**2. Frequent milking or suckling during early lactation: a window of opportunity**

An exciting development for both dairy producers and dairy scientists was the finding that the timing of implementation can influence the milk yield response to frequent milking. During middle and late lactation, frequent milking increased milk production; however cessation of frequent milking resulted in an immediate decrease in milk yield to pre-treatment levels (Elliott, 1961; Morag, 1973a, b; Svennersten et al., 1990). During early lactation, however, frequent milking for a short duration can stimulate milk production and the effect persists through the remainder of lactation, even after less frequent milking is resumed. This effect was originally observed in experiments designed to determine the

milk yield loss associated with the use of nurse cows. Using identical twin cows, Everitt and Phillips (1971) discovered that suckling by calves in addition to machine milking during the first 8 to 10 weeks of lactation was associated with increased milk production after weaning and throughout the remainder of lactation in both primi- and multiparous cows (Figure 2). Shortly after this report, similar observations were made in both cows (Edmunds, 1977; Moss & O'Grady, 1978; Thomas et al., 1978; Fulkerson, 1981) and heifers (Fulkerson et al., 1978; Peel et al., 1979). Pearson et al. (1979) assigned cows to 3X for the first 143 d of lactation, followed by 2X thereafter. Although they did not report the full lactation curves, they measured milk yield for the entire lactation and reported that relative to 2X, cows that were milked 3X for the first 143 d of lactation produced more milk through 280 DIM (Pearson et al., 1979). Subsequently, it has been observed in numerous experiments that frequent milking during early lactation was associated with both acute and persistent increases in milk production (Table 5). These findings presented an opportunity for dairy producers; that an initial investment in labor could increase milk production efficiency for the remainder of lactation. Poole (1982) speculated that the practice might not be adopted, however, because producers would be discouraged by the partial decrease in milk production upon cessation of frequent milking, despite the significant carry-over effect.

**Figure 2.** The effect of suckling during early lactation on milk production of dairy cows. *Ad libitum* suckling for the first 8 weeks of lactation increases milk production through late lactation (re-drawn from Everitt and Phillips, 1971). Cows were either milked 2X during the entire lactation (solid line), or were suckled by calves until 8 weeks of lactation, followed by 2X milking thereafter (dashed line).


a Cows were assigned to unilateral frequent milking (twice daily milking of the left side, four times (**4X**) daily milking of the right side) for days 1 to 21, 1 to 14, or 7 to 21 of lactation (n = 10 cows per treatment). The differential milk yield response was adjusted to a whole-udder basis, and additional milk yield per cow was estimated (Wall & McFadden, 2007b). bFour times daily milking for days 1 to 21, 1 to 14 or 7 to 21 of lactation, followed by twice daily milking for the remainder of lactation.

c Additional feed to support increased milk production during frequent milking (**FM**), estimated at \$0.92/cow/d. dAdditional feed to support increased milk production after frequent milking, estimated at \$0.39/cow/d.

e Additional labor associated with extra milkings and animal handling during 4X milking, approximately \$4/d f Cost associated with extra milkings, including inflation replacement, teat dip, and towels; approximately \$0.025/d gExtra milk income is based on \$12/cwt.

hTotal net annual income for a 100-cow operation.

242 Milk Production – An Up-to-Date Overview of Animal Nutrition, Management and Health

significant carry-over effect.

**2**

**3**

**4**

**5**

**6**

**Milk yield (kg/d)**

**7**

**8**

**9**

**10**

milk yield loss associated with the use of nurse cows. Using identical twin cows, Everitt and Phillips (1971) discovered that suckling by calves in addition to machine milking during the first 8 to 10 weeks of lactation was associated with increased milk production after weaning and throughout the remainder of lactation in both primi- and multiparous cows (Figure 2). Shortly after this report, similar observations were made in both cows (Edmunds, 1977; Moss & O'Grady, 1978; Thomas et al., 1978; Fulkerson, 1981) and heifers (Fulkerson et al., 1978; Peel et al., 1979). Pearson et al. (1979) assigned cows to 3X for the first 143 d of lactation, followed by 2X thereafter. Although they did not report the full lactation curves, they measured milk yield for the entire lactation and reported that relative to 2X, cows that were milked 3X for the first 143 d of lactation produced more milk through 280 DIM (Pearson et al., 1979). Subsequently, it has been observed in numerous experiments that frequent milking during early lactation was associated with both acute and persistent increases in milk production (Table 5). These findings presented an opportunity for dairy producers; that an initial investment in labor could increase milk production efficiency for the remainder of lactation. Poole (1982) speculated that the practice might not be adopted, however, because producers would be discouraged by the partial decrease in milk production upon cessation of frequent milking, despite the

**Figure 2.** The effect of suckling during early lactation on milk production of dairy cows. *Ad libitum* suckling for the first 8 weeks of lactation increases milk production through late lactation (re-drawn from Everitt and Phillips, 1971). Cows were either milked 2X during the entire lactation (solid line), or were suckled by calves until 8 weeks of lactation, followed by 2X milking thereafter (dashed line).

**2 6 10 14 18 22 26 30 34**

Milked Suckled

**Week of Lactation**

**Table 4.** Potential economic return of milking four-times daily during early lactation.a


aReports on frequent milking during the entire lactation or on half-udders are represented in Tables 1 and 6. bNumbers in columns represent the increase in milk yield observed with increased milking frequency

c 2X = twice daily milking; 3X = thrice daily milking; 4X = four times daily milking; 6X = six times daily milking. dNumbers in columns represent days in milk.

e Pers. = the persistent increase in milk production after cessation of frequent milking.

f Acute = the increase in milk production during frequent milking.

