Table 1.

Effects of rbST use on resource input and waste output (per unit of milk) over the lactation cycle of an average cow

	Resource input or waste output per kilogram of milk*	Change per unit of milk with rbST use†, %
Resource inputs
Net energy for maintenance, MJ	1.73	−11.8
Metabolizable protein for maintenance, g	30.4	−7.5
Total net energy requirement‡, MJ	4.79	−4.5
Total metabolizable protein requirement‡, g	77.6	−3.2
Feedstuffs per kg dry matter	0.82	−8.1
Waste outputs
Methane, g	26.2	−7.3
Manure, kilogram freshweight	1.92	−6.8
N excretion, g	5.67	−9.1
P excretion, g	2.98	−11.8

*Based on the average annual milk yield (28.9 kg/d) for 2006.

^†Use of rbST significantly increases milk production (7); yield response to supplementation equaled 4.5 kg per day.

^‡Comprises nutrients required for maintenance plus lactation.