Effect of lowering blood cortisol level along with progesterone priming on intensifying the secondary symptoms of oestrus in Murrah buffaloes during the hot summer months

Abstract

The present study sought to intensify oestrus symptoms in heat‐stressed pre‐pubertal Murrah buffalo heifers. The first experiment aimed at lowering the blood cortisol level. Twenty pre‐pubertal buffalo heifers approximately 36–40 months of age were randomly allocated to four groups of five buffaloes. Group Gly received 100 ml glycerol orally for 8 days (day 0 is the start of treatments), group Gly‐E received intra‐muscular injections of 500 mg tocopherol (vitamin E activity) and 150 mg sodium selenite on alternate days (four treatments) in addition to treatments received by group Gly, group Gly‐E + B‐Ch received intra‐muscular injections of vitamin B‐complex and choline daily for 8 days in addition to the treatments received by group Gly‐E. The control group Co‐1 did not received any treatments. Blood cortisol and glucose level was measured on day 7 post‐treatment. The second experiment sought to test the effect of lowering the blood cortisol level and progesterone priming on the intensity of oestrus symptoms in heat‐stressed pre‐pubertal buffalo heifers. Eighty buffaloes were allocated into four groups of twenty buffaloes. P4 group received intra‐vaginal progesterone CIDR for 5 days (day 0 is the day of start of treatment). Gly‐E group received the same treatment as in the first experiment for 7 days (day 0–6) and P4 + Gly‐E received the combination of P4 and Gly‐E groups. The control group Co‐2 did not receive any treatments; however, on day 6, all groups received intra‐muscular injection of 2 mg estradiol benzoate. The buffaloes were graded for oestrus symptoms on the basis of mucus discharge (A‐scanty and B‐copious), vulvar redness (slightly pink and moist‐A and deep red and moist‐B), ferning (nil or poor‐A and good with arborization‐B) and cellularity of cervical mucus (Type A goblet cells with round nucleus and abundant cytoplasm and Type B goblet cells with cylindrical nucleus and scanty cytoplasm). The blood glucose level (mean ± SEM) of Gly group on day 7 of treatment in experiment 1 was 58.3 ± 0.4 mg/dl that was significantly greater than Co‐1 (52.4 ± 0.4 mg/dl), Gly‐E (53.5 ± 0.8 mg/dl) and Gly‐E + B‐Ch (52.7 ± 0.6 mg/dl) groups; however, the difference was found to be non‐significant among Co‐1, Gly‐E and Gly‐E + B‐Ch groups. The cortisol level (mean ± SEM) on day 7 in groups Gly (11.4 ± 0.6 ng/ml), Gly‐E (8.1 ± 0.5 ng/ml) and Gly‐E + B‐Ch (7.5 ± 0.4 ng/ml) was significantly lower than groups Co‐1 (15.5 ± 0.3 ng/ml), though the difference between groups Gly‐E and Gly‐E + B‐Ch was non‐significant and the level in group Gly‐E significantly lower than Gly. Thus, the combination of vitamin E and selenium along with glycerol had the best effect in the reduction of blood cortisol level in heat‐stressed buffaloes. In the second experiment the blood estradiol level on day 7 in all groups was around 40 pg/ml. Cortisol reduction (group Gly‐E) improved oestrus symptoms (mucus discharge and ferning) compared to control, but when compared to group P4 showed non‐significant difference with respect to mucus...