Factors affecting gestation length in goats and the effect of gestation period on kid survival

Data on 1468 pregnancies and 2356 newborn goat kids of six genetic groups u nder intensive management were utilized to determine some genetic and non-g enetic factors affecting gestation length, and to assess the relationship b etween gestation length and survival of kids to 25 days of age. The study r evealed significant (P < 0.01) effect of breed of dam, litter weight, breed ing season and parity on gestation length. Number of kids born and sex of k ids were not a significant source of variation affecting this trait. Granad ina goats had the shortest gestation(149.0+/-0.31 days), whereas Toggenburg (151.7+/-0.28 days) and Alpine (151.4+/-0.46 days) had the longest. Litter weight and gestation period were related curvilinearly in summer and linea rly in autumn. Gestation of goats bred in summer was 1 day longer (P < 0.01 ) than those mated in the autumn. There was a progressive reduction of gest ation length as parity increased (151.3 +/- 0.24, 150.6 +/- 0.17 and 149.9 +/- 0.39 days for 1, 2-6 and >7 kiddings, respectively). The mean survival rate of kids gestated < 148 days and 148-152 days were 78 +/- 2 and 87 +/- 1, respectively, and these were significantly lower (P < 0.05) than the sur vival rate of kids gestated 152-156 days and > 156 days (94+/-1 and 95+/-2) . In conclusion, prolonged gestation (152-160 days) in goats was beneficial because it resulted in heavier litters at birth and higher viability of ne onatal kids.