Gultyayeva E. Metabolic processes and productivity of cows depending on the dietary fat content and pH in the rumen

The purpose of the research was the effect of supplements to the diet with different content and type of fat on rumen fermentation, blood indices and milk yield of cows. There were five experiments performed. In the first experiment, enzymatic processes in the rumen in vitro were studied. Rumen content was incubated with sunflower or rapeseed oils and sunflower, rapeseed or soybean oil-cakes. To the experimental incubates in addition mix of sodium bicarbonate, calcium carbonate and magnesium carbonate were added. Mix of carbonates stimulated fiber degradation, increased concentration of protein and microbial nitrogen, total lipids, NEFA, triacylglycerols and decreased the concentration of ammonia and lactate in the rumen content. Sodium bicarbonate, calcium and magnesium carbonates added to incubation of rumen content increased the part of stearic acid and proportion of fatty acids with an odd number of carbon atoms and a branched carbon chain. Carbonates mixture reduced the fraction of 10-trans-oleic acid (18:1n10t) and increased the fraction of 11-trans oleic acid (18:1n11t). In the second experiment, we studied the effect of this carbonate supplement on cows fed diets with different fat content in postpartum period. The first group received a typical balanced diet. In the diet of the second group, the amount of fat was increased by replacing the soybean meal with extruded full-fat soybeans. Cows of the third and fourth groups received diets of the first and second groups with the addition of 100 g of sodium bicarbonate and 50 g of magnesium carbonate and calcium per head per day. The trial lasted 2 months. The addition of the buffer mixture to the diet contained soybean meal lead to a decrease in the rumen of ammonia concentration by 15% and lactate - by 20%, but in those received soybeans - only reducing of lactate by 18%. With an increase in the amount of unsaturated fat in the diet of cows, the proportion of oleic (cis-9 18:1) and linoleic (cis-9,12 18:2) acids in milk increased. The buffer mixture reduced the proportion of these acids for maintenance on both diets, but the proportion of trans-11 linoleic acids, on the contrary, increased. Adding to the diet the carbonates mixture showed insignificant effect on milk yields, but increases the fat content of the milk, which positively affected the fat corrected milk yield.