Male fertility is clearly associated with rearing a uniform flock that has adhered to weight and conformation standards. However, other factors influence flock fertility performance. Incorrect transfer from rearing to the production house can have an adverse effect on male fertility. There are things to consider at transfer that can keep a well-managed male on track.

Timing Is Everything

It is important that the growth and uniformity established in the rearing house is continued in the production house. Male transfer typically coincides with photostimulation. Therefore, males will mature during the 4 weeks after transfer and experience 75% of testis development. Growth disruption during this time will have a negative impact on testis development and sperm maturation.

Training males to their feeding system is key to successful separate sex feeding programs. Males need to identify their specific feeders at transfer. Ideally, use the same feeding system in the production house that was used in rearing. Often, this is not the case and the timing of transfer should be adjusted to allow the pullets and males the opportunity to find their respective feeders as soon as possible after transfer.  It may be necessary to transfer males and females at different times (2 to 5 days) to allow the birds time to adjust to a new feeding system (Table 1).        


Recommended transfer timing of breeder broilers to production house based on feeding system. (Cobb-Vantress)

Sexual Synchronization

Correct sexual synchronization will lead to high hen receptivity and mating efficiency. Incorrect synchrony may reduce flock fertility due to male overactivity, which results in mortality, slating, overmatingb and interference during mating. Factors influencing male/female synchronization include bodyweight and composition, frame size, and stage of maturity at transfer. Be aware that different male lines will differ regarding rates of maturation, behavior, temperament, and degree of interaction/receptivity with females. In general, it is recommended that the weight difference between males and females range from 15% to 25% depending on the Cobb package. Sex separate feeding will allow the weight differential between males and females to be reduced to 8% to 15% when flock sexual activity peaks around 30 weeks (Table 2).


Percentage of bodyweight difference between females and males at transfer and through production. (Cobb-Vantress)

Prior to mixing the males and females, evaluate both sexes to determine the degree of synchrony. In some cases, males that are closest to average weight (11% to 12% heavier than females with a fleshing score of 2.5 to 3) can be transferred. This would be the best-case scenario and will reduce mortality due to leg health. Mating will be easy and maintain feather coverage on the hens’ backs.


If the male maturation is ahead of the females, consider the following to slow sexual development:

  • Reduce light to 1 to 2 lux (0.1-to-0.2-foot candle) in rearing. 
  • House males one week after females to allow the female one additional week to mature.  
  • If the males are more sexually advanced or if the male weight exceeds the female weight by 30%, introduce a lower male ratio at mixing (6% to 7% for slatted and 7% to 8% for non-slatted house).
  • At peak production or first spike, increase the male ratio to 8% to 9.5%.

If the maturation of the male flock is behind the female, consider the following:

  • Increase the weekly bodyweight gain for males between 18 and 21 weeks.  
  • Transfer and photostimulate males up to 1 week earlier than the females. This can be done in the rearing house if the males have their own house.                      

Maintaining Uniformity After Transfer

At transfer, it is important to monitor the transition by observing the males’ eating behavior. Comb size may be a factor as some males will be able to access female feeders despite the use of male exclusion systems. As the males mature and the comb develops (24 to 25 weeks), they will not be able to access female feeders. It is important to determine the percentage of males eating feed from the female feeders because male and female daily feed adjustments must be made. Males that eat from the female feeders will overconsume, while the females are shorted on feed. To compensate for this, add a percentage of female feed to the female feeders that is consistent with the percentage of males consuming female feed.  Subtract the same amount of feed from the male feeders. Closely track the feed amounts as the percentages will change until comb development is complete. By 25 weeks, resume 100% feed allocations for males and females.  


Jim Jones (Cobb-Vantress)

The key to maximizing fertility is to provide a uniform environment. Presentation feeding reduces competition at the feeder by providing all birds the opportunity to eat at the same time. Provide the appropriate number of male feeders: 8 to 10 birds for round and 10 to 12 males per oval pan. If using a track system, provide 20 centimeters (8 inches) per bird. Confirm that all pans are adjusted to provide the maximum depth of feed across all pans. Pan settings should be identical throughout the house to ensure even feed cleanup. Stabilize all feeding systems so feeders do not swing while males are feeding. Weigh male feed daily and fully discharge all feed across the system. Lowering the male feeding system as the females leave the floor to eat will allow timid males to eat. Keep the male feeder at a height that excludes the females and makes the males stretch slightly to eat.

The transfer from the rearing house to production house can be a stressful transition. Everything in the production house should be ready before transfer. Males should never lose weight in the production house. A loss in bodyweight of 100 grams or more may cause a reduction in sperm quality if the breeder condition is below standard. Top flocks tend to have better weight control and never exceed the weight target by more than 2% to 5 %. Flesh males frequently in production to ensure they do not lose condition.  If possible, use males with weights closest to the female weight. Follow feed increases as specified by appropriate Cobb product supplement (