Search

International audience; Breeding for resilience requires a better understanding of intra-flock variability and the related mechanisms responsible for robustness traits. Among such traits, the animals’ ability to cope with feed fluctuations by mobilizing or restoring body reserves (BR) is a key mechanism in ruminants. The objective of this work was to characterize individual variability in BR dynamics in productive Romane ewes reared in extensive conditions. The BR dynamics profiles were characterized by combining individual longitudinal measurements of BW and body condition scores (BCS) over several production cycles. Historical data, including up to 2628 records per trait distributed in 1146 ewes, underwent cluster analysis. Two to four trajectories were observed for BW depending on the cycle, while three trajectories were found for BCS, whatever the cycle. Most trajectories suggested that BR dynamics were similar but the level of BR may differ between ewes. Nevertheless, some trajectories suggested that both BR dynamics and levels were different for a proportion of ewes. Clustering on BW and BCS profiles adjusted for individual level trends, resulted in differences only in the level of BW or BCS, rather than differences in trajectories. Thus, the overall shape of trajectories was not changed considering or not the individual level trend across cycles. In addition to individual variability, the ewe’s age at first lambing and litter size contributed to the distribution of the ewes between the trajectories. Regarding the entire productive life, three trajectories were observed for BW and BCS changes over three productive cycles. Increase in BW at each cycle suggested that ewes kept growing up until 3 to 4 years old in our conditions. Similar alternation of BCS gains and losses across cycles suggested BR dynamics might be repeatable. Many individual trajectories remained the same throughout a ewe’s life, whatever the age at first lambing, parity or litter size. Our results demonstrate the relevance of using BW and BCS changes for characterizing the diversity of BR mobilization–accretion profiles in sheep in a long timespan perspective.

Excessive mobilization of body reserves during the transition from pregnancy to lactation imposes a risk for metabolic diseases on dairy cows. We aimed to establish an experimental model for high v. normal mobilization and herein characterized performance, metabolic and endocrine changes from 7 weeks antepartum (a.p.) to 12 weeks postpartum (p.p.). Fifteen weeks a.p., 38 pregnant multiparous Holstein cows were allocated to two groups that were fed differently to reach either high or normal body condition scores (HBCS: 7.2 NEL MJ/kg dry matter (DM); NBCS: 6.8 NEL MJ/kg DM) at dry-off. Allocation was also based on differences in body condition score (BCS) in the previous and the ongoing lactation that was further promoted by feeding to reach the targeted BCS and back fat thickness (BFT) at dry-off (HBCS:gt;3.75 andgt;1.4 cm; NBCS:lt;3.5 andlt;1.2 cm). Thereafter, both groups were fed identical diets. Blood samples were drawn weekly from 7 weeks a.p. to 12 weeks p.p. to assess the serum concentrations of metabolites and hormones. The HBCS cows had greater BCS, BFT and BW than the NBCS cows throughout the study and lost more than twice as much BFT during the first 7 weeks p.p. compared with NCBS. Milk yield and composition were not different between groups, except that lactose concentrations were greater in NBSC than in HBCS. Feed intake was also greater in NBCS, and NBCS also reached a positive energy balance earlier than HBCS. The greater reduction in body mass in HBCS was accompanied by greater concentrations of non-esterified fatty acids, and β-hydroxybutyrate in serum after calving than in NBCS, indicating increased lipomobilization and ketogenesis. The mean concentrations of insulin across all time-points were greater in HBCS than in NBCS. In both groups, insulin and IGF-1 concentrations were lower p.p than in a.p. Greater free thyroxine (fT4) concentrations and a lower free 3-3'-5-triiodothyronine (fT3)/fT4 ratio were observed in HBCS than in NBCS a.p., whereas p.p. fT3/fT4 ratio followed a reverse pattern. The variables indicative for oxidative status had characteristic time courses; group differences were limited to greater plasma ferric reducing ability values in NBSC. The results demonstrate that the combination of pre-selection according to BCS and differential feeding before dry-off to promote the difference was successful in obtaining cows that differ in the intensity of mobilizing body reserves. The HBCS cows were metabolically challenged due to intense mobilization of body fat, associated with reduced early lactation dry matter intake and compromised antioxidative capacity.

