Prefeeding plasma acetoacetate and glucose in healthy, lactating heifers. Variations related to milk yield, metabolic balances and stage of lactation
Halse, K.; Tveit, B.
Acta Veterinaria Scandinavica 35(3): 243-255
1994
ISSN/ISBN: 0044-605X PMID: 7847193 Document Number: 434298
When measured before morning feeding plasma acetoacetate (ACAC) increased and glucose (GL) decreased significantly with increasing milk yield (fat corrected, FCM) within 2 groups of half-sister related heifers which did not suffer from clinical ketosis. The groups received respectively A: 7 kg and B: 4 kg/d of concentrates in addition to grass silage ad libitum (each group 88 animals). Correlation coefficients of the same magnitude between the 3 variables mentioned were obtained in the 1st and 3rd month of lactation in spite of a narrowing of the ACAC range from 0.024 - 0.66 to 0.019 - 0.16 mmol/l. Reproducibility of differences between animals in milk yield and in the plasma components was evidenced by significant correlations between measurements in the 1st and 3rd month. The B-animals produced 2.4 kg/d less FCM than the better fed A group (A, 1st month of lactation 19.8 +- 3.1 kg/d) while the mean values for ACAC and GL remained practically unaffected by the difference in feeding. B cows gave consistently 5-6 % lower GL means (p lt 0.01) than A animals with identical yields. Animals which showed marked ACAC increment during the first 5-6 weeks of lactation produced 3-4 kg More FCM/d than equally fed animals with constantly low ACAC levels. The estimated energy deficit of this ketonaemic, high-producing category corresponded to the production of 4.5 - 6 kg FCM/d from body reserves. Low ACAC values ( lt 0.05 mmol/l) were reproduced with a standard deviation of +- 4% with the automated nitroprusside method described.