Willis H J, Zak L J, Foxcroft G R
Alberta Agriculture, Food and Rural Development, Edmonton, Alberta, Canada.
J Anim Sci. 2003 Aug;81(8):2088-102. doi: 10.2527/2003.8182088x.
The objectives of this study were to determine factors affecting the reproductive performance of primiparous sows early weaned (EW; n = 35) at d 14 or conventionally weaned (CW; n = 35) at d 24 of lactation. Sow BW and backfat were recorded at farrowing, weekly until weaning, and at standing heat. Feed intake was controlled throughout lactation to standardize nutritional effects on subsequent reproductive performance. Litter size was standardized across treatments within 48 h after farrowing, and litter weight was recorded until weaning. In subsets of sows, blood samples were collected from 10 h before to 10 h after weaning, and then every 6 h until ovulation. Sows were heat checked twice daily and bred at 24-h intervals during standing heat using pooled semen. Ultrasonography every 6 h determined time of ovulation. Sows were either slaughtered within 24 h after ovulation to assess ovulation rate, fertilization rate, and embryonic development in vitro, or at d 28 of gestation to determine ovulation rate and embryonic survival. Compared with CW sows, EW sows had more backfat at weaning (15.9 +/- 0.5 vs. 14.7 +/- 0.5 mm; P < 0.001). Also, CW sows tended to lose more BW and to have lower IGF-I concentrations, indicating poorer body condition. Duration of lactation did not affect ovulation rate (EW = 17.6 +/- 0.7; CW = 18.7 +/- 0.6), fertilization rate (EW = 96.0 +/- 2.2; CW = 88.2 +/- 4.7%), or embryo survival to d 28 (EW = 62.5 +/- 4.5; CW = 63.1 +/- 5.0%). There was a marginal effect of duration of lactation on weaning-to-estrus interval (EW = 120 +/- 3; CW = 112 +/- 3 h; P < 0.06) and duration of estrus (EW = 52.4 +/- 2.3; CW = 46.3 +/- 2.2 h; P < 0.08). Overall, embryonic survival, not ovulation rate, seems to be the limiting factor for potential litter size in the second parity. Although fertility in both EW and CW sows studied was compromised, endocrine and metabolic data indicate that the mechanisms affecting reproductive performance may differ between the two weaning systems. The LH, FSH, and estradiol data from the EW sows are characteristic of animals with limited follicular development and incomplete recovery of the hypothalamic-pituitary-ovarian axis; consequently, the integrity of the uterine environment may be adversely affected and limit embryonic survival. In CW sows, variability in metabolic state seemed to be the key factor limiting the fertility, again adversely affecting embryonic survival.
本研究的目的是确定影响初产母猪繁殖性能的因素，这些母猪在泌乳第14天进行早期断奶（EW；n = 35）或在第24天进行常规断奶（CW；n = 35）。在分娩时、直至断奶每周以及发情站立时记录母猪的体重和背膘厚度。在整个泌乳期控制采食量，以规范营养对后续繁殖性能的影响。分娩后48小时内对各处理组的窝仔数进行标准化，并记录窝仔体重直至断奶。在部分母猪中，从断奶前10小时至断奶后10小时采集血样，然后每6小时采集一次直至排卵。每天对母猪进行两次发情检查，并在发情站立期间每隔24小时使用混合精液进行配种。每6小时进行一次超声检查以确定排卵时间。母猪在排卵后24小时内屠宰以评估排卵率、受精率和体外胚胎发育情况，或在妊娠第28天屠宰以确定排卵率和胚胎存活率。与CW母猪相比，EW母猪断奶时背膘更厚（15.9±0.5对14.7±0.5毫米；P < 0.001）。此外，CW母猪往往体重减轻更多且胰岛素样生长因子-I浓度较低，表明体况较差。泌乳期长短不影响排卵率（EW = 17.6±0.7；CW = 18.7±0.6）、受精率（EW = 96.0±2.2；CW = 88.2±4.7%）或胚胎存活至第28天的情况（EW = 62.5±4.5；CW = 63.1±5.0%）。泌乳期长短对断奶至发情间隔（EW = 120±3；CW = 112±3小时；P < 0.06）和发情持续时间（EW = 52.4±2.3；CW = 46.3±2.2小时；P < 0.08）有轻微影响。总体而言，胚胎存活率而非排卵率似乎是第二胎潜在窝仔数的限制因素。虽然所研究的EW和CW母猪的繁殖力均受到损害，但内分泌和代谢数据表明，两种断奶系统影响繁殖性能机制可能不同。EW母猪的促黄体生成素、促卵泡素和雌二醇数据是卵泡发育受限和下丘脑-垂体-卵巢轴恢复不完全的动物的特征；因此，子宫环境的完整性可能受到不利影响并限制胚胎存活。在CW母猪中，代谢状态的变化似乎是限制繁殖力的关键因素，同样对胚胎存活产生不利影响。
