Variations in Per Cent of Protein, Milk Fat, and Solids-not-fat between Milkings and during the Milking Process

A total of 1,290 individual evening and morning milk samples in 11 herds of three breeds was tested for protein, solids-not-fat, and milk fat. Morning sample means were lower than evening samples for all components, milk fat 0.73% lower, solids-not-fat 0.11%, and protein 0.03%; whereas, milk weights were 4.21 lb higher. These differences and those between herds, herds by time of day and breed were all statistically highly significant. The differences between milking intervals of 12-12 and 10-14 hr were highly significant for milk fat and significantly different for solids-not-fat.