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Protein, Energy and Method of Feeding as Factors in the Nutrition of Developing White Leghorn Pullets1
158
W. R. BRENEMAN, F. J. ZELLER AND B. E. BEEKMAN
testes weights which were slightly less than the additive effect produced by the hormones when given alone. This was especially noteworthy when the highest dosages of FSH and LH were given. REFERENCES Bates, R. W., and J. P. Schooley, 1942. Studies on the assay of pituitary gonadotropins using the augmentation reaction. Endocrinology, 31: 309317. Bliss, C. I., 1952. The Statistics of Bioassay. p. 448473. Academic Press Inc. Publishers, New York, N. Y. Breneman, W. R., 1945. The gonadotropic activity of the anterior pituitary of cockerels. Endocrinology, 36: 190-199. Breneman, W. R., and R. C. Mason, 1951. Androgen influence on pituitary-gonad interrelationship. Endocrinology, 48: 752-762. Byerly, T. C , and W. H. Burrows, 1938. Chick testis weight response to gonadotropic hormone. Endocrinology, 22: 366-369. Dorfman, R. I., A. S. Dorfman and D. Grim, 1948. Studies on the bioassay of pregnant mare's serum
gonadotrophin. Endocrinology, 42: 93-97. Emmens, C. W., 1950. Hormone Assay, p. 1-33. Academic Press Inc. Publishers, New York, N. Y. Greep, R. 0., H. B. van Dyke and B. F. Chow, 1941. Use of anterior lobe of prostate gland in the assay of metakentrin. Proc. Soc. Exper. Biol. Med. 46: 644-649. Greep, R. O., H. B. van Dyke and B. F. Chow, 1942. Various effects of purified thylakentrin and pure metakentrin. Endocrinology, 30: 635-649. Hays, E. E., and S. L. Steelman, 1955. Chemistry of anterior pituitary hormones. The Hormones I I I : 201-234. Academic Press Inc. Publishers, New York, N. Y. Segal, S. J., 1957. Response of Weaver Finch to chorionic gonadotrophin and hypophysial luteinizing hormone. Science, 126:1242-1243. Snedecor, G. W., 1956. Statistical Methods, 5th Edition. Iowa State College Press, Ames, Iowa. Steelman, S. L., and F. M. Pohley, 1953. Assay of follicle stimulating hormone based on the augmentation with human chorionic gonadotropin. Endocrinology, 53: 504r-616. Witschi, E., 1955. Vertebrate gonadotrophins. Memoirs of the Society for Endocrinology, 4: 149-162.
Protein, Energy and Method of Feeding as Factors in the Nutrition of Developing White Leghorn Pullets1 L A W R E N C E R.
BERG
State College of Washington, Western Washington Experiment Station, Puyallup, Washington (Received for publication June 16, 1958)
P
REVIOUS studies at this station (Berg and Bearse, 1958) have indicated that the protein requirement of developing White Leghorn pullets was not more than 15 percent from 8 to 12 weeks of age, 13 percent from 12 to 16 weeks and 12 percent from 16 to 20 weeks. These results confirmed the findings of Blaylock (1956) who also found that the protein requirement of the developing White Leg1 Scientific Paper No. 1733, Washington Agricultural Experiment Stations, Pullman. Project No. 1241.
