Fibrolytic enzyme and aerobic stability of diets for dairy cows

Abstract

The use of exogenous enzymes and organic acids applied to TMR can increase feed intake and digestibility for ruminants improving feed efficiency. The first experiment evaluated the effect of an enzyme preparation with cellulase and xylanase activities on lactation performance, feed efficiency, diet digestibility, ruminal fermentation of dairy cows fed a corn silage diet. Twenty-eight Holstein cows were individually fed for 56 d. The treatments were control (CTL) or enzyme (ENZ. 0.75 mL/kg of dry matter in the diet). DMI (21.0 kg/d), NDF (46.1%) and starch (93.6%) digestibility, milk production (26.3 kg/d) and the milk/DMI ratio (1.34) did not differ. The molar ratio of propionate to be reduced (19.7 vs. 18.5%) in the ENZ, inducing a trend towards an increase in the acetate to propionate ratio (3.59 vs. 3.29). ENZ tended to increase milk fat concentration, increased milk protein concentration at weeks 6 and 8, and increased milk solids concentration. ENZ increased milk N-urea at week 3 and tended to increase plasma N-urea, suggesting protease activity. ENZ had no effect on fiber digestibility and feed efficiency but had an effect on rumen fermentation profile and increased milk solids concentration. In the second and third experiments, the effects of commercial products based on organic acids on the aerobic stability of a TMR based on corn silage were evaluated. In experiment 2 the treatments were: Control (CTL), calcium propionate at 1 (PC1), 1.5 (PC1.5) or 2 (PC2) kg/ton, and Fresh Cut Plus (acetic, benzoic and propionic acids, ammonium hydroxide, polysorbate) at 1 (FC1), 1.5 (FC1.5) or 2 (FC2) L/ton. Treatments were mixed with 5 kg of TMR and placed in 6 buckets kept in a controlled environment room (29.1 ± 1.7 °C) for 48 h. The maximum temperature (46.7 ºC) and aerobic stability were not different for the treatments. The treatments FC1.5 (32.4 ºC) and FC2 (32.2 ºC) reduced the temperature from 0-24 h of TMR in relation to CTL (34.8 ºC). The additives did not affect (P ≥ 0.63) the temperature of 24-48 h (44.4 ºC). Counts (log cfu/g) of aerobic and spore-forming bacteria were reduced by CP2 (4.77 vs. 4.11) and FC1.5 (3.86 vs. 3.27). Yeast counts tended to be reduced in FC1 (0.98 vs 2.71). The filamentous fungi count was reduced by PC2 (1.59), FC1 (1.37), FC1.5 (1.07) and FC2 (1.73) in relation to the control. The FC product was more efficient in reducing the 0-24 h TMR temperature and microbial growth than the PC product. The use of exogenous enzymes can improve the feeding efficiency of dairy cows and the stabilizer FC1,5 and FC2 reduced the TMR temperature from 0 to 24 h and was more inhibitory to microbial growth than the PC product.