Effect of Increasing Protein Supplementation on Intake and Digestion of Bermudagrass Hays of Divergent Quality by Beef Cattle

• Main Author: Payne, Catherine Pomeroy
• Other Authors: Wickersham, Tryon A.
• Format: Others
• Language: en_US
• Published: 2012
• Subjects: bermudagrass; cattle; protein; supplementation
• Online Access: http://hdl.handle.net/1969.1/ETD-TAMU-2011-05-9295

Bermudagrass (Cynodon dactylon (L) Pers.), one of the predominant forages in the southeastern US, varies in nutritive value in response to management and environmental factors. Beef cattle supplementation decisions are complicated by this variability. Therefore, our objective was to determine the effect of four protein supplementation levels (0, 82, 119 and 155 mg N/kg BW) on the utilization of three bermudagrass hays (5.6, 6.3, and 8.1 percent CP).Thirteen ruminally fistulated Angus x Hereford steers (BW = 330 plus/minus 19 kg) were used in a 13 x 4 incomplete Latin square design with 13 treatments. Treatments were arranged as a 3 x 4 factorial plus a control bermudagrass hay (10.8 percent CP). Hay was provided ad libitum and protein supplements were offered as range cubes once daily. Periods were 15 d with intake determinations made on d 10 through d 13 to correspond with fecal grab samples collected from d 11 through d 14. Acid detergent insoluble ash was used as an internal marker for determination of fecal output. Hay OM intake of unsupplemented steers increased linearly (P < 0.01) as hay nutritive value increased from 75 to 77, 96 and 94 g/kg BW^0.75 for 5.6, 6.3, 8.1 and 10.8 percent CP hays, respectively. A cubic increase (P = 0.03) in OM digestibility for unsupplemented hays was observed with values ranging from 46 to 65 percent. This resulted in a linear increase (P < 0.01) in total digestible OM intake in response to hay nutritive value from 35 to 45, 51, and 60 g/kg BW^0.75 for 5.6, 6.3, 8.1, and 10.8 percent CP hays, respectively. No significant effects on total digestible OM intake were observed when hays were supplemented with protein. There was a tendency for forage OM intake of the 6.3 percent CP hay to increase linearly with supplemental protein (P = 0.08). Total OM intake increased linearly (P < 0.01) when CP was supplemented to the 6.3 percent CP hay from 77 to 88, 92, and 98 g/kg BW^0.75 for 0, 82, 119, and 155 mg N/kg BW, respectively. We conclude that forage CP content was the primary driver in determining total digestible OM intake, and the effects of protein supplementation on utilization of bermudagrass hay were varied.