The objective was to determine relationships between protein and energy consumed from milk replacer and starter for heifer growth and first lactation performance of Holstein cattle. Data were collected from 4,534 Holstein animals from birth year of 2004 through 2014 to analyze growth of calves, and 3,627 cows were analyzed for production during first lactation. Calves were received from 3 commercial dairy farms and assigned to 45 trials at the University of Minnesota Southern Research and Outreach Center. Milk replacer (MR) metabolizable energy (ME), starter ME, MR protein intake, and starter protein intake consumed from 0 to 8 wk were (mean ± SD): 102.7 ± 13.3 Mcal/kg, 151.9 ± 41.4 Mcal/kg, 4.8 ± 1.0 kg, and 9.5 ± 2.6 kg, respectively. Birth season, year, 6- and 8-wk ADG class, and herd were included in the model with calf trial as a random effect. Calves born in the fall and winter consumed more ME (P < 0.001) and protein (P < 0.001) from MR and starter than calves born in the spring and summer. Increased protein and ME consumption led to greater growth (P < 0.05) and first lactation production (P < 0.02). Variation was high in all estimates suggesting numerous factors contribute to growth and milk production. Table 1. Effect of birth season on 8-wk MR and starter protein (kg) and ME (Mcal/kg; n = 3,627)

Variable	Spring	Summer	Fall	Winter	Season P-value
MR protein intake	4.7ab	4.7a	4.6b	4.7a	0.057
Starter protein intake	9.0b	9.1b	10.2a	10.2a	<0.001
MR ME intake	101.8a	101.5a	100.1b	102.9a	0.025
Starter ME intake	143.6b	145.0b	162.9a	162.8a	<0.001
Combined protein intake	13.7b	13.9b	14.8a	14.9a	<0.001
Combined ME intake	245.9b	246.8b	262.9a	265.8a	<0.001