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Activity of Vitamin K1 and Menadione Sodium Bisulfite Complex When Measured by Mortality of Chicks with Cecal Coccidiosis1
Activity of Vitamin Ki and Menadione Sodium Bisulfite Complex When Measured by Mortality of Chicks with Cecal Coccidiosis1 R. H. HARMS,2 P. W. WALDROUP2 AND D. D. COX 3 Florida Agricultural Experiment Stations, Gainesville, Florida (Received for publication April 2, 1962)
T
HE National Research Council (1954, 1960) has increased the estimated vitamin K requirement in poultry feed from 0.18 to 0.24 mg. of vitamin Kx per pound. This increase in the estimated requirement was based on recent reports which indicate that a level of 0.18 mg. per pound of vitamin Ki is not adequate (Perdue et al., 1957; and Nelson and Norris, 1960,1961a, b). Since vitamin K t is not usually used to supply vitamin K activity for poultry feeds, it is essential to know the relative activity of materials used to meet the vitamin K requirement. The most commonly used source of vitamin K activity in poultry feeds is menadione sodium bisulfite complex.* Considerable variation in the relative activity of these two compounds has been reported. Perdue et al. (1957) found the activity of MSBC to be 1.5 times that of vitamin Ki. Using a purified diet, Nelson and Norris (1960) found MSBC and vitamin K% to be equally active for the chick. In a later report these workers (Nelson and Norris, 1961a) showed the activity of vitamin Kx to be greater than that of
1 Florida Agricultural Experiment Station Journal Series No. 1437. 2 Department of Poultry Science. 3 Department of Veterinary Science. * Menadione sodium bisulfite complex is a compound defined as containing not less than 63% of menadione sodium bisulfite U.S.P. Hereafter the compound will be referred to as MSBC.
MSBC when the diet contained 0.1% of sulfaquinoxaline. Using mortality from cecal coccidiosis as a measure, Harms et al. (1960) reported that the activity of vitamin K.! appeared to be four times as great as MSBC. In view of the variation reported in the comparative activity of MSBC and vitamin Ki, experiments were conducted to further evaluate the relative activity of these compounds. EXPERIMENTAL PROCEDURE
Four experiments were conducted with Vantress X White Plymouth Rock chicks. The chicks were sexed, intra-ocularly vaccinated for bronchitis and Newcastle disease at one day of age, and randomized into groups containing five males and five females. All chicks were reared in electrically heated batteries with thermostatic temperature controls and raised wire floors. Experimental diets and tap water were given ad libitum, from one day of age through the entire experimental period. The water was changed every other day and the troughs were cleaned and disinfected with a chlorine solution to minimize bacterial synthesis of vitamin K. The composition of the vitamin K low basal diet is shown in Table 1. Graded levels of MSBC (0.0 to 9.72 g./ton), vitamin Kj (0.0 to 0.68 g./ton) and alfalfa meal (0.75, 1.5 and 3.0 percent) and three
1836
1837
COMPARATIVE VITAMIN K ACTIVITIES TABLE 1.—Composition of basal diet Ingredient Yellow corn Soybean oil meal (50% protein) Defluorinated phosphate (34% + 18% P) Ground limestone Iodized salt Micro-ingredients 1
Lbs./cwt. 6S.2 31.0 Ca 1.8 0.7 0.4 0.9
1 Supplies per pound of diet: 2,268 I.U. vitamin A, 340 I.C.U. vitamin D 3 , 10 meg. vitamin B12, 2 mg. riboflavin, 9 mg. calcium pantothenate, 18 mg. niacin, 261 mg. choline chloride, 10 mg. terramycin HCI, 57 mg. santoquin, 80 mg. manganese sulphate 9 mg. iron, 0.9 mg. copper, 35 mg. manganous oxide, 90 meg. cobalt, 5 mg. iodine and 45 meg. zinc.
