TY - JOUR
T1 - A retrospective cohort study investigating the association of individual quarter dry-off with udder health, milk production, and culling risk
AU - Wieland, M.
AU - Skarbye, A. P.
N1 - Publisher Copyright:
© 2024 American Dairy Science Association
PY - 2024/7
Y1 - 2024/7
N2 - Individual quarter dry-off (QDO) has been increasingly employed as a strategy for managing cows with chronically elevated SCC and recurrent clinical mastitis. However, little knowledge is available on the effects of QDO on milk production, SCC, the risk of clinical mastitis, and the risk of removal from the herd. Therefore, this retrospective cohort study aimed to investigate these associations. Data from 471 dairy cows subjected to QDO were analyzed. The cows were housed on a 4,000-cow dairy farm with a thrice-daily milking schedule. The cows were grouped based on the reason for QDO: (1) cows detected with a nonlactating quarter at a fresh cow check (QFRESH); (2) cows with recurrent clinical mastitis (QMAST); (3) cows diagnosed with Staphylococcus aureus IMI (QSA); and (4) cows with chronic subclinical mastitis (QSCC). Additionally, we randomly selected herd mates at a ratio of 1:1 to serve as a control group (CON). Cows in the CON group were matched in terms of parity and stage of lactation. Generalized linear mixed models with an identical link were used to estimate milk yield and SCC at 1 test day before QDO (T-1) as well as 1, 2, and 3 (T1, T2, and T3) test days after QDO. All cows subjected to QDO exhibited a decrease in milk yield following QDO compared with their respective control groups. All QDO cows approached the yield of their control group by T3. In particular, the difference in milk yield between QMAST cows and their controls at T3 was less than the difference at T1. Cows in the QMAST and QSCC groups exhibited a decrease in their SCC following QDO. In particular, the SCC was significantly higher among QMAST cows than among their controls at T1, but this difference was no longer significant by T3. Proportional hazards regression models revealed that QDO was associated with clinical mastitis occurrence and removal from the herd. Compared with CON cows, the hazard ratio (95% CI) for clinical mastitis occurrence was 3.70 (1.65–8.28), 1.80 (1.31–2.47), and 2.27 (0.93–5.54) among QFRESH, QMAST, and QSA cows, respectively. The hazard ratio among QSCC cows was modified by the effect of parity. The hazard ratio (95% CI) for removal from the herd was higher among cows subjected to QDO than among CON cows (hazard ratio [95% CI] values of 2.30 [0.99–5.33], 3.27 [2.20–4.86], and 4.87 [1.81–13.12] for QFRESH, QMAST, and QSCC cows, respectively). We conclude that QDO can be a viable strategy for managing cows with recurrent clinical mastitis. However, the results for the cows that underwent QDO for other reasons are less clear, partially due to low statistical power. Therefore, future research should examine how to decrease the risks of clinical mastitis and removal from the herd among cows subjected to QDO.
AB - Individual quarter dry-off (QDO) has been increasingly employed as a strategy for managing cows with chronically elevated SCC and recurrent clinical mastitis. However, little knowledge is available on the effects of QDO on milk production, SCC, the risk of clinical mastitis, and the risk of removal from the herd. Therefore, this retrospective cohort study aimed to investigate these associations. Data from 471 dairy cows subjected to QDO were analyzed. The cows were housed on a 4,000-cow dairy farm with a thrice-daily milking schedule. The cows were grouped based on the reason for QDO: (1) cows detected with a nonlactating quarter at a fresh cow check (QFRESH); (2) cows with recurrent clinical mastitis (QMAST); (3) cows diagnosed with Staphylococcus aureus IMI (QSA); and (4) cows with chronic subclinical mastitis (QSCC). Additionally, we randomly selected herd mates at a ratio of 1:1 to serve as a control group (CON). Cows in the CON group were matched in terms of parity and stage of lactation. Generalized linear mixed models with an identical link were used to estimate milk yield and SCC at 1 test day before QDO (T-1) as well as 1, 2, and 3 (T1, T2, and T3) test days after QDO. All cows subjected to QDO exhibited a decrease in milk yield following QDO compared with their respective control groups. All QDO cows approached the yield of their control group by T3. In particular, the difference in milk yield between QMAST cows and their controls at T3 was less than the difference at T1. Cows in the QMAST and QSCC groups exhibited a decrease in their SCC following QDO. In particular, the SCC was significantly higher among QMAST cows than among their controls at T1, but this difference was no longer significant by T3. Proportional hazards regression models revealed that QDO was associated with clinical mastitis occurrence and removal from the herd. Compared with CON cows, the hazard ratio (95% CI) for clinical mastitis occurrence was 3.70 (1.65–8.28), 1.80 (1.31–2.47), and 2.27 (0.93–5.54) among QFRESH, QMAST, and QSA cows, respectively. The hazard ratio among QSCC cows was modified by the effect of parity. The hazard ratio (95% CI) for removal from the herd was higher among cows subjected to QDO than among CON cows (hazard ratio [95% CI] values of 2.30 [0.99–5.33], 3.27 [2.20–4.86], and 4.87 [1.81–13.12] for QFRESH, QMAST, and QSCC cows, respectively). We conclude that QDO can be a viable strategy for managing cows with recurrent clinical mastitis. However, the results for the cows that underwent QDO for other reasons are less clear, partially due to low statistical power. Therefore, future research should examine how to decrease the risks of clinical mastitis and removal from the herd among cows subjected to QDO.
KW - blind quarter
KW - bovine
KW - mastitis
KW - nonlactating quarter
UR - http://www.scopus.com/inward/record.url?scp=85196774457&partnerID=8YFLogxK
U2 - 10.3168/jds.2023-24400
DO - 10.3168/jds.2023-24400
M3 - Journal article
C2 - 38331181
AN - SCOPUS:85196774457
SN - 0022-0302
VL - 107
SP - 4942
EP - 4960
JO - Journal of Dairy Science
JF - Journal of Dairy Science
IS - 7
ER -