Effect of short transport during di-oestrus and pro-oestrus on cortisol levels and oestrous behaviour of sheep

Abstract

Two experiments were conducted to evaluate the effect of short transport stress on ewes during di-oestrus and pro-oestrus. In Experiment 1, intra-vaginal sponges containing fluorogestone acetate were inserted into ewes for a period of 12 days. A gonadotrophin (PMSG) injection was given at the time of sponge withdrawal to induce oestrous. To dissociate the possible effect of PMSG during pro-oestrus, a second experiment was designed in which prostaglandin was used as the oestrous induction factor. Ewes in both experiments were subjected to 30 min of transport by truck. In addition, oestrous behaviour and serum cortisol concentration were evaluated. Control groups consisted of un-transported ewes. In both experiments, cortisol concentration was greater (P <0·01) in transported than in un-transported animals. No difference (P> 0·05) was found between moving the ewes during pro-oestrous or di-oestrus (0·30±0·03 v. 0·53±0·18 ng/ml and 3·88±0·97 v. 2·94±0·73 ng/ml in Experiment 1 and 2 respectively). The number of ewes detected in oestrous was similar (P>0·05) among those stressed during di-oestrus, pro-oestrus or un-transported animals within each experiment (66, 47 and 42% respectively in Experiment 1 and 96·7 in all situations in Experiment 2). In general, higher cortisol concentration and more ewes displaying oestrous behaviour were detected in Experiment 2. It was concluded that under the conditions of these experiments, no difference was found in the proportion of ewes displaying oestrus regardless of the phase of the oestrous cycle in which they were transported.