اثر كمبود دائمي انسولين بر مصرف خوراك، شاخص هاي رشد، تركيب گوشت و فراسنجه هاي خون در گوسفند زل

Effect of Permanent Hypoinsulinemia on Feed Intake, Growth Parameters, Meat Composition and Blood Metabolites in Zel Sheep

To investigate effect of permanent hypoinsulinemia induction on feed intake, growth parameters, carcass composition and blood metabolitesʹ levels in Zel sheep, 4 intravenous injections of doses 0, 25, 50 and 75 mg streptozotocin /kg BW were used as control, low-dose, middle-dose and high-dose, respectively. Twenty male sheep weighing 19.4±1 kg divided into four groups as a completely randomized design. The duration of the experiment was 8 consecutive weeks, and injections were performed at the end of third week. Animals in high-dose group omitted from the experiment because of abnormalities. Feed and water intakes and animal weight were measured weekly. Blood samples were collected weekly at fasting via venipuncture. Blood metabolites and hormones were measured via spectrophotometery and radioimmunoassay, respectively. Data were analyzed as repeated measures design. Results showed that a marked hypoinsulinemia in middle-dose group occurred with a significant decrease in insulin concentrations. Leptin concentrations in middle-dose group were lower than control group (P<0.05). Middle-dose injection caused significant increases in blood glucose, triglycerides, cholesterol, total protein, blood urea nitrogen and keton body levels versus control group (P<0.05). Middle-dose group showed hyperphagia and enhanced water intake (P<0.05), but instead of increased feed intake, it was enabled to gain more weight than control group (P<0.05), and feed conversion ratio increased. Protein and fat percentages of meat and liver did not have any significant differences among groups (P>0.05). In conclusions, results showed that decreased insulin and leptin levels can enhance feed intake in sheep without improving growth parameters. Furthermore, decrease in insulin level can decrease blood glucose, triglycerides, cholesterol, total protein, blood urea nitrogen and keton body levels with no effect on meat composition.