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Some Factors Encountered in Experiments to Evaluate Feeds for Fattening Lambs

Oklahoma Agricultural Experiment Station

Abstract

Thirty-six lots of twenty lambs each were fed during a six-year period by a controlled gain method. An attempt was made to establish the relative net energy value of cottonseed meal, barley, oaks, and prairie hay for fattening lambs, using corn and aldalfa hay as base feeds.

In the first series of experiments, covering a three-year period, cottonseed meal fed in excess of the amount needed to balance the ration had an average value of 64.4 therms per hundred pounds in producing live weight gain on lambs, based on an assigned value of 79.2 therms for corn. In one of three experiments, .1 pound of cottonseed meal added to a ration of corn and alfalfa had considerable supplementing value. The net energy values of prairie hay varied widely, but averaged 33.8 therms, based on the value of 41.5 therms assigned alfalfa hay.

A second series of experiments, conducted in three successive years, found oats to have an average value of 72.8 therms when they replaced all the corn in a ration or 80.1 therms when one-half the corn was replaced. These values are based on live weight gains and do not consider the less finished carcasses of the oat-fed lambs. In a similar comparison barley had an average value of 70.3 therms in replacing all the corn or 64.5 therms in replacing one-half the corn. Carcasses of lambs fed corn and barley carried as much carcass finish as corn-fed lambs, but barley alone did not produce comparable finish. The value for barley was slightly higher when fed in combination with corn than when fed with oats.

Results of these experiments suggest that comparable live weight gains commonly do not result in similar carcass condition of experimental lambs. Other factors encountered in controlling gains of lambs that may have biased the values obtained are weather, fill, feed quality, palatability, rate of gain, base values of feeds, feed combinations, and the inability of the experimenter to always keep lots gaining at or near the same rate.

The described method of evaluating feeds does reduce the number of variables common to ordinary feeding experiments because gains are controlled as is the intake of all feeds except those under comparison. The live weight gain producing value of a feed can be expressed readily in terms of a standard or base feed with which it was compared.

¹ A portion of the material contained was submitted to the Graduate School of Cornell University, Ithaca, New York, September, 1938, in partial fulfillment for the degree, Doctor of Philosophy. The author wishes to acknowledge the assistance of Professor F. B. Morrison, Head of the Animal Husbandry Department, Cornell University, in designing this series of trials.