Effects of Bromocriptine and Photoperiod on Puberty in Gilts

• Main Authors: Lii, Wei-Sheng, 李維生
• Other Authors: Shyi-Kuen Yang
• Format: Others
• Language: zh-TW
• Published: 1997
• Online Access: http://ndltd.ncl.edu.tw/handle/42762497511852467445

碩士 === 東海大學 === 畜產學研究所 === 85 === Two experiments were conducted to determine effects of bromocriptine ( a dopaminergic agonist ) injection and photoperiod regimen on puberty in gilts. In Exp. I., 36 crossbred gilts【 Yorkshire×Landrace ( YL ) and Duroc× Yorkshire×Landrace ( DYL ) 】born on February 10-12,1995, were randomly allotted into control ( C? K, bromocriptine ( BRO ) or melatonin ( MEL ) group on 60 d of age. Gilts in CTL group were exposed to natural photoperiod. Those in BRO group were exposed to natural photoperiod, but were injected intramuscularly with bromocriptine mesilate ( 0.5 mg/ Kg ) on 165,195 and 225 d of age. Those in MEL group were administered melatonin orally at dose of 3 mg/ day from 90 d of age to the end of this Exp. All gilts were collected blood samples twice a week from 165 d of age for the determination of progesterone by radioimmunoassay to evaluate whether the individual gilt ovulated before first estrus. The proportions of gilts attaining puberty within 245 d were 7/12, 4/12 and 3/12 for CTL, BRO and MEL groups, respectively, without significant difference among treatments. The proportion of gilts attaining puberty in MEL group tended to be lower than that in CTL group ( p=0.098 ). Ages at puberty and body weights at puberty were not different among treatments. In Exp. II, 36 crossbred gilts born on August 27-28, 1995, were randomly allotted into CTL, BRO or long-light ( LL ) group on 65 d of age. Treatments for CTL and BRO groups were the same as described in Exp. I. Gilts in LL group were exposed to 16 h photoperiod from 120 d of age to the end of this Exp. The proportions of attaining puberty were not different among treatments ( 6/12, 6/12 and 5/12, for CTL, BRO and LL groups, respectively ). However, LL group ( 181.4±24.4d ) attained puberty earlier significantly than CTL group ( 216.2±12.4d ) ( p<0.05 ). Body weights at puberty were not different among treatments. It is concluded that the bromocriptine injection doesn*t influence the proportion and age of puberty in gilts. Melatonin administration decreases the proportion of puberty in gilts during decreasing daylength, and longdays advances puberty in gilts during increasing daylength.