VITAMIN A requirements of growing

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1 Effect of Vitamin A Level of Diet on Feed Conversion and Utilization of Energy by Growing Chickens 1 T. E. SHELLENBERGER, D. B. PARRISH AND P. E. SANFORD Kansas Agricultural Experiment Station, Manhattan VITAMIN A requirements of growing chickens reported by different investigators vary from 5 units/lb. of feed to more than 1, units/lb. (Almquist, 1953). Parrish et al. (1955) found that about 7 units vitamin A/lb. of feed were enough for rapid growth of chicks fed a good growing diet. Requirements for growth are important, but data on interrelationships of vitamin A and other factors are needed to extend knowledge of the role of vitamin A. Studies apparently have not been published on the effect of different dietary levels of vitmain A on feed conversion and utilization of feed energy by growing chicks. This is a report on such studies. EXPERIMENTAL Trial 1. Newly hatched straight run, cross-bred broiler strain chicks 2 were depleted for one week on a vitamin A-free diet and then randomized into groups of 12 birds each. Duplicate groups were fed either a high or low energy carotenoid-free feed (Table 1) containing 35, 525, or 7 units vitamin A/lb., supplied as carotene in high quality alfalfa meal. A single group of 12 chicks was fed the high energy feed containing 1,75 units vitamin A from alfalfa meal. A negative control group received no provitamin A. Chicks were raised in batteries; illumination was controlled to 12 hours 1 Contribution No. 599, Department of Chemistry, and No. 2S3, Department of Poultry Husbandry, Kansas State University, Agricultural Experiment Station, Manhattan. 2 Peterson Cornish X Arbor Acre White Rock, hereafter called broiler strain. (Received for publication February 1, 196) 1413 TABLE 1. Composition of high and low energy, vitamin A and carotenoid-free diets'- Ingredient White corn Sorghum grain (milo) Soybean oil meal (5% protein) Soybean oil meal (44% protein) Lard (stabilized) Ground white corn cobs Fish meal (herring, 7% protein) Dried brewer's yeast Steamed bone meal Dried skim milk Calcium carbonate Salt Wesson oil Vitamin premix b Manganous sulfate premix Methionine Glycine High energy 31b. 171b b. 3 1b. lib..51b. 8 gm. 252 gm. 46 gm. 46 gm. Low energy 35 1b. 171b. 281b. 81b. lib..51b. 3 gm. 8 gm. 252 gm. a On the basal unsupplemented diets threefourths of the chicks died within 18 days and the rest were in poor condition. b Vitamin Bi 2 cone. (1 mg./gm.), 1 gm.; vitamin D3, 12, units; riboflavin,.3 gm.; niacin, 2 gm.; calcium pantothenate, 1 gm.; menadione, 6 mg.; choline chloride, 5 gm.; gray wheat shorts, 76 gm. Manganous sulfate monohydrate, 25 gm.; gray wheat shorts, 227 gm. darkness and 12 hours light, and temperature was thermostatically controlled. The high energy feed formula was calculated as 24% protein and 1,6 Cal. productive energy/lb.; the low energy feed was 2% protein and 795 Cal./lb. Both basal feeds appeared to have a good distribution of amino acids, vitamins and other micronutrients, except vitamin A. Feeds were mixed at 2-week intervals to keep vitamin A losses relatively small and to insure freshness. Chick weights were recorded every two weeks. The study continued 8 weeks. When it was terminated, liver and blood samples were taken from two randomly Downloaded from at Penn State University (Paterno Lib) on September 17, 216

2 1414 T. E. SHELLENBERGEE, D. B. PARRISH AND P. E. SANFORD TABLE 2. Response of straight-run broiler strain chicks fed high and low energy diets of different vitamin A contents {trial 1) Units Vit. A/lb. Final wt., lbs., per pen a Liver vitamin A, mmg./gm. Final wt., lbs., per pen" Blood serum Vit. A., mmg./loo ml. Liver vitamin A, mmg./gm , ,65 1, ,25 1, ,27 1, » Wt. after one week depletion plus 8 weeks on expt. b Feed consumption and conversion 2nd through 9th wk. Calculated value. selected birds of each group (one male, one female) for vitamin A analyses. Determination of vitamin A in blood serum was by the Kimble method (1939) and in livers by saponification, ether extraction and Carr- Price technique (Parrish, 1948). Trial 2. Newly hatched male broiler strain chicks, as in trial 1, and male egg strain chicks 3 were depleted one week and randomized into groups of 11 birds each. Duplicate groups were fed the high energy feed, as in trial 1, containing 4, 6, and 8 units vitamin A, supplied as carotene of high quality alfalfa meal. Single groups of each breed received 2, units vitamin A from alfalfa. Negative control groups were included. Other conditions and procedures were as in trial 1. RESULTS In trial 1 (Table 2) chicks receiving high "Hy-line strain, hereafter called egg strain. High energy diet Low energy diet ,23 1, ,2 1, , ,29 3, energy feed containing all levels of vitamin A grew.3 to.s lb. more per bird on.8 to l.s lb. less total feed than did chicks on low energy feed. With both feeds, growth increments decreased as vitamin A content was changed progressively from lower to higher levels. In both trials, final weights included growth during both the one week depletion period and the 8 week experimental period, but feed conversion ratios were calculated using only growth and feed consumption during the 8 week experimental period. Feed conversion ratios were similar ( ) for high energy feeds containing 525, 7, and 1,75 units vitamin A/lb., and better than for feed with 35 units/lb. Feed conversion ratios for low energy feeds containing 525 and 7 units vitamin A/lb. were similar also ( ), and better than for feed with 35 units/lb. An interesting finding was that on both high and low energy diets containing 525 Downloaded from at Penn State University (Paterno Lib) on September 17, 216

