- Email: [email protected]
Studies With Corn-Soya Laying Diets
1078
H. J. EOFF, R. E. DAVIES, T. M. FERGUSON AND J. R. COUCH Effect of dietary calcium-phosphorus adjustment and/or supplementation with terephthalic acid upon serum antibiotic levels of chickens. Poultry Sci. 38: 233-235. Snedecor, G. W., 1956. Statistical Methods. Iowa State College Press, Ames. Stokstad, E. L. R., C. N. Huhtanen, W. L. Williams and T. H. Jukes, 1959. The effect of calcium levels on aureomycin absorption. Poultry Sci. 3 8 : 1251.
Studies With Corn-Soya Laying Diets 5. SEASONAL PATTERNS OF PERFORMANCE AT MARGINAL LEVELS OF DIETARY PROTEIN D. J. BRAY AND D. J. MORRISSEY1 Department of Animal Science, University of Illinois, Urbana, Illinois (Received for publication November 10, 1961)
N
UMEROUS workers have reported acceptable levels of egg production from pullets fed corn-soya type laying diets containing less than the IS percent of protein recommended by the National Research Council (1960); Thornton et al. (1957), Waibel and Johnson (1961), and Bray and Gesell (1961). An appraisal of the above reports indicated that corn-soya type diets formulated to contain 12 percent of protein were marginal for meeting the amino acid needs of laying pullets. With the exception of the recent reports of Johnson and Fisher (1959) and Waibel and Johnson (1961), few data are available concerning the comparative performance of pullets at successive intervals during the laying year when fed diets containing marginal and adequate levels of protein. The findings of Bray and Gesell (1961) suggest that seasonal trends in temperature, as they affect feed consumption and, hence,
1 Present address, Minooka Community High School, Minooka, Illinois.
protein intake, may influence the relative performance of pullets fed diets containing marginal and adequate levels of protein. In the study reported herein, the performance of pullets fed corn-soya type laying diets containing 12 and 18 percent protein was compared at successive periods during an assay period of 42 weeks. The results would suggest that, except for a short period at the beginning and near the end of the assay period, performance was comparable at the two protein levels. EXPERIMENTAL
The experiment was initiated on September 27, 1960 and terminated on July 18, 1961. Eighteen 257-day-old and seven 207day-old White Leghorn pullets and three males were allotted at random to each of eight floor pens in a non-insulated poultry house. Four pens of pullets were fed diet 1 (12% protein), Table 1, and a like number was fed diet 2 (18% protein). Continuous lighting and ad libitum feeding and watering management practices were followed. Supplemental heat was provided
Downloaded from http://ps.oxfordjournals.org/ at University of Nebraska-Lincoln Libraries on June 11, 2016
ured by clinical effect. Poultry Sci. 39: 960-970. Price, K. E., Z. Zolli Jr., J. C. Atkinson and H. G. Luther, 1957a. Antibiotic inhibitors. I. The effect of certain milk constituents. Antibiotics Chemotherapy, 7: 672-688. Price, K. E., Z. Zolli Jr., J. C. Atkinson and H. G. Luther, 19S7b. Antibiotic inhibitors. II. Studies on the inhibitory action of selected divalent cations for oxytetracycline. Antibiotics Chemotherapy, 7: 689-701. Price, K. E., Z. Zolli Jr. and J. H. Hare, 1959.
CORN-SOYA LAYING DIETS TABLE 1.—Experimental diets Ingredient
Percent proteinPercent of protein from soybean oil meal Percent of protein from corn Calculated amino acid content, Amino acid Arginine Histidine Isoleucine Leucine Lysine Methionine and cystine Phenylalanine and tyrosine Threonine Tryptophan Valine
Diet 2
%
%
var 1 var var 4.70 2.00 0.50 0.05 0.25 0.25
var var var 4.70 2.00 0.50 0.05 0.25 0.25
+ + + + +
+ + + + +
100.00
100.00
12.0
18.0
45 70 55 30 percent of ration 2 0.67 0.29 0.58 1.25 0.54 0.353 1.03 0.48 0.1P 0.63
1.12 0.45 0.95 1.64 0.98 0.47 1.50 0.71 0.19 0.94
1
See text for explanation. 2 Based upon the amino acid composition of proteins by Block and Weiss (1956). 3 Calculated to be deficient by NRC (1960) nutrient requirements and Johnson and Fisher (1958) egg protein ratio standard.
