A comparison of the production of F₁ and F₂ Border Leicester × Merino ewes

Abstract

A comparison has been made of the production characteristics of 255 F1 and 288 F2 Border Leicester x Merino ewes. These sheep comprised a total drop of ewes born in a breed establishment trial in March-April 1960. There were no significant differences between the means of each group of ewes for the following characters : 18 month body weight, mutton score, fleece and breech score, yield, staple length, crimps per inch, fibre diameter, follicle density, ratio of primary to total follicles, and wool colour and character. The F1 ewes had significantly heavier greasy and clean fleece weights and showed significant though only slightly greater face cover scores. There was no significant increase in the variation of any character studied, in the F2 ewes. It is considered that these results are reasonable when the nature of inheritance of production characters, and their susceptibility to environment are considered. On the other hand the variance of horn growth, which is controlled by a few major genes, increased considerably in the F2 ewes. There was a large (40 per cent) and significant drop in fertility in the F2 ewes brought about by a drop in the number of wet ewes and multiple births, and an increase in lamb losses. The significance of these findings in relation to crossbreeding and breed establishment is discussed.