Marie-Madeleine Mialon

Genetic variability of the length of postpartum anoestrus in Charolais cows and its relationship with age at puberty.

Fertility records (n = 1 802) were collected from 615 Charolais primiparous and multiparous cows managed in an experimental herd over an 11-year period. The objectives of the study were to describe the genetic variability of the re-establishment of postpartum reproductive activity and the relationship with body weight (BW) and body condition score (BCS) at calving and age at puberty. The length of postpartum anoestrus was estimated based on weekly blood progesterone assays and on twice daily detection of oestrus behaviour. The first oestrus behaviour was observed 69 days (± 25 days s.d.) post-calving and the first positive progesterone measurement (≥ 1 ng mL-1) was observed at 66 days (± 22 days s.d.) for the group of easy-calving multiparous suckling cows. Estimates of heritability and repeatability were h2 = 0.12 and r = 0.38 respectively, for the interval from calving to first oestrus (ICO). Corresponding values were h2 = 0.35 and r = 0.60 for the interval from calving to the first positive progesterone test (ICP). The genetic correlation between both criteria was high (rg= 0.98). The genetic relationships between postpartum intervals and BW and BCS of the female at calving were negative: the genetic aptitude to be heavier at calving and to have high body reserves was related to shorter postpartum intervals. A favourable genetic correlation between age at puberty and postpartum intervals was found (rgbetween 0.45 and 0.70). The heifers which were genetically younger at puberty also had shorter postpartum intervals.

An assessment of the impact of rumenocentesis on pain and stress in cattle and the effect of local anaesthesia

Rumenocentesis is commonly used to collect rumen fluid to screen for acidosis. This study was designed to investigate whether rumenocentesis induced pain and stress and, if so, whether local anaesthesia could limit this. Twenty-four dairy cows were assigned to one of three treatments: (1) rumenocentesis with local anaesthesia (AR); (2) rumenocentesis without local anaesthesia (R); and (3) local anaesthesia only (A). Treatments were performed in a restraining cage. The cows were placed in the cage on three consecutive days and anaesthesia and/or rumenocentesis was performed on the second day. Blood samples for cortisol determination and heart rate were recorded from 0.25 h before treatment until 4h after. Behaviour was noted while the cows were caged. Feed intake and milk production were measured the week before treatment, on the day of treatment, and the day after. With all three treatments, cortisol concentrations and heart rate were increased while cows were in the cage. Cortisol, cardiac and behavioural responses were not significantly higher in the R and AR treatments than the A group. Cortisol concentrations and heart rate did not change between days. Feed intake and milk production were unaffected by the treatments. It was concluded that rumenocentesis does not appear more stressful than local anaesthesia or handling.

Repeated acidosis challenges and live yeast supplementation shape rumen microbiota and fermentations and modulate inflammatory status in sheep

This study aimed to investigate the impact of repeated acidosis challenges (ACs) and the effect of live yeast supplementation (Saccharomyces cerevisiae I-1077, SC) on rumen fermentation, microbial ecosystem and inflammatory response. The experimental design involved two groups (SC, n=6; Control, n=6) of rumen fistulated wethers that were successively exposed to three ACs of 5 days each, preceded and followed by resting periods (RPs) of 23 days. AC diets consisted of 60% wheat-based concentrate and 40% hay, whereas RPs diets consisted of 20% concentrate and 80% hay. ACs induced changes in rumen fermentative parameters (pH, lactate and volatile fatty-acid concentrations and proportions) as well as in microbiota composition and diversity. The first challenge drove the fermentation pattern towards propionate. During successive challenges, rumen pH measures worsened in the control group and the fermentation profile was characterised by a higher butyrate proportion and changes in the microbiota. The first AC induced a strong release of rumen histamine and lipopolysaccharide that triggered the increase of acute-phase proteins in the plasma. This inflammatory status was maintained during all AC repetitions. Our study suggests that the response of sheep to an acidosis diet is greatly influenced by the feeding history of individuals. In live yeast-supplemented animals, the first AC was as drastic as in control sheep. However, during subsequent challenges, yeast supplementation contributed to stabilise fermentative parameters, promoted protozoal numbers and decreased lactate producing bacteria. At the systemic level, yeast helped normalising the inflammatory status of the animals.

Genetic relationship between cyclic ovarian activity in heifers and cows and beef traits in males

Records were collected in an experimental herd over an 11-year period from purebred Charolais heifers (n = 351), cows (n = 615) and young entire bulls (n = 383). The objective of the study was to estimate the genetic relationship between the components of female ovarian activity (age at puberty and postpartum anoestrus length), their growth rate and body condition score and beef traits measured on related bulls. Two methods were used to estimate age at puberty and postpartum anoestrus length: the detection of oestrous behaviour and a test of cyclicity based on plasmatic progesterone assay. This study shows the existence of significant heritability estimates for the different cyclicity traits (h2 between 0.11 and 0.38). Most of the genetic correlation coefficients between ovarian activity and growth rate of females and males are negative and favourable (rg between -0.43 and 0.06). Cyclicity is also favourably related with body condition score in young or adult females (rg between -0.65 and -0.22). The genetic relationship between female ovarian activity and proportion of adipose tissue in the male carcass is, however, close to zero. These results show that an antagonism between male beef traits measured in this study and female ovarian activity is unlikely to be a cause for concern in the short term.

