Seasonal Trends of in vitro Dry Matter Digestibility of N-Fertilized Bermudagrass and of Orchardgrass-Ladino Pastures1
- H. A. Fribourg,
- K. M. Barth,
- J. B. McLaren,
- L. A. Carver,
- J. T. Connell and
- J. M. Bryan2
Improved cultivars of warm-season grasses, such as ‘Midland’ bermudagrass [Cynodon dactylon (L.) Pen.] can produce much forage during the summer. However, weight gains by growing beef animals grazing Midland pastures, even when these are well-managed, may be unsatisfactory in some months. In this study, the quality of grazable forage available to yearling beef steers, was measured at frequent intervals by in vitro dry matter digestibility (IVDMD).
Pastures of ‘Midland’ bermudagrass grown at four levels of N fertilization (0, 112, 224, 448 kg N/ha/year in three equal applications) were grazed by yearling beef steers and compared to common bermudagrass (C. dactylon var. dactylon) fertilized with 112 kg N/ha/year in three equal applications, and to a mixture of orchardgrass (Dactylis glomerata L.) and ladino clover (Trifolium repens L.).
The IVDMD of forage samples obtained at 2-week intervals from mid-April to mid-September was determined for 3 consecutive years. The data were reduced to polynomial equations describing the regression of IVDMD on elapsed days of grazing. These equations were used to generate predicted IVDMD for a 160-day grazing 5eason. Fertilization with N increased the seasonal mean IVDMD of Midland, but only the IVDMD of Midland-448 was significantly greater than that of Midland-0. Significant decreases in IVDMD from April to September were observed in each treatment (50.8 to 37.7, 54.3 to 33.7, 56.6 to 34.2, 57.1 to 34.9, 49.8 to 40.2, and 69.2 to 58.3% for Midland-0, −112, −224, −448, Common-112, and 0rc.-Lad., respectively).Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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