Estrone Sulfate Concentrations, Calf Birth Weight and Viability, and Placental Weight and Expulsion in Dairy Cattle with Different Gestation Length

摘要

Fifty-four pregnant Holstein-Friesian cattle were divided into 3 groups according to their gestation length (A = 274-280 days ; B = 281-285 ; C = 286-290). Changes in plasma estrone sulfate (E_1 S) concentrations during pregnancy, calf birth weight, calf viability, placental weight and placental expulsion were compared among the 3 groups. Differences in E_1 S concentrations among these groups became evident after day 271 of pregnancy and E_1S levels in groups A and C were lower than in group B. In male calves, birth weights in group A were significantly lower than those in groups B (P<0.01) and C (P<0.05). Likewise, in female calves, birth weights in group A were significantly lower than those in group C (P<0.05). There were no significant differences in birth weights of both male and female calves between groups B and C. Incidences of weak calves and retained placenta were lower in group B (11.5%) than in groups A (25.0%) and C (43.8%). Cotyledonary weights in group B tended to be higher than in groups A and C, and there were significant differences between groups A and B for dams with male neonates and for total dams, and between groups B and C for total dams. Thus, gestation length below the herd average is associated with low calf birth weight, low cotyledonary weight and low plasma E_1S concentrations, while gestation length above the herd average is not necessarily associated with high calf birth weight, high cotyledonary weight or high plasma E_1S concentrations. The longer gestation period, however, resulted in higher incidence of neonatal weakness and retained placenta. These results indicate that the feto-placental growth slows or ceases when a gestation period extends over a normal period and as a consequence prevalence of retained placenta and weak calves increases in cows with longer gestation period.