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Efficiency of Feed Utilization in New Hampshires to Ten Weeks1
Efficiency of Feed Utilization in New Hampshires to Ten Weeks1 MOELEY G. MCCARTNEY AND MORLEY A. JULL Department of Poultry Husbandry, University of Maryland, College Park, Maryland (Received for publication July 19, 1947)
Barred Plymouth Rocks and crossbreds. The data strongly suggest that the efficiency of feed utilization is inherited. Glazener and Jull (1946) studied efficiency of feed utilization in two strains of New Hampshires and Barred Plymouth Rocks and found that the progeny of the long-shanked strains tended to grow faster and utilize feed more efficiently than the progeny of the short-shanked strains. Differences in rate of growth among strains have also been observed by other workers. Within a strain, the slower growing birds are generally less efficient than the more rapid growing birds. Probably this is due to the greater maintenance requirements for a longer period of time in the case of the slow-growing birds to reach any given weight.
N THE production of poultry for meat purposes, efficiency of feed utilization is a problem of primary importance, since approximately one-half of the cost of production is represented by the feed consumed by the growing birds. Efficiency of feed utilization has been shown to be heritable in many classes of livestock, including poultry. Little progress has been made, however, in an attempt to develop strains of birds characterized by high efficiency of feed utilization. One of the first genetic approaches to the problem of efficiency of feed utilization was conducted in rats by Morris, Palmer, and Kennedy (1933). By nine generations of selective inbreeding, two lines were established in which the lowefficiency line was about 40 percent less efficient than the high-efficiency line. Evidence was provided to support the belief that heritable factors influence the efficiency of food utilization. In efficiency of feed utilization studies in poultry, Hess, Byerly, and Jull (1941) demonstrated that efficiency varies greatly among different strains and crosses. The most efficient purebreds and crossbreds were produced by the same sire. The least efficient Barred Plymouth Rocks and crossbreds required 21.0 to 37.0 percent more feed, respectively, to produce a pound of chicken than the most efficient
MATERIALS AND PROCEDURE In 1944, from the Maryland Experiment Station flock of New Hampshires, two strains, A and B, were developed that differed significantly in body weight at four weeks of age. In the fall of 1945, from these two strains of birds, three pens of strain-A females (half-sisters) and three pens of strain-B females (half-sisters) were selected for breeding purposes. Each pen of females was mated to a male of the same strain, the three half-brother males of each strain being mated to their half-sisters. In the spring of 1946 four hatches were secured from each pen; the first two hatches were reared in batteries to 10
1 Scientific paper No. A170, Contribution No. 2068 of the Maryland Agriculture Experiment Station (Department of Poultry Husbandry).
17
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I
18
MORLEY G. MCCARTNEY AND MORLEY A. JULL
consumed were taken by means of a Toledo scale to the nearest gram. In order to keep conditions as uniform as possible at the time of weighing, all chicks were fasted for a short period of time before weighing. From the six matings made in the fall of 1945, data were collected on a total of 257 strain-A and 233 strain-B progenies reared in batteries; and 165 strain-A and 208 strain-B progenies reared for replacement stock. From the two rematings made in July 1946, data were collected on 120 strain-A and 155 strain-B progenies. Data were also collected on 65 strain-A and 52 strain-B progenies reared from the matings made in September 1946. Thus, data were collected on a total of 607 strain-A and 648 strain-B progenies. In order to determine the differences between strains and the progenies of the sires, the data from all hatches of each mating were combined in order to increase the size of the population and analyzed statistically by methods recommended by Patterson (1939), Snedecor (1940), and Arkin and Colton (1946). Growth was calculated as a function of cumulative feed consumption. Titus and Hendricks (1930), Hammond and Marsden (1938), showed that growth was a function of cumulative feed consumption. Glazener and Jull (1946) studied growth as a function of cumulative feed consumption in two strains of New Hampshires and Barred Plymouth Rocks. The equation, Y = a-\-bX was used; the constants "a" and " b " were solved by means of the least squares method. The " a " value is the weight of the chick at hatching time, and the " b " value is the increase in weight for each unit of feed consumed. The use of the equation of the curve of diminishing increment was suggested by Spillman (1924) for expressing the relationship between feed consumed and live
Downloaded from http://ps.oxfordjournals.org/ at Wayne State University on April 10, 2015
