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The Value of Grit for Chickens and Turkeys
276
E. C. STTJTTS, W. E. BRILES AND H. 0. KTJNKEL Stutts, E. C , W. Johnson, W. E. Briles and H. O. Kunkel. 1956a. Variation in reduced glutathione in bloods of inbred lines of chickens. Proc. Soc. Exp. Biol. Med. 91:60-63. Stutts, E. C , W. E. Briles and H. O. Kunkel, 1956b. Blood glutathione levels and egg production in inbred lines of chickens. Poultry Sci. 35: 727-728. Tuba, J., and N. B. Madsen, 1952. The relationship of dietary factors of rat serum alkaline phosphatase. IT. The effect of total food consumption, methionine, choline and vitamin B12 in normal and alloxan diabetic adult rats. Canadian J. Med. Sci. 30: 18-25. Wiese, A. C , B. C. Johnson, C. A. Elvehjem, E. B. Hart and J. G. Halpin, 1939. A study of blood and bone phosphatase in chick perosis. J. Biol. Chem. 127: 411-420.
The Value of Grit for Chickens and Turkeys M. L. SCOTT AND G. F. HEUSER Department of Poultry Husbandry, Cornell University, Ithaca, New York (Received for publication September 4, 1956)
chickens and turkeys are not SINCE equipped with teeth, the gizzard must take over the function of reducing the size of the coarse particles of food so that it can be acted upon efficiently by the enzymes concerned in digestion and assimilation. This grinding process is aided considerably by furnishing the birds with a hard, insoluble grit which, upon being consumed by the chicken or turkey, passes to the gizzard and remains there for a considerable period of time (Kaupp and Ivey, 1923), passing on through the remainder of the digestive tract only after it has been reduced by the grinding process to a size no longer capable of aiding in the attrition of the coarse particles of food. Upon finding that the gizzards of hens fed crushed limestone or crushed oyster shell contained approximately the same amounts of mineral material as hens fed granite grit, Waite (1935) concluded that
crushed limestone and crushed oyster shell are capable of serving in the dual capacity of calcium supplement and grinding grit for laying hens. Numerous research studies have been conducted which show that supplementary calcium is not only advisable but absolutely necessary for hens receiving both mash and grain. Less is known concerning the need for free-choice supplementation of chicken and turkey mash-and-grain growing rations with calcium in the form of crushed limestone or oyster shell. The question arises, therefore, as to the ability of chickens and turkeys to maintain sufficient grit in the gizzard for grinding purposes without consuming excesses of calcium when crushed limestone or oyster shell is the only form of grit supplied. Also, because of the inherently soft nature of crushed limestone and oyster shells and the fact that these materials readily dissolve in acid solution, such as
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between plasma phosphatase and phosphatase of bone, kidney, liver and intestinal mucosa. Biochem. J. 47: 193-196. Peterson, W. J., and D. B. Parrish, 1939a. Fluctuations of phosphatase and inorganic phosphorus in the blood of the laying hen during the period of egg formation. Poultry Sci. 18: 54-58. Peterson, W. J., and D. B. Parrish, 1939b. Phosphatase and inorganic phosphorus in the plasma and whole blood of the fowl. Poultry Sci. 18: 59-62. Snedecor, G. W., 1946. Statistical Methods. 4th Edition, Iowa State College Press. Ames. Squibb, R. L., M. A. Guzman and N. S. Scrimshaw, 1954. Effect of high environmental temperatures on metabolism. I. Growth and blood constituents of rats exposed to 94°F. for 72 hours. J. Nutrition, 52: 155-163.
GRIT FOR CHICKENS AND TURKEYS
The studies to be presented in this report were undertaken with broilers, growing turkeys and laying hens, using calcium carbonate grits (calcite and crushed oyster shells) and two kinds of insoluble grit (granite and feldspar) singly and in vari-
ous combinations, to determine (1) which grit or combination of grits is most effective in producing increased growth, egg production and efficiency of feed utilization, and (2) whether or not chickens and turkeys tend to over-eat calcium grit or insoluble grit when these are supplied singly as compared to when they are supplied together. PROCEDURE AND RESULTS
Studies with broilers. For the broiler study, ten lots of Vantress pullet chicks, 20 chicks per lot, were used. All lots received a commercial chick starter ration as the only feed for the first three weeks. This ration contained, by analysis, 1.1% calcium and 0.9% phosphorus. At the end of three weeks, all lots except Lot #8 were given access to scratch grains (cracked corn and cracked wheat) on a free-choice basis. At the same time, certain lots were given access to the various kinds of grit as shown in Table 1. Chicksize scratch grains and grits were used until the birds were eight weeks of age, whereupon intermediate-sized scratch grains and grits were fed until the conclusion of the experiment which was conducted until the birds were 12 weeks of age. The results of the experiment, also presented in Table 1, show that the feeding of the insoluble grits (Lots 2, 3, 5, 6, 7) produced decidedly better growth and efficiency of feed utilization than were obtained with the lots (#1 or #4) which received the mash and grain ration without grit or with calcite grit, respectively. When insoluble grit was supplied together with calcite grit, the consumption of the latter was reduced to about one-third the amount consumed when calcite grit was supplied alone, indicating, in confirmation of the work of Heuser and Norris (1946a) that when the calcite grit alone was available, the birds tended to over-eat the cal-
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that present in the proventriculus and gizzard, it appears possible that these materials may lack the hardness to aid in crushing hard kernels of corn and wheat, whereupon the chicken or turkey may over-eat these materials in an effort to obtain sufficient hard grit for proper functioning of the gizzard. On the other hand, when insoluble grit is fed in the absence of supplementary calcium, it is possible that growing chickens, turkeys and laying hens may over-eat the insoluble grit in an effort to obtain calcium to balance the diet with respect to this mineral nutrient (Buckner and Martin, 1922). Heuser and Norris (1946a) showed that the feeding of free-choice calcium grit tended to cause decreased weight gains in chicks receiving a complete starting ration to eight weeks of age, unless an insoluble grit (granite) was supplied free-choice also. These experiments showed that the young chicks consumed more calcium grit when it was the only form of grit supplied than they consumed when granite and calcium grit were both available for choice. These results were in agreement with those of Cooney (1941) and Ferber and Briiggemann (1933) who reported less favorable results with broilers fed calcium grits than with those fed insoluble grits. Combs, Romoser and Nicholson (1954) concluded from studies with broilers raised under practical conditions that the use of granite grit was economically sound (as judged by the increased growth and improvement in feed utilization) when the broilers were fed free-choice mash and cracked corn but was not necessary when the broilers were reared on complete, allmash rations.
