Effects of Varying Particle Size of Forage on Digestion and Chewing Behavior of Dairy Heifers

Abstract

Eighteen Holstein heifers were fed long and chopped coarse and fine alfalfa hay ad libitum to evaluate effects of physical form on digestion and chemical composition of feed and fecal particles and to examine the applicability of a sinusoidal model to chewing behavior. Recordings of jaw movement were divided into 1-h segments for analysis. Least square mean size of fecal particles from coarse and finely chopped diets were 290 and 297 micrometers as compared to 227 micrometers on long hay. Intakes of dry matter were greater an digestibilities lower for chopped as compared to long hay. Crude protein content of separated feed and fecal particles increased as particle size decreased. Neural and acid detergent fiber concentrations decreased in feed and feces with decreasing particle size. Lignin content of feed particles decreased as particle size decreased, whereas for fecal particles lignin as a percent of cell wall followed a "U" shaped pattern of declining then increasing as size decreased. Patterns were sinusoidal for eating and ruminating long and chopped hays and total chewing (eating and ruminating) of long hay. Our results suggest a gradual effect on chemical degradation and physical detrition of digesta particles and chewing behavior as forage particle size decreased.

Effects of physical form and stage of maturity at harvest of whole-crop barley silage on intake, chewing activity, diet selection and faecal particle size of dairy steers

“…However, daily rumination time was probably not limited by daily eating time in the present study, as it did not differ between the long and chopped silage treatments whereas daily eating and chewing times did. The daily rumination time was within the normal range of 8 to 9 h per day given by Welch (1982) and comparable with results from other studies with growing cattle (Deswysen and Vanbelle, 1978;Jaster and Murphy, 1983;Teller et al, 1993).…”

“…The higher eating rate but shorter eating time of chopped WCBS compared with long can be explained by the lower need for chewing per kg DM and NDF during ingestion of the chopped silage. Similarly, Jaster and Murphy (1983) found shorter daily eating time for chopped lucerne hay compared with long and Deswysen and Vanbelle (1978) found shorter eating time for chopped grass silage compared with long when fed to dairy heifers. Main effects of maturity (M) and physical form (F): *P , 0.05; **P , 0.01; ***P , 0.001; T 5 tendency (0.05 , P , 0.1).…”

“…This might indicate that long particles in the unchopped WCBS were more efficiently reduced in size during rumination than long particles in the chopped silage, as suggested by Jaster and Murphy (1983). Chopping increased the proportion of faecal particles retained on the 1 mm pore size and the mean faecal particle size in agreement with findings by Jaster and Murphy (1983) and Main effects of maturity (M) and physical form (F): *P , 0.05; **P , 0.01; ***P , 0.001; T 5 tendency (0.05 , P , 0.1). There were no interactions between M and F in any of the variables.…”

“…might be related to a more efficient particle size reduction during rumination of long silage, as daily rumination time was similar across treatments (Jaster and Murphy, 1983). Larger mean faecal particle size with later maturity of the WCBS is in agreement with findings by Jalali et al (2008) for faeces from ewes fed grass silage at different stages of maturity.…”

“…An increased need for chewing during ingestion might decrease eating rate and restrict the time available for rumination (Teller et al, 1993) and as the digestive function of rumination is to reduce the particle size and facilitate particle outflow from the reticulo-rumen, restricted rumination can decrease feed intake (Welch, 1982). Faecal particle size reflects the size of particles leaving the rumen (Kennedy, 2005) and is affected by forage particle size (Jaster and Murphy, 1983) and stage of maturity (Jalali et al, 2008).…”