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Body Composition in the Growing Rat as Affected by Dietary Lactose, Calcium, Buffering Capacity and Edta^{1, 2,}

Rutgers University, New Brunswick, New Jersey 08903

Abstract

The effects of adding alpha-lactose (0.0 and 12%), calicum (0.19, 0.48 and 0.78%), dietary buffering capacities (BC) (0.46, 0.54 and and 0.76) and EDTA (0.0 and 0.2%) to the diet of growing male rats on body composition were tested in a balanced factorial arrangement (2 x 3 x 3 x 2). A total of 144 Norway growing male rats was employed in the study providing four replicates for each of 36 dietary treatments. The rats were killed at the end of the 6-week experimental period, and the unskinned body, less the contents of the digestive tract (wet carcass), was analysed for water, fat, protein and ash. Lactose feeding resulted in a decrease (P<.01) in percentage of body fat and increases (P<.01) in percentages of body water, protein and ash. Lactose interacted (P<.01) with dietary BC and EDTA on total weight of wet carcass and percentages of body water, fat and protein. Relative skeletal size and body water percent on a lean body mass basis were increased by feeding lactose. Lactose-fed rats maintained a relatively younger body composition with more body water, protein and ash and less fat. The effect of feeding lactose on body composition depended on the diet composition with percentages of body water and fat being mainly affected. Lactose effect on body protein and ash, however, was related to improved calcium retention in lactose-fed rats. The main effect of calcium intake was exhibited on body protein and ash and to a lesser extent on body water and fat. Increased calcium intake increased body protein and ash (P<.01) and decreased body water and fat (P<.05 and P<.01, respectively). The relative size of the skeleton and protein percent on a lean body basis were increased with increased calcium intake. The quadratic responses in feed intake and weight of wet carcass (P<.05 and P<.01, respectively) by increasing calcium level to 0.78% resulted in decreases in total body water, fat and protein in grams and in body fat percent.

The data indicated that percent body water and fat can be changed independently of percent body protein and ash by dietary manipulation, i.e. body water and fat are influenced by lactose and body protein and ash are influenced by level of dietary calcium (table 7).

¹ Paper of the Journal Series, New Jersey Agricultural Experiment Station, Rutgers University.

² Department of Animal Sciences.