Search

On-farm methane (CH 4 ) emissions need to be estimated accurately so that the mitigation effect of recommended practices can be accounted for. In the present study prediction equations for enteric CH 4 have been developed in lieu of expensive animal measurement approaches. Our objectives were to: (1) compile a dataset from individual beef cattle data for the Latin America and Caribbean (LAC) region; (2) determine main predictors of CH 4 emission variables; (3) develop and cross-validate prediction models according to dietary forage content (DFC); and (4) compare the predictive ability of these newly-developed models with extant equations reported in literature, including those currently used for CH 4 inventories in LAC countries. After outlier's screening, 1100 beef cattle observations from 55 studies were kept in the final dataset (∼ 50 % of the original dataset). Mixed-effects models were fitted with a random effect of study. The whole dataset was split according to DFC into a subset for all-forage (DFC = 100 %), high-forage (94 % ≥ DFC ≥ 54 %), and low-forage (50 % ≥ DFC) diets. Feed intake and average daily gain (ADG) were the main predictors of CH 4 emission (g d -1 ), whereas this was feeding level [dry matter intake (DMI) as % of body weight] for CH 4 yield (g kg -1 DMI). The newly-developed models were more accurate than IPCC Tier 2 equations for all subsets. Simple and multiple regression models including ADG were accurate and a feasible option to predict CH 4 emission when data on feed intake are not available. Methane yield was not well predicted by any extant equation in contrast to the newly-developed models. The present study delivered new models that may be alternatives for the IPCC Tier 2 equations to improve CH 4 prediction for beef cattle in inventories of LAC countries based either on more or less readily available data., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Accurate estimates of methane (CH4) production by cattle in different contexts are essential to developing mitigation strategies in different regions. We aimed to: (i) compile a database of CH4 emissions from Brazilian cattle studies, (ii) evaluate prediction precision and accuracy of extant proposed equations for cattle and (iii) develop specialized equations for predicting CH4 emissions from cattle in tropical conditions. Data of nutrient intake, diet composition and CH4 emissions were compiled from in vivo studies using open-circuit respiratory chambers, SF6 technique or the GreenFeed® system. A final dataset containing intake, diet composition, digestibility and CH4 emissions (677 individual animal observations, 40 treatment means) obtained from 38 studies conducted in Brazil was used. The dataset was divided into three groups: all animals (GEN), lactating dairy cows (LAC) and growing cattle and non-lactating dairy cows (GCNL). A total of 54 prediction equations available in the literature were evaluated. A total of 96 multiple linear models were developed for predicting CH4 production (MJ/day). The predictor variables were DM intake (DMI), gross energy (GE) intake, BW, DMI as proportion of BW, NDF concentration, ether extract (EE) concentration, dietary proportion of concentrate and GE digestibility. Model selection criteria were significance (P < 0.05) and variance inflation factor lower than three for all predictors. Each model performance was evaluated by leave-one-out cross-validation. The Intergovernmental Panel on Climate Change (2006) Tier 2 method performed better for GEN and GCNL than LAC and overpredicted CH4 production for all datasets. Increasing complexity of the newly developed models resulted in greater performance. The GCNL had a greater number of equations with expanded possibilities to correct for diet characteristics such as EE and NDF concentrations and dietary proportion of concentrate. For the LAC dataset, equations based on intake and animal characteristics were developed. The equations developed in the present study can be useful for accurate and precise estimation of CH4 emissions from cattle in tropical conditions. These equations could improve accuracy of greenhouse gas inventories for tropical countries. The results provide a better understanding of the dietary and animal characteristics that influence the production of enteric CH4 in tropical production systems.

Supplementation of grass-fed cattle with low-cost feeding alternatives may be an attractive way to improve efficiency of cattle production. We hypothesized that inclusion of crude glycerin (CG) in supplements provided to grass-fed cattle could improve feed conversion without negative effects on growth performance while reducing methane emissions. Our hypothesis was tested using Nellore bulls grazing tropical pasture ( = 50; initial BW of 427 ± 19.41 kg; age of 17 ± 2 mo) supplemented with increasing concentrations (0, 70, 140, 210, and 280 g/kg DM basis of supplement) of CG and corn gluten replacing corn grain. A second experiment was conducted using 10 ruminally cannulated Nellore steers (490.1 ± 47.8 kg BW; age of 25 mo) to assess the impact of different concentrations of glycerin in the supplement on ruminal VFA concentration. Inclusion of CG did not affect total DMI ( = 0.53), DMI of forage ( = 0.41), supplement DMI ( = 0.47), organic matter intake ( = 0.50), crude protein intake ( = 0.24), NDF intake ( = 0.49), GE intake ( = 0.50), NDF digestibility ( = 0.17), final BW ( = 0.17), LM area ( = 0.50), rib fat thickness ( = 0.87), or carcass gain ( = 0.13). The inclusion of CG in the supplement linearly increased ( < 0.001) the molar proportion of propionate, butyrate, and valerate; linearly decreased acetate ( = 0.001); and did not affect the molar proportion of isovalerate ( = 0.31) and isobutyrate ( = 0.63), thereby reducing the acetate to propionate ratio ( < 0.001). The increase of CG supplementation of young bulls in pasture had a quadratic effect on BW gain ( = 0.002), with lower BW gain with 140 g/kg DM of CG in the supplement and tended ( = 0.06) to improve G:F. Inclusion of CG did not affect ruminal CH emission expressed in kilograms per year ( = 0.74), grams per kilogram of DMI ( = 0.69), and grams per kilogram of carcass gain ( = 0.48). Crude glycerin supplementation was not effective as a strategy to reduce CH emission in grass-fed cattle. However, CG can be effectively used as a partial energy source in supplement of grazing cattle, promoting an improvement in feed efficiency.