horn pullet was less than the level of 16 percent suggested as the requirement by the National Research Council. It was considered desirable to determine the protein requirement of developing pullets with rations of differing energy content and when the diets were fed as all-mash or as mash and whole grain. EXPERIMENTAL
Commercial, July 1957 hatch, straincross White Leghorn pullets were used in the test. The pullets were raised in a new,
159
NUTRITION OF DEVELOPING PULLETS
insulated, windowless, rearing house with controlled ventilation. All chicks were brooded under the same environmental and nutritional regimen to eight weeks of age. Twenty-four groups of 80 eightweek-old pullets each were used in the experiment. The groups were maintained in similar 12X12 ft. pens. From 0 to 10 weeks of age the birds were provided with 14 hours of artificial light daily. This was reduced to 9 hours daily from 10 to 21 weeks of age. Using levels of approximately 1,100 and 1,425 Calories of metabolizable energy per pound, mashes were formulated to approximate 12, 15 and 18 percent protein. The formulas for such rations, to be fed as all-mash rations, are shown in Table 1. As Table 1 shows, chemical analysis determined the rations to be about
1.0 percent higher in protein than calculated. Mashes of similar protein and energy content were formulated to be fed free choice with whole milo, (see footnote 1, Table 1). Mineral and vitamin adjustments made for such rations are indicated in Table 1. The twelve rations were each fed to two randomly selected groups from 8 to 21 weeks of age. Average body weights were determined by group weighings at 8, 12, 16 and 21 weeks of age. Group feed consumption was recorded for the interval between each body weight determination. At about 14 weeks of age, blinder type anti-picking devices were put on each bird. At 21 weeks of age each group was transferred to a 10X20 ft. laying pen having windows and natural ventilation. All
TABLE 1.—Percent composition of all-mash rations1 Developing ; ration Ingredients
1
Ground yellow corn 18.50 Ground barley — Ground oats 50.12 Wheat mixed feed 20.00 Dehydrated grass3 5.00 Herring fish meal (70% protein) 2.50 Meat and bone scrap (50% protein) — Soybean oil meal (44% protein) — Limestone flour 2.23 Steamed bone meal 1.30 Salt 0.35 Inedible tallow — Analysis Determined protein % 13.2 Calculated calcium % 1.4 Calculated phosphorus % 0.7 Calculated Calories metabolizable energy/lb. 4 1,100
2
3
4
5
6
17.00
17.00
80.71
72.71
64.71
—
—
— — —
— — —
— — —
44.40 20.00 5.00 2.50 1.82 6.08 2.20 0.65 0.35
27.02 20.00 5.00 2.50 3.69 12.31 2.13
—
—.
15.9 1.4 0.7
18.9 1.4 0.7
1,100
1,100
—
0.35
5.00 2.50 1.31 4.39 1.53 2.63 0.35 1.00
Laying ration 35.00 41.90
— —
5.00 2.50 3.16 10.54 1.50 1.95 0.35 2.00
5.00 2.50 5.00 16.70 1.47 1.27 0.35 3.00
3.00 2.50 5.00 7.00 3.30 2.00 0.30
12.7 1.6 0.8
15.8 1.6 0.8
18.8 1.6 0.8
15.3 2.5 0.9
1,425
1,425
1,425
1,260
—
1 Mashes fed with whole milo were changed in mineral and vitamin content as follows: The calcium and phosphorus levels of rations similar to 1, 2 and 3 in protein and energy were increased to 2.0 and 1.0 percent, respectively, and in rations similar to 4, 5, and 6 to 2.2 and 1.1 percent. The levels of vitamins A and D and riboflavin were doubled. Nicarbazin was increased by 50 percent. Protein levels determined are shown in Table 2. 2 The following were added per pound to rations 1-6: 700 LIT. vitamin A, 136 I.C.U. vitamin D 3 , 0.5 mg. riboflavin, 57 mg. D.P.P.D., 56 mg. MnSOi, 1 mg. KI and 57 mg. nicarbazin. The laying ration was supplemented with 3401.U. vitamin A, 340 I.C.U. vitamin D 3 ,1.0 mg. riboflavin, 78 mg. MnSC>4,1.5 mg. KI and 2.27 g. sulfaquinoxaline. 3 17% protein and a guarantee of 19 mg. of carotene per 100 grams. 4 Using values of Titus (1957).
\
160
L. R. BERG TABLE 2.—Effect
Calories1 per lb. mash
1,100
1,425
of protein and energy consumed per bird
i of the developing diet on pounds feed experimental periods Age period
% protein in mash
8-21 wks.
21 8 wks.2 wks. to 21-29 to 50% 50% weeks lay lay
8-12 wks.
12-16 wks.
16-21 wks.