3 VITAMIN A AND ENERGY 1415 TABLE 3. Response of broiler strain and egg strain cockerels on a high energy diet of different vitamin A contents (trial 2) Units Vit. A/lb , Final wt., lbs., per pen" Productive energy /lb. (Cal.) Liver vit. A, mmg./gm. Final wt., lbs., per pen Liver vit. A, mmg./gm , ,78 1, CornishXWhite ,21 1, a Wt. after one week depletion plus 8 weeks on experiment. b Feed consumption and conversion 2nd through 9th weeks. Calculated value. units or more vitamin A/lb. the productive energy consumed/lb. gain was similar, differing from the average value, 2,248 Cal., by only ±2%. Birds receiving 35 units vitamin A/lb. of feed did not utilize productive energy so efficiently, especially those fed low energy feed. Total vitamin A intakes per bird increased with increasing levels in the feed, and at each level were highest for chicks fed the low energy diet. Small quantities of vitamin A were found in livers and blood serum of chicks fed even the lower levels of vitamin A. Eye abnormalities, scored by gross observation on a scale -4, 4 were most marked in birds fed high energy diets, but 4 Score 1 mild condition characterized mainly by slight watering of eyes, but no noticeable inflammation. Score 4 marked swelling and/or infection and cheesy deposits in eye. Only scores above 2 indicate a condition of definite pathological change by gross observation. Rock males ,28 1, Egg production strain males ,73 2,69 1,54 2, ,23 4, ,82 5, the incidence and severity decreased to insignificant levels at the highest vitamin A intake. Birds apparently stored small quantities of vitamin A even when intake seemed to be insufficient for maintaining a normal eye condition. Results of trial 2 (Table 3) with broiler strain chicks differed somewhat from those of trial 1. A partial explanation for better growth in trial 2 is use of only male chicks hatched from eggs from mature hens, instead of straight-run chicks hatched from pullet eggs, as in trial 1. Also vitamin A levels in feeds of trial 2 were about 15% higher than in comparable feeds of trial 1, which might have affected results when the lower vitamin A levels were given. In trial 2 dietary levels of vitamin A did not appear to have affected final weights to the same degree as in trial 1, except for broilers on 2, units vitamin A/lb. This increased growth at the highest vitamin A Downloaded from at Penn State University (Paterno Lib) on September 17, 216

4 1416 T. E. SHELLENBEEGEE, D. B. PAREISH AND P. E. SANFORD level is somewhat greater than generally observed in this laboratory. Within-breed growths were similar on feeds containing 6 and 8 units vitamin A/lb. feed and also for egg strain chicks on 2, units/lb. In trial 2, within-breed feed conversion ratios were similar (broiler strain chicks, ; egg strain chicks, ) at all levels of dietary vitamin A. Productive energy consumed/lb. gain by broiler strain chicks was similar (2,21-2,28 Cal.) at all vitamin A intakes and within the same range as in trial 1. For egg strain chicks, higher intakes of productive energy/lb. of gain (273 Cal. ± 2%) were found. Egg strain chicks fed feeds containing all levels of vitamin A had higher liver and blood serum vitamin A concentrations than did broiler strain chicks on the same feeds. The somewhat lower liver and blood serum vitamin A contents in broilers of trial 2 may have been due to the fact that males only were used and vitamin A needs of males for growth may be higher (Coward et al., 1931). In trial 2 only a small amount of eye abnormality was observed and was of little concern. DISCUSSION Data from this study are of interest with respect to vitamin A requirements, although that was not the primary purpose of these trials. Even with feeds mixed bi-weekly, with possible small losses of vitamin A potency, 6-8 units vitamin A/lb. feed, as carotene of alfalfa meal, were adequate for good growth of both broiler and egg strain chicks getting a high energy feed. Because of greater feed intake, the heavier breed consumed more vitamin A per day at each dietary vitamin A level than did the light breed, but intake of the broilers per lb. of bird was 15-2% less (Table 3). Intake of vitamin A per day and per lb. of bird by the heavy breed was higher on low energy feed (Table 2). By using about 2 additional units of vitamin A per lb. of feed, the heavy breed eating the high energy diet would obtain approximately the same vitamin A intake/lb. of gain as those getting a low energy diet. By interpolation this relationship was found to hold even at vitamin A levels above those used in this study. Vitamin A intake may be computed as the quantity needed to achieve a fixed final weight, as for example, a 3-lb. broiler. Data from this study and from previous reports (Parrish et al., 1955; National Research Council, 1954) may be used for those estimates. Egg production strain males eating a high energy feed containing 8 units vitamin A/lb. would require about 12 weeks to reach 3 lbs. and would consume about 85 units vitamin A/day. To reach the same weight, broiler strain chicks would require about lyi weeks and consume 95 units vitamin A/day when fed the high energy diet, and about 1 weeks and 1 units vitamin A/day when fed the low energy diet. Thus, heavier breeds getting a modern high energy practical production diet probably receive more vitamin A/day for equal weight gains than do lighter breeds, and only a few percent less than heavy breeds getting a low energy diet of the same vitamin A content. Even though intake/lb. of bird may be less for the heavier breed, two factors tend to counteract any disadvantage: maintenance needs should be less for birds making production weights in the shorter time, and reserves of vitamin A at hatching would serve the faster growing bird for a greater fraction of total productive life. Baldini and Rosenberg (1955) proposed that nutrients expressed as a percentage of the diet could not be considered fixed values but varied as a direct function of productive energy. They suggested that all nutrients should be reconsidered on the basis of that relationship, since a nutrient present as a fixed percentage may not be adequate Downloaded from at Penn State University (Paterno Lib) on September 17, 216

