The attached poster, the third and last in the series, will help pork producers effectively screen replacement gilt candidates for quality of reproductive traits.
This poster focuses on reproductive abnormalities, disorders or injuries that can adversely affect gilts' abilities to remain productive through many parities. These traits are critically important, whether you are purchasing replacement gilts or producing your own in an internal multiplication program. The poster provides examples of the types of underline and external genitalia problems producers should avoid when selecting replacement gilts.
Reproductive soundness evaluation is a process of visual appraisal by scoring or evaluating animals for proper underline development, including a sufficient number of correctly placed teats. Replacement gilts should have at least 12 well-spaced (preferably six per side), properly sized, functional teats. Gilts with pin teats or inverted teats should be avoided.
When evaluating the external genitalia of gilts, be sure the vulva is of adequate size to avoid breeding and farrowing problems. A vulva that is abnormally small or infantile is an indication of an underdeveloped reproductive tract that may never conceive, or could present problems during the birthing process. Tipped-up vulvas should also be discriminated against.
Additionally, an injured vulva could impair successful breeding or cause farrowing difficulties. If severe, producers may want to cull these females or at least delay breeding until they are fully healed.
Identifying replacement gilts with one or more of these conditions and culling them, rather than utilizing them in the breeding program, may be one of the keys to lowering breeding herd replacement rates.
The underline and external genitalia shown on the poster can have genetic, health and environmental causes.
Keep in mind that poor underlines in a parent will also have an impact on the quality of underlines of its offspring. If animals with poor underline quality and insufficient numbers of teats are retained for breeding purposes, we would expect a significant number of their offspring to also have this condition.
Sows with poorly spaced or poor quality (pin and/or inverted) teats will not perform as well as their more sound counterparts.
If an excessive number of gilts have an inadequate number of teats, genetic improvement through selection can help, because the heritability of the trait is estimated at 25-30%.
Similarly, genetic and environmental factors contribute to small, infantile vulvas and other vulva disorders. Injuries to the external genitalia can be caused by sharp or protruding gates and equipment or by being bitten by a penmate.
Mycotoxins are another environmental influence on mammary and genital tissue appearance. Mycotoxins can make the mammary and external genitalia of gilts appear abnormally large or over-developed for their age. It is important to feed replacement gilts high-quality grains. Laboratory tests should be conducted on any feedstuffs suspected of mycotoxin contamination.
As with the conformation and structural soundness and feet and leg disorders in the two previous posters from the Jan. 15 and Feb. 15, 2005 issues of National Hog Farmer, the prevalence of underlines and external genitalia problems is greater than many managers realize.
And, it should be noted, not all gilts have perfect structural and reproductive soundness. Any selection program must evaluate and prioritize the importance of numerous traits. Compromises are often made with the reproductive soundness and other traits under consideration.
For example, a gilt with a minor underline defect may be retained if she has at least 12 fully functional nipples. Ask yourself: What impact will a defect have on an individual's productivity in the farrowing crate? How will it impact the productivity of her offspring?
Producers should be able to recognize these reproductive problems and cull animals exhibiting them when appropriate.
This series of posters was produced through the cooperative efforts of the Pork Checkoff, National Swine Registry, National Hog Farmer and Iowa State University Swine Extension.
Additional copies of the reproductive trait poster are available free to U.S. producers and agricultural educators. Non-producer and foreign poster orders are available at 50ยข each. Contact Pork Checkoff at (800) 456-PORK or visit the Pork Checkoff catalogue at www.porkboard.org. Complete sets of three posters are now available.