Post-weaning growth rate effects on body composition of Nellore bulls

Abstract

Context Previously feed-restricted cattle may exhibit compensatory growth during the finishing phase. However, the efficiency in converting feed into carcass should be evaluated since cattle undergoing compensatory growth usually have high non-carcass weight gain. Aims The objective of this study was to evaluate the effect of growth rate throughout the post-weaning growing phase on subsequent feed efficiency, carcass gain, and gain composition. Methods Thirty-nine weaned young Nellore bulls averaging 230.4 ± 5.62 kg of bodyweight and 8.5 ± 0.25 months of age were used. Initially, five bulls were slaughtered as a reference initial group. The remaining bulls were randomly assigned to one of three nutritional plans to achieve Low (0 kg/day), Medium (0.6 kg/day) or High (1.2 kg/day) average daily gain (ADG) throughout the post-weaning growing phase, followed by high growth rate during the finishing phase. One-half of the bulls from each treatment were slaughtered at the end of the post-weaning growing phase, and the other one-half after the finishing phase. During both phases the feed intake, apparent digestibility, performance, and body composition were evaluated. Key results Throughout the post-weaning growing phase, High bulls had greater ADG and more efficiently converted feed into carcass, compared with other nutritional plans (P < 0.01). Throughout the finishing phase, Low bulls had greater ADG, carcass gain, and feed efficiency than High and Medium bulls (P < 0.01). Previous feed restriction did not affect (P > 0.05) apparent digestibility. During the finishing phase, previously restricted bulls fully compensated for the lost visceral organ weight, whereas the losses of bodyweight and carcass weight were only partially compensated. Throughout finishing, Low bulls had the greatest feed efficiency and profitability among nutritional plans. However, considering the overall experiment, Hight bulls converted feed into carcass more efficiently than Low bulls (P = 0.02), but did not differ from Medium (P > 0.05). Conclusions Although previously restricted bulls had greater performance and efficiency throughout finishing, the improvement was not enough to reach the same carcass weight at the same age of the unrestricted bulls. Implications Despite the greater profitability of previously restricted bulls throughout finishing, unrestricted bulls were more profitable considering both growing and finishing phases.

Carcass Traits, Meat Characteristics, and Economic Viability of Grazing Nellore Cattle Produced Under Different Supplementation Strategies in the Tropics

“…An economic analysis of the different nutritional strategies revealed that CS/CS strategy had the highest pro tability (i.e., gross revenue, pro t, and pro t index), despite it showed the greatest EOC and total cost, among the supplementation strategies evaluated (Figure 1). These results are in accordance with those of Silva et al (2020) ndings, who observed that although supplementation costs were higher when animals are supplemented with concentrate in both seasons, unrestricted animals are more pro table when considering the cost per kg of carcass produced in relation to animals that were subjected to restriction. Furthermore, the use of concentrate supplementation in at least one season is more economically advantageous than the use of mineral supplementation in both seasons, as this practice provides greater hot carcass weight and shorter nishing time for animals in a grazing system (Sampaio et al, 2017).…”

“…Data revealed that backfat thickness tended to be lower for animals supplemented with mineral salt in the dry season (i.e., MS/MS and MS/CS) compared to other supplementation strategies. This fact demonstrates that animals under feed restriction in the dry season prioritize the growth of visceral organs instead of depositing subcutaneous fat (Silva et al, 2020). Regarding ribeye area, no differences were observed across supplementation strategies; nevertheless, animals under MS/MS and MS/CS supplementation strategies tended to produce the highest hindquarter yields, demonstrating the priority in muscle deposition over the adipose tissue deposition, which is in line with other studies (Hornick et al, 1998;Silva et al, 2017).…”

“…As expected, a quantitative restriction produced by the supply of different energy density diets across the seasons (i.e., different supplementation strategies), resulted in different hot carcass weights. This agrees with Silva et al (2020) Concomitantly, the concentrate supplementation in both dry and rainy seasons (i.e., CS/CS) produced animals with the highest hot carcass weight among the other supplementation strategies evaluated. This may be due to the highest energy density of the diet supplied in this supplementation strategy compared to others explored.…”

“…To overcome the variations in nutrient inputs, grazing tropical beef cattle is commonly supplemented with concentrate in intensive production systems (Detmann et al, 2014); however, beyond supplementation level, the choice for an adequate supplementation strategy during the dry and rainy seasons may differentially infer in the growth rate of the animals (Sampaio et al, 2017). In general, a restriction of nutrients occurs in the dry season, whereas an increase of nutrient supply to animals goes in the rainy season; hence, the dynamics of nutrient across these seasons in uences the body composition and weight gain (Modzelewska-Kapituła and Nogalski, 2016;Oksbjerg and Therkildsen, 2017;Silva et al, 2020). Therefore, the selection of a correct supplementation strategy may positively affect the carcass characteristics of cattle, thereby in uencing the cattle production economic viability as well.…”

Performance, Intake, Feed Efficiency, and Carcass Characteristics of Young Nellore Heifers under Different Days on Feed in the Feedlot

“…1 is that the animals maintained their body and carcass weight gain. According to Silva et al [ 35 ], animals that received a high level of supplementation during the growing phase have more metabolically active organs. As a result, effective nutrient utilization occurs in the skeletal muscle rather than the viscera during the feedlot period.…”