The effect of orally administered thyrotropin-releasing hormone on growth and carcass characteristics of seven- to ten-week-old broilers.
In contrast to some earlier studies with young broiler chickens, several recent studies have shown growth responses to exogenous growth hormone (GH) administration in broiler chickens of advanced age (Vasilatos-Younken et al., 1988; Scanes et al., 1990). It was therefore of interest to determine whether intermittent feeding of thyrotropin-releasing hormone (TRH), a known GH secretagogue, would elevate plasma GH of 7- to 10-wk-old broilers and alter their growth characteristics. Four replicate pens of 15 males and four pens of 15 females 7 to 10 wk of age were given access to feed containing 3.5 mg/kg of TRH for four 2-h periods each 24 h with 4-h periods of feed removal between. Control groups either were fed the basal ration on the same intermittent schedule or had continuous access to it. Growth hormone concentrations, measured 45 to 75 min after the start of TRH feeding periods, were significantly elevated in males on the 1st day of the experiment and after 7, 14, and 21 days when they were 7, 8, 9, and 10 wk of age, respectively. Concentrations in females were elevated on the 1st day of treatment, but not thereafter. Treatment with TRH had no effect on BW or relative gain of males at any time. It significantly increased relative gain of females during the 1st wk, but not thereafter. There were no treatment effects on 10-wk shank length, Pectoralis major weight, Gastrocnemius weight, or liver weight in either sex, but the percentage fat pad of males fed TRH was lower than that of controls fed intermittently.
Mitchell
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RD
Department of Poultry Science, University of Georgia, Athens 30602-2772.
Burke
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WH
D000284:Administration, Oral; D000818:Animals; D001835:Body Weight / Q000187:drug effects*; D002645:Chickens / Q000254:growth & development*; D005260:Female; D013006:Growth Hormone / Q000097:blood* / Q000187:drug effects; D008297:Male; D013973:Thyrotropin-Releasing Hormone / Q000008:administration & dosage / Q000494:pharmacology*
D013973:Thyrotropin-Releasing Hormone; D013006:Growth Hormone