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A Comparison of Three Methods of Supplying Calcium in the Diet of Laying Chickens
976
G. J. BANWART REFERENCES
A Comparison of Three Methods of Supplying Calcium in the Diet of Laying Chickens ARNON L. MEHRING, JR. Lime Crest Research Laboratory, Limestone Products Corporation of America, Newton, New Jersey (Received for publication January 30, 1964)
F
OR many years it has been the practice to include in the feed of laying chickens only a part of the calcium needed for egg production, and to give the chickens free access to a calcium supplement. It was believed that the chickens would consume enough additional calcium to fully meet their needs. Oddly enough, there is but little experimental evidence on record to support that belief. Berg et al. (1944) reported the results of a comparison of two methods of supplying calcium to laying pullets, that of putting the full allowance in the feed, and that of putting a part of it in the feed and giving the pullets free access to limestone grit. The feed that supplied the full allowance contained 3.08 percent of calcium.
Three other feeds contained, respectively, 0.926, 1.875, and 2.727 percent of calcium; and the chickens that received those feeds were given free access to limestone grit. All groups of chickens laid equally well; and, in thickness and smoothness, the shells of the eggs from any one group were not significantly different from the shells of the eggs from the other groups. It was concluded that it did not matter whether all the calcium is in the feed or part is in the feed and part is in the form of a separate supplement. Much more recently, Petersen et al. (1960) reported on the relative merits of including all the calcium in the feed and of giving chickens free access to a separate calcium supplement when only part of the
Downloaded from http://ps.oxfordjournals.org/ at Carleton University on May 11, 2015
Angelotti, R., E. Wilson, M. J. Foter and K. H. Lewis, 1959. Time-temperature effects on salmonellae and staphylococci in foods. I. Behavior in broth cultures and refrigerated foods. Technical Report F59-2. U. S. Dept. Health, Education and Welfare, Public Health Service. Ayres, J. C , and H. M. Slosberg, 1949. Destruction of Salmonella in egg albumen. Food Technol. 3: 180-183. Banwart, G. J., and J. C. Ayres, 1956. The effect of high temperature storage on the content of Salmonella and on the functional properties of dried egg whites. Food Technol. 10: 68-73. Banwart, G. J., and J. C. Ayres, 1957. The effect of pH on the growth of Salmonella and on the functional properties of liquid egg white. Food Technol. 11:244-246. Goresline, H. E., K. M. Hayes, R. E. Moser, M. A.
Howe and F. E. Drewniak, 1951. Pasteurization of liquid whole egg under commercial conditions to eliminate Salmonella. V. S. Dept. Agr. Cir. 897. Hoskins, J. K., 1934. Most probable numbers for the evaluation of coliaerogenes test by fermentation tube method. U. S. Public Health Reports 49: 385-505. United States Department of Agriculture, 1963. Regulations governing the grading and inspection of egg products. U. S. Public Health Service, 1963. Salmonella surveillance summary. Morbidity and Mortality, 12 (42): 348-349. Wilson, M. E., 1948. Survival of Salmonella organisms in stored egg powder. Food Ind. 20: 873875. Winter, A. R., G. F. Stewart, J. H. McFarlane and M. Solowey, 1946. Pasteurization of liquid egg products. III. Destruction of Salmonella in liquid whole eggs. Am. J. Public Health 36: 451-460.
977
SUPPLYING CALCIUM XO LAYERS
EXPERIMENTAL PROCEDURE The results of two experiments are reported in this paper. Experiment 1 lasted for eleven 28-day periods (308 days). Experiment 2 was started a year later, and it lasted for twelve 28-day periods (336 days). Each experiment was conducted with New Hampshire pullets, just starting to lay; and, in each, the pullets were kept in individual metal cages in an air-conditioned, window-less room. The temperature and relative humidity of the room were
TABLE 1.—Formula of the diet having the lowest level of calcium* Ingredient Ground yellow corn Soybean meal (44% protein) Mono-basic potassium phosphate (KH2PO4)
Salt Riboflavin supplement1' Trace-mineral pre-mix (Delamix)0 Choline chloride, 25% Vitamin D3 supplement"1 Crystalline vitamin A acetate1' Calcium pantothenate Menadione Total
Parts by weight 74.24 22.48 2.06 .52 .46 .10 .078 .058 .00136 .00055 .000045 99.997955
a Estimated to contain 16.7 percent of protein, 0.10 percent of calcium, and 0.83 percent of phosphorus, but actually contained 0.20 percent of calcium. b Contained 227 milligrams riboflavin per pound; supplied 1.044 milligrams per pound of the diet. " Contained 6% manganese, 0.12% iodine, 2% iron, 0.2% copper, 0.02% cobalt, 0.01% zinc. d Contained 1,500 I.C.U. vitamin D3 per gram; supplied 395 I.C.U. per pound of the diet. e Supplied 3,080 I.U. vitamin A per pound of the diet.
