There is evidence from a range of experiments of increases in milk production, including improvements in milk protein content, to additional dietary inclusions of low degradability ‘animal’ protein sources. This experiment was designed to examine the effect of stage of lactation on the response of dairy cows to increased dietary protein.

The continuous design experiment was conducted with 20 individually fed autumn calved dairy cows and four heifers over the first 26 weeks of lactation. The animals were fed initially a ‘standard diet’ of silage ad libitum and 8 kg (freshweight) of concentrate per day up to the 14th day of lactation. The cows were then allocated to four balanced groups of five cows (and one heifer) on the basis of lactation number, body weight and current milk yield. The data recorded during the first 14 days were used for subsequent covariance analysis.