North Carolina State University, Raleigh, NC 27695, USA.
J Anim Sci. 2010 Sep;88(9):2913-9. doi: 10.2527/jas.2009-2639. Epub 2010 Jun 4.
Variance components and genetic correlations were estimated among estrus, puberty, growth, and composition traits in Landrace-Large White gilts (n = 1,225; Genetic Improvement Services, Newton Grove, NC) from 59 sires and 330 dams. Four groups of gilts entered the North Carolina Swine Evaluation Station in Clayton at an average age of 162 d and were checked daily for estrus. Once 70% of gilts had reached puberty, recording of estrus symptoms occurred every 12 h for 30 d, using fence-line boar contact. Subjective estrus traits were maximum strength of standing reflex with or without a boar present, total strength of standing reflex with or without a boar present, and strength of vulva reddening and swelling. Objective estrus traits consisted of vulva redness, vulva width, length of estrus in consecutive days based on 12-h observations, and age at puberty (AGEPUB). Growth and composition traits included puberty weight, days to 114 kg (DYS), 10th-rib backfat, and 10th-rib LM area at 114 kg (BF, LMA) and puberty. Variance components were estimated using AIREMLF90 with an animal model. All models included gilt development diet class and breed composition as fixed effects, entry age as a covariate (except DYS, BF, and LMA), a random common litter effect, and a random animal genetic effect. Heritability estimates for length of estrus, maximum strength of the standing reflex with a boar, total strength of the standing reflex with a boar, maximum strength of the standing reflex without a boar, total strength of the standing reflex without a boar, vulva redness, strength of vulva reddening and swelling, and vulva width were 0.21, 0.13, 0.26, 0.42, 0.42, 0.26, 0.45, and 0.58, respectively. Heritability estimates for AGEPUB, puberty weight, 10th-rib backfat at puberty, 10th-rib LM area at puberty, DYS, BF, and LMA were 0.29, 0.39, 0.41, 0.38, 0.24, 0.47, and 0.39, respectfully. Common litter effect estimates ranged from 0.01 to 0.09. The estimated genetic correlation between length of estrus and maximum strength of standing reflex with a boar was 0.99. Genetic correlations between AGEPUB and length of estrus, maximum strength of standing reflex with a boar, and vulva redness were -0.23, -0.32, and 0.20, respectively. Length of estrus had positive genetic associations with DYS and BF (0.30 and 0.29, respectively). It was concluded that past selection for lean BW gain may have weakened the strength of the standing reflex and that sufficient genetic variation exists to make selection for improved swine estrus traits effective.
在北卡罗来纳州克莱顿的北卡罗来纳州斯旺评估站，59 头公猪和 330 头母猪的后代 1225 头长白-大约克母猪被平均分为 4 组，进入评估站，进入评估站时的平均年龄为 162 日龄，之后每天都会检查发情情况。一旦 70%的母猪达到性成熟，将使用围栏线公猪接触的方式，连续 30 天，每 12 小时记录一次发情症状。主观发情特征包括有或没有公猪存在时站立反射的最大强度、有或没有公猪存在时站立反射的总强度以及外阴部的红肿和肿胀程度。客观发情特征包括外阴部的颜色、外阴部的宽度、根据 12 小时观察结果连续发情的天数以及性成熟年龄。生长和组成性状包括性成熟体重、达到 114kg 的天数（DYS）、第 10 肋骨背膘和达到 114kg 时第 10 肋骨 LM 面积（BF、LMA）以及性成熟体重。使用 AIREMLF90 动物模型估计方差分量。所有模型均包含母猪育肥日粮类型和品种组成作为固定效应、进入年龄作为协变量（除了 DYS、BF 和 LMA 之外）、一个共同的随机窝效应和一个随机的动物遗传效应。发情持续时间、有公猪存在时站立反射的最大强度、有公猪存在时站立反射的总强度、无公猪存在时站立反射的最大强度、无公猪存在时站立反射的总强度、外阴部的颜色、外阴部红肿和肿胀的强度以及外阴部的宽度的遗传力估计值分别为 0.21、0.13、0.26、0.42、0.42、0.26、0.45 和 0.58。性成熟年龄、性成熟体重、性成熟时第 10 肋骨背膘、性成熟时第 10 肋骨 LM 面积、DYS、BF 和 LMA 的遗传力估计值分别为 0.29、0.39、0.41、0.38、0.24、0.47 和 0.39。共同窝效应估计值在 0.01 到 0.09 之间。发情持续时间和有公猪存在时站立反射的最大强度之间的遗传相关性估计值为 0.99。性成熟年龄与发情持续时间、有公猪存在时站立反射的最大强度和外阴部颜色之间的遗传相关性分别为-0.23、-0.32 和 0.20。发情持续时间与 DYS 和 BF 呈正遗传关联（分别为 0.30 和 0.29）。研究结论认为，过去对瘦肉型 BW 增重的选择可能削弱了站立反射的强度，并且存在足够的遗传变异，可以有效地选择改善猪的发情特征。
