Tsunenori Homma

Publication Date


Advisor(s) - Committee Chair

Gordon Jones, James Worthington, Elmer Gray


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Degree Program

Department of Agriculture

Degree Type

Master of Science


Sow productivity data on 756 litters at Green Hill Farm in Wolcott, Indiana, were used in the present study. The data were collected from March 1981 to May 1983. The sows were all purebred Landrace and Yorkshire. This seedstock herd is well managed, closed, totally confined, and Specific Pathogen Free. Thus, the effect of temporary environmental influences on sow productivity was minimized. Cross-fostering of pigs was practiced to reduce variability of the number of nursing pigs. Selection of sows occurred continuously during the data collection period.

The sow productivity measurements analyzed in this study were number of pigs born (NB), number of pigs born alive (NBA), number of pigs after transfer (NAT), number of pigs at 21 days (N21), 21-day litter weight (W21), and sow productivity index (SPI). The W21 was adjusted for age, mating type, season, NAT, and parity. The final form of the adjusted W21 was designated ADJW. The SPI was calculated from the formula SPI = 6.5 x NBA + ADJW.

Concerning adjustment factors, W21 was significantly influenced by season, NAT, and parity. The variability of deviations for NAT greater than 10 had a narrow and inconsistent range; thus, the same adjustment factor was used for all litters with NAT greater than 10. Sows appear able to reach their maximum milking ability if nursing at least 11 pigs. Landrace sows exceeded Yorkshire sows in all traits studied except NBA. After adjustment for heterosis, the selected sows with purebred litters gave higher performance figures than the sows with crossbred litters.

All the coefficients of correlation between six sow productivity traits were significant (P<.01) except three combinations – NB x ADJW, NBA x ADJW, and NAT x ADJW. The coefficient of determination between ADJW and N21 was .30. Since the environmental variability was minimized, the residual variability (.70) in ADJW was probably due to differences in milking ability among sows. The coefficients of correlation were consistent across breeds and parity groups.

In the overall analysis the post-farrowing traits, such as N21 and ADJW, showed higher repeatability estimates than the birth traits, such as NB and NBA. In birth traits, repeatability estimates were higher for Landrace than for Yorkshire sows. In post-farrowing trait estimates, both breeds showed the same repeatability. Repeatability estimates of post-farrowing traits were higher for sows nursing crossbred litters than for sows nursing purebred litters. Noticeable declines of W21 and SPI were found between two successive parities within individual sows.


Agriculture | Animal Sciences | Life Sciences