Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: November 20, 2003
Publication Date: August 1, 2004
Citation: Wise, T.H., Klindt, J.M. 2004. Relationships of leptin, backfat and body weight in gilts [abstract]. Journal of Animal Science. 82 (Supplement 2):87. (Abstract #238) Technical Abstract: Market pigs today have a degree of leanness that may be associated with delayed puberty. It is known that a degree of body fat is required for initiation and maintenance of reproductive function. Leptin produced by adipocytes acts through leptin receptors in the upper brain centers to control appetite and food intake thus communicating information about degree of fatness. To analyze the role of body weight (BW) and backfat thickness (BF) in initiation of first estrus, age of puberty was monitored from offspring of two genetic sire lines representing Duroc (D) and Landrace (L) bred to maternal line White cross gilts. In a second study, the D and L sire lines were crossed (DxL) to produce maximum variation. At first estrus, BF was measured ultrasonically at the first rib, last rib, and last lumbar vertebrae and BW recorded. The first year, 215 D sired gilts and 207 L sired gilts were studied. The second year, 521 DxL F2 gilts were studied. To provide insight into the mechanism of fat accumulation and endocrine effects, serum leptin concentrations were measured by RIA at puberty. Sire line effects were NS in relation to age of puberty, BW, BF, and leptin concentrations. However, significant sire effects were noted in all traits measured. Frequency analysis showed that leptin concentrations were greatest (P < 0.01) when the majority of animals attained puberty (196 +/ 1.2 days of age). Gilts with delayed puberty (> 230 days of age, mean age of puberty +/ 1 SD) had increased BW (P < 0.01) and BF but decreased (P < 0.01) leptin concentrations. Incidence of delayed puberty was 31% in D sired gilts, 32% in L sired gilts and 20% in the DxL F2 gilts. Gilts with delayed puberty had sufficient BW and BF but low leptin levels, suggesting delayed puberty in these gilts may be a result of gilts still being in a perceived growth phase of development and/or have a deficiency in leptin secretion. Identification of the genetic component associated with the low leptin levels/delayed puberty would provide a management tool to identify gilts that have attained market weight but will not produce a litter by a year of age.