percent menhaden fish meal were added to the basal diet to form the experimental diets (Table 2). The MSBC and vitamin Ki were pre-mixed in ground yellow corn and aliquots of this premix added to the basal diet to produce the desired level of vitamin K activity. The alfalfa meal and menhaden fish meal were added to the diet at the expense of an equal amount of basal diet. No attempt was made to determine the vitamin K activity of the alfalfa or fish meal. Five replicate pens of five males and five females were fed each of the experimental diets in experiments 1, 2, and 3, with three replicates used per treatment in experiment 4. Birds were inoculated at 21 days of age with sporulated oocysts of Eimeria tenetta, with each bird receiving 30,000 oocysts in experiments 1, 2, and 3, and with 5,000 or 10,000 given in experiment 4. Prothrombin time determinations were made on eight male and eight female chicks from selected treatments in experiment 3. The procedure described by Nelson and Norris (1960) was used for the prothrombin determinations. Statements of probability in this paper are based on the analysis of variance according to Snedecor (1956), with significant differences between treatment means
determined by Duncan's multiple range test (1955). RESULTS AND DISCUSSION Data from these experiments indicate that vitamin Ki is three times as effective as MSBC, on a weight basis, in preventing mortality when chicks are artificially infected with cecal coccidiosis (Table 2). Although considerable variation occurred between experiments, a plot of the logarithm of the vitamin K activity against average mortality in experiments 1, 2 and 3 indicated that 0.44 and 1.2 grams per ton, respectively of vitamin Kt and MSBC was adequate to give maximum protection when chicks were suffering from a severe attack of cecal coccidiosis. The vitamin K activity furnished by one and one-half percent alfalfa meal in experiments 1 and 2 appeared to be adequate to meet the chicks' need under the conditions of these experiments. The vitamin K activity furnished by the three percent fish meal in experiment 3 provided no obvious protection against mortality. TABLE 2.—Mortality of chicks with coccidiosis when fed diets containing different levels and sources of vitamin K activity {Experiments 1, 2 and 3) Vitamin K activity source None
Mortality Level (g./ton) 0.0
Experiment 1*
(%)
86/3" b
Experiment 2*
(%)
Experiment 3 *
(%)
81.5"
96.0" b
MSBC
0.36 0.72 1.08 3.24 9.72
54.5 37.5°d 33.8d 31.3de 31.0d°
60.7» 41.5b 44.0b 50.0b 54.0b
Ki
0.115 0.23 0.46 0.68
56.3b, 25.0et 42.5° 18.0 f
62.0"b 56.0b 40.5b 36.3b
25.0ef
—
47.6°
23.0of
38.0b
0.75% alfalfa meal
— — -
—
45.6b
— —
3 % menhaden fish meal
-
—
—
84.0"
3 % alfalfa meal 1.5% alfalfa meal
90.0" 77.6"b 52.0° 37.2° 77 7 a k 57]o b ° 51.6°
' Means having different superscripts in each experiment are significantly different.
1838
R. H. HARMS, P. W. WALDROUP AND D. D. COX
TABLE 3.—Prothrombin time of chicks when fed diets containing different levels and sources of vitamin K activity {Experiment 3) Vitamin K activity Source None
Prothrombin time 1
Level (g./ton) 0.0
(sec.) 120.0"
0.36 0.72 9.72
85.8 b 60.1" 53.4 cd
0.46
54.8
cd
3 % alfalfa meal
—
50.0 d
3 % menhaden fish meal
—
130.8"
MSBC
Ki
1
Means having different superscripts are significantly different.
Prothrombin time of chicks in experiment 3 (Table 3) indicated that a level in excess of 0.72 grams of MSBC per ton of feed was required for minimum prothrombin time. This would indicate that the required level of vitamin K activity was not increased by the presence of coccidiosis. Experiment 4 (Table 4) was conducted to compare the relative activity of vitamin K.! and MSBC when chicks were exposed to fewer oocysts. Results from this test again indicate that vitamin K.! has approximately three times the activity of MSBC. Although an inverse linear relationship exists between the vitamin K activity of the diet and mortality of chicks from cecal coccidiosis, this did not appear to be a satisfactory assay for vitamin K activity in a diet because of the large variability between replications and experiments. Changing the number of oocysts given to each bird did appear to decrease this variability. SUMMARY
Four experiments conducted with dayold Vantress X White Plymouth Rock chicks indicated the relative activity of vitamin Kx on a weight basis, to be three times that of MSBC when measured by
mortality from cecal coccidiosis. Although an inverse relationship existed between vitamin K activity in the diet and mortality from coccidiosis, this did not appear to be a satisfactory assay of the vitamin K activity of the diet. Coccidiosis did not appear to increase the chicks' requirement for vitamin K. ACKNOWLEDGMENTS
This investigation was supported in part by a grant-in-aid from Abbott Laboratories, North Chicago, Illinois. The authors are indebted to Abbott Laboratories for the MSBC; to Merck and Company, Rahway, New Jersey, for the vitamin Ki and '.o Dr. Charles Beale for assisting in the prothrombin determinations. REFERENCES Duncan, D. B., 1955. Multiple range and multiple F tests. Biometrics, 11: 1-42. Harms, R. H., P. W. Waldroup and D. D. Cox, 1960. Comparison of various sources and levels of vitamin K activity using chicks with cecal coccidiosis. Proc. Soc. Exp. Biol. Med. 105: 230-232. Nelson, T. S., and L. C. Norris, 1960. Studies on the vitamin K requirements of the chick. I. Requirement of the chick for vitamin Kj, menadione and menadione sodium bisulfite. J. Nutrition, 72: 137-144.
