The Role of Chitosan as a Possible Agent for Enteric Methane Mitigation in Ruminants
, Sara Valencia-Salazar 2, Carmen Elisa Pinzón-Díaz 3, Esperanza Herrera-Torres 3, Carlos Fernando Aguilar-Pérez 1, Jacobo Arango 4 and Juan Carlos Ku-Vera 1,*
Garland Dahlke
Round 1
Reviewer 1 Report
General – I think you have done a good job of reviewing the topic, so most of my comments are editorial in nature.
many times you use the phrase ‘Experiments carried out to date’, or something like that. I believe that is intuitive (you can’t report on future experiments), so I suggest rephrasing to eliminate that redundancy.
Line Comment
19-20 “ … decreasing … are global commitments,…. “ or perhaps “ Effort to increase …. and decrease …. Is a global commitment. Either way, use ‘increase’ and ‘decrease’ , or ‘raise’ and ‘lower’
21 (VFA) the apostrophe s is unnecessary
22 rephrase to clarify that this is an enteric loss, before absorption and metabolism
45 “…a marine product. Like other compounds…”
46 “… of extraction and storage. In addition, it is important…”
50 “ … production systems. Chitosan is a promising…”
51 “… mitigating effects, but further research…”
54 Keywords should include ‘ruminant’ and ‘chitosan’
58 change ‘forcer’ to ‘effector’
60 “…livestock systems, particularly those that include ruminants {3}.”
68 – 71 I suggest adding a few words here to clarify that feeding grains (low fiber diets) causes more H2 captured as propionate versus lost as methane, whereas high forage diets cause less capture as propionate and more lost as methane; methanogens and high-fiber diets go together
77 “….inconsistent {15}, with variation attributed to “
81 “ … production of methane {3,10.18}; therefore, in the last decade…”
84 Start a new paragraph with “Plants produce….”
88 Delete “that shows”
90 “ A range of feed additives including antibiotics has achieved …”
101 When you say ‘laboratory’, do you mean in vitro? If so, say so.
102- 104 This statement needs citation and some clarification; what is the difference between ‘production parameters’ and ‘milk quality’? Do you mean feed efficiency? I suggest replacing ‘improve’ with change; milk quality is a nebulous descriptor.
122-124 “Recent research in animal nutrition has focused in its potential to modulate rumen fermentation in beef or dairy cattle {34-37} and nutrient digestibility in cattle {38}.”
125 “way at industrial scale..”
128 “way, considered environmentally safe, uses lactic acid…”
155-220 use present tense or past tense verbs consistently in these sections, e.g. ‘is’ or ‘was’, ‘gives’ or ‘gave’, ‘results; or ‘resulted’ ‘shows’ or showed’, “modifies’ or ‘modified’. I think past tense works better.
Table 1. In the dosage column, do your readers a favor and avoid use of percentages; just convert 5 to appropriate units, eg. mg/L
Author Response
Revisor 1.-
General – I think you have done a good job of reviewing the topic, so most of my comments are editorial in nature.
many times you use the phrase ‘Experiments carried out to date’, or something like that. I believe that is intuitive (you can’t report on future experiments), so I suggest rephrasing to eliminate that redundancy. Corrected
Line Comment
19-20 “ … decreasing … are global commitments,…. “ or perhaps “ Effort to increase …. and decrease …. Is a global commitment. Either way, use ‘increase’ and ‘decrease’ , or ‘raise’ and ‘lower’ (Increasing the efficiency of production systems and decreasing its environmental burden is a global commitment)
21 (VFA) the apostrophe s is unnecessary Corrected
22 rephrase to clarify that this is an enteric loss, before absorption and metabolism “thus methane mitigation is a strategy to reach those goals, by rechanneling metabolic hydrogen (H2) into volatile fatty acids (VFA) to reduce the loss of energy as methane in the rumen which ranges from 2% (grain rations) to 12% (poor-quality forage rations) of gross energy intake”.
