Table 1. Milk production over the lactation during which the cows were sampled.

Cow	Age in years	Lactation length (days)	Annual milk (kg)	Milk protein (kg)	Milk fat (kg)
B	5.7	271	5156	179.6	228.7
C	4.7	289	4758	195.3	237.8
D	4.7	297	5975	207.0	245.0
E	5.8	266	5829	203.3	261.6