The possibility for oestrus synchronization by salt-freesalt diet in some sheep breeds reared in Bulgaria

N. Vasilev, K. Nedelkov, N. Todorov

Abstract: The purpose of these studies was to determine the effectiveness of the salt-free-salt diet, which is widely applied in Bulgaria as a non-hormonal method for oestrus synchronization of ewes. The main point of this diet consists of complete deprivation from salt in ewe’s diet for approximately two weeks followed by the addition of 15-20 g dietary salt per ewe per day for 5-7 days. Three group experiments have been carried out. The first experiment was conducted with Tsigai ewes, the second – with Karakachan Sheep, and the third group experiment has been carried out with ewes of the Bulgarian Dairy Synthetic Population. The animals of same breed were divided into two groups equalized by age and BCS. Both groups were placed at the same conditions of feeding and keeping. Control groups received regularly salt, while experimental groups was subject to the salt-free-salt diet. According to literature data a few days after supplementing ewes with a high dose of salt, almost 50% of ewes came in oestrus. In our experiments tracking of oestrus behavior and insemination of ewes started on the third day from the introduction of high salt doses. From the 3rd to the 12th day after giving salt, the following percentages of ewes from the different breed came in oestrus: Tsigai breed – 15.7% from 134 ewes in the control group and 13.5% from 133 ewes subject to the salt-free- salt diet; Karakachan Sheep breed – 16.4% from 55 ewes in the control group and 25,9% from 54 ewes subject to the salt-free-salt; Bulgarian Dairy Synthetic Population Sheep – 3.2% from 154 ewes in the control group and 3.8% from 159 ewes subject to the salt-free- salt diet. Total for all sheep breeds, from 343 ewes in the control groups at oestrus were 10.2% and from 346 ewes subject to the salt-free- salt diet – 11.0%. Three, 10 and 17days after inclusion of 20 g common salt in diet one out of five ewes from the control group had increased blood progesterone concentration up to 1.796 ng/ml. In the group fed the salt-free-salt diet the progesterone values were bellow 0.841 ng/ml in all ewes. The ultrasonographic examinations performed in June, coinciding with the late anoestrous period, showed a corpus luteum in ewe with increased values of progesterone. In the beginning of the breeding season at the 10th day after giving 20 g salt, 9 out of 20 ewes subject to the salt-free- salt diet formed a corpus luteum vs. 7 out of 20 ewes in the control group. Group experiments, assays of serum progesterone and ultrasonographic examinations revealed no significant influence of high amounts of dietary salt on the onset of oestrus from the 3rd to 12th days after the supplementation. In conclusion, there is not significant effect of salt-free-salt diet on in provoking induction of oestrus in ewes.

Keywords: breed; ewes; oestrus synchronization; progesterone; salt-free-salt diet; ultrasonography

Date published: 2019-08-22