45 “…a marine product. Like other compounds…” Corrected
46 “… of extraction and storage. In addition, it is important…” Corrected
50 “ … production systems. Chitosan is a promising…” Corrected
51 “… mitigating effects, but further research…” Corrected
54 Keywords should include ‘ruminant’ and ‘chitosan’ Corrected
58 change ‘forcer’ to ‘effector’ We revised and the most common word used is forcer than effector
60 “…livestock systems, particularly those that include ruminants {3}.” Corrected
68 – 71 I suggest adding a few words here to clarify that feeding grains (low fiber diets) causes more H2 captured as propionate versus lost as methane, whereas high forage diets cause less capture as propionate and more lost as methane; methanogens and high-fiber diets go together Corrected
Ration and type of feed affect the availability of metabolic hydrogen for CH4 synthesis in the rumen, feeding concentrate and grains (low fiber diets) reduce the population of methanogens (range 107 to 109 g-1) while more propionic acid is synthesized which utilize H2, whereas pasture-fed (methanogens 109 to 1010 g-1) ruminants yield higher concentrations of acetic acid in rumen liquor resulting in a higher availability of metabolic H2
77 “….inconsistent {15}, with variation attributed to “ Corrected
81 “ … production of methane {3,10.18}; therefore, in the last decade…” Corrected
84 Start a new paragraph with “Plants produce….” Corrected
88 Delete “that shows” Corrected
90 “ A range of feed additives including antibiotics has achieved …” Corrected
101 When you say ‘laboratory’, do you mean in vitro? If so, say so. Corrected (in vitro)
102- 104 This statement needs citation and some clarification; what is the difference between ‘production parameters’ and ‘milk quality’? Do you mean feed efficiency? I suggest replacing ‘improve’ with change; milk quality is a nebulous descriptor. Corrected
122-124 “Recent research in animal nutrition has focused in its potential to modulate rumen fermentation in beef or dairy cattle {34-37} and nutrient digestibility in cattle {38}.” Corrected
125 “way at industrial scale..” Corrected
128 “way, considered environmentally safe, uses lactic acid…” Corrected
155-220 use present tense or past tense verbs consistently in these sections, e.g. ‘is’ or ‘was’, ‘gives’ or ‘gave’, ‘results; or ‘resulted’ ‘shows’ or showed’, “modifies’ or ‘modified’. I think past tense works better. Corrected
Table 1. In the dosage column, do your readers a favor and avoid use of percentages; just convert 5 to appropriate units, eg. mg/L Corrected
Reviewer 2 Report
Regarding the opening sentence -Ruminants are not a major cause of green house gas emissions. Plant fiber degradation is. This will happen if there are ruminants or not. Ruminants can capture some of what is released in the process. Get this fact right.
Methane mitigation occurs with introducing starch or sugar into the ruminant diet, why wasn't chitosan impact compared to what occurs when grain is introduced ?
Regarding lines 155-165-I'm not sure the explanation is very clear or correct. Anything that shifts vfa production to more proprionate and less acetate will reduce methane production.
Lines 187-188--what do you mean that there is no change in vfa production, after you had just written that there was a shift to more proprionate production?
Author Response
Revisor 2.-
Regarding the opening sentence -Ruminants are not a major cause of green house gas emissions. Plant fiber degradation is. This will happen if there are ruminants or not. Ruminants can capture some of what is released in the process. Get this fact right. Corrected
Ruminant husbandry is one the largest contributors to greenhouse gas emissions from the agriculture sector, particularly of methane gas, which is a byproduct of anaerobic fermentation of structural and non-structural carbohydrates in the rumen.
Methane mitigation occurs with introducing starch or sugar into the ruminant diet, why wasn't chitosan impact compared to what occurs when grain is introduced ?
Lines 198-200 Thus, chitosan seems to work in the rumen much in the way as when grain (starch) is incorporated in the ration, by shifting the pattern of fermentation to a more propionic acid type of fermentation.
Regarding lines 155-165-I'm not sure the explanation is very clear or correct. Anything that shifts vfa production to more proprionate and less acetate will reduce methane production.
Lines 162 – 172 - Corrected
Chitosan has shown effects on feed intake, digestion, fermentation, and enteric methane production, however, results generally disagree between in vitro and in vivo studies (Table 1; Figure 3). In in vitro tests, it was found, Belanche [39] that chitosan changed rumen fermentation pattern and increased propionate production, decreasing cellulolytic bacteria, such as Fibrobacter, Butyrivibrio and Ruminococcus, and hemicellulolytic bacteria such as Eubacterium and increased amylolytic bacteria. This led us to speculate that the electrostatic interaction of chitosan and the destabilization of the cell membrane inhibited methanogens or metabolic pathways of methane synthesis and reduced methane production by 10 to 42 %, increasing propionic acid, and lactate as fermentation products as a result of the use of chito-oligosaccharides as carbon sources by rumen microbiota [53].
Lines 187-188--what do you mean that there is no change in vfa production, after you had just written that there was a shift to more proprionate production? Corrected
Lines 193 – 194 Chitosan modified the rumen fermentation pattern by increasing propionic acid and decreasing the acetate:propionate ratio [28,29,59,60].