Mash Milo
Mash Milo
Mash Milo
Mash
Milo
13.2 12.9
4.22 2.68
.97
5.62 2.92
1.87
6.93 2.51
4.08
16.78 8.11
6.92
5.12 5.87
21.89 20.90
13.89 13.39
15.9 16.2
4.30 2.65
1.20
5.66 2.53
2.26
6.89 2.26
4.23
16.84 7.43
7.69
5.48 5.76
22.32 20.87
13.83 13.59
18.9 18.8
4.03 2.44
1.44
5.52 2.67
2.53
6.96 1.77
4.52
16.50 6.87
8.49
5.30 5.85
21.81 21.21
13.67 13.53
12.7 12.8
3.46 2.90
.63
4.53 3.07
1.43
5.74 3.30
3.36
13.73 9.10
5.40
6.21 6.62
19.93 21.12
13.39 13.44
15.8 16.0
3.48 2.55
.87
4.73 2.79
1.97
5.81 2.56
3.44
14.01 7.89
6.28
5.33 5.69
19.34 19.85
13.51 13.42
18.8 18.8
3.56 2.63
.80
4.67 2.68
2.02
5.57 2.37
3.90
13.80 7.67
6.72
4.79 5.87
18.59 20.25
13.45 13.34
1
Metabolizable calories. From 21 weeks all birds fed same all-mash laying ration containing 15.3 percent protein and 1,260 Calories per pound. 2
24 pens were located in the same house. Artificial light was used to extend light to a 13 hour day. All groups were fed the same all-mash laying ration containing 15.3 percent protein and approximately 1,260 Calories of metabolizable energy per pound (Table 1). Egg production data to 29 weeks of age was obtained. Average weight of eggs was ascertained by group weighing all eggs
laid each Sunday, Tuesday and Thursday. Group body weights were recorded at the conclusion of each four week period. RESULTS AND DISCUSSION
No culling was done during the entire test period from 8 to 29 weeks of age. Total mortality during the test was 1.3 percent. Table 2 presents the amount of feed
TABLE 3.—Analysis of variance of feed consumption data of Table 2 Mean squares for Source of variation Total Treatments Protein level (P) Energy level (E) Mash vs. Mash+Milo (M) PXE PXM EXM PXEXM Error :
d.f.
Total feed 8-21 wks.
Total feed to 50% lay
Total-feed 21-29 wks.
2.4735** .5310 16.3846** .0176 .9279 .5028 6.8586** .0122 .3128
.0628 .0167 .3038** .1768* .0007 .0054 .0888 .0382 .0328
23 11 2 1 1 2 2 1 2 12
2.6097** .0015 20.3320** 1.6276** .0055 .1317 6.2935** .0881 .1421
Significant at the 5 and 1 percent level, respectively.
\
161
NUTRITION OF DEVELOPING PULLETS TABLE 4.—Effect
of protein and energy level of the developing diet on body weight, days to 50% lay, rate of lay and egg weight
Treatment variables Lbs. body weight at Calories % Proper lb. tein in mash mash
1,100
1,425
Whole milo
8 wks. 21 wks. 29 wks.
Age at 50% lay, days
Eggs Egg Egg % lay 29th per bird wt. at wt. 29th to 29 50% lay week week wks. grams grams
13.2 12.9
No Yes
1.43 1.41
2.98 2.98
3.80 3.81
171 175
88.3 87.3
27.7 25.4
46.9 46.2
51.0 50.5
15.9 16.2
No Yes
1.38 1.44
2.95 3.05
3.82 3.87
172 175
90.2 90.7
27.9 26.1
46.9 47.4
50.7 50.8
18.9 18.8
No Yes
1.39 1.45
2.99 3.12
3.74 3.89
172 174
89.4 90.5
28.5 27.8
46.4 47.3
50.9 50.8
12.7 12.8
No Yes
1.43 1.43
2.94 2.96
3.80 3.78
176 177
88.2 86.6
25.4 23.7
47.0 48.6
50.4 51.0
15.8 16.0
No Yes
1.44 1.42
3.03 3.05
3.81 3.84
173 174
88.2 91.5
26.9 26.3
46.3 47.4
50.4 50.4
18.8 18.8
No Yes
1.42 1.42
2.98 3.08
3.80 3.82
171 175
92.0 91.4
28.9 26.3
46.0 47.4
50.1 50.5
consumed per bird during different age periods with the different rations. The effect of the developing diets on body weight, age at 50 percent lay, rate of lay and egg weight are shown in Table 4. Tables 3 and 5 show the analysis of variance of the data presented. Decreasing the energy content of the ration from approximately 1,425 Calories of metabolizable energy per pound to
1,100 Calories increased feed consumption about 20 percent. This amounts to approximately a 6.15 percent increase in consumption for each decrease of 100 Calories in the diet. This result agrees with the value of 6.17 percent per 100 Calories observed at this station with laying hens (Berge* al., 1956). Protein level of the ration had no effect on the amount of feed eaten per bird. This
TABLE 5.—Analysis of variance of data shown in Table 4 Mean squares for Source of variation
d.f.
