Abstract
Relationship between litter size and farrowing conditions was examined using 110 litters from crossbred sows. The time required for piglet expulsion was found to be 195±150 minutes, showing large differences among the individuals. Therefore, by excluding the sows with an interval of piglet expulsions over 60 minutes, the relationship of the inter-litter interval and the time for farrowing the entire litter to the litter size was investigated, by which the inter-litter interval and the time needed for expulsion of all piglets turned out to be 10.2 minutes and 191.4 minutes, respectively, for the litter size of 14, 12.4 minutes and 157.1 minutes, respectively, for that of 10, and 20.1 minutes and 143.2 minutes, respectively, for that of 6. In every pair of the litter sizes, a significant difference (p<0.01) was noted.
The relationship between the litter size and conditions of newborn piglets was then examined on the basis of the farrowing records of 1, 348 litters. The parity of the sows was 3.62±2.55 and the litter size was 11.13±1.84. With regard to the rate of expulsion of abnormal piglets, immature, stillborn and mummified piglets were 5.18, 5.81 and 1.28%, respectively. A negative correlation was found out (r=-0.793) between the litter size and the ratio of expulsion of normal piglets, while with regard to the relationship between the litter size and the ratio of abnormal piglets, no significant tendency was found in mummified piglets, but significant correlations were found (p<0.01) in the cases of immature piglets (r=0.807) and stillborn piglets (r=0.794).
