Influence of Milking Frequency on Productive and Reproductive Efficiencies of Dairy Cows

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Abstract
Thirty-four mature Holstein cows were blocked into 2 groups on their 305-day, twice daily milked, mature equivalent milk-production of the previous lactation; groups were assigned at random to a twice or thrice daily milking frequency. In addition, 6 pairs of paternal half-sisters and 1 pair of nonsibling heifers also were assigned to twice daily or thrice daily milking frequency. Half-sisters were assigned to milking frequency on alternate calvings, and the nonsibling pair was assigned at random. Milk production peaked at 6 wk lactation in mature cows in both treatments, at 7 wk for cows in 1st lactation milked thrice daily and at 9 wk for cows in 1st lactation milked 3 times a day. Cows milked thrice daily reached higher peak milk production and were more persistent in milk production. Multiparous and 1st-lactation cows milked thrice daily produced 18.5 and 25.2% more milk than their counterparts milked twice daily, and after 15 wk heifers milked thrice daily were producing more milk per day than mature cows milked twice daily. The combined increased average production for cows and heifers milked thrice daily, 1299 kg, required only 92 kg more dry matter intake and resulted in an apparent preferential use of feed nutrients for milk production or higher rate of tissue catabolism in cows milked thrice daily. Milk composition was not influenced by milking frequency; total milk fat was 36 kg more for cows milked thrice daily. Reproductive performance measured as days to 1st estrus, days open or services per conception also was not influenced by milking frequency.