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This study was conducted in lactating goats with the aim of measuring the deposition of trans-11 18:1 (vaccenic acid, VA) and the product of its Δ9-desaturation, cis-9, trans-11 18:2 (rumenic acid, RA), in the major tissues that are involved in lipid metabolism in the lactating ruminant (i.e., mammary secretory tissue, liver, and omental and perirenal adipose tissues) and examining its potential link with variations in the expression of genes encoding Δ9-desaturase [stearoyl-CoA desaturases 1 and 5 (SCD1 and SCD5)]. Eight lactating goats were fed a diet supplemented with sunflower oil (n = 4) or sunflower oil plus fish oil and additional starch (n = 4), based on the hypothesis that these dietary treatments could affect Δ9-desaturase gene expression in specific tissues. A chemical tracer, 1.5 g of [1-13C] VA as nonesterified fatty acid, was delivered by jugular injection. Goats were slaughtered 4 d later, and tissue samples were collected for the measurement of [13C]VA and [13C]RA enrichment and SCD1 and SCD5 expression. The addition of fish oil and additional starch to a diet containing sunflower oil was associated with several changes in [13CC]VA and [13CC]RA enrichment. These results support previous studies suggesting that mammary secretory tissue is the primary site of Δ9-desaturation in lactating goats. In adipose tissues, the [13 C]VA + [13C]RA enrichment was consistent with a net uptake of circulating fatty acids to reconstitute body reserves at the end of the lactation cycle. The putative uptake of [13 C]RA synthesized by other tissues precludes any conclusion from being drawn regarding potential Δ9-desaturation in the liver of goats, despite the detection of SCD1 and SCD5 mRNA in this tissue. Finally, no significant effect of dietary treatment was observed for SCD1 or SCD5 mRNA abundance in the mammary secretory tissue or other body tissues. [ABSTRACT FROM AUTHOR]

The potential benefits on human health have prompted an interest in developing nutritional strategies for reducing saturated and increasing specific unsaturated fatty acids (FA) in ruminant milk. The impact of the level and type of starchy concentrate added to diets supplemented with sunflower-seed oil on caprine milk FA composition and on mammary, omental and perirenal adipose, and liver lipid metabolism was examined in fourteen Alpine goats in a replicated 3 × 3 Latin square with 21 d experimental periods. Treatments were a grass hay-based diet with a high level of forage (F) or a high level of concentrate with either maize grain (CM) or flattened wheat (CW) as source of starch and supplemented with 130 g/d sunflower-seed oil. Milk yield was enhanced (P < 0·01) and milk fat content was decreased on the CM and CW diets compared with the F diet, resulting in similar milk fat secretion. Both high-concentrate diets increased (P < 0·05) milk yield of 10 : 0-16 : 0 and decreased trans-9,11-18 : 1 and cis-9, trans-11-18 : 2. The CW diet decreased (P < 0·05) the output of Σ C18 and Σ cis-18 : 1 and increased (P < 0·05) the output of trans-10-18 : 1 in milk. The expression and/or activity of fourteen proteins involved in the major lipogenic pathways in mammary tissues and of lipogenic genes in adipose and liver tissues were similar among treatments. In conclusion, high starch concentrates alter milk FA yield via mechanisms independent of changes in mammary, liver or adipose tissue lipogenic gene expression. Furthermore, data provided indications that mammary lipogenic responses to starch-rich diets differ between caprine and bovine ruminants. [ABSTRACT FROM PUBLISHER]

The leptin receptor ( LEPR) gene consists of 20 exons divided over 1.75 Mb. Parts of bovine LEPR exon 4 (79 bp), exon 11 (95 bp) and exon 20 (513 bp) of 20 cows (Holstein-Friesian) were sequenced ( ; ; ) in an attempt to find polymorphisms. In exons 4 and 11 no SNPs were found. In exon 20, a T to C missense mutation was found at nucleotide 115, which causes an amino acid substitution at residue 945 (T945M). Frequencies for alleles C and T were 0.93 and 0.07 respectively, in a population of 323 Holstein-Friesian cows and TT animals were not detected. Using genotypes of these cows an association study was performed for leptin concentrations during late pregnancy and lactation. Leptin concentrations were determined by radioimmunoassay (RIA). The T945M mutation showed an association with circulating leptin concentrations only during late pregnancy ( P < 0.05) but not during lactation ( P > 0.05). The CC genotype had higher concentrations than the CT genotype during this period. A combined effect with previously described leptin polymorphisms on prepartum leptin concentrations was observed, with one genotype combination having significantly lower levels of leptin up to 50 days, but interaction effects were not significant. The T945M polymorphism may have induced a structural change in the intracellular domain of the LEPR, which may have influenced the signal transduction pathway. However, the effect was found only for the heterozygous genotype because the TT genotype was not detected in this population of 323 Holstein-Friesian cows. [ABSTRACT FROM AUTHOR]

Examines the ability of the ovine mammary gland to synthesize leptin throughout pregnancy and lactation. Leptin location by indirect immunofluorescence; Temporal expression of leptin mRNA in ovine mammary gland during pregnancy and lactation; Immunofluorescent location of leptin in ovine mammary gland during pregnancy and lactation.

