Changes in plasma triglyceride fatty acids during lactation.

Total blood plasma lipid and plasma triglyceride fatty acids were analyzed at an average of 33, 89, and 139 days of lactation (ranges 20 to 57, 52 to 129, and 122 to 157 days for periods I, II, and III) for 35 Holstein cows in their second or later lactation. Average milk production in the test periods was 35.7, 30.3, and 25.5 kg/day. Lipid analysis was part of a study comparing methionine hydroxy analog or sulfur for lactating cows with effects of treatment and time separated statistically. Cows fed methionine analog had a lower percent palmitate in the triglyceride fatty acid, but there was no other treatment effect. There were significant changes with time in percent total lipid and triglyceride fatty acid. Total lipid averaged 424, 526, and 529 mg/dl. Average percents of measured triglyceride fatty acid and differences with stage of lactation were: myristic, 2.96; palmitic, 27.52, I greater than II or III; palmitoleic, 2.83, I greater than II or III; stearic, 38.58 I greater than II greater than III, oleic, 20.75, I greater than II or III; and linoleic, 4.59.