Atashi Hadi, Asaadi Anise
Shiraz University Department of Animal Science Shiraz Iran Shiraz University, Department of Animal Science, Shiraz, Iran.
Shiraz University School of Veterinary Medicine Department of Clinical Science Shiraz Iran Shiraz University, School of Veterinary Medicine, Department of Clinical Science, Shiraz, Iran.
Anim Reprod. 2019 Nov 18;16(4):846-852. doi: 10.21451/1984-3143-AR2019-0005.
In this study, 252,798 lactations on 108,077 cows in 433 herds were used to determine the association between gestation length (GL) and lactation performance, lactation curve, calf birth weight and dystocia in Holstein dairy cows in Iran. The GL averaged 278.1 ± 5.41 d, was categorized as short (SGL; at 1 SD below the population mean), average (AGL; the population mean ± 1 SD), or long (LGL; at least 1 SD above the population mean). Factors including parity, calf gender and calving season were associated with the GL. Primiparous cows with SGL had less lactation performance than those with longer GL; however, there was no difference between those with AGL and LGL. Multiparous cows with longer GL always had more partial and 305-d lactation performance. Primiparous cows with SGL produced less milk at the beginning of lactation and at the peak than those with AGL or LGL; inverse trends were found for lactation persistency, upward and downward slopes of the lactation curve. Within multiparous, a direct relationship was found between GL and the peak yield, where cows with longer GL always produced more milk at the peak. Multiparous cows with SGL produced less milk at the beginning of lactation, reached their peaks later, had higher lactation persistency and showed a lower upward slope of lactation curve than those with AGL or LGL. There was a direct relationship between GL and calf birth weight, where cows with longer GL had calves with more weight at the birth. Within primiparous, cows with SGL had the lowest and those with LGL had the highest rate of dystocia. However, multiparous cows with AGL had a lower rate of dystocia than those with SGL or LGL. Although there was a direct relationship between GL and lactation performance, intermediate GL seems optimal when considering dystocia.
在本研究中，对伊朗荷斯坦奶牛433个牛群中108,077头奶牛的252,798次泌乳进行分析，以确定妊娠期长度（GL）与泌乳性能、泌乳曲线、犊牛出生体重及难产之间的关联。GL平均为278.1±5.41天，分为短（SGL；低于群体均值1个标准差）、平均（AGL；群体均值±1个标准差）或长（LGL；高于群体均值至少1个标准差）。胎次、犊牛性别和产犊季节等因素与GL相关。初产母牛中，SGL的母牛泌乳性能低于GL较长的母牛；然而，AGL和LGL的母牛之间无差异。经产母牛中，GL较长的母牛总是具有更高的部分泌乳性能和305天泌乳性能。初产母牛中，SGL的母牛在泌乳初期和高峰期产奶量低于AGL或LGL的母牛；泌乳持续性、泌乳曲线的上升和下降斜率则呈相反趋势。在经产母牛中，GL与产奶高峰期产量呈直接关系，GL较长的母牛在高峰期产奶量总是更高。SGL的经产母牛在泌乳初期产奶量较低，达到峰值的时间较晚，泌乳持续性较高，泌乳曲线上升斜率低于AGL或LGL的母牛。GL与犊牛出生体重呈直接关系，GL较长的母牛所产犊牛出生体重更大。在初产母牛中，SGL的母牛难产率最低，LGL的母牛难产率最高。然而，AGL的经产母牛难产率低于SGL或LGL的母牛。尽管GL与泌乳性能呈直接关系，但考虑到难产情况，中等长度的GL似乎最为理想。
