The US dairy herd comprises 90.1% Holstein and
5.3% Jersey cattle (USDA, 2007a), 2 breeds that display very different performance characteristics, notably
a higher milk yield in the Holstein breed compared with
a higher milk nutrient density and a lesser BW in the
Jersey breed. The environmental impact of recombinant bovine somatotropin (rbST) has been evaluated
in Holstein populations (Johnson et al., 1992; Dunlap
et al., 2000; Capper et al., 2008) but the effect in smallframed dairy breeds with a generally lower daily milk
yield has not yet been defined. In this study, we used a
deterministic model to assess the environmental impact
of producing sufficient milk to yield 500,000 t of Cheddar cheese from either the Jersey or Holstein populations using national data for production year 2009,
with and without rbST supplementation.
The US dairy herd comprises 90.1% Holstein and 5.3% Jersey cattle (USDA, 2007a), 2 breeds that display very different performance characteristics, notably a higher milk yield in the Holstein breed compared with a higher milk nutrient density and a lesser BW in the Jersey breed. The environmental impact of recombinant bovine somatotropin (rbST) has been evaluated in Holstein populations (Johnson et al., 1992; Dunlap et al., 2000; Capper et al., 2008) but the effect in smallframed dairy breeds with a generally lower daily milk yield has not yet been defined. In this study, we used a deterministic model to assess the environmental impact of producing sufficient milk to yield 500,000 t of Cheddar cheese from either the Jersey or Holstein populations using national data for production year 2009, with and without rbST supplementation.
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