maintained at 65 ± 2°F. and 50 ± 5 percent, respectively. The room was lighted 14 consecutive hours of each day. Three, all-mash, corn-soybean meal diets were fed ad libitum. One of the diets contained no calcium supplement. The formula of this diet is given in Table 1. The other two diets were made by adding sufficient calcite flour to the first diet to increase the content of calcium to the desired levels (a presumably adequate level and half of the presumably adequate level). The diets were mixed for each experimental period of 28 days. They were sampled and analyzed for content of protein, calcium, and phosphorus. The three diets contained, respectively, 0.20 ± 0.011, 1.24 ± 0.021, and 2.43 ± 0.045 percent of calcium in Experiment 1 and 0.20 ± 0.010, 1.25 ± 0.012, and 2.47 ± 0.023 percent of calcium in Experiment 2.
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calcium is included in the feed. They fed a mash that contained 2.25 percent of calcium and supplied oyster shell, ad libitum. The hens adjusted their calcium intake to a quantity equal to 3.63 percent of the combined mash and calcium supplement. The quality of the shells of their eggs was about equal to that of the eggs of the other hens that were fed a diet containing 3.0 percent of calcium and not given access to a calcium supplement; it was poorer than that of the eggs of the hens that were fed a diet containing 3.75 percent of calcium. These workers concluded that the chicken will utilize the calcium of its diet more efficiently if all the calcium is included in the feed than if 2.25 percent of calcium is included in the feed and free access is given to a supplement of oyster shell. The problem of how to supply the required calcium is receiving renewed attention with the development of cage systems of layer management. Many poultrymen prefer to include all the calcium in the feed under such systems of management. Will this practice be as satisfactory as the older method of putting a part of the calcium in the feed and giving the chickens free access to a calcium supplement? Experiments were conducted at this laboratory that provide additional information on this problem.
978
A. L. MEHRING, JR.
Experiment 1 was started with 96 pullets; 32 were assigned to each of the three following-described treatments. Experiment 2 was started with 192 pullets, 64 of which were assigned to each of the said three treatments.
Distilled water was provided at all times. Records were kept, for each chicken in each experiment, of egg production, consumption of feed and calcite crystals, gain or loss in live weight, hatchability of fertile eggs, and strength of egg shells. Each fourth egg laid by each chicken was tested for resistance of the shell to breaking in a device described by Mehring (1949), in which device an increasing, measured TABLE 2.—Average <
RESULTS AND DISCUSSION
The average egg production, feed efficiency, strength of egg shells, hatchability of fertile eggs, and gain in live weight of the chickens in Experiments 1 and 2 are given in Tables 2 and 3, respectively. There were no differences (P < .05) in egg production, feed efficiency or hatchability of fertile eggs in either experiment. Even if allowance is made for the calcium supplement that was added to the feed, or for the consumption of calcite crystals as part of the total diet, feed efficiency was not statistically different among treatments. In Experiment 1, the chickens on treatment 1 gained significantly more weight, on the average, than those of treatments 2 or 3 (P < .05). In Experiment 2, however, the gain made by the chickens on treatment
production, feed efficiency, strength of egg shells, hatchability of fertile eggs, i gain in live weight of the chickens in Experiment 1 Feed efficiency"
Treatment
1—0.20% calcium in feed plus free access to calcite crystals
Combination of Strength Feed Feed Egg of egg feed (with production (without (with shells calcium calcium i-cMi-iujui calcium • I • i inclusion) inclusion) ^ c a ' l c i t e crystals Percent
Hatchability of fertile eggs
Gain in live weight
Kilograms
Percent
Grams
65.3
.203
.203
.181
3.62
68.1
658*
2—1.24% calcium in feed plus free access to calcite crystals
62.6
.211
.206
.188
3.65
63.5
474
3—2.43% calcium in feed
59.8
.207
.193
.193
3.53
66.4
460
a
Dozens of eggs produced per pound of feed (with and without calcium inclusion), and per pound of the combination of feed (with calcium inclusion) and calcite crystals. * Significantly different from the result of treatment 2 or 3 (P<.05).
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Treatment 1 consisted of feeding the diet that contained no calcium supplement, and of providing free access to a calcium supplement in the form of calcite crystals. Treatment 2 consisted of feeding the diet that contained the intermediate level of calcium, and of providing free access to calcite crystals. Treatment 3 consisted of feeding the diet that contained the highest level of calcium with no supplement of calcite crystals.
pressure is applied against the egg midway between the ends of the egg, until the shell is broken. The chickens were manually inseminated, and all suitable eggs that were not tested for strength of shell were incubated.
