Abstract:
The aim of the present study was to investigate the evolution rate and its relationship with number of total pigs born in purebred gilts under tropical climate condition. This study was conducted at two swine breeding herds (A and B) in the northeastern part of Thailand from April to December 2001. The sources of swine genetic material originate from northwestern Europe. Gilts were mated (AI) on the second or later observed estrus. One hundred and twenty-seven gilts, 25 Landrace and 24 Yorkshire from herd A, and 42 Landrace and 35 Yorkshire from herd B were used. Gilts were examined once by laparoscopy under general anesthesia between days 8 to 15 after mating. The ovaries were examined and the pathological findings were recorded. The numberof corpora lutea was counted, and was assumed to equal the ovulation rate. Subsequent of variance results and farrowing data were redorded. The data was analyzed with analysis of variance. Single or double unilateral cysts and par-ovarian cyst did not affect mating results. Landrace gilts were significantly younger at first mating than Yorkshire gilts (244 vs. 249 d, P<0.05>. At first mating, Yorkshire had significantly higher ovulation rate compare to Landrace (15.3 vs 13.8, P<0.001). No difference in number of total piglets born between the two breeds, but Yorkshire had significantly higher ovum wastage than Landrace. The total prenatal loss from ovulation to farrowing is 31.0% and 37.5% in Landrace and Yorkshire, respectively. Both the low ovulation rate and the high prenatal loss were contributed in the low litter size in gilts raised under tropical climate condition.