Is there a relationship between genetic merit and enteric methane emission rate of lactating Holstein-Friesian dairy cows?
The present study was undertaken to examine the effect of cow genetic merit on enteric methane (CH4) emission rate. The study used a data set from 32 respiration calorimeter studies undertaken at this Institute between 1992 and 2010, with all studies involving lactating Holstein-Friesian dairy cows. Cow genetic merit was defined as either profit index (PIN) or profitable lifetime index (PLI), with these two United Kingdom genetic indexes expressing the expected improvement in profit associated with an individual cow, compared with the population average. While PIN is based solely on milk production, PLI includes milk production and a number of other functional traits including health, fertility and longevity. The data set had a large range in PIN (n=736 records, -£30 to +£63) and PLI (n=548 records, -£131 to +£184), days in milk (18 to 354), energy corrected milk yield (16.0 to 45.6 kg/day) and CH(4) emission (138 to 598 g/day). The effect of cow genetic merit (PIN or PLI) was evaluated using ANOVA and linear mixed modelling techniques after removing the effects of a number of animal and diet factors. The ANOVA was undertaken by dividing each data set of PIN and PLI into three sub-groups (PIN:£15, PLI:£67) with these being categorised as low, medium and high genetic merit. Within the PIN and PLI data sets there was no significant differences among the three sub-groups in terms of CH(4) emission per kg feed intake or per kg energy corrected milk yield, or CH(4) energy (CH(4)-E) output as a proportion of energy intake. Linear regression using the whole PIN and PLI data sets also demonstrated that there was no significant relationship between either PIN or PLI, and CH(4) emission per kg of feed intake or CH(4)-E output as a proportion of energy intake. These results indicate that cow genetic merit (PIN or PLI) has little effect on enteric CH(4) emissions as a proportion of feed intake. Instead enteric CH(4) production may mainly relate to total feed intake and dietary nutrient composition.
1Agri-Food and Biosciences Institute,Hillsborough,Co. Down BT26 6DR,UK.
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Dong
1Agri-Food and Biosciences Institute,Hillsborough,Co. Down BT26 6DR,UK.
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Yan
1Agri-Food and Biosciences Institute,Hillsborough,Co. Down BT26 6DR,UK.
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Ferris
2Faculty of Life and Health Sciences,University of Ulster,Newtownabbey,Co. Antrim BT37 0QB,UK.
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McDowell
3Agri-Food and Biosciences Institute,Newforge,Co. Down BT9 5PX,UK.
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Gordon
D000818:Animals; D002417:Cattle / Q000235:genetics / Q000378:metabolism*; D004032:Diet / Q000662:veterinary; D002149:Energy Intake; D005260:Female; D007774:Lactation; D016014:Linear Models; D008697:Methane / Q000378:metabolism*; D008892:Milk / Q000378:metabolism*
D008697:Methane
Holstein-Friesian cow; calorimeter data; genetic merit; methane emission