Table 4.

The phase and amplitude of a cosine function with a 24 h period fit to milk yield and composition, milk fatty acid profile, and select plasma metabolites and hormones of cows fed once per day or in four equal meals when milked every 6 h.

Parameter	Trt1	Phase2 (h)	Amplitude3	P‐value4
Milk production
Milk yield, kg/6 h	1× Fed	0336	0.55	<0.001
	4× Fed	0648*	0.50	<0.001
Fat, %	1× Fed	1500	0.34	<0.001
	4× Fed	1342*	0.24*	<0.001
Fat yield, g/6 h	1× Fed	01430	21	<0.01
	4× Fed	2324*	22	0.02
Protein, %	1× Fed	1718	0.06	<0.001
	4× Fed	1948*	0.03*	<0.001
Protein yield, g/6 h	1× Fed	0148	9.1	<0.05
	4× Fed	0630*	14*	<0.001
Milk FA by source
∑ < 16 C,% FA	1× Fed	2350	0.91	<0.001
	4× Fed	0520*	0.28*	0.29
∑ 16 C,% FA	1× Fed	2338	0.61	<0.01
	4× Fed	0242*	0.43*	0.01
∑ > 16 C,% FA	1× Fed	1235	1.09	<0.001
	4× Fed	1133	0.25*	0.50
Plasma hormones and metabolites
Glucose, mg/dL	1× Fed	0048	2.5	<0.001
	4× Fed	0912*	0.68*	0.35
Insulin, μIU/mL	1× Fed	1736	8.0	<0.001
	4× Fed	1542*	2.7*	<0.001
NEFA, μEq/L	1× Fed	0530	21.2	<0.001
	4× Fed	700*	7.7*	0.12
BUN, mg/dL	1× Fed	1000	1.2	<0.001
	4× Fed	1130*	0.39*	0.10

¹Treatments (Trt) were cows fed once a day (1× Fed) or in four equal meals every 6 h (4× Fed). n = 17 per treatment.

²Phase is the time (h) of peak of a cosine function with a 24 h period. * Indicates 4× Fed different from 1× Fed (P <0.05).

³Amplidute is the difference from peak to mesor of a cosine function with a 24 h period. Units shown next to parameter.

⁴Zero amplitude test of the cosine function with a 24 h period for each treatment.