EFFECT OF BULL BIOSTIMULATION ON THE REPRODUCTIVE PERFORMANCE OF POSTPARTUM DAIRY COWS

Abstract

The present study was carried out to investigate the effect of bull bio-stimulation in Holstein Friesian dairy cows during postpartum period to improve their reproductive performance & reduce the calving interval. For this, a 21 days long study was conducted in the intensively reared Military Farm Chattogram at Chattogram Cantonment. A total of 22 postpartum cows (≥60 days postpartum) of same Body Condition Score (BCS), age, parity and cross breed cattle were selected from 490 non-pregnant cattle. Both groups were kept under similar feeding and management conditions. The cows were divided into two equal groups (n= 11 cows for each group); the first group was exposed to teaser bull and the second group was considered as a control. Blood samples were collected on day 0, 7, 14 and 21 days from both control and experimental groups by proper aseptic measures. Serum samples were separated by spinning the coagulated blood and the hormone extraction from blood samples were done by established protocol. The results revealed that ovarian activity resumed in 81.82% of experimental group compared to 27.27% in the control group. Mean progesterone (P4) levels were significantly higher (P<0.05) in the experimental group (10.3 ± 1.76 ng/ml) than in control (5.01 ± 0.78 ng/ml). First service intervals were shorter in bull-exposed cows (93.60 ± 4.16 days) compared to controls (102.71 ± 6.31 days). Days open were reduced in the experimental group (110.33 ± 11.48 days) versus control (134.57 ± 10.01 days). Number of services per conception was lower (1.33 ± 0.16) in cows following exposure to bull than non-exposure to bull (1.85 ± 0.34). The difference between means was highly significant (P< 0.05). Conception rates were higher in bull-exposed cows (90.90%) compared to controls (63.63%). Endocrinological analysis showed lower FSH and LH levels in bull-exposed cows. The mean value of hematological parameters showed significantly higher (P<0.05) in case of ESR (1.07 ± 0.12) mm/hr, MCV (73.44 ± 3.54) fl, and MCH (18.29 ± 0.92)) pg in the experimental group than the control group where the mean values of ESR was (0.76±0.07) mm/hr, MCV (64.64 ± 2.41)fl and MCH (15.69 ± 0.65) pg. In case of mean value of PCV, Hb, TEC, TLC, lymphocytes, monocytes, neutrophils, and MCHC showed no significant differences. Biochemical analysis indicated significant variations in total protein, globulin, and triglycerides, while plasma uric acid, BUN, and cholesterol levels showed no differences between groups. These findings demonstrate that bull bio-stimulation significantly improves reproductive performance and reduces calving intervals in postpartum anoestrous dairy cows under intensive management systems.