weeks of age and the last two hatches were reared for replacement stock on the Maryland Experiment Station poultry farm. Battery rearing was employed for the first two hatches as a means of providing data on rate of growth, feed consumption, and other factors under well controlled conditions. In order to provide replacement stock and additional data on rate of growth, the last two hatches were reared by the conventional floor-rearing method. On the basis of the observations made on the battery-reared birds in the spring of 1946, one male of each strain was selected in July and mated to females of the same strain on the basis of their progenies' efficiency at 10-weeks of age. From these two matings, three hatches were secured and reared in battery-brooders in order to obtain data on the rate of growth and feed consumption to 10 weeks of age. In September 1946, one pen of females from each strain was selected from the replacement stock on the basis of the efficiency of the battery-reared birds at 10 weeks of age. Each pen of females was mated to a male of the same strain. From these two matings, two hatches were secured and reared in batterybrooders in order to study the rate of growth and feed consumption to 10 weeks of age. At hatching time all of the chicks were pedigreed and weighed. The chicks which provided the data on efficiency of feed utilization were reared in starting batteries and were fed University of Maryland station mash "ad libitum." Feed wastage was kept at a minimum by means of a special feed trough. At 6 weeks of age, the chicks were transferred to growing batteries. All chicks were kept on experiment until 10 weeks of age. Bi-weekly weights of birds and feed
19
FEED UTILIZATION TO T E N WEEKS
gain for the period -—: : : : — — — , and W feed consumption for the period
was solved by the formulae 2
in which W\ was the weight of the chick at the beginning of the bi-weekly period and Wz was the weight at the end of the bi-weekly period. C and k are constants whose values are determined by solving by the least squares method. C is the theoretical maximum efficiency if no feed is used for maintenance and k is the maintenance requirements per unit of weight. RESULTS
In Figure 1-A growth is plotted as a function of cumulative feed consumption. Data from the two feeding trials of the progenies of the three sires of each strain of New Hampshires were combined to give comparable groups and proportional sexes for each strain. In this study, the "a" value is the weight of the chick at hatching time, and the " b " value is the increase in weight for each unit of feed consumed. In Figure I-A, the "a" values shown are somewhat higher than the actual observed values. The regression line plotted by the least squares method fits the data well for the first 8 weeks of the growth period. The high "a" values are apparently due to the failure of the regression line to fit the data for the latter part of the growth period, thus pulling the regression line down. The results show clearly that after an initial growth of about 150 grams, the growth of the progeny of strain B as a function of cumulative feed consumption exceeded that of the progeny of strain A. The difference in the final live weight at the end of the 10-week period was insignificant, but the progeny of strain B increased relatively more in live weight
Downloaded from http://ps.oxfordjournals.org/ at Wayne State University on April 10, 2015
weight in animals. More recently, Jull and Titus (1928), Titus and Jull (1928), and Hendricks, Jull, and Titus (1931) applied the exponential or diminishing increment equation, relating growth to feed consumption in poultry. Hendricks, Jull, and Titus (1932) used the rapid method of evaluating the constants in equation 1 described by Hendricks (1931) in analyzing data on the utilization of feed by chickens. In a study of the growth of chickens as a function of feed consumption, Titus, Jull, and Hendricks (1934) used the equation of the curve of diminishing increment and found that the average live weights computed by means of this equation agreed very closely with the observed average live weights. Brody (1945) discussed the principle of diminishing increment and feed consumption during growth in animals. As the animal grows larger, its maintenance requirements increase and, therefore, the efficiency of growth decreases until at maturity feed consumption continues for maintenance only. Titus (1928), Hammond, Hendricks, and Titus (1938), and Hammond and Marsden (1938) applied the law of diminishing increment in efficiency studies in ducklings, chickens, and turkeys, and found that the relation between live weight and feed consumption was expressible by the law of diminishing increment in the three classes of poultry. Hess, Byerly, and Jull (1941) and Glazener and Jull (1946), in studies of feed utilization in Barred Plymouth Rock and crossbred broilers and two strains of New Hampsbires, respectively, used the formulae E = C— kW; which is a derivative of the equation for the curve of diminishing increment. In this equation, E was calculated by the formulae
20
MORLEY G. MCCARTNEY AND MORLEY A. JULL
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FIG. 1. Growth as a function of cumulative feed consumption in: (A) the progeny of strain A and strain B; (B) the progeny of sire 12 (strain B) and sire 9 (strain A); and (C) the F 2 progeny of sire 12 and sire 9.
