PSXIII-28 - Late-Breaking: Lactational performance of dairy cows receiving supplemental His: A meta-analysis

The objective of this meta-analysis was to examine the effect of supplemental histidine (His) on dry matter intake (DMI), milk (MY) and energy-corrected milk (ECM) yields, and milk components in lactating dairy cows. A comprehensive meta-analysis was performed to data from 20 studies published in peer-reviewed journals between 1999 and 2021. In 12 of the studies His was supplemented to the diet as rumen-protected His and in the remaining experiments free His was infused into the abomasum (5 experiments), the jugular vein (2 experiments) or the duodenum (1 experiment) of the cows. The diets were based on corn silage in 60% and on grass silage in 40% of the studies. In studies where data were available (13 out of 20), metabolizable protein supply was estimated to be on average 98% (min = 85% and max = 110%) of NRC (2001) requirements. Computations were carried out using Comprehensive Meta-Analysis (V. 3.3.070). Histidine supplementation increased (P < 0.001) plasma His concentration by 59%, compared with control. Dry matter intake and MY increased (P ≤ 0.002) by 0.22 and 0.36 kg/d, respectively, whereas ECM yield tended to increase (P = 0.07) by 0.14 kg/d with His supplemented diets vs. the control. Milk protein concentration was also increased (P = 0.004) by 0.20 %-units, whereas milk fat concentration tended to decrease (P = 0.10) by 0.11 %-units with His supplementation. Further, His increased milk protein and lactose yield (P ≤ 0.05) by 0.31 and 0.14 kg/d, respectively. Overall, based on the available data, His supplementation of lactating dairy cow rations enhanced DMI, MY and milk protein concentration and yield.