TABLE 4.—Mortality of chicks infected with coccidiosis when fed diets containing different levels and sources of vitamin K activity {Experiment 4) Vitamin K activity Level (g./ton)
Mortality (oocysts/bird) 5,000
(%)
10,000
(%)
Av. 1
(%)
32.0
93.1
62.6"
0.36 0.72 1.08 9.72
15.4 0.0 3.6 0.0
24.1 13.8 13.3 0.0
19.8 b 6.9'"' 8.5 b ° 0.0
0.18 0.36 1.08
0.0 0.0 0.0
17.8 13.3 6.9
8.9 bo 6.T* 3.5"
1 Means having different superscripts are significantly different.
COMPARATIVE VITAMIN K ACTIVITIES Nelson, T. S., and L. C. Norris, 1961a. Studies on the vitamin K requirement of the chick. II. Effect of sulfaquinoxaline on the quantitative requirements of the chick for vitamin Ki, menadione and menadione sodium bisulfite. J. Nutrition, 73: 135-142. Nelson, T. S., and L. C. Norris, 1961b. Studies on the vitamin K requirement of the chick. The effect of age and cecectomy on the vitamin K requirement of the chick. Poultry Sci. 40: 392-395. National Research Council, 1954. Nutrient re-
1839
quirements for domestic animals. No. 1. Nutrient allowances for poultry. Washington, D.C. National Research Council, 1960. Nutrient requirements for domestic animals. No. 1. Nutrient allowances for poultry. Washington, D.C. Perdue, H. S., H. C. Spruth and D. V. Frost, 1957. Comparison of vitamin K activities of vitamin K, and Klotogen F (menadione sodium bisulfite complex). Poultry Sci. 36: 633635. Snedecor, G. W., 1956. Statistical Methods. 5th ed., The Iowa State College Press, Ames, Towa.
Light Intensity Studies with Broilers1'2 W. C. SKOGLUND AND D. H. PALMER3 Department of Poultry Science, University of New Hampshire, Durham, New Hampshire (Received for publication April 4, 1962)
T
HE ROLE which light intensity plays in broiler production has never been fully evaluated or understood. The possibility of a relationship between the amount of light in broiler houses and the problem of feather picking and cannibalism has been suggested by Clark (1953) and Biester and Schwarte (1952). This has been discussed, also, by an anonymous author in the Purina Eastern Broiler Letter of August 1952. This publication recommended that the number of windows be reduced, and that only enough artificial light be provided to enable the birds to see the feed and water. Light intensity studies with broilers at the University of New Hampshire, were
1 Published with approval of the Director, N. H. Agr. Exp. Sta. as Scientific Contribution No. 291. 3 This study was conducted as part of the contributing project of the New Hampshire Agricultural Experiment Station to the Northeast Regional Poultry Housing Project (NE-8). 'Present address: Department of Animal and Poultry Industry, Univ. of Delaware, Newark, Delaware.
