Influence of Harvesting Age and Season on Digestibility and Chemical Composition of Pelleted Coastal Bermudagrass

Coastal Bernmdagrass was harvested at either 3-, 5-, or 7-wk frequencies throughout the season, dehydrated and pelleted.It was fertilized with 400 lb of N per acre in split applications.In the total fertilizer applied, the ratio of N, P~O~, and K.~O was 4:1:2.Total collection digestion trials were conducted with Holstein bull calves.Digestibility of all components decreased as the age of the grass at harvest increased.In excess of 95% of the variation associated with forage age was attributed to the linear effect for dry matter, energy, organic matter, crude fiber, crude protein, ash, and NFE.Average digestibilities for forages harvested at 3-, 5-, and 7-wk frequencies were organic matter, 66.0, 60.7, and 56.8; dry nmtter, 65.9, 60.7, and 56.6; protein, 67.0, 58.8, and 51.7; crude fiber, 66.2, 59.1, and 54.2; and NFE, 65.3, 61.7, and 59.2.Correspondingly, calculated estimated net energy values were: 59.2, 51.2, and 45.0 therms per 100 lb.As forage age at harvest increased, the protein content declined substantially, but there was only a moderate increase in crude fiber.There was a tendency for crude fiber levels to be highest in mid-season.On a within-harvesting frequency basis, nylon bag dry matter disappearance determined in fistulated steers tended to be lowest in the middle of the season.The 3-, 5-, and 7-wk forages contained the following percentages on a dry basis: protein, 15.3, 11.8, and 10.8, and crude fiber, 28.0, 30.2, and 30.9.