Abstract
The present study was conducted to compare chewing behavior and passage rates of digesta in wether fed timothy (Phleum pratense L.) hay at three different maturities (preheading, heading and seed setting). Twelve wethers (average weight 62.3kg) were randomly divided into three groups and fed 1000g hay once daily. The crude protein, neutral detergent fiber and acid detergent lignin contents on dry matter basis of hay were 9.6; 62.9; 3.3%, 6.8; 70.0; 5.5%, 4.8; 70.0: 6.9%, for preheading, heading and seed setting, respectively. Apparent digestibilities for hay decreased with advancing maturity. The daily time spent ruminating was significantly shorter for preheading hay than for heading and seed setting hay. Ruminal fluid passage rates calculated from feacal excretion curve of Co-EDTA were not different among three stages of growth. In contrast, ruminal particulate passage rate calculated from feacal dysprosium excretions of setting hay was significantly slower than that of preheading hay. Total mean retention time for seed setting hay was longer than that for preheading and heading hays. These results suggested that maturity of timothy hay affects ruminal particulate passage rate, and also indicated that ruminal passage of digesta was closely related with physical particle size reduction by mastication.