for each unit of feed consumed than the progeny of strain A. Figure 1-B shows growth plotted as a function of cumulative feed consumption for the feeding trials of the progeny of sire 9 (strain A) and sire 12 (strain B) each remated to females of its own strain on the basis of their progenies' efficiency at 10 weeks of age. The " a " values are higher than the actual observed values. During the entire growing period, the progeny of sire 12 increased relatively more for each unit of feed consumed than the progeny of sire 9. In Figure 1-C is shown growth plotted as a function of cumulative feed consumption for the F2 progenies of sire 9 and sire 12. The results of these feeding trials indicate that the progeny of strain B tended to grow better and consume less feed for each unit gain than the strain A progeny. Within each sex there was an insignificant difference in body weight between the two strains at 10 weeks. It is interesting to note that the calculated " a " values are very close to the observed hatching weights; the regression line fits the data fairly well for the entire 10-week growing period. The calculated " b " values are very close to those of the
progeny of sire 9 and of sire 12 shown in Figure 1-B. The results of these studies on growth as a function of cumulative feed consumption indicate that the two strains differ in respect to their relative increase in gain for each unit of feed consumed. However, the differences may be insignificant between these two strains, mainly due to the insignificant differences in rate of growth. In Figures 2-A, B, and C, efficiency is plotted as a function of live weight for the same feeding trials considered in Figure 1-A, B, and C, respectively. The weights used were average weights of each successive bi-weekly weights, not the actual weights at weighing time. As mentioned previously, in plotting efficiency as a function of live weight by the formulae E = C-kW, " C " is the theoretical maximum efficiency if no feed is used for maintenance and "k" is the maintenance requirements per unit of weight. The experimental results shown in Figures 2-A and B indicate that the progeny of strain B was more efficient than the progeny of strain A for most of the growing period, but as they reached the end of the 10-week period the progeny of strain A
Downloaded from http://ps.oxfordjournals.org/ at Wayne State University on April 10, 2015
1 1 1 1 1 1 i 0 5 10 15 20 25 JO 0 5 CUMULATIVE FEED CONSUMPTION IN GRAMS ( 1 0 0 )
21
FEED UTILIZATION TO T E N WEEKS
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FIG. 2. Efficiency as a function of live weight in: (A) the progeny of strain A and strain B; (B) the progeny of sire 12 (strain B) and sire 9 (strain A); (C) the F 2 progeny of sire 12 and sire 9.
became the more efficient. In Figure 2-C, the progeny of strain B was more efficient than the progeny of strain A throughout the entire growing period. This was apparently due to the difference in growth rate between the progenies of the two matings. When both sexes were combined the progeny of strain B weighed more at 10 weeks. In Table 1 are given the efficiencies of the progenies of the three sires of the two strains. Since the progeny of each sire reached an average weight of at least 800 grams, in Table 1 the values of E are shown when W is 500 grams and 800 grams, respectively. When W is 500 grams, the progenies of the strain-B sires were more efficient then the progenies of the strain-A sires in every case except for the progeny of sire 8. But when W is 800 grams, the progenies of the strain B sires were the most efficient, except in the case of the progeny of sire 12. These results show that as the progeny of the two strains approached maturity, the differences in efficiencies decreased. This study indicates that probably the best period to compare differences in feed efficiencies is during the first 8 weeks of a chicken's life. Other studies of this kind
TABLE 1.—Values of constants in the formulae E = C—kW, and calculated values for E at 500 grams and 800 grams live weight, respectively. E when E when TF=500 W=?M
Sire
Strain
C
7 9 11 8 10 12
A A A B B B
.339 .317 .343 .372 .418 .396
.000154 .000066 .000069 .000172 .000213 .000106
.282 .284 .308 .286 .311 .343
.236 .264 .288 .234 .248 .312
A B
.339 .395
.000094 .000163
.292 .313
.264 .265
7,9,11 8,10,12
'
K
have shown similar trends in efficiencies; as the birds reach maturity the differences in efficiencies decrease. This being the case, apparently comparisons should be made when the birds reach an average weight of from 500 to 600 grams. Since rate of growth is apparently an important factor influencing efficiency differences in chickens, probably this short period of growth may be the optimum time to make comparisons in efficiencies. When the chickens averaged 500 grams (W being 500 grams), the progeny of strain A required 7.20 percent more feed per unit of gain than the progeny of strain B. When the efficiency of the least efficient strain-A progeny and the most
Downloaded from http://ps.oxfordjournals.org/ at Wayne State University on April 10, 2015
• STRAIN "B"
22
MORLEY
G.
