Oscillating and static dietary crude protein supply: II. Energy and protein requirements of young Nellore bulls

Abstract

The objective of this study was to evaluate whole body chemical composition and energy and protein nutrient requirements for maintenance and gain of Nellore bulls. Fifty young bulls, with an average age of 7 ± 1 mo and initial body weight (BW) of 260.0 ± 8.1 kg, were used in this experiment. Four bulls were used as baseline reference animals and were slaughtered at the beginning of the experiment. Four bulls were fed at maintenance (12 g dry matter [DM]/kg of BW), whereas 42 bulls were divided into six groups (n = 7/group) and were randomly assigned to the following dietary treatments 105 (low [LO]), 125 (medium [MD]), or 145 (high [HI]) g crude protein (CP)/kg DM, LO to HI (LH), LO to MD (LM), or MD to HI (MH) oscillating CP at a 48-h interval for 140 d. At the end of the experiment, bulls were slaughtered and samples of the whole body were collected. All samples were lyophilized, ground, and composed as percentage of component of empty body weight (EBW) from each bull. A power model was used to estimate carcass, non-carcass components, and gastrointestinal content of the shrunk body weight (SBW), and CP and water present in the empty body, whereas an exponential model was used to estimate adipose tissue and ether extract (EE) present in the EBW. Nonlinear regression equations were developed to predict heat production from metabolizable energy (ME) intake and retained energy (RE). The net energy requirements for maintenance and ME for maintenance were 77 and 122.75 kcal/EBW0.75/d, respectively. The efficiency of ME utilization for maintenance was 62.7%. The equation obtained for net energy for gain (NEg) was: NEg (Mcal/EBW0.75/d) = 0.0535 × EBW0.75 × EBG0.7131, where EBG is the empty body gain, and the efficiency was 24.25%. Net protein requirement for growth (NPg) was: NPg (g/d) = 227.372 × EBG – 19.479 × RE. There was a linear increase for carcass, CP, and water present in the EBW as the animal grew. The EE deposition exponentially increased as EBW increased.

Effect of inclusion levels of low‐fat dried distillers grains in finishing diets on protein and energy intake and retention and estimation of protein and energy requirements of young Nellore bulls fed with high concentrate diets

“…However, greater differences will be found for higher weights, above maturity. It is important to mention that the average SBW of the animals described by Menezes et al (2019) (445 kg) is higher than the average SBW of the animals evaluated in this study (402 kg), which explains the difference in the proposed models. Menezes et al (2019) also proposed the following equation for estimating EWG (kg/day): EWG = 1.0119 × ADG 0.8315 , with the model coefficients close to those suggested by Equation (19).…”

“…It is important to say that some authors describe exponential models for the deposition of fat in EBW. Menezes et al (2019) proposed the following model for Nellore cattle: EE (kg) = 16.2886 × e (0.0041 × EBW) . If we consider the animal in the hypothetical example of the previous paragraph, we find a value of 72 kg of EE in EBW, a value close to that described by the equation proposed by this study (75 kg).…”

Oscillating and static dietary crude protein supply. I. Impacts on intake, digestibility, performance, and nitrogen balance in young Nellore bulls1

“…Additionally, when averaged over the entire feeding period and animals are fed to a constant endpoint, the body composition of gain and the diluting effects water gain on cost of lean weight gain may minimize the effects of protein vs. fat gain ( Tedeschi et al, 2010 ). Data regarding the chemical body composition of the bulls and its pattern of deposition can be found in a complimentary paper ( Menezes et al, 2019 ).…”

Nutrient Requirements of Zebu and Crossbred Cattle - BR-CORTE

“…Two studies were developed to evaluate the effect of reducing crude protein levels in the diets of beef cattle. In Study 1 (Menezes et al, 2019), animals were weaned, and the growing/finishing phase was conducted in a feedlot, in which static and oscillating levels of 10.5, 12.5, and 14.5 % CP in the diet DM were tested. In Study 2 (Menezes et al, 2016), animals were weaned, allocated on pasture for one year following a finishing phase in feedlot.…”