Department of Veterinary Sciences, Texas Tech University, Lubbock, TX 79415.
Department of Veterinary Sciences, Texas Tech University, Lubbock, TX 79415.
J Dairy Sci. 2024 Oct;107(10):8259-8270. doi: 10.3168/jds.2023-23981. Epub 2024 May 15.
The objective of this study was to evaluate the effect of selective dry cow therapy (SDCT) strategies based on 2 different algorithms in comparison with blanket dry cow therapy for measures of udder health, milk yield, and culling in herds not using internal teat sealant. Cows from 2 commercial farms in west Texas were randomized into 3 different groups: SDCT algorithm 1 (ALG1; n = 455) cows treated with an intramammary antimicrobial at dry-off if SCC >200,000 cells/mL at any Dairy Herd Improvement Association test date or if the cow had 2 or more cases of clinical mastitis (CM) during the enrollment lactation; SDCT algorithm 2 (ALG2; n = 458) cows treated with an intramammary antimicrobial at dry-off if SCC >200,000 cell/mL at last test date or any case of CM during the enrollment lactation; and control cows (CON = 447) received blanket dry cow therapy. None of the cows enrolled in the study received an internal or external teat sealant. Data related to milk and SCC linear score (LSCC) were collected monthly. Milk yield and LSCC during the first 6 mo of lactation were analyzed using repeated measures ANOVA models, while Cox proportional hazards models were fitted to culling and CM data. The farm was fitted as a random effect in all models. The percentage of cows receiving antimicrobials at dry-off was 51.3%, 24.7%, and 100% for ALG1, ALG2, and CON, respectively. Treatment did not influence the IMI dynamics during the dry period. Additionally, no statistical differences related to treatment were observed for LSCC and milk yield. The LSCC for ALG1, ALG2, and CON cows was 2.44, 2.41, and 2.26, respectively. The average milk yield for ALG1, ALG2, and CON cows was 43.2, 43.2, and 44.0 kg/d, respectively. Treatment did not affect CM incidence or culling. The cumulative incidence of CM was 19.6%, 19.4%, and 21.4% for ALG1, ALG2, and CON cows, respectively. Additionally, the cumulative risk of death or culling was 18.5%, 17.1%, and 19.5% for ALG1, ALG2, and CON cows, respectively. In conclusion, SDCT strategies led to a decrease in antimicrobial drug use at dry-off, without significantly affecting the incidence of CM, the risk of culling, LSCC, or milk yield of dairy cows. However, numerical differences in LSCC and milk yield were observed between treatment groups.
本研究的目的是评估基于两种不同算法的选择性干奶牛治疗（SDCT）策略与常规干奶牛治疗相比，对未使用乳头内封闭剂的牛群的乳房健康、产奶量和淘汰率的影响。来自德克萨斯州西部的 2 个商业农场的奶牛被随机分为 3 组：SDCT 算法 1（ALG1；n=455），如果 SCC 在任何奶牛群改良协会的测试日期超过 200,000 个细胞/ml，或者奶牛在入群泌乳期有 2 次或以上临床乳腺炎（CM）病例，在干奶时用抗生素治疗；SDCT 算法 2（ALG2；n=458），如果 SCC 在入群泌乳期的最后一次测试日期或任何 CM 病例中超过 200,000 个细胞/ml，在干奶时用抗生素治疗；对照组（CON=447）接受常规干奶牛治疗。研究中没有任何奶牛使用乳头内或外部封闭剂。每月收集与牛奶和 SCC 线性评分（LSCC）相关的数据。使用重复测量 ANOVA 模型分析泌乳前 6 个月的产奶量和 LSCC，使用 Cox 比例风险模型分析淘汰和 CM 数据。所有模型都将农场作为随机效应进行拟合。ALG1、ALG2 和 CON 组的奶牛在干奶时接受抗生素治疗的比例分别为 51.3%、24.7%和 100%。治疗对干奶期的 IMI 动态没有影响。此外，治疗对 LSCC 和产奶量没有统计学差异。ALG1、ALG2 和 CON 奶牛的 LSCC 分别为 2.44、2.41 和 2.26。ALG1、ALG2 和 CON 奶牛的平均产奶量分别为 43.2、43.2 和 44.0 kg/d。治疗对 CM 发病率或淘汰率没有影响。ALG1、ALG2 和 CON 奶牛的 CM 累积发病率分别为 19.6%、19.4%和 21.4%。此外，ALG1、ALG2 和 CON 奶牛的死亡或淘汰累积风险分别为 18.5%、17.1%和 19.5%。总之，SDCT 策略减少了干奶时抗生素的使用，但对奶牛的 CM 发病率、淘汰率、LSCC 或产奶量没有显著影响。然而，治疗组之间的 LSCC 和产奶量存在数值差异。
