Ewe colostrogenesis : estimation of Immunoglobulin G1 (IgG1) concentrations and mass variability ; La production de colostrum chez la brebis : évaluation de la variabilité de la concentration et de la masse d’immunoglobulines G1(IgG1)

In ewe, because of the syndesmochorial placentation, maternal immunity is mediated exclusively by early and high quality colostrum intake. The purpose of our study was to evaluate the feasibility of a rapid and cheap characterization of colostrum yield and quality in ewes at lambing and to investigate some potential factors of variation. Based on the analysis of 300 samples, our results show that refractometry can be used to discriminate between low (less than 50 g/L IgG1) and high concentrated colostrum with best performances obtained at the 24 % Brix cut-off (sensibility 81.8 %; specificity 82.5 %). The colostrometer yielded similar performances (sensibility 78.5 %; specificity 84.5 %) at the 75 g/L cut-off value. However both rapid tools cannot be advised to give a precise estimation of colostrum IgG1 concentration, because of the large prediction interval. The IgG1 concentration and colostrum volume produced up to 18 hours post-partum in 66 ewes appeared to be highly variable between ewes and were influenced by several factors among which the body score condition at lambing and the udder health. Finally the colostrum volume, IgG1 and butterfat amounts produced up to 12 hours after lambing were not statistically related to the kinetics of cortisol, progesterone and prolactin between 15 days before lambing and 12 hours after lambing. Others factors should therefore be investigated to better understand the variability of colostrum volume and concentration production in ewes. ; Chez la brebis, la placentation syndesmochoriale impose une prise colostrale précoce et de qualité pour la survie de l’agneau. L’objectif de ces travaux était d’apporter des éléments de réponse sur la faisabilité d’un phénotypage rapide et peu couteux des brebis sur la qualité et la quantité de colostrum produit après la mise bas et d’investiguer certains facteurs potentiels de variation de la production. Chez les ovins, la détection au réfractomètre des colostrums de concentration inférieure à 50 g/L d’IgG1 est apparue optimale au seuil ...