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Title:   Author  item
                                            CALDERON DIAZ, JULIA - Iowa State Universityitem
                                            Vallet, Jeffitem
                                            Lents, Clayitem
                                            Nonneman, Danny

                                                         - *Dan*item
                                            Miles, Jeremyitem
                                            Wright, Elaneitem
                                            Rempel, Leaitem
                                            Cushman, Robert

                                                         - *Bob*item
                                            Freking, Bradley

                                                         - *Brad*item
                                            Rohrer, Garyitem
                                            PHILLIPS, C - Murphy Brown Llcitem
                                            DEDECKER, A - Murphy Brown Llcitem
                                            FOXCROFT, GEORGE - University Of Albertaitem
                                            STALDER, KENNETH - Iowa State University
  Submitted to: Journal of Animal Science Supplement
                                    Publication Type: Abstract Only
                                    Publication Acceptance Date: 3/1/2015
                                    Publication  Date: 3/1/2015
                                    Citation: Calderon Diaz, J.A., Vallet, J.L., Lents, C.A., Nonneman, D., Miles, J.R., Wright-Johnson, E.C., Rempel, L.A., Cushman, R.A., Freking, B.A., Rohrer, G.A., Phillips, C.E., DeDecker, A.E., Foxcroft, G., Stalder, K. 2015. Age at puberty, ovulation rate, and reproductive tract traits of developing gilts fed two lysine levels and three metabolizable energy levels from 100 to 260 d of age [abstract]. Journal of Animal Science. 93(Supplement 2):81 (Abstract #180).Interpretive Summary:
                                Technical Abstract: The objective of this study was to determine the effect of feeding different lysine and metabolizable energy (ME) levels to developing gilts on age at puberty and reproductive tract measurements. Crossbred Large White × Landrace gilts (n = 1221) housed in groups from 100 d of age until slaughter (approximately 260 d of age) were randomly allotted to 6 corn-soybean diets formulated to provided 2 standardized ileal digestible lysine levels [100% (HL), 85% (LL)] and 3 ME levels [90% (LME), 100% (MME), 110% (HME)] at 100 d of age.  The 100% lysine and 100% ME were based on an informal survey from the U.S. commercial swine industry to obtain average levels that are currently fed to developing gilts. Gilts were weighed and backfat thickness and loin muscle area were recorded at the beginning of the trial and then every 28 d. Starting at 160 d of age, gilts were exposed daily to vasectomized boars and observed for behavioral estrus. At slaughtered, their reproductive tract was collected and examined to determine whether the gilt was cyclic, estrous cycle stage, ovulation rate, uterine length, and ovary length and width.  Data were evaluated for normality and analyzed using mixed model methods. Average age at puberty was 193 d of age with a range from 160 d to 265 d. There was no difference in age at puberty among dietary treatments (P > 0.05). Approximately 6% of gilts were not observed in standing estrous; however, only 4% of gilts had not attained puberty when evaluated at slaughter, determined by the absence of corpora lutea or corpora albicantia. The remainder of gilts with no observed standing estrus were assumed to be behaviorally anestrus (cycling but no signs of standing estrus observed). At slaughter, there were more pre-pubertal gilts in the low lysine treatment when compared with high lysine treatments (33 vs. 16 gilts, respectively), thus low protein in the diet was associated with puberty failure. There were no differences between dietary treatment for ovulation rate, uterine length, and ovary length and width.  Uterine length in this experiment varied with stage of the cycle and was greater as gilt body weight increased. Despite significant differences in the lysine:energy ratio in the diets, the expected differences in reproductive traits were not observed. Other factors such as BW and days of estrous had a greater effect on the traits recorded than feed provided.


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