AGE AT PUBERTY, OVULATION RATE, UTERINE LENGTH, PRENATAL SURVIVAL ANDLITTER SIZE IN CHINESE MEISHAN AND YORKSHIRE FEMALES

Studies on the ovulation rate, prenatal survival and litter size of Ch inese Meishan pigs have given widely divergent results depending on th e extent of inbreeding of the animals, their original genetic diversit y, the age and parity, and the conditions of management. To obtain mea ningful results, it is necessary to characterize the population under study. The following report characterizes populations of Meishan and Y orkshire of a widely diverse background. First farrowing data were col lected on 21 Meishan and 20 Yorkshire gilts. Meishan gilts had 12.4 fu lly formed piglets and Yorkshire gilts had 7.4 fully formed piglets (P < 0.01). Meishan gilts averaged 1.86 mummified fetuses per litter vs 0.05 per Yorkshire litter (P < 0.01). Yorkshire piglets averaged 1.3 k g body weight at birth vs 0.9 kg for Meishan piglets (P < 0.01). At 47 days of second gestation, 19 Meishan and 12 Yorkshire sows averaged 2 2.7 and 16.3 corpora lutea (CL), respectively (P < 0.01). Uterine leng th and number of fetuses were not different (P > 0.40) in the two bree ds. Daily estrous detection of 50 Meishan and 34 Yorkshire gilts began at 60 and 120 days of age, respectively. Meishan gilts reached sexual maturity at 95 days of age, which was 105 days earlier than Yorkshire gilts (P < 0.01). Meishan gilts were in estrus nearly 1 day longer th an Yorkshire gilts at first, second and third estrus (P < 0.05). No di fferences in cycle length between breeds were detected for the first o r second estrous cycle (P > 0.60). Nineteen Meishan gilts were slaught ered at 51 days of gestation and their reproductive tracts were recove red. The mean number of dissected CL (17.0), number of fetuses (13.1), total uterine length (396 cm), spacing per fetus (29.9 cm), allantoic (124.9 ml) and amniotic (32.2 ml) volumes, crown-rump length (82.8 mm ), weight (35.4 g), sex, and direction of each fetus were determined. Chinese Meishan gilts reached puberty much earlier and were in estrus longer than Yorkshire gilts and Meishan sows had more CL than Yorkshir e sows.