EFFECTS OF 6-N-PROPYL-2-THIOURACIL ON GROWTH, HORMONAL PROFILES, CARCASS AND REPRODUCTIVE TRAITS OF BOARS

Neonatal 6-N-propyl-2-thiouracil (PTU)-induced hypothyroidism reduces body weight but increases testicular size in adult male rodents. The o bjective of this study was to determine the effect of prepubertal PTU treatment on boars. For Experiment I, boars (n = 28) were randomly all otted to eight pens. Each pen received one of four PTU doses (0, 0.01, 0.03 and 0.1% in a basal diet) between 28 and 56 days of age (DOA). D ue to a lack of difference among three PTU treatments, PTU-treated boa rs were pooled. Boars treated with PTU had lower (P < 0.05) ADG during treatment, lighter (P < 0.05) BW after 56 DOA and less (P < 0.05) dev eloped epi didymides at 154 DOA. For Experiment II, boars (n = 19) wer e randomly allotted to six pens. Each pen received one of three PTU tr eatments orally as: control (carrier), PTU-I (0.002% BW of PTU daily b etween 7 and 70 DOA), or PTU-II (0.002% BW of PTU daily between 28 and 91 DOA). During treatment, PTU-treated boars had lower (P<0.05) serum T-4 levels, rectal temperature, feed intake and ADG. Boars treated wi th PTU had lower (P < 0.05) BW between 63 and 154 DOA but higher (P < 0.05) gain/feed between 105 and 133 DOA. Boars treated with PTU had le ss (P < 0.05) developed epididymides and sperm count per gram testis a t 238 DOA. These results suggest that prepubertal PTU-induced hypothyr oidism had significant effects on growth, hormonal profiles, and repro ductive traits of boars; however, it does not appear to be an effectiv e method for increasing testis size and sperm production of commercial boars. (C) 1998 Elsevier Science B.V.