Effects of various protein levels in the ration of dairy heifers on their growth rate and biochemical status

When breeding dairy cattle, scientists and specialists focus special attention on their productive qualities (milk yield per lactation, fat and protein content, growth rate of young animals, etc.) and the influence of both genetic and paratypic factors on them. The impact of several dietary factors is especially relevant. Therefore, the purpose of this study was to determine the influence of dietary protein concentration, ۲۰.۸۷% (control), ۲۳.۴۹% (Mid), and ۳۰.۵۲%, on the growth of young dairy cattle bred in the northern region of Kazakhstan. The study involved ۶۰ Holstein heifers, aged ۹۰ days (± ۵ days), with a body weight of ۱۰۷.۲ ± ۰.۴۸ kg. Their daily consumption of dry matter was ۲.۵ kg day-۱ which contained ۱۰.۱۰-۱۰.۶۰ MJ metabolizable energy, indigestible protein ۱۴.۴-۱۷.۸% and crude fiber ۲۲.۶-۲۴.۶%. The body weight of newborn calves in all groups did not differ and was ۳۱.۸-۳۲.۶ kg. At the age of ۶ months, difference in body weight in the control, Mid, and High groups were ۱۸۱.۱ kg, ۱۹۸.۶ kg, and ۲۰۰.۸ kg respectively. The gain of calves in two experimental groups exceeded that of the control by ۹.۷% (p < ۰.۰۰۱) and ۱۰.۹% (p < ۰.۰۰۱), respectively. No differences in blood glucose were found. Highest AST values were observed in the control compared to Mid (۵.۱۴ U L-۱) and High (۸.۲۵ U L-۱). The Coefficient of Ritis value was within ۲.۷۴-۳.۱۱. Research indicates that a ratio in dry matter with an optimal proportion of indigestible protein ۲۳.۴۹% and degradable protein ۷۰% was economically justified.

کلیدواژه ها:

Dairy herd ، Growth and development intensity ، body weight ، Average daily gain ، Feed digestibility ، Neutral-detergent fiber ، Acid-detergent fiber