Influence of Dietary Energy and Protein on Growth and Carcass Composition in Different Biological Types of Cattle2

Abstract

Two types of cattle (Angus-Hereford cross-breds, small type; and 3/4- or 7/8-Charolais and Chianina Hereford or Chianina Angus cross-breds, large type) were evaluated for their response to different dietary energy densities (2.9, 3.1, or 3.2 Meal ME/kg dry matter) (low, LE; medium, ME; and high, HE, respectively) and three dietary levels of crude protein (LP = 10, MP = 11.5 or HP = 13% of dry matter) in a 2 × 3 × 3 factorial design. The rations consisted of the following ratios of corn silage to corn plus supplement: LE, 43:67; ME, 25:75; and HE, 11:89. Small type cattle from each treatment were slaughtered after 196 and 232 days on experiment (460 ± 3 and 465 ± 3 days of age) and large type after 232 and 308 days (464 ± 3 and 566 ± 3 days of age). Increasing energy intake increased ADG in both types of cattle with HE>LE (PME = HE) and rib fat increased (LE<ME = HE) as a result of increased dietary energy intake (P<05). Up to about 325 kg live weight, small type cattle increased ADG and feed efficiency with the MP compared to the LP intake. There was no advantage for the HP compared to MP. ADG and feed efficiency increased up to 348 kg live weight in large type cattle with the HP intake compared to the LP ration. The percentage of moisture and protein in the rib were decreased and fat was increased in large type cattle fed the 13% level of crude protein compared to those fed lower levels of dietary protein. Steaks from all carcasses of both types of cattle and from all energy or protein treatments were organoleptically acceptable in a taste panel evaluation. Copyright © 1977. American Society of Animal Science . Copyright 1977 by American Society of Animal Science.