Effects on milk production of feeding silage and sugar-beet pulp as separate components, in a mixed ration or as an ensiled blend

Twenty early-lactation British Friesian dairy cows were used in a five-treatment, partially balanced change-over design experiment, consisting of four periods each of 4 weeks' duration. Three treatments consisted of offering ensiled blends of silage and sugar-beet pulp produced by mixing 40 (S40), 80 (S80) and 120 (S120)kg beet pulp t^?1 herbage at ensiling. In two further treatments, an untreated silage was supplemented with 5 kg of beet pulp daily, either mixed with the silage prior to feeding (SM) or offered in two equal feeds each day (ST). Silage was offered ad libitum in all treatments, while in addition all cows received 1 kg d^?1 of a concentrate supplement containing 470 g crude protein kg^?1 fresh weight. Dry-matter intakes and milk fat + protein yields increased with increasing level of beet pulp inclusion in the diet, irrespective of whether it was offered in the form of an ensiled blend or as a supplement to an untreated silage. With the exception of D-value (digestible organic matter in the dry matter), which was significantly higher with treatments SM and ST than with the ensiled blend treatment (S80), no significant differences were identified in total ration digestibility or in the efficiency of nitrogen or energy utilization between methods of beet pulp inclusion in the diet. However, offering beet pulp in the form of an ensiled blend reduced the acetate/propionate ratio in rumen fluid compared with offering best pulp as a supplement to an untreated silage. When account is taken of differences in the efficiency of recovery of edible silage dry matter between ensilage systems and of differences in dry-matter intakes between treatments, total milk fat + protein outputs per 10000 kg herbage dry matter ensiled were 55 (s.e. 50·9) and 78 (s.e. 47·5) kg lower when equal quantities of beet pulp were offered as part of an ensiled blend rather than as a supplement to an untreated silage, as in treatments SM and ST respectively. However, these differences were non-significant. Alternatively, in order to produce an equal milk output from ensiling a given quantity of herbage, 12·5 and 16·2% more beet pulp would have been required if the beet pulp had been mixed with the herbage at ensiling, rather than offered as a supplement, as in treatments SM and ST respectively.