Fateme Ahamadi; hamid Amanlou; Najme Eslamian Farsuni; Tahere Amirabadi Farahani
Volume 23, Issue 3 , September 2021, , Pages 363-374
Abstract
The objective of this study was to investigate the effect of decreasing dietary protein content with supplementing protected methionine (pMet) and lysine (pLys) on intake, milk yield, metabolic status, and apparent digestibility of nutrients in Holstein fresh cows. Immediately after calving, 16 cows ...
Read More
The objective of this study was to investigate the effect of decreasing dietary protein content with supplementing protected methionine (pMet) and lysine (pLys) on intake, milk yield, metabolic status, and apparent digestibility of nutrients in Holstein fresh cows. Immediately after calving, 16 cows with the similar BCS and parity were randomly assigned to two treatments. Experimental diets provided equal amounts of lysine (132 to 133 g/d) and methionine (40 to 43 g/d). The treatments were: a diet containing 18.35 % CP without supplementing pMet and pLys (HP); and a diet containing 16.45 % CP with supplementing rumen-protected amino acids (LPML). Individual dry matter intake and milk yield were recorded daily during fresh period. Blood samples were collected at 0, 3, 7, 14 and 21 d after calving to determine the serum concentrations of mineral and metabolites. Feed intake was not affected by experimental diets but milk yield was higher for HP cows than cows in LPML (P < 0.01). The yield of milk protein, lactose, fat and concentration of milk urea nitrogen (MUN) were higher in HP cows compared to LPML (P < 0.05). Compared to HP cows, cows in LPML had lower blood urea nitrogen (BUN) and higher serum concentrations of total protein and globulin (P < 0.01). Based on the results of the present study, reducing dietary protein content while maintaining the supply of limiting amino acids decreased lactational performance and feed efficiency of Holstein fresh cows.