Corrigendum to “A new approach for improving emission factors for enteric methane emissions of cattle in smallholder systems of East Africa – Results for Nyando, Western Kenya” [Agricultural systems volume (161) pp72–80]

The authors regret that a recent examination of our data for other purposes has led to the discovery of an error in the calculation of the Metabolic Energy Requirement for maintenance (MERm) in the original calculations of this article. This was occasioned by the application of an incorrect constant to the calculation of MERm to male animals >2 yrs., male animals 1-2 yrs. and calves and had the effect of increasing the Emission Factors (EF) for these classes of animals by 3–29%. The corrected table of EFs for all classes of animal is reproduced directly below

Genetic and environmental variation in methane emissions of sheep at pasture

A total of 2,600 methane (CH4) and 1,847 CO2 measurements of sheep housed for 1 h in portable accumulation chambers (PAC) were recorded at 5 sites from the Australian Sheep CRC Information Nucleus, which was set up to test leading young industry sires for an extensive range of current and novel production traits. The final validated dataset had 2,455 methane records from 2,279 animals, which were the progeny of 187 sires and 1,653 dams with 7,690 animals in the pedigree file. The protocol involved rounding up animals from pasture into a holding paddock before the first measurement on each day and then measuring in groups of up to 16 sheep over the course of the day. Methane emissions declined linearly (with different slopes for each site) with time since the sheep were drafted into the holding area. After log transformation, estimated repeatability (rpt) and heritability (h(2)) of liveweight-adjusted CH4 emissions averaged 25% and 11.7%, respectively, for a single 1-h measurement. Sire × site interactions were small and nonsignificant. Correlations between EBV for methane emissions and Sheep Genetics Australia EBV for production traits were used as approximations to genetic correlations. Apart from small positive correlations with weaning and yearling weights (r = 0.21-0.25, P < 0.05), there were no significant relationships between production trait and methane EBV (calculated from a model adjusting for liveweight by fitting separate slopes for each site). To improve accuracy, future protocols should use the mean of 2 (rpt = 39%, h(2) = 18.6%) or 3 (rpt = 48%, h(2) = 23.2%) PAC measurements. Repeat tests under different pasture conditions and time of year should also be considered, as well as protocols measuring animals directly off pasture instead of rounding them up in the morning. Reducing the time in the PAC from 1 h to 40 min would have a relatively small effect on overall accuracy and partly offset the additional time needed for more tests per animal. Field testing in PAC has the potential to provide accurate comparisons of animal and site methane emissions, with potentially lower cost/increased accuracy compared to alternatives such as SF6 tracers or open path lasers. If similar results are obtained from tests with different protocols/seasonal conditions, use of PAC measurements in a multitrait selection index with production traits could potentially reduce methane emissions from Australian sheep for the same production level

Vitamin A status of heifers fed a diet deficient in Beta Carotene

Introduction: Ruminants derive their retinol (vitamin A) requirements from β-carotene and generally have sufficient liver reserves to maintain healthy function through dry periods, but clinical vitamin A deficiency has been reported in cattle during prolonged drought (Hill et al. 2009). The level of endogenous reserves at which animals become symptomatic are unclear and manifestation of the disease seems highly variable (Jones et al. 1943). We characterised blood and liver retinol levels in\ud growing heifers from a common background, systematically deprived of dietary β-carotene.\ud \ud Material and Methods: Yearling Braham heifers (n=30) were fed a β-carotene deficient diet consisting of wheaten straw ad. lib and a wheat-based pellet, throughout the trial. Blood was collected monthly, liver tissue biopsied every 90d and weight recorded weekly. Retinol concentrations were determined by HPLC.\ud \ud Results and Discussion: LW increased from 179kg (SEM 2.66 kg) at Od to 306kg (SEM 4.15kg) at 176d. Initial serum and liver retinol concentrations decreased by 29% and 91% respectively, over the corresponding period (Fig. 1). No animals displayed signs of vitamin A deficiency during the depletion period. \ud \ud Decline in liver retinol over ~180d agreed with Kohlmeier and Burroughs (1970) for cattle fed dry-forage, but observed poor correlation between blood and liver retinol, except when critically low, suggesting serum retinol levels are not reliable indicators of Vitamin A reserves in young cattle