Table 1.

Effects of chitosan on rumen fermentation and methane emission.

Chitosan	Length of Experiment	Dosage	Substrate/Feed	Methane Determination	Results	Reference
>85% deacetylated with a viscosity equal to 140 mPas in 1% acetic acid solution at 25 °C	In vitro (18 days)	0 and 50 g/L of culture fluid	Forage-to-concentrate ratio 50:50	Gas chromatography	42% of reduction methane versus control, without modification of the rumen microbiota and VFA	[39]
Six different types	In vitro (24 and 144 h)	750 mg/L of culture fluid	Maize silage	Stoichiometry	Modification of rumen microbial fermentation and reduced 10 to 30% of methane	[53]
Three different types	In vitro (24 h)	0, 325, 750, and 1500 mg/L of culture fluid	Alfalfa hay and concentrate ratio 80:20; 50:50; 20:80	Stoichiometry	Effects were related to the nature of the feed and the characteristics of the additive, inconsistent results in methane reduction	[54]
Chitin and chitosan from Black Soldier Fly	In vitro (24 h)	10 and 20 g/L of culture fluid	Grass Setaria splendida: concentrate ratio 60:40	Gas chromatography	Methane production was not reduced and digestibility of OM and DM were decreased	[56]
Deacetylated chitin, poly (D-glucosamine) Sigma-Aldrich Co., St. Louis, MO, USA	In vitro (24 h)	100 mg/L of culture fluid	Meadow hay, barley grain, maize silage	Gas chromatography	Chitosan had an effect on IVDMD, total gas, slight effect on methane production, and some rumen ciliate genera	[57]
Deacetylation degree >95%; viscosity < 500 mPa s	In vitro (11 days)	750 mg/d of culture fluid	Grass hay and a concentrate mixture 10:90 using sunflower or rapeseed meal	Not quantified	Chitosan inhibited biohydrogenation	[55]
Deacetylation degree > 95%, viscosity < 500 mPa s	In vivo, in vitro Sheep (45 days)	0 and 136 mg/kg of BW	Alfalfa hay and concentrate at 50:50	Stoichiometry	Chitosan reduce NDF apparent digestibility, ruminal NH3-N concentration and modulates ruminal and fecal fermentative activity	[59]
Degree of deacetylation > 92% apparent density 0.64 g/mL; total ash ≤ 2.0%; pH 7.0–9.0; viscosity < 200 cPs	In vivo Cattle (84 days)	0, 50, 100 and 150 mg/kg BW	Corn Silage-concentrate 60:40	Not quantified	Chitosan shifted rumen fermentation, improved nutrient digestibility and propionate concentrations	[38]
Deacetylation degree of 86.6%	In vivo Cattle (84 days)	0 and 4 g/kg of DM	Corn silage-to- concentrate ratio 50:50	Not quantified	Improved feed efficiency, increased milk UFA concentration	[27]
Deacetylation degree ≥ 85%, 0.32 g/mL density, pH 7.90, and viscosity < 200 cPs	In vivo Cattle (105 days)	0, 400, 800, 1200 or 1600 mg/kg DM	Grazing Urochloa brizantha and concentrate at 150 g/100 kg of LW	Not quantified	Chitosan increased DMI and digestibility, propionate concentration and microbial crude protein	[28]
Deacetylation degree of 86.3%; 0.33 g/mL of apparent density, pH = 7.9, viscosity < 200 cPs, 1.4% ash, and 88.3% of DM	In vivo Cattle (98 days)	0, 75, 150, 225 mg/kg BW	Corn silage to concentrate ratio 63:37	Not quantified	In dairy cattle works like a modulator of rumen fermentation, increasing milk yield, propionate and nitrogen utilization	[29]
Deacetylation degree of 95%; apparent density of 0.64 g mL−1, 20 g kg−1 of ash, 7.0–9.0 of pH, viscosity < 200 cPs.	In vivo Cattle (25 days each period)	0, 2.0 g/kg Chitosan (CH) of DM. Whole raw soybean (WRS) 163.0 g/kg DM; and CH + WRS	Corn silage to concentrate ratio 50:50	Not quantified	Chitosan improved nutrient digestion and decrease DMI and reduce nitrogen excreted in feces	[37]
Deacetylation degree 90%	In vivo (21 days each period) and in vitro (24 h)	0.0, 0.5, and 1.0% of DM	High-concentrate (85%) Low concentrate (36%)	Sulfur hexafluoride (SF6)	In vivo: No effect on enteric methane emissions. In vitro: Low concentrate substrate increased methane production	[41]
Deacetylation degree of 86.6%; 0.33 g/mL of apparent density, pH of 8.81	In vivo Cattle (84 days)	50, 100 and 150 mg/kg BW	Corn silage to concentrate ratio 50:50	Not quantified	Improved nutrient digestibility without altering productive performance of dairy cows	[58]
Deacetylation degree 95%; viscosity < 200 cPs density 0.64 g/mL; pH 7.0–9.0	In vivo Cattle (84 days)	150 mg/kg BW	Maize silage: concentrate ratio 50:50	Not quantified	Chitosan increase the digestibility and reduce acetate to propionate relation	[60]
Deacetylation degree of 86.3%; apparent density of 0.32 g/mL, pH 7.9, viscosity of 50 cP at 20 °C	In vivo Cattle (92 days)	0 or 4 g/kg Chitosan (CH) or Whole Raw Soybean (WRS) of DM	Corn silage: concentrate ratio 50:50	Not quantified	CH + WRS affected ruminal fermentation, increased milk content of UFA, decreases nutrient intake, digestibility, microbial protein synthesis, and milk yield. CH in diets with no lipid supplementation improves feed efficiency of lactating cows	[63]

BW: Body weight; DM: Dry matter; OM: Organic matter; DMI: Dry matter intake; IVDMD: in vitro dry matter digestibility; UFA: Unsaturated fatty acids.