Total 23 Treatments 11 Protein level (P) 2 Energy level (E) 1 Mash vs. mash+milo (M) 1 PXE 2 PXM 2 EXM 1 PXEXM 2 Error 12 :
Egg Egg Body wt. Body Days to % l a y Eggs/bird wt. at wt. at wt. 29 21 wks. wks. 50% lay 29th wk. to 29 wks. 50% 29th lay wk. .0059* .0124** .0002 .0210** .0026 .0053 .0010 .0012 .0016
.0031 8.64** .0027 6.00 .0008 14.00* .0096 43.00** .0002 9.50* .0045 .50 .0054 1.00 .0016 2.50 .0032 1.75
Significant at the 5 and 1 percent level, respectively.
6.35 23.42** .48 .50 3.40 4.83 .07 5.51 2.50
4.5845** 10.8028** 5.8411* 15.9088** 1.6482 .3147 .0081 1.5701 .8092
1.03 .37 .48 3.68* 1.49 .25 1.82 .59 .75
.16 .06 .51 .07 .13 .01 .46 .18 .14
162
L. R.
was true with both energy levels and with both the all-mash and mash-whole grain systems of feeding. Evidently the protein level of the lowest protein rations was high enough to prevent an increase in appetite caused by an amino acid or protein deficiency. With the 1,100 Calorie mashes, the birds fed by the mash-whole milo system ate about 1.5 pounds less feed during the 8-21 week period than those fed the allmash diets. This decreased consumption with the mash-whole milo system of feeding was true for each protein level and for each of the experimental periods 8-12, 1216 and 16-21 weeks of age. In contrast, with the 1,425 Calorie mashes, pullets fed by the mash-whole milo system ate about 0.5 pound more feed per bird during the 8-21 week period than those fed mash only. Whereas the birds tended to consume less feed on the mash-whole milo system during each of the three periods on the low energy diet, with the high energy diet consumption increased only during the 16-21 week period. During the 8-12 and 12-16 week periods, feed consumption was the same with both systems of feeding. Statistical treatment of the 8-21 week feed consumption data showed significance at the 1.0 percent level of probability for differences resulting from energy level and method of feeding and for the interaction between energy level and method of feeding. During the interval from 21 to 29 weeks of age, when all of the birds were fed the same all-mash laying ration, the energy level of the developing mash and the method of feeding during the developing period exerted some influence on the amount of feed consumed. The birds raised on the 1,425 Calorie diet consumed an average of 13.4 pounds of the laying ration as compared with 13.7 pounds for those fed the 1,100 Calorie diet. This dif-
BERG
ference was significant at the 1.0 percent level. Birds raised on the mash-grain system also tended to eat less feed during the early laying period. The average difference of 0.2 pound per bird for the eight week period was significant at the 5.0 percent level of probability. Among those treatments in which the birds had access to mash and whole milo, the percentage of the total ration consumed as whole milo increased as the level of protein increased. This was true with both levels of energy. Likewise in each of the periods, (8-12, 12-16 and 16-21 weeks) the percent of the ration eaten as whole milo increased. Table 6 shows the approximate levels of protein and energy in the rations consumed by the birds fed mash and whole milo as compared with those fed the allmash diets. Increasing protein levels of the mash with the free choice system of feeding resulted in increased body weights at 21 weeks of age. The average weights with the 13 and 18.8 percent protein mashes were 2.97 and 3.10 pounds, respectively. A similar trend was not as evident with the all-mash rations. The increased weight gains resulting with each greater protein level of the mash with the mash-milo system do not seem to be due to the increased Calories resulting from the milo consumption because no similar protein effect was noted with either the high or low energy level in the all-mash diets. If energy level or energy-protein ratios of the diets are involved in the differences between the allmash and mash-grain system in ability to promote weight gains the fact would indicate that the developing pullet can select the correct proportion of mash to whole grain to provide the desirable ratio of nutrients for body weight increases. The birds fed mash and milo were heavier than those fed by the all-mash system
NUTRITION OF DEVELOPING PULLETS
163
TABLE 6.—Protein and energy content and C/P ratios of diets consumed during experimental periods Treatment variables
8-12 weeks
12-16 weeks 3
Calo- % ries1 Pro. Whole per lb. in milo mash mash
% Pro. 2 total ration
Cal./ lb.. total ration
C/P ratio total ration
% Pro. total ration
Cal./ lb. total ration
C/P ratio total ration
% Pro. total ration
Cal./ lb. total ration
C/P ratio total ration
13.2 12.9
No Yes
13.2 12.3
1,100 1,220
83 100
13.2 12.0
1,100 1,276
83 107
13.2 11.8
1,100 1,308
83 111
15.9 16.2
No Yes
15.9 14.4
1,100 1,241
69 86
15.9 13.5
1,100 1,314
69 97
15.9 13.3
1,100 1,330
69 100
18.9 18.8
No Yes
18.9 15.7
1,100 1,268
58 " 81
18.9 14.8
1,100 1,320
58 89
18.9 14.2
1,100 1,350
58 95
12.7 12.8
No Yes
12.7 12.4
1,425 1.448
112 117
12.7 12.1
1,425 1,465
112 121
12.7 11.9
1,425 1,472
112 123
15.8 16.0
No Yes
15.8 14.6
1,425 1,457
90 100
15.8 13.7
1,425 1,478
90 108
15.8 13.6
1,425 1,481
90 109
18.8 18.8
No Yes
18.8 16.9
1,425 1,455
76 86
18.8 15.2
1,425 1,480
76 97
18.8 14.9
1,425 1,484
76 99
1,100
1,425
1 2 3
Metabolizable energy calculated. Whole milo was calculated at 10.5 percent protein. C/P ratio refers to Calories of metabolizable energy per pound/percent protein in the diet.