277
278
M. L. SCOTT AND G. F. HEUSER TABLE 1.—Effects
of different kinds of grit upon weight gains, feed conversion, and grain intake in Vantress pullet chicks to twelve weeks of age
Treatment
Feed consumption /Chick
Efficiency of feed utilization
Mash
Scratch
lbs.
lbs.
lbs.
lbs. feed/ lb. gain
3.39 3.62 3.69 3.44
8.96 8.09 8.27 8.05
1.86 2.90 3.18 3.03
3.23 3.14 3.19 3.34
3.69
8.00
3.15
3.18
3.89
8.55
3.22
3.55
8.07
2.50
3.55
11.03
—
Grit consumption/Chick Granite*
sparf
cite|
lbs.
lbs.
lbs.
— —
— — —
—
0.33
— —
0.37
—
0.18
0.30
—
0.08
3.15
—
0.22
0.07
3.16
0.09
0.23
0.06
3.20
—
—
—
* Gray granite, Stone Mountain Grit Co., Lithonia, Ga. f White feldspar, International Minerals and Chemical Corp., Chicago, 111. Sample of feldspar use 1 was a composite of samples from Maine, South Dakota and Arizona. \ Limecrest calcite, Limestone Products Corp. of America, Newton, N. J.
cite grit in an effort to obtain hard particles to aid the gizzard in grinding the scratch grains. Adequacy of the diet in calcium is substantiated by the low calcite intake of all lots which received both calcite and an insoluble grit. No appreciable differences in consumption of insoluble grit occurred either in the presence or absence of calcite grit. Granite and feldspar grits were consumed equally well when fed singly, but the chicks appeared to prefer feldspar grit to granite grit when given the opportunity to choose between them. In every instance the feeding of grit, including calcite grit, was accompanied by an increased consumption of scratch grains and a decreased consumption of mash as compared with the basal lot receiving mash and grains but no grit. The fact that scratch grains cost less than mash accentuated the economic advantage obtained by the increased efficiency of feed utilization when insoluble grit was fed. Studies with growing turkeys. For the turkey study, 96 White Holland torn tur-
keys were raised to twelve weeks of age on an all-mash regime. All turkeys received a 28% protein commercial turkey starting ration (containing, by analysis, 1.8% calcium and 0.9% phosphorus) for the first eight weeks. From 8 to 12 weeks of age, they received a 20% protein commercial turkey growing ration (containing, by analysis, 2.5% calcium and 1.2% phosphorus). When the turkeys were twelve weeks of age, they were divided into eight lots of equivalent average weight and housed in rearing pens with one-inch wire mesh floors. Seven lots were given the growing mash and coarse scratch grains on a free-choice basis. Six of the lots received granite, feldspar or calcite grit, either alone or in various combinations, while one lot received the mash and grain without grit. The eighth lot received the mash alone, without grain or grit. The plan of the experiment is presented in Table 2. The experiment was continued until the turkeys were 20 weeks of age. The effects of the different kinds of grit upon weight gains, feed conversion
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1. Mash and grain, ad lib. (no grit) As (1) and granite grit As (1) and feldspar grit As (1) and calcite grit As (1) and granite and calcite grit 6. As (1) and feldspar and calcite grit 7. As (1) and granite, feldspar and calcite grits 8. All-mash, no grain nor grit
2. 3. 4. 5.
Avg. wt., 12 wks.
GRIT FOR CHICKENS AND TURKEYS
TABLE 2.—Effects
TABLE 3.—Lower bone-ash values in turkeys receiving mash-and-grain rations as compared to turkeys receiving similar rations plus supplementary calcium grit Avg. wt. 20 wks.
Treatment
lbs. Growing mash and scratch grains (no calcite grit) 12. 5 t Growing mash and scratch grains with calcite grit, free-choice 15.8
Bone ash* % 55.2 59.9
* Average of three turkeys per treatment. f These turkeys weighed less than the average for the corresponding lots because they were suffering from the enlarged hock disorder.
keys showing enlarged hocks in the present study and some of the normal turkeys which received calcite grit showed that calcification in the turkeys suffering from enlarged hocks was inferior to that of the turkeys receiving calcite grit (Table 3). Studies with laying hens. When the pullets used in the broiler study presented in the first experiment became 18 weeks of age, they were housed in four similar laying houses on litter, and fed a commercial laying ration, scratch grains and crushed oyster shell, free-choice, with and without free-choice access to granite grit and feldspar grit (hen-size), singly and in
of different hinds of grit upon weight gains, feed conversion, grain intake and enlarged hock disorder in White Holland turkeys between 12 and 20 weeks of age
Treatment
Avg. gam, 10-20 wks.
Mash
1. Mash and grain, ad lib. (no grit) 2. As (1) and granite grit 3. As (1) and feldspar grit 4. As (1) and calcite grit 5. As (1) and granite and calcite grits 6. As (1) and feldspar and calcite grits 7. As (1) and granite, feldspar and calcite grits 8. All-mash, no grain nor grit
Grit consumption/Turkey Incidence Efficiency enlarged 12-20 wks. of feed hock utilization CalFelddisorder, 12-20 wks. Gran20 wks. ite spar cite Scratch
Feed consumption/Turkey, 12-20 wks.
lbs.
lbs.
lbs.
lbs. feed/ lb. gain
7.8 8.4 8.5 7.9
25.8 25.2 26.6 26.7
7.2 7.2 5.5 7.1
4.23 3.85 3.78 4.28
8.4
24.6
8.1
8.5
23.0
8.2 7.0
lbs.
lbs.
lbs.
—
— —
— — —
%
— —
5.7
—
1.6
25 17 8 0
3.89
4.2
—
2.6
0
10.2
3.90
—
5.6
2.6
0
23.1
7.1
3.70
3.3
4.6
1.0
0
28.4
—
4.06
•—
—
—
0
6.0
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and the enlarged hock disorder are also presented in Table 2. The results of the experiment agree with those obtained with the chickens in showing that insoluble grit is necessary for maximum growth and efficiency of feed utilization when scratch grains are fed. The turkeys receiving insoluble grit gained appreciably more on approximately the same feed intake as compared with the basal lot or the lot receiving only calcite grit. The lot which received the mash without grain grew at a slower rate than any of the lots receiving grain. This was probably due to the relatively high protein and low energy intake of this lot as compared with those having the opportunity to balance their intake of energy through the consumption of grain. The calcite intake by the turkeys was variable and much higher than the calcite intake of the chickens in the previous study. Furthermore, some cases of enlarged hock disorder were observed in all lots receiving grain but no calcite, but no hock trouble occurred in the comparable lots receiving supplemental calcium. Bone ash analyses conducted on the fat-free, moisture-free tibia of some of the tur-
279
280
M. L. SCOTT AND G. F. HEUSER TABLE 4.—Effect
of insoluble grit upon egg production and efficiency of feed utilization in Vantress hens over a twelve-week period of production
Treatments
Avg. wt. of hens
Mortality
lbs.
