Abstract
ABSTRACT The objective of this study was to estimate adjustment factors of scrotal circumference for growth traits in Nellore cattle. Measurement at post-yearling of scrotal circumference from 100,107 Nellore was adjusted for six traits: age (A), body weight (BW), hip height (HH), conformation (C), precocity (P), musculature (M), and simultaneously for age and the other five traits (A-BW, A-HH, A-C, A-P, A-M), body weight and the other four traits (BW-HH, BW-C, BW-P, BW-M), and hip height and the other three [...]
Highlights
Scrotal circumference is widely used as selection criteria to improve reproductive efficiency in beef cattle breeding programs because it is easy to measure, is genetically related to reproductive traits, and its magnitude of heritability coefficient is moderate (Terakado et al, 2015; Schmidt et al, 2019)
The visual scores of conformation, precocity, and musculature ranged from 1 to 5 and are defined according to Jorge Júnior et al (2001) as: Conformation – the amount of meat in the carcass, as the animal was slaughtered at the moment of the evaluation; Precocity – the capacity of the animal to reach the minimum buildup of fat in the carcass with lower body weight; Musculature – the development of muscle, observed at the forearm, shoulder, loin and rump
The adjustment factor of scrotal circumference for body weight at 500 days presented an amplitude of 0.34293, while the amplitude of scrotal circumference adjusted for hip height at 500 days was 0.12709 and of scrotal circumference adjusted for hip height at 300 kg was 0.04426 (Table 3)
Summary
Scrotal circumference is widely used as selection criteria to improve reproductive efficiency in beef cattle breeding programs because it is easy to measure, is genetically related to reproductive traits, and its magnitude of heritability coefficient is moderate (Terakado et al, 2015; Schmidt et al, 2019). According to Ortiz Peña et al (2000), the EPD for scrotal circumference adjusted for age is useful when the objective of selection is to improve growth and sexual precocity, while the adjustment of scrotal circumference for age and body weight identifies more adequate sires for sexual precocity because growth variation is removed. Alternative adjustment of scrotal circumference for growth traits in Nellore cattle 2 process may indicate biotypes economically more efficient as they can be related to the identification of precocious animals (Koury Filho et al, 2009). Since recent studies that consider alternative adjustments of the scrotal circumference are scarce, we aimed to estimate the adjustment factors of the scrotal circumference for age, body weight, hip height, and traits evaluated using visual scores in Nellore cattle
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