MCCARTNEY AND MORLEY
TABLE 2.—Values of constants in the formulae E=C—kW, and calculated values for E at 500 grams and 800 grams live weight, respectively. Sire
Strain
C
v A
9 12
A B
.333 .396
.000109 .000204
E when E when W=500 TF=800 .279 .294
.246 .233
growing progenies were more efficient then the slower-growing progenies and there was also some evidence that efficiency of feed utilization is inherited. Similar results were obtained by Morris, Palmer, and Kennedy (1933) with rats and by Hess, Byerly, and Jull (1941) with purebred and crossbred chickens. Table 2 gives the values of E when W is 500 grams and 800 grams, respectively, for the progeny of sire 9 (strain A) and of sire 12 (strain B) each mated to its own strain of females which produced the least and the most efficient progenies, respectively. The results show that when W is 500 grams, the progeny of sire 9 required 20.96 percent more feed than the progeny of sire 12. This shows the difference in the efficiency of the progeny of the same sire
TABLE 3.—Values of constants in the formidae E=C—kW, and calculated values for E at 500 grams and 800 grams live weight, respectively. Sire
Strain
9 12
A B
K .305 .324
.000063 .000060
E when E when W = 500 W=800 .274 .294
.245 .276
mated to a relatively different group of females (half-sisters) of the same strain. In Table 3 the values of E are calculated when W is 500 grams and 800 grams, respectively, for the F 2 progeny of sire 9 and of sire 12. At 500 grams live weight t,he progeny of strain A required 5.88 per cent more feed per unit of gain than the progeny of strain B. These results are in close agreement with the differences obtained between the Fi progenies of the same sires, thus supplying additional evidence that efficiency of feed utilization is inherited. SUMMARY
Data were collected on a total of 607 strain-A and 648 strain-B progeny from the two strains of New Hampshires. Body weight and feed consumption data were collected at bi-weekly intervals to 10 weeks of age. Growth was plotted as a function of cumulative feed consumption. Efficiency was plotted as a function of live weight. The values of E, in the formulae E = C—kW, were calculated when W was 500 grams and 800 grams, respectively. The progeny of strain B tended to make greater gains for each unit of feed consumed tjhan the progeny of strain A. The progeny of strain B utilized feed relatively more efficiently than the progeny of strain A, especially during the first few weeks; although the efficiencies tended to approach each other towards the end of the 10-week period. Evidence submitted indicates the heritability of efficiency of feed utilization.
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efficient strain-B progeny were compared, the progeny of sire 7 (strain A) required 21.99 percent more feed than the progeny of sire 12 (strain B). The least efficient strain-A sire's progeny required 9.23 percent more feed than the most efficient strain-A sire's progeny. On the other hand, the least efficient strain-B sire's progeny required 20.07 per cent more feed than the most efficient strain-B sire's progeny. These results indicate that the difference in efficiencies between the progenies of the strain-B sires were more than twice the difference in efficiencies between the progenies of the strain-A sires. Probably part of this difference was due to differences in rate of growth, but the faster-
A. Jtrix
FEED UTILIZATION TO T E N WEEKS REFERENCES
Morris, H. F., L. S. Palmer, and Cornelia Kennedy, 1933. Fundamental food requirements for growth of the rat. VII. An experimental study of inheritance as a factor influencing food utilization of the rat. Univ. of Minn. Agr. Exp. Sta. Tech. Bui. 92, pp.1-56. Patterson, D. D., 1939. Statistical technique in agricultural research. A simple exposition of practice and procedure in biometry. 263 pp. McGraw-Hill Publishing Co., New York. Snedecor, G. W., 1940. Statistical Methods Applied to Experiments in Agriculture and Biology. 414 pp. The Iowa State College Press. Spillman, W. J., and E. Lang, 1924. The Law of Diminishing Returns. 178 pp. World Book Co., Chicago. Titus, H. W., 1928a. Growth and the relation between live weight and feed consumption in the case of White Pekin ducklings. Poultry Sci. 7: 254-263. Titus, H. W., and W. A. Hendricks, 1930. The early growth of the chicken as a function of feed consumption rather than of time. Proc. of the Fourth World's Poultry Congress, London, pp. 285-293. Titus, H. W., and M. A. Jull, 1928. The growth of Rhode Island Reds and the effect of feeding skim-milk on the constants of their growth curves. Jour. Agr. Res. 36: 515-540. Titus, H. W., M. A. Jull, and W. A. Hendricks, 1934. Growth of chickens as a function of feed consumption. Jour. Agr. Res. 48:817-835.
Downloaded from http://ps.oxfordjournals.org/ at Wayne State University on April 10, 2015
Arkin, H., and R. R. Colton, 1946. An Outline of Statistical Methods. 224 pp. Barnes and Noble, Inc. New York. Brody, S., 1945. Bioenergeticsand Growth. 1023 pp. Rienhold Publishing Co., New York. Glazener, E. W., and M. A. Jull, 1946. Feed utilization in growing chickens in relation to shank length. Poultry Sci. 24:355-364. Hammond, J. C.^and S. J. Marsden, 1938. The effect of the level of protein on the growth and feed utilization of turkeys. Poultry Sci. 18:11-18. Hammond, J. C , W. A. Hendricks, and H. W. Titus, 1938. Effect of percentage of protein in the diet on growth and feed utilization of male chickens. Jour. Agr. Res. 56: 791-810. Hendricks, W. A., 1931. Fitting the curve of the diminishing increment to feed consumption liveweight curves. Science (n.s.) 74:290-291. Hendricks, W. A., M. A. Jull, and H. W. Titus, 1931. A possible physiological interpretation of the law of diminishing increment. Science (n.s.) 73:427^129. , 1932. The utilization of feed by chickens. Poultry Sci. 11:74-77. Hess, C. W., T. C. Byerly, and M. A. Jull, 1941. The efficiency of feed utilization by Barred Plymouth Rock and crossbred broilers. Poultry Sci. 20:210-215. Jull, M. A., and H. W. Titus, 1928. Growth of chickens in relation to feed consumption. Jour. Agr. Res. 36:541-550.
