Amino acid requirements of guinea pigs using chemically defined diets

Abstract

At the University of Missouri in Columbia we have been studying the nutritional requirements of the guinea pig using chemically defined diets. The purpose of this longterm study has been to enhance the value of this species as an animal model for human research. This presentation includes the results of over twenty experiments, 22 days in duration and involving over 1500 guinea pigs from 3–6 weeks of age.

In 1982 we published the results of our first studies on indispensable amino acid nitrogen and total nitrogen requirements. The amino acid content and composition of these diets was patterned after casein and soy protein based diets reported in the literature. Four levels of total dietary nitrogen (2.5, 2.9, 3.6 and 4.3%) and three levels of indispensable amino acid nitrogen (1.7, 2.0 and 2.4%) were tested. The level selected was 3.6% total dietary nitrogen and 1.7% total indispensable amino acid nitrogen. The remainder of our research on specific amino acid requirements has been conducted using 3.6% of total dietary nitrogen. When individual indispensable amino levels have been altered they have been replaced by a corresponding change in the dispensable amino acid nitrogen component. The total dietary level of indispensable amino acid nitrogen has been reduced from 1.7% to 0.98% while maintaining the total dietary nitrogen level constant at 3.6%. During the process of this research the growth rate of the animals has increased by over 20%, attesting to a better balance of nutrients. Our most recent research suggests that total dietary nitrogen can be reduced by 20% to about 2.9%.

The nutritive requirements of the guinea pig are not well documented. The research reported here is focused on designing a chemically defined diet for guinea pigs 2–6 weeks of age which will make this animal a more useful model for human research. These studies deal with the assessment of the indispensable amino acid (IAA) and the total nitrogen (TN) requirements of the growing guinea pig [1–3]. The requirements for Arg, Lys, Met and Trp have been previously estimated using diets supplemented with crystalline amino acids and based on either casein or soybean protein [4–7].