Effect of dietary protein content on performance, feed efficiency and carcass traits of feedlot Nellore and Angus × Nellore cross cattle at different growth stages

Abstract

An experiment was conducted to evaluate whether a reduction in dietary crude protein (CP) and genotype affects animal performance, feed efficiency and carcass traits of beef cattle at different stages of the feedlot. Twenty-two Nellore and 22 crossbred F1 Angus × Nellore (Nellore: 8 months, initial body weight (iBW) = 212.7 kg; Crossbred: 8 months, iBW = 226.1 kg) were used in this experiment. The experiment was conducted in a complete randomized design with six replicates, in a 2 × 3 factorial design. The factors were two genotypes (Nellore and Crossbred) and three CP concentrations (100, 120 and 140 g/kg dry matter [DM]). The experimental period lasted 224 day, being divided into two stages (Backgrounding = 112 day, and Finishing = 112 day). At the end of the experiment, all animals were slaughtered to evaluate their carcass characteristics. Similar patterns were observed during backgrounding and finishing phases on intake and average daily gain (ADG) regarding genotype. Intakes of DM, organic matter, CP, neutral detergent fibre, non-fibre carbohydrates and total digestible nutrients, ADG (kg/day) and feed efficiency were greater in Crossbred animals than Nellore in both phases. During the backgrounding phase, dietary CP did not influence DM intake. However, a linear effect of CP on ADG was observed in the backgrounding phase. During finishing, Nellore cattle fed 100 g CP/kg DM presented lower ADG than Nellore fed 120 and 140 g CP/kg DM. Crossbred animals were heavier than Nellore at the beginning and end of the trial. Crossbred animals also gained more carcass, retained more CP and fat, and had a greater subcutaneous fat thickness during the experiment compared with Nellore. There was a quadratic effect of dietary CP on retained CP and dressing. The current study found that crossbred animals (F1 Angus × Nellore) not only had greater performance, but also better carcass traits compared with Nellore, representing an option for increasing productivity. Also, it is possible to adjust diets according to phase. During the backgrounding stage, 140 g CP/kg DM should be used, being reduced to 120 g CP/kg DM during the finishing stage of feedlot for Nellore and to 100 g CP/kg DM for Crossbred, without affecting performance adversely.

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

“…At the end of this period, or during the finishing phase (56 d), dietary CP content could be reduced to 100 g CP/kg DM without affecting animal performance during this phase. In agreement with Amaral et al (2018) , this study shows that reducing CP from 145 to 105 g CP/kg DM or oscillating CP supply did not affect animal performance and carcass characteristics of growing Nellore bulls.…”

“…Data from the literature suggest that for growing animals, dietary CP content influences weight gain ( Winchester et al, 1957 ), and an optimal CP for beef cattle is approximately 13% over the grow out period ( Gleghorn et al, 2004 ) and is greater during early feeding and less during the finishing phase, as cattle approach final weight ( Todd et al, 2008 ). Amaral et al (2018) developed a study with Nellore and crossbred Nellore x Angus bulls divided into three groups receiving diets with 100, 120, and 140 g CP/kg DM. This author observed that calves that were weaned and thereafter finished in feedlot should receive diets with CP content of approximately 120 g CP/kg DM during the initial growing phase (84 d).…”

TRIENNIAL GROWTH SYMPOSIUM: THE NUTRITION OF MUSCLE GROWTH: Impacts of nutrition on the proliferation and differentiation of satellite cells in livestock species1,2

“…Concurrently, as dietary protein concentration and protein deposition are increased, the rate of fat deposition decreases resulting in accrual of an increased amount of lean in the body (Cooke et al, 1972). More recently, it was reported that as dietary protein concentrations increased (100, 120, or 140 g/kg DM), there was also a linear increase in ADG of backgrounding cattle (Amaral et al, 2018). Additionally, feeding metabolizable protein at 85%, 100%, or 115% of the daily requirements also resulted in a linear increase in the weight gain of preconditioning beef steers (Moriel et al, 2015).…”

“…Although a complete review of dietary protein and AA concentrations is beyond the scope of this review, it is important to understand that adequate dietary protein nutrition is important in ensuring that optimal skeletal muscle growth occurs in livestock species. Most of the research analyzing specific AAs has been completed using human, rodent, and porcine models, but recent research does indicate that dietary protein concentration is related to gross, phenotypic changes relating to growth of skeletal muscle in cattle (Moriel et al, 2015;Hales et al, 2016;Amaral et al, 2018). To date, most of the research analyzing the impacts of nutrient status on growth of skeletal muscle in livestock has not focused on SC specifically, but rather on phenotypic changes relating to overall skeletal muscle growth.…”

Effect of metabolizable protein intake on growth performance, carcass characteristics, and feeding behavior in finishing steers

“…Protein supplementation to ruminants often increases growth performance, which makes protein a limiting nutrient for production ( Medeiros and Marino, 2015 ). However, excessive use of protein in finishing diets leads to economic losses and environmental implications due to excess of nitrogen excretion ( Amaral et al , 2018 ). In addition, N excretion in ruminants is not only related to N intake but also microbial efficiency that influences metabolizable protein (MP) supply ( Niu et al , 2016 ).…”