The objective of this study was to evaluate the effect of a GnRH-vaccine in the ram lamb. Experiments were performed using 20 male lambs, randomly divided into a test (GnRH-immunization) and control group (physiological NaCl-solution). At a body weight of 20 kg (age 2-3 months) and three weeks later, all animals of the test group received 2 ml of Improvac (CSL Limited, Parkville, Victoria, Australia). The body weight as well as the blood testosterone concentration were measured weekly for 16 weeks. Thereafter, blood samples for testosterone analysis were taken monthly in immunized lams only. After the booster injection testicular growth was suppressed and plasma testosterone remained at low values < 0.1 ng/ml for at least 12 weeks. The mean corresponding testosterone concentrations for the control lambs ranged between 0.1 and 0.9 ng/ml plasma. An increase of testosterone was observed in 8 of 10 immunized animals between 3 to 7 months after the booster dose. The control lambs showed a tendency for better growth rate than vaccinated animals, but the difference was not significant. Our results demonstrate that in prepubertal ram lambs two immunizations with Improvac, three weeks apart, can suppress testosterone secretion and testicular growth at least for three months after the booster injection. For a suppression of reproductive function longer than three months after the second vaccination, a third immunization is needed at this time or when testicular growth is beginning.

Currently, there is a lack of detailed information about sheep used for biomedical research. Therefore, a European survey was conducted among sheep users gathering information on the current situation, with emphasis on animal selection criteria and issues encountered in practice. The ultimate goal was to identify needs for improvement, which will subsequently lead to a refinement and reduction of the total number of animals used for experimental studies. From the 84 respondents, 77.4% were veterinarians, 71.4% were employed at academic institutions and 63.1% had worked with sheep as research animals for more than 5 years. The majority of the respondents were using females (79.8%) with no clear age preference, mainly for surgical procedures and testing medical devices. The main criteria for choosing a sheep supplier were the animals’ health status, their availability, the trust and experience in the sheep provider and the animals’ uniformity. Approximately 60% of the respondents had encountered problems in their sheep not related to the experimental protocol and almost half of them did not have a health monitoring program for their animals. In conclusion, there is definitely a need for refinement in selecting sheep used in biomedical research, with their health status as possible starting point.

No abstract

The objective of this study was to evaluate the effect of two synthetic progestagen preparations Chlormadinone acetate (CAP, Chronosyn, Veterinaria AG Zürich) and Medroxyprogesterone acetate (MPA, Nadigest, G Streuli & Co. Uznach) on cycling activity and fertility in sheep. A flock of 28 non pregnant white alpine sheep was randomly divided into three groups, A (n = 10), B (n = 9) and C (n = 9). During a period of 4 weeks the cycling activity was confirmed by blood progesterone analysis. Thereafter, the animals of group A were treated with 50 mg CAP, those of group B with 140 mg MPA and those of group C with physiological saline solution. All injections were given intramuscularly. Suppression of endogenous progesterone secretion lasted from 28 to 49 days (mean = 39 days) in group A and from 42 to 70 days (mean = 50 days) in group B. The synchronization effect of both preparations was unsatisfactory as the occurrence of first estrus was distributed over a period of 3 weeks in group A and 4 weeks in group B. These findings could also be confirmed by the lambing period which lasted 52 days in group A and 36 days in group B. Control animals lambed within 9 days due to the synchronizing effect of the ram. The first fertile estrus was observed 36 days (group A) and 45 days (group B) after the treatment. In group A all 10 animals and in groups B and C 8 of 9 ewes each became pregnant. Parenteral progestagen application with CAP and MPA is a simple, safe and reversible method of estrus suppression in the sheep. The minimal suppressive duration of 4 (CAP) and 5 weeks (MPA) is not sufficient when a period of 3 months (alpine pasture period) is desired.