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Relationship between dairy cow genetic merit and profit on commercial spring calving dairy farms
Ramsbottom, George Cromie, A. R. Horan, Brendan Berry, Donagh
Ramsbottom, George
Cromie, A. R.
Horan, Brendan
Berry, Donagh
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2011-12
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Ramsbottom_EBIfarms.pdf
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G. Ramsbottom, A. R. Cromie, B. Horan and D. P. Berry (2012). Relationship between dairy cow genetic merit and profit on commercial spring calving dairy farms. animal, 6, pp 1031-1039. doi:10.1017/S1751731111002503
Abstract
Because not all animal factors influencing profitability can be included in total merit breeding indices for profitability, the
association between animal total merit index and true profitability, taking cognisance of all factors associated with costs and
revenues, is generally not known. One method to estimate such associations is at the herd level, associating herd average genetic
merit with herd profitability. The objective of this study was to primarily relate herd average genetic merit for a range of traits,
including the Irish total merit index, with indicators of performance, including profitability, using correlation and multiple
regression analyses. Physical, genetic and financial performance data from 1131 Irish seasonal calving pasture-based dairy farms
were available following edits; data on some herds were available for more than 1 year of the 3-year study period (2007 to 2009).
Herd average economic breeding index (EBI) was associated with reduced herd average phenotypic milk yield but with greater
milk composition, resulting in higher milk prices. Moderate positive correlations (0.26 to 0.61) existed between genetic merit for
an individual trait and average herd performance for that trait (e.g. genetic merit for milk yield and average per cow milk yield).
Following adjustment for year, stocking rate, herd size and quantity of purchased feed in the multiple regression analysis, average
herd EBI was positively and linearly associated with net margin per cow and per litre as well as gross revenue output per cow
and per litre. The change in net margin per cow per unit change in the total merit index was h1.94 (s.e.50.42), which was not
different from the expectation of h2. This study, based on a large data set of commercial herds with accurate information
on profitability and genetic merit, confirms that, after accounting for confounding factors, the change in herd profitability per
unit change in herd genetic merit for the total merit index is within expectations.