Evaluation of rations of high-yielding cows with different energy levels

Abstract

The materials of the publication reflect the results of scientific research conducted on the Simmental breed dairy cows in the conditions of the “Pchany-Denkovych” farm in the Stryi district of the Lviv region. The study is based on optimizing the normalized energy nutrition of dairy cows with a milk yield of 6000 kg or more per lactation. The main objective of the research was to study the impact of different levels of energy nutrition of cows by lactation phase and its effect on productivity, hematological indicators, the level of individual rumen metabolites, digestibility of essential nutrients, nitrogen balance, and live weight dynamics. Three groups of eight cows each were selected for research. The rations of the experimental animals provided for the inclusion of a protein-fat concentrate in the compound feed at the rate of 5–10 % by nutrition. The main ration consisted of bulk fodder, cereal-bean hay, hay, silage, and balanced compound feed, which were fed from the feed table in the form of a mixture prepared in a feed mixer–the farm practices year-round uniform feeding of cows with a walking yard. The deficiency of mineral substances in the diet was replenished due to iodized salt, monocalcium phosphate, and polysalts of trace elements. Feeding and housing conditions for all experimental animals during the comparison period lasting 15 days were the same and differed in the reference period in terms of nutrient availability in percentages. The analysis of the obtained results showed that increasing the energy supply of cows had a positive effect on milk productivity. In the first period of lactation, the highest yield was obtained from cows of the third group, which indicates that the experimental animals are approaching the maximum possible potential productivity. This trend persists both in the second and third periods. The increased level of energy nutrition due to the use of protein-fat concentrate had a positive effect on the increase in the live weight of cows. During the analysis of the obtained indicators of the rumen content, a probable increase in the number of amylo- and cellulolytic bacteria was revealed - the quantitative advantage (second and third group) compared to the control is 1.52–2.33 and 1.67–2.54 million/ml. A similar pattern is observed in the number of proteolytic bacteria, which contributed to the increase in the enzymatic activity of the microflora. Regarding the digestibility of the primary nutrients of the feed, their growing trend was established in the second and third groups, which confirms the results of the balanced experiment. Thus, animals of the second group are characterized by the highest digestibility and assimilation of nitrogen. Its positive balance was (+7.1) compared to the third and (+3.0) to the first, in which the nitrogen balance was negative. The use of nitrogen for milk in these groups was the highest: from consumed – 31.7 % and from digested – 48.5 %. Thus, the conducted studies provide a reason to recommend that the farm use a protein-fat concentrate of 5% of the diet's total nutrition in the feeding of dairy cows. Its use will ensure an increase in the level of milk productivity and will make it possible to optimize the energy nutrition of cows during the calving period and mid-lactation.