979
SUPPLYING CALCIUM TO LAYERS
1'AELE 3.—Average egg production, feed efficiency, strength of egg shells, hatchabilily of fertile eggs, and gain in live weight of the chickens in Experiment 2 Feed efficiency"
Treatment
Egg production
Percent
Combinat i o n of Strength Feed Feed of egg *eea ieed feed (with shells (without (with ,\ calcium calcium . , . .. inclusion) inclusion) M e d d l e crystals Kilograms
Hatchability of fertile eggs
Gain in live weight
Grams
3.87*
62.2
669
.172
3.81
61.9
740
.173
3.71
65.3
689
53.9
.191
.191
.172
2—1.25% calcium in feed plus free access to calcite crystals
54.5
.191
.185
3—2.47% calcium in feed
52.7
.185
.173
a
Dozens of eggs produced per pound of feed (with and without calcium inclusion), and per pound of the combination of feed (with calcium inclusion) and calcite crystals. * Significantly different from the result of treatment 3 (P<.02).
1 was less, though not significantly so, than the gains made by those on treatments 2 or 3. This diversity of results raises a doubt that the method of supplying the calcium in treatment 1 actually was responsible for the greater gain observed in Experiment 1. In both experiments, the average strength of shells was greater in every instance in which free access to the separate calcium supplement was provided than in the instances in which access to a separate calcium supplement was not provided. The difference between treatments 1 and 3 in Experiment 2 was significant (P < .02). Although the other three differences were not statistically significant, they suggest that the greater consumption of calcium tended to cause an increase in strength of shell. The quantity of calcium that was consumed by the chickens on each of the treatments may be estimated from the quantities of feed and calcite crystals consumed and the quantity of calcium they contained. Such estimates are given in Tables
4 and S. In Experiment 1, the chickens on treatments 1 and 2 consumed almost identical quantities of calcium (3.401 and 3.405 pounds, respectively). These quantities are appreciably larger than the 1.923 pounds consumed by the chickens on treatment 3 (all the calcium in the feed). The quantity of calcium in the combined intake of feed and calcite crystals was estimated to be 3.64, 3.97, and 2.43 percent of the diet, respectively, for the chickens on treatments 1, 2, and 3. A similar situation was observed in Experiment 2, in which the consumption of calcium was 2.844 and 3.036 pounds, respectively, for the chickens on treatments 1 and 2, as compared to 2.112 pounds for the chickens on treatment 3. The corresponding quantities of calcium in the combined intake of feed and calcium supplement were 3.26, 3.43, and 2.47 percent of the diet, respectively. It is apparent from both experiments that in those instances in which the chickens had the opportunity to adjust their consumption of calcium (treatments 1 and
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Percent
1—0.20% calcium in feed plus free acess to calcite crystals
980
A. L. MEHRING, JR. T A B L E 4.—Average consumption
of calcium, from feed and calcium Experiment 1
consumption
:lum content
Calcium consumed
in
consumed
Average consumption
Calcium consumed
Level of calcium intake
Percent
Lbs.
Lbs.
Lbs.
Percent 3.64
Average Calcium sumption content
Calcium
Lbs.
Percent
Lbs.
1—0.20% calcium in feed plus free access to calcite crystals
83.53
0.20
0.167
33.0
3.234
93.33
3.401
2—1.24% calcium in feed plus free access to calcite crystals
78.46
1.24
0.973
33.0
2.432
85.83
3.405
3.97
3—2.43% calcium in feed
79.14
2.43
1.923
79.14
1.923
2.43
a
Lbs.
oj the chickens
Combination of feed & calcite crystals
Calcite crystals
Feed" Treatment
supplement,
As fed.
calculated that their hens at the Idaho Experiment Station consumed sufficient oyster shell to provide a total calcium intake of 2.75 to 4.0 percent (average of 3.63 percent). Gerry (1962) reported that the chickens in two experiments at the Maine Experiment Station adjusted their total calcium intake with calcite grit at 3.75 and 3.40 percent. Johnson (1954) estimated that the Leghorns in four random-sample and four standard egg laying tests (1949— 1953) at Modesto, California, adjusted their total calcium intake with oyster shell to an average level of 2.9 percent. The crosses in the contests adjusted their level of intake at 2.8 percent; and the heavy breeds, at 2.5 percent. The greater strength of shell observed on treatments 1 and 2, in which the chickens had free access to a calcium supplement
TABLE 5.—Average consumption of calcium, from feed and calcium supplement, of the chickens in Experiment 2 Feed a Treatment
Combination of feed & calcite crystals
Calcite crystals
Average consumption
Calcium content
Calcium consumed
Average consumption
Calcium content
Calcium consumed
Average consumption
Calcium consumed
Level of calcium intake
Lbs.
