School of Veterinary Science, The University of Queensland, St Lucia, QLD 4072, Australia.
Anim Reprod Sci. 2010 Apr;118(2-4):163-70. doi: 10.1016/j.anireprosci.2009.08.006. Epub 2009 Aug 21.
The influence of nutrition during the first and second trimesters of gestation on the occurrence of dystocia was investigated in 3-year-old composite-breed beef heifers. Heifers were allocated according to stratification by weight and genotype to either a high (H/-=76 MJ metabolisable energy (ME) and 1.4 kg crude protein (CP)), or low (L/-=62 MJ ME and 0.4 kg CP daily) nutritional treatment on the day of artificial insemination (day 0) to the same Senepol bull. Half of each nutritional group changed to an opposite nutritional group on day 93 of gestation (-/H=82 MJ ME and 1.4 kg CP; -/L=63 MJ ME and 0.4 kg CP daily), resulting in four treatment groups: HH (n=16); HL (n=19); LH (n=17); LL (n=19). From 180 days until calving all heifers were fed the same diets. Pelvic area measures were taken at heifer selection (-72 days) and at 117 days. Maternal circulating concentrations of estrone sulphate (ES), bovine placental lactogen (bPL), bovine pregnancy associated glycoprotein and progesterone were monitored throughout gestation. Heifers were observed continuously over the calving period and delivery type classified as being either eutocic or dystocic. The occurrence of dystocia was 14.1%. Increased calf birth weight increased the odds of occurrence of dystocia (odds ratio (OR)=1.40; 95% confidence interval (95% CI) 1.12-1.76; P<0.01). High diets in the second trimester were associated with heavier calves at birth (P=0.01). The mean pelvic area of eutocic heifers on -72 d, tended to be greater compared to that of dystocic heifers (P=0.08) such that a 1-cm(2) difference in pelvic area tended to decrease the risk of dystocia (OR=0.97; 95% CI 0.93-1.01; P=0.09). Longer gestation length was associated with an increased risk of dystocia (P=0.03). ES (P=0.04) and bPL (P=0.09) at calving were positively associated with the risk of dystocia. In conclusion, the current study demonstrates (a) that pelvic area measurement at selection in 3-year-old Bos indicusxBos taurus heifers may be useful for identifying heifers at an increased risk of dystocia and (b) increased ES and bPL concentrations at calving are associated with increased risk of dystocia. Pelvic area measurements obtained prior to conception remain valid in their assessment of the relationship between pelvic area and likelihood of dystocia occurring in the event of changing maternal nutrient intake during gestation. This is an important finding given maternal diets high in protein and energy during the second trimester of gestation increased calf birth weight and calf birth weight was associated with an increase in the occurrence of dystocia in heifers calving as 3-year olds.
本研究旨在探讨妊娠前两个月的营养状况对难产发生的影响，选用了 3 岁杂交安格斯小母牛。小母牛按照体重和基因型分层，于人工授精当天（第 0 天）分配至高（H/-=76MJ 代谢能和 1.4kg 粗蛋白）或低（L/-=62MJ ME 和 0.4kg CP 日）营养处理组，与同一头塞尼佩尔公牛配种。一半的小母牛在妊娠第 93 天（-/H=82MJ ME 和 1.4kg CP；-/L=63MJ ME 和 0.4kg CP 日）时转换为相反的营养处理组，从而产生了四个处理组：HH（n=16）；HL（n=19）；LH（n=17）；LL（n=19）。从 180 天到分娩，所有小母牛都喂食相同的日粮。在小母牛选择（-72 天）和 117 天时进行骨盆区域测量。监测了整个妊娠期间母体循环中雌酮硫酸盐（ES）、牛胎盘催乳素（bPL）、牛妊娠相关糖蛋白和孕酮的浓度。在分娩期间连续观察小母牛，并将分娩类型分类为正常分娩或难产。难产的发生率为 14.1%。增加的犊牛出生体重增加了难产的发生几率（比值比（OR）=1.40；95%置信区间（95%CI）为 1.12-1.76；P<0.01）。妊娠中期的高日粮与出生时较重的犊牛有关（P=0.01）。正常分娩小母牛的平均骨盆面积在-72 天时趋于大于难产小母牛（P=0.08），即骨盆面积相差 1cm²，难产的风险降低（OR=0.97；95%CI 0.93-1.01；P=0.09）。较长的妊娠期与难产风险增加有关（P=0.03）。分娩时 ES（P=0.04）和 bPL（P=0.09）与难产风险呈正相关。总之，本研究表明：（a）在 3 岁印度野牛×瘤牛小母牛中，选择时的骨盆面积测量可能有助于识别难产风险增加的小母牛；（b）分娩时 ES 和 bPL 浓度增加与难产风险增加有关。在受孕前获得的骨盆面积测量值在评估妊娠期间母体营养摄入变化时与骨盆面积和难产发生几率之间的关系仍然有效。鉴于妊娠中期高蛋白和高能量的母体日粮增加了犊牛的出生体重，并且犊牛的出生体重与 3 岁小母牛的难产发生率增加有关，这是一个重要的发现。
