Particle size reduction during initial mastication of forages by dairy cattle.

Abstract

Four experiments were conducted with dairy cattle to determine the effects of initial feed particle size and moisture content on particle size of ingested masticates. Three mature Holstein cows were used in either latin square or Youden square designs. Samples of masticated and ingested boli were collected at the cardiac opening through a ruminal fistula between 0 and 5, 5 and 10 and 10 and 15 min after meal initiation. In Exp. 1, masticate log mean particle sizes (LMPS) (ln microns, log normal distribution) were 3.50, 3.53 and 3.50 for corn silage, fine-chopped alfalfa haylage and coarse-chopped alfalfa haylage, respectively. In Exp. 2, boli LMPS for ground, chopped and long alfalfa hay were 3.11, 3.76 and 4.09, respectively. Boli LMPS in Exp. 3 for ground, chopped and long timothy hay were 2.93, 3.12 and 3.03, respectively. Exp. 4 compared the effect of addition of water to produce 30%, 47%, 64% and 82% DM in chopped alfalfa hay. Boli LMPS were 3.66, 3.56, 3.64 and 3.68 for the respective alfalfa hay DM contents. Feed LMPS was not reduced during mastication in Exp. 4, nor were there differences in LMPS due to time after feeding. Boli LMPS was affected by feed particle size of alfalfa hay, but there was no effect of feed particle size on masticate particle size in timothy hay. The magnitude of particle size reduction during mastication appears to be dependent on forage type and is not dependent totally on initial feed particle size and DM content of forages.

Effect of maturity stage and chopping length of maize silage on particle size reduction in dairy cows

“…The proportion of large particles larger than 2 mm (LP2) was determined by the sum of the particle proportions retained on 8, 4, and 2 mm aperture sieves, this being considered as the critical size for leaving the reticulo-rumen in cattle [23,28]. As performed by Bailey et al [4], the differences in particle size from feed to bolus and from bolus to rumen were expressed using differences in mean particle size and LP2 proportions.…”

“…With hays and straws, Lee and Pearce [19] also reported differences in the extent to which roughages were reduced by ingestive mastication. More recently, Bailey et al [4], Bernard et al [6], studied comminution during ingestive mastication with hays with different initial particle sizes. A reduction in particle size was greater with the long than with the short form, 22 vs. 15% [4], 50 vs. 32% [6].…”

“…More recently, Bailey et al [4], Bernard et al [6], studied comminution during ingestive mastication with hays with different initial particle sizes. A reduction in particle size was greater with the long than with the short form, 22 vs. 15% [4], 50 vs. 32% [6]. To our knowledge, only one trial on particle size reduction during mastication has been conducted with silages, haylage and maize silage [4]; initial particle size distribution of the silages was similar and so the authors could not draw any firm conclusion from their trial.…”

“…Most feed particle comminution to sizes small enough to leave the rumen is accomplished by chewing, and interrelationships exist between chewing activity, particle comminution, ruminal retention time and voluntary intake [9]. Only a few authors have studied particle comminution mechanisms with cattle in relation to control of feed intake and most results have been obtained with hay or haylage [4,20,26]. In this experiment, particle size reduction in maize silages differing in maturity stage and chopping length was studied in cows fed restricted amounts.…”

Intake and digestive kinetics of leaf and stem fractions

“…Bailey et al (1990) reported that particle size of ruminal contents had a direct effect on the rate at which diets are passed from the rumen. They suggested that ruminal particle size was a function of the initial particle size of masticated feed and the rate of particle size reduction due to rumination and microbial breakdown.…”