Performance of dairy cows fed normal- or reduced-starch diets supplemented with an exogenous enzyme preparation

Abstract

The objective of this study was to investigate the effects of supplementation of an exogenous enzyme preparation (EEP) on performance, total-tract digestibility of nutrients, plasma AA profile, and milk fatty acids composition in lactating dairy cows fed a reduced-starch diet compared with a normal-starch diet (i.e., positive control). Forty-eight Holstein cows (28 primiparous and 20 multiparous) were enrolled in a 10-wk randomized complete block design experiment with 16 cows per treatment. Treatments were as follows: (1) normal-starch diet (control) containing (% dry matter basis) 24.8% starch and 33.0% neutral detergent fiber (NDF), (2) reduced-starch diet (RSD) containing 18.4% starch and 39.1% NDF, or (3) RSD supplemented with 10 g/cow per day of an EEP (ENZ). The EEP contained amylolytic and fibrolytic activities and was top-dressed on the total mixed ration at the time of feeding. Compared with normal-starch diet, dry matter intake and milk and energy-corrected milk (ECM) yields were lower (on average by 7.1, 9.5, and 7.2%, respectively) for cows on the RSD treatments. Concentrations, but not yields, of milk fat and total solids were increased by RSD. Energy-corrected milk feed efficiency did not differ among treatments. Totaltract digestibility of NDF tended to increase by RSD treatments. Plasma AA concentrations were not affected by treatment, except that of 3-methylhistidine was increased by ENZ, compared with RSD. Blood glucose concentration tended to be lower in cows on the RSD treatments, but ENZ increased glucose and tended to increase insulin concentrations at 4 h after feeding when compared with RSD. Cows on the RSD treatments had decreased concentrations of de novo fatty acids and tended to have increased concentrations of preformed fatty acids in milk. Overall, decreasing dietary starch concentration by 26% decreased dry matter intake, milk, and ECM yields, but ECM feed efficiency was not different among treatments. The negative effects of reducing dietary starch on production were not attenuated by the EEP.

Effects of an exogenous enzyme preparation extracted from a mixed culture of Aspergillus spp. on lactational performance, metabolism, and digestibility in primiparous and multiparous cows

“…Because plasma glucose concentration did not differ between treatments in the current study, it is plausible to infer that supplementation with ENZ resulted in greater utilization of glucose by the mammary gland (e.g., increased milk lactose content for ENZ compared with CON). Dietary factors such as starch and NDF concentrations (Silvestre et al, 2022) and the type of forage (Yang et al, 2019) can also influence responses in cows fed diets supplemented with enzyme preparations. For instance, Silvestre et al (2022) hypothesized that supplementing a reduced-starch diet (i.e., a 26% reduction in dietary starch concentration by substitution of ground corn with wheat straw) with the same enzyme preparation as that used in the current study would compensate the deficit of energy compared with a normal-starch diet.…”

“…Dietary factors such as starch and NDF concentrations (Silvestre et al, 2022) and the type of forage (Yang et al, 2019) can also influence responses in cows fed diets supplemented with enzyme preparations. For instance, Silvestre et al (2022) hypothesized that supplementing a reduced-starch diet (i.e., a 26% reduction in dietary starch concentration by substitution of ground corn with wheat straw) with the same enzyme preparation as that used in the current study would compensate the deficit of energy compared with a normal-starch diet. Although the enzyme supplementation in the reduced-starch diet increased postprandial blood glucose concentration, cows were not able to maintain the same DMI and milk production levels as cows fed a normal-starch diet, even though feed efficiency was not affected by treatments (Silvestre et al, 2022).…”

“…6 Unaccounted N = N intake -(urinary N + fecal N + milk N). presentation (Weiss et al, 2011), stage of lactation (Beauchemin et al, 2003), and interaction with dietary nutrients (Tirado-González et al, 2018;Silvestre et al, 2022) have all been shown to affect responses to exogenous enzyme supplementation. In addition, parity should be considered as a factor when using exogenous enzyme additives in the diet of dairy cows, as reported in the current study.…”

“…However, improvements in lactational performance of dairy cows fed diets supplemented with A. oryzae were either small or not evident in recent (Zilio et al, 2019;Vittorazzi et al, 2021) and older (Kellems et al, 1990;Sievert and Shaver, 1993;Higginbotham et al, 1994) studies. Supplementation of diets with Aspergillus niger extracts alone has not been investigated, and only 2 studies (Oh et al, 2019;Silvestre et al, 2022) have evaluated the effects of a combination of A. niger and A. oryzae on lactational performance of dairy cows. Oh et al (2019) reported increased total VFA concentration and Silvestre et al (2022) suggested increased postprandial blood glucose concentration in cows fed a reduced-starch diet supplemented with A. oryzae and A. niger.…”

“…Supplementation of diets with Aspergillus niger extracts alone has not been investigated, and only 2 studies (Oh et al, 2019;Silvestre et al, 2022) have evaluated the effects of a combination of A. niger and A. oryzae on lactational performance of dairy cows. Oh et al (2019) reported increased total VFA concentration and Silvestre et al (2022) suggested increased postprandial blood glucose concentration in cows fed a reduced-starch diet supplemented with A. oryzae and A. niger. The effects of A. oryzae and A. niger on total-tract digestibility of nutrients and lactational performance of the cows were either small or not evident in the latter 2 studies.…”