Effects of substitution of dietary protein with carbohydrate on lactation performance in the mink (Mustela vison)

Thirty mink dams nursing litters of 6 kits were assigned to one of 3 dietary treatments to investigate the effects of changing the protein:carbohydrates ratio on nutrient utilization, heat production, milk production and kit growth. Three diets were formulated to contain 65:3 (LC), 48:15 (MC) or 34:33 (HC) % of the metabolizable energy (ME) from protein and carbohydrate, respectively. The diets were fed ad libitum for 4 weeks from parturition. Twelve dams were held in an intensive care unit and subjected to balance and respiration experiments and the kits were injected with deuterium oxide to measure water kinetics and milk production. Eighteen dams were kept under normal farm conditions and feed intake of dams and weight gain of the kits were determined. Milk samples were collected from the dams. Metabolizable energy intake was not affected by dietary treatment. Carbohydrates were efficiently utilized with a digestibility coefficient of 84% in dams fed the HC diet. Dams fed the HC diet had a lower (P<0.05) percentage weight loss, lower (P<0.05) total heat production (HE), lower (P<0.05) protein oxidation (OXP), lower (P<0.05) water intake and a lower (P<0.05) nitrogen (N) excretion than dams fed the LC diet. Milk production, and thereby liveweights of the kits 4 weeks post partum, was higher (P<0.05) in dams fed the HC diet than in dams fed the LC diet. In conclusion, lactating mink dams are able to utilize digestible carbohydrates with positive effects on lactation performance and reduced nitrogen excretion.