Rumen Health Technical Guide

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Poor Fiber Degradation

Fibrolytic microbial populations are vital to maximizing forage digestion.

Ruminants depend on microbial fermentation within the rumen to acquire energy from plant material.15ReferenceView allOba M. and Allen M. S. 1999.
Evaluation of the Importance of the Digestibility of Neutral Detergent Fiber from Forage: Effcts on Dry Matter Intake and Milk Yield of Dairy Cows. J. Dairy Sci. 82: 589-596.

The different fractions from plant cells walls are not entirely physically accessible and achieve various degrees of digestibility in the rumen.

To improve animal productivity, a portion of the forage diet is increasingly substituted with readily-fermentable carbohydrates. However, the supplementation of diets with readily-fermentable carbohydrates is known to depress rumen fiber degradation.16ReferenceView allMoorby J. M., Dewhurst R. J., Evans R. T., and Danelon J. L. 2006.
Effects of Dairy Cow Diet Forage Proportion on Duodenal Nutrient Supply and Urinary Purine Derivative Excretion. J. Dairy Sci. 89 : 3552-3562.

Additionally, the major fiber-degrading bacterial species Fibrobacter succinogenes, Ruminococcus albus and R. flavefaciens, as well as rumen fibrolytic fungi, are particularly vulnerable to rumen pH at 5.8 or lower.

The challenge for ruminant nutritionists is to maximize a balanced nutrient intake and availability, digestion and ultimately the efficiency of this process to convert to milk, meat or wool.

PHOTO Rumen fungi on plant cell wall INRA
Rumen fungi attached to a plant cell wall ©INRA

Digestion of fiber in the rumen can depend on carbohydrate type

Fiber degradation depends on rumen pH

Indicators and risk parametersGeneral reasons
table-arrow-upANIMAL PERFORMANCE- Reduced average daily gain and increased feed conversion ratio may be due to impaired rumen fermentation in beef cattle.
- Low milk production, milk fat and a reduced fat/protein ratio may be due to impaired rumen fermentation in lactating dairy cattle.17ReferenceView allBritt J. S., Thomas R. C., Speer N. C., and Hall M. B. 2003.
Efficiency of Converting Nutrient Dry Matter to Milk in Holstein Herds. J. Dairy Sci. 86:3796–3801.
18ReferenceView allAllen M. S. 1997.
Relationship Between Fermentation Acid Production in the Rumen and the Requirement for Physically Effective Fiber. J. Dairy Sci. 80: 1447-1462
19ReferenceView allSauvant D. and Peyraud J. L. 2010.
FRENCH Calculs de ration et évaluation du risque d’acidose. INRA Prod. Anim. 23: 333-342.
Undigested processed grains in the feces because of poor rumen efficiency may be due to an increased passage rate due to an imbalanced or low diet digestibility.20ReferenceView allHall M. B. 2002.
Characteristics of manure: what do they mean? Proceedings of the Tri-State Nutrition Conference. Pages 141-147. April 16-17, 2002
table-arrow-upBODY CONDITIONThin animals can indicate poor rumen efficiency due to poor diet digestibility and decreased intake.22ReferenceView allZaaijer D. and Noordhuizen J. P. T. M. 2003.
A novel scoring system for monitoring the relationship between nutritional effiency and fertility in dairy cows. Irish Vet. Journal 56 : 145-151.
23ReferenceView allHeinrichs A.J.
Penn. State extension website : Body Condition Scoring as a Tool for Dairy Herd Management.
24ReferenceView allButler W.R. and Smith R. D. 1989.
Interrelationships Between Energy Balance and Postpartum Reproductive Function in Dairy Cattle. J Dairy Sci 72: 767-783
table-arrow-downHEAT STRESS
Heat stress (temperature and / or humidity) increases the risks of acidosis and low fiber degradation because:
> Eating behavior is negatively affected: cattle prefer to eat during cooler times of the morning and later evening.
> Dry matter intake is decreased: cattle sort the diet with a lower proportion of forage and higher levels of fermentable carbohydrates.
> High loss of saliva (from drooling and open-mouthed breathing) in hot weather decreases the amount of natural buffers to the rumen.31ReferenceView allBurgos Zimbelman Rosemarie and Collier Robert J. 2011.
Feeding Strategies for High-Producing Dairy Cows During Periods of Elevated Heat and Humidity. Tri-State Dairy Nutrition Conference pages 111-126.