What are the signs of a dog being in heat but not producing viable sperm?

The question seems to contain a slight misunderstanding, as dogs in heat are female, and the production of viable sperm is a male reproductive function. However, I will address the signs of a female dog being in heat and clarify the reproductive processes of both male and female dogs to provide a comprehensive answer.

1. Signs of a Female Dog in Heat
A female dog in heat, also known as estrus, exhibits several physical and behavioral changes due to hormonal fluctuations. These signs typically occur in cycles, usually every six to twelve months, depending on the breed and individual dog. The estrus cycle consists of four stages: proestrus, estrus, diestrus, and anestrus. The most noticeable signs occur during proestrus and estrus.

During proestrus, which lasts about 7-10 days, the female dog's body prepares for potential mating. Signs include:
- Swelling of the vulva
- Blood-tinged vaginal discharge
- Increased urination frequency
- Attracting male dogs but not yet being receptive to mating

During estrus, which lasts about 5-9 days, the female becomes receptive to mating. Signs include:
- A change in vaginal discharge from bloody to straw-colored or clear
- Flirtatious behavior, such as flagging her tail to the side when approached by a male
- Increased restlessness or clinginess
- Attempting to escape to find a mate

2. Male Dog Reproductive Function
Male dogs do not go into heat. Instead, they are capable of producing viable sperm year-round once they reach sexual maturity, typically around 6-12 months of age. Sperm production occurs in the testes and is influenced by hormones like testosterone. If a male dog is not producing viable sperm, it may be due to factors such as:
- Age (very young or very old dogs may have reduced fertility)
- Health issues (e.g., infections, hormonal imbalances, or testicular abnormalities)
- Genetic conditions
- Environmental factors (e.g., exposure to toxins or extreme stress)

3. Practical Tips and Recommendations
For female dogs in heat:
- Keep her indoors or closely supervised to prevent unwanted mating.
- Use doggy diapers or sanitary pads to manage discharge.
- Avoid dog parks or areas with intact male dogs.
- Consider spaying if breeding is not intended, as this prevents heat cycles and reduces the risk of certain health issues.

For male dogs:
- Monitor for signs of reproductive health issues, such as swelling, pain, or changes in behavior.
- Consult a veterinarian if you suspect infertility or other reproductive problems.
- Neutering is an option to prevent unwanted behaviors and reduce the risk of certain health problems.

4. Potential Risks or Concerns
For female dogs, the heat cycle can lead to:
- Unwanted pregnancies if not properly managed
- Increased risk of mammary tumors or pyometra (a life-threatening uterine infection) if not spayed

For male dogs, infertility or low sperm quality can result from:
- Infections or injuries to the reproductive organs
- Genetic or congenital issues
- Poor nutrition or environmental stressors

5. Additional Related Information
Understanding the reproductive cycles of dogs is essential for responsible pet ownership. Spaying and neutering are common procedures that not only prevent unwanted litters but also offer health benefits. For example, spaying a female dog before her first heat cycle significantly reduces the risk of mammary tumors and eliminates the risk of pyometra. Neutering male dogs can reduce aggression, roaming, and marking behaviors.

6. When to Seek Professional Help
Consult a veterinarian if:
- Your female dog shows signs of prolonged or abnormal heat cycles (e.g., excessive bleeding, lethargy, or pain).
- Your male dog exhibits signs of reproductive health issues, such as swelling, discharge, or difficulty urinating.
- You are considering breeding and want to assess the fertility of your dog.

In summary, female dogs in heat exhibit specific signs related to their reproductive cycle, while male dogs produce sperm year-round and do not experience heat cycles. Understanding these differences and taking appropriate measures can help ensure the health and well-being of your dog.