The effect of an exogenous amylase on performance and total-tract digestibility in lactating dairy cows fed a high-byproduct diet

Abstract

The objective of this experiment was to determine the performance and digestibility response of lactating dairy cows fed a reduced-starch diet containing a commercial amylase product. Treatments consisted of a normal-starch total mixed ration (NS-), a reduced-starch total mixed ration (RS-), and a reduced-starch total mixed ration with exogenous amylase (RS+) added to the concentrate. Treatments were assigned according to a replicated 3 × 3 Latin square design with 28-d periods. Twenty-three cows completed the study. Starch concentrations in NS-, RS-, and RS+ total mixed rations were 27.7, 23.5, and 22.7%, respectively. Effects of treatment on intake, milk production, milk composition, and total-tract apparent nutrient digestibility were evaluated during the last week of each period. Effects of amylase on in vitro starch digestibility of the NS- and RS- grain mixes were also measured. We hypothesized that the reduction in dietary starch in the RS- ration would decrease diet digestibility and limit milk production compared with NS- due to a decrease in available energy, and that RS+ would alleviate some of this decrease by increasing nutrient digestibility. Contrary to this hypothesis, the RS- diet did not affect intake or milk production relative to the NS- diet, except for increased milk urea nitrogen and a tendency for a decrease in milk protein yield. This lack of response is attributed to both low milk fat concentrations across treatments and greater than predicted dietary energy content preventing the energy deficit that was intended to occur with the reduced-starch rations. Cows fed the RS+ ration had the lowest production performance, with reduced milk, fat-corrected milk, protein, and lactose yields relative to cows fed NS-. Cows fed RS+ also had reduced lactose yield and tended to have reduced milk and fat-corrected milk relative to cows fed RS-. Despite the negative effects of the RS+ treatment on performance, exogenous amylase did increase both in vitro and in vivo measurements of digestibility. Although amylase increased nutrient digestibility, this did not translate into improved milk performance, likely due to the relatively high energy content of experimental diets compared with cow requirements.

Effects of exogenous amylase on the in vitro digestion kinetics of whole‐crop maize silages made from flint or dent grain type at different phenological stages grown in tropical condition

“…The increase in V 1 , V 2, C 1 and C 2 with amylase inclusion indicates higher digestibility of both non-fibrous and fibrous fractions of silage, which strengthens the occurrence of cross-feeding interaction among the micro-organisms. Similarly, amylase supplementation increased the total NDF digestibility when evaluated in vivo (Gencoglu et al, 2010;Mccarthy et al, 2013). Contrary to our study, others did not found effect of addition of the exogenous amylase on NDF digestibility for dairy cows (Andreazzi et al, 2018;Zilio et al, 2019).…”

“…(2016) observed that amylase decreased lag time and increased rate and amount of gas production. This effect of amylase is due to the greater hydrolysis of starch (Nozière et al, 2014) providing substrates for the multiplication of other microbial species, mainly fibrolytic micro-organisms (Mccarthy, Engstrom, Azem, & Gressley, 2013), a process defined as cross-feeding among rumen micro-organisms (Russell, 1985) that can improve fibre digestibility by increase in fibre digestion rate as shown in our study.…”

“…Similarly, amylase supplementation increased the total NDF digestibility when evaluated in vivo (Gencoglu et al, 2010;Mccarthy et al, 2013). Similarly, amylase supplementation increased the total NDF digestibility when evaluated in vivo (Gencoglu et al, 2010;Mccarthy et al, 2013).…”

“…This hydrolysis occurs through the cleavage of the α-1.4 and α-1.6 bonds of the starch granules (Tricarico, Johnston, & Dawson, 2008). This effect of amylase is due to the greater hydrolysis of starch (Nozière et al, 2014) providing substrates for the multiplication of other microbial species, mainly fibrolytic micro-organisms (Mccarthy, Engstrom, Azem, & Gressley, 2013), a process defined as cross-feeding among rumen micro-organisms (Russell, 1985) that can improve fibre digestibility by increase in fibre digestion rate as shown in our study. Likewise, Gallo et al (2016) observed that amylase decreased lag time and increased rate and amount of gas production.…”

Exogenous Enzymes in Ruminant Nutrition: A Review

“…Early research attempts on supplementation ruminant diet with exogenous enzymes has a considerable long history which took place in 1960's, mainly considering the amylolytic (McCarthy et al, 2013) and proteolytic (Vera et al, 2012) enzymes. But the inconsistency of the obtained results, less knowledge on mode of action of enzymes and the high production cost of enzymes hindered the further development of this field.…”