Seasonal Forage Nutritive Value Variation of Coastal and Coastcross-1 Bermudagrass

Chronological age is a common basis of reference used in bermudagrass research treatments and forage production management recommendations. Plant growth and development changes due to the environment could cause a confounding of research results when assuming that forage of a given chronological age has a similar nutritive value regardless of the season or year. This field study on victoria clay soil (a Typic Pellusterts) was conducted to measure the mouth-to-mouth variation in quality of Coastal and Coastcross-1 varieties of bermudagrass (Cynodon dactylon, (L.) Pers.) harvested at 4, 8, 12, 16, 20, and 24 week growth intervals through the 1975 growing season, Samples were taken from March through December. Acid detergent fiber (ADF), neutral detergent fiber (NDF), crude protein (CP), and in vitro dry matter digestibilit (IVDMD) were measured. Statistical comparisons or quality were made only within age intervals. Fifty percent of 312 month-to-month comparisons were significantly different. Coastcross-1 bermudagrass was more variable than Coastal bermudagrass, because of greater declines as well as greater increases in quality due to environmental changes. The 8-week-old forage had the greatest variation in quality in both varieties. The most measurable variability was in crude protein content. Month-to-month variability of CP declined with advancing maturity in Coastal and increased in Coastcross-1. Variation as measured by ADF and IVDMD was second and third to CP, respectively, and the grassa responded similarly. Overall variability measured by NDF was the lowest of the four methods used. Actual percentage changes in ADF, NDF, CP, and IVDMD of 8-week-old forage within a 30day period was as high as 9.9, 3.0, 4.6, and 12.7 percentage units, respectively, for Coastcross-1. The impact of environmental conditions on forage quality was significant and was dependent up on the age of the grass, the specific quality component in question, and the grass variety. Therefore, care should be exercised in extrapolating research data from one season of the year to another even at the same geographical location.