(P<.01). Energy level of the developing mashes had no effect on the rate of body weight increases. When the birds were 29 weeks old, after having been on the same laying ration for eight weeks, none of the developing rations had any effect on body weight. The protein levels of the 1,100 Calorie all-mash rations had no effect on the average age of the pullets when they attained 50 percent production. With 1,425 Calorie diets, increasing the level of protein decreased the days required to 50 percent lay. The birds fed the higher energy mashes required an average of one day longer to reach 50 percent lay. Practically all of this increase was due to the increased time required by the birds on the lowest protein diets. The interaction between protein and energy levels was significant at the 5 percent level. With each protein and energy level of the mash, giving the birds access to whole milo increased the time to reach 50 percent lay.
)
16-21 weeks
The average delay over the entire experiment was 2.5 days, (P<.01). The groups attained peak production during the 28th and 29th weeks of age. The average rate of lay on the various treatments during the 29th week varied from 86.6 to 91.5 percent (Table 4). Neither energy level of the developing diet nor method of feeding during the developing period had any statistically significant effect on the rate of peak production attained. However, the peak production of the pullets fed the lowest protein mashes averaged about 2.0 percent lower than that of those fed the higher protein diets, (P<.01). To the age of 29 weeks the pullets fed the low energy developing mashes had laid an average of one egg more per bird than those fed the high energy mashes (P<.05). Those fed by the all-mash system had produced 1.5 more eggs per bird than those fed mash and whole milo (P<.01). With the three protein levels of
164
L. R.
the developing mash, each increasing increment resulted in an average increase of 0.75 eggs per bird (P<.01). Neither protein nor energy level of the developing diet had any effect on weight of eggs produced when the birds attained 50 percent lay or at peak production (29th week of age). These results support previous findings from this station, (Berg and Bearse, 1958). When the birds reached 50 percent lay, the eggs produced by the pullets fed mash and milo averaged about 1.0 gram heavier than those which had been fed all-mash (P<.05). This result can probably be associated with the increased age and size of these birds when 50 percent lay was attained. This effect of method of feeding was not present with the eggs laid during the 29th week. The results of the present test support previous findings from this station (Berg and Bearse, 1958) which showed that giving birds from 8 to 20 weeks of age a free choice ration of mash and whole grain delays age to 50 percent lay by two to four days when compared with an all-mash diet. In the present test this was true whether the mash portion of the diet contained 1,100 or 1,425 Calories of metabolizable energy per pound. The increase in days to 50 percent production owing to feeding whole milo was similar with mashes differing widely in energy content. Therefore the effect of the milo consumed would not seem to be due to the resulting increase in energy content of the feed. Likewise, the effect of milo feeding was not necessarily due to a reduction in quantity of protein consumed. This fact is evident when the mash-milo diets with 1,100 Calories and 16.2 and 18.8 percent protein in the mash are compared with the 13.2 percent all-mash ration. With these two mash-milo diets, the percent protein of the total consumed rations was greater
BERG
than with the all-mash diet, but more days were required to reach 50 percent lay. The milo did change the amino acid composition of the total ration consumed from that of the all-mash diets and may have been responsible for the delayed onset of egg production. Changes in mineral and vitamin content of the total ration resulting from milo consumption should not have affected these results because these materials were increased in the mash portion of these rations to compensate for the decreased mash consumption. Previous results (Berg and Bearse, 1958) indicated that developing pullets do not require more than 15 percent protein from 8 to 12 weeks, not more than 13 percent from 12 to 16 weeks and less than 12 percent from 16 to 20 weeks. In the present test, pullets fed all-mash diets containing 13.2 percent protein gained in body weight as rapidly, attained 