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Successful mitigation efforts entail accurate estimation of on-farm emission and prediction models can be an alternative to current laborious and costly in vivo CH4 measurement techniques. This study aimed to: (1) collate a database of individual dairy cattle CH4 emission data from studies conducted in the Latin America and Caribbean (LAC) region; (2) identify key variables for predicting CH4 production (g d−1) and yield [g kg−1 of dry matter intake (DMI)]; (3) develop and cross-validate these newly-developed models; and (4) compare models' predictive ability with equations currently used to support national greenhouse gas (GHG) inventories. A total of 42 studies including 1327 individual dairy cattle records were collated. After removing outliers, the final database retained 34 studies and 610 animal records. Production and yield of CH4 were predicted by fitting mixed-effects models with a random effect of study. Evaluation of developed models and fourteen extant equations was assessed on all-data, confined, and grazing cows subsets. Feed intake was the most important predictor of CH4 production. Our best-developed CH4 production models outperformed Tier 2 equations from the Intergovernmental Panel on Climate Change (IPCC) in the all-data and grazing subsets, whereas they had similar performance for confined animals. Developed CH4 production models that include milk yield can be accurate and useful when feed intake is missing. Some extant equations had similar predictive performance to our best-developed models and can be an option for predicting CH4 production from LAC dairy cows. Extant equations were not accurate in predicting CH4 yield. The use of the newly-developed models rather than extant equations based on energy conversion factors, as applied by the IPCC, can substantially improve the accuracy of GHG inventories in LAC countries. Made available in DSpace on 2022-09-16T18:05:48Z (GMT). No. of bitstreams: 1 PredictionOfEntericMethaneProductionAndYieldInDairyCattleUsingALatinAmericaAndCaribbeanDatabase.pdf: 8419936 bytes, checksum: d329346d1445b50492a3d593140a2385 (MD5) Previous issue date: 2022

Simple Summary The nutrients requirements of dairy cattle is the most used system to formulate dairy cattle diets. However, these guidelines were developed based on research using mostly purebred Holstein in temperate conditions and did not determine nutrient requirements of crossbred Holstein × Gyr or Gyr animals raised in a tropical environment. Studies conducted in tropical conditions demonstrated that breed largely affected the nutrient requirements of crossbred and Gyr cattle, which limits the use of this system. Our objective was to evaluate the effects of two feeding levels and three breed compositions on nutrient intake, digestibility, performance, and methane emissions of prepubertal (10-month-old) dairy heifers. We observed that feeding diets to allow gains of 400 and 800 g/day resulted in greater daily gain than the formulated, overestimating the nutritional requirements of the heifers. Overall, breed composition did not affect dry matter intake, but it did result in differences in nutrients digestibility coefficients and feed efficiency. Feeding prepubertal heifers above maintenance requirements was the main driver in reducing CH4 intensity in confinement conditions. Abstract The dairy Nutrients Requirements of Cattle (NRC) was developed using data from purebred Holsteins and it might not accurately predict the performance of crossbred cattle. Our objectives were to evaluate the effects of two feeding levels (FLs) and three breed compositions (BCs) on nutrient intake, digestibility, performance, and methane (CH4) emissions of prepubertal dairy heifers. We used thirty-six heifers from three BCs: purebred Holstein (H), purebred Gyr (G), and F1 Holstein × Gyr (HG). Each BC had 12 animals and the experiment was designed as twelve incomplete three by three Latin squares, in a factorial arrangement three by two, with three BCs and two FLs (400 and 800 g/day). Total tract nutrient digestibility was determined using total fecal collection and DMI was individually measured. The data were analyzed using the PROC MIXED in SAS. Dry matter intake of all nutrients increased from the medium to high feeding level and the nutrients digestibility coefficients did differ among BCs. Achieved body weight gain in the medium FL treatment was greater than those predicted using the NRC, suggesting that crossbred and Gyr heifers have similar performance to Holsteins. Breed composition does not influence body weight gain of confined dairy heifers, but Holstein heifers fed a medium FL had higher feed efficiency and reduced CH4 emissions intensity.