Serum gonadotropins after gonadotropin-releasing hormone injection in bulls subjected to spacial restriction.
Response patterns of luteinizing hormone, follicle-stimulating hormone, and testosterone after injection of gonadotropin-releasing hormone were investigated in bulls grouped by weight (250 to 459 kg body weight) and confined five per pen in 9.2 or 6.4 m2 space per bull in two replicates. Blood samples were collected for 1 h prior to injection of 100 micrograms gonadotropin releasing hormone and 5 h after injection at 15-min intervals. Overall mean luteinizing hormone concentrations were not affected by spacial restriction or replicate. Interaction of treatment by time revealed that luteinizing hormone response curves were not similar. Restricted bulls had a higher response of luteinizing hormone to gonadotropin-releasing hormone. Follicle-stimulating hormone increased in all groups within 15 min and peaked at 219.4 ng/ml at 45 min. Both gonadotropin responses returned to preinjection concentrations by 4 h. Testosterone was affected by treatment, replicate, and time of sampling. Testosterone was higher in restricted bulls and higher in replicate 2. Mean testosterone peak following gonadotropin-releasing hormone was 3.86 ng/ml and occurred between 105 and 120 min which was approximately 90 min after the gonadotropin peaks. It appears that hormone responses to gonadotropin-releasing hormone were not depressed by spacial restriction, and additional spacial restriction of young bulls could be used commercially.
D000367:Age Factors; D000818:Animals; D001835:Body Weight; D002417:Cattle / Q000502:physiology*; D003441:Crowding; D005640:Follicle Stimulating Hormone / Q000097:blood*; D006799:Housing, Animal; D007986:Luteinizing Hormone / Q000097:blood*; D008297:Male; D010906:Pituitary Hormone-Releasing Hormones / Q000494:pharmacology*; D013739:Testosterone / Q000097:blood
D010906:Pituitary Hormone-Releasing Hormones; D013739:Testosterone; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone