A longitudinal field study investigating the association between teat-end shape and two minute milk yield, milking unit-on time, and time in low flow rate

Data from electronic milk meters that measure milking characteristics have been used to monitor and improve parlor efficiency. However, the variability within them and associated cow characteristics such as teat-end shape have not been investigated by rigorous methods. Our primary objective was to investigate the association of teat-end shape (TES) and the milking characteristics: two minute milk yield (2MIN), milking unit-on time (DUR), and time in low flow rate (LOW). The secondary objective was to determine which of cow, day, and milking time (i.e., 1st, 2nd, and 3rd milking session of each day) contributes most of the variation in 2MIN, DUR, and LOW. In a longitudinal field study 284601 milking observations from 3312 cows were analyzed from a commercial dairy herd. Cows were milked thrice daily. Teat-end shape was classified into 3 categories: pointed, flat, and round. Udder level milking characteristics were gathered using on-farm milk meters. Three-level null models were generated to determine the variance components present at the different levels. Cow, day, and milking time attributed 84%, 2%, and 14%; 78%, 2%, and 20%; and 21%, 5%, and 74% to the variation in 2MIN, DUR, and LOW, respectively. A multivariable linear regression model showed differences in 2MIN [least squares means ± standard errors (LSM ± SE)] among cows with different TES: 6.4 ± 0.1; 7.3 ± 0.1; and 6.7 ± 0.1kg in cows with pointed, flat, and round TES, respectively. There was an interaction between TES and milking mode such that DUR was shortest for cows with flat [LSM ± SE (229 ± 3s)] TES when milked on automatic take-off compared with cows with pointed (248 ± 3s) and round (243 ± 1s) TES, but was not different when milking clusters were detached manually. Time in low flow rate was lowest in cows with flat [LSM, 95%CI (10.3, 9.9–10.7s)] TES when milked on automatic take-off compared with cows with pointed (11.4, 11.1–11.7s) and round (11.5, 11.4–11.6s) TES, whereas LOW was highest in cows with flat (30.2, 27.5–33.2s) TES compared with cows with pointed (19.0, 18.0–20.1s) and round (19.7, 19.1–20.2s) TES when milking clusters were detached manually. Different milking machine settings and milking routine such as limiting the employment of manual milking mode for cows with different TES might have the potential to increase parlor efficiency and decrease potentially harmful effects of machine milking on teat tissue condition.