Digestibility of prairie hay diets supplemented with different levels of magnesium-mica by beef heifers

• Published in: Journal of animal science Vol. 78; no. 3; pp. 718 - 725
• Main Authors: Coffey, K. P, Nagaraja, T. G, Towne, E. G, Brazle, F. K, Moyer, J. L
• Format: Journal Article
• Language: English
• Published: Savoy, IL Am Soc Animal Sci 01-03-2000; American Society of Animal Science; Oxford University Press
• Subjects: Aluminum Silicates - metabolism; Animal Feed; Animal productions; Animals; Biological and medical sciences; Cattle; Cattle - metabolism; Diet; Dietary Fiber - metabolism; Dietary Proteins - metabolism; Dietary Supplements; Digestion; Digestive system; Excretory system; Female; Fermentation; Fundamental and applied biological sciences. Psychology; Glycine max; Magnesium - metabolism; Poaceae - metabolism; Terrestrial animal productions; Vertebrates; Hay; Farming animal; Ruminant animal; Animal feeding; Ox; Rumen; Food additive; Experimental study; Dose activity relation; Vertebrata; Mammalia; Beef cattle; Rearing; Heifer; Artiodactyla; Magnesium compound; Ungulata; Mica; Digestibility
• ISSN: 0021-8812; 1525-3163; 0021-8812
• DOI: 10.2527/2000.783718x

Four ruminally fistulated, nonpregnant, nonlactating heifers (515 +/- 7.9 kg) were offered chopped (10-cm screen size) prairie hay for ad libitum consumption with 1.8 kg/d of supplements to provide 0, 45, 113, or 181 g/d of magnesium-mica (MM) in a 4 x 4 Latin square design experiment. Heifers were adapted to diets for 7 d in drylot followed by a 19-d confinement period in individual stalls within a metabolism facility. Total feces and urine were collected for 5 d, daily intake and water consumption were monitored for 16 d, and in situ disappearance of fiber (prairie hay) and CP (soybean meal) were determined during the confinement period. Ruminal samples for fermentation product analyses were collected at feeding and every 2 h thereafter for 12 h on d 18, and rumens were evacuated at 1100 on d 19 to determine rumen fill. Cubic responses (P < .05) to MM level were observed for DM, OM, NDF, and ADF digestion and were characterized by a tendency for improved digestion with 45 g/d compared with the control diet, followed by a suppressive effect on digestion with 113 g/d, then little effect with 181 g/d MM. In situ NDF disappearance at 72 and 96 h tended (P < . 10) to be influenced quadratically by level of MM, but MM level had no apparent effect on ruminal fill and passage rate, ciliated protozoa counts, in situ rate of disappearance of fiber or CP, or nitrogen balance. Therefore, feeding MM at low levels to heifers consuming a prairie hay diet with a 20% CP supplement seemed to be beneficial for feed digestion with no measurable negative impact on intake or ruminal protein or fiber digestion.