Mid-infrared (MIR) spectrometry was used to estimate the fatty acid (FA) composition in cow, ewe, and goat milk. The objectives were to compare different statistical approaches with wavelength selection to predict the milk FA composition from MIR spectra, and to develop equations for FA in cow, goat, and ewe milk. In total, a set of 349 cow milk samples, 200 ewe milk samples, and 332 goat milk samples were both analyzed by MIR and by gas chromatography, the reference method. A broad FA variability was ensured by using milk from different breeds and feeding systems. The methods studied were partial least squares regression (PLS), first-derivative pretreatment + PLS, genetic algorithm + PLS, wavelets + PLS, least absolute shrinkage and selection operator method (LASSO), and elastic net. The best results were obtained with PLS, genetic algorithm + PLS and first derivative + PLS. The residual standard deviation and the coefficient of determination in external validation were used to characterize the equations and to retain the best for each FA in each species. In all cases, the predictions were of better quality for FA found at medium to high concentrations (i.e., for saturated FA and some monounsaturated FA with a coefficient of determination in external validation >0.90). The conversion of the FA expressed in grams per 100mL of milk to grams per 100g of FA was possible with a small loss of accuracy for some FA.

A genetically modified Bt176 corn hybrid (Rh208Bt)--providing control of European corn borer damage--and the conventional isogenic hybrid (Rh208)--harvested as whole plant silage--were evaluated in three separate feeding trials to verify that the in vivo feeding value was substantially equivalent among modified and conventional hybrids. In the first trial, after a week of preexperiment, two sets of six Texel sheep, housed in digestibility crates, were fed silage sources of Rh208 and Rh208Bt hybrids, and silage of three additional control varieties of low, intermediate, and high feeding value (Rh289, Adonis, and Adonis bm3) for 1 wk. Feed offered to sheep was adjusted to maintenance requirements based on metabolic body weight. Agronomic and biochemical traits were similar among the Rh208 and Rh208Bt hybrids. Organic matter digestibility (67.1 and 67.6%), crude fiber digestibility (52.9 and 54.2%), and neutral detergent fiber digestibility (50.2 and 49.0%) were not significantly different among Rh208 and Rh208Bt hybrids. In the second trial, two sets of 24 Holstein cows were fed silage from Rh208 and Rh208Bt corn hybrids for 13 wk, 9 wk after calving, and including 2 wk of preexperiment. Fat-corrected milk yield (31.3 and 31.4 kg/d), protein content (31.7 and 31.6 g/kg) and fat content (36.7 and 37.0 g/kg) in milk of dairy cows were unaffected by hybrid source. Body weight gains of cattle were not different. However, intake was significantly higher in cows fed Rh208Bt silage. In the third trial, five midlactation multiparous Holstein cows were successively fed the silage from Rh208 and Rh208Bt corn hybrids 2 or 3 wk. Data were considered only for the last week of each period. There were no significant effects on protein fractions, fatty acid composition, or coagulation properties of milk between Rh208 and Rh208Bt fed cattle. Cattle and sheep can perform equally well with a conventional or a genetically modified Bt176 corn silage.

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Les acteurs des filières laitières bovine, caprine et ovine françaises se sont regroupés dans le programme PhénoFinlait autour d’un but commun : caractériser la composition du lait en Acides Gras (AG) et protéines afin de la maîtriser. La quantification des AG et des protéines devait être possible à grande échelle et à moindre coût avant d’identifier des leviers permettant d’adapter cette composition à la demande. PhénoFinlait s’est organisé autour de trois objectifs : i) caractériser précisément la composition du lait, ii) phénotyper et génotyper une large population de femelles sur l’ensemble du territoire français et iii)identifier les leviers génétiques et alimentairespermettant de maîtriser cette composition. La spectrométrie dans le Moyen InfraRouge (MIR) a été choisie comme méthode de quantification à haut débit des composants du lait. Elle permet la quantification précise en routine de 15 à 27 AG, des quatre caséines et des deux protéines majeures du lactosérum. Une collecte de données de grande ampleur a été mise en œuvre dans plus de 1 500 élevages bovins, caprins et ovins. Les données de production laitière, les spectres MIR du lait, les informations sur le stade physiologique des femelles et sur la composition de l’alimentation des troupeaux ont été recueillies. Plus de 12 000 vaches, chèvres et brebis ont été génotypées. Finalement, plus de 800 000 données représentatives des situations de l’élevage français ont été stockées dans une base de données destinée à l’étude du déterminisme génétique de la composition en AG et en protéines du lait, et des facteurs d’élevage l’influençant.