Percent
Lbs.
Lbs.
Percent
Lbs.
Lbs.
Lbs.
Percent
1—0.20% calcium in feed plus free access to calcite crystals
79.07
0.20
0.158
8.14
33.0
2.686
87.21
2.844
3.26
2—1.25% calcium in feed plus free access to calcite crystals
82.42
1.25
1.030
6.08
33.0
2.006
88.50
3.036
3.43
3—2.47% calcium in feed
85.51
2.47
2.112
-
-
-
85'. 51
2.112
2.47
As fed.
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2), they consumed more calcium than was provided in the diet that contained the presumably adequate level (treatment 3). It is evident, also, that the total consumption of calcium was almost the same on treatment 1 and 2, despite the fact that those on treatment 1 received no calcium supplements in the feed and those on treatment 2 received half of a presumably adequate level of calcium in the feed. It is worth noting that the total calcium intake of the chickens on treatments 1 and 2 agrees reasonably well with that reported by other workers who gave laying chickens free access to a calcium supplement; and, further, that the total calcium intake tended to be in excess of the calcium requirement (2.75 percent) currently suggested by the National Research Council (1962). Petersen et al. (1960)
SUPPLYING CALCIUM TO LAYERS
981
strength of shells in those instances in which access to a separate calcium supplement was provided. This effect was no doubt due to the considerably greater consumption of total calcium by these chickens. It was concluded that if laying chickens in good production are given free access to a calcium supplement, such as calcite crystals, they will consume enough calcium to meet their needs even if no calcium supplement is included in their feed; that they will adjust their calcium intake to a higher level than that currently recommended (2.75 percent) by the National Research Council; and that they will tend to produce shells of greater strength if they are permitted to adjust their calcium intake. It appears that the three methods of supplying calcium (all in the feed, part in the feed and part as a supplement, and practically none in the feed and nearly all as a supplement) are equally satisfactory.
SUMMARY Comparisons were made between laying New Hampshire chickens that received all of their calcium in the feed (2.45 percent), part in the feed (1.25 percent) and part in the form of a calcium supplement (calcite crystals), and as little as possible in the feed (0.20 percent) and practically all in the form of the calcium supplement. Two consecutive experiments, each lasting nearly a year, were conducted. Thirtytwo chickens were assigned to each of the three methods of supplying calcium, in the first experiment; and 64, to each of the three methods, in the second experiment. The chickens were kept in individual cages in an air-conditioned room. No real differences in egg production, efficiency of feed utilization, or hatchability were observed in either experiment. A tendency was observed, however, for greater
ACKNOWLEDGMENT Analytical work on the diets was performed by Loyd L. Nesbitt of the Lime Crest Research Laboratory. REFERENCES Berg, L. R., G. E. Bearse and V. L. Miller, 1944. A comparison of two methods of supplying calcium to laying pullets. Washington Agr. Exp. Sta. Bui. 458. Gerry, R. W., 1962. Can the laying hen adjust her own calcium level? Maine Farm Research, 10: 12-14. Johnson, E. A., 1954. Protein and calcium intake on a free-choice diet. Poultry Sci. 33: 1063. Mehring, A. L., Jr., 1949. A device for measuring the strength of shells of eggs. Poultry Sci. 28: 621— 622. National Research Council, 1962. Supplement to Nutrient requirements for domestic animals. No. 1. Nutrient requirements for poultry, 1960. Petersen, C. F., D. H. Conrad, D. H. Lumijarvi, E. A. Sauter and C. E. Lampman, 1960. Studies on the calcium requirements of high producing white leghorn hens. Idaho Agr. Exp. Sta. Bui. 44.
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and in which the total calcium intake was greater than that observed on treatment 3, led us, at this laboratory, to believe that the presumably adequate levels of 2.43 and 2.47 percent of calcium are, in reality, not adequate. The experiments reported in this paper suggest that the three methods of supplying calcium to the laying chicken (all in the feed, part in the feed and part as a supplement, and practically none in the feed and nearly all as a supplement) are equally satisfactory. The chief difference noted as a result of differences in the method of supplying calcium was in strength of shell. It appeared to be greater in those instances in which the chickens had free access to the calcium supplement than in those instances in which all the calcium was in the feed. This difference can be attributed, no doubt, to the appreciably greater total consumption of calcium by the chickens that had free access to the separate calcium supplement.
