Understanding Hen Mortality at Peak Production

Mortality can be due to disease but can also be a management problem. Poor flock management can cause high mortality leading into production or persistent mortality throughout the life of flock.

To determine mortality issues possibly related to management, begin by creating an accurate picture of the causes of mortality. Post-mortem examinations will provide much of the information. However, be careful when interpreting data from post-mortems. If data is collected from only a few hens, the results may be misleading as several different diagnoses within a small population will not provide an accurate conclusion. A good practice when troubleshooting higher than normal mortality for a flock or a complex is to conduct post-mortem examinations on all the daily mortality of affected flocks once a week. This practice will increase the sample size and give a good representation of the cause.

After collecting, it is recommended to group the data in broad categories. Examples include infection, prolapse, sudden death syndrome, runt, lameness, and no lesions. Each case should be put in the category that best describes the primary issue. The data can then be graphed giving the farm manager a broad perspective of mortality causes. Understanding the main cause of mortality is important to make targeted adjustments to a management program.

Photo stimulation

Preparation for photo stimulation

A common cause of hen mortality is inadequate preparation for photo stimulation. The pullets need to have the right weight, age, fleshing and fat reserve to respond well to photo stimulation and achieve a high peak of egg production with low mortality. Poorly conditioned pullets will fail to respond to photo stimulation and will have low peak production and increased mortality. When photo stimulated, poorly conditioned pullets may die due to prolapses, sudden death syndrome (SDS), or peritonitis issues and may have issues associated with overstimulation including a high number of double yolk eggs. Some poorly conditioned pullets do not mature properly and will become overweight producing few to no eggs. Overweight pullets are also more susceptible to mortality than hens at target weights.

Flock uniformity is an important part of preventing mortality. A flock with poor uniformity will have both immature and overweight pullets at photo stimulation. Both the poorly conditioned and the overweight pullets will have more issues after photo stimulation than pullets that are correctly conditioned.

A flock should be ready for photo stimulation between day 147 (week 21) and 154 (week 22) depending on the line. If the flock is not in the correct condition at the recommended time, it is possible to wait an additional week to give the first light increase, but it’s not advisable to wait longer than 1 week. The best way to determine if a flock is ready for photo stimulation is to evaluate fleshing scores and pelvic fat reserves. At photo stimulation, all females should have a fleshing score of 3 or higher. The majority (>90 %) of the pullets should also have enough pelvic fat reserves. Having enough, but not too much fat, is essential for the hormonal response to photo stimulation.

Photo stimulation program

Pullets are usually on an 8-hour light program in the pullet house. The goal is to increase to 14 hours as fast as possible. A good strategy is to increase from 8 to 12 hours for the first increase. After 2 weeks of 12 hours of light per day, increase the light length by 1 hour every week until the flock is receiving 14 hours each day. When light is increased too quickly, flocks show signs of overstimulation such as a high percentage of double yolks, peritonitis and prolapses.

Along with length, light intensity is also increased. The intensity is increased between 50 and 100 Lux (5 to 10 fc) on the first increase in day length.

Feed management