PSXIV-19 - Gas flux by calves from dams identified as either high or low methane emitters

Abstract: Eight (BW = 398 ± 8 kg) Red Angus heifers were used to examine the similarity between respiration gas parameters of dams and their offspring. Heifers’ CH₄, CO₂ emissions, and O₂ consumption were measured over a 70-day period using an automated head-chamber system that measured CO₂, CH₄, and O₂ fluxes. Heifers grazed native mixed-grass prairie and were given a daily supplement of 1.025 kg of alfalfa (Medicago sativa L.) pellets via the automated head-chamber system. Heifers were then artificially inseminated using sexed semen from a single Black Angus sire. The emissions of the offspring (BW = 284 ± 7 kg; 7 heifers, 1 steer) were measured at 11 months of age over a 70-day period. Like the dams, during their measurement period, the offspring grazed native mixed-grass prairie and were given a daily supplement of 1.025 kg of alfalfa pellets via the automated head-chamber system. Means for CH_4, CO₂ emissions, O₂ consumption, CH₄: CO2 ratio, respiratory quotient, and heat production were compared between dams and their calf by regressing maternal parameters on the parameters of the calves and using beginning dam and offspring BW as covariates. Methane emissions of the dams and their offspring had an excellent Pearson’s correlation (ρ = 0.79). Carbon dioxide emissions and O₂ consumption had an excellent Pearson’s correlation among dams and their offspring (ρ = 0.88 and 0.91, respectively). Heat production as well as the CH₄: CO2 ratio also had an excellent and good Pearson’s correlation (ρ = 0.91 and 0.67, respectively). The respiratory quotient correlation was good (ρ = 0.60). These results indicated that CH₄ and CO₂ emissions, O₂ consumption, the CH₄: CO2 ratio and HP production from offspring have a good Pearson’s correlation with the dam’s emissions. Hence, even with this small dataset, there is evidence that beef cattle can be selected for lower greenhouse gas emissions.