13 CLA,trans-11,trans-13 CLA andtrans-12,trans-14 CLA contents were all enhanced on the H-L diet, while the M-S and C-S diets increasedtrans-8,cis-10 CLA,trans-10,cis-12 CLA andtrans-9,cis-11 CLA concentrations. Across all diets, decreases in milk fat content were associated with increases in milktrans-10 C18:1,trans-10,cis-12 andtrans-9,cis-11 CLA concentrations (r2=0·93, 0·88 and 0·89, respectively). In conclusion, the relative abundance oftransC18:1and CLA isomers in milk fat were dependent on the composition of the basal diet, type of plant oil and duration of lipid supplementation, highlighting the challenges in developing nutritional strategies for the production of milk highly enriched with CLA over an extended period of time.

International audience; Ketosis was diagnosed in a flock of Merino ewes that conceived from synchronised oestrus in the early autumn period. On day 140 of pregnancy the ewes were sampled for determination of beta OH-butyrate ( BHB), AST, glucose, nonesterified fatty acids ( NEFA), total cholesterol ( TCH), insulin, T-4, T-3, cortisol, IGF-1 and leptin. The results were evaluated according to the number of fetuses born some days later and the presence of hyperketonaemia ( BHB: >= 1.60 mmol/l). In May, about 3 months after lambing, cyclic ovarian function was induced ( Cronolone + eCG), and the ewes were inseminated artificially ( AI) 48 h after the removal of gestagen-containing sponge. At the time of AI and 10 days later blood samples were collected again to check the plasma levels of the same constituents as previously ( in samples taken at AI), and to monitor the ovarian response by assaying progesterone ( in both samples). On day 140 of gestation significantly lower BHB levels were detected in dams with single ( n = 41) than in those with twin ( n = 57) pregnancies. Hyperketonaemia was found only in ewes bearing twins ( n = 27). These animals had higher NEFA and cortisol, and lower TCH, insulin, IGF-1, leptin and T3 levels than their normoketonaemic twin-bearing flockmates, and those with single pregnancy. The blood glucose concentrations varied within a wide range, and the means of groups did not exhibit any significant differences. The formerly hyperketonaemic individuals were characterised by lower leptin level 3 months after lambing, and they showed a poorer response to the cycle-induction procedure than the others. The non-responders had lower IGF-1 and leptin levels than those ovulated after this treatment. It was concluded that the subclinical form of ovine ketosis is characterised by complex endocrine alterations, reflecting an obvious form of negative energy balance. If attempts to induce cyclic ovarian function outside the breeding season are made soon after lambing, the ovarian response and fertility of these ewes may also be depressed.

Three Holstein cows were fed a high-concentrate diet (65:35 concentrate to forage) supplemented with either 5% sunflower oil (SO), 5% linseed oil (LO), or 2.5% fish oil (FO) to examine effects on biohydrogenation and fatty acid profiles in rumen, blood plasma, and milk. Diets were fed in a 3×3 Latin square with 4-wk periods with grass hay as the forage. Milk yield, dry matter intake, and percentages of milk fat (2.64) and protein (3.22) did not differ. All diets resulted in incomplete hydrogenation of unsaturated fatty acids as indicated by the profiles of 18:1 isomers, conjugated 18:2 isomers, nonconjugated 18:2 isomers, and 18:0 in ruminal fluid. Percentages of 8:0–14:0 and 16:0 in milk fat were greater with FO. Percentage and yield of trans 10, cis 12-18:2 were small and greater in cows fed SO (0.14%, 0.57 g/d) than FO (0.03%, 0.15 g/d) or LO (0.04%, 0.12 g/d). Percentage and yield of trans 10-18:1, however, increased with FO (6.16%) and SO (6.47%) compared with LO (1.65%). Dietary FO doubled percentage of cis 11-18:1 in rumen, plasma, and milk fat. Despite a lack of difference in ruminal percentage of trans 11-18:1 (10.5%), cows fed FO had greater plasma trans 11-18:1 (116 vs. 61.5μg/mL) but this response did not result in greater trans 11-18:1 percentage in milk fat, which averaged 5.41% across diets. Percentage (2.2%) and yield (14.3 g/d) of cis 9, trans 11-18:2 in milk fat did not differ due to oils. Unique responses to feeding LO included greater than 2-fold increases in percentages of trans 13+14-18:1, trans 15-18:1, trans 16-18:1, cis 15-18:1, cis 9, trans 12-18:2 and trans 11, cis 15 -18:2 in umen, plasma, and milk, and cis 9, trans 13-18:2 in plasma and milk. Ruminal 18:0 percentage had the highest positive correlation with milk fat content (r = 0.82) across all diets. When compared with previous data with cows fed high-concentrate diets without oil supplementation, results suggest that greater production of trans 10-18:1, cis 11-18:1, and trans 11, cis 15-18:2 coupled with low production of 18:0 in the rumen may be associated with low milk fat content when feeding high-concentrate diets and fish oil. In contrast, SO or LO could lead to low milk fat content by increasing ruminal trans 10-18:1 (SO) or trans 11, cis 15-18:2 and trans 9, trans 12-18:2 (LO) along with a reduction in mammary synthesis of 8:0-16:0. Simultaneous increases in ruminal trans 11-18:1 with fish oil, at a fraction of sunflower oil supplementation, may represent an effective strategy to maintain cis 9, trans 11-18:2 synthesis in mammary while reducing milk fat output and sparing energy.