only when necessary to prevent the water system from freezing. Fresh mixes of feed were prepared at approximately monthly intervals. All samples of corn and soybean oil meal were analyzed for protein (N X 6.25) prior to the mixing of diets. Soybean oil meal contributed 45 and 70 percent of the protein in the 12 and 18 percent protein diets, respectively, in all mixes. Corn starch was added as needed to bring the diets to 100 parts, Table 1. Egg production was summarized on a hen-day basis for each successive period as
shown in Table 2. Egg weight was determined on a pen basis for each period by a group weighing of all eggs produced on each of three consecutive days. The feed intake of males was assumed to be equal to that of the females. RESULTS AND DISCUSSION Egg production of pullets fed the 12 percent protein diet was significantly lower during the first three 4-week assay periods than that of birds fed the 18 percent protein diet, Table 2. During the following six 4-week periods, egg production was comparable at the two protein levels. A significantly lower rate of lay was apparent at the 12 percent protein level during the final six weeks of the assay. Egg weight was comparable at the two protein levels throughout the assay with the exception of the first 4-week period. Therefore, the pattern of egg yields tended to parallel that of egg production. Cumulative gains in body weight of birds fed the 12 percent protein diet were significantly less during the initial two periods of the assay. However, during the 9-12 week period, birds fed the 12 percent protein diet gained 67 grams as compared to 30 grams at the 18 percent protein level. No significant differences in body weight patterns were apparent then and thereafter until the final weighing, Table 2. These trends appear to be related to the level of feed consumption and hence protein intake as influenced by environmental temperature. However, the need for additional protein for the completion of growth and feather development in the early assay periods and for feather replacement near the terminal period undoubtedly exerted an influence upon the observations. When molt of the primary wing feathers was recorded at the termination of the experiment, birds fed the 12 and 18 percent protein diets had molted an average of 3.25
Downloaded from http://ps.oxfordjournals.org/ at University of Nebraska-Lincoln Libraries on June 11, 2016
Ground yellow corn Soybean oil meal, dehulled Starch Ground limestone Dicalcium phosphate Salt-iodized Manganese sulfate—70% Bi2-antibiotic supplement Choline chloride—25% Niacin 10 mg./lb. Vitamin D 3 300 I.C.U./lb. Riboflavin 2 mg./lb. Vitamin A 2000 I.U./lb. Calcium pantothenate 2 mg./lb.
Diet 1
1079
1080
D.
J.
BRAY AND D.
J.
MORRISSEY
TABLE 2.—Performance of pullets fed 12 and 18 percent protein diets during successive periods of a 42-week assay
Period (wks.)
57.6 44.8 32.2 28.1 21.2 42.9 41.0 51.4 61.9 71.5
18* 74« 141 190 204 219 225 251 240
53 121 151 199 210 232 225 259 274
— —
Egg prod.
%
Egg weight gm.
Egg yield gm./bir d / d a y
Feed cons. gm./bird/day
Protein cons. gm./bird/day
Gm. egg/gm. proteii l cons.
12% P
18% P
12% P
18% P
12% P
18% P
12% 1 8 % P P
12% 1 8 % P P
12% P
18% P
64.8** 68.9** 75.3* 76.2 71.1 70.1 66.7 60.3 58.7 52.5*
77.3 81.8 80.3 73.6 70.6 69.3 65.9 59.5 57.4 58.0
52.6 54.0* 57.1 58.1 59.7 60.2 60.6 61.1 61.7 61.1 61.0
52.5 55.4 57.2 58.9 60.1 60.1 60.4 61.3 61.7 61.1 60.6
34.9** 39.3** 43.7* 45.5 42.8 42.5 40.8 37.2 35.9
42.8 46.8 47.3 44.4 42.4 41.9 40.4 36.7 35.1
111 120 130 133 1202 133 132 130 118
115 120 124 129 1202 128 128 130 117
13.3 14.4 15.6 16.0 14.9 16.0 15.8 15.6 14.2
20.7 21.6 22.3 23.2 21.6 23.0 23.0 23.4 21.1
2.62 2.73 2.80 2.84 2.87 2.66 2.58 2.38 2.53
2.07 2.17 2.12 1.91 1.96 1.82 1.76 1.57 1.66
31.1*
34.6
106
106
12.7
19.1
2.45
1.81
39.0*
40.9
122.8 121.1
14.7
21.8
2.65
1.88
41-42J
173*
220
48.0*
54.7
61.0
60.9
1-42
173*
220
65.8*
68.8
59.3
59.4
1 2
As reported by the U. S. Weather Bureau, Champaign, Illinois. Supplemental heat and minimum ventilation during this period may explain lower feed intake. * Significant (P<.05). ** Significant (P<.01).