23
Barred Plymouth Rocks and crossbreds. The data strongly suggest that the efficiency of feed utilization is inherited. Glazener and Jull (1946) studied efficiency of feed utilization in two strains of New Hampshires and Barred Plymouth Rocks and found that the progeny of the long-shanked strains tended to grow faster and utilize feed more efficiently than the progeny of the short-shanked strains. Differences in rate of growth among strains have also been observed by other workers. Within a strain, the slower growing birds are generally less efficient than the more rapid growing birds. Probably this is due to the greater maintenance requirements for a longer period of time in the case of the slow-growing birds to reach any given weight.
N THE production of poultry for meat purposes, efficiency of feed utilization is a problem of primary importance, since approximately one-half of the cost of production is represented by the feed consumed by the growing birds. Efficiency of feed utilization has been shown to be heritable in many classes of livestock, including poultry. Little progress has been made, however, in an attempt to develop strains of birds characterized by high efficiency of feed utilization. One of the first genetic approaches to the problem of efficiency of feed utilization was conducted in rats by Morris, Palmer, and Kennedy (1933). By nine generations of selective inbreeding, two lines were established in which the lowefficiency line was about 40 percent less efficient than the high-efficiency line. Evidence was provided to support the belief that heritable factors influence the efficiency of food utilization. In efficiency of feed utilization studies in poultry, Hess, Byerly, and Jull (1941) demonstrated that efficiency varies greatly among different strains and crosses. The most efficient purebreds and crossbreds were produced by the same sire. The least efficient Barred Plymouth Rocks and crossbreds required 21.0 to 37.0 percent more feed, respectively, to produce a pound of chicken than the most efficient
MATERIALS AND PROCEDURE In 1944, from the Maryland Experiment Station flock of New Hampshires, two strains, A and B, were developed that differed significantly in body weight at four weeks of age. In the fall of 1945, from these two strains of birds, three pens of strain-A females (half-sisters) and three pens of strain-B females (half-sisters) were selected for breeding purposes. Each pen of females was mated to a male of the same strain, the three half-brother males of each strain being mated to their half-sisters. In the spring of 1946 four hatches were secured from each pen; the first two hatches were reared in batteries to 10
1 Scientific paper No. A170, Contribution No. 2068 of the Maryland Agriculture Experiment Station (Department of Poultry Husbandry).
17
Downloaded from http://ps.oxfordjournals.org/ at Wayne State University on April 10, 2015
I
18
MORLEY G. MCCARTNEY AND MORLEY A. JULL
consumed were taken by means of a Toledo scale to the nearest gram. In order to keep conditions as uniform as possible at the time of weighing, all chicks were fasted for a short period of time before weighing. From the six matings made in the fall of 1945, data were collected on a total of 257 strain-A and 233 strain-B progenies reared in batteries; and 165 strain-A and 208 strain-B progenies reared for replacement stock. From the two rematings made in July 1946, data were collected on 120 strain-A and 155 strain-B progenies. Data were also collected on 65 strain-A and 52 strain-B progenies reared from the matings made in September 1946. Thus, data were collected on a total of 607 strain-A and 648 strain-B progenies. In order to determine the differences between strains and the progenies of the sires, the data from all hatches of each mating were combined in order to increase the size of the population and analyzed statistically by methods recommended by Patterson (1939), Snedecor (1940), and Arkin and Colton (1946). Growth was calculated as a function of cumulative feed consumption. Titus and Hendricks (1930), Hammond and Marsden (1938), showed that growth was a function of cumulative feed consumption. Glazener and Jull (1946) studied growth as a function of cumulative feed consumption in two strains of New Hampshires and Barred Plymouth Rocks. The equation, Y = a-\-bX was used; the constants "a" and " b " were solved by means of the least squares method. The " a " value is the weight of the chick at hatching time, and the " b " value is the increase in weight for each unit of feed consumed. The use of the equation of the curve of diminishing increment was suggested by Spillman (1924) for expressing the relationship between feed consumed and live
Downloaded from http://ps.oxfordjournals.org/ at Wayne State University on April 10, 2015
