Monitoring adrenal activity in dairy cows under various feeding
regimens using faecal glucocorticoid metabolites
C.J. MORROW, E.S. KOLVER, K.A. MACDONALD, G.A. VERKERK AND L.R.
MATTHEWS
AgResearch Ruakura and Dexcel Ltd., Private Bag 3123,
Hamilton, NZ.
E-Mail:
Proceedings of the New Zealand Society of Animal Production 2001. 61:
52-55
Adrenal activity in cattle can be measured by changes in plasma
glucocorticoid concentrations. Cows treated with synthetic
adrenocorticotrophic hormone (ACTH) to stimulate the adrenal cortex
exhibited elevated plasma cortisol concentrations for 4-5h.
Concentrations of faecal glucocorticoid metabolites (FGM) peaked between
8-9.5h after ACTH treatment, 2.5 fold higher than basal (P<0.05) and
remained elevated for 13h (range, 11.1-16.1h). Faecal glucocorticoid
concentrations were monitored in two strains of Holstein Friesian (HF)
dairy cows farmed in New Zealand under two systems: NZ pastoral and
North American concentrate-based. The overseas (OS) and New Zealand (NZ)
HF were fed a pasture-based diet (Grass) or a total mixed ration (TMR)
throughout lactation. Faecal samples were collected on four occasions
during lactation. Faecal glucocorticoid concentrations of the cows fed
Grass were consistently higher (P<0.05) than cows fed TMR. There was
also a significant genotype effect; FGM concentrations of the NZ HF cows
were higher than OS HF cows (P<0.05). In a separate study, no obvious
trends were evident in FGM in NZ HF grazing pasture at three stocking
rates (2.2, 3.2, 4.3 cows per hectare). Measuring FGM can be used to
monitor acute adrenal activity in cows, but is more difficult to
interpret as a measure of chronic stress.
Keywords: NZSAPAB;
dairy cows; faecal; cortisol; ACTH; stress
Last Updated 7/08/01