Previous studies in rodents have shown that the lipoprotein lipase (LPL) regulation is complex and often opposite in adipose tissue (AT) and muscle in response to the same nutritional treatment. However, neither LPL responses nor the molecular mechanisms involved in the nutritional regulation have been studied in both AT and muscle of ruminant species. To explore this, we measured the LPL activity and mRNA levels in perirenal AT and cardiac muscle (CM) of control, 7-d-underfed or 14-d-refed ewes. Underfeeding decreased (P < 0.01) LPL activity both in AT (-59%) and CM (-31%), and these activities were restored (P < 0.01) by refeeding (AT, +248%; CM, +34%). Variations of LPL mRNA level measured by real-time reverse transcription-polymerase chain reaction or by Northern blot followed variations of LPL activity: underfeeding decreased AT- and CM-LPL mRNA levels (-58 and -53%, respectively), and refeeding restored (P < 0.01) them in CM (+117%) and increased them over the baseline in AT (+640%). Quantification of either 3.4- or 3.8-kb LPL mRNA levels revealed a predominant (P < 0.001) expression of the 3.4-kb mRNA in AT (60%) and of the 3.8-kb mRNA in CM (56%), without any preferential regulation of one of these mRNA species by the nutritional status. This work reveals a tissue-specific expression pattern of the ovine LPL gene and a pretranslational nutritional regulation of its expression, which is achieved in the same direction in perirenal AT and CM. The different regulation of CM-LPL between ewes and rats probably arises from peculiarities of ruminant species for nutrient digestion and absorption and liver lipogenesis. [ABSTRACT FROM AUTHOR]

Changes in the amount and metabolism of adipose tissue (AT) occur in underfed ruminants, and are amplified during lactation, or in fat animals. The fat depot of the tail of some ovine breeds seems to play a particular role in adaptation to undernutrition; this role could be linked to its smaller adipocytes and high sensitivity to the lipolytic effect of catecholamines. Glucocorticoids and growth hormone probably interact to induce teleophoretic changes in the AT responses to adenosine and catecholamines during lactation. Fat mobilization in dry ewes is related both to body fatness and to energy balance. The in vivo beta-adrenergic lipolytic potential is primarily related to energy balance, whereas basal postprandial plasma non-esterified fatty acids (NEFA) are related to body fatness, and preprandial plasma NEFA is the best predictor of the actual body lipid loss. Several mechanisms seem to be aimed at avoiding excessive fat mobilization and/or insuring a return to the body fatness homeostatic set point. As well as providing the underfed animal with fatty acids as oxidative fuels, AT acts as an endocrine gland. The yield of leptin by ruminant AT is positively related to body fatness, decreased by underfeeding, beta-adrenergic stimulation and short day length, and increased by insulin and glucocorticoids. This finding suggests that the leptin chronic (or acute) decrease in lean (or underfed respectively) ruminants is, as in rodents, a signal for endocrine, metabolic and behavioural adaptations aimed at restoring homeostasis. [ABSTRACT FROM AUTHOR]

• Hay and corn silage induced slight differences in milk fatty acid profile. • Interaction between forage nature and lipid supplement modified dairy performance. • Linseed oil increased more milk linolenic acid yield than sunflower or fish oil. It has been well established that milk fat yield and composition are affected by different types of forage and lipid supplementation of cow diets, but there are very few direct comparisons, including different forages and lipid supplements. In this experiment, we analysed directly the interaction among 2 forage types and 3 types of lipid supplements on the responses of milk fat and fatty acid yields. Twelve Holstein cows were divided into 2 groups and received diets based on either mountain grassland hay (H, 60% of DM intake) or corn silage (C , 69%) and concentrate mixture. They were used in two replicated 3 × 3 Latin square designs (2 cows per block) to evaluate responses to feeding two basal diets (one for each Latin square) supplemented with either 2.5% fish oil (FO), 5.0% sunflower oil (SO), or 5.0% linseed oil (LO). Responses of milk fat and FA yields were different according to the interaction between different types of forage and lipid supplementation. In fact, milk fat yield was decreased by FO (when compared to other oils) with H diets, whereas it was decreased by LO with C diets. We observed a shift of trans 11- to trans 10-18:1 yields, due to changes in ruminal biohydrogenation (RBH) pathway, after 2 weeks with CSO and CLO diets. The milk 18:2 n -6 yield was increased to a larger extent with HSO than with CSO diets. Linseed oil supplementation increased more the trans 13/14- and cis 15-18:1, and 18:3 n -3 yields with H than with C diets. Linseed oil decreased more even saturated fatty acids (FA) than SO or FO with C diets, whereas no change was observed with H diets. Effects on milk FA yields were more pronounced with C than H diets, notably with the shift of trans 11- to trans 10-18:1 with C diets. For a regular milk production with a stable composition, the adaptation period for feeding a diet supplemented with vegetable lipids should be not lower than 3 weeks. We can conclude that the dose of vegetable oils that does not cause milk fat depression is under 5%. Finally, the milk nutritional quality could be improved for HLO diet (versus other diets) with lower saturated FA (SFA) and higher milk 18:3 n -3 levels. [ABSTRACT FROM AUTHOR]