**Table 5.** Summary of select literature reports on the effects of frequent milking during early lactation on milk yield of dairy cowsa

In an attempt to minimize additional costs associated with frequent milking, and to investigate the response of dairy cows to frequent milking or suckling during a short interval of time in early lactation, Bar-Peled et al. (1995) compared 3X to 6X or 3X+suckling for the first 6 wk of lactation, followed by 3X of all cows. Relative to cows milked 3X during the entire lactation, 6X and 3X + suckling acutely increased milk production by 7.3 and 14.7 kg/d, respectively (Bar-Peled et al., 1995). Cessation of frequent milking or suckling was associated with a partial decline in milk production; however, a carry-over effect was observed in 6X cows (+5.1 kg/d relative to 3X; Bar-Peled et al., 1995). In a similar experiment, Sanders et al. (2000) observed an acute increase of 6 kg/d and a carry over response of 3.7 kg/d in 6X cows relative to 3X cows. In heifers, the acute response to 6X was lower in magnitude (+1.7 kg/d), and no carry over effect was observed (Sanders et al., 2000).

A summary of literature reports on the effect of suckling during early lactation on milk production is presented in Table 6. The results of subsequent experiments have further narrowed down the 'window' during early lactation wherein frequent milking can increase milk production for the remainder of lactation. Hale et al. (2003) assigned cows to 2X or to 4X for the first 3 wk of lactation, followed by 2X. Four times daily milking was associated with an acute increase of 8.8 kg/d and a carry over effect of 2.6 kg/d for the remainder of lactation. A treatment interval of 1 to 21 DIM was also used in a field study by Dahl et al. (2004b), who observed similar effects of frequent milking during early lactation. In contrast, VanBaale et al. (2005) assigned cows to 3X or 6X for the first 7, 14, or 21 d of lactation and reported that 6X did not increase milk production relative to 3X. Their observations were inconsistent with previous reports, and the authors speculated that facility logistics may have influenced their results because 6X cows were housed farther away from the milking parlor and spent a considerably longer time away from their pen than 3X cows (VanBaale et al., 2005). With the exception of one negative report (VanBaale et al., 2005), and one abstract (Fernandez et al., 2004), it is generally accepted that frequent milking increases milk yield, and that frequent milking or suckling during early lactation can increase milk production for the remainder of lactation (see Tables 5 and 6). The mechanistic basis for the milk yield response to frequent milking, however, is poorly understood. Even less understood are the mechanisms involved in the persistent effect on milk yield of frequent milking during early lactation.



 aPers. = the persistent increase in milk production after cessation of suckling, if reported bAcute = the increase in milk production during suckling

244 Milk Production – An Up-to-Date Overview of Animal Nutrition, Management and Health

In an attempt to minimize additional costs associated with frequent milking, and to investigate the response of dairy cows to frequent milking or suckling during a short interval of time in early lactation, Bar-Peled et al. (1995) compared 3X to 6X or 3X+suckling for the first 6 wk of lactation, followed by 3X of all cows. Relative to cows milked 3X during the entire lactation, 6X and 3X + suckling acutely increased milk production by 7.3 and 14.7 kg/d, respectively (Bar-Peled et al., 1995). Cessation of frequent milking or suckling was associated with a partial decline in milk production; however, a carry-over effect was observed in 6X cows (+5.1 kg/d relative to 3X; Bar-Peled et al., 1995). In a similar experiment, Sanders et al. (2000) observed an acute increase of 6 kg/d and a carry over response of 3.7 kg/d in 6X cows relative to 3X cows. In heifers, the acute response to 6X was lower in

magnitude (+1.7 kg/d), and no carry over effect was observed (Sanders et al., 2000).

**Duration (DIM) Parity 2X vs. 1X +** 

<sup>1971</sup>1 to 70 2+ (+) 1.2 kg/d (pers.a)

Walsh, 1974 1 to 100 2+ (+) 11.3% (acuteb)

<sup>1978</sup>1 to 56 2+ (+) 3.3 kg/d

Thomas et al., 1978 1 to 56 2+ (+) 1.68 kg/d (acute)

**suckle 2X vs. 2X + suckle 3X vs. 3X +** 

(no pers.)

1 (+) .87 kg/d (pers.)

(+) 7.7% (pers.)

**suckle** 

lactation.

Everitt and Phillips,

Moss and O'Grady,

**Reference Treatment** 

A summary of literature reports on the effect of suckling during early lactation on milk production is presented in Table 6. The results of subsequent experiments have further narrowed down the 'window' during early lactation wherein frequent milking can increase milk production for the remainder of lactation. Hale et al. (2003) assigned cows to 2X or to 4X for the first 3 wk of lactation, followed by 2X. Four times daily milking was associated with an acute increase of 8.8 kg/d and a carry over effect of 2.6 kg/d for the remainder of lactation. A treatment interval of 1 to 21 DIM was also used in a field study by Dahl et al. (2004b), who observed similar effects of frequent milking during early lactation. In contrast, VanBaale et al. (2005) assigned cows to 3X or 6X for the first 7, 14, or 21 d of lactation and reported that 6X did not increase milk production relative to 3X. Their observations were inconsistent with previous reports, and the authors speculated that facility logistics may have influenced their results because 6X cows were housed farther away from the milking parlor and spent a considerably longer time away from their pen than 3X cows (VanBaale et al., 2005). With the exception of one negative report (VanBaale et al., 2005), and one abstract (Fernandez et al., 2004), it is generally accepted that frequent milking increases milk yield, and that frequent milking or suckling during early lactation can increase milk production for the remainder of lactation (see Tables 5 and 6). The mechanistic basis for the milk yield response to frequent milking, however, is poorly understood. Even less understood are the mechanisms involved in the persistent effect on milk yield of frequent milking during early

**Table 6.** Summary of select literature reports on the effects of suckling during early lactation on milk yield of dairy cows
