Sentence:  The already low proportion of Friesian and Hereford Friesian cross calves sold as <WSD>bobbies</WSD> declined to almost insignificant proportions and there was a very steep drop in the proportion of <WSD>bobby</WSD> calves in the other breeds 
Meaning of the word marked with <WSD> tags:  A calf that is slaughtered in its first month, usually because it has no dam or because it is undersized or otherwise defective.