Metabolic and growth response of mink (Neovison vison) kits until 10 weeks of age when exposed to different dietary protein provision

Abstract

Growth performance and metabolism were investigated in mink kits (n = 210) exposed to the same dietary treatment as their dams (n = 30), i.e. high (HP; 61% of metabolisable energy, ME), medium (MP; 48% of ME) or low (LP; 30% of ME) protein supply, from birth until 10 weeks of age. The kits were weighed weekly, and were measured by means of balance experiment and indirect calorimetry, in weeks eight and nine post-partum (p.p.). At weaning (seven weeks p.p.) and 10 weeks p.p. one kit per litter was killed and blood, liver and kidneys were collected. Plasma amino acid profiles, and hepatic abundance of mRNA for phosphoenolpyruvate carboxykinase (PEPCK), fructose 1,6-biphosphatase, pyruvate kinase and glucose-6-phosphatase (G-6-Pase) by q-PCR, were determined. There were no differences in live weights among kits the first four weeks of life when kits solely consumed milk, but male LP kits were the heaviest. After transition to solid feed MP kits weighed most at nine weeks of age (p < 0.05). At eight weeks of age, the kits fed the LP diet retained less (p < 0.05) N than HP and MP kits. Heat production did not differ among kits, although protein oxidation was higher (p < 0.001) in HP kits than in LP kits. Kits fed the LP diet had lower (p < 0.05) plasma concentrations of lysine, methionine and leucine than MP kits. Dietary treatment was not reflected in the relative abundance of any of the studied mRNAs, but kits had significantly lower abundance of all studied mRNA than their dams, ranging from 83% less PEPCK abundance to 40% less for G-6-Pase. The kidney mass was smallest (p < 0.01) in kits fed the LP diet, and liver masses were largest (p < 0.001) in HP kits. The results indicate that the LP diet did not meet the protein requirements for mink kits in the transition period from milk to solid feed. The capacity to regulate the rate of gluconeogenesis was even more limited in young mink kits than in adult dams. However, young mink kits can regulate protein oxidation in response to dietary protein supply, probably by adapting the size of the liver and kidneys to the level of protein supply.

Keywords:

• amino acids
• blood plasma
• enzyme activity
• gene expression
• mink
• offspring
• protein metabolism

Acknowledgements

This experiment was a part of the Committee on innovative post docs, Danish Research Agency project no. 2013-01-0027 “Reduced protein supply to lactating mink – animal performance and environmental aspects” to Rikke Fink, financially co-supported by The Danish Fur Breeders Research Centre. Financial support from the Danish Agricultural and Veterinary Research Council to project no. 23-04-0147 “Hepatic gluconeogenesis – approach for assessment, and in between species comparative aspects to Anne-Helene Tauson is gratefully acknowledged. The authors wish to thank Merethe Stubgaard for skilled technical assistance throughout the experiment, Abdalla Ali for performing the respiration experiments, and Hilmer Sørensen for performing the amino acid analyses in plasma.