Estimates of repeatability for reproductive traits in Large White sows

Abstract

The main aim of this paper was to analyze the effect of parity number on the litter size and other reproductive traits in Large White sows during successive farrowings to determine the repeatability estimates. The population used for the present study is from a pig farm managed by the Limited Liability Company (LLC) “Tavriys’ki svyni” located in Skadovsky district (Kherson region, Ukraine). The experimental materials used for this study consisted of 100 inds. of productive parent sows of the Large White breed. The estimation of reproductive performance was conducted for each animal included in this study. The total number of piglets born (TNB), number piglets born alive (NBA), number weaned piglets (NW), number of stillborn piglets (NSB) and frequency of stillborn piglets (FSB) per litter, number of piglets that died between birth and weaning (NPWM) and frequency of piglets that died between birth and weaning (FPWM) per litter were monitored in the first eight parities in the period of eleven years (2007–2017). For TNB, of the 28 correlations between different parities, 19 (i.e., 68 %) were statistically significant (P < 0.001…0.05). The correlation between TNB values at repeated farrowings was, as expected, positive and in most cases moderate, from 0.197 (between 1st and 4th parity) to 0.365 (between 6th and 7th parity). Highest significant correlation was determined between TNB values in four latest farrowings (5th–8th parities). For NBA, only 7 (i.e., 25 %) phenotypic correlations were statistically significant (P < 0.002…0.025) and varied from 0.230 (between 1st and 8th parity) to 0.303 (between 6th and 7th parity). Finally, for NW only 5 (i.e., 18 %) phenotypic correlations were statistically significant (P < 0.005…0.05) and varied from 0.200 (between 3th and 7th parity) to 0.281 (between 4th and 6th parity). Thus, while observing the phenotypic correlations for the same studied traits between different parities (P1–P8), it can be seen that the correlations for TNB are positive and stronger compared to the phenotypic correlations for NBA and NW. For all studied litter size traits, the weakest relationship was found between the first four farrowings (1st–4th parity) and more stronger correlation was found between the latest four farrowings (5th–8th parity). The repeatability estimates for the LW sow’ litter size traits were generally low, 0.217 ± 0.037, 0.141 ± 0.032 and 0.073 ± 0.027 for TNB, NBA and NW, respectively, indicating that most of the phenotypic variance is explained by other factors than sows’ variance (primarily, by environmental factors). In addition these results indicate that the repeatability estimates for TNB were higher than for NBA, and the repeatability estimates for NBA were higher than for NW. This may be due in part to the gain of the permanent environmental effect on the number of stillborn piglets and the high rate of pre-weaning mortality for later parities.