50 percent lay as soon, and laid practically the same number of eggs per bird to 29 weeks of age as birds fed rations containing 15.9 or 18.9 percent protein when the rations contained approximately 1,100 Calories of metabolizable energy per pound. Although the birds on the low protein diet had a peak production 1.0 to 2.0 percent lower than those on the higher protein diets, the rate of 88.3 percent must be considered satisfactory. Thus it is concluded that the protein requirement, during the period from 8 to 21 weeks, of White Leghorn pullets such as used in this test is not over 13.2 percent with diets containing 1,100 Calories per pound. The results obtained with the 12,9 percent protein1,100 Calorie mash fed free choice with milo showed that pullets will gain in weight as well and enter production nearly as rapidly with approximately 12.0 percent protein as with higher levels. The increase in time required to reach 50 percent lay as the level of protein de-
I
N U T R I T I O N OF D E V E L O P I N G P U L L E T S
creased from 18.8 to 15.8 to 12.7 percent with diets containing 1,425 Calories per pound indicate t h a t the protein requirement with this level of energy may be higher t h a n with the lower energy level. I t is interesting to note, however, t h a t the pullets fed the high energy diet with only 12.7 percent protein made weight gains similar to those made with higher protein levels and had a peak production of 88 percent. In this test the pullets made practically the same progress in development with widely varying Calorie/Protein ratios (Table 4). With the all-mash 1,100 Calorie diets the ratios varied from 58/1 to 8 3 / 1 . When the birds were given access to whole milo the birds increased the ratio to as high as 111/1 during the 16-21 week period. The C / P ratio of the diet does not appear to be as critical for the developing pullets as it is for the younger chick, Combs (1955), Vondell and Ringrose (1958). SUMMARY A 3 X 2 X 2 factorial experiment involving levels of approximately 13, 16 and 19 percent protein and 1,100 and 1,425 Calories of metabolizable energy per pound in the mash with two systems of feeding (all-mash and m a s h + w h o l e milo free choice) was conducted with White Leghorn pullets from 8 to 21 weeks of age. The effect of these treatments on ability of the pullets to enter production was determined by feeding all birds the same laying mash containing 15.3 percent protein and approximately 1,260 Calories per pound from 21 to 29 weeks of age. The results of the study show t h a t energy level of the developing rations had no effect on body weight gains, rate of peak production or size of eggs produced. With protein levels of 12.7 percent or
165
less, the high energy diet increased days to 50 percent lay. Energy content of the diet had no effect on age at 50 percent lay with protein levels of 13.7 percent or higher. Giving the pullets free access to whole milo with mash caused an increase in days to 50 percent lay, increased body weight at 21 weeks of age but had no effect on peak rate of lay. With the low energy mashes, feeding whole milo resulted in a decrease in total feed consumed, whereas with the high energy mashes it caused an increase in the amount of feed eaten. With pullets fed all-mash rations, 13.0 percent protein in the developing diet resulted in body weights and egg size equal to t h a t obtained with higher protein levels. This low protein level permitted the attainment of a peak production rate of 88 percent. With the mash and milo system of feeding, increasing protein level resulted in increased body weight. With this system of feeding, consumption of rations with 12 percent protein resulted in a peak production of 87 percent. REFERENCES Berg, L. R., G. E. Bearse, R. S. Hansen, L. S. Jensen and J. McGinnis, 1956. Energy level of the diet for laying hens in Western Washington. Washington Agri. Exp. Sta. Tech. Bull. 22, pp. 1-25. Berg, L. R., and G. E. Bearse, 1958. Protein and energy studies with developing White Leghorn pullets. Poultry Sci. 37: 1340-1346. Blaylock, L. G., 1956. The protein requirement of growing birds. Poultry Sci. 35: 1133. Combs, G. F., 1955. Energy-protein ratio approach for poultry feed formulation. Flour and Feed. Aug. 1955, p. 4-5. Titus, H. W., 1957. Energy values of feedstuffs for poultry. Unpublished mimeographed material, 14 pp. Vondell, R. M., and R. C. Ringrose, 1958. The effect of protein and fat levels and calorie to protein ratio upon performance of broilers. Poultry Sci. 37: 147-151.
