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First parity sow, Breeding backfat, Gestation energy, Lactation feed inake, Return to estrus


Records kept by the swine industry reveal that a large precentage of females entering the sow herd are culled prior to reaching their peak reproductive performance expected in their fourth to sixth parity. In herds with low replacement rates over 30% of the females are culled and in herds with high replacement rates this figure exceeds 50% annually. Of those sows not culled for health or structural problems, most are removed because they fail to return to estrus or fail to maintain pregnancy after their first or second litter. Low feed intake and excessive weight loss during lactation have been associated with this problem, particularly with first parity sows from very productive genetic lines. Many believe that selection of replacement females from lean genotypes and limit feeding the filts during the development stage has exacerbated the problem. Thin sows are often prevalent among the sows that are culled. However, research has demonstrated that absolute body condtion is not of itself associated with reproductive failure. Some feel that it is the amount of fat lost that is the problem, not the resulting body fat level after lactation. Sows with low feed intake and substantial body weight loss during lactation are among those most often culled due to failure to recycle. Sows with low feed intake are thinner than those with more desirable feed intake and have lost both body fat and body protein as they have lost weight. A feeding strategy that would increase lactation feed intake and allow sows to maintain body weight and condition during lactation, reguardless of their starting body fat level, might allow more sows to reach their potential for reproductive efficiency. The research reported herein was designed to evaluate the effect of body backfat level at breeding and the effect gestation energy level on sow lactation feed intake, body weight change, and return to strus of first parity sows.

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South Dakota State University


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