Submitted to: Grassland International Congress Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 2/1/2001
Publication Date: 2/1/2001
Citation: Interpretive Summary: Regulation of voluntary intake continues to be one of the major topics in ruminant nutrition because of the interactions of the animal and its demand and the limitations imposed by the feed, particularly when the feed is forage. Ultimately forage intake affects all aspects of performance, growth, milk or wool. For forages in particular, rumination time (post ingestion chewing time) in the processing of forage is one of the importan limitations forages impose on their intake. We initiated this research to determine the relationships among forage chemistry (protein and digestibility estimates), eating and ruminating behavior, rate of passage, DM intake, and nutrient digestibility using goats as a model system. To assess the relative importance of all these factors, we utilized a wide array of forage types including warm-season and cool-season annual and perennial grasses and used the legume, alfalfa, as a control. We found that forage chemistry provided little insight for explaining intake in goats but was quite useful for predicting digestibility. Intake was better related to measures of resistance to breakdown (rumination time and passage rate) than simple measures of forage chemistry.
Technical Abstract: Eight species of forage, included a cool-season perennial (Festuca arundinacea) and annual grass (Triticum aestivum), four warm-season perennial grasses (Bothriochloa caucasica, B. ischaemum, Cynadon dactylon, and Tripsacum dactyloides), a warm season annual (Digitaria sanguinalis) and a perennial legume (Medicago sativa), were each cut at two or three maturities to provide a wide array of quality difference (n=20). Twenty wether goats (Capra hicus) were fed the hays in four different trials using an incomplete block so that each hay was fed to four different goats. Alfalfa produced the highest DM, but lowest neutral detergent fiber (NDF) intake. Intake was best predicted with eating time, passage rate and lag, and hay crude protein and ADF (R**2=0.57). Digestibility was best predicted with percentage acid detergent fiber (ADF), permanganate lignin and CP, and ruminating time (R**2=0.35). Weight gain (g/d) could be predicted with digestible dry matter intake with an r**2=0.42 (P<0.001). Regression lines were different (P<0.05) among forage types.