This work was realized to evaluate lactation stage, physiological state, somatic cell count (SCC) and body condition score (BCS) on production and composition of cow's milk from Gir and Guzerat breeds were studied. Ninety-eight cows were analyzed and classified according to their physiological state, lactation stage, SCC and BCS. Milk production was weighed monthly to obtain production data. Composed samples were collected in vials containing preservatives and sent to the laboratory for analysis. Data were used for statistic descriptive analysis and analysis of variance. Higher milk production in the first 60 days of lactation was observed. Fat, protein and total solids concentration increased according to the increase of days in milk; while lactose concentration decreased. Higher levels of fat, protein and total solids in milk of non-pregnant cows were observed; while pregnant cows had higher daily production and higher lactose content in their milk. Higher lactose levels in milk were observed in animals with lower SCC. The BCS had no effect on milk composition or on somatic cell count. Zebu cow milk production and composition are influenced by lactation stage, physiological state and SCC. RESUMO. Neste trabalho, objetivou-se avaliar o efeito do estádio de lactação, estado fisiológico, contagem de células somáticas (CCS) e escore de condição corporal (ECC) sobre a produção e composição do leite de vacas Gir e Guzerá. Foram utilizadas noventa e oito vacas, que foram classificadas de acordo com o estado fisiológico, estádio de lactação, CCS e ECC. O leite foi pesado mensalmente para obtenção dos dados de produção. Amostras compostas coletadas em frascos contendo conservante foram enviadas ao laboratório para análises. Os dados foram submetidos a análises estatísticas descritivas e de variâncias. Verificou-se maior produção de leite nos primeiros 60 dias de lactação. Os teores de gordura, proteína e extrato seco aumentaram com o avançar da lactação; enquanto o teor de lactose decresceu. Foram observados maiores teores de gordura, proteína e sólidos totais no leite de vacas vazias; enquanto as vacas gestantes apresentaram maior produção diária e maior teor de lactose no leite. Maiores teores de lactose foram verificados em animais com menor CCS. O ECC não teve efeito sobre a composição e escore de células somáticas do leite. A produção e composição do leite de vacas zebuínas sofrem influência do estádio de lactação, do estado fisiológico e da CCS.

This work was realized to evaluate lactation stage, physiological state, somatic cell count (SCC) and body condition score (BCS) on production and composition of cow's milk from Gir and Guzerat breeds were studied. Ninety-eight cows were analyzed and classified according to their physiological state, lactation stage, SCC and BCS. Milk production was weighed monthly to obtain production data. Composed samples were collected in vials containing preservatives and sent to the laboratory for analysis. Data were used for statistic descriptive analysis and analysis of variance. Higher milk production in the first 60 days of lactation was observed. Fat, protein and total solids concentration increased according to the increase of days in milk; while lactose concentration decreased. Higher levels of fat, protein and total solids in milk of non-pregnant cows were observed; while pregnant cows had higher daily production and higher lactose content in their milk. Higher lactose levels in milk were observed in animals with lower SCC. The BCS had no effect on milk composition or on somatic cell count. Zebu cow milk production and composition are influenced by lactation stage, physiological state and SCC.

Excessive negative energy balance (EB) has been associated with decreased reproductive performance and increased risk of lameness and metabolic diseases. On-farm, automated EB estimates for individual cows would enable dairy farmers to detect excessive negative EB early and act to minimize its extent and duration by altering feeding. Previously, we have shown that EB can be estimated from frequent measurements of body weight (BW) and body condition score (BCS) changes, referred to as EBbody. In this study, we investigated the robustness and sensitivity of the EBbody method to assess its genericity and on-farm applicability. We used 5 data sets with BW of lactating cows (name of data set in parenthesis): 65 Holstein cows in a French feeding trial (INRA); 6 Holstein cows in a British feeding trial (Friggens); 31 Holstein cows and 17 Jersey cows in a Danish feeding trial (DCRC); 140 Holstein cows in a British feeding trial (Scotland's Rural College, SRUC); and 1,592 Holstein cows on 9 Danish farms with milking robots (automatic milking system). We used the INRA and Friggens data sets to develop a dynamic formula to correct BW for increasing residual gut-fill (RGF) during early lactation. With the DCRC data, we tested the effect of smoothing parameters and weighing frequency on EBbody. Also, 2 robustness tests were performed using the SRUC data to test the effect of diet change on BW and the automatic milking system data to test the effect of farm on BW variation. Finally, we combined the results into a blueprint describing different ways to calculate EBbody depending on the purpose and on the availability of BCS. The dynamic RGF adjustment resulted in a lower empty BW during early lactation than that obtained with the previously used constant RGF. The double-exponential smoothing method used to correct for meal-related gut-fill was robust to choice of smoothing parameters. Cows should be weighed at least once every 4 d during early lactation to capture the duration of negative EBbody. Our EBbody method proved robust to diet changes. Finally, although cow BW varied significantly between farms, the quantile regression smoothing of BW did not bias the estimation of weight differences between herds. In conclusion, these results validate the applicability of the EBbody method to estimate EB across a range of farm conditions, and we provided a blueprint that enables the estimation of EBbody for individual cows on-farm using only frequent BW, in combination with BCS when available.

