Effects of Dietary Amino Acid Balance on the Response of Dairy Cows to an Increase of Milking Frequency from Twice to Three Times Daily

Abstract

An experiment was conducted to examine how the response of dairy cows to a change from twice to three times-daily milking is affected by deficiencies in the dietary supplies of three amino acids, His, Met, and Lys. Six cows were used in a 6 x 6 Latin square with 14-d periods. The three dietary treatments were: grass silage and a cereal-based supplement containing feather meal as the sole protein supplement; the same silage-cereal diet supplying similar amounts of metabolizable and rumen-undegradable protein but with additional amounts of His, Met, and Lys in the form of fish meal; and the fish meal diet with additional metabolizable energy in the form of an additional 2 kg/d of sugar beet pulp. Within each of these dietary treatments, the cows were milked twice and three times daily, making a total of six treatments. When cows were given the feather meal diet, even though dietary metabolizable energy was in considerable excess, a deficiency of specific amino acids prevented any increase in milk yield in response to increasing the frequency of milking from twice to three times daily. In contrast, when cows consumed a similar level of excess metabolizable energy and a similar level of rumen-undegradable protein for which the protein was of better amino acid balance (fish meal), the increased frequency of milking led to increased yield of milk and milk protein.

Temporary alterations to postpartum milking frequency affect whole-lactation milk production and the energy status of pasture-grazed dairy cows

“…Therefore, this greater body fat mobilization was not sustained in cows genetically selected for pasture-based systems, perhaps as a protective mechanism against excessive BCS loss during early lactation, which is undesirable to maintain an annual, seasonally concentrated breeding cycle. This effect may explain the relatively small increases in milk yield and the lack of increases in milk component yields, and indicates that extra energy than was offered must be supplied to achieve better production responses to increased MF (Andersen et al, 2003;Yeo et al, 2003).…”