Analysis of stillbirth in different lines of pig

In order to examine genetic influences on stillbirth in the pig, records of 7817 litters, originating from two purebred dam lines (D1 and D2), one pur ebred sire line (S), and one two-way cross (D12), were analyzed. For each l itter, number of stillbirths, parity of the dam, gestation length (GL), tot al number of piglets born (TNB), average birth weight of the litter (ABW), variation in birth weight within the litter (VBW) and preweaning mortality rate (PWM) were recorded. After adjustment for ABW, there were no significa nt line differences in both average birth weight of stillborn and live-burn piglets. Number of stillbirths per litter did not differ between lines, ne ither before nor after adjustment for GL, TNB, ABW and VBW, but was signifi cantly influenced by GL, TNB and ABW, and not by VBW. Number of stillborn p iglets per litter increased with decreasing GL, increasing TNB and decreasi ng ABW. On average, number of stillborn piglets increased between the secon d and the fifth parity. After adjustment for number of live-born piglets pe r litter, there was a significant positive relationship between number of s tillborn piglets per litter and number of live-born piglets that died befor e weaning. In conclusion, no line differences in stillbirth were found, but significant line differences in the relation of stillbirth with GL, TNB an d ABW indicate a small underlying genetic influence. The positive relations hip of number of stillbirths with preweaning mortality of live-borns indica tes an overall lower viability of litters in which stillbirths occur. (C) 1 999 Elsevier Science B.V. All rights reserved.