Metabolizable protein and amino acid requirements of growing cattle

Abstract

Metabolizable protein and amino acid requirements for growing cattle were estimated using data from 11 research trials. A total of 543 steers were individually fed a high-roughage diet supplemented with protein at several levels above a urea supplement control. The mean weight for all animals was 253 kg, with a range in mean initial to final weights of 200 to 316 kg, respectively. Daily gain ranged from -.04 to .89 kg. Metabolizable protein for each treatment group was calculated at the point at which the protein requirement was met. The sum of dietary escape protein (basal and supplemental) and calculated microbial protein represented metabolizable protein supplied per test protein source analyzed in each trial. Daily gain was regressed against calculated metabolizable protein flow using weighted regression analysis (r2 = .69, n = 45) to determine the metabolizable protein requirements for maintenance (3.8 x BW.75 g/d, where BW is expressed in kilograms) and growth (305 g/kg of live weight gain). Calculated metabolizable amino acid requirements as a percentage of metabolizable protein for a 253-kg animal gaining .49 kg/d were as follows: methionine, 3.0%; total sulfur amino acids, 5.8%; lysine, 8.0%; tryptophan, 1.0%; threonine, 5.2%; valine, 5.7%; isoleucine, 5.6%; leucine, 6.9%; phenylalanine, 3.9%; and histidine, 1.6%. The proposed requirements were based on live animal gain and intake of metabolizable protein and should represent the needs of the growing beef animal.

Models of protein and amino acid requirements for cattle

“…Seven studies conducted either in Brazil or in the United States (Boin and Moura, 1977;Fox and Cook, 1977;Danner et al, 1980;Lomas et al, 1982;Abdalla et al, 1988;Ainslie et al, 1993;Wilkerson et al, 1993) were used to compare the predictions of animal performance using the beef NRC (National Research Council, 2000), and the levels 1 and 2 of the CNCPS (Fox et al, 2004). These studies were selected because they contained adequate information to characterize the animals, feeds, management, and environment in which they were fed.…”

Disponibilidade e absorção de aminoácidos em bovinos alimentados com diferentes fontes de compostos nitrogenados

“…A disponibilidade de Met foi de 5,26 a 6,06 g/dia e a de His, de 5,21 a 6,94 g/dia. Czerkawski (1976) e Wilkerson et al (1993) determinaram Met como primeiro aminoácido limitante na dieta de bovinos, seguido de Lys e Thr. Neste estudo, a disponibilidade de Lys e Thr nas três dietas estudadas pode ser considerada adequada se comparada aos valores descritos por esses autores.…”

“…O baixo suprimento de Met para o intestino pode limitar o crescimento de bovinos (Wilkerson et al, 1993).…”

The influence of supplementation with haylage, haylage plus soybean meal or haylage plus corn dried distillers’ grains with solubles on the performance of wintering pregnant beef cows fed wheat straw

“…Changes in ADG could also be due to the variety of protein sources provided vs. using only a single protein source. Using a combination of protein sources (haylage plus soybean meal or dried corn distillers' grains plus solubles) in the diet is more likely to provide a more balanced profile of amino acids needed to satisfy the metabolizable protein requirements of the cow (Wilkerson et al 1993). According to calculated values from NRC (1996), there were differences in the ratio of UIP/DIP to CP in the treatment diets; however, the effects of higher proportions of UIP on ADG in cows fed low-quality forage is likely minimal, since calculated DIP and MP intakes met or exceeded NRC (1996) requirements.…”