weeks of age and the last two hatches were reared for replacement stock on the Maryland Experiment Station poultry farm. Battery rearing was employed for the first two hatches as a means of providing data on rate of growth, feed consumption, and other factors under well controlled conditions. In order to provide replacement stock and additional data on rate of growth, the last two hatches were reared by the conventional floor-rearing method. On the basis of the observations made on the battery-reared birds in the spring of 1946, one male of each strain was selected in July and mated to females of the same strain on the basis of their progenies' efficiency at 10-weeks of age. From these two matings, three hatches were secured and reared in battery-brooders in order to obtain data on the rate of growth and feed consumption to 10 weeks of age. In September 1946, one pen of females from each strain was selected from the replacement stock on the basis of the efficiency of the battery-reared birds at 10 weeks of age. Each pen of females was mated to a male of the same strain. From these two matings, two hatches were secured and reared in batterybrooders in order to study the rate of growth and feed consumption to 10 weeks of age. At hatching time all of the chicks were pedigreed and weighed. The chicks which provided the data on efficiency of feed utilization were reared in starting batteries and were fed University of Maryland station mash "ad libitum." Feed wastage was kept at a minimum by means of a special feed trough. At 6 weeks of age, the chicks were transferred to growing batteries. All chicks were kept on experiment until 10 weeks of age. Bi-weekly weights of birds and feed
19
FEED UTILIZATION TO T E N WEEKS
gain for the period -—: : : : — — — , and W feed consumption for the period
was solved by the formulae 2
in which W\ was the weight of the chick at the beginning of the bi-weekly period and Wz was the weight at the end of the bi-weekly period. C and k are constants whose values are determined by solving by the least squares method. C is the theoretical maximum efficiency if no feed is used for maintenance and k is the maintenance requirements per unit of weight. RESULTS
In Figure 1-A growth is plotted as a function of cumulative feed consumption. Data from the two feeding trials of the progenies of the three sires of each strain of New Hampshires were combined to give comparable groups and proportional sexes for each strain. In this study, the "a" value is the weight of the chick at hatching time, and the " b " value is the increase in weight for each unit of feed consumed. In Figure I-A, the "a" values shown are somewhat higher than the actual observed values. The regression line plotted by the least squares method fits the data well for the first 8 weeks of the growth period. The high "a" values are apparently due to the failure of the regression line to fit the data for the latter part of the growth period, thus pulling the regression line down. The results show clearly that after an initial growth of about 150 grams, the growth of the progeny of strain B as a function of cumulative feed consumption exceeded that of the progeny of strain A. The difference in the final live weight at the end of the 10-week period was insignificant, but the progeny of strain B increased relatively more in live weight
Downloaded from http://ps.oxfordjournals.org/ at Wayne State University on April 10, 2015
weight in animals. More recently, Jull and Titus (1928), Titus and Jull (1928), and Hendricks, Jull, and Titus (1931) applied the exponential or diminishing increment equation, relating growth to feed consumption in poultry. Hendricks, Jull, and Titus (1932) used the rapid method of evaluating the constants in equation 1 described by Hendricks (1931) in analyzing data on the utilization of feed by chickens. In a study of the growth of chickens as a function of feed consumption, Titus, Jull, and Hendricks (1934) used the equation of the curve of diminishing increment and found that the average live weights computed by means of this equation agreed very closely with the observed average live weights. Brody (1945) discussed the principle of diminishing increment and feed consumption during growth in animals. As the animal grows larger, its maintenance requirements increase and, therefore, the efficiency of growth decreases until at maturity feed consumption continues for maintenance only. Titus (1928), Hammond, Hendricks, and Titus (1938), and Hammond and Marsden (1938) applied the law of diminishing increment in efficiency studies in ducklings, chickens, and turkeys, and found that the relation between live weight and feed consumption was expressible by the law of diminishing increment in the three classes of poultry. Hess, Byerly, and Jull (1941) and Glazener and Jull (1946), in studies of feed utilization in Barred Plymouth Rock and crossbred broilers and two strains of New Hampsbires, respectively, used the formulae E = C— kW; which is a derivative of the equation for the curve of diminishing increment. In this equation, E was calculated by the formulae
20
MORLEY G. MCCARTNEY AND MORLEY A. JULL
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.
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STRAIN
FIG. 1. Growth as a function of cumulative feed consumption in: (A) the progeny of strain A and strain B; (B) the progeny of sire 12 (strain B) and sire 9 (strain A); and (C) the F 2 progeny of sire 12 and sire 9.
