The effect of GnRH (Dalmarelin) given on day 12 post-mating on ovarian function and embryo development in lohi sheep at Southern Punjab,Pakistan

The present study was conducted at sheep and goat research station,bahauddin zakariya university,multan. the objectives of this study were to investigate the effects of gnrh analogue (dalmarelin) treatment on day 12 of pregnancy on ovarian function,plasma hormone concentrations and embryo development to improve litter size. sixteen lohi sheep 3-4 years old,weighing 44±0.4 kg (mean ± s.e.m) were selected. the daily feed/ration was hay,seasonal fodder,tree looping and 250g concentrate per sheep. sheep were mated to ram at synchronized estrus by two i/m injections of 2ml pgf2a analogue (dalmazin) given at 11 days apart. these animals were divided into two treatment groups (8/group) through random stratification by body weight. animals were injected an either saline (group i) or 2ml gnrh (group ii) on day 12 post-mating. the blood samples were collected from jugular venipuncture (3ml) with a disposable syringe from 1 hour before and 0,2,4,6,8,24,48,and 72 hours after treatment. plasma progesterone concentrations detected by elisa were higher (p<0.05) in sheep as compared with saline treated controls. oestradiol concentrations in gnrh treated animals were significantly (p<0.05) higher than those in the controls. the effects of gnrh on conceptus growth and litter size were determined by at slaughter on day 25 of pregnancy. gnrh treatment increased (p<0.05) embryonic weight,amniotic sac width and length and crown-rump length as compared with controls. results of present study demonstrated that treatment with gnrh may be luteotrophic and embryotrophic and thereby could improve litter size.