Effects of feeding a histidine-deficient diet on lactational performance of dairy cows

Abstract Text:

A 10-wk randomized complete block design study with 24 Holstein cows (days in milk, 87 ± 22 d; BW, 630 ± 56 kg) was conducted to determine the effects of feeding a His-deficient diet on lactational performance of dairy cows. Following a 2-wk covariate period, cows were blocked by days in milk, milk yield, and parity, and randomly assigned to one of the following 2 treatments: His-adequate diet [HAD; digestible His (dHis) supply of 75 g/d, or 2.8% of MP requirements] and His-deficient diet (HDD; dHis supply of 50 g/d, or 2.0% of MP requirements). Both HAD and HDD were supplemented with rumen-protected (RP) Met (Mepron; Evonik Nutrition & Care GmbH) and RPLys (AjiPro-L; Ajinomoto Co., Inc.) supplying dMet and dLys at 2.5 and 2.4% and 7.5 and 7.2% of MP requirements, respectively. At the end of the study, HDD was supplemented with RPHis (an experimental product supplying 9.3 g/d of dHis; total dHis supply of 62 g/d, or 2.5% of MP requirements) for 9 d. The diets consisted of (DM basis): 45% corn and 20% alfalfa silages and 35% concentrates. Diets contained 16.3 and 16.2% CP, respectively, and supplied MP and NE_L in excess of cow requirements. DMI, yields of milk, energy-corrected milk, and milk protein were decreased (P ≤ 0.02) by HDD (25.4, 37.6, 34.4, and 1.07 kg/d) compared with HAD (27.1, 40.5, 37.4, and 1.18 kg/d, respectively). Milk urea nitrogen was decreased (P < 0.01) by HDD versus HAD. Feed and energy-corrected milk feed efficiencies, milk nitrogen efficiency, milk fat and protein concentrations, milk fat yield, and BW change of the cows were not affected by treatments (P ≥ 0.12). Blood hemoglobin concentration was 5.4% lower (P < 0.01) in cows fed HDD compared with HAD, suggesting a provision of about 24 g of His from this endogenous depot during the 8-wk experimental period. Plasma His concentration was decreased (P < 0.01) by HDD versus HAD. Supplementation of RPHis increased DMI (26.6 vs. 25.1 kg/d, P < 0.01), but did not affect milk yield (36.0 vs. 34.8 kg/d, P = 0.28) compared with HDD during the last 9 d of the study. Overall, feeding a diet deficient in His but supplying adequate MP, Met, and Lys had negative effects on DMI and lactational performance of dairy cows. The effect on DMI was reversed when RPHis was supplemented.  

Keywords:

histidine, dry matter intake, dairy cow