International audience; Milk fat secretion and profiles of conjugated linoleic acids (CLA) and trans-18:1 isomers in milk fat due to a ruminal or duodenal supply of fish oil (FO; EPA = 22% of total fatty acids, DHA = 7%) were evaluated using six lactating Holstein cows with cannulas in their rumen and duodenum. Cows were fed a control diet based on corn silage (66% of DM), or the control plus 300 mL FO/d into the rumen (FO-R) or duodenum (FO-D) for 4 weeks in a replicated 3 x 3 Latin square design. Dry matter intake was higher with the control (19.8 kg/d), intermediate with FO-D (18.0 kg/d), and lower with FO-R (16.2 kg/d). Yield of milk (22.7 kg/d), lactose (1.09 kg/d), or crude protein (0.70 kg/d) was not affected by treatments. Content of crude protein, true protein, and casein was lower in response to FO-R compared with the control. Despite similar jugular concentration compared with the control, jugular-mammary venous difference for beta-OH-butyrate was 54% lower with FO-R or FO-D. Milk fat content and yield were lowest with FO-R (25 g/kg, 567 g/d) compared with FO-D (32 g/kg, 737 g/d) or the control (35 g/kg, 783 g/d). Percentage of trans5-, trans6+7+8-, trans9-, trans 10-, trans11-,transl2-, and trans13+14-18:1 in milk fat was greater due to FO-R (0.05, 0.44, 0.48, 1.8, 9.2, 0.70, and 0.82%, respectively) compared with the control or FO-D (0.02, 0.22, 0.19, 0.27, 1.1, 0.35, and 0.40%). Although 18:0 and cis9-18:1 percentage was markedly lower in response to FO-R, percentage of cis11-, cis13-, and cis15-18:1 was greater compared with the control or FO-D. Cis9,trans11-CLA (87-95% of total CLA) averaged 3.2% in response to FO-R compared with 0.51% for control or FO-D. Trans10,cis12-18:2 was not detected. Among non-conjugated 18:2 isomers, cis9,cis12-18:2 was lower but cis9,trans13-, trans9,cis12-, and trans11,cis15-18:2 greater when FO-R was compared with the control or FO-D. There was high correlation (r = 0.94-0.99) among data obtained by GLC versus HPLC for most trans-18:1 isomers and cis9,trans11-18:2, suggesting GLC alone with our chromatographic conditions provided adequate separation of isomers. Milk 20:5n-3 (EPA) and 22:6n-3 (DHA) were 0.08 and 0.04% with the control, increased to 0.36 and 0.17% with FO-R, and were 1.47 and 0.47% with FO-D. Data indicate, ruminal supply of FO led to hydrogenation of EPA and DHA and enhanced percentage of various trans-18: 1, cis-18:1, non-conjugated 18:2, and cis9,trans11-18:2 in milk fat. Combined increases in trans-18:1 along with reduced availability of 18:0 for endogenous synthesis of cis9-18:1 may play a key role in reduced milk fat synthesis in cows fed fish oil.

