Abstract :
The demand for meat goats in the USA is increasing, particularly in the Christmas and Easter holiday season. Manipulation
for spring breeding in goats could increase productivity of flocks, enhance profitability and elevate the supply of meat goats at
a time when demand is high. Four Spanish bucks were conditioned for 2 months to long day photoperiod (16 h light:8 h dark),
followed by a single melatonin implant (18 mg, 6-week release period). Eighty Spanish female goats (15 does and 65 doelings)
were allotted to five treatments: control (C); melatonin implant (MI); melatonin and bromocryptine (225 mg, 60-days release
period) implants (MIB); oral administration of melatonin (MO, 3mg per day); and oral administration of melatonin and the
bromocryptine implant (MOB). After the fifth week of melatonin administration, does were randomized and bred in three
single-sire groups for a 35-days period. Melatonin administration elevated serum melatonin level (P < 0.05 ) compared with
C in weeks 5–7. In response, prolactin concentration was suppressed by melatonin in weeks 2, 4–6 (P < 0.05 ). There were 14,
14, 13, 13 and 15 does bred; 5, 10, 13, 12 and 10 does pregnant at ultrasonography diagnosis; 5, 10, 11, 8 and 8 does kidding; 8,
18, 16, 15 and 19 kids born; and 8, 17, 15, 13 and 18 kids weaned for C, MI,MIB, MO and MOB, respectively. There were no
differences among treatments in number of does bred, whereas melatonin-treated groups had greater numbers of does pregnant
and kidding and a greater number of kids born (P < 0.05 ). For the spring breeding (overall), does in estrus, conception rate,
does kidding, kids born per doe bred, multiple litter rate and number of kids weaned per doe kidding were 86, 63 85, 67, 179
and 169%, respectively, whereas, slightly greater values were noted for fall breeding (92, 82, 96, 78, 198 and 187, respectively).
These results suggest that an accelerated breeding program for goats, with scheduled breeding in the spring and fall, could be
profitable by elevating total meat goat production and also through an increase in the supply when prices are relatively high.
© 2003 Elsevier Science B.V. All rights reserved.
Keywords :
melatonin , Prolactin , Spanish goat , birth weight , Breeding
