从涉及84,189次泌乳的初始数据集中,这项研究评估了干旱期长度(DPL)与产奶量之间的关系,剔除风险,和生育能力。该数据集包括总共48,297头多胎奶牛泌乳记录,产牛事件发生在2019年和2020年,属于62个意大利牛群,至少有150头牛。DPL分为5类(<40、40-49、50-60、61-70和>70d),这些类别用于建立DPL与结果变量之间的关联。使用简单和多元线性回归以及Cox比例风险模型评估所有获得的数据。在61至70d(2,480.29kg/牛)和50至60d(2,474.39kg/牛)的DPL类别中,60d牛奶(DIM)的累积牛奶产量最高,最低为<40d(2,281.29公斤/头)。同样,DPL类别61至70天(10,830.94。kg/牛)和50至60d(10,817.48kg/牛)的最高305d产奶量,而<40天(10,200.96公斤/牛)的最低。DPL为40到49d和>70d的组略有,但意义重大,降低牛奶产量,因为累计60DIM和预测305天牛奶产量。剔除风险有曲线行为,在DPL<40d和DPL>70d的情况下,与DPL为50至60d的DPL相比,在前60DIM中剔除的几率显着提高[相对风险(RR):1.53;RR:1.46]。在同样的比较中,61至70d的DPL也有较高的剔除风险(RR:1.13)。DPL也与生育率有关,DPL为40至49d和50至60d,在前200个DIM中怀孕的可能性最大。<40、61-70和>70d的DPL与生育力呈负相关,妊娠风险分别为0.87、0.95和0.94。本文强调了DPL的重要性,因为我们证明了它与牛奶生产的关联,剔除,和生育能力。尽管对高产奶牛很有吸引力,非常短的干旱期同时也与较高的剔除风险相关,降低牛奶产量和生育率。长DPL是有害的,尤其是关于扑杀和生育。总之,通过提高繁殖性能来减少DPL的变异性并避免极端情况,最大限度地提高后期泌乳产量,并在脱水时间上做出明智的决定,在意大利乳制品条件下,可能会导致更好的性能和更低的早期剔除。
From an initial data set involving 84,189 lactations, this research evaluated the relationship between dry period length (DPL) and milk production, culling risk, and fertility. The data set included a total of 48,297 multiparous cow lactation records, with a calving event occurring in 2019 and 2020, belonging to 62 Italian herds with at least 150 cows. The DPL was classified into 5 categories (<40, 40-49, 50-60, 61-70, and >70 d) and these categories were used to establish the association between DPL and the outcome variables. All data obtained were assessed with simple and multiple linear regressions and Cox proportional hazard models. Cumulative milk production at 60 d in milk (DIM) was the highest in DPL categories of 61 to 70 d (2,480.29 kg/cow) and 50 to 60 d (2,474.39 kg/cow), and the lowest in <40 d (2,281.29 kg/cow). Similarly, DPL categories 61 to 70 d (10,830.94. kg/cow) and 50 to 60 d (10,817.48 kg/cow) had the highest 305-d milk production, whereas the <40 d (10,200.96 kg/cow) had the lowest one. The groups with a DPL of 40 to 49 d and >70 d had slightly, but significant, lower milk production both as cumulative 60 DIM and predicted 305-d milk production. Culling risk had a curvilinear behavior, with DPL <40 d and DPL >70 d showing significantly higher odds for culling during the first 60 DIM compared with DPL of 50 to 60 d [relative risk (RR): 1.53; RR: 1.46]. Within the same comparison, DPL of 61 to 70 d also had a slightly higher risk for culling (RR: 1.13). The DPL was associated also with fertility, with DPL of 40 to 49 d and 50 to 60 d having the greatest odds for pregnancy within the first 200 DIM. The DPL of <40, 61 to 70, and >70 d were negatively associated with fertility and showed pregnancy risks of 0.87, 0.95, and 0.94, respectively. This paper reinforces the importance of DPL as we demonstrated its association with milk production, culling, and fertility. Despite being attractive for high production dairy cows, very short dry periods are at the same time also associated with higher culling risk, lower milk production and fertility. Long DPL is detrimental, especially regarding culling and fertility. In summary, reducing variability in DPL and avoiding extremes by improving reproductive performance, maximizing late lactation milk production and making wise decisions on dry-off timing, may lead to better performances and lower early culling under Italian dairy conditions.