Diurnal Variations in Milk Yield, Fat Yield, Milk Fat Percentage, and Milk Protein Percentage of Holstein-Friesian Cows

Abstract

Milk from 51 Holstein cows was weighed and sampled every 12 hr for 15 days. There were significant diurnal variations in milk and fat yield and fat and protein percentages. Mean milk yield was greater by .65 kg .05 in the morning than in the evening while mean fat yield was greater by .017 kg .004, mean fat percentage higher by .321% .020, and mean protein percentage higher by .086% .003 in the evening than in the morning.