G. J. BANWART REFERENCES
A Comparison of Three Methods of Supplying Calcium in the Diet of Laying Chickens ARNON L. MEHRING, JR. Lime Crest Research Laboratory, Limestone Products Corporation of America, Newton, New Jersey (Received for publication January 30, 1964)
F
OR many years it has been the practice to include in the feed of laying chickens only a part of the calcium needed for egg production, and to give the chickens free access to a calcium supplement. It was believed that the chickens would consume enough additional calcium to fully meet their needs. Oddly enough, there is but little experimental evidence on record to support that belief. Berg et al. (1944) reported the results of a comparison of two methods of supplying calcium to laying pullets, that of putting the full allowance in the feed, and that of putting a part of it in the feed and giving the pullets free access to limestone grit. The feed that supplied the full allowance contained 3.08 percent of calcium.
Three other feeds contained, respectively, 0.926, 1.875, and 2.727 percent of calcium; and the chickens that received those feeds were given free access to limestone grit. All groups of chickens laid equally well; and, in thickness and smoothness, the shells of the eggs from any one group were not significantly different from the shells of the eggs from the other groups. It was concluded that it did not matter whether all the calcium is in the feed or part is in the feed and part is in the form of a separate supplement. Much more recently, Petersen et al. (1960) reported on the relative merits of including all the calcium in the feed and of giving chickens free access to a separate calcium supplement when only part of the
Downloaded from http://ps.oxfordjournals.org/ at Carleton University on May 11, 2015
Angelotti, R., E. Wilson, M. J. Foter and K. H. Lewis, 1959. Time-temperature effects on salmonellae and staphylococci in foods. I. Behavior in broth cultures and refrigerated foods. Technical Report F59-2. U. S. Dept. Health, Education and Welfare, Public Health Service. Ayres, J. C , and H. M. Slosberg, 1949. Destruction of Salmonella in egg albumen. Food Technol. 3: 180-183. Banwart, G. J., and J. C. Ayres, 1956. The effect of high temperature storage on the content of Salmonella and on the functional properties of dried egg whites. Food Technol. 10: 68-73. Banwart, G. J., and J. C. Ayres, 1957. The effect of pH on the growth of Salmonella and on the functional properties of liquid egg white. Food Technol. 11:244-246. Goresline, H. E., K. M. Hayes, R. E. Moser, M. A.
Howe and F. E. Drewniak, 1951. Pasteurization of liquid whole egg under commercial conditions to eliminate Salmonella. V. S. Dept. Agr. Cir. 897. Hoskins, J. K., 1934. Most probable numbers for the evaluation of coliaerogenes test by fermentation tube method. U. S. Public Health Reports 49: 385-505. United States Department of Agriculture, 1963. Regulations governing the grading and inspection of egg products. U. S. Public Health Service, 1963. Salmonella surveillance summary. Morbidity and Mortality, 12 (42): 348-349. Wilson, M. E., 1948. Survival of Salmonella organisms in stored egg powder. Food Ind. 20: 873875. Winter, A. R., G. F. Stewart, J. H. McFarlane and M. Solowey, 1946. Pasteurization of liquid egg products. III. Destruction of Salmonella in liquid whole eggs. Am. J. Public Health 36: 451-460.
977
SUPPLYING CALCIUM XO LAYERS
EXPERIMENTAL PROCEDURE The results of two experiments are reported in this paper. Experiment 1 lasted for eleven 28-day periods (308 days). Experiment 2 was started a year later, and it lasted for twelve 28-day periods (336 days). Each experiment was conducted with New Hampshire pullets, just starting to lay; and, in each, the pullets were kept in individual metal cages in an air-conditioned, window-less room. The temperature and relative humidity of the room were
TABLE 1.—Formula of the diet having the lowest level of calcium* Ingredient Ground yellow corn Soybean meal (44% protein) Mono-basic potassium phosphate (KH2PO4)
Salt Riboflavin supplement1' Trace-mineral pre-mix (Delamix)0 Choline chloride, 25% Vitamin D3 supplement"1 Crystalline vitamin A acetate1' Calcium pantothenate Menadione Total
Parts by weight 74.24 22.48 2.06 .52 .46 .10 .078 .058 .00136 .00055 .000045 99.997955
a Estimated to contain 16.7 percent of protein, 0.10 percent of calcium, and 0.83 percent of phosphorus, but actually contained 0.20 percent of calcium. b Contained 227 milligrams riboflavin per pound; supplied 1.044 milligrams per pound of the diet. " Contained 6% manganese, 0.12% iodine, 2% iron, 0.2% copper, 0.02% cobalt, 0.01% zinc. d Contained 1,500 I.C.U. vitamin D3 per gram; supplied 395 I.C.U. per pound of the diet. e Supplied 3,080 I.U. vitamin A per pound of the diet.
