Abstract
The objective of this study was to evaluate animal performance and carcass characteristics of 64 Nellore young bulls at 22 months of age finished in a feedlot and slaughtered at five body weights (350; 455; 485; 555 and 580 kg) fed diets containing coated or uncoated urea. The experimental design adopted was completely randomized, set in a 4 × 2 factorial arrangement, and for the variables assessed in the control animals, it was 5 × 2. No effect of interaction between slaughter weights and diets were observed, so the variables were analyzed separately, compared by polynomial contrasts and by the F test, respectively. The time animals remained in the feedlot to reach slaughter weights was 66, 88, 145 and 194 days. Average daily gain (ADG) showed quadratic behavior, with a maximum of 1.44 kg/day with animals of 491.7 kg. Dry matter intake (DMI) (kg/day) was similar in all the treatments, but it decreased linearly as body weight increased. The bionutritional efficiency worsened linearly as body weight rose. The elevation in slaughter weight resulted in linear decrease in the percentage of beef round and increase in forequarter. Backfat thickness and rib eye area of the longissimus increased linearly and the percentages of muscle and protein in the carcass reduced and those of fat and ether extract increased linearly as body weight increased. Average daily gain, DMI, feed efficiency and carcass characteristics were not affected by diets containing coated or uncoated urea. However, animals fed coated urea presenter better crude fiber and neutral detergent fiber intake.
Highlights
The feedlot is an alternative utilized by some farmers for finishing cattle
When Dry matter intake (DMI) was expressed as ratio of body weight (DMIBW), there was a linear decrease for the heavier animals (Table 3)
The data found in the literature about DMI according to slaughter weight are contradictory
Summary
The period of confinement can vary according to factors like sex, breed group and the concentrate:roughage ratio. A longer period of confinement implicates higher production cost due to the worsening in feed conversion. According to Santos et al (2011), the replacement of feeds that contain true protein by feeds with a higher content of non-protein nitrogen, such as urea, can improve the financial efficiency of feeding and reduce the need to purchase protein contents. It allows for the formulation of diets with greater inclusion of energy feeds, fibrous by-products and forages
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