Metabolism and reproductive function during the postpartum period in first-calf cows when introducing the placenta extract

Most reproductive disorders in dairy cows are associated with postpartum metabolic state. One approach to normalizing the reproductive function is to use biostimulators, which have a modulating effect on the immune, metabolic, and endocrine systems. The aim of the present research was to study the action of the cattle placenta extract on the metabolic adaptation and reproductive system functioning during the postpartum period in first-calf cows. We have conducted for the first time monitoring of indicators of metabolism and the steroidogenic ovarian activity in first-calf cows, treated with the placenta extract, during the transition period and two months after calving and also assessed the reproduction indices. The raw material for the preparation was placenta separated within 4-6 hours after calving. The extract was isolated from placenta according to the procedure, described earlier (M.V. Varenikov et al., 2010), with the use of some modifications. Effects of the extract were evaluated in first-calf cows of the Black Pied breed (Bos taurus taurus) on the basis of ZAO PZ «Barybino» (Domodedovo Region, Moscow Province) in 2015-2016. Seven to fourteen days prior to calving and on the day of calving, cows of the group I (control, n = 8) received the saline, and cows of the group II (experiment, n = 11) received 20 ml of the placenta extract. Before the treatment and on days 3 to 5, 20 to 25 and 50 to 60 after calving, the animal blood was taken for biochemical analysis and enzyme immunoassay. In serum samples, the concentration of total protein and its fractions, urea, bilirubin, cholesterol, calcium, and phosphorus, the activity of aspartate aminotransferase (AST, EC 2.6.1.1) and alanine aminotransferase (ALT, EC 2.6.1.2), and the content of progesterone and estradiol-17β were measured. Twelve months after calving, based on the analysis of zootechnical and pedigree records, the reproduction indices (the pregnancy rate, calving to conception interval, and service per conception rate) and the 305 - day milk yield were determined. A rise (p < 0,001) in the blood content of total protein (by 24.9 %) and its globulin fraction (by 51.8 %) was observed on days 20 to 25 after calving only in animals of the group II. The cholesterol concentration in the blood of these cows remained unchanged, whereas it was reduced by 33 % (p < 0.05) in control cows from days 3-5 to days 20-25 after calving. During the studied period, an increase in the serum activity of ALT was more pronounced in cows of the group II, while a raise in the activity of AST was considerable only in control animals. On days 20-25, the progesterone concentration in the blood of experimental cows was 57.7 % lower than in the control group (p < 0.05). However, 50-60 days after calving, the level of blood progesterone in experimental animals rose sharply and was four times higher than in control ones (p < 0.01). The treatment of cows also resulted in a reduction in the calving to conception interval from 123.5±10.5 to 95.1±5.8 days (p < 0.05). Thus, the injection of the cattle placenta extract to first-calf cows exerts modulating effects on metabolism, primarily lipid metabolism, as well enhances the luteal activity of ovaries during the postpartum period. Normalization of the metabolic and hormonal status of cows is, obviously, related to a rise in the reproductive ability of the animals and leads to a reduction in the subsequent calving to conception interval.