The Determination of the Net Utilization of Proteins by a Shortened Method

Abstract

The various methods of measuring the nutritive value of proteins have been frequently reviewed (Chick, 1942;Mitchell, 1944;Allison, 1949 A method is described here, whereby seven proteins can be tested simultaneously in 10 days, using thirty-two rats and involving no N estimations other than on the food. The method is based on the formula already discussed (Bender & Miller, 1953 a). In principle the values obtained are the same as those obtained by the Thomas-Mitchell procedure, being a measure of that proportion of the food N eaten retained by the test animals. EXPERIMENTALAnimals. Rats of our hooded strain were used in all the experiments. T h e animals were weaned at 21 days at a weight of about 35 g, and fed for I week on stock diet so that they weighed 50-60 g at the beginning of the experiment.Chemical analyses. Body water was determined after killing the rats with chloroform. Incisions were made into the skull, thoracic and body cavities, and the carcasses were dried to a constant weight at 105' (48 h). Intestinal contents were included. N was determined by the Kjeldahl method. Small rats, of less than 15 g dry weight,were completely digested with 10 ml. conc. H,SO,/g dry matter and 20 g catalyst (2 g SeO,, 2 g CuSO,. 5H,O, 16 g K,SO,). T h e dried carcasses of the larger rats were pounded in a mortar and 10-15 g portions digested. The large size of the portions compensated for any lack of homogeneity as shown by the agreement between duplicate digestions. Samples of this size, especially those rich in fat, frequently froth violently during digestion, but this frothing was avoided by maintaining the digestion mixture at 120' for 2 h before strong heating. T h e digested material was finally diluted for the micro-estimation of ammonia (Markham, 1942

Spirulina as a protein source in the nutritional recovery of Wistar rats

“…The formulation of the C diet, despite the recommendation of eating 20% of protein for growing rodents, was calculated to provide 12% of this nutrient (Miller and Bender 1955;Sgarbieri 1996;Jood and Singh 2001). It is noteworthy that in order to obtain the C diet with 12% of protein, it was supplemented with 120 g casein, since it was not pure (> 85% protein); the rest of the ingredients were as recommended by Reeves et al (1993) and corn starch to supplement 1000 g of diet.…”

Improvement of Tilapia (Oreochromis niloticus Linnaeus, 1758) Growth Performance Fed Three Commercial Feed Additives in Diets

“…All fish were weighed and counted fortnightly and feeding rates were adjusted accordingly. At the end of the experimental period the following growth and feed utilization indices were calculated: weight gain (WG), specific growth rate (SGR), food conversion ratio (FCR) and protein efficiency ratio (PER) using the following formulae as described by Brown [12], Winberg [13], Castell and Teiws [14] and Miller and Bender [15], respectively.…”

Potential of crab meal as a protein substitute for fish meal in diets for mudfish Heterobranchus longifilis juveniles

“…Fish performance was evaluated by calculating the following parameters: weight gain (g) = final weight (g) -initial weight (g), length increase = final length (mm) -initial length (mm) of fish, percent survival = N¡ x 100/ N O (Alatise and Otubusin, 2006), where N¡ = number of fish alive at end of experiment and N O = number of fish at the start, specific growth rate (%day -1 ) = ln W 2 -ln W 1 x 100/ t 2 -t 1 (Brown, 1957), W 2 and W 1 are final and initial weights (g),t 2 and t 1 = end of growth period and start of growth in days and ln is natural logarithm, condition factor = 100 (Weight, g)/(total length, cm) 3 , Bagenal and Tesch (1978), feed conversion ratio (FCR) = feed intake (g) / weight gain (g) (Utne, 1979), protein efficiency ratio (PER) = weight gain (g) / weight of protein fed (g) (Zeitoun et al, 1973) and apparent net protein utilization (ANPU) = P b -P a x 100/P i (Miller and Bender, 1955) where P b and P a = body protein at end and start of feeding trial and P ¡ = protein consumed over feeding trial.…”