Best Prediction (BP) was developed by USDA-AGIL to predict 305-d lactational production for genetic evaluation in the US. Mean and SD of test days for all production traits are used by BP to predict either primiparous or multiparous 305-d production based on a Wood’s lactation curve. Fixed Holstein (HO) breed parameters for Wood’s curve (a, b, c, and SD of a, b, c) currently used by BP since 2009 were compared with alternative parameters that were newly estimated. The new parameters were implemented to determine if increased production of cows and reduced use of rBST over the past decade has impacted the effectiveness of BP to predict 305-d production of milk, fat, and protein. Test-day observations of HO cows from 7 high-production dairies in Minnesota that have participated in research with the University of Minnesota were used to estimate the alternative BP parameters. The primiparous cows calved from 2011 to 2016, and the multiparous cows calved from 2012 to 2016. All lactations of cows were required to have at least 250 d in milk and were also required to have at least 6 test days by 265 d in milk. Shapes of Wood’s lactation curves for these 3 production traits from BP were noticeably different for the currently used versus alternative fixed breed parameters. However, when the 305-d production records of cows were deviated within months of calving according to procedures used for genetic evaluation in the US, the differences between the 2 alternative predictions of 305-d production were of no practical consequence. Table 1 (Abstr. 468). Mean currently used and alternative Holstein parameters

	Currently used parameters				Alternative parameters
a	b	c		n	a	b	c
Primiparous					1922
Milk	13.010	0.267	0.00262			13.376	0.300	0.00238
Fat	0.784	0.120	0.00130			0.762	0.172	0.00125
Protein	0.463	0.203	0.00161			0.462	0.247	0.00158
Multiparous					1730
Milk	22.009	0.216	0.00357			21.391	0.278	0.00370
Fat	1.287	0.073	0.00213			1.173	0.139	0.00228
Protein	0.854	0.132	0.00232			0.801	0.197	0.00257