In poultry, “pin bone distance” refers to the distance between the pelvic bones (pin bones) located near the hen’s vent. The pin bone distance is one of the key indicators of hen’s sexual maturity and the indication of when she will start laying eggs.

Pin Bones location, significance and interpretation

The pin bones are located on either side of the hen’s vent and the significance of the Pin bones’ distance indicates a hen’s approach to laying stage.

Closed pin bones or narrow space between the pin bones Indicate that the hen is not yet sexually mature or is not at the laying stage.

The distance of the two pin bones is wider apart indicates that the hen is sexually mature and likely to start laying eggs.

Pin Bone distance of a hen and the determination of laying stage

• The right distance of the ‘pin bones’ in commercial white leg horn breed of the breeder and commercial layer should be about 3 fingers wide. This will indicate that the hen is at the laying stage.
• Pin bone distance of between 2 and 2½ fingers indicates at about10 days prior to lay the first egg.

Variation in pin bone distance and the solution

If the variation in pin bone distance within a flock is above 70% it indicates the problems with flock’s uniformity in body weight, egg production, and egg size.

Body weight

Birds are less sexually mature than expected for age if the Pin bones are closer together. In this case we should check the birds’ body weight according to the age and can adjust the feed nutrition and qty in-take which will help the birds gradually return to the laying standards at the right age.

Light stimulation Adjustment

If the variation of ‘pin bone distance’ between the birds of the same age is more than 70% of the flock it’s better to adjust the light stimulation by increasing or decreasing based on the weather conditions to bring the ‘pin bones distance’ similar and correct it to 80 to 85% of the flock to have the uniformity in egg production & egg size.

This lighting adjustment will allow the flock to reach the same level of pin bone distance naturally.

Egg- grading techniques will help to improve uniformity of the flock.

Birds are more sexually mature than expected for age if the ‘pin bone distance’ is wider than expected for age; in this case we should monitor and adjust the feed nutrition & feed Qty. uptake to control the body weight gain to have an optimum egg production & egg size. Reducing or delaying the lighting would help to have the optimum egg size and production.

Herbal Extracts through feed

Adding any of the herbal extracts combination of product that claims to ‘balance the hen’s reproductive system’ would help to have the right pin bone distance and help the birds to bring to the laying stage. However, we should follow their recommended dosage as high dosage of inclusion will result in over-sized eggs.

Equipment in measuring Pin Bone distance

There is no equipment available for measuring the pin bones’ distance.

Physical measurement BY using one’s fingers is the only way to measure the pin bone distance.

The measurement ‘finger’ is relative to the operator’s hand size and so will vary from person to person; hence, ideally the same person should measure the pin bone distance periodically by every week. ‘Pin bone distance’ should be measured regularly from 15 to 16 weeks (105 to 112 days) of age until the last stage of laying period.

Summary

Routine measurement of pin bone distance helps determining the hen’s laying stage and will help to identify to resolve the issues with flock uniformity in body weight, egg production and egg size as well as the sexual maturity. Pin bone distance should ideally be measured every once a week to have uniformity. This exercise will certainly help to increase the farm average of egg production% especially by bringing non layers into laying stage in breeder and commercial layer flock.

Egg is a great protein source packed with energy, vitamins and minerals. Egg is a biotech and affordable solution to the food needs of the rising human population in the globe.

Hence, every egg ‘produced is every egg ‘served!

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