%
%
hen/ 12 wks.
Grit consumption/Hen, 12-wk. period
Emciency
Mash
Grain
Oyster shell
Granite
Feldspar
lbs.
lbs.
lbs.
lbs.
lbs.
0.20
— -—
6.2
lbs. feed/ doz. eggs
6.35
12.1
34.4
40.9
9.21
11.70
0.57
6.43
14.3
43.7
52.0
11.73
10.86
0.52
6.54
6.9
44.0
52.4
12.30
10.81
0.60
0.32
6.3
6.52
5.6
47.5
56.5
12.90
10.44
0.70
0.28
5.9
combination. The mash contained 2.06% calcium and 1.56% phosphorus. The pullets used for the lot which received no insoluble grit were those which had received the basal ration or the basal ration plus calcite grit during the broiler study. Similarly, the pullets which received either granite grit or feldspar grit or the combination of these grits were those which had received the corresponding grit treatments during the starting and growing periods. Each lot contained 40 pullets. The experiment was started after the first month of egg production and was conducted for the succeeding 12-week period. The experimental plan and results are presented in Table 4. The first month of production TABLE 5.—Effect
Feed consumption/ Hen, 12-wk. period
7.3
was omitted from consideration in Table 4 because the hens receiving no insoluble grit (Lot 1) and those receiving only granite grit (Lot 2) were much slower in coming into production than were the two lots which received feldspar grit. The results show that the feeding of insoluble grit was effective in improving egg production and efficiency of feed utilization as compared with that obtained with the lot receiving the laying mash and scratch grains with crushed oyster shells as the only source of grit. The presence of whole grain (wheat) in the gizzards of fasted hens which had received mash, grain and oyster shell as the only form of grit (Table 5) provides further evidence
of ration and grit upon gizzard weights in growing and laying chickens Content of gizzard*
Treatment
Age
Gizzard wt. Grit
Whole
grains
wks.
gms.
%of body wt.
gms.
Pre-laying period: All-mash ration (no grain nor grit) Mash+grain(no grit) Mash-j-grain+feldspar grit
12 12 12
47.8 50.6 52.9
2.12 2.20 2.24
0 0 17.4
Laying period: Mash+grains+oyster Mash+grains+oyster Mash+grains+oyster Mash+grains+oyster +feldspar grit
36 36 36
52.6 51.2 51.6
1.59 1.57 1.66
3 16.6 15.6
+
36
52.4
1.64
13.4
0
shell shell+granite grit shell+feldspai• grit shell+granite grit
* Birds were fasted 16 hours before slaughter.
0
+ 0
0 0
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1. Laying mash+whole grains (corn & wheat 50:50) -{-oyster shell (free-choice) 2. As (1) -f-granite grit (freechoice) 3. As (l)-f feldspar grit (freechoice) 4. As (l)-f granite grit-Heldspar grit (free-choice)
Avg. production
GRIT FOR CHICKENS AND TURKEYS
out grit, the gizzards were not fully developed. However, when the birds reached 36 weeks of age, all gizzards were of approximately equivalent weight, thus indicating that although grit causes the gizzard to develop to its full size earlier in life, it does not cause the gizzard to develop to a greater size than it will ultimately reach in the absence of insoluble grit. Undoubtedly, the fact that the hens receiving no insoluble grit were given whole grains and oyster shell aided in the development of the gizzards in this lot of hens. DISCUSSION
The studies presented in this report show that insoluble grit was necessary for growing chicks, growing turkeys and laying hens for maximum growth, Sfficiency and production, when a mash-andscratch-grain feeding program was used. Calcite grit had little if any effect upon either growth or efficiency of feed utilization in either growing chicks or growing turkeys, indicating that this form of grit is not suited to the dual purpose of supplying calcium and aiding the gizzard in the grinding of scratch grains. Calcite grit, however, appeared to have a beneficial effect upon the enlarged hock disorder in the turkeys under the experimental conditions used. Whether or not this was due to a need for calcium or to the presence in the calcite of an unknown trace mineral required for normal calcification in turkeys remains to be determined. It is possible (1) that the mash fed to the turkeys was too low in calcium to meet the needs of those turkeys having the highest requirements, or (2) that a few of the turkeys in each lot preferred grain to mash and, therefore, failed to obtain their calcium requirement because of an insufficient mash intake. When supplemental calcium was provided, the turkeys having the highest requirements, or those
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that oyster shell is incapable of functioning as an efficient grinding grit. This experiment confirmed the earlier two studies with the chicks and the turkeys in that the hens also showed a definite preference for the feldspar grit. When given a choice between granite grit and feldspar grit, the consumption of granite grit was almost negligible. Oyster shell consumption was approximately equal for all lots, indicating that hens tend to adjust their calcium intake to their needs regardless of other dietary treatments and further indicating that oyster shell fails to serve as a good grinding grit. Gizzard weights. Earlier studies (Piatt and Stephenson, 1935; Heuser and Norris, 1946b; Scott, Holm and Reynolds, 1954) have shown that the feeding of grit to chicks or pheasants receiving all-mash rations causes the development of larger gizzards in the birds receiving the grit than in those receiving the same rations without grit. This has been taken to indicate the desirability of feeding insoluble grit to replacement pullets on the basis that the gizzard should be allowed to develop to its utmost in order to be better capable of grinding coarse grains during the growing and laying periods when the mash-and-scratch-grains method of feeding is used. In order to obtain further information on gizzard development under the various feeding treatments used in the present studies, gizzard weights were determined on the chickens at the end of the broiler experiment (when the pullets were 12 weeks of age) and at the end of the egg-production experiment (when the pullets were 36 weeks of age). The findings are presented in Table 5. These results show that in the 12-weekold pullets receiving insoluble grit, the gizzards had reached maximum size, whereas in the pullets receiving the allmash ration, or the mash and grains with-
281
282
M. L. SCOTT AND G. F. HEUSER
Gizzard weight appears to be no guiding criterion of the efficiency of feed utilization, since the hens in the present experiment which received whole grains and crushed oyster shell showed lower egg production and lower efficiency of feed utilization than those receiving insoluble grit in spite of the fact that the gizzards of the former were as large as those of the latter. Heuser (19S5) showed that grains alone caused the development of larger gizzards. It has also been shown that allmash rations containing highly fibrous materials such as oat hulls cause increased gizzard weights (Hill and Dansky, 1954; Scott, Holm and Reynolds, 1954). The improvement in growth and ef-
