Two experiments involving lactating Holstein cows were carried out to quantify the effect of a 550-g supplement of lipids from extruded rapeseed and linseed on milk fatty acid profiles and the susceptibility of milk fat to oxidation. The effect of a daily oral supplement containing 9616 IU of vitamin E (all-rac-alpha-tocopheryl acetate) on milk alpha-tocopherol and protection against oxidation was also evaluated. The intake of oilseeds decreased protein and fat contents in milk, and the proportion of all C18 fatty acids increased. The trans isomers were 2.7 and 10.76% of the milk fatty acids, respectively, for cows fed the control diet and the diet containing extruded rapeseed and linseed. The ratio of oleic to palmitic acid was doubled, and the resistance to oxidation was reduced by 30 to 40% in both experiments. The dietary vitamin E supplement increased the alpha-tocopherol concentration in milk by about 45% and was sufficient to prevent milk fat depression and oxidation. The diet containing oilseeds and supplemented with an adequate amount of vitamin E allowed cows to yield milk that could be used to manufacture butter with high oleic acid content, good spreadability, and resistance to oxidation.

Six lactating Holstein cows were assigned to a replicated Latin square design to test the effect of dietary vitamin E on milk fat depression and on the increased production of milk trans-10 C18:1 classically observed when feeding high doses of unsaturated fatty acids with low-fiber diets. Two diets (linseed diet and linseed diet + 12,000 IU of vitamin E/d) were compared during 2 periods of 21 d. The linseed diet presented a forage-to-concentrate ratio of 50:50 and contained extruded linseed (1.86 kg/d) and linseed oil (190 g/d). It was conceived to favor the "trans-11 to trans-10 shift" (low structural value and high level of unsaturated fatty acids). Milk yield and protein content were not affected by the diets. Milk of cows fed the linseed diet presented the typical symptoms of milk fat depression associated with a shift in biohydrogenation pathways: low fat content and high level of trans-10 C18:1. However, the high dose of dietary vitamin E provided significantly increased milk fat content (by 17.93%) and yield (by 15.56%) and decreased trans-10 C18:1 content (by 47.06%). In addition, it managed to significantly increase the daily yields of vaccenic (by 102.56%) and rumenic acids (by 56.67%). However, the sequence of administration of vitamin E influenced its effect, as vitamin E seemed to be more active in limiting the "trans-11 to trans-10 shift" when it was incorporated in the diet simultaneously with the fat. Once the shift had occurred, the subsequent addition of vitamin E was no longer able to completely counteract this process.

The normal microflora colonizing the digestive tract in livestock species at five to six days after birth can be summarized as following: 400 to 500 different bacterial strains for a total count of 10(14) bacteriae. The role of the gut flora is multifarious: fermentation of feed compounds, induction of anatomical and physiological changes in the intestinal cell wall structure, increase in animal resistance against enteropathogenic bacteriae, etc. In the present review, the numerous hypotheses for explaining the beneficial effects of probiotics on zootechnical performances and also the healthy aspects for men and animals are summarized, and the possible mechanisms of bacterial attachment are enumerated. The different assumptions on mode of action and fixation mechanisms of probiotics in the gut are critically discussed, and the required characteristics of the ideal probiotic are listed. Finally, some zootechnical results obtained with lactic acid bacteria are shown for calves, piglets and broilers.

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The objective of this study was to test the effects of inclusion of hop pellets (HP) and oak tannin extracts (OT) alone or in combination on N efficiency, methane (CH 4 ) emission, and milk production and composition in 2 experiments with dairy cows fed low-N rations supplemented with linseed. In both experiments, 6 lactating Holstein cows were assigned to 3 dietary treatments in a 3 × 3 duplicated Latin square design (21-d periods). Cows were fed a total mixed ration at a restricted level to meet their nutrient requirements. In experiment 1, 169 g dry matter (DM) of OT or 56 g DM of HP was included separately in the control diet (C1). In experiment 2, the additives were included together (OT-HP) in the control diet (C2) similar to C1. Diet C2 was compared with a control without linseed (C0). In experiment 1, the supplementation of the control diet with OT decreased urinary N excretion by 12%. In experiment 2, the combination of OT and HP decreased urinary N by 7%. Oak tannin extracts and HP alone or in combination did not influence the daily enteric CH 4 production of cows. Cows fed diet C0 produced 17% more enteric CH 4 daily than those fed diet C2. Intake of diet C2, which contained 6.7% extruded linseed on a DM basis (experiment 2), decreased the sum of 6:0 to 14:0 fatty acids (−16%) and palmitic acid (−26%) and increased the stearic acid (+50%), oleic acid (+36%), vaccenic acid (trans-11 18:1; +285%), rumenic acid (cis-9,trans-11 18:2; +235%), and α-linolenic acid (+100%) in milk fat. The supplementation of diet C2 with the OT-HP mixture further improved the milk's fatty acid composition. Intake of the OT alone increased α-linolenic acid by 17.7% (experiment 1). The results of this study show that at the economically acceptable dose we tested, hops had no effect on urinary N excretion, CH 4 emission, milk production, and milk composition. By contrast, supplementation of diets with oak tannin extract can be considered for reducing urinary N excretion. The combination of oak tannin and hops had no more effect than oak tannin alone except on the milk fatty acid profile, which was favorably influenced from a nutritional point of view.