and 4.482 primary feathers, respectively. This indicated that birds fed the 18 percent protein diet were more capable of maintaining egg production and body weight even though wing molt, for some unexplained reason, was more advanced at this protein level. Contrary to the progressive reduction in the intake of diets containing suboptimal levels of protein under constant temperature conditions reported by Bray and Gesell (1961), consumption of the 12 percent protein diet increased under the decreasing temperature conditions during the experiment reported herein. This raises the unanswered question of whether performance at the two protein levels would have been comparable from the 13 th through the 36th week had the environmental temperature of the 1-4 week period prevailed throughout. Mortality over the 42-week period was 16 and 62 percent at the 12 and 18 percent protein levels, respectively. As expected, the maximum conversion of ingested protein to eggs appeared to coincide with the maximum rate of lay at2
Significantly different at the 5 percent level of
probability by t-test of Senedecor (1956).
tained. The maximum conversion occurred during the 5-8 week period at the 18 percent protein level, but not until the 13-16 week period at the 12 percent protein level, Table 2. When Bray and Gesell (1961) fed young pullets diets containing graded levels of the optimum combination of corn and soybean protein (45:55), as determined by Bray (1960), to insure different levels of protein intake over an 8-week assay period, egg yield was maximized at 45-50 gram/bird/day. This coincided with a daily protein intake of 13-14 grams per bird. In the same report, it was found that a daily protein intake of 10 grams per bird supported a 35-40 gram/bird/day yield. However, calculations show that egg yield of pullets fed the 12 percent protein diet averaged only 37.1 grams/bird/day at a daily protein intake of 13.9 grams per bird during the first 8 weeks of the assay reported herein. This may be partially explained on the basis that the 55:45 mixture of corn and soybean protein, diet 1, was not as adequate at a given suboptimal level of protein intake for sustaining egg production as the (45:55) combination used by Bray and Gesell (1961).
Downloaded from http://ps.oxfordjournals.org/ at University of Nebraska-Lincoln Libraries on June 11, 2016
0 1- 4 5- 8 9-12 13-16 17-20 21-24 25-28 29-32 33-36 37-401
Cumulative Mean 1 body weight daily gain, gm. temp. °F. 12% 18% P P
1081
CORN-SOYA LAYING DIETS SUMMARY AND CONCLUSIONS
When pullets were fed corn-soya diets containing 12 and 18 percent protein for a 42-week assay period beginning in September and terminating the following July, performance was comparable at the two protein levels, except for the first 12-week and last 6-week periods of the assay, during which performance was significantly lower for one or more criteria at the 12 percent protein level. The results indicate the necessity of considering the level of feed intake, maturity and physiological status of the bird, rate of lay, and/or various combinations of these factors in interpreting the results of experiments designed to assay the amino acid adequacy of diets fed to laying hens. REFERENCES Block, R. J., and K. W. Weiss, 1956. Amino Acid Handbook, Charles C Thomas, Springfield, Illinois. Bray, D. J., 1960. Studies with corn-soya laying diets. 2. Optimum combinations of corn and soybean protein. Poultry Sci. 39: 1541-1546. Bray, D. J., and J. A. Gesell, 1961. Studies with corn-soya laying diets. 4. Environmental temperature—a factor affecting performance of pullets fed diets suboptimal in protein. Poultry Sci. 40: 1328-1335. Johnson, D., Jr., and H. Fisher, 1958. The aminoacid requirement of laying hens. 3. Minimal requirement levels of essential amino-acids; techniques and development of diet. Brit. J. Nutrition, 12: 276-285. Johnson, D., Jr., and H. Fisher, 1959. The amino acid requirement of laying hens. 4. Supplying minimal levels of essential amino acids from natural feed ingredients. Poultry Sci. 38: 149152. National Research Council, 1960. Nutrient requirements of poultry. Publication 827. Snedecor, G. W., 1956. Statistical Methods. Iowa State College Press, Ames, Iowa. Thornton, P. A., L. G. Blaylock and R. E. Moreng, 1957. Protein level as a factor in egg production. Poultry Sci. 36: 552-557. Waibel, P. E., and E. L. Johnson, 1961. Effect of low protein corn-soybean oil meal diets and amino acid supplementation on performance of laying hens. Poultry Sci. 40: 293-298.
