Influence of supplemental aminooligosaccharides on in vitro disappearance of diets for dairy cattle and its effects on milk yield

Two experiments were conducted to evaluate the influence of supplemental aminooligosaccharides (AOS) on the disappearance and fermentation of diets for lactating cows, and its effects on milk yield and quality. In the first study, diets containing 0 or 0.2% AOS (dry matter basis) were incubated for 24, 48 and 72 h with ruminal fluid to evaluate the in vitro dry matter disappearance (IVDMD) and fermentation characteristics. The addition of AOS improved IVDMD of diets, induced higher total bacterial and cellulolytic bacterial counts and decreased the number of bacteria that produce lactate compared to the control. At 24 h incubation, AOS increased volatile fatty acid concentrations and the molar proportion of propionate, though at 48 and 72 h incubation AOS did not affect the fermentation characteristics of the diets. In a further experiment, milk yield and milk quality were evaluated using 50 Holstein dairy cows (193 days in milk). Cows were randomly assigned to the diets tested in the in vitro study. Feed intake was not modified by AOS. Milk yield of cows fed AOS was significantly higher than that of cows not supplemented. Because AOS tended to decrease the percentage of fat in milk, fat and solid-corrected milk content were similar for the two treatments. Percentage and yield of non-fat solids, protein and lactose, and the somatic cell count in milk were not affected by AOS. The milk urea-N concentration of the cows fed AOS was lower than of those not supplemented. Supplementing AOS enhanced the disappearance and fermentation characteristics of the diet. Further studies with cows earlier in lactation are necessary to evaluate the effects of AOS on milk yield and milk components.