Effects of dry matter intake and metabolisable energy density on the concentrations of insulin-like growth factor-I (IGF-I) and blood metabolites in pasture-fed dairy cows
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Date
2009
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Journal ISSN
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Publisher
Ghanaian Journal of Animal Science
Abstract
Blood metabolites including glucose, NEFA, BHB and urea could be used as indicators of nutritional or energy balance in an animal. The plasma concentrations of IGF-1 may also be a sensitive measure of dietary changes. The relationship between IGF-I and the above metabolites in the blood, and their potential in monitoring dietary effects in 32 pasture-fed Holstein-Friesian cows in early lactation were investigated in a 5-wk study. The cows were randomly assigned to four dietary sub-groups and fed one of 4 rations varying in dry matter (DM) and metabolizable energy (ME) concentration (LL: 16.6 kg DM and 174 MJ ME; HL: 17.3 kg DM and 181 MJ ME; LH: 15.4 kg DM and 183.1 MJ ME; HH: 17.9 kg DM and 213.3 MJ ME, with the first letter indicating DM and the second ME). The four rations consisted of pasture, hay and pelleted cereal grain. Plasma IGF-I concentrations were positively associated with glucose (R = 0.587; P<0.01) but negatively associated with BHB (R = - 0.588; P<0.01) and urea (R = -0.372; P<0.05) concentrations at d 35. The relationship between IGF-1 and NEFA concentration was not statistically significant (R = 0.007: P.00.05) at d 35. ME density had grater influence on the proportional changes in blood IGF-1, glucose, BHB and urea concentrations, than changes associated with DM intake. Plasma IGF-I had a higher R2 estimate in its model than any other metabolite at d 14 (R2 = 0.528) and d 35 (R2 = 0.649) of the study, except for BHB at d 35 (R2 = 0.708). The changes in IGF-1 with diet were over a greater range than with the other metabolites, and were indicative of a stronger association of IGF-I with dietary changes.
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Keywords
Blood Metabolites, Dairy Cow, Energy Balance, IFG-I
Citation
Ghanaian Journal of Animal Science 1(4): 68-77