The hen's egg: Prediction and reduction of downgrading in large producer groups

British Egg Marketing Board data on the incidence of downgrading in eggs received at packing stations during the second week in each month from April 1960 to March 1968 have been analysed in relation to:

1. the incidence of free‐range, deep‐litter and battery husbandry in flocks from which they came, as estimated by interpolation from annual census data;

2. season, as represented by fundamental and first‐harmonic sine and cosine terms;

3. age‐structure of the flocks, as indicated by the incidence of extra‐small eggs 10 months earlier;

4. time;

5. packing‐station throughput.

It is shown that 93–3 per cent of the variance of downgrading percentage is associated with variation in (i), (ii) and (iii). After these effects had been taken into account there was no significant long‐term time‐trend but there were small effects associated with certain years. There was no significant effect of (v). The regression equation was used to predict the incidence of downgrading in the second week of each month from April 1968 to January 1969; this it did accurately except in May and June 1968, when the downgrading percentage fluctuated to an unprecedented degree following a very cold and a very hot spell of weather.

It is suggested that large producer‐packer groups should systematically collect information on the incidence of downgrading and the percentages of birds of each strain and age‐group, of cages of each type, of nutritional regimes and of egg‐collection methods; and that these data should be analysed to yield (a) forecasts of downgrading incidence and (b) estimates of the effect of each strain, cage‐type, etc. on downgrading incidence, for use when deciding replacement policy.