Leptin concentrations in body fluids and tissues undergo dynamic changes during the periparturient period. Polymorphisms in the leptin gene have been shown to be associated with differences in leptin concentration during late pregnancy but not during lactation. As the promoter of leptin regulates the expression of leptin, polymorphisms in this region could play an important role in the differences in leptin expression observed during the periparturient period. We sequenced the leptin promoter and discovered 20 SNP in a 1.6-kbp region of the bovine leptin promoter. Fourteen of these SNP were genotyped for all animals and these were found to be associated with leptin concentrations during late pregnancy but not during lactation. Three of these SNP are located in a 135-bp promoter region and together explained 14.3% of the variance in prepartum leptin concentrations which indicates that this region might be important for pregnancy-induced leptin synthesis. In the association study of the 14 SNP with dairy traits three were separately found to be associated with fertility, energy balance and protein yield. These might serve as markers for future breeding programmes for better fertility and energy balance without significantly influencing milk yield in dairy cattle.

International audience; Most dairy ruminants are still lactating during early pregnancy, which could induce hormonal adaptations different from those observed during pregnancy alone. The incidence of concomitant lactation and pregnancy on plasma leptin has not been studied, and physiological factors involved in its regulation have not been addressed in goats. We assayed leptinemia throughout the pregnancy-lactation cycle in nulliparous and primiparous goats, starting 165 days prior to parturition and finishing 59 days after. During the first half of pregnancy, primiparous goats were lactating. Lactating non-pregnant primiparous goats were studied in parallel. Plasma leptin increased (+49%) up to mid-pregnancy in nulliparous, but not in primiparous goats. Furthermore, leptinemia was similar between pregnant and non-pregnant lactating primiparous goats, suggesting a strong leptinemia down-regulation by late lactation. Plasma leptin decreased from mid-pregnancy to parturition, more markedly in nulliparous goats, and remained depressed during early lactation at a similar level in both female types. It was lower, at 130 days of pregnancy, in goats carrying two fetuses. The leptinemia down-regulation by late pregnancy was highlighted by the lack of plasma leptin increase after drying-off late-pregnant primiparous goats, while it strongly increased in non-pregnant goats. The observation of leptinemia increase only in nulliparous goats suggests that it is not an essential endocrine adaptation during early pregnancy. By contrast, in both female types, the low leptinemia during transition from late pregnancy to lactation, and during late lactation, may be important for the adaptations that occur during lactation such as the partitioning of energy and nutrients towards essential functions and/or hyperphagia.

Effects on fatty acid profiles and milk fat yield due to dietary concentrate and supplemental 18:3n-3 were evaluated in 4 lactating Holstein cows fed a low- (35:65 concentrate:forage; L) or high- (65:35; H) concentrate diet without (LC, HC) added oil or with linseed oil (LCO, HCO) at 3% of DM. A 4 x 4 Latin square with four 4-wk periods was used. Milk yield and dry matter intake averaged 26.7 and 20.2 kg/d, respectively, across treatments. Plasma acetate and beta-hydroxybutyrate decreased, whereas glucose, nonesterified fatty acids, and leptin increased with high-concentrate diets. Milk fat percentage was lower in cows fed high-concentrate diets (2.31 vs. 3.38), resulting in decreases in yield of 11 (HC) and 42% (HCO). Reduced yields of 8:0-16:0 and cis9-18:1 fatty acids accounted for 69 and 17%, respectively, of the decrease in milk fat yield with HC vs. LC (-90 g/d), and for 26 and 33%, respectively, of the decrease with HCO vs. LCO (-400 g/d). Total trans-18:1 yield increased by 25 (HCO) and 59 (LCO) g/d with oil addition. Trans10-18:1 yield was 5-fold greater with high-concentrate diets. Trans11-18:1 increased by 13 (HCO) and 19 (LCO) g/d with oil addition. Trans13+14-18:1 yield increased by 9 (HCO) and 18 (LCO) g/d with linseed oil. Yield of total conjugated linoleic acids (CLA) in milk averaged 6 g/d with LC or HC compared with 14 g/d with LCO or HCO. Cis9,trans11-CLA yield was not affected by concentrate level but increased by 147% in response to oil. Feeding oil increased yields of trans11,cis13-, trans11,trans13-, and trans,trans-CLA, primarily with LCO. Trans10,cis12-CLA yield (average of 0.08 g/d) was not affected by treatments. Yield of trans11,cis15-18:2 was 1 g/d in cows fed LC or HC and 10 g/d with LCO or HCO. Yields of cis9,trans11-18:2, cis9,trans12-18:2, and cis9,trans13-18:2 were positively correlated (r = 0.74 to 0.94) with yields of trans11-18:1, trans12-18:1, and trans13+14-18:1, respectively. Plasma concentrations of biohydrogenation intermediates with concentrate or linseed oil level followed similar changes as those in milk fat. Milk fat depression was observed when HC induced an increase in trans10-18:1 yield. A correlation of 0.84 across 31 comparisons from 13 published studies, including the present one, was found among the increase in percentage of trans10-18:1 in milk fat and decreased milk fat yield. We observed, however, more drastic milk fat depression when HCO increased yields of total trans-18:1, trans11,cis15-18:2, trans isomers of 18:3, and reduced yields of 18:0 plus cis9-18:1.