ficiency of feed utilization obtained with insoluble grit in this study under a mashand-grain system of feeding confirms the work of Heuser and Norris (1946a, b), Combs, Romoser and Nicholson (1954) and others. Similar results were reported recently by Balloun and Phillips (1956). These workers also report, in contrast to the finding of Combs, Romoser and Nicholson, that the feeding of insoluble grit also improved growth, efficiency of feed utilization and egg production in young chickens and caged hens receiving allmash rations. The experiments presented in the present report were not designed to get further information on the value of grit in all-mash systems of feeding. All evidence on this subject indicates a much less pronounced advantage from the feeding of insoluble grit with all-mash rations than with mash-and-grain feeding, thus indicating that, at times (Combs, Romoser and Nicholson, 1954) the increased return over feed costs as a result of grit feeding with all-mash rations is not sufficient to defray the cost of the grit. On the other hand, the use of insoluble grit with mashand-grain systems of feeding should increase economic returns through its beneficial effects upon growth, egg production and efficiency of feed utilization together with its effect in reducing the over-consumption of calcium grits. SUMMARY
Experiments have been conducted with chicks, turkeys and laying hens on the effects of calcium grits and insoluble grits, singly and in combination, upon growth, egg production and efficiency of feed utilization, under mash-and-grain systems of feeding. The results indicated that: (1) Insoluble grit, either granite or feldspar, improved growth, egg production and efficiency of feed utilization when fed to chickens or turkeys receiving mash and
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consuming the highest percentage of grain, may have consumed extra calcium, thereby accounting for the complete prevention of hock trouble in the lots receiving supplemental calcite, or (3) that the substance in the calcite grit responsible for prevention of the enlarged hock disorder was not calcium, but an unknown trace mineral present in this material. Other recent research on leg weakness conducted at Cornell (Butters and Scott, 1956) indicates the existence of such an unknown mineral required for prevention of leg weakness and for optimum calcification in turkeys. The turkeys showing enlarged hocks were smaller than the average for the lots from which they were taken. It is probable, however, that this drfference in weight was not responsible for the observed differences in bone ash, since Butters and Scott (unpublished) found in other studies that in younger turkeys receiving the same dietary treatment there were no significant differences in the bone ash values for the individuals of different weights. The results of this study indicate, nevertheless, the desirability of feeding both a calcium grit and an insoluble grit to growing turkeys receiving mash and free-choice scratch grains.
GRIT FOR CHICKENS AND TURKEYS
ACKNOWLEDGMENT
The authors wish to thank the Stone Mountain Grit Company for the granite grit and the International Minerals and Chemical Corporation for the feldspar
grit and for financial aid in support of this work. REFERENCES Balloun, S. L., and R. E. Phillips, 1956. Grit feeding affects growth and feed utilization of chicks and egg production of laying hens. Poultry Sci. 35: 566-569. Buckner, G. D., and J. H. Martin, 1922. The function of grit in the gizzard of the chicken. Poultry Sci. 1: 108-113. Butters, H. E., and M. L. Scott, 1956. Further studies on leg weakness in turkeys. Poultry Sci. (in press). Combs, G. F., G. L. Romoser and J. L. Nicholson, 1954. Studies on the evaluation of insoluble grit for broilers. Maryland Agr. Exp. Sta. Misc. Publ. 210. Cooney, W. T., 1941. Influence of various grits on battery-raised broilers. Oregon Circ. 139. Ferber, K. E., and H. Briiggemann, 1933. Die Zugabe von Kalksteingrit und Flintgrit zum Futter bei der Jungmast von Hahnchen. Archiv. fur Gefhlgelkunde 7: 363-368. Heuser, G. F., 1955. Influence of the ration on gizzard development in chickens. World's Poultry Sci. J. 11: 132-138. Heuser, G. F., and L. C. Norris, 1946a. Calcite grit and granite grit as supplements to a chick starting ration. Poultry Sci. 25:195-198. Heuser, G. F., and L. C. Norris, 1946b. Oyster shells, calcite grit, ground limestone and granite grit in rations for hens. Poultry Sci. 25:173-179. Hill, F. W., and L. M. Dansky, 1954. Studies of the energy requirements of chickens. 1. The effect of dietary energy level on growth and feed consumption. Poultry Sci. 33: 112-119. Kaupp, B. F., and J. E. Ivey, 1923. Digestive coefficients of poultry feeds and the rapidity of digestion and fate of grit in the fowl. North Carolina Agr. Exp. Sta. Tech. Bui. 22. Piatt, C. S., and A. B. Stephenson, 1935. The influence of commercial limestone and mica grits upon growth, feed utilization, and gizzard measurements of chicks. New Jersey Agr. Exp. Sta. Bui. 587. Scott, M. L., E. R. Holm and R. E. Reynolds, 1954. Studies on pheasant nutrition. 2. Protein and fiber levels in diets for young pheasants. Poultry Sci. 33: 1237-1244. Waite, R. H., 1935. Miscellaneous studies on poultry grit. Maryland Agr. Exp. Sta. Bui. 377:313-335.
July 16-19. American Poultry Hatchery Federation Convention, Municipal Auditorium, Kansas City, Missouri.
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grains, as compared with similar lots of birds receiving the same rations without grit or with only a calcium grit. (2) Crushed limestone grit (calcite) and crushed oyster shell appeared not to be suited to the dual purpose of supplying calcium and aiding the gizzard in its grinding process, as evidenced by the failure of these materials to improve growth, egg production or feed utilization in chickens or turkeys receiving mash and grain, and by the fact that whole grains (wheat) were found in the gizzards of hens fed oyster shell as the only grit. (3) Growing chicks may over-eat calcium grits somewhat when the diet is already adequate in calcium and when no insoluble grit is fed. Growing turkeys and laying hens, on the other hand, when fed mash-and-grain rations, which require supplementation with extra calcium, appear to be able to adjust calcium intake to their needs whether or not they also have access to insoluble grit. (4) In growing turkeys receiving mash and grain, supplemental calcium may be needed for maximum bone calcification and the prevention of leg weakness. It is possible, however, that for prevention of leg weakness, an unknown mineral, present in the calcite used in these studies, is required. (5) Granite grit and feldspar grit were consumed equally well when fed singly, but the chicks, turkeys and laying hens all preferred feldspar grit to granite grit when given the opportunity to choose between them.
