Interactions between metabolic status, pre-breeding protein supplementation, uterine pH, and embrionic mortality in ewes: preliminary observations.

The effect of prebreeding short-term protein supplementation level (PL) and body condition (BC) on fertility rate (FERT,%), uterine pH and embryonic mortality (EMORT,%) in sheep, was evaluated. Multiparous Rambouillet ewes at low BC (LC; n = 6, 62.7+/-1.7 kg) or high BC (HC; n = 6, 71.9 +/-1.7 kg), received, within BC, one of two levels of ruminally undegradable protein: low (LP, 14 g/ewe per day) and high (HP, 30 g/ewe per day). Once the animals were euthanized, corpus luteum number (CLN), as an indicator of ovulation rate, was registered and uterine horns were irrigated to recover embryonic tissue plus associated membranes as well as to measure uterine pH (UpH). While EMORT- 1 considered a nonadjusted relationship between the number of embryos and CLN, EMORT-2 considered an analysis of covariance using CLN as the covariate. The HP-supplemented ewes had the lowest FERT (p = 0.06; 100% vs 50%) and the highest EMORT (EMORT-1, 16.6% vs 53.8%, p = 0.08; EMORT-2, 52.0% vs 14.5%, p = 0.07) when compared to the LP-supplemented ewes. Neither BC nor PL affected CLN, CL weight or P4 release (p > 0.10). While the lowest UpH (p = 0.04) was observed in the HP-supplemented ewes, this group also showed the lowest fertility and the highest embryonic mortality.