Effects of inclusion of a blended protein product in 35 dairy herds in five regions of the country

We assessed the change in milk production in 35 dairy herds located in eigh t states when a blended animal-marine protein product was included in diets at 2 (22 herds) to 4% (13 herds) of dry matter. Average 305-d production a cross herds was 8844.1 kg (SEM = 153.7 kg) of milk, with a range of 6876.9 to 11,293.2 kg. The mean days in milk for all herds at initiation of the tr ial was 118.8 d (SEM = 3.7, herd mean range of 68.8 to 160.0 d), and the av erage daily milk production was 32.6 kg (SEM = 0.6 kg, range 24.2 to 39.6 k g). The animal-marine protein blend was included in herd rations for 30 d, beginning immediately after a DHI herd test month and ending immediately af ter the next DHI sample test. Cow milk records were collected for 1 to 2 mo before the protein blend was included and for 2 to 3 mo after the protein was removed. Sample days were assigned a dummy variable to indicate months off or on the animal-marine protein blend. A total of 33,190 milk records f rom 7135 cows were analyzed. The numbers within herd ranged from 35 to 2012 cows. Of the 35 herds, 19 were classed as having increased milk yield, 12 herds as having no change, and 4 herds as having decreased milk yield when the animal-marine protein blend was included in the diet. The population me an for change in milk yield with the inclusion of the animal-marine protein blend was 1.24 kg/d of milk (SEM = 0.05 kg). There was no significant effe ct of parity on mean response. Milk protein content was not influenced by a nimal-marine protein blend inclusion. Fat content was lower for the month o n which the animal-marine protein blend was fed (3.51%) compared with the m onth prior (3.63%) and the month after (3.70%), respectively (SEM = 0.032). Stage of lactation influenced the method for calculating the production re sponse and the actual response to the animal-marine protein blend.