If rabbit litters consistently die and a specific buck is the common denominator, it could indicate a genetic issue with that particular buck. Genetic factors can influence the health and viability of offspring, and if a buck carries certain genetic defects or weaknesses, it can result in higher rates of mortality in the litters.

In such cases, it is advisable to evaluate the buck's breeding history and assess whether there have been similar issues with other litters sired by him. If the pattern of high mortality persists across multiple litters, it may be best to discontinue using that buck for breeding to prevent further losses.

To ensure healthy litters, it's important to select breeding stock with good genetics, including robust health, strong reproductive traits, and no known genetic defects. Regular health screenings and genetic testing can help identify any potential issues before breeding. Additionally, maintaining optimal breeding conditions, providing proper nutrition, and practicing good husbandry techniques are essential for maximizing the chances of successful and healthy litters.