Downloaded from http://ps.oxfordjournals.org/ at University of Nebraska-Lincoln Libraries on June 11, 2016
Once the pullets had attained comparable body weight at the two protein levels (12 weeks), intake of the 12 percent protein diet appeared to be adequate for sustaining an acceptable rate of lay (60-70%) during the winter and spring months even though calculations indicated that this diet was deficient in sulfur-containing amino acids and tryptophan, Table 1. Assuming that shell eggs contain 12 percent protein of the amino acid pattern given by Block and Weiss (1956), 61 percent of the sulfur-amino acids and 56 percent of the tryptophan ingested was accounted for in the egg protein synthesized over the 42week period. From the data of Johnson and Fisher (1959) it can be calculated that their 10.4 percent protein ration, formulated to provide all essential amino acids in amounts equal to or in excess of the Johnson and Fisher (1958) standard, supported a daily egg yield of 32.8 grams per bird at a daily protein intake of 14.3 grams per bird over a 28-week assay period. Thus, only 2.29 grams of egg were synthesized per gram of protein consumed compared to 2.65 grams for birds fed the 12 percent protein diet in our studies, Table 2. Assuming that their 10.4 percent protein diet, formulated to meet the aforementioned standard, provided a better pattern of amino acids than the mixture of corn and soybean protein used in our 12 percent diet, these observations would suggest that Johnson and Fisher (1959) might have attained comparable egg production at still lower dietary levels of the same protein at the feed intake reported. The findings and discussion presented herein suggest that the level of feed intake, maturity and physiological status of the bird, rate of lay, and/or various combinations of these factors are indeed pertinent to the interpretation of experiments designed to assy the protein (amino acid) adequacy of diets fed to laying hens.
H. J. EOFF, R. E. DAVIES, T. M. FERGUSON AND J. R. COUCH Effect of dietary calcium-phosphorus adjustment and/or supplementation with terephthalic acid upon serum antibiotic levels of chickens. Poultry Sci. 38: 233-235. Snedecor, G. W., 1956. Statistical Methods. Iowa State College Press, Ames. Stokstad, E. L. R., C. N. Huhtanen, W. L. Williams and T. H. Jukes, 1959. The effect of calcium levels on aureomycin absorption. Poultry Sci. 3 8 : 1251.
Studies With Corn-Soya Laying Diets 5. SEASONAL PATTERNS OF PERFORMANCE AT MARGINAL LEVELS OF DIETARY PROTEIN D. J. BRAY AND D. J. MORRISSEY1 Department of Animal Science, University of Illinois, Urbana, Illinois (Received for publication November 10, 1961)
N
UMEROUS workers have reported acceptable levels of egg production from pullets fed corn-soya type laying diets containing less than the IS percent of protein recommended by the National Research Council (1960); Thornton et al. (1957), Waibel and Johnson (1961), and Bray and Gesell (1961). An appraisal of the above reports indicated that corn-soya type diets formulated to contain 12 percent of protein were marginal for meeting the amino acid needs of laying pullets. With the exception of the recent reports of Johnson and Fisher (1959) and Waibel and Johnson (1961), few data are available concerning the comparative performance of pullets at successive intervals during the laying year when fed diets containing marginal and adequate levels of protein. The findings of Bray and Gesell (1961) suggest that seasonal trends in temperature, as they affect feed consumption and, hence,