283
E. C. STTJTTS, W. E. BRILES AND H. 0. KTJNKEL Stutts, E. C , W. Johnson, W. E. Briles and H. O. Kunkel. 1956a. Variation in reduced glutathione in bloods of inbred lines of chickens. Proc. Soc. Exp. Biol. Med. 91:60-63. Stutts, E. C , W. E. Briles and H. O. Kunkel, 1956b. Blood glutathione levels and egg production in inbred lines of chickens. Poultry Sci. 35: 727-728. Tuba, J., and N. B. Madsen, 1952. The relationship of dietary factors of rat serum alkaline phosphatase. IT. The effect of total food consumption, methionine, choline and vitamin B12 in normal and alloxan diabetic adult rats. Canadian J. Med. Sci. 30: 18-25. Wiese, A. C , B. C. Johnson, C. A. Elvehjem, E. B. Hart and J. G. Halpin, 1939. A study of blood and bone phosphatase in chick perosis. J. Biol. Chem. 127: 411-420.
The Value of Grit for Chickens and Turkeys M. L. SCOTT AND G. F. HEUSER Department of Poultry Husbandry, Cornell University, Ithaca, New York (Received for publication September 4, 1956)
chickens and turkeys are not SINCE equipped with teeth, the gizzard must take over the function of reducing the size of the coarse particles of food so that it can be acted upon efficiently by the enzymes concerned in digestion and assimilation. This grinding process is aided considerably by furnishing the birds with a hard, insoluble grit which, upon being consumed by the chicken or turkey, passes to the gizzard and remains there for a considerable period of time (Kaupp and Ivey, 1923), passing on through the remainder of the digestive tract only after it has been reduced by the grinding process to a size no longer capable of aiding in the attrition of the coarse particles of food. Upon finding that the gizzards of hens fed crushed limestone or crushed oyster shell contained approximately the same amounts of mineral material as hens fed granite grit, Waite (1935) concluded that
crushed limestone and crushed oyster shell are capable of serving in the dual capacity of calcium supplement and grinding grit for laying hens. Numerous research studies have been conducted which show that supplementary calcium is not only advisable but absolutely necessary for hens receiving both mash and grain. Less is known concerning the need for free-choice supplementation of chicken and turkey mash-and-grain growing rations with calcium in the form of crushed limestone or oyster shell. The question arises, therefore, as to the ability of chickens and turkeys to maintain sufficient grit in the gizzard for grinding purposes without consuming excesses of calcium when crushed limestone or oyster shell is the only form of grit supplied. Also, because of the inherently soft nature of crushed limestone and oyster shells and the fact that these materials readily dissolve in acid solution, such as
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between plasma phosphatase and phosphatase of bone, kidney, liver and intestinal mucosa. Biochem. J. 47: 193-196. Peterson, W. J., and D. B. Parrish, 1939a. Fluctuations of phosphatase and inorganic phosphorus in the blood of the laying hen during the period of egg formation. Poultry Sci. 18: 54-58. Peterson, W. J., and D. B. Parrish, 1939b. Phosphatase and inorganic phosphorus in the plasma and whole blood of the fowl. Poultry Sci. 18: 59-62. Snedecor, G. W., 1946. Statistical Methods. 4th Edition, Iowa State College Press. Ames. Squibb, R. L., M. A. Guzman and N. S. Scrimshaw, 1954. Effect of high environmental temperatures on metabolism. I. Growth and blood constituents of rats exposed to 94°F. for 72 hours. J. Nutrition, 52: 155-163.
GRIT FOR CHICKENS AND TURKEYS
The studies to be presented in this report were undertaken with broilers, growing turkeys and laying hens, using calcium carbonate grits (calcite and crushed oyster shells) and two kinds of insoluble grit (granite and feldspar) singly and in vari-
ous combinations, to determine (1) which grit or combination of grits is most effective in producing increased growth, egg production and efficiency of feed utilization, and (2) whether or not chickens and turkeys tend to over-eat calcium grit or insoluble grit when these are supplied singly as compared to when they are supplied together. PROCEDURE AND RESULTS
Studies with broilers. For the broiler study, ten lots of Vantress pullet chicks, 20 chicks per lot, were used. All lots received a commercial chick starter ration as the only feed for the first three weeks. This ration contained, by analysis, 1.1% calcium and 0.9% phosphorus. At the end of three weeks, all lots except Lot #8 were given access to scratch grains (cracked corn and cracked wheat) on a free-choice basis. At the same time, certain lots were given access to the various kinds of grit as shown in Table 1. Chicksize scratch grains and grits were used until the birds were eight weeks of age, whereupon intermediate-sized scratch grains and grits were fed until the conclusion of the experiment which was conducted until the birds were 12 weeks of age. The results of the experiment, also presented in Table 1, show that the feeding of the insoluble grits (Lots 2, 3, 5, 6, 7) produced decidedly better growth and efficiency of feed utilization than were obtained with the lots (#1 or #4) which received the mash and grain ration without grit or with calcite grit, respectively. When insoluble grit was supplied together with calcite grit, the consumption of the latter was reduced to about one-third the amount consumed when calcite grit was supplied alone, indicating, in confirmation of the work of Heuser and Norris (1946a) that when the calcite grit alone was available, the birds tended to over-eat the cal-
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that present in the proventriculus and gizzard, it appears possible that these materials may lack the hardness to aid in crushing hard kernels of corn and wheat, whereupon the chicken or turkey may over-eat these materials in an effort to obtain sufficient hard grit for proper functioning of the gizzard. On the other hand, when insoluble grit is fed in the absence of supplementary calcium, it is possible that growing chickens, turkeys and laying hens may over-eat the insoluble grit in an effort to obtain calcium to balance the diet with respect to this mineral nutrient (Buckner and Martin, 1922). Heuser and Norris (1946a) showed that the feeding of free-choice calcium grit tended to cause decreased weight gains in chicks receiving a complete starting ration to eight weeks of age, unless an insoluble grit (granite) was supplied free-choice also. These experiments showed that the young chicks consumed more calcium grit when it was the only form of grit supplied than they consumed when granite and calcium grit were both available for choice. These results were in agreement with those of Cooney (1941) and Ferber and Briiggemann (1933) who reported less favorable results with broilers fed calcium grits than with those fed insoluble grits. Combs, Romoser and Nicholson (1954) concluded from studies with broilers raised under practical conditions that the use of granite grit was economically sound (as judged by the increased growth and improvement in feed utilization) when the broilers were fed free-choice mash and cracked corn but was not necessary when the broilers were reared on complete, allmash rations.
