Daily dry matter intake to sustain body weight of mature, non-lactating, non-pregnant cows

¹ USDA, ARS, U.S. Meat Animal Research Center, Clay Center, NE 68933-0166

^* To whom correspondence should be addressed. E-mail: Tom.Jenkins{at}ars.usda.gov.

	Abstract

To quantify the relationship between DM consumption, the ability to sustain weight per unit of DMI (weight stasis), and days to reach weight equilibrium among diverse cattle breeds, weekly individual cow BW and DMI data were recorded for mature, non-pregnant and non-lactating cows sampled from Angus, Braunvieh, Charolais, Hereford, Gelbvieh, Limousin, Pinzgauer, Red Poll, and Simmental breeds. Within each breed, cows were assigned to receive 1 of 4 daily DM allowances (56, 76, 93, or 111 g·BW ^{-0.75, kg}) of a ground alfalfa hay/corn grain-based diet. Cows were housed in pens (space for 4 animals/pen) in open front barns and fed individually using head gates. During the first 60 d of the experiment, BW were recorded every 28 d, after which BW were recorded on a weekly basis until cows were determined to have attained BW equilibrium. Individual cows were determined to be at BW equilibrium when the rate of weekly BW change did not differ from 0 over an 8-wk period. Days to reach BW equilibrium was not affected (P > 0.79) by breed but was affected by daily DM allowance (P < 0.003). The number of days required to attain BW equilibrium was greater as the rate of feeding (g of DM fed x BW ^-0.75) increased. Mean days to BW equilibrium by feeding rate increased and ranged from 103 d to 136 d. Within breed linear and the pooled quadratic regressions were significant for BW. Observed breed differences varied with feeding rate. Weight stasis estimates for mature Red Poll cows (68.3 ± 3.9) were similar to estimates for all the breeds with the exception of Limousin (72.0 ± 3.8), Braunvieh (74.0 ± 4.8) and Simmental (79.4 ± 3.8; P > 0.05) and Gelbvieh cows (82.5 ± 3.8; P < 0.05) at the lowest feeding rate. At 111 g·BW ^-0.75 rate, the estimates for Limousin (82.2 ± 3.8) were greater (P < 0.05) than the other breeds with the exception of the Pinzgauer (81.0 ± 4.3) and Braunvieh (75.7 ± 3.9) which were similar to the remaining breeds in the study (P > 0.05). The change in rank of breed estimates for BW stasis suggests a breed X nutrition interaction for BW stasis.

Key Words: beef cows, maintenance, weight stasis