The aim of this study was to compare the energy balance and dynamic of body reserves in rabbit females divergently selected for longevity. One hundred and twenty-nine females from a high longevity line (HL) and 131 females of a low longevity line (LL) were studied from the 1st to the 3rd kindling. Litter size and weight and female body weight were measured at kindling (1st, 2nd and 3rd), insemination (2nd and 3rd) and at weaning (1st and 2nd). The total body electric conductivity (TOBEC) method was used to estimate the body reserves in all females at artificial insemination and at weaning, and at kindling in females that achieved parturition. Energy balance between the 11th and the 21th d of lactation was also calculated for these females. No significant difference was found for fertility or for the number of offspring born alive and weaned. However, the total number of offspring born was higher in the LL line than in the HL line at the 2nd parturition (+1.12±0.46 g; Pnd artificial insemination (+107.0±29 g; P=0.049), leading to a similar weight between the lines at the 2nd artificial insemination. There was no significant difference between lines for estimated energy used for growth between the 11th and the 21th d of lactation, or for estimated milk production (2365±30 g in HL line vs. 2398±30 g in LL line), estimated using the weight gain of the kits between the 11th and 21st d of lactation, for feed intake measured during this period (351±5 g/d in HL line vs. 359±5 g/d in LL line) or for energy balance (–6.11±0.3 MJ in HL line vs. –6.30±0.3 MJ in LL line). However, body energy content was higher in HL females than in LL (+2.72±0.64 MJ; P=0.001). In conclusion, selection for higher functional longevity results in a better ability of females to use body reserves in their early reproductive life.

The overall sustainability and innovative capacity of small ruminant sector in Europe have to be improved to cope with current and future economic, environmental and societal challenges. This involves improving robustness in sheep to cope with fluctuating environmental conditions, for instance to increase grazing. The ability of ewes to mobilize or to restore body reserves is a key mechanism to cope with fluctuations in feed resources. The purposes of this work were to characterize the different patterns of BW and BCS variations throughout productive cycles and to analyze the genetic variability of BW and BCS variations in meat sheep. Temporal changes in body reserves dynamics were investigated using Body Weight (BW) and Body Condition Score (BCS) measured frequently throughout repeated entire productive cycles in ewes reared exclusively outdoors in harsh conditions. Cluster analysis showed three different clusters for BCS variations whatever productive cycle and one to four clusters for BW variations depending on productive cycle. Major clusters were mainly characterized by body reserves accretion during dry-off period and early pregnancy and body reserves mobilization during mid-pregnancy and suckling. The heritability values were low to medium for BW variations (h2=0.11 to 0.19) and BCS variations (h2=0.06 to 0.15). Moderate to high genetic correlations between BW and BCS variations indicated both traits were genetically related. High negative genetic correlations for BCS and BW variations between dry-off period and pregnancy and/or suckling indicated body reserves mobilization and accretion were two genetically correlated processes. The present data demonstrated body reserves variations were heritable indicating such traits could be used in selection to increase robustness.