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278
M. L. SCOTT AND G. F. HEUSER TABLE 1.—Effects
of different kinds of grit upon weight gains, feed conversion, and grain intake in Vantress pullet chicks to twelve weeks of age
Treatment
Feed consumption /Chick
Efficiency of feed utilization
Mash
Scratch
lbs.
lbs.
lbs.
lbs. feed/ lb. gain
3.39 3.62 3.69 3.44
8.96 8.09 8.27 8.05
1.86 2.90 3.18 3.03
3.23 3.14 3.19 3.34
3.69
8.00
3.15
3.18
3.89
8.55
3.22
3.55
8.07
2.50
3.55
11.03
—
Grit consumption/Chick Granite*
sparf
cite|
lbs.
lbs.
lbs.
— —
— — —
—
0.33
— —
0.37
—
0.18
0.30
—
0.08
3.15
—
0.22
0.07
3.16
0.09
0.23
0.06
3.20
—
—
—
* Gray granite, Stone Mountain Grit Co., Lithonia, Ga. f White feldspar, International Minerals and Chemical Corp., Chicago, 111. Sample of feldspar use 1 was a composite of samples from Maine, South Dakota and Arizona. \ Limecrest calcite, Limestone Products Corp. of America, Newton, N. J.
cite grit in an effort to obtain hard particles to aid the gizzard in grinding the scratch grains. Adequacy of the diet in calcium is substantiated by the low calcite intake of all lots which received both calcite and an insoluble grit. No appreciable differences in consumption of insoluble grit occurred either in the presence or absence of calcite grit. Granite and feldspar grits were consumed equally well when fed singly, but the chicks appeared to prefer feldspar grit to granite grit when given the opportunity to choose between them. In every instance the feeding of grit, including calcite grit, was accompanied by an increased consumption of scratch grains and a decreased consumption of mash as compared with the basal lot receiving mash and grains but no grit. The fact that scratch grains cost less than mash accentuated the economic advantage obtained by the increased efficiency of feed utilization when insoluble grit was fed. Studies with growing turkeys. For the turkey study, 96 White Holland torn tur-
keys were raised to twelve weeks of age on an all-mash regime. All turkeys received a 28% protein commercial turkey starting ration (containing, by analysis, 1.8% calcium and 0.9% phosphorus) for the first eight weeks. From 8 to 12 weeks of age, they received a 20% protein commercial turkey growing ration (containing, by analysis, 2.5% calcium and 1.2% phosphorus). When the turkeys were twelve weeks of age, they were divided into eight lots of equivalent average weight and housed in rearing pens with one-inch wire mesh floors. Seven lots were given the growing mash and coarse scratch grains on a free-choice basis. Six of the lots received granite, feldspar or calcite grit, either alone or in various combinations, while one lot received the mash and grain without grit. The eighth lot received the mash alone, without grain or grit. The plan of the experiment is presented in Table 2. The experiment was continued until the turkeys were 20 weeks of age. The effects of the different kinds of grit upon weight gains, feed conversion
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1. Mash and grain, ad lib. (no grit) As (1) and granite grit As (1) and feldspar grit As (1) and calcite grit As (1) and granite and calcite grit 6. As (1) and feldspar and calcite grit 7. As (1) and granite, feldspar and calcite grits 8. All-mash, no grain nor grit
2. 3. 4. 5.
Avg. wt., 12 wks.
GRIT FOR CHICKENS AND TURKEYS
TABLE 2.—Effects
TABLE 3.—Lower bone-ash values in turkeys receiving mash-and-grain rations as compared to turkeys receiving similar rations plus supplementary calcium grit Avg. wt. 20 wks.
Treatment
lbs. Growing mash and scratch grains (no calcite grit) 12. 5 t Growing mash and scratch grains with calcite grit, free-choice 15.8
Bone ash* % 55.2 59.9
* Average of three turkeys per treatment. f These turkeys weighed less than the average for the corresponding lots because they were suffering from the enlarged hock disorder.
keys showing enlarged hocks in the present study and some of the normal turkeys which received calcite grit showed that calcification in the turkeys suffering from enlarged hocks was inferior to that of the turkeys receiving calcite grit (Table 3). Studies with laying hens. When the pullets used in the broiler study presented in the first experiment became 18 weeks of age, they were housed in four similar laying houses on litter, and fed a commercial laying ration, scratch grains and crushed oyster shell, free-choice, with and without free-choice access to granite grit and feldspar grit (hen-size), singly and in
of different hinds of grit upon weight gains, feed conversion, grain intake and enlarged hock disorder in White Holland turkeys between 12 and 20 weeks of age
Treatment
Avg. gam, 10-20 wks.
Mash
1. Mash and grain, ad lib. (no grit) 2. As (1) and granite grit 3. As (1) and feldspar grit 4. As (1) and calcite grit 5. As (1) and granite and calcite grits 6. As (1) and feldspar and calcite grits 7. As (1) and granite, feldspar and calcite grits 8. All-mash, no grain nor grit
Grit consumption/Turkey Incidence Efficiency enlarged 12-20 wks. of feed hock utilization CalFelddisorder, 12-20 wks. Gran20 wks. ite spar cite Scratch
Feed consumption/Turkey, 12-20 wks.
lbs.
lbs.
lbs.
lbs. feed/ lb. gain
7.8 8.4 8.5 7.9
25.8 25.2 26.6 26.7
7.2 7.2 5.5 7.1
4.23 3.85 3.78 4.28
8.4
24.6
8.1
8.5
23.0
8.2 7.0
lbs.
lbs.
lbs.
—
— —
— — —
%
— —
5.7
—
1.6
25 17 8 0
3.89
4.2
—
2.6
0
10.2
3.90
—
5.6
2.6
0
23.1
7.1
3.70
3.3
4.6
1.0
0
28.4
—
4.06
•—
—
—
0
6.0
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and the enlarged hock disorder are also presented in Table 2. The results of the experiment agree with those obtained with the chickens in showing that insoluble grit is necessary for maximum growth and efficiency of feed utilization when scratch grains are fed. The turkeys receiving insoluble grit gained appreciably more on approximately the same feed intake as compared with the basal lot or the lot receiving only calcite grit. The lot which received the mash without grain grew at a slower rate than any of the lots receiving grain. This was probably due to the relatively high protein and low energy intake of this lot as compared with those having the opportunity to balance their intake of energy through the consumption of grain. The calcite intake by the turkeys was variable and much higher than the calcite intake of the chickens in the previous study. Furthermore, some cases of enlarged hock disorder were observed in all lots receiving grain but no calcite, but no hock trouble occurred in the comparable lots receiving supplemental calcium. Bone ash analyses conducted on the fat-free, moisture-free tibia of some of the tur-
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280
M. L. SCOTT AND G. F. HEUSER TABLE 4.—Effect
of insoluble grit upon egg production and efficiency of feed utilization in Vantress hens over a twelve-week period of production
Treatments
Avg. wt. of hens
Mortality
lbs.
