Journal of Animal Science, Vol 73, Issue 8 2474-2482, Copyright © 1995 by American Society of Animal Science

JOURNAL ARTICLE

Influence of nitrogen fertilization and defoliation frequency on nitrogen constituents and feeding value of annual ryegrass

Y. Zhang, L. D. Bunting, L. C. Kappel and J. L. Hafley
Department of Dairy Science, Louisiana State University Agricultural Center, Baton Rouge 70803, USA.

Two experiments were conducted to determine the seasonal effects of N fertilizer (NF) and defoliation interval (DI) on specific N fractions within annual ryegrass (AR) and overall usage of AR N by growing lambs. In Exp. 1, NF (0, 112, 224, and 336 kg of N/ha) and DI of 2, 4, or 6 wk were factorially applied to AR plots. Both decreasing DI and increasing NF increased N levels in AR in a manner that depended on harvest date (NF or DI x harvest date interaction, P < .05). The proportions of .2% NaOH soluble N or soluble protein N were not affected (P > .05) by NF or DI. Although NF had no effect (P > .05) on in situ disappearance of DM, decreasing the DI seemed to reduce the severity of the season-induced reduction in DM disappearance (DI x harvest date interaction, P = .04). In Exp. 2, NF (0 or 224 kg of N/ha) and a DI of 2 or 6 wk were factorially applied to AR plots. Fresh, frozen AR was fed in semipurified diets (48% of DM as AR) to four wether lambs (23 +/- 1.3 kg) using a 4 x 4 Latin square. Diets including AR had greater ruminal DM and plant N digestibilities when AR had a 2-wk vs a 6-wk DI with NF but had reduced digestibilities when AR had a 2-wk vs a 6-wk DI without NF.(ABSTRACT TRUNCATED AT 250 WORDS)

This article has been cited by other articles:

				R. L. Kallenbach, G. J. Bishop-Hurley, M. D. Massie, M. S. Kerley, and C. A. Roberts Stockpiled Annual Ryegrass for Winter Forage in the Lower Midwestern USA Crop Sci., July 1, 2003; 43(4): 1414 - 1419. [Abstract] [Full Text] [PDF]