PS7-12. Fats and Growing Cats: The Effects of Dietary n-6:n-3 Fatty Acid Ratios on Queen Metabolism and Physiology During Gestation and Lactation.

Abstract Gestation and lactation are physiologically demanding life stages that influence metabolic activity and energy partitioning in mammals, supported by dietary fatty acids (FA). There are no published recommendations for dietary n-6:n-3 ratio and little information on the contribution of n-6 linoleic acid (LA) and n-3 alpha-linolenic acid (ALA) to physiological outcomes. This study aimed to assess whether dietary n-6:n-3 ratios, altered by LA:ALA, impact queen body weight (QBW), feed intake (FI), respiratory quotient (RQ), total energy expenditure (TEE), and total litter body weight (KBW) during gestation and lactation in queens. Four unproven adult queens and one tom were bred for two parities. Queens received one of two diets consisting of the same kibble base with n-6:n-3 ratios of either 7:1 or 3:1, achieved through top-dressing with plant-based oils (sunflower and flaxseed) to alter the LA:ALA ratio, with otherwise identical macro- and micronutrient content. Indirect calorimetry was performed weekly from 2 weeks pre-partum to 4 weeks post-partum, BW weekly, FI daily, and KBW daily post-partum. Repeated measures of BW, FI, RQ, TEE, and KBW across week were analyzed using the GLIMMIX procedure of SAS Studio® (v.9.4). Gestational QBW was not affected by diet; however, queens fed 7:1 were heavier during lactation than queens fed 3:1 (p = 0.001). There were no main effects of diet on FI, RQ, TEE, or KBW in any physiological stage (p > 0.05). Gestational QBW increased by week (p < 0.001), with no effect of week during lactation. There was no week effect on gestation FI; however, FI increased weekly during lactation (p < 0.01). Gestational RQ tended to decrease by week (p = 0.08), with no week effect on RQ during lactation or on TEE during gestation or lactation. During lactation, KBW increased daily (p < 0.001). The interaction between diet and week affected RQ during gestation (p = 0.02), with a larger decrease in RQ observed in queens fed 3:1 compared to 7:1 approaching parturition. Our findings suggest that dietary n-6:n-3 ratio, modified through LA:ALA, may influence the physiology and metabolism of queens during gestation and lactation. The greater QBW observed in queens fed the 7:1 diet despite similar FI and KBW to the 3:1 diet may suggest differences in nutrient partitioning and utilization during lactation. All queens demonstrated expected patterns of weight gain and loss across gestation and lactation, suggesting both ratios supported normal, healthy fetal development and subsequent milk production for neonates. To our knowledge, this is the first study to use indirect calorimetry in gestating and lactating queens to assess macronutrient utilization and TEE.