%
%
hen/ 12 wks.
Grit consumption/Hen, 12-wk. period
Emciency
Mash
Grain
Oyster shell
Granite
Feldspar
lbs.
lbs.
lbs.
lbs.
lbs.
0.20
— -—
6.2
lbs. feed/ doz. eggs
6.35
12.1
34.4
40.9
9.21
11.70
0.57
6.43
14.3
43.7
52.0
11.73
10.86
0.52
6.54
6.9
44.0
52.4
12.30
10.81
0.60
0.32
6.3
6.52
5.6
47.5
56.5
12.90
10.44
0.70
0.28
5.9
combination. The mash contained 2.06% calcium and 1.56% phosphorus. The pullets used for the lot which received no insoluble grit were those which had received the basal ration or the basal ration plus calcite grit during the broiler study. Similarly, the pullets which received either granite grit or feldspar grit or the combination of these grits were those which had received the corresponding grit treatments during the starting and growing periods. Each lot contained 40 pullets. The experiment was started after the first month of egg production and was conducted for the succeeding 12-week period. The experimental plan and results are presented in Table 4. The first month of production TABLE 5.—Effect
Feed consumption/ Hen, 12-wk. period
7.3
was omitted from consideration in Table 4 because the hens receiving no insoluble grit (Lot 1) and those receiving only granite grit (Lot 2) were much slower in coming into production than were the two lots which received feldspar grit. The results show that the feeding of insoluble grit was effective in improving egg production and efficiency of feed utilization as compared with that obtained with the lot receiving the laying mash and scratch grains with crushed oyster shells as the only source of grit. The presence of whole grain (wheat) in the gizzards of fasted hens which had received mash, grain and oyster shell as the only form of grit (Table 5) provides further evidence
of ration and grit upon gizzard weights in growing and laying chickens Content of gizzard*
Treatment
Age
Gizzard wt. Grit
Whole
grains
wks.
gms.
%of body wt.
gms.
Pre-laying period: All-mash ration (no grain nor grit) Mash+grain(no grit) Mash-j-grain+feldspar grit
12 12 12
47.8 50.6 52.9
2.12 2.20 2.24
0 0 17.4
Laying period: Mash+grains+oyster Mash+grains+oyster Mash+grains+oyster Mash+grains+oyster +feldspar grit
36 36 36
52.6 51.2 51.6
1.59 1.57 1.66
3 16.6 15.6
+
36
52.4
1.64
13.4
0
shell shell+granite grit shell+feldspai• grit shell+granite grit
* Birds were fasted 16 hours before slaughter.
0
+ 0
0 0
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1. Laying mash+whole grains (corn & wheat 50:50) -{-oyster shell (free-choice) 2. As (1) -f-granite grit (freechoice) 3. As (l)-f feldspar grit (freechoice) 4. As (l)-f granite grit-Heldspar grit (free-choice)
Avg. production
GRIT FOR CHICKENS AND TURKEYS
out grit, the gizzards were not fully developed. However, when the birds reached 36 weeks of age, all gizzards were of approximately equivalent weight, thus indicating that although grit causes the gizzard to develop to its full size earlier in life, it does not cause the gizzard to develop to a greater size than it will ultimately reach in the absence of insoluble grit. Undoubtedly, the fact that the hens receiving no insoluble grit were given whole grains and oyster shell aided in the development of the gizzards in this lot of hens. DISCUSSION
The studies presented in this report show that insoluble grit was necessary for growing chicks, growing turkeys and laying hens for maximum growth, Sfficiency and production, when a mash-andscratch-grain feeding program was used. Calcite grit had little if any effect upon either growth or efficiency of feed utilization in either growing chicks or growing turkeys, indicating that this form of grit is not suited to the dual purpose of supplying calcium and aiding the gizzard in the grinding of scratch grains. Calcite grit, however, appeared to have a beneficial effect upon the enlarged hock disorder in the turkeys under the experimental conditions used. Whether or not this was due to a need for calcium or to the presence in the calcite of an unknown trace mineral required for normal calcification in turkeys remains to be determined. It is possible (1) that the mash fed to the turkeys was too low in calcium to meet the needs of those turkeys having the highest requirements, or (2) that a few of the turkeys in each lot preferred grain to mash and, therefore, failed to obtain their calcium requirement because of an insufficient mash intake. When supplemental calcium was provided, the turkeys having the highest requirements, or those
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that oyster shell is incapable of functioning as an efficient grinding grit. This experiment confirmed the earlier two studies with the chicks and the turkeys in that the hens also showed a definite preference for the feldspar grit. When given a choice between granite grit and feldspar grit, the consumption of granite grit was almost negligible. Oyster shell consumption was approximately equal for all lots, indicating that hens tend to adjust their calcium intake to their needs regardless of other dietary treatments and further indicating that oyster shell fails to serve as a good grinding grit. Gizzard weights. Earlier studies (Piatt and Stephenson, 1935; Heuser and Norris, 1946b; Scott, Holm and Reynolds, 1954) have shown that the feeding of grit to chicks or pheasants receiving all-mash rations causes the development of larger gizzards in the birds receiving the grit than in those receiving the same rations without grit. This has been taken to indicate the desirability of feeding insoluble grit to replacement pullets on the basis that the gizzard should be allowed to develop to its utmost in order to be better capable of grinding coarse grains during the growing and laying periods when the mash-and-scratch-grains method of feeding is used. In order to obtain further information on gizzard development under the various feeding treatments used in the present studies, gizzard weights were determined on the chickens at the end of the broiler experiment (when the pullets were 12 weeks of age) and at the end of the egg-production experiment (when the pullets were 36 weeks of age). The findings are presented in Table 5. These results show that in the 12-weekold pullets receiving insoluble grit, the gizzards had reached maximum size, whereas in the pullets receiving the allmash ration, or the mash and grains with-
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M. L. SCOTT AND G. F. HEUSER
Gizzard weight appears to be no guiding criterion of the efficiency of feed utilization, since the hens in the present experiment which received whole grains and crushed oyster shell showed lower egg production and lower efficiency of feed utilization than those receiving insoluble grit in spite of the fact that the gizzards of the former were as large as those of the latter. Heuser (19S5) showed that grains alone caused the development of larger gizzards. It has also been shown that allmash rations containing highly fibrous materials such as oat hulls cause increased gizzard weights (Hill and Dansky, 1954; Scott, Holm and Reynolds, 1954). The improvement in growth and ef-