Reproductive performance of dairy cows has been declining while their milk production was improving. The strong genetic selection that was applied on milk production is considered to be responsible for this. Each step of the reproductive process has been impacted: abnormal ovarian activity is more common in the current population, the duration and intensity of oestrus has dramatically decreased and the occurrence of pregnancy failures has increased. The consensus in the literature is that reproduction is impaired because dairy cows are investing most of their resources in milk production. The aim of this Ph.D. thesis is to explore the effect of alternative selection strategies based on milk fat and protein content on robustness of dairy cows. Our hypotheses were that at similar genetic merit for milk solids yield, compared to cows with high genetic merit for milk yield,dairy cows with high genetic merit for fat and protein contents (i) are exporting less energy in milk and are consequently safeguarding their body reserve; (ii) have better reproductive performance (earlier resumption of ovarian activity, more intense oestrus, better ability to ensure pregnancy). Our results suggest that cows selected for production through high fat and protein content instead of high milk yield would resume ovarian activity earlier, have similar oestrus intensity but more pregnancy failures. These intriguing results suggest that the steps of the reproductive process are genetically partly disentangled. Selecting dairy cows for fat and protein content is not a promising way to improve repro; Les performances de reproduction des vaches laitières se sont dégradées parallèlement à l’augmentation de leurs performances de production. L’intense sélection réalisée sur la production laitière est tenue responsable de cela. Chaque étape du processus de reproduction a été affectée : les anomalies de cyclicité ovarienne sont plus fréquentes dans la population actuelle, la durée et l’intensité des chaleurs ont diminué drastiquement, et les échecs de gestation sont plus fréquents. La littérature s’accorde sur le fait que la reproduction est affectée parce que la majeure partie des ressources est investie dans la production laitière. L’objectif de cette thèse de doctorat est d’étudier l’intérêt d’une stratégie de sélection alternative basée sur un fort potentiel génétique de taux butyreux et protéique sur la robustesse des vaches laitières.Les hypothèses testées étaient que par rapport aux vaches à fort potentiel de production laitière, celles à fort potentiel de taux butyreux et protéique (i) exportent moins d’énergie dans le lait et donc préservent leur réserves corporelles, (ii) ont de meilleures aptitudes à se reproduire. Nos résultats montrent que les vaches à fort potentiel de taux butyreux et protéique ont un retour de cyclicité plus précoce, une expression des chaleurs similaire mais plus d’échecs de gestation que celles à fort potentiel de production laitière. Ces résultats intrigants suggèrent que les étapes de la reproduction sont partiellement découplées sur le plan génétique. Sélectionner les vaches laitières sur les taux butyreux et protéique dans le but d’amé

International audience; To investigate laying decision and clutch size determination in indeterminate layers, we analysed in-nest activity (nest presence, and copulation, prey deliveries, and entrance frequencies) and female body mass change, as well as their relation to clutch size variation in five Barn Owl pairs (Tyto alba) nesting in eastern France. Body mass of the female and behaviour [copulation frequency, entrance frequency, and prey delivery to the nest by the male (in number and mass)] were monitored using an automated weighing system and a video camera. There was a consistent change of behaviour and foraging activity among pairs ca. 18 days before laying indicating that the females may be tied to the nest at this time. Barn Owls being indeterminate layers have their clutch size determined at the oviposition of the first egg of the clutch. Window correlation analyses between the clutch size and the female body mass gain indicate that the clutch size might be determined no later than a few days before the laying of the first egg. Our results suggest that female Barn Owls may use the pre-laying period to determine the clutch size using cues such as the male food deliveries (a proxy for male quality).

Effects of parity (primiparous, PRIM vs multiparous, MULT) and litter size (singletons, SING vs twins, TWIN) on metabolic profiles from 1 wk before lambing to the end of lactation were studied in 48 Lacaune dairy ewes reared in confinement during most of the year and grazed on improved pastures at the end of lactation (summer). Another group of 48 ewes was incorporated during the milking period (ie, from 1 wk after weaning), to measure the effects of milking frequency (1 vs 2 milkings per day) on intake, milk production and composition, and body energy usage. Thus, in a 2 × 2 × 2 factorial design, ewes (n = 96) were allocated to homogeneous groups according to body weight (BW) and body condition score (BCS) and were monitored from late pregnancy to late lactation as a function of parity (PRIM, n = 48; MULT, n = 48), litter size (LSi) (SING, n = 40; TWIN, n = 56) and daily milking frequency (FREQ; milked once, ONE; n = 48; or twice, TWO; n = 48). Individual BW, BCS, plasma metabolites, and metabolic hormones were measured regularly (ie, 9 consecutive sampling dates). The BW was higher in MULT but no differences because of LSi or FREQ were detected at the intra-parity group level. The BCS was higher in MULT and in ewes with SING throughout the experiment. The latter was related to the demands for body reserves mobilization, as expressed by higher nonesterified fatty acids and β-hydroxybutyrate concentrations in ewes with TWIN from late pregnancy to weaning (35 d postpartum) in both PRIM and MULT ewes. This was consistent with higher insulin in MULT and higher triiodothyronine, leptin and insulin-like growth factor 1 in ewes with SING during this period. Differences in energy balance because of FREQ were evident after interpretation of plasma nonesterified fatty acids, glucose, insulin, and leptin concentration during the milking period. At similar feed intakes, ewes in ONE were in positive balance with regard to TWO. Overall, clear effects of parity, LSi, physiological states, and FREQ on metabolic profiles were found because of differences in nutrient partitioning when combining these experimental factors. Without considering FREQ, changes in metabolic measures in milking period were marginal compared with the periparturient adjustments performed until weaning to compensate energy deficiencies.