5 VITAMIN A AND ENERGY 1417 if the animal satisfies its energy requirement before it consumes quantities of diet containing the required quantity of nutrient. Data obtained in this study, at lower levels of supplementation, lend support to the Baldini-Rosenberg proposal, if vitamin A requirement is related to intake/unit gain. But if requirement is related to body weight, as proposed for mammals (Guilbert and Loosli, 1951) and to time to reach production weight, the fast growing bird on present high energy rations should not be handicapped. From a practical standpoint, present requirements (National Research Council, 1954) should provide safe margins for fast growing broilers eating diets with feed-to-gain ratios of 2 or larger for an 8 to 1 week growing period. Levels of vitamin A above 4 units/lb. feed did not appear to affect within-breed conversion ratios or productive energy intakes per lb. of gain, but there was some effect on weight gain, condition of eyes, and deposit of vitamin A in blood and livers. These findings indicate that physiological vitamin A priorities may exist so that an intake that might allow efficient feed utilization may not provide enough in addition for optimum growth or normal tissue condition, as in the eye. Although minor deposits of vitamin A seemed to have occurred at lower vitamin A intakes, marked deposition, especially in the liver, was observed only when supplementation was 1,75 or 2, vitamin A units/lb. feed. SUMMARY A study was made of effect of different levels of vitamin A (as carotene of alfalfa meal) in the diet on utilization of feed by two strains of chicks. Vitamin A fed as carotene in alfalfa meal at 6 units/lb. or more permitted good growth. Within-strain feed conversion ratios on the high energy feed were similar at all vitamin A intakes above 4 units/lb.; they also were similar, but higher, for broiler-strain chicks fed low energy feed. Ad libitum consumptions of productive energy/lb. gain were similar (2,2-2,29 Cal.) for broiler strain chicks getting both high and low energy feeds containing 4 units vitamin A/lb. or more. Intakes of productive energy/lb. gain by egg strain chicks were higher than for broiler strain chicks, but similar (2,69-2,82 Cal.) at all levels of dietary vitamin A. Intakes of vitamin A/lb. of bird and per day by the two strains of chicks were calculated and discussed with respect to requirements and methods of expressing them. Quantities of vitamin A that may be satisfactory for highest feed and feed energy utilization may not be high enough to support maximum growth, or for normal health of certain tissues, such as the eye. In practical feeding, present vitamin A requirements (National Research Council, 1954) should provide safe margins for fast growing broiler strain chicks eating diets with feed-to-gain ratios of 2 or larger during an 8 to 1 week growing period. REFERENCES Almquist, H. J., Evaluation of vitamin requirement data. Poultry Sci. 32: Balidini, J. T., and H. R. Rosenberg, The effect of productive energy level of the diet on the methionine requirement of the chick. Poultry Sci. 34: Coward, K. H., K. M. Key, F. J. Dyer and B. G. E. Morgan, LXIV. Caseinogen for vitamin tests. Biochem. J. 25: Guilbert, H. R., and J. K. Loosli, Comparative nutrition of farm animals. J. Animal Sci. 1: Kimble, M. S., The photocolorimetric determination of vitamin A and carotene in human plasma. J. Lab. Clin. Med. 24: National Research Council, 19S4. Nutrient requirements for domestic animals. No. 1. Nutrient requirements for poultry. Parrish, D. B., Unpublished. Parrish, D. B., P. E. Sanford and T. E. Shellenberger, Unpublished. Downloaded from at Penn State University (Paterno Lib) on September 17, 216