initiated to determine if intensity played a role in the incidence of cannibalism. Skoglund (1962) found that light intensities of 15, 60 and 120 foot candles at the feeder height exerted no influence upon the incidence of feather picking in broilers; but there was a slight trend for the birds exposed to the lower light intensities to have a heavier body weight. The studies reported in this paper were concerned with determining the lower limits of light intensity that would promote maximum weight gains. EXPERIMENTAL PROCEDURE
Pens 4' X 15' in size, completely blacked out but with the desired light intensity provided by artificial illumination were utilized. Ventilation was provided by air intake fan and duct, and heat was supplied by a hot water brooding system. Hover lights of 7^2 watts were used the first three weeks to attract chicks to the heat source. After that period the only source of light was the bulbs used to give the desired light intensity. The New England College Conference
T
HE National Research Council (1954, 1960) has increased the estimated vitamin K requirement in poultry feed from 0.18 to 0.24 mg. of vitamin Kx per pound. This increase in the estimated requirement was based on recent reports which indicate that a level of 0.18 mg. per pound of vitamin Ki is not adequate (Perdue et al., 1957; and Nelson and Norris, 1960,1961a, b). Since vitamin K t is not usually used to supply vitamin K activity for poultry feeds, it is essential to know the relative activity of materials used to meet the vitamin K requirement. The most commonly used source of vitamin K activity in poultry feeds is menadione sodium bisulfite complex.* Considerable variation in the relative activity of these two compounds has been reported. Perdue et al. (1957) found the activity of MSBC to be 1.5 times that of vitamin Ki. Using a purified diet, Nelson and Norris (1960) found MSBC and vitamin K% to be equally active for the chick. In a later report these workers (Nelson and Norris, 1961a) showed the activity of vitamin Kx to be greater than that of
1 Florida Agricultural Experiment Station Journal Series No. 1437. 2 Department of Poultry Science. 3 Department of Veterinary Science. * Menadione sodium bisulfite complex is a compound defined as containing not less than 63% of menadione sodium bisulfite U.S.P. Hereafter the compound will be referred to as MSBC.
MSBC when the diet contained 0.1% of sulfaquinoxaline. Using mortality from cecal coccidiosis as a measure, Harms et al. (1960) reported that the activity of vitamin K.! appeared to be four times as great as MSBC. In view of the variation reported in the comparative activity of MSBC and vitamin Ki, experiments were conducted to further evaluate the relative activity of these compounds. EXPERIMENTAL PROCEDURE
Four experiments were conducted with Vantress X White Plymouth Rock chicks. The chicks were sexed, intra-ocularly vaccinated for bronchitis and Newcastle disease at one day of age, and randomized into groups containing five males and five females. All chicks were reared in electrically heated batteries with thermostatic temperature controls and raised wire floors. Experimental diets and tap water were given ad libitum, from one day of age through the entire experimental period. The water was changed every other day and the troughs were cleaned and disinfected with a chlorine solution to minimize bacterial synthesis of vitamin K. The composition of the vitamin K low basal diet is shown in Table 1. Graded levels of MSBC (0.0 to 9.72 g./ton), vitamin Kj (0.0 to 0.68 g./ton) and alfalfa meal (0.75, 1.5 and 3.0 percent) and three
1836
1837
COMPARATIVE VITAMIN K ACTIVITIES TABLE 1.—Composition of basal diet Ingredient Yellow corn Soybean oil meal (50% protein) Defluorinated phosphate (34% + 18% P) Ground limestone Iodized salt Micro-ingredients 1
Lbs./cwt. 6S.2 31.0 Ca 1.8 0.7 0.4 0.9
1 Supplies per pound of diet: 2,268 I.U. vitamin A, 340 I.C.U. vitamin D 3 , 10 meg. vitamin B12, 2 mg. riboflavin, 9 mg. calcium pantothenate, 18 mg. niacin, 261 mg. choline chloride, 10 mg. terramycin HCI, 57 mg. santoquin, 80 mg. manganese sulphate 9 mg. iron, 0.9 mg. copper, 35 mg. manganous oxide, 90 meg. cobalt, 5 mg. iodine and 45 meg. zinc.