International audience; The objective was to study the effects of body condition score (BCS) at calving on dairy performance, indicators of fat and protein mobilization, and metabolic and hormonal profiles during the periparturient period of Holstein-Friesian cows. Twenty-eight multiparous cows were classed according to their BCS (0 to 5 scale) before calving as low (BCS ≤2.5; n = 9), medium (2.75 ≤ BCS ≤ 3.5; n = 10), and high (BCS ≥3.75; n = 9), corresponding to a mean of 2.33, 3.13, and 4.17 points of BCS, and preceding calving intervals of 362, 433, and 640 d, respectively. Cows received the same diets based on preserved grass to allow ad libitum feed intake throughout the study, and lactation diet contained 30% of concentrate (dry-matter basis). Measurements and sampling were performed between wk −4 and 7 relative to calving. No significant effects were observed of BCS group on dry matter intake (kg/d), milk yield, BCS loss, plasma glucose, and insulin concentrations. The high-BCS group had the lowest postpartum energy balance and the greatest plasma concentrations of leptin prepartum, nonesterified fatty acids and β-hydroxybutyrate postpartum, insulin-like growth factor 1, and milk fat content. Milk fat yield was greater for the high- than the low-BCS group (1,681 vs. 1,417 g/d). Low-BCS cows had the greatest concentration of medium-chain fatty acids (e.g., sum of 10:0 to 15:0, and 16:0), and the lowest concentration and secretion of preformed fatty acids (e.g., cis-9 18:1) in milk fat. Milk protein secretion was lowest in the low-BCS group, averaging 924, 1,051, and 1,009 g/d for low-, medium-, and high-BCS groups, respectively. Plasma 3-methylhistidine was greater in wk 1 and 2 postpartum compared with other time points, indicating mobilization of muscle protein. Plasma creatinine tended to be lower and the 3-methylhistidine: creatinine ratio was greater in low- compared with medium- and high-BCS cows, suggesting less muscle mass but more intense mobilization of muscle protein in lean cows. High-BCS cows were metabolically challenged during early lactation due to intense mobilization of body fat. Conversely, limited availability of body fat in low-BCS cows was associated with increased plasma indicators of body protein mobilization during the first weeks of lactation, and lower milk protein secretion. These results should be confirmed using an experimental approach where calving BCS variation would be controlled by design.

absent

SUMMARYImmunity is hypothesized to share limited resources with other physiological functions and this may partly account for the fitness costs of reproduction. Previous studies have shown that the acquired immunity of female common eider ducks (Somateria mollissima) is suppressed during their incubation, during which they entirely fast. Corticosterone was proposed to be an underlying physiological mechanism for such immunosuppression. Therefore,the current study aimed to assess the effects of exogenous corticosterone on acquired immunity in captive eiders. To this end, females were implanted with corticosterone pellets at different stages of their incubation fast. We measured total immunoglobulin levels, T-cell-mediated immune response, body mass and corticosterone levels in these females and compared them with those of control females prior to and after manipulation (i.e. corticosterone pellet implantation). To mimic corticosterone effects on body mass, we experimentally extended fasting duration in a group of females termed `late fasters'. Implanted females had corticosterone levels 6 times higher and lost 35% more mass than control females. Corticosterone levels in `late fasters' were similar to those in control females but body mass was 8% lower in the former. The decrease in the immunoglobulin levels of corticosterone implanted females was twice as high as in control females, while the T-cell-mediated immune response was not significantly affected by the treatment. We found a decrease in the T-cell-mediated immune response only in `late fasters' (by 60%), while the immunoglobulin level was not lower in this group than in corticosterone implanted or control females. Our study shows that in incubating eiders,exogenous corticosterone only decreased humoral immunity. We suggest that the immunosuppressive effect of corticosterone could be mediated through its effects on body reserves. Further experiments are required to determine the relationship between body condition and immune system in fasting birds.

