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One of the most common ways for dairy producers to increase milk production is by increasing milking frequency. Frequent milking during early lactation may not only increase milk yield during the frequent milking period, but also produce carry-over effects that last well into lactation. Furthermore, to produce increases in subsequent milk yield, the duration of the intervals between milking do not have to be the same, and frequent milking may only have to occur during the first 3 weeks after calving. By simply manipulating milking schedules, increased milking frequency in early lactation may be a relatively nonŠlabor intensive and economically beneficial way to increase a herd's milk production.

Increase in Yield: Fixed Increment or Percentage Increase?
Although most cows in the United States are still milked twice a day (2X), increasing numbers of cows are being milked three times a day (3X) (more than 25 percent in the latest U.S. Department of Agriculture sire summary data set). Profitability of 3X milking depends on the increase in milk income minus added cost associated with increased feed, labor, utilities, milking supplies, depreciation, and other expenses associated with the extra milking. Often when producers consider adopting increased milking frequency, a key factor in the decision is knowing what kind of increases to expect in milk production. In the past, the response to 3X milking has been characterized as a 15 to 20 percent increase. When compiling sire summaries, USDA still uses a percentage increase to adjust records for increased milking frequency although these factors have been adjusted downward recently.

Strong evidence suggests that the response in milk production is a fixed increment in milk yield rather than a percentage increase. In 1995, we summarized the results of more than 40 published comparisons of 2X versus 3X milking studies dating as far back as the 1930s. Over a complete lactation, 3X milking increased milk yield on average 7.7 lb/cow/day. This was a remarkable conclusion considering that the production response was similar regardless of the level of milk production of the cows. The same result can be expected when milking frequency is increased for only a short time during a later stage of lactation and then returned to the normal milking routine. In limited studies 4X milking has been shown to increase milk production by 10.8 lb/cow/day when compared to 2X. Yet, increasing milking frequency in early rather than mid to late lactation may result in increases in subsequent milk yield even after returning to 2X milkings.

Targeted Timing of Increased Milking Frequency
If more frequent milking for the complete lactation is not feasible because of parlor facilities or labor constraints, a different strategy is to target the timing of increased milking frequency for selected times during the lactation. This practice does increase milk during the period of increased milking; however, after a return to less frequent milking, milk yields generally go back to previous amounts.

If milking is increased immediately after calving, for at least 3 weeks, an apparent increase in milk yield continues even after increased milking stops. Master's thesis research by Ashley Sanders, University of Maryland, examined the effects of 6X versus 3X milking, from the time immediately after calving until week 6 postpartum in both first- and second-lactation cows. Here, milk production increases were maintained even beyond the 6 weeks of increased milking. While the response from first-lactation cows was minimal and nonsignificant, the second-lactation 6X and 3X cows produced 97 lb/cow/day and 83.8 lb/cow/day, respectively. Even after increased milking ceased and cows were milked only 3X, significant differences in milk yield within the second lactation group persisted. Over 305 days, second-lactation 6X cows produced 90.4 lb/cow/day while the first lactation 3X cows produced 84.0 lb/cow/day. The parity effect on milk production was attributed to lower body weight at calving as well as younger average age.

Increased Frequency in Less Time
Increased milking may not have to continue for 6 weeks to produce a carryover effect in milk yield. We currently are completing a study in which cows were milked for 4X immediately after calving until day 21 of lactation, when they returned to 2X milking. In contrast to the 6X milking study in which the milking intervals were approximately the same throughout the day, in this study, the milking intervals were quite short. The 4X cows were milked immediately before 2X cows and again approximately 3 hours later, at the end of the normal milking routine. This made the 2X milking interval approximately 9 to 11 hours while the 4X milking interval was only 3 to 8 hours.

During the 3 weeks of increased milking frequency, milk yields were 74.1 lb/cow/day for the 2X cows and 88.7 lb/cow/day for the 4X cows. After returning all cows to 2X milking, milk yields were 79.4 lb/cow/day and 85.6 lb/cow/day for the 2X and 4X cows, respectively (Figure 1). The difference (6.2 lb) is only slightly lower than the average response of 3X milking for a complete lactation (7.7 lb). These results are of particular importance since both the milking interval and the period of increased milking were relatively short, accounting for only 21 days in a standard 305-day lactation. This suggests that much of the benefit from increased milking frequency might be achieved with relatively little added labor for extra milking using a strategy in which cows are milked more frequently only during the very beginning of lactation.


Figure 1. Milk Production in cows milked 2X and 4X during weeks 1 to 40 postpartum. During weeks 1 to 3, 4X cows were milked 4X daily and at weeks 3 resumed 2X milking. Arrow indicates where 4X cows returned to the 2x milking routine.

Dr. Mark A. Varner (Professor & Extension Specialist, Dairy Integrated Reproduction Management - University of Maryland)

Dr. Richard A. Erdman (Chair of Department & Professor Animal & Avian Sciences - University of Maryland)

Dr. Anthony V. Capuco (Research Physiologist - United States Department of Agriculture)

Sarah Hale (non-available data at publishing)

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