percent menhaden fish meal were added to the basal diet to form the experimental diets (Table 2). The MSBC and vitamin Ki were pre-mixed in ground yellow corn and aliquots of this premix added to the basal diet to produce the desired level of vitamin K activity. The alfalfa meal and menhaden fish meal were added to the diet at the expense of an equal amount of basal diet. No attempt was made to determine the vitamin K activity of the alfalfa or fish meal. Five replicate pens of five males and five females were fed each of the experimental diets in experiments 1, 2, and 3, with three replicates used per treatment in experiment 4. Birds were inoculated at 21 days of age with sporulated oocysts of Eimeria tenetta, with each bird receiving 30,000 oocysts in experiments 1, 2, and 3, and with 5,000 or 10,000 given in experiment 4. Prothrombin time determinations were made on eight male and eight female chicks from selected treatments in experiment 3. The procedure described by Nelson and Norris (1960) was used for the prothrombin determinations. Statements of probability in this paper are based on the analysis of variance according to Snedecor (1956), with significant differences between treatment means
determined by Duncan's multiple range test (1955). RESULTS AND DISCUSSION Data from these experiments indicate that vitamin Ki is three times as effective as MSBC, on a weight basis, in preventing mortality when chicks are artificially infected with cecal coccidiosis (Table 2). Although considerable variation occurred between experiments, a plot of the logarithm of the vitamin K activity against average mortality in experiments 1, 2 and 3 indicated that 0.44 and 1.2 grams per ton, respectively of vitamin Kt and MSBC was adequate to give maximum protection when chicks were suffering from a severe attack of cecal coccidiosis. The vitamin K activity furnished by one and one-half percent alfalfa meal in experiments 1 and 2 appeared to be adequate to meet the chicks' need under the conditions of these experiments. The vitamin K activity furnished by the three percent fish meal in experiment 3 provided no obvious protection against mortality. TABLE 2.—Mortality of chicks with coccidiosis when fed diets containing different levels and sources of vitamin K activity {Experiments 1, 2 and 3) Vitamin K activity source None
Mortality Level (g./ton) 0.0
Experiment 1*
(%)
86/3" b
Experiment 2*
(%)
Experiment 3 *
(%)
81.5"
96.0" b
MSBC
0.36 0.72 1.08 3.24 9.72
54.5 37.5°d 33.8d 31.3de 31.0d°
60.7» 41.5b 44.0b 50.0b 54.0b
Ki
0.115 0.23 0.46 0.68
56.3b, 25.0et 42.5° 18.0 f
62.0"b 56.0b 40.5b 36.3b
25.0ef
—
47.6°
23.0of
38.0b
0.75% alfalfa meal
— — -
—
45.6b
— —
3 % menhaden fish meal
-
—
—
84.0"
3 % alfalfa meal 1.5% alfalfa meal
90.0" 77.6"b 52.0° 37.2° 77 7 a k 57]o b ° 51.6°
' Means having different superscripts in each experiment are significantly different.
1838
R. H. HARMS, P. W. WALDROUP AND D. D. COX
TABLE 3.—Prothrombin time of chicks when fed diets containing different levels and sources of vitamin K activity {Experiment 3) Vitamin K activity Source None
Prothrombin time 1
Level (g./ton) 0.0
(sec.) 120.0"
0.36 0.72 9.72
85.8 b 60.1" 53.4 cd
0.46
54.8
cd
3 % alfalfa meal
—
50.0 d
3 % menhaden fish meal
—
130.8"
MSBC
Ki
1
Means having different superscripts are significantly different.
Prothrombin time of chicks in experiment 3 (Table 3) indicated that a level in excess of 0.72 grams of MSBC per ton of feed was required for minimum prothrombin time. This would indicate that the required level of vitamin K activity was not increased by the presence of coccidiosis. Experiment 4 (Table 4) was conducted to compare the relative activity of vitamin K.! and MSBC when chicks were exposed to fewer oocysts. Results from this test again indicate that vitamin K.! has approximately three times the activity of MSBC. Although an inverse linear relationship exists between the vitamin K activity of the diet and mortality of chicks from cecal coccidiosis, this did not appear to be a satisfactory assay for vitamin K activity in a diet because of the large variability between replications and experiments. Changing the number of oocysts given to each bird did appear to decrease this variability. SUMMARY
Four experiments conducted with dayold Vantress X White Plymouth Rock chicks indicated the relative activity of vitamin Kx on a weight basis, to be three times that of MSBC when measured by
mortality from cecal coccidiosis. Although an inverse relationship existed between vitamin K activity in the diet and mortality from coccidiosis, this did not appear to be a satisfactory assay of the vitamin K activity of the diet. Coccidiosis did not appear to increase the chicks' requirement for vitamin K. ACKNOWLEDGMENTS
This investigation was supported in part by a grant-in-aid from Abbott Laboratories, North Chicago, Illinois. The authors are indebted to Abbott Laboratories for the MSBC; to Merck and Company, Rahway, New Jersey, for the vitamin Ki and '.o Dr. Charles Beale for assisting in the prothrombin determinations. REFERENCES Duncan, D. B., 1955. Multiple range and multiple F tests. Biometrics, 11: 1-42. Harms, R. H., P. W. Waldroup and D. D. Cox, 1960. Comparison of various sources and levels of vitamin K activity using chicks with cecal coccidiosis. Proc. Soc. Exp. Biol. Med. 105: 230-232. Nelson, T. S., and L. C. Norris, 1960. Studies on the vitamin K requirements of the chick. I. Requirement of the chick for vitamin Kj, menadione and menadione sodium bisulfite. J. Nutrition, 72: 137-144.