for each unit of feed consumed than the progeny of strain A. Figure 1-B shows growth plotted as a function of cumulative feed consumption for the feeding trials of the progeny of sire 9 (strain A) and sire 12 (strain B) each remated to females of its own strain on the basis of their progenies' efficiency at 10 weeks of age. The " a " values are higher than the actual observed values. During the entire growing period, the progeny of sire 12 increased relatively more for each unit of feed consumed than the progeny of sire 9. In Figure 1-C is shown growth plotted as a function of cumulative feed consumption for the F2 progenies of sire 9 and sire 12. The results of these feeding trials indicate that the progeny of strain B tended to grow better and consume less feed for each unit gain than the strain A progeny. Within each sex there was an insignificant difference in body weight between the two strains at 10 weeks. It is interesting to note that the calculated " a " values are very close to the observed hatching weights; the regression line fits the data fairly well for the entire 10-week growing period. The calculated " b " values are very close to those of the
progeny of sire 9 and of sire 12 shown in Figure 1-B. The results of these studies on growth as a function of cumulative feed consumption indicate that the two strains differ in respect to their relative increase in gain for each unit of feed consumed. However, the differences may be insignificant between these two strains, mainly due to the insignificant differences in rate of growth. In Figures 2-A, B, and C, efficiency is plotted as a function of live weight for the same feeding trials considered in Figure 1-A, B, and C, respectively. The weights used were average weights of each successive bi-weekly weights, not the actual weights at weighing time. As mentioned previously, in plotting efficiency as a function of live weight by the formulae E = C-kW, " C " is the theoretical maximum efficiency if no feed is used for maintenance and "k" is the maintenance requirements per unit of weight. The experimental results shown in Figures 2-A and B indicate that the progeny of strain B was more efficient than the progeny of strain A for most of the growing period, but as they reached the end of the 10-week period the progeny of strain A
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1 1 1 1 1 1 i 0 5 10 15 20 25 JO 0 5 CUMULATIVE FEED CONSUMPTION IN GRAMS ( 1 0 0 )
21
FEED UTILIZATION TO T E N WEEKS
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9 STRAIN
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FIG. 2. Efficiency as a function of live weight in: (A) the progeny of strain A and strain B; (B) the progeny of sire 12 (strain B) and sire 9 (strain A); (C) the F 2 progeny of sire 12 and sire 9.
became the more efficient. In Figure 2-C, the progeny of strain B was more efficient than the progeny of strain A throughout the entire growing period. This was apparently due to the difference in growth rate between the progenies of the two matings. When both sexes were combined the progeny of strain B weighed more at 10 weeks. In Table 1 are given the efficiencies of the progenies of the three sires of the two strains. Since the progeny of each sire reached an average weight of at least 800 grams, in Table 1 the values of E are shown when W is 500 grams and 800 grams, respectively. When W is 500 grams, the progenies of the strain-B sires were more efficient then the progenies of the strain-A sires in every case except for the progeny of sire 8. But when W is 800 grams, the progenies of the strain B sires were the most efficient, except in the case of the progeny of sire 12. These results show that as the progeny of the two strains approached maturity, the differences in efficiencies decreased. This study indicates that probably the best period to compare differences in feed efficiencies is during the first 8 weeks of a chicken's life. Other studies of this kind
TABLE 1.—Values of constants in the formulae E = C—kW, and calculated values for E at 500 grams and 800 grams live weight, respectively. E when E when TF=500 W=?M
Sire
Strain
C
7 9 11 8 10 12
A A A B B B
.339 .317 .343 .372 .418 .396
.000154 .000066 .000069 .000172 .000213 .000106
.282 .284 .308 .286 .311 .343
.236 .264 .288 .234 .248 .312
A B
.339 .395
.000094 .000163
.292 .313
.264 .265
7,9,11 8,10,12
'
K
have shown similar trends in efficiencies; as the birds reach maturity the differences in efficiencies decrease. This being the case, apparently comparisons should be made when the birds reach an average weight of from 500 to 600 grams. Since rate of growth is apparently an important factor influencing efficiency differences in chickens, probably this short period of growth may be the optimum time to make comparisons in efficiencies. When the chickens averaged 500 grams (W being 500 grams), the progeny of strain A required 7.20 percent more feed per unit of gain than the progeny of strain B. When the efficiency of the least efficient strain-A progeny and the most
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• STRAIN "B"
22
MORLEY
G.
MCCARTNEY AND MORLEY
TABLE 2.—Values of constants in the formulae E=C—kW, and calculated values for E at 500 grams and 800 grams live weight, respectively. Sire
Strain
C
v A
9 12
A B
.333 .396
.000109 .000204
E when E when W=500 TF=800 .279 .294
.246 .233
growing progenies were more efficient then the slower-growing progenies and there was also some evidence that efficiency of feed utilization is inherited. Similar results were obtained by Morris, Palmer, and Kennedy (1933) with rats and by Hess, Byerly, and Jull (1941) with purebred and crossbred chickens. Table 2 gives the values of E when W is 500 grams and 800 grams, respectively, for the progeny of sire 9 (strain A) and of sire 12 (strain B) each mated to its own strain of females which produced the least and the most efficient progenies, respectively. The results show that when W is 500 grams, the progeny of sire 9 required 20.96 percent more feed than the progeny of sire 12. This shows the difference in the efficiency of the progeny of the same sire
TABLE 3.—Values of constants in the formidae E=C—kW, and calculated values for E at 500 grams and 800 grams live weight, respectively. Sire
Strain
9 12
A B
K .305 .324
.000063 .000060
E when E when W = 500 W=800 .274 .294
.245 .276
mated to a relatively different group of females (half-sisters) of the same strain. In Table 3 the values of E are calculated when W is 500 grams and 800 grams, respectively, for the F 2 progeny of sire 9 and of sire 12. At 500 grams live weight t,he progeny of strain A required 5.88 per cent more feed per unit of gain than the progeny of strain B. These results are in close agreement with the differences obtained between the Fi progenies of the same sires, thus supplying additional evidence that efficiency of feed utilization is inherited. SUMMARY
Data were collected on a total of 607 strain-A and 648 strain-B progeny from the two strains of New Hampshires. Body weight and feed consumption data were collected at bi-weekly intervals to 10 weeks of age. Growth was plotted as a function of cumulative feed consumption. Efficiency was plotted as a function of live weight. The values of E, in the formulae E = C—kW, were calculated when W was 500 grams and 800 grams, respectively. The progeny of strain B tended to make greater gains for each unit of feed consumed tjhan the progeny of strain A. The progeny of strain B utilized feed relatively more efficiently than the progeny of strain A, especially during the first few weeks; although the efficiencies tended to approach each other towards the end of the 10-week period. Evidence submitted indicates the heritability of efficiency of feed utilization.
