Journal of Animal Science, Vol 71, Issue 6 1552-1560, Copyright © 1993 by American Society of Animal Science

JOURNAL ARTICLE

Influence of porcine somatotropin on endocrine and histological variables in gilts

C. J. Andres, M. L. Green, J. A. Clapper, T. R. Cline, M. A. Diekman and P. J. Thomford
Department of Animal Science, Purdue University, West Lafayette, IN 47907.

Thirty-six crossbred gilts (71.7 +/- .9 kg and 140.1 +/- .9 d) were assigned to one of three doses (0, 35, or 70 micrograms.kg BW-1 x d-1) of recombinant porcine somatotropin (rpST). The doses of rpST were adjusted weekly, and i.m. injections continued until d 50. Gilts were pen fed (six gilts/pen) a 17% CP corn-soybean diet (1.2% lysine and 3.2 Mcal of ME/kg). At d 50, feed intake, feed:gain ratios (P = .02), and blood urea nitrogen were decreased (P < .001) by increasing rpST doses, whereas ADG was increased (P = .04) by increasing rpST doses. Injections of rpST did not affect (P > .05) conception rate, age, or weight at puberty. Numbers of blastocysts or corpora lutea observed at d 10.4 +/- 1.5 of gestation (42.2 d after final rpST injection) were unaffected (P > .05) by rpST treatment. Anterior and posterior pituitary weights were increased (P < or = .003) linearly with rpST dose. However, liver, adrenal, and heart weights were unaffected (P > .05) by rpST. After a withdrawal period of 42.2 +/- 2.0 d, rpST increased (P < or = .02) the estimated percentage of lean by 5.8% and longissimus muscle area by 10.4%. Eighteen hours before the initial rpST injection (d 0), 10 gilts per rpST dose were catheterized. Catheterizations were repeated on d 40. The rpST or diluent was given i.m. in the extensor muscle of the neck 1 h after initiation of blood collection. Adrenocorticotropic hormone (1.4 IU/kg BW) was administered through the catheter 3 h after initiation of blood collection.(ABSTRACT TRUNCATED AT 250 WORDS)