252 FEEDS AND FEEDING 



not provide a maintenance ration for stock. According to Vinson, 38 

 cattle in the deserts of Sonora, Mexico, subsist for 3 months of the year 

 on little else than the fruits of cacti, but they become emaciated. When 

 fed in large amounts with no dry feed, cacti tend to produce scours. As 

 cacti are all low in protein, this forage should be supplemented by pro- 

 tein-rich feeds, such as alfalfa hay or cottonseed meal. From trials at 

 the Arizona Station 37 Vinson concludes that 6 Ibs. or more of cholla 

 fruit with 0.5 to 0.75 Ib. of alfalfa hay per day will maintain a sheep in a 

 lean but healthy condition. 



In a trial by Griffiths 38 cows fed 3 Ibs. cottonseed meal and 8 to 12 Ibs. 

 of rice bran per head daily ate about 150 Ibs. of singed prickly pear, 6 

 Ibs. of pear equaling 1 Ib. of sorghum hay in feeding value. A lot of 27 

 steers fed a ration of 96 Ibs. chopped prickly pear and 4.4 Ibs. of cotton- 

 seed meal gained 1.75 Ibs. per head daily, requiring 55 Ibs. of pear and 

 2.5 Ibs. of cottonseed meal per pound of gain. 



Spineless cacti, which during recent years have been extensively ad- 

 vertised, have long been known in Mexico and the Mediterranean coun- 

 tries. Most spineless varieties are not hardy where the temperature falls 

 below 20 F. and are thus of limited value in the southwestern states. 

 These cacti cannot survive on the open range because cattle will graze 

 and destroy them, and moreover they must be enclosed by rabbit-proof 

 fences, as these animals are fond of them. Griffiths 39 reports yearly 

 yields of 20 to 25 tons of spineless cactus per acre without irrigation at 

 Chico in the Sacramento Valley, California ; this locality having an aver- 

 age rainfall of 23 inches. These yields were secured with expert culti- 

 vation and when a perfect stand was carefully maintained. 



The chief importance of cacti will undoubtedly be to furnish emer- 

 gency forage for stock in the semi-arid regions in case of drought, for 

 these plants are able to utilize most efficiently small and irregular sup- 

 plies of moisture. For this purpose plantations of the spiny cacti may be 

 established on the open range, where they will be able to grow and hold 

 their own until drawn upon in time of serious drought, for cattle will 

 not graze them when other feed is reasonably abundant. 



IV. POISONOUS PLANTS 



Only the briefest mention can be made of the leading plants poison- 

 ous to stock. One in trouble should consult a competent veterinarian or 

 send suspected specimens to the experiment station of his state or to the 

 United States Department of Agriculture. 



395. Plants carrying prussic acid. Prussic acid, a most deadly poison, 

 has been found in over 200 species of plants, including the sorghums, 

 the wild cherry, vetch, Java bean, flax, etc. The poison is not present as 

 free prussic acid, but in the form of complex compounds, called glucosides 



M Ariz. Bui. 67. *U. S. Dept. Agr. Bur. Anim. Indus., Bui. 91. 



"Ariz. Rpt. 21. '"IT. S. Dept. Agr., Farmers' Buls. 483, 1072. 



