Blood Biochemical Parameters and Physiological Indices in Fattened Heat Stressed Lambs Fed with Higher Protein Level and Glutamine Supplementation

The research aims to determine the effect of protein levels and glutamine supplementation on the blood biochemical parameters and physiological indices of fattened lambs during heat stress. Sixteen male lambs of the Afshari breed (average BW=31.5 +/- 0.22 kg; aged 3-4 months) were randomly selected and assigned into four groups for forty-five days. The experimental treatments included animals fed with a basal diet (C), basal diet supplemented with glutamine at the rate of 0.2 g/kg of body weight (BW) (G), basal diet with 10% higher protein (CP), and basal diet with 10% higher protein and glutamine (GP). The mean temperature-humidity index was 82.26, which indicated heat stress condition during the experimental periods. Changes in body weight, dry matter intake, and feed conversion ratio were similar in all the groups. Rectal temperature and respiratory rate significantly decreased with glutamine supplementation (P=0.018, P=0.004 and P=0.051, P=0.004 on the 30th and 45th days respectively). Glutamine supplementation in G and GP groups decreased concentrations of creatinine (P=0.013 on the 30th), lactate (P<0.0001 on the 15th day) and conversely increased glucose concentration (P=0.027, P=0.012 and P=0.001 on the 15th, 30th and 45th days), but the effect of glutamine supplementation on blood urea nitrogen, cholesterol, and triglycerides was not significant. The significantly increased blood urea nitrogen, cholesterol (P<0.05) and triglycerides (P=0.001, P=0.019 on the 15th and 30th) when the higher level of protein was used; however, glucose, creatinine, and lactate were found non significant. The interaction of glutamine and protein level significantly increased glucose concentration (P=0.010 and P=0.005 on the 15th and 45th days) and decreased cholesterol and triglyceride concentrations in fattening lambs (P<0.05). The results showed that glutamine supplementation improves the health state of heat-stressed lambs during the fattening period.