Abstract：
Preventing dystocia can stabilise beef cattle management. This study aimed to investigate the relationship between serum pregnancy-associated glycoproteins (PAGs) S-N values and estrone sulphate (E1S) concentrations during pregnancy and the calf birth weight in beef cattle and to evaluate their usefulness as new predictive parameters for dystocia due to foetal overgrowth. Thirty-eight pregnant Japanese Black cattle were used. Blood samples were collected at 40, 70, 100, 150, 200, 250, 280, and 285 days after artificial insemination (AI), and birth weight of the offspring was measured. Serum PAGs S-N values and E1S concentrations were measured, and the area under the curve (AUC) and the ratio of change based on 70 days after AI were calculated, followed by calculation of the correlation coefficient with the birth weight of the offspring and comparison between the eutocia (n = 32) and dystocia (n = 6) groups. The birth weight of the offspring was moderately positively correlated with the AUC of serum PAGs S-N values and E1S concentrations in the second (r = 0.425, P < 0.01) and third (r = 0.595, P < 0.01) trimesters, respectively. The ratio of change in serum E1S concentrations between 70 and 280 days after AI was greater (P < 0.05) in the dystocia group (1276.6 ± 229.1 %) than in the eutocia group (852.6 ± 69.6 %). These results suggest that blood PAGs S-N values at mid-pregnancy (100-199 days after AI) and the ratio of changes in blood E1S concentrations between 70 and 280 days after AI may be new parameters for predicting dystocia.
摘要：
预防难产可以稳定肉牛管理。本研究旨在探讨妊娠期间血清妊娠相关糖蛋白（PAGs）S-N值和硫酸雌酮（E1S）浓度与肉牛出生体重之间的关系，并评估其作为胎儿过度生长难产的新预测参数的有用性。使用了38头怀孕的日本黑牛。在人工授精（AI）后40、70、100、150、200、250、280和285天收集血样，并测量了后代的出生体重。测定血清PAGsS-N值和E1S浓度,计算曲线下面积（AUC）和基于AI后70天的变化率，然后计算与后代出生体重的相关系数，并比较顺产（n=32）和难产（n=6）组。子代出生体重与第2个(r=0.425,P<0.01)和第3个(r=0.595,P<0.01)三个月血清PAGsS-N值和E1S浓度的AUC呈中度正相关,分别。难产组AI后70～280天血清E1S浓度变化比例（1276.6±229.1％）大于顺产组（852.6±69.6％）（P<0.05）。这些结果表明，妊娠中期（AI后100-200天）的血液PAGS-N值和AI后70至280天之间血液E1S浓度变化的比率可能是预测难产的新参数。