Behavioural adaptations of sheep to repeated acidosis challenges and effect of yeast supplementation

This study aims to determine whether sheep modify their feeding and general behaviour when they undergo acidosis challenge, whether these modifications are maintained when acidosis challenges are repeated and whether yeast supplementation affects these modifications. Twelve rumen-cannulated wethers fed concentrate (wheat) and forage (hay) were exposed to three 28-day periods consisting of a 23-day recovery phase (20% of wheat) followed by a 5-day acidosis challenge (60% of wheat). Both diets limited food intake to 90% of ad libitum intake. Six sheep received a daily supplementation of a live yeast product, six received a placebo. Ruminal pH was recorded continuously. Daily consumption of wheat, hay, water and weekly consumption of salt were monitored. Behavioural observations were performed twice in each period: once under the recovery phase and once under acidosis challenge. These observations included video recordings over 24 h (time budget), social tests (mixing with another sheep for 5 min) and nociception tests (CO2 hot laser). As expected, sheep spent more time with a ruminal pH below 5.6 during challenges than during recovery phases (12.5 v. 4.7 h/day). Sheep drank more water (3.87 v. 3.27 l/day) and ingested more salt (16 v. 11 g/day) during challenges. They also spent more time standing than during recovery phases, adopting more frequent alarm postures and reacting more slowly to the hot stimulus. More severe behavioural modifications were observed during the first challenge than the two other challenges. Significant concentrate refusals were observed during challenge 1: from days 3 to 5 of this challenge, sheep ate only half of the distributed concentrate. Sheep were also more active and more aggressive towards each other in challenge 1. These behavioural modifications disappeared as the challenges were repeated: no behavioural modifications were observed between challenges and recovery phases during periods 2 and 3, and furthermore, sheep rapidly ate all the concentrate distributed during the third challenge. Focusing on the effects of yeast, the only differences registered between the two groups concerned ruminal pH, that is, mean ruminal pH values in the supplemented group were lower during the first challenge (5.11 v. 5.60) but higher during the third challenge (5.84 v. 5.28). In conclusion, our experiment suggests sheep can adapt to acidosis challenges, especially with yeast supplementation. Otherwise, ruminal pH values remained low during challenges, indicating that the modifications of general and feeding behaviour in subacute ruminal acidosis situations are not due exclusively to low ruminal pH values.

Puberty in Charolais heifers in relation to growth rate. 2. Genetic variability

The genetic variability of age at puberty estimated by the age at the first observed oestrus and the age at the first positive progesterone test was described for 351 Charolais heifers, the progeny of 60 sires. The relationship between age at puberty and growth rate of the heifers was also studied. Estimates of heritability were 0.34 for the age at the first observed oestrus and 0.27 for the age at the first positive progesterone test. The genetic correlation between these two criteria was high (r = 0.94). Negative environmental relations existed between age at puberty and growth rate of the betters until 1 year of age and with mature weight. The genetic relationship between puberty criteria and growth rate was also negative. Heifers with a high genetic potential for growth also had a high potential for an early puberty. Puberty age criteria were, however, independent of the degree of weight maturity at I year of age but negatively related to adult weight. Weight maturity at the first oestrus was highly correlated (rg = 0.70) with age at the first oestrus. (© Elsevier / Inra)

Inheritance of duration of fertility in female common ducks ( Anas platyrhynchos ) inseminated in pure breeding or in inter-generic crossbreeding with Muscovy drakes ( Cairina moschata )

Ducks (common, Muscovy and mule ducks) are the third most important bird species in animal production for human consumption worldwide. Our study aimed to improve the efficiency of mule duck breeding, thus contributing to the efficiency of food production in general. In the common duck, females can be bred either with males of the same species (i.e. in pure breeding (PB) subscript p) or in inter-generic crossbreeding (CB; subscript c) with Muscovy drakes to produce the hybrid mule duck. The aim of the present study was to estimate the genetic parameters of several indicators of duration of fertility, considered to be a trait of the female duck, within and between breeding schemes and, in particular, to estimate the purebred-crossbred genetic correlation (rg pc). These indicators were maximum duration of fertility (MD), that is, the time interval between insemination and the last fertilised egg, the number of fertile eggs (F) and of hatched ducklings (H) after a single artificial insemination (AI), and the fertility rate over days 2 to 12 after AI (F 2,12), taking three sub-periods (F 2,4, F 5,8, F 9,12) into account. A total of 494 females and 2655 inseminations were involved. PB resulted in longer duration of fertility (MD p = 8.1 v. MD c = 6.4 days). Heritability (h 2) was higher for MD p (estimate ± s.e.: 0.27 ± 0.04) than for MD c (0.15 ± 0.04), but both traits were highly correlated with each other (rg pc = 0.85 ± 0.07). F p and F c had similar heritability (h 2 around 0.24) and displayed a high genetic correlation (0.78 ± 0.07). The same was true for H p and H c (h 2 around 0.17 and rg pc = 0.88 ± 0.05). The heritability estimates were 0.24 ± 0.03 for F 2,12p and 0.20 ± 0.04 for F 2,12c, with a 0.80 ± 0.07 genetic correlation between each other. Permanent environmental effects influenced MD p far less than MD c, F p less than F c, but H p and H c to the same extent. The high values for rg pc (>0.78) indicated that the same genes are involved in the duration of fertility for both PB and CB. Unlike CB, initial fertility for PB (F 2,4p) was not correlated to overall fertility rate and to duration of fertility and probably involves different genes, if any. In both breeding schemes, indirect selection on F would be better than direct selection on H to improve H, and easier to implement than selection on MD. Moreover, any gain in one breeding scheme will have its correlated counterpart in the other one, because of the high values of rg pc.