Provision of a protein-rich supplement for grazing suckling female beef calves to improve productive performance and metabolic response

Objective: This study was conducted to evaluate the effects of the provision of a protein rich supplement on productive performance, and metabolic profile on grazing suckling female beef calves in tropical conditions during 150 d of experimentation. Methods: Fifty-six Nellore suckling female calves, and their respective dams were distributed in a completely randomised design and made to undergo two treatments as follows: UNS (without supplementation), and SUP (supplementation with 5 g/kg body weight [BW] of a protein supplement). Throughout the experiment, animal performance and metabolic profile were evaluated. Also, ureagenesis and gluconeogenesis were assessed for gene expression. Results: SUP female calves showed a higher voluntary intake (p<_0.03) of the diet components evaluated, digestibility of organic matter (p<_0.02) and microbial nitrogen production (MICN; p<_0.02) compared to UNS female calves. In its turn, serum urea nitrogen (p<_0.01) and insulin-like growth factor-1 (p<_0.03) levels and ureagenesis (p<_0.04) increased in SUP female calves compared to UNS female calves. Blood glucose and triglyceride levels were not affected by supplementation. The average daily gain (ADG) from SUP female calves was higher (p<_0.02) compared with UNS female calves. However, supplementation did not affect the body measures of the animals. Conclusion: In summary, provision of a protein-rich supplement improves the intake and nutrients digestibility, ADG and final BW and increases metabolic indicators of the protein status in grazing suckling female beef calves in tropical conditions.