Table 4.

Effects of level and source of fat in the diet beef cows during gestation, time and treatment × time interaction on performance, partial milk yield, and milk composition during the first 42 d of lactation

	Treatment1				Days relative to calving				P-value2
Item	LF (n = 10)	CAN (n = 10)	FLX (n = 10)	SEM	0	21	42	SEM	LF vs. HF	CAN vs. FLX	D	trt × d
Performance of cows3
BW, kg	694	691	701	13.7	705	695	686	12.9	0.72	0.28	<0.01	0.18
Cumulative ADG, kg/d	−0.49	−0.53	−0.46	0.44	–	−0.54	−0.45	0.44	0.93	0.63	0.21	0.54
BCS	2.63	2.49	2.53	0.07	2.66	2.56	2.44	0.07	<0.01	0.32	<0.01	0.75
Change	−0.20	−0.14	−0.15	0.09	–	−0.10	−0.22	0.08	0.35	0.92	0.04	0.68
Thin, % of cows	3.7	16.7	6.7	8.34	2.9	6.2	21.6	9.51	0.04	0.09	<0.01	0.84
Optimal, % of cows	96.3	83.3	93.3	8.31	97.1	93.8	78.4	8.86	0.07	0.06	<0.01	0.65
Over conditioned, % of cows	0.0	0.0	0.0	–	0.0	0.0	0.0	–	–	–	–	–
NEFA, µEq/L	1,043	1,032	1,014	92.0	1,049	1,038	1,002	91.9	0.73	0.78	0.75	0.28
BHBA, mg/dL	11.3	10.8	11.4	0.64	10.7	11.3	11.4	0.59	0.75	0.31	0.24	0.39
Milk parameters4
12-h milk yield, kg	5.9	6.2	5.8	0.43	–	5.8	6.1	0.39	0.74	0.23	0.14	0.44
Fat, %	3.50	3.51	3.66	0.17	–	3.24	3.87	0.12	0.70	0.54	<0.01	0.97
Fat yield, g	217	224	214	18.9	–	193	243	15.7	0.91	0.66	<0.01	0.78
Protein, %	3.07	3.11	3.01	0.07	–	3.22	2.90	0.07	0.82	0.03	<0.01	0.81
Protein yield, g	183	193	171	16.6	–	187	177	15.7	0.91	0.08	0.23	0.54
Lactose, %	4.63	4.57	4.64	0.04	–	4.53	4.70	0.03	0.63	0.28	<0.01	0.23
Lactose yield, g	273	286	264	20.0	–	262	287	17.9	0.88	0.25	0.01	0.83
Total solids, %	12.2	12.2	12.3	0.20	–	12.0	12.5	0.16	0.78	0.67	<0.01	0.89
Total solids yield, g	818	890	796	62.4	–	706	963	49.5	0.75	0.31	<0.01	0.56
Milk energy, Mcal/kg	0.68	0.68	0.69	0.02	–	0.66	0.70	0.01	0.72	0.57	<0.01	0.97
Milk energy yield, Mcal	4.09	4.26	3.97	0.29	–	3.85	4.37	0.24	0.94	0.37	<0.01	0.69
MUN, mg/dL	11.6	11.2	11.2	2.37	–	11.7	11.0	2.35	0.42	0.99	0.07	0.73

¹LF = cows fed a low-fat diet; CAN = cows fed a high-fat diet including a canola seed–based pelleted feed; FLX = cows fed a high-fat diet including a flaxseed-based pelleted feed.

²HF = average of CAN and FLX.

³Thin = % of cows with a BCS < 2.5; Optimal = % of cows with a 2.5 ≤ BCS ≤ 3; Over conditioned = % of cows with BCS > 3; NEFA = nonesterified fatty acids; BHBA = β-hydroxy butyrate.

⁴12-h milk yield = milk yield estimated for 4 quarters over 12 h. Milk energy yield (Mcal) was calculated from milk composition (NRC, 2000) based on a predicted four-quarter 12-h yield. MUN = milk urea nitrogen.