Reproductive and biochemical parameters were studied at parturition in multiparous single-carrying Holstein cows. These were compared in animals with (n=14) and without (n=40) a
retained placenta and then according to 2 prepartum diets (corn silage/concentrate, n=44; grass silage/concentrate, n=10) in cows with and without
retained placentas. Cows with
retained placentas had a 4-day shorter gestation period and gave birth to 5 kg-lighter calves than cows without
retained placentas. Furthermore, their plasma
PGFM -PgF2alpha main metabolite- (3325 vs 5675 pg/ml; P<0.01) and
glucose (79.2 vs 95.2 mg/100ml; P<0.05) levels were lower and their
protein concentration was higher (85.7 vs 76.5 g/l; P<0.05) than those of cows without
retained placentas.
Retained placenta incidence in cows fed grass-silage was higher than in cows fed corn-silage (60% vs 18.2%; P<0.05). Cows with
retained placentas and fed corn silage had shorter gestation lengths, gave birth to lighter calves, and had less circulating
glucose at calving (77.6 vs 96.5 mg/100ml; P<0.05) than cows without
retained placentas and fed the same forage. Cows with
retained placentas and fed grass silage had less
PGFM (2172 vs 4530 pg/ml; P<0.05) than cows without
retained placentas and fed the same forage. Calving number, sex ratio and preceeding milk yield were not different between the two groups of cows whatever their prepartum diet. In the dairy cow,
retained placenta could be due to a
PgF2alpha or an energy deficiency at calving. Roles of the dietary
polyunsaturated fatty acids toward the Pg synthesis and of the energy supply before calving in relation to
retained placenta are discussed here.