Maize silage for the pasture-fed dairy cow. 2. A comparison between two systems for feeding silage while grazing perennial pastures in the spring

Abstract

Dairy cows in early lactation grazed irrigated perennial pastures in early spring and were offered 7-8 kg maize silage DM/day, either in the morning or throughout the entire day and night. Another group of cows with rumen fistulae were pen-fed annual pasture of similar quality and offered maize silage, again, in the morning only or throughout the day and night. Rumen retention time, diet digestibility, and excretion of maize grains were measured during the pen-feeding trial, as well as the rate of disappearance of feed samples from nylon bags placed in the rumen of each cow. Diurnal variations in rumen pH, total volatile fatty acids, and ammonia concentrations were monitored every 2 h. Intakes of grazed pasture, and diurnal variations in rumen pH and ammonia, were measured in the grazing cows. Milk yield and milk composition, and changes in liveweight and body condition (in the grazing cows only), were also monitored. Although time of feeding maize silage influenced rumen fermentation patterns in both pen-fed and grazing cows, it had little effect on feed intake and utilisation, or on milk production. This was attributed to the low levels of rumen-degradable starch in the maize silage, which would have had minimal influence on rumen cellulolytic activity. Therefore, unlike supplements of cereal grains, for which twice-daily feeding is recommended, maize silage need only be offered once daily without adversely affecting the performance of cows grazing high quality spring perennial pastures.