THE PHOSPHORUS REQUIREMENTS OF SHEEP

Transcription

1 THE AMERICAN SOCIETY OF ANIMAL PRODUCTION 345 THE PHOSPHORUS REQUIREMENTS OF SHEEP W. M. BEESON, D. W. BOLIN AND C. W. HICKMAN University o~ Idaho It has been recognized for many years that phosphorus is necessary in livestock rations for normal growth, reproduction, and fattening of livestock. The development of the sugar beet industry in the Snake River Valley of Idaho has resulted in the utilzation of large quantities of beet pulp and beet molasses as an economical part of a fattening ration. These feeds being naturally low in phosphorus created a condition which might result in a phosphorus deficiency if not properly balanced with other feeds. This situation caused considerable interest among the livestock feeders as to whether mineral supplements were needed in feed-lot rations of sheep. Practical experiments were initiated in 1932 to study this problem. Four years of experimentation (1-4) by adding phosphorus supplements to typical Idaho rations, gave negative results for phosphorus supplements. However, these experiments did not answer the question as to the actual phosphorous requirements of sheep. Comparatively few studies on the phosphorus requirements of sheep are reported in the literature. Dutoit and coworkers (5) reported that 1.53 grams of phosphorus daily was sufficient for ewes. Previous work at Idaho (4) has shown that a daily intake of 1.46 grams is insufficient for fattening western lambs. These lambs did not gain rapidly, assimilated their feed inefficiently, and had a low blood phosphorus. According to Martin and coworkers' (6) report, Merino lambs receiving 1.6 grams of phosphorus daily satisfied their phosphorus requirements. Fraps of the Texas Station (7) concluded from mineral balance studies that a daily intake of.74 gram of phosphorus met the maintenance requirements of a ewe weighing 1 pounds. Since the majority of the studies reported to date have dealt primarily with the phosphorus requirements of mature ewes, it was deemed advisable to continue our studies with the phosphorus requirements for fattening lambs. EXPERIMENTAL The object of this study was to determine quantitatively the optimum phosphorus requirements of lambs for growth and fattening. This was accomplished most effectively by using a basal ration that was definitely deficient in phosphorus (established by prelimnary experiment), feeding the sheep individually in stanchions, and adding a known amount of phosphorus to the daily ration at various levels.

2 346 THE AMERICAN SOCIETY OF ANIMAL PRODUCTION Twenty-four lambs with an average initial weight of 71 pounds were selected from the University flock, divided into four lots of six each. The breeds were distributed equally, each lot consisting of four Rambouillets, one Hampshire, and one Lincoln. All the lambs were fed individually twice each day by means of a separate stanchion and feed box. The feed was provided accordingto the appetite of the sheep. Daily phosphorus supplements were added to the basal ration at various levels in the form of di-sodium phosphate. All the lambs were housed in a well-lighted and well-ventilated building provided with an outside pen. The lambs were kept off the ground by means of a wooden floor in both the inside and outside pens. Shavings were used as bedding. The lambs were weighed individually every fourteen days and blood samples were taken every twenty-eight days. Blood analyses ~vere made for calcium and phosphorus. The basal ration was analyzed every month for calcium and phosphorus and a complete feed analysis was determined at the beginning and end of the experiment. The same basal ration was used in all lots consisting of dried molasse~ beet pulp 73 percent, cane molasses 1 percent, alfalfa hay (ground) 1 percent, and blood meal 7 percent. This ration was fed as a mixture, thus giving each lot a ration containing the same percentage composition of digestible nutrients, minerals and vitamins. The rations were as follows: daily. daily. daily. I. Basal ration (.8 percent P). II. Basal ration plus.5 gram of phosphorus per head III. IV. Basal ration plus 1. gram of phosphorus per head Basal ration plus 1.5 grams phosphorus per head RESULTS AND DISCUSSION A ration definitely deficient in phosphorus was established for sheep. The basal ration was low in phosphorus, but adequate in the other essentials necessary for an adequate diet. The lambs in I receiving only.82 gram of phosphorus daily showed definite symptoms of aphosphorosis. The blood phosphorus was reduced from a normal level of 5.2 mg. per 1 cc. of plasma to a deficient level of 2.69 mg. per 1 cc. The low level of phosphorus was evident after 28 days on the low phosphorus basal ration. Further evidence of aphosphorosis in I was manifested by eating boards, shavings, and wool. Several

