Supplementation of β-mannanase (CTCZYME) to lactating dairy cattle diets improves feed conversion efficiency and somatic cell count

Abstract Text: Improving feed conversion efficiency (FCE) and health status of animals has economic and environmental benefit in dairy operations. Fibrolytic enzymes such as mannanases may improve nutrient digestion and utilization by releasing compounds contained within non-structural carbohydrates such as mannan and xylan, and may also help immune status. A trial was conducted to investigate the effects of β-mannanase supplementation on nutrient digestibility, FCE, and enteric methane emissions in lactating dairy cows. Twelve post peak-lactation multiparous Holstein cows producing 45.5± 6.6 kg/d milk at 116± 19.0 DIM were randomly allocated to one of 3 treatments in a 3×3 Latin square design with 3 18-d periods. Cows were fed the same basal diet with treatment 1 used as control and treatments 2 and 3 contained β-mannanase supplementation at 0.1% (low supplement [LS]), or 0.2% (high supplement [HS]) of DM. Effects of β-mannanase supplementation on nutrient intake and utilization, milk production efficiency, BW change, and methane emissions were determined using the MIXED procedure of SAS (version 9.4). Supplementation of β-mannanase enzyme did not affect DMI, milk yield, and milk composition. Somatic cell counts in milk was lower (P=0.023) for cows fed the LS diet compared to cows fed control and HS diets. Methane yield (per unit of DMI) and intensity (per unit of milk yield or milk protein yield) were not affected by β-mannanase supplementation. Cows fed LS diet had lower DM, OM, and CP digestibility compared to cows fed control and HS diets. Starch, NDF, and ADF digestibility were not affected. Cows fed LS significantly improved (P<0.05) FCE, BW gain, and efficiency of converting dietary N to milk protein compared to cows fed the control diet. β-mannanase supplementation had no effect on N excreted in feces and urine. Dietary supplementation of β-mannanase can improve FCE, BW gain, and udder health of mid-lactating dairy cows without affecting methane emissions and manure N excretions. The role of β-mannanase supplementation may be more critical for early lactating cows, which are generally under significant metabolic and immune challenges and more likely to be in negative energy balance.

Keywords: dairy, feed efficiency, b-mannanase