Location: Livestock Bio-SystemsTitle: Body weight and growth in normal cyclic and acyclic gilts
Submitted to: Journal of Animal Science
Publication Type: Abstract Only
Publication Acceptance Date: 12/22/2020
Publication Date: 5/7/2021
Citation: Lents, C.A., Nonneman, D.J. 2021. Body weight and growth in normal cyclic and acyclic gilts [abstract]. Journal of Animal Science. 99 (Supplement 1):140-141. https://doi.org/10.1093/jas/skab054.237.
Technical Abstract: Anestrus, or failure to express estrus during boar exposure, is commonly observed in replacement gilts, and results primarily from either delayed onset of puberty (prepubertal; PP) or cyclic ovulations without behavioral estrus (behavioral anestrus; BA).Gilts born between 2007 and 2018 at USMARC were observed for age at puberty between 160 and 240 days of age. Mature boars were placed in an alleyway pen while a herdsman observed gilts for standing lordosis in response to the back pressure test. Gilts failing to be observed in estrus by 240 days of age were slaughtered (250.4 ± 0.3 days of age) and reproductive tracts recovered to determine if gilts had ovulated. Gilts were defined as PP (n = 606), BA (n = 649), or Peripubertal (n = 118; PP with large preovulatory follicles on the ovary). There were 96 age-matched, cyclic contemporary gilts included as cyclic control gilts. Body weights were recorded at birth, weaning, 8 weeks, and 21 weeks of age with hot carcass weight (HCW) recorded at slaughter. The objective was to retrospectively determine if growth and HCW differed between these groups. Data were analyzed as a mixed ANOVA using group as a fixed effect with sire and farrowing group to which the gilt was born as random effects. Birth weight, weaning weight, ADG at weaning, and weight at 8 weeks did not differ between groups (P > 0.16). The BA gilts had greater growth rate (weight per day of pig age at 21 weeks; P < 0.02) and HCW (P < 0.0001) than PP and Peripubertal gilts, which also had smaller HCW than control gilts. Some cyclic control gilts (7.3%) that displayed estrous behavior had a prepubertal reproductive tract with no ovulatory activity at slaughter. Results indicated that gilts exhibiting delayed puberty grow slower late in development and during boar exposure. Estrus without ovulation in replacement gilts may be more prevalent than assumed.