Growth and carcass characteristics and serum growth hormone, prolactin and insulin profiles in Debouillet lambs treated with ovine growth hormone and(or) zeranol.

Sixteen Debouillet wether lambs (approximately 3 mo old) were placed indoors in 1.5- x 3-m pens (14 h light:10 h dark) 28 d after weaning. Lambs received no implant or a 12-mg zeranol implant on d-2 (eight lambs/group). Two days later (d 0), animals received either 0 or 2.5 mg ovine growth hormone (oGH, eight lambs/group) s.c. on alternate days for 42 d. Animals had ad libitum access to water, salt, mineral and a pelleted alfalfa diet (16% CP). After 42 d, lambs were slaughtered to evaluate carcass traits, organ weights and femur characteristics. Zeranol by oGH interactions were not detected (P greater than .20). Zeranol increased (P less than .05) BW, improved (P less than .05) feed:gain during the first 20 d and increased (P less than .10) feed intake during the last 22 d of the 42-d trial compared with controls. Carcass characteristics were not altered (P greater than .10) by 12 mg zeranol. Serum insulin and prolactin were elevated (P less than .05), but serum GH was not influenced by zeranol compared with controls. Exogenous oGH decreased feed intake (P less than .10) and improved feed:gain (P less than .05) during the initial 20 d compared with controls, but did not influence (P greater than .20) these variables during the last 22 d of the study. Carcass traits were not influenced (P greater than .10) by oGH. Exogenous ovine GH dramatically elevated (P less than .05) serum GH, but did not affect serum insulin or prolactin (P greater than .10).(ABSTRACT TRUNCATED AT 250 WORDS)