Performance of crossbred Holstein x Gyr dairy cows, with and without energy supplementation, in BRS Kurumi elephant grass pastures

Abstract

This study evaluated the effect of energy supplementation with ground corn on the performance of crossbred dairy cows in BRS Kurumi elephant grass pastures managed under rotational stocking during the rainy season. Six Holstein × Gyr cows were used, with average milk production, body weight, body condition score, and days in milk of 18.0±2.89 kg day-1, 560±66 kg, 2.50±0.21, and 99±12, respectively. The experimental design used was the complete reversion (switchback), and the evaluations were conducted over three grazing cycles, with adaptation periods of 14 days and six days of sample collection. The concentrate supplement (ground corn) was supplied twice a day, at a rate of 2 kg cow-1day-1in the morning and 1 kg cow-1day-1in the afternoon (as-fed basis). A reduction of 23.4% was observed in the pasture dry matter (DM) intake (PDMI) in cows that received energy supplementation, which corresponds to 2.96 kg day-1 less of PDMI when compared to the group without supplementation. This corresponds to a substitution rate of 1.1 kg of pasture per kg of concentrate consumed (DM basis), which reduced the intake (kg cow-1day-1) of neutral detergent fiber and crude protein by 18.9% and 13.9% in the cows that received ground corn. There were increases of 11.8%, 9.0%, and 10.1%, respectively, in the milk yield, the 3.5% fat-corrected milk yield, and the energy-corrected milk yield of the cows that received ground corn. The response to supplementation in kg of milk per kg of DM of concentrate consumed was 0.57, and the milk contents of fat, protein, and lactose did not differ between treatments. The energy supplementation with 3 kg cow-1day-1of ground corn resulted in an increase of 11.8% in the milk yield of Holstein × Gyr dairy cows grazed on BRS Kurumi elephant grass, as well as promoted increases in the daily protein, lactose, and total solids yields. In addition, the provision of 3 kg day-1of ground corn for lactating cows grazing on BRS Kurumi increased the efficiency in the use of dietary nitrogen.