Nutritive Properties of Protein in Different Cuts of Beef

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Abstract
The relative nutritive or growth-promoting values of the protein in 6 different cuts of beef from each of two carcasses, one of a Shorthorn steer graded “high good” and the other a Hereford cow graded “commercial,” were determined by feeding tests with young male albino rats. The following cuts of beef were tested: round, loin, rib, chuck, neck, and combined fore and hind shanks. When protein constituted 7.5% of the diets, there were no significant differences between the nutritive values of the protein in the different cuts from the Shorthorn steer. In tests with the cuts from the Hereford cow, the protein in the round had a higher value than that in the other cuts except the shanks. When protein constituted 10% of the diets, there were no significant differences between the nutritive values of the protein in the different cuts of beef, either from the Shorthorn steer or from the Hereford cow. When the diets contained 12.5% protein, the growth-promoting values of the protein in the rib and neck from the Shorthorn steer were slightly lower than the values for the shank, round or chuck. The protein in the rib from the Hereford cow had a slightly lower value than the protein in the chuck. The average growth-promoting value of the protein at each level of intake was slightly higher for all the cuts from the Shorthorn steer than for those from the Hereford cow, but the differences were not statistically significant. When diets containing 7.5% protein were supplemented with 0.25% cystine, there was a marked increase in the rate of growth and in the efficiency of utilization of the protein in each cut of beef from each animal. There were no significant differences between the nutritive values of the protein in the different cuts from the Shorthorn steer. The protein in the rib from the Hereford cow had a significantly higher value than that in any other cut, except the neck. The average nutritive value of the protein in the cuts of beef from the Shorthorn steer, at the 7.5% level of protein intake, was approximately the same as the value for dried skim milk. When the diets contained 10.0 or 12.5% protein, the beef protein was of higher nutritive value than the milk protein. The average nutritive value of the protein in the cuts from the Hereford cow was lower than the value for milk at the 7.5% protein level, the same at the 10% level, but higher at the 12.5% level. The admixture of gelatin with beef, in the proportions of 10, 15, or 20% of the total nitrogen in the diets, definitely lowered the nutritive value of the total protein when the diets contained 1.6% nitrogen.

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