International audience; Once-a-day milking of multiparous Holstein cows throughout the entire lactation: milk yield and composition, and nutritional status. Eighteen multiparous Holstein cows were distributed into two similar groups immediately after calving: the control group (M2) was milked twice a day throughout lactation whereas the other group (M1) was milked only once a day in the morning. During the indoor (winter) period, all animals received the same total mixed ration ad libitum. In the summer, they were turned to pasture at the same time. The seven cows of group M2 (2 cows were excluded) produced 7323 kg of milk on average in 305 days. The nine cows of group M1 produced 5114 kg of milk (-30%; P < 0.01) over an entire lactation that lasted 12 days less than the twice daily milked cows. Fat and protein concentrations were higher by 3.5 g*kg-1 (P < 0.01) and 2.1 g*kg-1 (P = 0.06), respectively, in the M1 group. Mean lactose contents (entire lactation) did not differ between groups (P > 0.10). Mean somatic cell count (log10 = 5.043 per mL and 4.946 per mL in groups M1 and M2, respectively) did not differ between the groups despite the sharp increase noted in group M1 during the last third of lactation. Casein and whey protein contents also were not significantly different between the groups. Plasmin and lipoprotein lipase activities were unchanged although the plasminogen-derived activity tended to be higher in the milk from group M1. The dry matter (feed) mean intake amount of the first 14 weeks of lactation did not differ between the two groups although it gradually became higher in the M2 group. Group M1 cows' liveweight and body condition gradually improved over those of group M2, with a difference as high as 56 kg (P < 0.01) and 0.94 point on the body condition score (P = 0.02) on the 36th week of lactation. Eight of the nine M1 cows and four of the seven M2 cows were diagnosed as pregnant. The M1 cows did not show any specific sanitary disorder or abnormal behaviour throughout the lactation.; La traite une fois par jour de vaches laitières multipares Prim'holstein pendant toute la lactation : production laitière et état nutritionnel. Dix-huit vaches Prim'Holstein multipares ont été réparties en deux lots semblables dès le vêlage : le lot témoin (2M) a été trait deux fois par jour durant toute la lactation, tandis que l'autre lot (1M) n'était trait que le matin. Au cours de la période de stabulation les animaux ont reçu, à volonté, la même ration complète. Pendant l'été, ils ont été conduits ensemble au pâturage. Les 7 vaches du lot 2M (2 vaches éliminées) ont produit en moyenne 7323 kg de lait en 305 jours. Les 9 vaches du lot 1M ont produit 5114 kg (-30 % ; P < 0,01) au cours d'une lactation plus courte de 12 jours en moyenne. Les teneurs en matières grasses et en protéines ont été plus élevées de, respectivement, 3,5 g*kg-1 (P < 0,01) et 2,1 g*kg-1 (P = 0,06) dans le lot 1M. Les teneurs moyennes (sur la lactation) du lait en lactose n'ont pas été différentes entre les 2 lots (P > 0,10). Il en est de même des concentrations des cellules somatiques (log10 = 5,043 par mL et 4,946 par mL pour les lots 1M et 2M), malgré la forte augmentation observée dans le lot 1M au cours du dernier tiers de la lactation. La concentration des caséines et des protéines solubles n'a pas été significativement différente entre les lots. Les activités de la plasmine et de la lipoprotéine lipase n'ont pas été modifiées, mais l'activité dérivée du plasminogène a eu tendance à être plus élevée dans le lait du lot 1M. La quantité de matière sèche ingérée au cours des 14 premières semaines de lactation n'a pas été, en moyenne, différente entre les 2 lots, mais elle est progressivement devenue plus élevée dans le lot 2M. Le poids vif des vaches du lot 1M et leur état corporel sont progressivement devenus plus élevés que ceux du lot 2M, la différence atteignant 56 kg à la 36e semaine de lactation (P < 0,01) et 0,94 point de note d'état corporel (P = 0,02). Huit des neuf vaches du lot 1M et quatre des sept vaches du lot 2M ont été diagnostiquées fécondées. Les vaches du lot 1M n'ont présenté aucun trouble sanitaire particulier et aucun comportement anormal.

