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Infertility in breeder flocks has become a common concern in broiler breeder production.
The causes of reproductive failure are multiple.
Infertility could be related to females, but males have a more significant impact.
Male fertility is a combination of proper spermatogenesis related to a healthy reproductive tract and mating behavior mainly linked to plasma testosterone levels. Both aspects have a high correlation with testicular size or weight.
In Figure 1, we have a broiler breeder rooster’s normal healthy reproductive tract. The semen filling the ductus deferens indicates this rooster is in production.
Figure 1. Normal reproductive tract.
Excessive body weight gain as roosters age or poor conformation can also cause incomplete copulations in roosters and eventually a reduction in fertility. On the other hand, roosters with low body weight (< 3,800 grams) have been also associated with low fertility.
Figure 2. Unilateral orchitis caused by E. coli. The left testis of a 27-week-old rooster is swollen and discolored.
Male infertility increases as roosters age after 40 weeks but can be accelerated due to the following factors:
Suboptimal development during rearing. Low body weights early in life cause weaker birds in the flock and lower placement in the pecking order. This causes stress, high blood corticosterone, reduced testosterone levels, delayed testicular development, and potentially faster testicular regression as roosters age.
Extended exposure to constant photoperiods longer than 12 hours during rearing.
Increase in photoperiod to more than 12 hours after 40 weeks of age.
Marginal nutritional deficiencies during the rearing and mating phases.
High crude protein and high calcium diets fed for a long time with levels similar to the ones observed in female diets can decrease sperm concentration in roosters older than 55 weeks.
Diseases caused by infectious bronchitis virus (IBV), avian metapneumovirus (aMPV), avian influenza (AI), Mycoplasma gallisepticum and Mycoplasma synoviae (MG/MS), and bacteria like Escherichia coli (Figure 2), or Staphylococcus aureus(Figure 3).
Figure 3. Orchitis caused by Staphylococcus aureus. Inflammation is evident in the swollen, discolored testis. Orchitis typically destroys the complete testis.
RESPIRATORY VIRUSES AND MALE INFERTILITY
Many respiratory viruses may also induce urogenital infe...
