Fishmeal substituted for soybean meal fed at two TDN levels for lactating dairy cows

Thirty multiparous Holstein and twelve multiparous Jersey cows were used to determine the effect of diets (3x2 factorial) containing 0,1,2 kg of fish meal (FM) and energy levels of 70 and 75% TDN on milk production and composition. Basal diets contained 83% corn silage and 10.3% concentrate for the 70% TDN ration and 60% corn silage, 10.3% concentrate and 24.5% high moisture corn for the 75% rations. High moisture corn in the higher TDN diets decreased both acid and neutral detergent fiber, and increased dry matter content. Nitrogen degradability was lower in the higher TDN rations and decreased with increasing fishmeal levels. Dry matter degradability tended to be similar for all diets. Milk and FCM production was similar for all diets. Milk fat percentage was similar for TDN levels but decreased as fishmeal level increased. Milk protein percentage increased with 75% TDN but was not affected by fishmeal. Kilograms of milk protein produced followed a trend similar to milk protein percentage. Dry matter intake was higher with higher TDN diets, but tended to be lower during the first 4 weeks of the study with increasing levels of fishmeal. Bodyweight fluctuated during the experiment and followed a pattern similar to dry matter intake. Blood plasma urea concentration was similar for all diets.