1 Present address, Minooka Community High School, Minooka, Illinois.
protein intake, may influence the relative performance of pullets fed diets containing marginal and adequate levels of protein. In the study reported herein, the performance of pullets fed corn-soya type laying diets containing 12 and 18 percent protein was compared at successive periods during an assay period of 42 weeks. The results would suggest that, except for a short period at the beginning and near the end of the assay period, performance was comparable at the two protein levels. EXPERIMENTAL
The experiment was initiated on September 27, 1960 and terminated on July 18, 1961. Eighteen 257-day-old and seven 207day-old White Leghorn pullets and three males were allotted at random to each of eight floor pens in a non-insulated poultry house. Four pens of pullets were fed diet 1 (12% protein), Table 1, and a like number was fed diet 2 (18% protein). Continuous lighting and ad libitum feeding and watering management practices were followed. Supplemental heat was provided
Downloaded from http://ps.oxfordjournals.org/ at University of Nebraska-Lincoln Libraries on June 11, 2016
ured by clinical effect. Poultry Sci. 39: 960-970. Price, K. E., Z. Zolli Jr., J. C. Atkinson and H. G. Luther, 1957a. Antibiotic inhibitors. I. The effect of certain milk constituents. Antibiotics Chemotherapy, 7: 672-688. Price, K. E., Z. Zolli Jr., J. C. Atkinson and H. G. Luther, 19S7b. Antibiotic inhibitors. II. Studies on the inhibitory action of selected divalent cations for oxytetracycline. Antibiotics Chemotherapy, 7: 689-701. Price, K. E., Z. Zolli Jr. and J. H. Hare, 1959.
CORN-SOYA LAYING DIETS TABLE 1.—Experimental diets Ingredient
Percent proteinPercent of protein from soybean oil meal Percent of protein from corn Calculated amino acid content, Amino acid Arginine Histidine Isoleucine Leucine Lysine Methionine and cystine Phenylalanine and tyrosine Threonine Tryptophan Valine
Diet 2
%
%
var 1 var var 4.70 2.00 0.50 0.05 0.25 0.25
var var var 4.70 2.00 0.50 0.05 0.25 0.25
+ + + + +
+ + + + +
100.00
100.00
12.0
18.0
45 70 55 30 percent of ration 2 0.67 0.29 0.58 1.25 0.54 0.353 1.03 0.48 0.1P 0.63
1.12 0.45 0.95 1.64 0.98 0.47 1.50 0.71 0.19 0.94
1
See text for explanation. 2 Based upon the amino acid composition of proteins by Block and Weiss (1956). 3 Calculated to be deficient by NRC (1960) nutrient requirements and Johnson and Fisher (1958) egg protein ratio standard.
only when necessary to prevent the water system from freezing. Fresh mixes of feed were prepared at approximately monthly intervals. All samples of corn and soybean oil meal were analyzed for protein (N X 6.25) prior to the mixing of diets. Soybean oil meal contributed 45 and 70 percent of the protein in the 12 and 18 percent protein diets, respectively, in all mixes. Corn starch was added as needed to bring the diets to 100 parts, Table 1. Egg production was summarized on a hen-day basis for each successive period as
shown in Table 2. Egg weight was determined on a pen basis for each period by a group weighing of all eggs produced on each of three consecutive days. The feed intake of males was assumed to be equal to that of the females. RESULTS AND DISCUSSION Egg production of pullets fed the 12 percent protein diet was significantly lower during the first three 4-week assay periods than that of birds fed the 18 percent protein diet, Table 2. During the following six 4-week periods, egg production was comparable at the two protein levels. A significantly lower rate of lay was apparent at the 12 percent protein level during the final six weeks of the assay. Egg weight was comparable at the two protein levels throughout the assay with the exception of the first 4-week period. Therefore, the pattern of egg yields tended to parallel that of egg production. Cumulative gains in body weight of birds fed the 12 percent protein diet were significantly less during the initial two periods of the assay. However, during the 9-12 week period, birds fed the 12 percent protein diet gained 67 grams as compared to 30 grams at the 18 percent protein level. No significant differences in body weight patterns were apparent then and thereafter until the final weighing, Table 2. These trends appear to be related to the level of feed consumption and hence protein intake as influenced by environmental temperature. However, the need for additional protein for the completion of growth and feather development in the early assay periods and for feather replacement near the terminal period undoubtedly exerted an influence upon the observations. When molt of the primary wing feathers was recorded at the termination of the experiment, birds fed the 12 and 18 percent protein diets had molted an average of 3.25
Downloaded from http://ps.oxfordjournals.org/ at University of Nebraska-Lincoln Libraries on June 11, 2016
Ground yellow corn Soybean oil meal, dehulled Starch Ground limestone Dicalcium phosphate Salt-iodized Manganese sulfate—70% Bi2-antibiotic supplement Choline chloride—25% Niacin 10 mg./lb. Vitamin D 3 300 I.C.U./lb. Riboflavin 2 mg./lb. Vitamin A 2000 I.U./lb. Calcium pantothenate 2 mg./lb.
