Parity and number of repeated doe-litter-separation treatments affect differently the reproductive performances of lactating does
Using data from three different experiments, the effects of oestrus synchronisation by doe-litter separation (DLS), applied 48 hours before artificial insemination from day 9 to day 11 post partum, on productive performance of free nursing rabbit does and their litters in relation to parity and number of successive DLS treatments were evaluated. lnitially, 200 New Zealand White does of different parity were homogeneously and definitively distributed in two groups (DLS and Control). On the whole, DLS improved fertility (+23.9%, P≤0.001), but reduced the growth of young rabbits from day 9 to weaning (-1.7 g/d, P≤0.01) and their weaning weight (-38 g, P≤0.01) at day 35. DLS also increased by 19.2%, 32.5% and 35.0% (P≤0.01) the fertility rate of does from parity 1 to 3, respectively, but was ineffective on does of parity ≥ 4. When DLS was repeatedly applied to does with more than 3 parity, fertility progressively dropped and, after the first still successful application, it was similar to that of controls. The results suggested that the effect of DLS on fertility of does and growth of suckling rabbit could depend on number of successive treatments rather than on parity. The hypothesis that several DLS treatments could induce a condition of behavioural/psychological and/or physiological adaptation, depressing both fertility and milk yield thereafter, while tempting, remains to be tested.
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