3 THE AMERICAN SOCIETY OF ANIMAL PRODUCTION 347 of the sheep on a high phosphorus diet were practically stripped of their wool by the phosphorus deficient animals. Observations were made to be certain that only the animals on a low phosphorus diet were eating foreign materials. Gains in I were below normal, but the contrast in gain between the various lots was not very great, owing to the fact it was difficult to keep the sheep on feed. The lambs in II receiving.5 gram of phosphorus per head daily in addition to the basal ration in some cases showed a phosphorus deficiency. Half of the lambs demonstrated a phosphorus deficiency as evidenced by a definite reduction in the blood phosphorus level. These lambs ingested daily 1.32 grams of phosphorus. This suggests that the requirements for individual lambs varies and that a daily intake of 1.32 grams of phosphorus is on the borderline of meeting the requirements of a lamb for phosphorus. III and IV receiving respectively 1.85 and 2.4 grams of phosphorus daily made average gains and maintained a normal blood phosphorus during the entire period. These lambs were more thrifty than the other lambs and did not demonstrate any symptoms of phosphorus deficiency by eating foreign materials. The blood calcium level was normal for all sheep. EXPERIMENT II Experimental This experiment was conducted to make a further study of the phosphorus needs of lambs under more practical feed lot conditions. The experiment was designed so that similar groups of lambs received rations which contained the same amounts of digestible nutrients, minerals and vitamins, but which contained different levels of phosphorus. The manner in which the lambs reacted in body growth, efficiency of feed utilization and blooci composition were taken as the criteria for determining the optimum amount of phosphorus to meet the requirements for normal growth. Five lots of feeder lambs, with 25 lambs per lot were fed for a period of 133 days on rations varying in the level and source of phosphorus. These lambs were typical range lambs as used in Idaho feed lots. The low phosphorus basal ration consisted of a mixture of dried beet pulp 44.2 percent, alfalfa hay (chopped) 5 percent, blood meal, 5. percent, and limestone.8 percent. The mixture was fed twice daily according to the appetite of the sheep. Corn silage was fed at the same rate to all lambs, 1 pound per head daily. The lambs were kept in an open tot with free access to salt and water.

4 348 THE AMERICAN SOCIETY OF ANIMAL PRODUCTION The rations were as follows: I. Basal ration with low phosphorus alfalfa (.13% P). II. Basal ration with high phosphorus alfalfa (.16% P). III. Basal ration (I) plus.7% bonemeal (.23% P). IV. Basal ration (I) plus cottonseed meal as a source of phosphorus (.23% P). V. Basal ration (I) reduced to 26~ alfalfa (.1% P). Blood samples were taken at definite intervals and analyzed for calcium and phosphorus. Feed samples were collected once a month for calcium and phosphorus analysis. An accurate check was kept on mineral intake. Results and Discussion A complete summary of data pertaining to this experiment is presented in Table I. Considering the data in this table, it is quite apparent that the lambs in V receiving 1.31 grams of phosphorus daily showed signs of phosphorus deficiency. The blood phosphorus was reduced from 5. mg. to 3.87 mg. per 1 cc. of plasma. Several of the lambs showed a lower level of phosphorus than indicated by this average and a few lambs had a normal blood phosphorus. These results agree closely with the results obtained in Experiment I. These data indicate that a ration containing.1 percent phosphorus does not meet the requirements for optimum gains. The addition of.7 percent bonemeal to a ration containing.13 percent phosphorus caused an increase in the average daily gain from.22 to.27 pound and reduced the feed requirements per 1 pounds of gain 15.8 percent. Although the average blood phosphorus content in I does not show a low level, certain individuals in the group were definitely deficient. At least the daily intake of 1.7 grams did not support average gains and also decreased the efficiency of food utilization. Cottonseed meal was used to supply phosphorus to the basal ration. The phosphorus was maintained at the same level as III, in order to make a direct comparison between the efficiency of an organic and inorganic source of phosphorus. There was a slight difference in the rapidity and economy of gains which may be attributed to the source of phosphorus. However, the difference in the source of protein in the two lots may have caused part of the difference. The substitution of a high phosphorus alfalfa hay (.227 percent P) for a low phosphorus alfalfa hay (.183 percent P) did not cause any signifcant change in the blood phosphorus gains or feed requirements of the lambs. Although no material dif-

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6 35 THE AMERICAN SOCIETY OF ANLMAL PRODUCTION ference was shown in favor of a higher phosphorus alfalfa in this experiment, a definite benefit might result where a high phosphorus alfalfa was included in an extremely low phosphorus ration. SUMMARY 1. A phosphorus deficient ration was established for sheep. 2. Growth was retarded and the blood phosphorus lowered to an abnormal level (2 to 3 mg/1 cc. blood plasma) when the lambs received from.82 to 1.32 grams of phosphorus per head daily. Phosphorus deficiency was manifested by eating wood shavings, fence posts~ feed boxes, and wool. Phosphorus deficient lambs were emaciated, thin and listless. 3. Phosphorus deficiency was produced by feeding a ration containing.1 percent phosphorus, which was indicated by the slow gains and low blood phosphorus. 4. The addition of.7 percent bonemeal to a ration containing.13 percent phosphorus caused an increase in the average daily gain from.22 to.27 pound and reduced the feed requirements per 1 pounds of gain 15.8 percent. 5. Lambs ingesting 2. to 2.5 grams of phosphorus daily satisfied their phosphorus requirements as indicated by a normal blood phosphorus, rapid gains, and a healthy appearance. 6. An organic source of phosphorus as present in cottonseed meal was not as available to lambs as the inorganic phosphorus in bonemeai. 7. These studies indicate that a fattening lamb requires about 2.5 grams of phosphorus daily per 1 pounds of live weight for efficient and rapid gains. BIBLOGRAPHY 1. -Annual Report, University of Idaho, Bul Annual Report, University of Idaho, Bul Annual Report, University of Idaho, Bul Annual Report, University of Idaho, Bul Dutoit, P. J., B. A. Phil, A. I. Malan and J. W. Graenewald--17th report of the director of Veterinary Services and Animal Industry, Union of South Africa (1931). 6. Martin, C. J., and A. W. Peirce--Council for Scientific and Industrial Research, Bul. 77, (1934). 7. Fraps, C. S., Texas Agr. Expt. Sta. Bul (1918).