maintained at 65 ± 2°F. and 50 ± 5 percent, respectively. The room was lighted 14 consecutive hours of each day. Three, all-mash, corn-soybean meal diets were fed ad libitum. One of the diets contained no calcium supplement. The formula of this diet is given in Table 1. The other two diets were made by adding sufficient calcite flour to the first diet to increase the content of calcium to the desired levels (a presumably adequate level and half of the presumably adequate level). The diets were mixed for each experimental period of 28 days. They were sampled and analyzed for content of protein, calcium, and phosphorus. The three diets contained, respectively, 0.20 ± 0.011, 1.24 ± 0.021, and 2.43 ± 0.045 percent of calcium in Experiment 1 and 0.20 ± 0.010, 1.25 ± 0.012, and 2.47 ± 0.023 percent of calcium in Experiment 2.
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calcium is included in the feed. They fed a mash that contained 2.25 percent of calcium and supplied oyster shell, ad libitum. The hens adjusted their calcium intake to a quantity equal to 3.63 percent of the combined mash and calcium supplement. The quality of the shells of their eggs was about equal to that of the eggs of the other hens that were fed a diet containing 3.0 percent of calcium and not given access to a calcium supplement; it was poorer than that of the eggs of the hens that were fed a diet containing 3.75 percent of calcium. These workers concluded that the chicken will utilize the calcium of its diet more efficiently if all the calcium is included in the feed than if 2.25 percent of calcium is included in the feed and free access is given to a supplement of oyster shell. The problem of how to supply the required calcium is receiving renewed attention with the development of cage systems of layer management. Many poultrymen prefer to include all the calcium in the feed under such systems of management. Will this practice be as satisfactory as the older method of putting a part of the calcium in the feed and giving the chickens free access to a calcium supplement? Experiments were conducted at this laboratory that provide additional information on this problem.
978
A. L. MEHRING, JR.
Experiment 1 was started with 96 pullets; 32 were assigned to each of the three following-described treatments. Experiment 2 was started with 192 pullets, 64 of which were assigned to each of the said three treatments.
Distilled water was provided at all times. Records were kept, for each chicken in each experiment, of egg production, consumption of feed and calcite crystals, gain or loss in live weight, hatchability of fertile eggs, and strength of egg shells. Each fourth egg laid by each chicken was tested for resistance of the shell to breaking in a device described by Mehring (1949), in which device an increasing, measured TABLE 2.—Average <
RESULTS AND DISCUSSION
The average egg production, feed efficiency, strength of egg shells, hatchability of fertile eggs, and gain in live weight of the chickens in Experiments 1 and 2 are given in Tables 2 and 3, respectively. There were no differences (P < .05) in egg production, feed efficiency or hatchability of fertile eggs in either experiment. Even if allowance is made for the calcium supplement that was added to the feed, or for the consumption of calcite crystals as part of the total diet, feed efficiency was not statistically different among treatments. In Experiment 1, the chickens on treatment 1 gained significantly more weight, on the average, than those of treatments 2 or 3 (P < .05). In Experiment 2, however, the gain made by the chickens on treatment
production, feed efficiency, strength of egg shells, hatchability of fertile eggs, i gain in live weight of the chickens in Experiment 1 Feed efficiency"
Treatment
1—0.20% calcium in feed plus free access to calcite crystals
Combination of Strength Feed Feed Egg of egg feed (with production (without (with shells calcium calcium i-cMi-iujui calcium • I • i inclusion) inclusion) ^ c a ' l c i t e crystals Percent
Hatchability of fertile eggs
Gain in live weight
Kilograms
Percent
Grams
65.3
.203
.203
.181
3.62
68.1
658*
2—1.24% calcium in feed plus free access to calcite crystals
62.6
.211
.206
.188
3.65
63.5
474
3—2.43% calcium in feed
59.8
.207
.193
.193
3.53
66.4
460
a
Dozens of eggs produced per pound of feed (with and without calcium inclusion), and per pound of the combination of feed (with calcium inclusion) and calcite crystals. * Significantly different from the result of treatment 2 or 3 (P<.05).
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Treatment 1 consisted of feeding the diet that contained no calcium supplement, and of providing free access to a calcium supplement in the form of calcite crystals. Treatment 2 consisted of feeding the diet that contained the intermediate level of calcium, and of providing free access to calcite crystals. Treatment 3 consisted of feeding the diet that contained the highest level of calcium with no supplement of calcite crystals.
pressure is applied against the egg midway between the ends of the egg, until the shell is broken. The chickens were manually inseminated, and all suitable eggs that were not tested for strength of shell were incubated.
