Effects of limited water availability on adaptation and performance parameters in sheep under thermal stress

The present study was carried out to investigate the changes in adaptation and performance data of local Awassi and crossbreed Çukurova Meat Sheep (ÇET; 3/8 Rambouillet, 3/8 İle De France, 1/8 İvesi, 1/8 Sakız) types raised under high temperature and humidity conditions when they were exposed to limited water availability. For this purpose, 15 Awassi sheep and 15 ÇET sheep were taken to experiment for six weeks after a 2-week adaptation period in order to determine their water consumption and to ensure adaptation to individual pens. In the experiment, two main treatment groups were formed as Awassi (Control, İK; 15% restricted, İ15 and 30% restricted, İ30) and ÇET (Control, ÇK; 15% restricted, Ç15 and 30% restricted, Ç30). Each treatment group was divided into three subgroup, which received ad-libitum water, received 15% less than ad-libitum water consumption and received 30% less than ad-libitum water consumption, thus is created in total six treatment groups. Performance parameters, physiological adaptation parameters, nutrient digestion and the change of some biochemistry and hormones in the blood in order to determine the effects of water restriction on sheep were studied. The results of the study showed that water restriction applied at different levels had no significant effect on feed consumption, live weight, body weight gain and change in some body measurements (P>0.05). In the bloods taken from the animals, it was found that urea and sodium levels were significantly affected by water restriction only in the second week of the experiment (P<0.05), and other blood biochemistry parameters were similar to the control groups in all periods (P>0.05). Additionally, it was determined that the levels of cortisol and vasopressin (ADH) hormones in blood were significantly affected by the water restriction in the second week and at the end of the experiment (P<0.05). In terms of nutrient digestion, except for the cellulose level in the feces taken in the middle of the experiment, it was observed that all other nutrient levels were not affected by water restriction during experiment (P>0.05). It was determined that the respiratory rate taken in the morning measurements was significantly affected by water restriction in the first week, fourth week and last week of the experiment (P<0.05). In addition, according to measurements taken in the morning at the end of the experiment, it was determined that water restriction was effective on pulse rate (P<0.01). However, it was determined that water restriction had no significant effect on respiratory rate and pulse rate on measurements made at noon and evening (P>0.05). Rectal temperature and body temperature were found to be similar between treatment groups in weekly measurements taken throughout the experiment (P>0.05). As a result, it was determined that Awassi and ÇET sheep raised in hot and humid conditions tolerate water restriction up to 30% of their daily ad-libitum water consumption without any yield loss.