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efficient strain-B progeny were compared, the progeny of sire 7 (strain A) required 21.99 percent more feed than the progeny of sire 12 (strain B). The least efficient strain-A sire's progeny required 9.23 percent more feed than the most efficient strain-A sire's progeny. On the other hand, the least efficient strain-B sire's progeny required 20.07 per cent more feed than the most efficient strain-B sire's progeny. These results indicate that the difference in efficiencies between the progenies of the strain-B sires were more than twice the difference in efficiencies between the progenies of the strain-A sires. Probably part of this difference was due to differences in rate of growth, but the faster-
A. Jtrix
FEED UTILIZATION TO T E N WEEKS REFERENCES
Morris, H. F., L. S. Palmer, and Cornelia Kennedy, 1933. Fundamental food requirements for growth of the rat. VII. An experimental study of inheritance as a factor influencing food utilization of the rat. Univ. of Minn. Agr. Exp. Sta. Tech. Bui. 92, pp.1-56. Patterson, D. D., 1939. Statistical technique in agricultural research. A simple exposition of practice and procedure in biometry. 263 pp. McGraw-Hill Publishing Co., New York. Snedecor, G. W., 1940. Statistical Methods Applied to Experiments in Agriculture and Biology. 414 pp. The Iowa State College Press. Spillman, W. J., and E. Lang, 1924. The Law of Diminishing Returns. 178 pp. World Book Co., Chicago. Titus, H. W., 1928a. Growth and the relation between live weight and feed consumption in the case of White Pekin ducklings. Poultry Sci. 7: 254-263. Titus, H. W., and W. A. Hendricks, 1930. The early growth of the chicken as a function of feed consumption rather than of time. Proc. of the Fourth World's Poultry Congress, London, pp. 285-293. Titus, H. W., and M. A. Jull, 1928. The growth of Rhode Island Reds and the effect of feeding skim-milk on the constants of their growth curves. Jour. Agr. Res. 36: 515-540. Titus, H. W., M. A. Jull, and W. A. Hendricks, 1934. Growth of chickens as a function of feed consumption. Jour. Agr. Res. 48:817-835.
Downloaded from http://ps.oxfordjournals.org/ at Wayne State University on April 10, 2015
Arkin, H., and R. R. Colton, 1946. An Outline of Statistical Methods. 224 pp. Barnes and Noble, Inc. New York. Brody, S., 1945. Bioenergeticsand Growth. 1023 pp. Rienhold Publishing Co., New York. Glazener, E. W., and M. A. Jull, 1946. Feed utilization in growing chickens in relation to shank length. Poultry Sci. 24:355-364. Hammond, J. C.^and S. J. Marsden, 1938. The effect of the level of protein on the growth and feed utilization of turkeys. Poultry Sci. 18:11-18. Hammond, J. C , W. A. Hendricks, and H. W. Titus, 1938. Effect of percentage of protein in the diet on growth and feed utilization of male chickens. Jour. Agr. Res. 56: 791-810. Hendricks, W. A., 1931. Fitting the curve of the diminishing increment to feed consumption liveweight curves. Science (n.s.) 74:290-291. Hendricks, W. A., M. A. Jull, and H. W. Titus, 1931. A possible physiological interpretation of the law of diminishing increment. Science (n.s.) 73:427^129. , 1932. The utilization of feed by chickens. Poultry Sci. 11:74-77. Hess, C. W., T. C. Byerly, and M. A. Jull, 1941. The efficiency of feed utilization by Barred Plymouth Rock and crossbred broilers. Poultry Sci. 20:210-215. Jull, M. A., and H. W. Titus, 1928. Growth of chickens in relation to feed consumption. Jour. Agr. Res. 36:541-550.
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