Journal of Animal Science, Vol 78, Issue 8 2072-2080, Copyright © 2000 by American Society of Animal Science

JOURNAL ARTICLE

Interaction of dietary magnesium level on the feeding value of supplemental fat in finishing diets for feedlot steers

J. E. Ramirez and R. A. Zinn
Desert Research and Extension Center, University of California, El Centro 92243, USA.

A feeding trial involving 160 crossbred steers (357 kg) and a metabolism trial involving eight Holstein steers (189 kg) cannulated in the rumen and proximal duodenum were conducted to evaluate the interaction of dietary Mg level (.18 vs .32%, DM basis) and supplemental fat (0% supplemental fat vs 4% tallow [T], yellow grease [YG], or griddle grease [GG]) on growth performance and NE value of the diet. Dietary Mg level did not influence (P > .10) growth performance. Daily weight gain was lower (11%, P < .05) for steers fed GG than for those fed YG. Supplemental fat decreased (5%, P < .10) DMI and increased (P < .05) gain efficiency (7%). There was a fat x Mg level interaction (P < .01) for dietary NE. The increase in dietary NEg with T and YG supplementation was similar (8.6 vs 8.0%) for diets containing .18 and .32% Mg. In contrast, the increase in dietary NEg with GG supplementation was 8.9% with .18% dietary Mg, but the NEg value of the diet did not increase when GG was added to diets with .32% dietary Mg. Dressing percentage was lower (1.5%, P < .1) and retail yield was greater (2.2%, P < .05) for steers fed GG- than for steers fed YG-supplemented diets. Increasing dietary Mg level increased kidney, pelvic, and heart fat (5.5%, P < .05). There was a fat x Mg level interaction (P < .1) for marbling score. With diets containing no supplemental fat, increasing dietary Mg decreased (15.2%) the marbling score, and with diets containing supplemental fat, increasing dietary Mg increased (7.2%) the marbling score. Fat supplementation decreased (P < .01) ruminal and total tract digestion of OM (10 and 3.5%, respectively) and NDF (37 and 17%, respectively). Supplemental fat did not affect (P > .10) Ca digestion but decreased (41.7%, P < .01) apparent Mg digestion. Increasing dietary Mg level increased (77.7%, P < .05) apparent Mg digestion. There were no treatment effects (P > .10) on postruminal fatty acid digestion. Fat supplementation decreased (17.3%, P < .01) the acetate:propionate molar ratio. Total ruminal protozoal counts were increased (12.7%, P < .05) by increasing dietary Mg level and decreased (12.9%, P < .05) by fat supplementation. We conclude that supplemental fats may depress Mg absorption. Increasing dietary magnesium levels beyond current recommendations may increase marbling scores in cattle fed fat-supplemented diets but may not affect growth performance or dietary NE. The NE value of fat is a predictable function of level of fat intake.

This article has been cited by other articles:

				B. W. Hess, G. E. Moss, and D. C. Rule A decade of developments in the area of fat supplementation research with beef cattle and sheep J Anim Sci, April 1, 2008; 86(14_suppl): E188 - E204. [Abstract] [Full Text] [PDF]

				S. P. Montgomery, J. S. Drouillard, T. G. Nagaraja, E. C. Titgemeyer, and J. J. Sindt Effects of supplemental fat source on nutrient digestion and ruminal fermentation in steers J Anim Sci, March 1, 2008; 86(3): 640 - 650. [Abstract] [Full Text] [PDF]

				S. Hutchison, E. B. Kegley, J. K. Apple, T. J. Wistuba, M. E. Dikeman, and D. C. Rule Effects of adding poultry fat in the finishing diet of steers on performance, carcass characteristics, sensory traits, and fatty acid profiles J Anim Sci, September 1, 2006; 84(9): 2426 - 2435. [Abstract] [Full Text] [PDF]

				T. D. Maddock, M. L. Bauer, K. B. Koch, V. L. Anderson, R. J. Maddock, G. Barcelo-Coblijn, E. J. Murphy, and G. P. Lardy Effect of processing flax in beef feedlot diets on performance, carcass characteristics, and trained sensory panel ratings J Anim Sci, June 1, 2006; 84(6): 1544 - 1551. [Abstract] [Full Text] [PDF]

				C. R. Krehbiel, J. J. Cranston, and M. P. McCurdy An upper limit for caloric density of finishing diets J Anim Sci, April 1, 2006; 84(13_suppl): E34 - E. [Abstract] [Full Text] [PDF]

				S. P. Montgomery, J. S. Drouillard, J. J. Sindt, M. A. Greenquist, B. E. Depenbusch, E. J. Good, E. R. Loe, M. J. Sulpizio, T. J. Kessen, and R. T. Ethington Effects of dried full-fat corn germ and vitamin E on growth performance and carcass characteristics of finishing cattle J Anim Sci, October 1, 2005; 83(10): 2440 - 2447. [Abstract] [Full Text] [PDF]

				D. J. Gibb, F. N. Owens, P. S. Mir, Z. Mir, M. Ivan, and T. A. McAllister Value of sunflower seed in finishing diets of feedlot cattle J Anim Sci, September 1, 2004; 82(9): 2679 - 2692. [Abstract] [Full Text] [PDF]

				E. E. D. Felton and M. S. Kerley Performance and carcass quality of steers fed different sources of dietary fat J Anim Sci, June 1, 2004; 82(6): 1794 - 1805. [Abstract] [Full Text] [PDF]

				A. Plascencia, G. D. Mendoza, C. Vasquez, and R. A. Zinn Relationship between body weight and level of fat supplementation on fatty acid digestion in feedlot cattle J Anim Sci, November 1, 2003; 81(11): 2653 - 2659. [Abstract] [Full Text] [PDF]