Abstract

The objective of the study was to investigate the effects of supplemental selenium and chromium on blood cortisol and glucose levels on stress alleviation and the carry-over effects on performance and liver mineral contents of local beef cattle under feedlot conditions. Seventy-two Bonsmara cross weaned calves weighing on average 185 ± 20.729 kg were allocated to 12 pens of six animals each, three replicates per treatment and fed for 120 days either a standard diet (CON) or supplemented with 0.3 mg.kg ^–1 DM sodium selenite (SEL) 0.3 mg.kg ^–1 DM chromium sulphate (CHR) and a combination of Se and Cr (SEL/CHR).  Blood cortisol and glucose levels as stress parameters, feed intake and growth performance parameters were assessed. There was no statistical difference in blood cortisol levels on d0. On d14, cortisol concentrations were lower than on d0 (P<0.05) except for treatment SEL/CHR. On d42, the values were higher than on d0 and d14 except for SEL/CHR that had very low cortisol values (P<0.05). Blood glucose concentrations followed similar trend. There was no carry-over effect of stress alleviation on growth performance though SEL/CHR tended to have better ADG (P=0,148) and predicted FCR (P=0,197). Liver tissue mineral levels were within normal ranges. However, SEL increased significantly (P<0.05) liver Ca, Mg, Co and Mn while CHR decreased Ca and Mg concentrations. Selenium was positively correlated with Cu (r=0.30, P= 0.01) and phosphorus (r=0.44, P=0.0001) while Cr was negatively correlated with Ca (r=-0.50, P=0.01) and Mg (r=-0.30, P=0.01). Liver tissue minerals did not affect performance parameters. SEL/CHR might act better on stress alleviation and growth improvement. The effects on carcass characteristics and meat quality and the use of different forms of supplemental Se and Cr warrant further research.

Key words: Selenium, chromium, stress, cortisol, glucose, feedlot, Bonsmara.