ficiency of feed utilization obtained with insoluble grit in this study under a mashand-grain system of feeding confirms the work of Heuser and Norris (1946a, b), Combs, Romoser and Nicholson (1954) and others. Similar results were reported recently by Balloun and Phillips (1956). These workers also report, in contrast to the finding of Combs, Romoser and Nicholson, that the feeding of insoluble grit also improved growth, efficiency of feed utilization and egg production in young chickens and caged hens receiving allmash rations. The experiments presented in the present report were not designed to get further information on the value of grit in all-mash systems of feeding. All evidence on this subject indicates a much less pronounced advantage from the feeding of insoluble grit with all-mash rations than with mash-and-grain feeding, thus indicating that, at times (Combs, Romoser and Nicholson, 1954) the increased return over feed costs as a result of grit feeding with all-mash rations is not sufficient to defray the cost of the grit. On the other hand, the use of insoluble grit with mashand-grain systems of feeding should increase economic returns through its beneficial effects upon growth, egg production and efficiency of feed utilization together with its effect in reducing the over-consumption of calcium grits. SUMMARY
Experiments have been conducted with chicks, turkeys and laying hens on the effects of calcium grits and insoluble grits, singly and in combination, upon growth, egg production and efficiency of feed utilization, under mash-and-grain systems of feeding. The results indicated that: (1) Insoluble grit, either granite or feldspar, improved growth, egg production and efficiency of feed utilization when fed to chickens or turkeys receiving mash and
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consuming the highest percentage of grain, may have consumed extra calcium, thereby accounting for the complete prevention of hock trouble in the lots receiving supplemental calcite, or (3) that the substance in the calcite grit responsible for prevention of the enlarged hock disorder was not calcium, but an unknown trace mineral present in this material. Other recent research on leg weakness conducted at Cornell (Butters and Scott, 1956) indicates the existence of such an unknown mineral required for prevention of leg weakness and for optimum calcification in turkeys. The turkeys showing enlarged hocks were smaller than the average for the lots from which they were taken. It is probable, however, that this drfference in weight was not responsible for the observed differences in bone ash, since Butters and Scott (unpublished) found in other studies that in younger turkeys receiving the same dietary treatment there were no significant differences in the bone ash values for the individuals of different weights. The results of this study indicate, nevertheless, the desirability of feeding both a calcium grit and an insoluble grit to growing turkeys receiving mash and free-choice scratch grains.
GRIT FOR CHICKENS AND TURKEYS
ACKNOWLEDGMENT
The authors wish to thank the Stone Mountain Grit Company for the granite grit and the International Minerals and Chemical Corporation for the feldspar
grit and for financial aid in support of this work. REFERENCES Balloun, S. L., and R. E. Phillips, 1956. Grit feeding affects growth and feed utilization of chicks and egg production of laying hens. Poultry Sci. 35: 566-569. Buckner, G. D., and J. H. Martin, 1922. The function of grit in the gizzard of the chicken. Poultry Sci. 1: 108-113. Butters, H. E., and M. L. Scott, 1956. Further studies on leg weakness in turkeys. Poultry Sci. (in press). Combs, G. F., G. L. Romoser and J. L. Nicholson, 1954. Studies on the evaluation of insoluble grit for broilers. Maryland Agr. Exp. Sta. Misc. Publ. 210. Cooney, W. T., 1941. Influence of various grits on battery-raised broilers. Oregon Circ. 139. Ferber, K. E., and H. Briiggemann, 1933. Die Zugabe von Kalksteingrit und Flintgrit zum Futter bei der Jungmast von Hahnchen. Archiv. fur Gefhlgelkunde 7: 363-368. Heuser, G. F., 1955. Influence of the ration on gizzard development in chickens. World's Poultry Sci. J. 11: 132-138. Heuser, G. F., and L. C. Norris, 1946a. Calcite grit and granite grit as supplements to a chick starting ration. Poultry Sci. 25:195-198. Heuser, G. F., and L. C. Norris, 1946b. Oyster shells, calcite grit, ground limestone and granite grit in rations for hens. Poultry Sci. 25:173-179. Hill, F. W., and L. M. Dansky, 1954. Studies of the energy requirements of chickens. 1. The effect of dietary energy level on growth and feed consumption. Poultry Sci. 33: 112-119. Kaupp, B. F., and J. E. Ivey, 1923. Digestive coefficients of poultry feeds and the rapidity of digestion and fate of grit in the fowl. North Carolina Agr. Exp. Sta. Tech. Bui. 22. Piatt, C. S., and A. B. Stephenson, 1935. The influence of commercial limestone and mica grits upon growth, feed utilization, and gizzard measurements of chicks. New Jersey Agr. Exp. Sta. Bui. 587. Scott, M. L., E. R. Holm and R. E. Reynolds, 1954. Studies on pheasant nutrition. 2. Protein and fiber levels in diets for young pheasants. Poultry Sci. 33: 1237-1244. Waite, R. H., 1935. Miscellaneous studies on poultry grit. Maryland Agr. Exp. Sta. Bui. 377:313-335.
July 16-19. American Poultry Hatchery Federation Convention, Municipal Auditorium, Kansas City, Missouri.
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grains, as compared with similar lots of birds receiving the same rations without grit or with only a calcium grit. (2) Crushed limestone grit (calcite) and crushed oyster shell appeared not to be suited to the dual purpose of supplying calcium and aiding the gizzard in its grinding process, as evidenced by the failure of these materials to improve growth, egg production or feed utilization in chickens or turkeys receiving mash and grain, and by the fact that whole grains (wheat) were found in the gizzards of hens fed oyster shell as the only grit. (3) Growing chicks may over-eat calcium grits somewhat when the diet is already adequate in calcium and when no insoluble grit is fed. Growing turkeys and laying hens, on the other hand, when fed mash-and-grain rations, which require supplementation with extra calcium, appear to be able to adjust calcium intake to their needs whether or not they also have access to insoluble grit. (4) In growing turkeys receiving mash and grain, supplemental calcium may be needed for maximum bone calcification and the prevention of leg weakness. It is possible, however, that for prevention of leg weakness, an unknown mineral, present in the calcite used in these studies, is required. (5) Granite grit and feldspar grit were consumed equally well when fed singly, but the chicks, turkeys and laying hens all preferred feldspar grit to granite grit when given the opportunity to choose between them.
283