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Effect of DL-malic acid supplementation on feed intake, methane emission, and rumen fermentation in beef cattle

UCD School of Agriculture, Food Science and Veterinary Medicine, University College Dublin, Lyons Research Farm, Newcastle, Co. Dublin, Ireland

pfoley{at}ucdconnect.ie

Abstract

The objective of this study was to determine the effect of dietary concentration of DL-malic acid (MA) on DMI, methane (CH₄) emission, and rumen fermentation in beef cattle. Two Latin square experiments were conducted. In Exp. 1, 6 beef heifers (19 ± 1 mo old) were assigned in a duplicated Latin square to 1 of 3 dietary concentrations of MA on a DMI basis (0%, MA-0; 3.75%, MA-3.75; or 7.5%, MA-7.5) over 3 periods. In Exp. 2, 4 rumen-fistulated steers (48 ± 1 mo old) were assigned to 1 of 4 dietary concentrations of MA (0%, MA-0; 2.5%, MA-2.5; 5.0%, MA-5.0; or 7.5%, MA-7.5) on a DMI basis, over 4 periods. Both experimental diets consisted of grass silage and pelleted concentrate (containing MA). Silage was fed for ad libitum intake once daily (a.m.), whereas concentrate was fed twice daily (a.m. and p.m.) with the aim of achieving a total DMI of 40:60 silage:concentrate. In both Exp. 1 and 2, experimental periods consisted of 28 d incorporating a 13-d acclimatization, a 5-d measurement period, and a 10-d washout period. In Exp. 1, enteric CH₄, feed apparent digestibility, and feed intake were measured over the 5-d measurement period. In Exp. 2, rumen fluid was collected on d 16 to 18, immediately before (a.m.) feeding and 2, 4, 6, and 8 h thereafter. Rumen pH was determined and samples taken for protozoa count, VFA, and ammonia analysis. Enteric CH₄ emissions were estimated using the sulfur hexafluoride (SF₆) tracer technique and feed apparent digestibility using chromic oxide as an external marker for fecal output. In Exp. 1, increasing dietary MA led to a linear decrease in total DMI (P < 0.001) and total daily CH₄ emissions (P < 0.001). Compared to the control diet, the greatest concentration of MA decreased total daily CH₄ emissions by 16%, which corresponded to a 9% reduction per unit of DMI. Similarly in Exp. 2, inclusion of MA reduced DMI in a linear (P = 0.002) and quadratic (P < 0.001) fashion. Increasing dietary MA led to a linear decrease in molar proportion of acetic (P = 0.004) and butyric acids (P < 0.001), and an increase in propionic acid (P < 0.001). Ruminal pH tended to increase (P = 0.10) with increasing dietary MA. Dietary inclusion of MA led to a linear (P = 0.01) decrease in protozoa numbers. Increasing supplementation with MA decreased CH₄ emissions, but DMI was also decreased, which could have potentially negative effects on animal performance.

Key Words: beef cattle • DL-malic acid • methane • rumen

This article has been cited by other articles:

				P. A. Foley, D. A. Kenny, D. K. Lovett, J. J. Callan, T. M. Boland, and F. P. O'Mara Effect of DL-malic acid supplementation on feed intake, methane emissions, and performance of lactating dairy cows at pasture J Dairy Sci, July 1, 2009; 92(7): 3258 - 3264. [Abstract] [Full Text] [PDF]