Abstract

- We investigated the impact of weaning at 30, 75, and 180 days of age on performance, body measurements, and rumen development (using the beta-hydroxybutyrate biomarker) of beef calves until 190 days of age. A total of 64 Brangus calves were assigned to three treatments: hyper -early (W30), weaned at 32 +/- 0.89 days of age (n = 22, 10 males and 12 females); early (W75), weaned at 77 +/- 0.95 days of age (n = 20, 12 males and eight females); and conventional (W180), weaned at 183 +/- 0.82 days of age (n = 22, 13 males and nine females). Body weight (BW), average daily gain (ADG), beta-hydroxybutyrate (beta HBA), and morphometric measurements were evaluated. These variables were influenced by an interaction between treatment and days and were not affected by the sex of calves. The W30 calves experienced weight loss from 30 to 40 days of age compared with the W75 and W180 calves. Consequently, at day 75, W30 animals were lighter and had lower body length, thoracic circumference, withers height, and croup height compared with the W75 and W180 calves. However, no significant differences in BW were observed among treatments at 85 days of age. Additionally, W30 calves exhibited higher ADG and a moderate correlation with beta HBA levels. Weaning calves at 30 days of age may negatively affect their performance until the sixth week after weaning, but there is no impairment in performance at 190 days of age.