A comparison of textured versus pelleted concentrates on rumen degradability, dry matter intake, milk yield and composition in lactating Holstein cows

Abstract

A study was undertaken to compare the feeding of a ground-pelleted concentrate mixture with a textured one. Parameters studied were in situ rumen degradability characteristics of the concentrates, dry matter intake and yield of milk and milk components. A concentrate mixture consisting of barley, corn, canola meal and a vitamin-mineral premix was manufactured in two forms. In the one form, all ingredients were ground and pelleted while in the second, only the canola meal and premix were pelleted while the corn and barley were steam rolled prior to mixing. Initially the degradability characteristics and digestive tract disappearance of the two concentrates were determined in an in situ trial using two non-lactating Holstein cows fitted with rumen and duodenal cannulae. Nylon bags containing 2–3 g of material were prepared in quadruplicate (two replicates per cow per incubation time) and incubated in reverse order 72, 48, 24, 12, 8, 4, 2 and 0 h for each concentrate. Total intestinal disappearance was determined using the mobile nylon bag procedure. The results of the in situ trial indicated that the degradable fraction b of the dry matter was greater for the textured compared with the pelleted form (34.7 vs. 31.2%) while effective degradability of the dry matter was higher for the pelleted form (74.5 vs. 68.0%). Total tract disappearance of the dry matter and protein fractions were not influenced by form of concentrate but rumen disappearance of crude protein was higher for the pelleted form (70.4 vs. 64.2%). The feeding trial employed 14 lactating Holstein cows fed a forage mixture consisting of corn silage and grass silage. Milk and milk protein yields and protein content of the milk were higher, while milk fat content was lower, for cows fed the pelleted compared with those fed the textured concentrate. Rumen pH (6.79 vs. 6.58) was lower for cows fed the pelleted compared with the textured concentrate. There was, however, no effect of form of concentrate on concentrations of volatile fatty acids in the rumen fluid. Form of concentrate fed did not influence dry matter intake but in terms of net energy (Mcal NEL) the diet containing the pelleted concentrate tended to have a higher energy value than the diet containing the textured concentrate (1.76 vs. 1.66 Mcal NEL kg DMI−1). The marked difference in the ratio of milk fat to milk protein, 1.14 vs. 1.29 for pelleted and textured concentrates, respectively, coupled with the impact on rumen degradability characteristics indicated that minor differences in processing can have an impact on product yield from the milk and the efficiency of utilization of the diet. Key words: Textured versus pelleted concentrate, degradability, lactating cows