Level of dietary energy during prepubertal growth and reproductive development of gilts

Development of gilts that conceive early and continue to produce offspring is a primary objective of swine production. The objective of this study was to determine the degree of feed restriction during development required to optimize reproductive performance and efficiency in gilts. The effects tha t various patterns of growth had on reproductive development and performanc e of gilts through d 30 of gestation were investigated. At 13 wk of age and 41 kg BW, 192 white crossbred gilts were penned individually and assigned to receive 87.5%, 75%, 62.5%, and 50% of predicted ad libitum energy intake . The study was replicated in two seasons. At 25 wk of age, gilts were move d to group pens and allowed ad libitum access to feed, and estrous detectio n was initiated. Gilts were inseminated at first observed estrus and those recycling were remated. Post-mating gilts were fed 1.5x maintenance in stal ls. Gilts that did not return to estrus 17 to 30 d after mating were slaugh tered at 30 d of gestation. Reproductive tracts were collected and numbers of corpora lutea and live embryos were recorded. Feed restriction during de velopment resulted in differences in BW and backfat thickness at the start of the breeding period and differences in feed intake during breeding. Gilt s subjected to the greatest feed restriction during development consumed th e greatest quantity of feed during breeding. Feed intake during breeding wa s associated with BW and backfat gain during breeding. The treatment group that entered breeding lightest and leanest (50% of predicted ad libitum int ake) had the least number of days to first estrus, followed by the fattest, heaviest group (87.5% of predicted ad libitum intake). Treatment groups di d not differ (P > 0.38) in ovulation rate or live embryo numbers. Significa nt relationships between quantity of GE consumed during development and var iables considered important in reproductive development and performance wer e evident, such as BW and fatness at start of breeding and first detected e strus, and ovulation rate. Variation in dietary energy during the developme nt period impacted many aspects of reproductive development and performance . However, coupling restricted energy intake during development with ad lib itum intake during breeding negated many of the effects of feed restriction during the development period.