Modelling of sulphur amino acid requirements and nitrogen endogenous losses in kittens

ABSTRACT

The objective of this study was to estimate the sulphur amino acid (methionine + cystine) requirements and nitrogen endogenous losses in kittens aged 150 to 240 d. Thirty-six cats were distributed in six treatments (six cats per treatment) consisting of different concentrations of methionine + cystine (M + C): T1, 6.5 g/kg; T2, 8.8 g/kg; T3, 11.3 g/kg; T4, 13.6 g/kg; T5, 16.0 g/kg; and control, 6.5 g/kg. Diets were formulated by serial dilution of T5 (a diet relatively deficient in M + C but containing high protein concentrations) with a minimal nitrogen diet (MND). Thus, crude protein and amino acid concentrations in diets T1–T5 decreased by the same factor. The control diet was the T1 diet supplemented with adequate concentrations of M + C (6.5 g/kg; 8.8 g/kg; 11.3 g/kg; 13.6 g/kg and 16.0 g/kg). All diets were based on ingredients commonly used in extruded cat diets. Digestibility assays were performed for the determination of nitrogen balance. Nitrogen intake (NI) and nitrogen excretion (NEX) results data were fitted with an exponential equation to estimate nitrogen maintenance requirement (NMR), theoretical maximum for daily nitrogen retention (NR_maxT), and protein quality (b). M + C requirements were calculated from the limiting amino acid intake (LAAI) equation assuming a nitrogen retention of 45 to 65% NR_maxT. The NMR of kittens aged 150, 195, and 240 d was estimated at 595, 559, and 455 mg/kg body weight (BW)^0.67 per day, respectively, and M + C requirements were estimated at 517, 664, and 301 mg/kg BW^0.67 per day, respectively.

KEYWORDS:

• cats
• cystine
• Göttingen method
• kittens
• methionine
• nitrogen balance
• requirements

Acknowledgments

The authors are grateful for the financial support provided by the Brazilian National Council for Scientific and Technological Development (CNPq) and the Brazilian Federal Agency for Support and Evaluation of Graduate Education (Capes). The authors also thank Ajinomoto Ltd., Manfrim Industrial e Comercial, Cargill Incorporated, and Auster Nutrição Animal for carrying out the amino acid analysis, processing the diets, and donating diet ingredients.

Disclosure statement

The authors declare no conflicts of interest.

Declaration of authors’ agreement to authorship and submission

All authors agree to authorship and submission of the manuscript for peer review.

Study design

All authors contributed to study design and data interpretation. JS, ACC, and RSV contributed to study conception and design. JS, MEZM, ATU, MPS, and MB performed the experiments. JS, JCPD, ACC, and RSV analyzed the data, carried out the statistical analysis, and drafted the manuscript. LBR, ACC, and RSV critically revised the manuscript. All authors read and approved the final version of the manuscript. JS ([email protected]) and RSV ([email protected]) take responsibility for the integrity of the work as a whole, from inception to published article.

Additional information

Funding

This research was funded by CNPq (process number 446567/2014-0); The authors JS, LBR and MEZM scholarship were supported by CAPES.