TABLE 4.—Mortality of chicks infected with coccidiosis when fed diets containing different levels and sources of vitamin K activity {Experiment 4) Vitamin K activity Level (g./ton)
Mortality (oocysts/bird) 5,000
(%)
10,000
(%)
Av. 1
(%)
32.0
93.1
62.6"
0.36 0.72 1.08 9.72
15.4 0.0 3.6 0.0
24.1 13.8 13.3 0.0
19.8 b 6.9'"' 8.5 b ° 0.0
0.18 0.36 1.08
0.0 0.0 0.0
17.8 13.3 6.9
8.9 bo 6.T* 3.5"
1 Means having different superscripts are significantly different.
COMPARATIVE VITAMIN K ACTIVITIES Nelson, T. S., and L. C. Norris, 1961a. Studies on the vitamin K requirement of the chick. II. Effect of sulfaquinoxaline on the quantitative requirements of the chick for vitamin Ki, menadione and menadione sodium bisulfite. J. Nutrition, 73: 135-142. Nelson, T. S., and L. C. Norris, 1961b. Studies on the vitamin K requirement of the chick. The effect of age and cecectomy on the vitamin K requirement of the chick. Poultry Sci. 40: 392-395. National Research Council, 1954. Nutrient re-
1839
quirements for domestic animals. No. 1. Nutrient allowances for poultry. Washington, D.C. National Research Council, 1960. Nutrient requirements for domestic animals. No. 1. Nutrient allowances for poultry. Washington, D.C. Perdue, H. S., H. C. Spruth and D. V. Frost, 1957. Comparison of vitamin K activities of vitamin K, and Klotogen F (menadione sodium bisulfite complex). Poultry Sci. 36: 633635. Snedecor, G. W., 1956. Statistical Methods. 5th ed., The Iowa State College Press, Ames, Towa.
Light Intensity Studies with Broilers1'2 W. C. SKOGLUND AND D. H. PALMER3 Department of Poultry Science, University of New Hampshire, Durham, New Hampshire (Received for publication April 4, 1962)
T
HE ROLE which light intensity plays in broiler production has never been fully evaluated or understood. The possibility of a relationship between the amount of light in broiler houses and the problem of feather picking and cannibalism has been suggested by Clark (1953) and Biester and Schwarte (1952). This has been discussed, also, by an anonymous author in the Purina Eastern Broiler Letter of August 1952. This publication recommended that the number of windows be reduced, and that only enough artificial light be provided to enable the birds to see the feed and water. Light intensity studies with broilers at the University of New Hampshire, were
1 Published with approval of the Director, N. H. Agr. Exp. Sta. as Scientific Contribution No. 291. 3 This study was conducted as part of the contributing project of the New Hampshire Agricultural Experiment Station to the Northeast Regional Poultry Housing Project (NE-8). 'Present address: Department of Animal and Poultry Industry, Univ. of Delaware, Newark, Delaware.
initiated to determine if intensity played a role in the incidence of cannibalism. Skoglund (1962) found that light intensities of 15, 60 and 120 foot candles at the feeder height exerted no influence upon the incidence of feather picking in broilers; but there was a slight trend for the birds exposed to the lower light intensities to have a heavier body weight. The studies reported in this paper were concerned with determining the lower limits of light intensity that would promote maximum weight gains. EXPERIMENTAL PROCEDURE
Pens 4' X 15' in size, completely blacked out but with the desired light intensity provided by artificial illumination were utilized. Ventilation was provided by air intake fan and duct, and heat was supplied by a hot water brooding system. Hover lights of 7^2 watts were used the first three weeks to attract chicks to the heat source. After that period the only source of light was the bulbs used to give the desired light intensity. The New England College Conference