The in vitro effects of insulin and/or dexamethasone (DEX) on leptin production were studied on adipose tissue (AT) from adult non-lactating, non-pregnant ewes. Perirenal AT explants were incubated for 2 or 4 days and leptin production was determined using a specific ovine RIA. The effects of these hormones were simultaneously measured on glucose and acetate utilisation and on lipogenic enzyme activities. A preliminary dose-response study showed a maximal leptin produc- tion by the addition in the incubation medium of 2 mIU·mL -1 of insulin and 100 nM of DEX. By us- ing these concentrations, insulin or DEX increased leptin production by ovine AT explants whatever the incubation duration and the effects of these two hormones were additive. Insulin also increased substrate utilisation as well as lipogenic enzyme activities while DEX decreased substrate utilisation and did not change the lipogenic enzyme activities. To conclude, leptin response to DEX is specific and largely independent of the overall metabolic or lipogenic activity. ewe / adipose tissue / leptin / insulin / dexamethasone

We examined the ability of the ovine mammary gland to synthesize leptin throughout pregnancy and lactation. Leptin gene expression was assayed by real-time reverse transcription and polymerase chain reaction in mammary gland from ewes at 15, 80, 106, 112, or 141 d of pregnancy and at 0 (30 min after parturition), 3, 48, or 70 d of lactation. Leptin mRNA level was high at the beginning (the first 80 d) and at the end of pregnancy and was lower at mid-pregnancy and throughout lactation. Furthermore, during these periods of mammary leptin expression, the location of leptin protein, as determined by immunohistochemical analysis, changed within mammary tissue. It was located in adipose cells during early stages of pregnancy, in epithelial cells after full cell differentiation just before parturition, and in myoepithelial cells after parturition. These data, compared with published data on leptin receptor gene expression, provide evidence that leptin could be produced by different cell types of the mammary gland and could act as a paracrine factor on mammary cell growth and differentiation via adipose-epithelial cells and myoepithelial-epithelial cell interactions.

This review summarises the effects of nutritional factors on fat content, different isomers of trans18:1 and conjugated linoleic acids (CLA) in milk fat from dairy cows and goats. Main dietary factors taken into account are the nature of for- ages and pasture, and supplementation with oil seeds, vegetable or marine oils. The effects of interactions between the nature of forages and lipid supplements in cows or goats are reviewed with particular attention. Lipid supplements could highly increase mean trans-vaccenic acid (TVA) and cis-9, trans-11 CLA content in ruminant milk fat, and interact with the quantity of concentrate in the diet or the type of preserved forage. Vegetable or fish oil supplementation increased milk cis-9, trans-11 CLA up to 4% (in total milk fatty acids (FA)). The content of copper or vitamin E in the diet could modify the milk percentage of TVA and cis-9, trans-11 CLA. Other isomers of trans-18:1 (e.g. trans-10) and CLA (e. g. cis-11, trans-13 or trans-11, trans-13 or trans-7, cis-9 or cis-9, cis-11 CLA) may be manipulated by diet composition. However, further studies are needed to establish their responses to different feeding strategies. The trans-10, cis-12 CLA in percentage in milk fat was always lower than 0.15% of total FA. The proportions of different trans-18:1 isomers in milk fat are similar in caprine and bovine species. Recent studies showed that the CLA content of goat milk fat was sim- ilar to values (0.4 - 0.9% and up to 4% for winter and lipid-supplemented diets, respectively) observed in the cow.&nbsp