Table 1.

Effect of first calving period on beef cow lifetime productivity

Item	Calving period1			SEM2	P value
	Period 1	Period 2	Period 3
Initial heifer, n	87	66	58
Age at first calving, d	731a	751b	778c	3.6	<0.01
Calving interval, d	376a	372a	358b	1.8	<0.01
Postpartum interval,3 d	95a	90a	76b	2.1	<0.01
Calf birth date, Julian day	107b	110b	119a	1.1	<0.01
Calf birth BW, kg	40	40	40	0.5	0.80
Calf age at weaning, Julian day	167a	164a	149b	2.0	<0.01
Calf weaning BW, kg	218a	217a	202b	2.5	<0.01
Pre-weaning ADG, kg/d	1.1ab	1.1a	1.0b	0.02	0.06
Calf adjusted 205-d weaning BW, kg/cow	264a	264a	255b	2.1	<0.02
Calf cumulative weaning BW, kg/cow	1157a	947ab	841b	84.5	0.04
Calf cumulative adjusted 205-d weaning BW, kg/cow	1401a	1156ab	1064b	97.4	0.03
Total produced calves, n/cow	5.4a	4.5b	4.2b	0.36	0.03
Weaned calves revenue, $/cow	4251a	3478ab	3091b	294.7	0.01

¹Period 1 = calved in the first 21 days, Period 2 = calved between day 22 and 43, Period 3 = calved day 44 or later.

²SEM, pooled standard error of means.

³Estimated postpartum interval from calving to conception based on consecutive calving dates and assuming a 282-d gestation length.

^abcMeans without a common superscript differ (P ≤ 0.05).