Seasonal variation of nutrient intake and digestibility of forage in beef cows grazed on a dwarf bamboo (Pleioblastus argenteostriatus f. glaber) dominant pasture

Abstract

AbstractDwarf bamboo is a significant but unique native forage for cattle grazing in Japan. A pasture dominated by Pleioblastus argenteostriatus f. glaber, a type of dwarf bamboo, was used to evaluate nutrient intake, digestibility of forage and nutritional status of grazing cows. Eight Japanese Black cows were grazed on the pasture, and six among the eight grazing cows were used for the experiment. This experiment consisted of three periods: spring (May), summer (July) and autumn (September–October) in 2002 and 2003. The nutrient intake and digestibility of the cows were estimated by the double indicator method with chromic oxide (Cr2O3) as the external indicator and acid detergent insoluble ash (ADIA) in forages as the internal indicator. The crude protein (CP) and neutral detergent fiber (NDF) contents of forage selected by the cows hardly changed during the grazing seasons in both years. Crude ash, acid detergent lignin (ADL), ADIA, and acid detergent insoluble protein (ADIP) contents were the highest in autumn in both years. Nutrient intake of the cows was lower in autumn than in other seasons. Nutrient digestibility of the cows increased slightly from spring to summer and then decreased in autumn. Metabolizable energy (ME) intake satisfied the maintenance requirements of the cows in spring and summer; however, it was only 50%–70% of the maintenance in autumn for both years. Urea nitrogen concentration in plasma was always high, approximately 20 mg dL−1, during grazing periods. Inorganic phosphate (IP) concentration in plasma was lower than critical value (4.5 mg dL−1) in spring and autumn. Therefore, energy and phosphate supplementation are needed for the cows grazed on P. argenteostriatus f. glaber‐dominated pasture.