979
SUPPLYING CALCIUM TO LAYERS
1'AELE 3.—Average egg production, feed efficiency, strength of egg shells, hatchabilily of fertile eggs, and gain in live weight of the chickens in Experiment 2 Feed efficiency"
Treatment
Egg production
Percent
Combinat i o n of Strength Feed Feed of egg *eea ieed feed (with shells (without (with ,\ calcium calcium . , . .. inclusion) inclusion) M e d d l e crystals Kilograms
Hatchability of fertile eggs
Gain in live weight
Grams
3.87*
62.2
669
.172
3.81
61.9
740
.173
3.71
65.3
689
53.9
.191
.191
.172
2—1.25% calcium in feed plus free access to calcite crystals
54.5
.191
.185
3—2.47% calcium in feed
52.7
.185
.173
a
Dozens of eggs produced per pound of feed (with and without calcium inclusion), and per pound of the combination of feed (with calcium inclusion) and calcite crystals. * Significantly different from the result of treatment 3 (P<.02).
1 was less, though not significantly so, than the gains made by those on treatments 2 or 3. This diversity of results raises a doubt that the method of supplying the calcium in treatment 1 actually was responsible for the greater gain observed in Experiment 1. In both experiments, the average strength of shells was greater in every instance in which free access to the separate calcium supplement was provided than in the instances in which access to a separate calcium supplement was not provided. The difference between treatments 1 and 3 in Experiment 2 was significant (P < .02). Although the other three differences were not statistically significant, they suggest that the greater consumption of calcium tended to cause an increase in strength of shell. The quantity of calcium that was consumed by the chickens on each of the treatments may be estimated from the quantities of feed and calcite crystals consumed and the quantity of calcium they contained. Such estimates are given in Tables
4 and S. In Experiment 1, the chickens on treatments 1 and 2 consumed almost identical quantities of calcium (3.401 and 3.405 pounds, respectively). These quantities are appreciably larger than the 1.923 pounds consumed by the chickens on treatment 3 (all the calcium in the feed). The quantity of calcium in the combined intake of feed and calcite crystals was estimated to be 3.64, 3.97, and 2.43 percent of the diet, respectively, for the chickens on treatments 1, 2, and 3. A similar situation was observed in Experiment 2, in which the consumption of calcium was 2.844 and 3.036 pounds, respectively, for the chickens on treatments 1 and 2, as compared to 2.112 pounds for the chickens on treatment 3. The corresponding quantities of calcium in the combined intake of feed and calcium supplement were 3.26, 3.43, and 2.47 percent of the diet, respectively. It is apparent from both experiments that in those instances in which the chickens had the opportunity to adjust their consumption of calcium (treatments 1 and
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Percent
1—0.20% calcium in feed plus free acess to calcite crystals
980
A. L. MEHRING, JR. T A B L E 4.—Average consumption
of calcium, from feed and calcium Experiment 1
consumption
:lum content
Calcium consumed
in
consumed
Average consumption
Calcium consumed
Level of calcium intake
Percent
Lbs.
Lbs.
Lbs.
Percent 3.64
Average Calcium sumption content
Calcium
Lbs.
Percent
Lbs.
1—0.20% calcium in feed plus free access to calcite crystals
83.53
0.20
0.167
33.0
3.234
93.33
3.401
2—1.24% calcium in feed plus free access to calcite crystals
78.46
1.24
0.973
33.0
2.432
85.83
3.405
3.97
3—2.43% calcium in feed
79.14
2.43
1.923
79.14
1.923
2.43
a
Lbs.
oj the chickens
Combination of feed & calcite crystals
Calcite crystals
Feed" Treatment
supplement,
As fed.
calculated that their hens at the Idaho Experiment Station consumed sufficient oyster shell to provide a total calcium intake of 2.75 to 4.0 percent (average of 3.63 percent). Gerry (1962) reported that the chickens in two experiments at the Maine Experiment Station adjusted their total calcium intake with calcite grit at 3.75 and 3.40 percent. Johnson (1954) estimated that the Leghorns in four random-sample and four standard egg laying tests (1949— 1953) at Modesto, California, adjusted their total calcium intake with oyster shell to an average level of 2.9 percent. The crosses in the contests adjusted their level of intake at 2.8 percent; and the heavy breeds, at 2.5 percent. The greater strength of shell observed on treatments 1 and 2, in which the chickens had free access to a calcium supplement
TABLE 5.—Average consumption of calcium, from feed and calcium supplement, of the chickens in Experiment 2 Feed a Treatment
Combination of feed & calcite crystals
Calcite crystals
Average consumption
Calcium content
Calcium consumed
Average consumption
Calcium content
Calcium consumed
Average consumption
Calcium consumed
Level of calcium intake
Lbs.
