Effects of Norprolac-Induced Prolactin Suppression on Plasma Hormone Levels and Semen Quality of Karan Fries Crossbred Bulls during Summer
Smrutirekha Mallick *
Dairy Cattle Physiology Division, ICAR-National Dairy Research Institute, Karnal-132001, Haryana, India and ICAR- National Institute on Foot and Mouth Disease, Arugul, Bhubaneswar-752050, Odisha, India.
Anjali Aggarwal
Dairy Cattle Physiology Division, ICAR-National Dairy Research Institute, Karnal-132001, Haryana, India.
B. S. Prakash
Dairy Cattle Physiology Division, ICAR-National Dairy Research Institute, Karnal-132001, Haryana, India.
B. S. Bharath Kumar
Dairy Cattle Physiology Division, ICAR-National Dairy Research Institute, Karnal-132001, Haryana, India.
Rubina Kumari Baithalu
Animal Reproduction, Gynaecology and Obstetrics, ICAR-National Dairy Research Institute, Karnal-132001, Haryana, India.
*Author to whom correspondence should be addressed.
Abstract
High peripheral prolactin levels can adversely affect male fertility. A study was undertaken to investigate the effects of norprolac-induced prolactin suppression on plasma prolactin and testosterone concentrations and semen quality of Karan Fries (Holstein Friesian × Tharparkar) bulls. To standardize the dose of norprolac in bull three doses i.e. 2.5 mg, 5.0 mg and 10.0 mg intramuscular (i.m.) per animal were attempted. The dose of 5.0 mg per animal was found suitable to suppress the peripheral prolactin concentration. Norprolac treatment @ 5 mg i.m. on alternate day for 10 days in summer effectively (p<0.05) reduced peripheral prolactin concentration without altering testosterone level significantly (p>0.05). Semen volume, sperm viability, sperm concentration, HOS-reactive spermatozoa and acrosome-intact spermatozoa% did not differ (p>0.05) between the treated (n=4) and control bulls (n=4) estimated fortnightly over a period of 60 days. It is concluded that norprolac-induced prolactin suppression during summer might not affect plasma testosterone concentration and semen quality in crossbred bulls. Our study provides the first evidence of norprolac treatment in bulls. However, due to small sample size the results require further validation in larger herd to underscore the physiological implications of prolactin suppression on bull fertility.
Keywords: Bull, summer, prolactin, norprolac, testosterone, semen quality