Diet 1
1079
1080
D.
J.
BRAY AND D.
J.
MORRISSEY
TABLE 2.—Performance of pullets fed 12 and 18 percent protein diets during successive periods of a 42-week assay
Period (wks.)
57.6 44.8 32.2 28.1 21.2 42.9 41.0 51.4 61.9 71.5
18* 74« 141 190 204 219 225 251 240
53 121 151 199 210 232 225 259 274
— —
Egg prod.
%
Egg weight gm.
Egg yield gm./bir d / d a y
Feed cons. gm./bird/day
Protein cons. gm./bird/day
Gm. egg/gm. proteii l cons.
12% P
18% P
12% P
18% P
12% P
18% P
12% 1 8 % P P
12% 1 8 % P P
12% P
18% P
64.8** 68.9** 75.3* 76.2 71.1 70.1 66.7 60.3 58.7 52.5*
77.3 81.8 80.3 73.6 70.6 69.3 65.9 59.5 57.4 58.0
52.6 54.0* 57.1 58.1 59.7 60.2 60.6 61.1 61.7 61.1 61.0
52.5 55.4 57.2 58.9 60.1 60.1 60.4 61.3 61.7 61.1 60.6
34.9** 39.3** 43.7* 45.5 42.8 42.5 40.8 37.2 35.9
42.8 46.8 47.3 44.4 42.4 41.9 40.4 36.7 35.1
111 120 130 133 1202 133 132 130 118
115 120 124 129 1202 128 128 130 117
13.3 14.4 15.6 16.0 14.9 16.0 15.8 15.6 14.2
20.7 21.6 22.3 23.2 21.6 23.0 23.0 23.4 21.1
2.62 2.73 2.80 2.84 2.87 2.66 2.58 2.38 2.53
2.07 2.17 2.12 1.91 1.96 1.82 1.76 1.57 1.66
31.1*
34.6
106
106
12.7
19.1
2.45
1.81
39.0*
40.9
122.8 121.1
14.7
21.8
2.65
1.88
41-42J
173*
220
48.0*
54.7
61.0
60.9
1-42
173*
220
65.8*
68.8
59.3
59.4
1 2
As reported by the U. S. Weather Bureau, Champaign, Illinois. Supplemental heat and minimum ventilation during this period may explain lower feed intake. * Significant (P<.05). ** Significant (P<.01).
and 4.482 primary feathers, respectively. This indicated that birds fed the 18 percent protein diet were more capable of maintaining egg production and body weight even though wing molt, for some unexplained reason, was more advanced at this protein level. Contrary to the progressive reduction in the intake of diets containing suboptimal levels of protein under constant temperature conditions reported by Bray and Gesell (1961), consumption of the 12 percent protein diet increased under the decreasing temperature conditions during the experiment reported herein. This raises the unanswered question of whether performance at the two protein levels would have been comparable from the 13 th through the 36th week had the environmental temperature of the 1-4 week period prevailed throughout. Mortality over the 42-week period was 16 and 62 percent at the 12 and 18 percent protein levels, respectively. As expected, the maximum conversion of ingested protein to eggs appeared to coincide with the maximum rate of lay at2
Significantly different at the 5 percent level of
probability by t-test of Senedecor (1956).
tained. The maximum conversion occurred during the 5-8 week period at the 18 percent protein level, but not until the 13-16 week period at the 12 percent protein level, Table 2. When Bray and Gesell (1961) fed young pullets diets containing graded levels of the optimum combination of corn and soybean protein (45:55), as determined by Bray (1960), to insure different levels of protein intake over an 8-week assay period, egg yield was maximized at 45-50 gram/bird/day. This coincided with a daily protein intake of 13-14 grams per bird. In the same report, it was found that a daily protein intake of 10 grams per bird supported a 35-40 gram/bird/day yield. However, calculations show that egg yield of pullets fed the 12 percent protein diet averaged only 37.1 grams/bird/day at a daily protein intake of 13.9 grams per bird during the first 8 weeks of the assay reported herein. This may be partially explained on the basis that the 55:45 mixture of corn and soybean protein, diet 1, was not as adequate at a given suboptimal level of protein intake for sustaining egg production as the (45:55) combination used by Bray and Gesell (1961).
