The selection of breeding animals should include screening for any faults or anomalies that are believed to be genetically transmissible. 4. ^{and 5.} All animals should also undergo a thorough assessment of temperament, structure, and health before being admitted into a breeding program. Conformation shows and various types of performance tests can be used by breeders to evaluate their animals and compare them to established breed standards. Once an adult dog or cat has been selected for breeding, a complete physical examination should be administered. This should include a fecal check for internal parasites, serological tests for brucellosis and herpesvirus in dogs, and the administration of any required vaccinations.

Before breeding, both the sire and the dam should be in excellent physical condition, well-exercised, and not overweight or underweight. It is especially important that the dam be at optimum weight and in prime condition. If the dam is underweight, she may be unable to consume enough food during gestation to provide for her own nutritional needs as well as the needs of her developing fetuses. Lack of proper nutrition in the dam can result in decreased birth weight and increased neonatal mortality. Conversely, an overweight condition in the dam can lead to the development of very large fetuses and dystocia.

At least 2 weeks prior to breeding the queen or bitch should be transitioned (if needed) to a high-quality, highly digestible food that is adequate for gestation and lactation. Changing to this diet early in the dam’s reproductive cycle allows her to be fully adjusted to the new food when breeding takes place and prevents the need to abruptly change diets during either gestation or lactation. Pet foods that have increased nutrient density are needed because of the increased nutrient and energy requirements of reproduction. Feeding a nutrient-dense food allows these needs to be met without excess food consumption, thus avoiding the likelihood of gastrointestinal upset or weight loss. The bitch or queen should be fed this food throughout pregnancy and lactation. For dogs, the food should contain animal-based protein as the primary protein source at a level of 28% to 30% (as fed). ⁶ Protein level for a reproducing queen should be slightly higher (~32%). ³ Energy density of the food should be relatively high; generally at least 20% fat (as fed) is recommended.

Both omega-6 and omega-3 fatty acids should be supplied in the diet, ideally balanced in a ratio between 5:1 and 10:1. This is important because a female’s essential fatty acid (EFA) status is negatively influenced by the physiological stress of pregnancy and lactation. ⁷ This risk is greatest in females who have had multiple litters. ⁸ This occurs because an increased supply of EFAs are needed during gestation and lactation to supply fetal tissues with fatty acids via the placenta and after birth through the milk. Of particular importance to reproducing females and their developing fetuses is the n-3 fatty acid docosahexaenoic acid (DHA). DHA is essential for normal neurological and retinal development in puppies and kittens (see Chapter 21, p. 211). ⁹ Because adult animals have a limited ability to synthesize DHA from alpha-linolenic acid, the best way to supply developing fetuses and neonates with DHA (and other essential long-chain polyunsaturated fatty acids) is through enrichment of the mother’s diet during pregnancy and lactation. ^{10. and 11.}

A final consideration is the level of antioxidants in the food. During gestation, females experience increased oxidative stress as a result of the increased oxygen consumption and altered metabolism that is associated with pregnancy. 12. ^{and 13.} Although limited studies have been conducted with companion animals, one study reported reduced antioxidant status in female dogs during gestation. ¹⁴ These changes, when considered in combination with recommendations to increase dietary EFAs during pregnancy, suggest that antioxidant nutrients such as vitamin E, vitamin A, and magnesium should also be increased in foods that are selected for pregnant bitches.