Intake of tropical grass forages alone is generally insufficient to avoid nutrition imbalances and reduced animal performance; therefore, supplementation is often recommended. The hypothesis of the present study is that when combined with fat, soybean hulls (SH) could replace corn as a source of energy, reducing methane production without affecting animal performance. This study evaluated the effects of starch-based supplementation level combined with oil on intake, digestibility, performance, and methane emissions of growing Nellore bulls (P = 44; initial BW = 250.69 ± 27 kg) fed cv. Xaraés during the rainy season. There were no interactions between starch level and oil supplementation with regard to intake of DM (P = 0.67), forage DM (P = 0.55), supplement DM (P = 0.14), OM (P = 0.66), CP (P = 0.74), NDF (P = 0.50), ether extract (EE; = 0.47), and GE ( P= 0.68). The intake of EE was greater for animals supplemented with oil than those fed supplements without oil (P < 0.01). There were no interactions between starch level and oil supplementation on digestibility of DM (P= 0.18), OM (P = 0.11), NDF (P= 0.42), and EE (P = 0.14). Moreover, there was interaction between starch and oil supplementation on GE (P < 0.01). Independent of starch level used, the addition of oil decreased the digestibility of OM (P = 0.04) and NDF (P = 0.03). There were no main effects of starch level, oil, or interaction between starch and oil for initial BW (P = 0.10), final BW (P = 0.94), ADG (P = 0.40), feed efficiency (P= 0.37), and carcass gain (P = 0.38). There was no interaction between starch-based supplementation level and oil on methane emissions when expressed in grams per day (P = 0.77), kilograms per year (P = 0.77), grams per kilogram DMI (P = 0.53), and grams per kilogram carcass gain (P= 0.31). There was, however, an interaction (P = 0.04) between starch level and oil on methane emissions when corrected for NDF intake. Additionally, oil decreased enteric methane emission for intake of GE (P = 0.04) and EE (P < 0.01) of animals fed with starch level. Soybean hulls have an estimated feeding value similar to that of corn. The use of oil supplementation may be effective to reduce enteric methane emission of Nellore bulls raised on pasture.

The present study was conducted to evaluate the effect of lipids with different fatty acid profiles on the intake, performance, and enteric CH4 emission of Nellore steers. A total of 45 Nellore animals with an average initial BW of 419 ± 11 kg (at 15 ± 2 mo) were distributed in a completely randomized design consisting of 5 treatments and 9 replicates. The roughage feed was maize silage (600 g/kg on a DM basis) plus concentrate (400 g/kg on a DM basis). The dietary treatments were as follows: without additional fat (WF), palm oil (PO), linseed oil (LO), protected fat (PF; Lactoplus), and whole soybeans (WS). The lipid source significantly affected (P < 0.05) nutrient intake. The greatest intakes of DM, OM, and CP were observed in the animals that were fed the WF or PF diets, and the lowest intakes were observed in the animals that were fed the PO diet. Intake of NDF decreased (P < 0.05) with the addition of PO. Enteric methane emission (g/kg DMI) was reduced by an average of 30% when the animals were fed diets containing WS, LO, and PO (P < 0.05), and these diets caused a larger reduction in the energy loss in the form of methane compared to those without added fat and with added PF (3.3 vs. 4.7%). The different fatty acid profiles did not affect the backfat thickness or the loin eye area of the animals (P > 0.05). However, animals fed PO displayed lower daily weight gain (0.36 kg/d), feed efficiency (0.08 kg ADG/kg DM), HCW (245 kg), and hot yield percentage (52.6%) compared to animals that were fed the other diets. Therefore, PO compared to the other lipid sources used in this study reduces intake, performance, feed efficiency, and carcass yield. Therefore, PO is not suggested for feedlot-finished animals.