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The effects of incomplete milking and increased milking frequency on milk production rate and milk composition

Increased milking frequency and incomplete milking have differential effects on milk yield and mammary gland physiology that are important for optimization of milking prac-tices in dairy herds. The objectives of this experi-ment were to determine the effects of increased milking frequency and incomplete milking on milk production rate (MPR) and milk compos-ition and to determine if milking 3 times daily (3×) could rescue the negative production effects of incomplete milking. Twenty-two multiparous cows were enrolled onto this experiment begin-ning at 5 days in milk (DIM) and continuing through 47 DIM. A split-plot design was used to randomize the 2 treatments, which were milking frequency and incomplete milking. Eleven cows were randomly assigned to be milked 2 times (2×) daily and 11 cows were randomly assigned to be milked 3×. Within each cow, a contralat-eral half-udder was randomly assigned to be in-completely milked (30% milk remaining in the gland ; IM), and the other half-udder was ran-domly assigned to be milked completely (CM). Quarter-level milk yields were recorded at each milking session. Milk samples from all quarters were collected twice weekly at the beginning of the morning milking for analysis. Cows milked 2× tended to have reduced MPR compared with 3× milked cows (1.81 ± 0.06 vs. 1.97 ± 0.06 kg milk/h ; P = 0.06). Half-udders that were CM and IM produced 1.09 ± 0.03 and 0.80 ± 0.03 kg milk/h, respectively. There was an interaction between incomplete milking treatment and week of lactation (P = 0.04). No interaction was de-tected between milking frequency and incom-plete milking for MPR or milk components. Cows milked 3× had increased milk fat percent (1.93 ± 0.09% vs. 1.65 ± 0.09%, P = 0.047), de- creased milk lactose percent (4.80 ± 0.04% vs. 4.93 ± 0.04%, P = 0.04), and exhibited no dif- ferences in milk protein percent or milk somatic cell count (SCC) compared with cows milked 2×. Half-udders that were IM had increased milk fat percent (2.15 ± 0.07% vs. 1.43 ± 0.07%, P < 0.0001), decreased lactose percent (4.75 ± 0.03% vs. 4.99 ± 0.03%, P < 0.0001), increased milk log10SCC (4.22 ± 0.05 vs. 4.41 ± 0.05, P = 0.0004), and no differences in milk protein percent compared with CM half-udders. These results indicate that a 3× milking frequency in IM half-udders was not able to improve milk production compared with IM half-udders milked 2×. Our results indicate that 30% milk re-maining in the gland had an irreversible impact on milk yield as increased milking frequency was not able to reverse the milk yield lost.

incomplete milking, increased milking frequency, milk composition, milk production rate

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