Many chemical analyses have been made of a number of different members of the cactus family to determine their value as a feeding stuff for animals.? With this data we are enabled to judge with a fair degree of accuracy the amount of the various nutrients contained by many different species of this group of plants, as well as by different parts of the same plant. However, as no record of digestion experiments with any of the cacti has been found, it was impossible to say what proportion of the different nutrients were available to the animals. The increased use of the prickly pear (the flat-jointed members of the genus Opuntia) as a feed for all classes of ruminants, especially for range and dairy cattle, makes it Important for the proper preparation of a ration that the feeder know how much digestible nutrients to expect from feeding a given quantity of the plant either alone or mixed with other feeding stuffs. The following experiments have therefore been conducted to determine the digestibility of prickly pear and thus guide the feeder in the preparation of rations from this plant.
- The average digestibility of the nutrients of prickly pear as determined in the first experiment where Opuntia lindheimeri was used were: Dry matter, 65.86 per cent; ash, 33.68 per cent; protein, 57.47 per cent; fat, 68.38 per cent; crude fiber, 41.32 per cent; nitrogen-free extract, 81.78 per cent. In the second experiment where the variety O. læris? was used the coefficients of digestion were: Dry matter, 63.96 per cent; ash, 35.81 per cent; protein, 40.87 per cent; fat, 69.02 per cent; crude fiber, 53.99 per cent; nitrogen-free extract, 78.95 per cent. In general these results would perhaps show a somewhat low coefficient for protein, a decidedly low coefficient for ash, but a very high coeficiente for the nitrogen-free extract. The total digestible nutrients are about equal to those of immature green corn fodder.
- Our experiments seem to show that when prickly pear is fed with cured fodders or grams the digestibility of both is increased. For this reason prickly pear has a greater food value than is shown by its analysts and digestion coefficients.
- The nutritive ratio, 1. e., the ratio of proteins te carbohydrates, is very wide for this feed, and m feeding it to all classes of animals, for whatever purpose, much better results should be obtained when it is fed with some substance of a high protein content.
- While the digestibility of the ash was apparently small, as noted above, yet the large amount of ash contained in these plants caused more ash to be assimilated from a ration equivalent to 15 pounds of dry matter than is ordinarily assimilated from an equal ration of alfalfa, which has a higher coefficient of digestion for its ash.
- The steers seldom drank water when fed prickly pear alone. In fact, in feeding a ration of 100 pounds of this feed per day the animals obtained from the feed over 8 gallons of water, which is more than was usually drunk by them when fed cured fodders alone.
- While no digestion experiments were made with any of the cacti other than prickly pear, the digestion coeficiente of the latter could probably be safely used for all oth@r members of this family, since their composition and other characteristics are similar.
- It may be seen that both steers gained proteins during the first experiment, although both ate a smaller quantity of dry matter which contained less proteins than are required according to Wolff’s standard ration for oxen of their weight at rest m stalls. In the second experiment both animals lost proteins, but here steer No. 1 ate less than half of what was eaten by steer No. 1 in the first experiment, and steer No. 2 ate over 3 pounds less than steer No. 2 of experiment No. 1.
- Animals scour quite badly when fed prickly pear alone: other feeds are needed to supply the proper amount of pro and for these reasons it is better not to feed it alone.
A ration for a 1,000-pound milch cow of 50 pounds of pear, 10 pounds of wheat bran, and 10 pounds of alfalfa furnish about the correct theoretical amount of nutrients, in which the ratio of proteins to carbohydrates would be 1 to 5.46.