The Effect of Water and Food Restriction on Physiological and Functional Traits of Lori-Bakhtiari Lambs and Their Crosses

Crossbreeding of fat-tailed native sheep with well known high performance thin-tailed sheep is currently widely used as a rapid solution to enhance production and reproduction, and reduction of fat-tail of native sheep. Nevertheless, comparison studies about native and crossbred animal performance in different environment is necessary for sheep husbandry industry.

This study was performed in the summer using 20 Lori-Bakhtiari (Lori) and 20 Lori-Bakhtiari×Romanov (F1) (Cross) sheep with an average weight of 31.6±2.5 kg in eight treatment with five-repetition for each in a completely randomized design with 2×2×2 factorial array including breed (Lori and Cross), water (free water and water restriction), and food (free food and food restriction). Unrestricted animals had free access to water and food, while water-restricted animals had free access to water for only one hour a day, and food-restricted animals were fed only with 0.45 to 0.65 percent of their body weight. After six weeks of treatments, lambs slaughtered and carcass traits were measured.

Food restriction has widely affected the measured traits in comparsion to water and breed and significantly reduced rectal temperature, respiratory rate, water intake, final weight, carcass weight, Carcass cuts and internal organ weight, fat-tail, visceral fat, total body fat, testis weight and volume (p≤0.01), while increased the water-to-feed ratio and carcass yield without fat-tail (p≤0.007). Water restriction had lesser effects and caused a significant increase in the difference between the maximum and minimum rectal temperature in each period (p<0.05), and decrease in water consumption (p=0.0001), but had no effect on other functional, physiological, and carcass traits. Crossbreeding also significantly reduced fat-tail and total carcass (p˂0.0001), and increased visceral fat, carcass yield without fat-tail, the proportion of carcass cuts, and testis weight and volume (p≤0.01), but had no effect on other traits.

In general, in normal food conditions (regardless the type of access to water) crossbreed animals performed better than Lori, but there is no differencess between them in severe food restriction. Therefore, it could be concluded that in all conditions F1 generation could make the carcass healthier and reduce the generation interval due to less carcass fat and faster maturation.