Percent
Lbs.
Lbs.
Percent
Lbs.
Lbs.
Lbs.
Percent
1—0.20% calcium in feed plus free access to calcite crystals
79.07
0.20
0.158
8.14
33.0
2.686
87.21
2.844
3.26
2—1.25% calcium in feed plus free access to calcite crystals
82.42
1.25
1.030
6.08
33.0
2.006
88.50
3.036
3.43
3—2.47% calcium in feed
85.51
2.47
2.112
-
-
-
85'. 51
2.112
2.47
As fed.
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2), they consumed more calcium than was provided in the diet that contained the presumably adequate level (treatment 3). It is evident, also, that the total consumption of calcium was almost the same on treatment 1 and 2, despite the fact that those on treatment 1 received no calcium supplements in the feed and those on treatment 2 received half of a presumably adequate level of calcium in the feed. It is worth noting that the total calcium intake of the chickens on treatments 1 and 2 agrees reasonably well with that reported by other workers who gave laying chickens free access to a calcium supplement; and, further, that the total calcium intake tended to be in excess of the calcium requirement (2.75 percent) currently suggested by the National Research Council (1962). Petersen et al. (1960)
SUPPLYING CALCIUM TO LAYERS
981
strength of shells in those instances in which access to a separate calcium supplement was provided. This effect was no doubt due to the considerably greater consumption of total calcium by these chickens. It was concluded that if laying chickens in good production are given free access to a calcium supplement, such as calcite crystals, they will consume enough calcium to meet their needs even if no calcium supplement is included in their feed; that they will adjust their calcium intake to a higher level than that currently recommended (2.75 percent) by the National Research Council; and that they will tend to produce shells of greater strength if they are permitted to adjust their calcium intake. It appears that the three methods of supplying calcium (all in the feed, part in the feed and part as a supplement, and practically none in the feed and nearly all as a supplement) are equally satisfactory.
SUMMARY Comparisons were made between laying New Hampshire chickens that received all of their calcium in the feed (2.45 percent), part in the feed (1.25 percent) and part in the form of a calcium supplement (calcite crystals), and as little as possible in the feed (0.20 percent) and practically all in the form of the calcium supplement. Two consecutive experiments, each lasting nearly a year, were conducted. Thirtytwo chickens were assigned to each of the three methods of supplying calcium, in the first experiment; and 64, to each of the three methods, in the second experiment. The chickens were kept in individual cages in an air-conditioned room. No real differences in egg production, efficiency of feed utilization, or hatchability were observed in either experiment. A tendency was observed, however, for greater
ACKNOWLEDGMENT Analytical work on the diets was performed by Loyd L. Nesbitt of the Lime Crest Research Laboratory. REFERENCES Berg, L. R., G. E. Bearse and V. L. Miller, 1944. A comparison of two methods of supplying calcium to laying pullets. Washington Agr. Exp. Sta. Bui. 458. Gerry, R. W., 1962. Can the laying hen adjust her own calcium level? Maine Farm Research, 10: 12-14. Johnson, E. A., 1954. Protein and calcium intake on a free-choice diet. Poultry Sci. 33: 1063. Mehring, A. L., Jr., 1949. A device for measuring the strength of shells of eggs. Poultry Sci. 28: 621— 622. National Research Council, 1962. Supplement to Nutrient requirements for domestic animals. No. 1. Nutrient requirements for poultry, 1960. Petersen, C. F., D. H. Conrad, D. H. Lumijarvi, E. A. Sauter and C. E. Lampman, 1960. Studies on the calcium requirements of high producing white leghorn hens. Idaho Agr. Exp. Sta. Bui. 44.
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and in which the total calcium intake was greater than that observed on treatment 3, led us, at this laboratory, to believe that the presumably adequate levels of 2.43 and 2.47 percent of calcium are, in reality, not adequate. The experiments reported in this paper suggest that the three methods of supplying calcium to the laying chicken (all in the feed, part in the feed and part as a supplement, and practically none in the feed and nearly all as a supplement) are equally satisfactory. The chief difference noted as a result of differences in the method of supplying calcium was in strength of shell. It appeared to be greater in those instances in which the chickens had free access to the calcium supplement than in those instances in which all the calcium was in the feed. This difference can be attributed, no doubt, to the appreciably greater total consumption of calcium by the chickens that had free access to the separate calcium supplement.