Effect of dry period protein feeding on post-partum milk production and composition

Abstract

Two experiments were carried out to investigate the effect of dry period supplementation with protein on milk production and composition in the subsequent early lactation period. In Experiment one, 87 Holstein/Friesian cows (including 18 first calvers) were blocked into groups of three on the basis of lactation number (first and second+) and expected calving date. Within each group, animals were randomly allocated to one of the following three pre-calving treatments (1) grass-silage ad libitum (S) (2) S+1 kg per day of fish-meal concentrate (0.5 kg fish-meal and 0.5 kg beet pulp and (3) S+1 kg per day of soyabean meal concentrate (0.75 kg soyabean meal +0.25 kg beet pulp). Only data from animals that were on the pre-calving treatments for a minimum of 28 days (18, 16 and 16 on Treatments 1, 2 and 3 respectively) were subjected to statistical analysis. Cow performance was measured for 12 weeks after calving. Milk yield, milk constituent yield or milk composition were not significantly affected by pre-calving treatment. In Experiment 2, 51 Holstein/Friesian cows of second lactation or greater were blocked into groups of three on the basis of lactation number and expected calving date. Within each group, animals were allocated randomly to one of the following three pre-calving treatments: (1) grass-silage ad libitum, (2) grass-silage/barley straw (0.8/0.2 DM basis), (restricted) and (3) grass-silage/barley straw (0.8/0.2 DM basis), (restricted) +1 kg/d of fishmeal concentrate. Cows on treatment 2 had a significantly lower body condition score close to calving ( P<0.05) than cows on Treatment 1 and gained significantly lower liveweight before calving ( P<0.05) compared to cows on Treatment 3. Treatment 2 also had a significantly lower DM intake than Treatment 1. Cow performance was measured for 8 weeks after calving. Only milk protein concentration and liveweight change were affected by the pre-calving treatment. Milk protein concentration was significantly lower in Treatment 2 ( P<0.05) compared to Treatments 1 and 3. Liveweight change was positive and significantly different ( P<0.01) in Treatment 2 compared to Treatments 1 and 3. It is concluded that milk yield and composition are not affected by dry period protein supplementation when grass-silage is the forage. Feeding restricted quantities of a silage/straw mixture in the dry period results in a lower milk protein concentration in early lactation compared to feeding grass-silage. Supplementing this forage mixture with undegradable protein increases milk protein concentration in early lactation to a level similar to that obtained when grass-silage is the dry period forage. Milk protein yield in early lactation is not affected by dry period protein supplementation.