The teat number in rabbits: The possibility and benefits of selection for this trait

• Rabbits (both sexes) most often have 8, 9 or 10 teats, fewer or more teats are rare. • The teats can be counted on a newborn rabbit. • Rabbits does with more teats raise more kits. • The teat number is a well-heritable trait, and can be successfully selected for. • The teat number should be taken into account during the selection of maternal lines. The purpose of the review is to present the distribution of teat number in rabbits, its relationship with some reproductive traits, and the possibility and limitations of selection for increasing teat number. In many mammal species, it has been observed that the number of offspring born is typically half as many or at most equal to the number of teats ("one-half rule"). While this rule holds true for European wild rabbits, it is no longer applicable for domesticated rabbits. Teat numbers most commonly range from 8 to 10, while litter size of hybrid rabbits typically fall between 10 and 12. A weak correlation was found between teat number and litter size at birth, but a closer relationship was observed between teat number and the survival of suckling kits or litter size at 3 weeks, especially in litters larger than 10. The high heritability of teat number was confirmed by the distribution of the teat number of the offspring from parents with 8 or 10 teats. Selection experiments have shown that it is possible to increase the average number of teats and the proportion of rabbits with 10 teats, although rabbits with 11 or 12 teats are rarely born. When selecting maternal lines, the number of teats should be considered to increase litter size. In the short term, selecting does with 10 teats is beneficial as it increases the chances of survival for kits during nursing, as they have more opportunities to access milk. In the long-term, this selective breeding strategy can lead to improved survival rates and overall reproductive success in rabbit populations.