Evaluating Strategies to Reduce Ruminal Protozoa and Their Impacts on Nutrient Utilization and Animal Performance in Ruminants – A Meta-Analysis

Abstract

Several studies have evaluated the effects of complete or partial ruminal protozoa (RP) inhibition; however, to this date, no practical suppressant has been identified and used in large scale. This meta-analysis quantitatively evaluates the effectiveness of multiple strategies on inhibiting RP numbers and their influence on ruminal fermentation and animal performance. This study compared 66 peer-reviewed articles (16 manuscripts for complete and 50 manuscripts for partial RP inhibition that used supplemental phytochemicals and lipids, published from 2000 to 2018, to inhibit RP in vivo. Data were structured to allow a meta-analytical evaluation of differences in response to different treatments (complete RP inhibition, phytochemicals, and lipids). Data were analyzed using mixed models with the random effect of experiment and weighted by the inverse of pooled standard error of the mean (SEM) squared. Supplemental phytochemicals and LCFA had no effects on inhibiting RP numbers; however, supplemental MCFA had a potent antiprotozoal effect. Both complete and partial RP (supplemental phytochemicals and lipids) inhibition decreased methane production, total tract digestibility of OM and NDF, and ruminal NH3-N concentration and increased propionate molar proportion. Methane production, molar proportions of acetate and propionate, total tract NDF digestibility were affected by the interaction of treatment (supplemental phytochemicals and lipids) and RP numbers. Supplemental phytochemicals and lipids can be effective in reducing methane production when RP numbers is below 7 Log10 cells/mL, especially by supplemental saponins, tannins, and MCFA. In terms of animal performance, supplemental tannins could be recommended to control methane emissions without affecting animal performance. However, their negative effects on total tract digestibility could be a drawback when feeding tannins to ruminants. The negative effects of supplemental lipids on milk fat composition should be considered when feeding lipids to ruminants. In conclusion, ruminal protozoa play important roles on methanogenesis, fiber digestion, and ruminal NH3-N concentration, regardless of experimental diets and conditions; supplemental phytochemicals and lipids can be effective on reducing methane production when RP numbers is below 7 Log10 cells/mL. Among these partial RP inhibition strategies, supplemental tannins could be recommended to control methane production.

Effect of Lerak (Sapindus Rarak) Extract in High Roughage Diet on Rumen Microbial Protein Synthesis and Performance of Sheep

“…Previously, (Ramos-Morales et al 2017) suggested that a persistent effect to depress protozoa can be done by chemical modification of the group that attached to the sapogenin. The type of diet fed to the animal, besides the saponin structure may also affect the antiprotozoal activity of these saponins (Patra and Saxena 2009;Dai and Faciola 2019). In this experiment, types of protozoa that survived in the presence of SRE were not identified, but (Zhou et al 2011) showed that tea saponin could selectively inhibit specific type of protozoa causing reduction of protozoal diversity in the rumen of sheep.…”

Effects of Increasing Levels of Palm Kernel Oil in the Feed of Finishing Lambs

“…The total digestible nutrients were calculated according to NRC [24] using the digestible fractions of nonfiber carbohydrates, crude protein, ether extract, and neutral detergent fiber. The nutrient digestibility coefficient (CD) was determined according to the equation: CD = ((kg of ingested portion − kg of excreted portion)/(kg of ingested portion)) × 100 (1) The nitrogen balance and microbial protein production were evaluated by total urine collection. Total urine collection was carried out in individual bowls containing 50 mL of 20% sulfuric acid solution.…”

“…1 Assurance levels (per kilogram of active elements): 120 g of calcium, 87 g of phosphorus, 147 g of sodium, 18 g of sulfur, 590 mg of copper, 40 mg of cobalt, 20 mg of chromium, 1800 mg of iron, 80 mg of iodine; 1300 mg of manganese, 15 mg of selenium; 3800 mg of zinc, 300 mg of molybdenum; maximum 870 mg of fluoride. 2 NFC = 100 − NDF ap − CP − EE.…”

In Vitro Screening of Plant Materials to Reduce Ruminal Protozoal Population and Mitigate Ammonia and Methane Emissions

“…Newbold et al [40] recommended complete rumen protozoal elimination as a means to increase microbial protein supply by 30% while reducing methane production by up to 11%. However, Dai and Faciola [41] recommended partial rumen protozoal reduction strategies, and tannin supplementation, to reduce methane production. Plant material supplementation resulted in reduced TVFA concentrations, supporting the findings of Min et al [36] concerning lower TVFA concentrations as compared to the control.…”