The Barbarine sheep is characterised by a fat-tail, whose mass varies between 1 and 4 kg. Its management is traditionally based on spring mating. The ability of this fat-tailed ewe to mobilise its body reserves has been demonstrated in lactation and the dry period by experimentally varying the food supply. The severely underfed ewe (200 g oat hay) can survive 161 days and lose 36% of its body weight (BW), with a change of 8.8 kg of dissected adipose tissue (AT) and 3.4 kg of muscle. It reached this stage with an empty BW of 24 kg containing 12% of AT. The fat tail exerts a role as a body reserve mainly through its mass rather than through its ability to be rapidly mobilised. In such situations, plasma NEFA and 3-hydroxybutyrate concentrations are first almost doubled, then decline in permanently underfed ewes, showing the ability of Barbarine ewes to adjust their lipid metabolite concentration in order to limit the toxic effects of high concentrations and therefore prolong survival. By the end of a re-feeding period, Barbarine ewes returned to their initial BW, lipid and protein mass. This breed has a good fertility, which can, however, be depressed in cases of undernutrition. However, if the mating period is extended, the overall reproductive performance is generally satisfactory. Poor nutrition during pregnancy may reduce lamb birth weight and affect subsequent growth, however, in traditional conditions, ewe and lamb mortality rates are surprisingly low in this breed. In normal birth weighted lambs, the post-weaning growth performances of grazing lambs are moderate but in feedlot conditions the conversion rate is rather low and carcass adiposity is high. This review shows that the Barbarine sheep, and specially the ewe, is well adapted to the local conditions mainly because of its high fertility and its ability to deposit and mobilise body reserves, La race Barbarine est caractérisée par une queue grasse dont la masse varie de 1 à 4 kg. Le système traditionnel d’élevage de la Barbarine est basé sur la lutte de printemps. La capacité de mobilisation des réserves chez cette brebis a été démontrée, aussi bien sur brebis allaitantes que sur brebis taries,en faisant varier expérimentalement les apports alimentaires. Des brebis sévèrement sous-alimentées(200 g de foin d’avoine par j) survivent 161 jours en perdant 36 % de leur poids vif initial (PV), avec8,8 kg de tissus adipeux (TA) et de 3,4 kg de muscle. Elles atteignent cet état avec un PV vide de24 kg contenant 12 % de TA. Le gras caudal agit comme réserve corporelle plutôt par sa masse que par son aptitude à être mobilisé rapidement. Dans de telles conditions, les concentrations plasmatiques en AGNE et 3-hydroxybutyrate sont transitoirement doublées puis elles déclinent, chez les brebis toujours sous-alimentées, montrant la capacité de la Barbarine à ajuster la concentration des métabolites lipidiques pour limiter les effets toxiques des fortes concentrations et prolonger la survie. En fin de période de réalimentation, les brebis Barbarine retournent à leur PV et masses lipidique et protéique initiales. Cette race a une fertilité satisfaisante, qui peut diminuer en cas de sous-nutrition. Cependant, si la période de lutte est suffisamment longue, la fertilité s’améliore. La sous-nutrition durant la gestation peut entraîner une réduction du poids des agneaux à la naissance. Cependant et dans de telles conditions, le taux de mortalité des agneaux est étonnamment faible. Chez des agneaux à poids de naissance normal, la croissance post-sevrage est modérée au pâturage mais,en bergerie, elle reste faible avec une efficacité alimentaire particulièrement basse et une adiposité élevée. Cette revue montre que la brebis de race Barbarine est bien adaptée aux conditions locales en raison de sa bonne fertilité et sa capacité à déposer et mobiliser des réserves corporelles