Efficacy of prostaglandin F2a and its analogs in enhancing reproductive efficiency of doe rabbits
The efficacy of prostaglandin F2a. (PGF2a.) and two analogs for inducing parturition in does to increase long-term rabbitry efficiency was studied. For the two-year trial, 40 single doe cages were used as experimental units. There were four treatments - does injected on day 29 of gestation with 5 mg PGF2a. 35 µg fenprostalene, 35 µg cloprostenol, or 1 mi saline as a control. Attempts to remate does began at 7 days post partum and were continuad daily until the doe accepted service. Ali does housed in a particular cage during the trial received the same treatment. The model included the fixed main effects of treatment, year, and season, with doe within treatment and residual error as random effects. The linear effect of parity was included as a covariate for those traits where it was significant (number of kits weaned and nest score). Doe repeatability accounted for significant varlation in litter birth weight (16.9±5.1 %), total kits born per litter (22.5±5.1%), kits born live per litter (19.5±5.0%), nest score (24.4±5.2%), and kits weaned per litter (14.6±4.8%). The 31.9±0.1 d gestation seen in the Jul-Sep season was graatar (P<0.05) than tha other saasons (31.2±0.1 to 31.6±0.1 d). Litter birth weight was greater (P<0.05) in Jan-Mar (338±19 g) than in Jul-Sep. (279±19 g) and followed a pattern similar to the number of kits born. At 63.5 d, tha kindling interval in the Oct.-Dec. period was longar than the othar seasons (P<0.01). During tha same period, the conception rate was lowar (P<0.01) as indicated by the higher number of servicas per litter (2.3±0.1 vs. 1.7±0.1, 1.6±0.1 and 1.6±0.1 for Jan.-Mar., Apr.-Jun. and Jul.-Sap., respectively.) Gestation length for saline treated does was 31.9±0.2 d vs. 31.4±0.4, 31.1±0.3 and 31.3±0.2 for the fenprostalene, cloprostenol and PGF2a. traated does, respactively (P<0.01). Fenprostalene and cloprostenol treated does kindled 7.3±0.5 and 7.2±0.5 kits per litter while PGF2a. treated does had only 5.8±0.5 kits per litter (P<0.01). Fenprostalene treatad does had larger (P<0.05) litters born live (6.0±0.5) than PGF2a. treated does (4.8±0.5). At 330±21 g, the litter birth weight of salina treatad does was greater than PGF2a. treated does (285±20) (P<0.05). Treatment had no effect on the quality of the nest constructed and little effect on subsequent reproductiva performance, although the fenprostalene treated does showad the least degrae of lordosis (P<0.05). Treatment with PGF2a. and the two analogs did not significantly shorten the kindling interval nor affect the number of services requirad for each litter. There were no differences among long-term responses to PGF2a. and its synthetic analogs nor any effect on conception rate. However, the differences in litter size born and born aliva indicate sorne differences may exist. Using our procedures, and breeding by natural service, routine use of prostaglandins or prostaglandin analogs did not improve reproductive efficiency in maat rabbits.
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