The variable responses in reproductive rate between flocks
The response in reproductive rate (foetuses/100 ewes joined) to nutrition varies for different flocks. The key factors affecting the responsiveness of flocks are their genetics and time of lambing. Later lambing flocks are more responsive.
It is critical to understand the responsiveness of your flock's reproductive rate (foetus/100 ewes joined) to increased ewe condition at joining so that you can make feeding decisions leading up to joining.
Whether your ewe flock is responsive (+30 lambs/condition score) or less responsive (+10 lambs/condition score) to improving condition score at joining, can affect the profitability of ewe management options approaching joining, depending on the value of extra lambs to your enterprise.
To determine the response of your flock requires condition scoring a flock at joining, recording the score of individual ewes and then recording their pregnancy status (dry, single bearing or twin bearing) at pregnancy scanning. Averaging the pregnancy status of ewes in each condition score at joining will show a relationship like the one below. Drawing a straight line (trend line) through the points will result in a sloped line. A steep slope indicates a very responsive flock to nutrition at joining. A shallow sloped line indicates a flock that isn’t responsive to nutrition at joining.
The difference between the reproductive rate at condition score 2 and condition score 3 (for example 0.35) means that you can expect an increase of 35 foetuses per 100 ewes scanned for every increase of one condition score.