Comparison of Four Feeding Methods for Assessing the Relative Growth-Promoting Properties of Proteins

Abstract

Four methods of feeding rats have been compared in respect to their relative merits in detecting differences in the growth-promoting properties of casein and cowpea proteins. The methods were: (a) ad libitum feeding, (b) paired feeding, (c) constant protein feeding, and (d) adjusted protein feeding. The latter two methods have been described in detail. When gain in body weight in a 4-week feeding period was used as the criterion of response, it was found that greater differences in response to the two sources of protein were obtained by the ad libitum and the adjusted protein procedures than from the paired feeding and the constant protein methods. The former two methods also had the greater standard deviations. The methods ranked, in descending order of their sensitivities as measured by the ratio of the difference to the standard deviation of the difference: ad libitum, adjusted protein, constant protein and paired feeding. There was no advantage in using protein efficiencies in place of gain in body weight as the metameter.