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International audience; Meta-analyses have been carried out to quantify the effect of dietary vitamin E on α-tocopherol accumulation and on lipid oxidation in porcine M. longissimus. Published results of 13 (vitamin E accumulation) and 10 (lipid oxidation) experiments respectively were used for the analyses. After a number of standardization procedures, a nonlinear relationship was found between the supplementary vitamin E and the accumulation of α-tocopherol in pork which approached a maximum value of 6.4 μg/g tissue. Pork lipid oxidation levels were described in terms of Thiobarbituric Acid Reacting Substances (TBARS) values. The statistical analysis revealed significant effect of vitamin E dose, muscle α-tocopherol concentration and supplementation time on TBARS, resulting in two prediction models for lipid oxidation. Meta-analysis has proven to be a valuable tool for combining results from previous studies to quantify the effects of dietary vitamin E. Further studies, carried out with standardized experimental protocols would be beneficial for model validation and to increase the predictive power of the derived models.

Semen production was analysed in two rabbit lines (low, L and high, H) derived by 5 generations of divergent selection for 63-d body weight from a commercial heavy breed. A total of 31 bucks were collected during 18 weeks, once a week, by 2 solicitations at a 15 min interval (giving the 1 st and 2 nd rank ejaculate). Performances were recorded only one week out of two, resulting in 9 collection series. Sexual activity did no t differ between lines. A total of 256 and 226 ejaculates were observed in the L and H lines, respectively. The percent of efficient ejaculates (= fit for insemination) was markedly higher in the L line (66.5% vs. 44.2% in the H line) due to lower potential elimination for presence of urine, or insufficient volume or insufficient mass motility. Considering only the main effect of the lines, the line influenced mass motility, the volume and the concentration of the ejaculates, as well as 4 parameters from a computer assisted sperm motility analysis (path velocity, VAP, track linearity, LIN, track speed, VCL and beat cross frequency, BCF). Mass motility and the volume of the ejaculates were higher in the L line while the semen concentration was higher in the H line. Overall, the total number of sperms and the number of motile sperms per ejaculate were similar in both lines. The interaction between line and rank of the ejaculate on concentration, percent of motile sperms per ejaculate and LIN was a very interesting feature of the results. For example, in the L line, both ejaculates had the same concentration, while in the H line, the 1 st ejaculate was more concentrated than the second one. This pattern was maintained all along the experiment. The L line had highe r values of VAP, LIN and VCL but lower value of BCF. The efficient number of sperms by ejaculate, a synthetic criteria taking into account the number of motile sperms per ejaculate and the ability of the ejaculate for insemination was significantly higher in the L line: 229 vs 170 x10 6 sperms per ejaculate in the H line.

We carried out a one-generation, divergent selection experiment on residual feed efficiency in order to estimate the genetic parameters of this trait. The selection criterion was the residual feed consumption. We measured the consequences of this selection on growth, feed efficiency, and carcass composition. One generation of selection was performed on young male rabbits from a heavy weight line. They were individually caged and measured for their weight gain and feed consumption between weaning (30 days) and 65 days of age. The fatness of all the males was estimated by ToBEC measurement (Total Body Electrical Conductivity) at 65 days of age. Their offspring were bred under the same conditions and 120 males were slaughtered at 65 days of age in order to estimate the correlated response on carcass traits: dressing yield, cutting parts, fatness, ultimate pH, and colour. Genetic parameters were estimated with restricted maximum likelihood applied to an animal model. The heritability value estimated for residual feed consumption was 0.45±0.11, which was of the same order as the heritability estimated for average daily gain (0.41±0.13) and higher than the heritability estimated for the feed conversion ratio (0.27). Residual feed consumption was negatively correlated with the hind part percentage (−0.71) and correlated positively with front part percentage (0.54). The genetic correlations with dressing percentage and carcass fatness were very low. Residual feed consumption may be introduced as a selection criterion for improving feed efficiency. Thus, no significant phenotypic differences were found between offspring of high and low residual feed consumption males, except for the hind part percentage, which was higher in the low residual feed consumption line.