Downloaded from http://ps.oxfordjournals.org/ at University of Nebraska-Lincoln Libraries on June 11, 2016
0 1- 4 5- 8 9-12 13-16 17-20 21-24 25-28 29-32 33-36 37-401
Cumulative Mean 1 body weight daily gain, gm. temp. °F. 12% 18% P P
1081
CORN-SOYA LAYING DIETS SUMMARY AND CONCLUSIONS
When pullets were fed corn-soya diets containing 12 and 18 percent protein for a 42-week assay period beginning in September and terminating the following July, performance was comparable at the two protein levels, except for the first 12-week and last 6-week periods of the assay, during which performance was significantly lower for one or more criteria at the 12 percent protein level. The results indicate the necessity of considering the level of feed intake, maturity and physiological status of the bird, rate of lay, and/or various combinations of these factors in interpreting the results of experiments designed to assay the amino acid adequacy of diets fed to laying hens. REFERENCES Block, R. J., and K. W. Weiss, 1956. Amino Acid Handbook, Charles C Thomas, Springfield, Illinois. Bray, D. J., 1960. Studies with corn-soya laying diets. 2. Optimum combinations of corn and soybean protein. Poultry Sci. 39: 1541-1546. Bray, D. J., and J. A. Gesell, 1961. Studies with corn-soya laying diets. 4. Environmental temperature—a factor affecting performance of pullets fed diets suboptimal in protein. Poultry Sci. 40: 1328-1335. Johnson, D., Jr., and H. Fisher, 1958. The aminoacid requirement of laying hens. 3. Minimal requirement levels of essential amino-acids; techniques and development of diet. Brit. J. Nutrition, 12: 276-285. Johnson, D., Jr., and H. Fisher, 1959. The amino acid requirement of laying hens. 4. Supplying minimal levels of essential amino acids from natural feed ingredients. Poultry Sci. 38: 149152. National Research Council, 1960. Nutrient requirements of poultry. Publication 827. Snedecor, G. W., 1956. Statistical Methods. Iowa State College Press, Ames, Iowa. Thornton, P. A., L. G. Blaylock and R. E. Moreng, 1957. Protein level as a factor in egg production. Poultry Sci. 36: 552-557. Waibel, P. E., and E. L. Johnson, 1961. Effect of low protein corn-soybean oil meal diets and amino acid supplementation on performance of laying hens. Poultry Sci. 40: 293-298.
Downloaded from http://ps.oxfordjournals.org/ at University of Nebraska-Lincoln Libraries on June 11, 2016
Once the pullets had attained comparable body weight at the two protein levels (12 weeks), intake of the 12 percent protein diet appeared to be adequate for sustaining an acceptable rate of lay (60-70%) during the winter and spring months even though calculations indicated that this diet was deficient in sulfur-containing amino acids and tryptophan, Table 1. Assuming that shell eggs contain 12 percent protein of the amino acid pattern given by Block and Weiss (1956), 61 percent of the sulfur-amino acids and 56 percent of the tryptophan ingested was accounted for in the egg protein synthesized over the 42week period. From the data of Johnson and Fisher (1959) it can be calculated that their 10.4 percent protein ration, formulated to provide all essential amino acids in amounts equal to or in excess of the Johnson and Fisher (1958) standard, supported a daily egg yield of 32.8 grams per bird at a daily protein intake of 14.3 grams per bird over a 28-week assay period. Thus, only 2.29 grams of egg were synthesized per gram of protein consumed compared to 2.65 grams for birds fed the 12 percent protein diet in our studies, Table 2. Assuming that their 10.4 percent protein diet, formulated to meet the aforementioned standard, provided a better pattern of amino acids than the mixture of corn and soybean protein used in our 12 percent diet, these observations would suggest that Johnson and Fisher (1959) might have attained comparable egg production at still lower dietary levels of the same protein at the feed intake reported. The findings and discussion presented herein suggest that the level of feed intake, maturity and physiological status of the bird, rate of lay, and/or various combinations of these factors are indeed pertinent to the interpretation of experiments designed to assy the protein (amino acid) adequacy of diets fed to laying hens.