The effect of diet and genotype on metabolic indicators of energy status in the periparturient cow were investigated. Fifty-six dairy cows of two different genotypes (Overseas Holstein-Friesian (OSHF) and New Zealand Holstein-Friesian (NZHF)) were randomly allocated to two dietary regimens. Half of each genotype group received a pasture/pasture silage diet pre-calving and a pasture diet post-calving, while the other half received a total mixed ration (TMR) pre- and post-calving. Compared with NZHF, OSHF had higher concentrations of plasma non-esterified fatty acids (NEFA; P<0.05) and glutamic acid dehydrogenase (GDH; P=0.09), an indicator of liver fat infiltration, 30 d post-calving. Genotype did not affect the concentration of either b-hydroxybutyrate (BHBA) or glucose in plasma. Cows grazing pasture pre-calving had greater (P<0.05) BHBA concentrations, but plasma NEFA concentration and liveweight loss during the first 30 days of lactation were not different. In summary, a pre-calving TMR did not appear to improve the metabolic energy status of the cow pre-calving. These results suggest that provided sufficient nutrients are supplied in the diet, the homeorhetic mechanisms within the cow allow adaption to very different diets. This implies that an all-forage diet pre-calving is sufficient for dairy cows fed forage post-calving.
Proceedings of the New Zealand Society of Animal Production, Volume 62, Palmerston North, 252-256, 2002
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