engleski

Reproductive characteristics of Pramenka breed - Lika strain sheep and the possibilities of non hormonal flock synchronisation

Introduction Pramenka sheep is indigenous, late maturing breed presenting a part of national heritage, biological and landscape diversity. It is resistant, adaptive and low productive breed. Pramenka sheep farming can respond to growing demand for organic products and restricting EC regulations about use of exogenous hormones. The aim of this study were to a) establish reproductive traits and patterns based on hormonal analysis and b) examine the possibility of advancement of sexual season in order to assure hormone free sheep products in extended period. Material and methods I Duration of seasonal anoestrus, puerperium and estrus cycle characteristic. Eight ewes and one ram were brought to the facilities of the Faculty of Veterinary Medicine, University of Zagreb and were kept in close proximity, but with no direct physical contact. Blood sampling was performed during 2 breeding seasons, 5 to 10 days apart for progesterone (P4) and testosteron (T) analysis performed by the IMMULITE system (ELISA). Measurments of scrotal circumference was also done. Also, during high sexual season, the ewes were synchronized with 2 prostaglandin injections. The animals were daily blood sampled for P4 analysis during 22 days and every 4 hours (0-3, 17-20 days) for LH. Sampling started when first animal was mounted by marking ram. Six ewes, delivered first in household (Hrvatski Blagaj, Lika region), 17-20 December, were sampled for P4: 25, 34, 41 and 51 days after lambing. II Advancement of breeding season. Melatonin implants were put to 30 ewes and 5 rams at the beginning of April. The animals were kept together (no technical conditions for isolation and light treatment). Selenium and vitamins were also given 2 times during May. Results & discussion I. The results of the first trial showed that sexual activity slightly starts by the end of July and is fully expressed by the beginning of September onward ; the season ended before February. Some P4 activity was noticed during anoestrus period (middle of April) indicating the possibility of induction of sexual activity using ram effect. The stress induced P4 peak was noticed following the transportation of the animals from Lika to Zagreb. The animals that had low body condition score expressed no progesterone activity and had no regular cyclic profiles. Based on testosterone and orchidometry, rams’ sexual activity starts in June ; ends before February. The duration of estrous cycle (period between two LH peaks) is 17.2 ± 0.61 days. Respecting puerperium, P4 activity was noticed as early as 25 and was fully developed in all ewes 51 days after delivery, a clue for the possibility of another mating during the same season. II. In order to fully evaluate the ability of melatonin implants to advance the breeding season in Pramenka Lika sheep, the results obtained so far in treated animals will be compared with untreated controls after the end of the lambing season (March 2013). Conclusion Obtained results present a guideline for veterinary practitioners and indirectly could help to maintain the sheep farmers in karstic / mountainous areas and give additional value to their work.

indigenous breed; Pramenka; reproduction; sexual season; estrous cycle; melatonin

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