Date Full Report Received

Date Abstract Report Received


Primary Investigator:
  1. Objectives: The principal objective of the Main Trail was to study associations among the established litter birth weight phenotype of nucleus/multiplication sows and the retention of their gilt progeny during development and selection, and the lifetime productivity and retention in the breeding herd. Collectively, these results were expected to inform decisions about how gilt selection programs affect efficiencies from the production nucleus/multiplication level to the level of terminal line production on commercial sow farms (Objective 1).
  2. How research was conducted: Extensive data capture and data auditing was used to document the fate of over 7,500 potential Camborough replacement gilts born to sows with an established average litter birth weight phenotype (ALBW_P). Agreed protocols for Pre-selection of gilts at weaning (Pre-select 1), and for entry to both off-site and on-site GDU stimulation programs (Pre-select 2 at around 170 days), limited the non-selection of gilts on the basis of relatively low growth rates, thus allowing the impact of greatest range of preselection growth rates on selection rates and SLP to be determined. Gilts were stimulated to reach pubertal estrus using optimized GDU/BEAR facilities on the down-stream farms included in the study. Gilt flows were also directed at down-stream sow farms where the risks of disease-related effects on production performance during the Main Trail were thought to be minimal. Data were excluded from final analysis of birth weight phenotype effects when evidence of non-compliance with established management
  3. Results. Notwithstanding these constraints analyses of lifetime performance in the breeding herd involved data from over 2,500 select gilts for which litter of origin data were available.
  4. Research findings: Litter birthweight phenotype significantly affected the retention of gilts through post-natal development to Pre-selection at around 170 days of age. As in commercial line litters, higher peri-natal mortality and poor pre-weaning survival were significant risk factors in gilts born to sows with a low aALBW_P. However, non-selection at later stages of development continued to be an issue for gilts born to sows with a lower ALBW-P, resulting in a 10 to 15% lower selection rate in the gilt progeny born to the low compared to the medium-low, medium-high and high ALBW_P sows. In the gilts that were Pre-selected for entry to the off-site and on-farm GDUs involved in this study, ALBW_P was positively associated with growth rate to entry to the GDU: However, final selection rates for the pre-select gilts and the response to puberty induction protocols were not affected by ALBW_P. As a result, the lasting effects of ALBW_P were on weight at selection and breeding. Interestingly, the higher growth rates of gilts derived from dams with the medium-high and high ALBW_P were determined to be a risk factor for future retention in the breeding herd: With a mean estimated breeding weight of around 150 kg in this replacement gilt cohort, a substantial proportion of these gilts would exceed the upper target weight at breeding of 150 kg.

    The lack of an effect of the ALBW_P of pre-select gilts on pubertal onset, was mirrored by a lack of effect on the percentage of gilts bred, and on total litter size born over at least three parities. However, retention in the breeding herd was negatively associated with ALBW_P, and poor retention was intuitively linked to heavier weights at breeding and subsequent removal due to lameness and poor locomotion.

  5. What these findings mean for the industry:
    These findings indicate that poor survival to weaning, and lower gilt retention rates during development, are critical issues for low birth weight gilts and for gilts born to sows with a low ALBW_P. Therefore, retaining sows in the production genetic nucleus population if they exhibit a repeatable low ALBW_P negatively impacts the efficient production of replacement gilts and represents a poor return on the investment of their high genetic merit. Nucleus sow culling strategies aimed at the early removal of the 10 to 15% of sows with the extreme low ALBW_P, as well as non-selection at birth of the lower birth weight gilts from other litters, will improve the overall efficiency of the nucleus/multiplication farm.

    Using current pre-selection criteria for gilts entering the GDU stage of production, lifetime growth performance and litter of origin traits have little impact on breeding performance. However, gilts born to the higher ALBW_P sows were heavier at breeding and their retention in the breeding herd was a risk factor for SLP. The risk of gilts being too heavy at breeding and negatively affecting subsequent retention in the breeding herd, emphasizes the importance of efficient GDU/BEAR programs that minimize entry to service intervals. The present study demonstrated that such programs can be implemented in large commercial systems and the success of these selection and pre-breeding programs makes a fundamental contribution to achieving acceptable SLP.

  6. Contact information:
    Dr. George Foxcroft. E-mail: george.foxcroft@ualberta.ca
    Jenny Patterson. E-mail: jennifer.patterson@ualberta.ca