Ruminal degradability of alfalfa and corn after processing or maceration

Abstract

. 1999. Ruminal degradability of alfalfa and corn after processing or maceration. Can. J. Anim. Sci. 79: 361-368. The effects of mechanical treatment on ruminal degradability of alfalfa and corn were determined in three experiments using nylon bags incubated in the rumen of two fistulated dry cows. The first experiment was a 2 × 2 × 2 factorial design applied to chopped alfalfa at two levels of mechanical treatment (processing with two corrugated rolls in a forage harvester or no processing), two throughput rates (medium or high) and two moisture contents (after a 4-h or a 24-h field wilting period prior to processing). The second experiment was a 2 × 2 factorial design applied to chopped corn at two levels of mechanical treatment (processed or not) and two throughput rates (medium or high). In these two experiments, forages were immediately frozen (not fermented) for later degradability measurements. In the third experiment, alfalfa was mowed either with a conventional mower-windrower or an experimental mower-macerator with three corrugated rolls. After 40 h of field wilting, alfalfa was dehydrated and processed into pellets. In the first experiment (chopped and frozen alfalfa), throughput, processing and wilting period had no effect (P > 0.05) on the effective degradability of DM, CP, NDF and ADF. In the second experiment, DM degradability of chopped corn decreased with an increased throughput (46.4% vs. 43.7%) but increased with processing (43.9% vs. 46.2%). Processing also increased CP degradability of corn. In the third experiment, maceration with subsequent field wilting during 40 h and dehydration produced alfalfa pellets with a higher degradability of DM (56.0% vs. 50.4%) and of NDF (27.1% vs. 17.3%) than pellets from non-macerated alfalfa. These results suggest that the increase in ruminal degradability is greater with alfalfa macerated and wilted in the field (exp. 3) than with alfalfa frozen immediately after harvesting and processing (exp. 1). Maceration probably reduced the loss of nutrients by decreasing field respiration. Processing of corn may have increased the ruminal degradability because of increased kernel breakage that facilitated starch digestion.Key words: Maceration, crop processing, ruminal degradability, alfalfa, corn Savoie, P., Tremblay, G. F. et Petit, H. V. 1999. Dégradabilité ruminale de la luzerne et du maïs après le broyage ou le surconditionnement. Can. J. Anim. Sci. 79: 361-368. Les effets de traitements mécaniques sur la dégradabilité ruminale de la luzerne et du maïs ont été déterminés lors de trois expériences en utilisant des sachets de nylon incubés dans le rumen de deux vaches taries fistulées. Le premier essai était un dispositif factoriel 2 × 2 × 2 appliqué à la luzerne hachée avec deux niveaux de traitement mécanique (un module de broyage à deux rouleaux rainurés intégrés dans un fourragère ou aucun broyage), deux débits (moyen ou élevé) et deux teneurs en eau (après 4 h ou 24 h de fanage au champ avant le traitement mécanique). La deuxième expérience était un disposi...

Ruminal protein and fibre degradability of lucerne hay as affected by regrowth period and dairy breed

“…A potential DM degradability value of approximately 48% was reported by Savoie et al (1999) for chopped LH, which corresponds with the 4 weeks' regrowth value obtained in the current study. The same authors reported a CP degradability value of 57.8%, which is somewhat higher than the values in the current study.…”

“…In Figure 1, the low rate of NDF degradation of LH harvested after the 6-week regrowth period is evident. A faster rate of protein degradation (c = 0.32) was reported by Savoie et al (1999) which could probably be explained by the fact that the LH was crushed during harvesting in their experiment.…”

“…The rumen pH in the current study was generally low and varied between 5.6 to 5.8 for Holsteins and 5.6 to 5.7 for Jerseys from one hour before feeding to five hours after feeding. This could have resulted in the lower b-values compared to those reported by Savoie et al (1999). It should also be kept in mind that, although the cows were non-lactating, they received a diet typical for lactating cows to simulate rumen conditions.…”

“…While the decrease in the soluble CP fraction is probably related to the increase in the NDF-content of the hay, the increase in the apparent soluble NDF fraction may be an artifact of model fitting or possibly a sample aberration or it may be related to material washout losses from the Dacron bags. Savoie et al (1999) determined zero-time disappearance values by washing the bags in cold water until the rinsing water was clear. These authors found a soluble DM fraction (30.7%) for chopped lucerne similar to the 6 weeks' regrowth value observed for LH in the current study.…”

“…Savoie et al (1999) reported a b-value of 51.8% for LH (420 g/kg NDF) that was wilted for four hours. The rumen pH in the current study was generally low and varied between 5.6 to 5.8 for Holsteins and 5.6 to 5.7 for Jerseys from one hour before feeding to five hours after feeding.…”