PRODUCTIVE AND REPRODUCTIVE PERFORMANCE OF RABBITS EXPOSED TO HEAT TREATMENT UNDER DESERT CONDITIONS

Abstract

This study aimed to release the heat shock protein 70 (HSP70) by using heat shock exposure programs and investigate its effects on physiological responses and performance of Hi-Plus rabbits under hot desert conditions of South Sinai during production period One hundred and twenty-one day old of female Hi-Plus rabbits were randomly divided into six equal treatments (20 rabbits/ treatment), namely T1, T2, T3, T4, T5and T6. (T1) served as control. The rabbits of 2nd, 3rd, 4th, 5th and 6th treatments were exposed to heat shock program at different ages (36±1 °C for 3 hours from 12:00 - 15:00 for 3 successive days). T2 exposed at 3 days of age, T3 exposed at 25 days of age, T4 exposed at 60 days of age, T5 exposed at 3 and 25 days of age and T6 exposed at 3, 25 and 60 days of age. After heat shock exposure all treatments returned to be reared under hot conditions HSP70 expression in the rabbits of T2, T3, T4, T5 and T6 was significantly increased as compared to the rabbits in T1. Rectal and fur temperatures and respiration rate were significantly decreased in the rabbits which exposed to heat shock programs as compared to the rabbits in T1. Red blood cells count, packed cell volume and hemoglobin concentration increased in the rabbits of T2, T3 and T4 as compared to the rabbits of T1. Total protein and globulin concentrations increased in the rabbits of T5 when compared to the rabbits in T1, T2 and T6. Alanine transaminase concentration decreased in the rabbits of T2, T3, T4, T5 and T6 as compared to the rabbits in T1. However, rabbits of T2 and T4 showed an increase in total antioxidant capacity when compared to the rabbits in T1. Tri-iodothyronine hormone increased in the rabbits of T2, T3, T4, T5 and T6 as compared to the rabbits in T1.However,corticosterone hormone decreased in the rabbits of T3, T4, T5 and T6 when compared to the rabbits in control group. Conception rate was higher in the does of T5 than that in T3, T4 and T6. Gestation length was significantly increased in the does of T3 when compared to the does in T1.Viable litter size at birth was significantly increased in the does of T6 as compared to those in T5 and T1. In addition, litter size at weaning was increased in the does of T6, T4, T3 and T2 as compared to the rabbits in T1. Litter weight at birth and at weaning, productive efficiency index, feed conversion and cost of feeding for producing one kg live weight were improved in the does of T2, T3, T4, T5 and T6 as compared to the rabbits in control group. Overall mortality rate from birth to weaning was lower in kits of the does of T2, T3, T4 and T5 than that in control group. In conclusion, applying early heat shock exposure programs for rabbits, especially exposure to heat shock at 25 days of age might increase HSP70 formation and enhance acclimation of rabbits, which led to enhance physiological immune responses and consequently reproductive performance and production under severe heat stress conditions in desert.