Release of cell contents and comminution of particles of perennial ryegrass herbage during ingestion by dairy cows fed indoors or grazing

Abstract

The effect of feeding indoors fresh perennial ryegrass vs. grazing on ingestive behaviour, release of cell contents and comminution of particles during ingestion, as well as on gas production of ingested boli fermented in vitro, was studied. Indoor feeding and grazing were compared using four dairy cows according to a triple reversal design with six periods. Chemical and morphological composition of the ingested herbage was similar for both indoor feeding and grazing treatments. The intake rate was markedly higher indoors compared with grazing [52AE1 vs. 22AE9 g dry matter (DM) min )1 ] with heavier boli and less saliva added per gram of DM intake. The proportions of intracellular nitrogen and chlorophyll released during mastication after ingestion of herbage fed indoors were lower, and the median size of the particles in the boli was larger (5AE97 vs. 4AE44 mm) compared with grazing. As a result, the rate of gas production in vitro was also lower for herbage fed indoors compared with grazing (0AE423 vs. 0AE469 mL min )1 g )1 incubated DM). Indoor feeding or grazing may have limited consequences in vivo on the kinetics of availability of nutrients for micro-organisms in the rumen, because the consequences of the more extensive physical damage suffered by herbage ingested at grazing could be compensated by a lower intake rate.

Effect of rumen fill on intake of fresh perennial ryegrass in young and mature dairy cows grazing or zero-grazing fresh perennial ryegrass

“…Consequently, it is likely that the better distribution and succession of eating and ruminating activities during day and night observed indoors could have created a larger outflow of particles from the rumen on a daily basis, and an outflow more steadily distributed throughout the day. This could be particularly true given that the feeding method apparently had no impact on the swallowed particle size after ingestive mastication in the present experiment, contrary to the observations of Boudon et al (2006) on a short sward. The differences in the distribution of eating or ruminating activities during day and night were responsible for most of the variation observed between the two ways of feeding on the ruminal content weights and particle sizes in the morning.…”

“…Ash, fiber (NDF, ADF and ADL), CP, NSC contents along with IVOMD were analyzed using the methods cited by Boudon et al (2006) and Delagarde et al (2000). Yb content was determined according to Siddons et al (1985).…”

“…Particle size distribution of rumen contents and ingestive boli was analyzed by wet sieving as described by Boudon et al (2006), using a vertical oscillating sieve shaker (Analysette 3, Fritsch). Sieve pore sizes were 4, 2, 1, 0.5, 0.25, 0.125 and 0.0625 mm for rumen contents and 16, 8, 4, 2, 1 and 0.0625 mm for ingestive boli.…”

“…The two or three first boli were discarded and the 15 following were collected, individually weighed and then gathered. A portion of the samples of rumen contents and boli was used for DM determination (808C forced-air oven for 72 h); the remainder was frozen (2208C) for chemical analyses and determination of particle size distribution.Particle size distribution of rumen contents and ingestive boli was analyzed by wet sieving as described by Boudon et al (2006), using a vertical oscillating sieve shaker (Analysette 3, Fritsch). Sieve pore sizes were 4, 2, 1, 0.5, 0.25, 0.125 and 0.0625 mm for rumen contents and 16, 8, 4, 2, 1 and 0.0625 mm for ingestive boli.…”

Foraging behavior and ruminal fermentation of dairy cows grazing ryegrass pasture alone or with white clover

“…Additionally, absorption rates of VFA across the rumen wall may have been increased at night due to a lower rumen fluid volume, resulting in a higher effective surface area for absorption (Dijkstra et al, 1993). Small increases in the VFA pool immediately after the beginning of grazing are expected due to a low efficiency of chewing during eating (Boudon et al, 2006;Acosta et al, 2007). Ingestive chewing is one of the main reasons to release soluble nutrients from feeds (Chilibroste et al, 2007).…”