Differences in laying
QWhy do some hens lay really well all the time and others keep taking time off? If they are kept in the same conditions and fed the same, should they not be more uniform?
VR SAYS: Hens are not machines and, although the hybrids have been selected for uniformity, there are still individuals who buck the trend. Simply, bird breeding hormones are activated by increasing light levels, so peak time of egg production is in the spring with lengthening days. That is why it is possible to keep hens laying in the winter by increasing their light levels to 14 hours a day. Spring lengthening days is well organised by Mother Nature as the baby birds or chicks then have high-protein insects to eat from the warmer days to maximise growth and survival rates. The number of chicken eggs in a clutch is the number of eggs laid on consecutive days. Each egg takes 25 hours from ovulation to laying, so laying is later each day. Ovulation of the next yolk occurs 30 minutes after laying, so a day is missed if ovulation occurs in the dark. The hybrid hens have been selected for a shorter ovulation time so clutch size is greater, i.e. there are fewer missed days. This intense production rate certainly shortens the life of hybrids. Quality of shell is inherited but also depends on quality of feed and lack of disease – infectious bronchitis produces wrinkly and weak shells, for instance, and stress (such as being chased, frightened or caught roughly) can produce distorted shells. At the beginning or end of a laying period aberrant eggs can be produced such as very small, very large or ones with no yolk. Pigment such as that Welsummer and Marans put on the shells gets lighter with the length of lay, so, if showing eggs, the early ones are more likely to have the darker and denser colour. (The exception to this is the blue egg laid by the Araucana and its crosses as the colour is laid down throughout the shell.) Double-yolked eggs are more likely to appear in the second year plus of lay and are caused by two ova (yolks) descending into the oviduct at the same time, the white and shell being added as normal but around a larger mass. As pure breeds get older, the shell quality of their eggs usually suffers and they lay fewer eggs each year. If you just want a few for incubation from a good line, then this is fine, but for economic production, flocks are changed on a regular basis. The stock cube and soup trade could not exist without spent hens. Ducks take 24 hours to produce an egg so they can be kept in their hut until about 9am when laying has taken place and you then can enjoy the eggs instead of the magpies or crows stealing them.