Endocrine and pregnancy protein changes during periparturient period with correlation of stillbirth in dairy cow

Abstract

Over the last fifty years a decline in fertility in high yielding Holstein dairy cattle is observed as well as a steady incline of the stillbirth rates during the last years is detectable, especially in Holstein-Friesian heifers. Both dystocia and stillbirth can be affected by several factors such as birth weight of the calf, gender of the calf, parity, age and breed of the dam, season of calving, gestational/calving length, and furthermore number of calves. Infections (e.g. BVD), insufficient placenta development, metabolic disorders of the cow, and congenital malformations of the calf belong to causes of stillbirth which are not related to calving difficulties. This present study focus primarily on analysing the periparturient levels of progesterone (P4), estradiol (E2) and pregnancy associated glycoprotein (PAG) to investigate the possible effects of hormonal and pregnancy protein disturbances on the incidence of stillbirth in Holstein- Friesian dairy cows. For the performance 173 multiparous Holstein-Friesian dairy cows were sampled on a Hungarian dairy farm three times during the periparturient period. In 2006 blood was collected at drying-off, three weeks before expected calving and within one hour after calving, respectively while in 2007 the cows were only sampled two times i.e. 3 weeks prior to expected calving and within 1 h after calving. Regarding the factor stillbirth the cows were grouped into two groups, i.e. control group (Group 1) and stillbirth group (Group 2). Dams without stillbirth (n=165) belong to the first, those undergoing stillbirth (n=8) to the second group. P4, E2 and PAG parameters were measured by RIA. A generalised linear model with binomial error distribution and logit link function (multivariate logistic regression) has been used to determine which of the parameters were the best predictor of the presence or absence of stillbirth at a given time. R.2.7.2 Statistical Software was utilized for all analysis. P < 0.05 was established as significance level. When P was between 0.05 and 0.10 an effect was considered a trend. The outcome of the study is a stillbirth rate of 4% in the year 2006 and 5.4% in 2007 resulting to an overall prevalence of stillbirth of 4.6%. Seven out of eight stillborn calves were bulls - 24 - (89%), but this difference was not significant. The presence or absence of stillbirth were not affected neither by the weight of the calves, the BCS nor the number of calving assistants and also no significant difference between the two groups regarding the gestation length or the number of parity were observed (P > 0.100 in all cases). At two months as well as three weeks before expected calving no significant differences concerning the examined hormone and pregnancy protein parameters were detected. However in case of P4, measured within one our after calving, mean values were 2.4 nmol/l in the control group whereas the stillbirth group reached mean levels of 4.7 nmol/l. Thus, the difference was significant (P < 0.001, OR = 3.06). As a result of the elevated progesterone levels in stillbirth cows the P4/E2 ratio was significantly higher as in the control group i.e. 0.014 and 0.005 respectively (P < 0.003, OR = 1.60). Changes in P4 as well as the P4/E2 ratio may be considered as a reason for stillbirth in Holstein-Friesian dairy cows and may be used for stillbirth prediction. However, for the future more examinations and studies have to be performed to confirm these results.