Variation in the concentration of long chain free fatty acids in equine plasma over 24 hours

The primary aim of this study was to examine the within-day variation in the concentration of total and individual long chain free fatty acids (C > 14) in normally fed horses. Plasma samples were collected over a 24 h period from 12 resting horses during three separate sessions (six horses in the first session and three in the second and third). Samples were analysed for individual long chain free fatty acids (FFA) and glucose. During normal feeding, the predominant FFA in plasma were palmitic (C16:0), linoleic (C18:2), oleic (C18:1), stearic (C18:0) and linolenic (C18:3). Together these acids constituted over 90% of the total concentration. Other FFA present were myristic (C14:0) and palmitoleic (C16:1) both of which constituted < 5% of the total concentration. Ten out of the 12 horses sampled exhibited an early morning increase in FFA (P < 0.001) localized around 0700 h and which was independent of feeding. The mean concentration of total FFA increased 4.5 fold (range 2.0-8.5) between 0400 and 1000 h. The predominant FFA showed the largest increase.