Fibrolytic enzymes could boost dairy cow efficiency

Dairy cows fed barley silage may see a boost to milk production efficiency when fibrolytic enzymes are added to feeds, say researchers.

An international group of researchers from Canada, South Korea and Egypt explored the use of fibrolytic enzymes (FETR) as an additive to dairy cow rations and its potential to influence lactation, feeding behavior and digestibility when used with a barley silage-based diet.

“This study aimed to evaluate the effects of supplementing a fibrolytic enzyme product applied directly to a barley silage–based diet fed to dairy cows during mid-lactation on milk yield, milk composition, nutrient intake and digestibility, and feeding behavior,”​ the researchers said.

During the feeding trials, the researchers found that there was no influence on feeding behavior from use of the enzyme, but it did improve feed efficiency and milk protein amounts. “Pretreating dairy cow barley-based TMR with FETR improved dairy cow performance during the mid-lactation phase,”​ they added.

“Based on the current study, the optimum dosage of the fibrolytic enzymes was 0.75 mL of FETR/kg DM of TMR [total mixed ration],” ​they said. “Applying this dosage improved NDF [neutral detergent fiber] digestibility, fat yield, FCM [fat corrected milk] yield, and feed efficiency of dairy cows fed a diet containing 34% barley silage (DM basis).”​

Why fibrolytic enzymes with barley silage?​

Dairy cows have the ability to transform forage into milk and protein products for human use, the researchers said. However, the rate and amount of forage digestion cows make is lower than when they are fed concentrates – limiting feed intake and cow performance.

It is important to boost forage digestibility to improve milk production, they said.

Fibrolytic enzymes can be added as feed additive in ruminant diets to improve forage fiber digestion and support increased milk production in cows, they said. enzyme use also has been linked to improved digestibility of dry matter (DM) and neutral detergent fiber (NDF).

“However, there are inconsistent results regarding the effect of providing fibrolytic enzymes to ruminant diets on dairy cow performance (Bernard et al., 2010; Chung et al., 2012; Dean et al., 2013),” ​they said. “Thus, the use of fibrolytic enzymes as feed additives has not yet been extensively adopted in commercial dairy farms.”​

As feed costs can vary, however, it remains important to “refine”​ enzyme use as feed additives to increase feed efficiency and lower the price of milk production, the researchers said.

In western Canada, whole-crop barley can be a main forage element for dairy and beef rations, they said.

Previously, three barley forage varieties were examined for their in vitro NDF digestibility to examine use of the forage with beef cattle, they said. “From the results of this study, it was found that all barley varieties, despite differences in NDF digestibility, have a similar effect on feed efficiency,”​ they added.

It was also noted that other factors also altered forage digestibility and quality, the researchers said. The range of nutritional quality for forage barley indicates that additional additives – like “fibrolytic enzyme products with high activity (xylanase and cellulase)”​ – may be needed to improve the digestibility of barley silage.

However, there is little information available on milk production response in cows when a fibrolytic enzyme is added to their barley silage-based ration, they said.

Methods and materials​

Prior to the feeding trial an in vitro examination was conducted to establish if adding fibrolytic enzymes would alter animal performance when used with a barley silage-based diet, the researchers said. The enzyme was tested on barley silage samples at six levels – 0, 0.25, 0.50. 0.75, 1 and 1.25 mL of FERT/kg DM of silage – and the gas generated was measured.

In the feeding trial, eight cows were given one of four diets for a period of 22 days, before being rotated to another of the trial diets, the researchers said. Each period on diet included a 16-day adjustment window and 6 days for sampling.

The diets included a total mixed ration (TMR) with 34.1% barley silage, 16.1% alfalfa hay, 19.7% barley grain and 30.1% concentrate on a DM basis and that diet was supplemented with 0, 0.5, 0.75 or 1mL of FETR/kg dry matter (DM), they said. The enzyme pretreatment was added to the feed during the mixing process.

Feed intake, feeding behavior and milk yield were noted daily during the 6-day period and milk samples were collected for the final three days and checked for milk fat, protein, lactose, MUN and TS, they said. TMR, ort and fecal samples also were gathered for analysis and to determine total tract digestibility of DM, organic matter, NDF and potentially digestible NDF.

Results​

In a pre-feeding trial in vitro test, adding the enzyme linearly increased digestibility of dry matter and appeared to improve the digestion of barley silages, the researchers said. There also was a linear effect on the digestibility of in vitro NDF digestibility.  

Adding the enzyme to cow rations did not alter the intake of DM, OM or NDF, they said. “The response of DM, OM, and NDF digestibility to the increasing level of FETR was cubic, where the intermediate dosage (0.75 mL of FETR/kg DM of TMR) has exhibited the best effect on nutrient digestibility,”​ they added.

“Pretreating dairy cow barley silage–based diet with 0.75 mL of FETR/kg of TMR increased the milk production efficiency of dairy cows fed diets containing 34% barley silage (DM basis),”​ they said. “The positive effect of adding FETR could benefit the dairy industry in western Canada, where barley silage-based diets are common.”​

The additive improved FCM and energy-corrected milk, with the highest levels found when 0.75 of the enzyme/kg was added to the TMR, the researchers said. Milk fat yield also increased, however the highest amount of enzyme tended to lower milk fat yield.

Milk protein composition increased linearly as more enzyme was added but yield did not, they said. The 0.75 diet also was found to generate the best milk lactose percentage, the best feed efficiency and a higher FCM yield. However, MUN was not altered.

“These findings indicate that supplementing the forage with moderate enzyme levels could enhance dairy cow performance,”​ they said. 

Source: Journal of Dairy Science​

Authors: B Refat, D Christensen, J McKinnon, W Yang, A Beattie, T McAllister, J-Su Eun, G Abdel-Rahman, P Yu