W. R. BRENEMAN, F. J. ZELLER AND B. E. BEEKMAN
testes weights which were slightly less than the additive effect produced by the hormones when given alone. This was especially noteworthy when the highest dosages of FSH and LH were given. REFERENCES Bates, R. W., and J. P. Schooley, 1942. Studies on the assay of pituitary gonadotropins using the augmentation reaction. Endocrinology, 31: 309317. Bliss, C. I., 1952. The Statistics of Bioassay. p. 448473. Academic Press Inc. Publishers, New York, N. Y. Breneman, W. R., 1945. The gonadotropic activity of the anterior pituitary of cockerels. Endocrinology, 36: 190-199. Breneman, W. R., and R. C. Mason, 1951. Androgen influence on pituitary-gonad interrelationship. Endocrinology, 48: 752-762. Byerly, T. C , and W. H. Burrows, 1938. Chick testis weight response to gonadotropic hormone. Endocrinology, 22: 366-369. Dorfman, R. I., A. S. Dorfman and D. Grim, 1948. Studies on the bioassay of pregnant mare's serum
gonadotrophin. Endocrinology, 42: 93-97. Emmens, C. W., 1950. Hormone Assay, p. 1-33. Academic Press Inc. Publishers, New York, N. Y. Greep, R. 0., H. B. van Dyke and B. F. Chow, 1941. Use of anterior lobe of prostate gland in the assay of metakentrin. Proc. Soc. Exper. Biol. Med. 46: 644-649. Greep, R. O., H. B. van Dyke and B. F. Chow, 1942. Various effects of purified thylakentrin and pure metakentrin. Endocrinology, 30: 635-649. Hays, E. E., and S. L. Steelman, 1955. Chemistry of anterior pituitary hormones. The Hormones I I I : 201-234. Academic Press Inc. Publishers, New York, N. Y. Segal, S. J., 1957. Response of Weaver Finch to chorionic gonadotrophin and hypophysial luteinizing hormone. Science, 126:1242-1243. Snedecor, G. W., 1956. Statistical Methods, 5th Edition. Iowa State College Press, Ames, Iowa. Steelman, S. L., and F. M. Pohley, 1953. Assay of follicle stimulating hormone based on the augmentation with human chorionic gonadotropin. Endocrinology, 53: 504r-616. Witschi, E., 1955. Vertebrate gonadotrophins. Memoirs of the Society for Endocrinology, 4: 149-162.
Protein, Energy and Method of Feeding as Factors in the Nutrition of Developing White Leghorn Pullets1 L A W R E N C E R.
BERG
State College of Washington, Western Washington Experiment Station, Puyallup, Washington (Received for publication June 16, 1958)
P
REVIOUS studies at this station (Berg and Bearse, 1958) have indicated that the protein requirement of developing White Leghorn pullets was not more than 15 percent from 8 to 12 weeks of age, 13 percent from 12 to 16 weeks and 12 percent from 16 to 20 weeks. These results confirmed the findings of Blaylock (1956) who also found that the protein requirement of the developing White Leg1 Scientific Paper No. 1733, Washington Agricultural Experiment Stations, Pullman. Project No. 1241.
horn pullet was less than the level of 16 percent suggested as the requirement by the National Research Council. It was considered desirable to determine the protein requirement of developing pullets with rations of differing energy content and when the diets were fed as all-mash or as mash and whole grain. EXPERIMENTAL
Commercial, July 1957 hatch, straincross White Leghorn pullets were used in the test. The pullets were raised in a new,
159
NUTRITION OF DEVELOPING PULLETS
insulated, windowless, rearing house with controlled ventilation. All chicks were brooded under the same environmental and nutritional regimen to eight weeks of age. Twenty-four groups of 80 eightweek-old pullets each were used in the experiment. The groups were maintained in similar 12X12 ft. pens. From 0 to 10 weeks of age the birds were provided with 14 hours of artificial light daily. This was reduced to 9 hours daily from 10 to 21 weeks of age. Using levels of approximately 1,100 and 1,425 Calories of metabolizable energy per pound, mashes were formulated to approximate 12, 15 and 18 percent protein. The formulas for such rations, to be fed as all-mash rations, are shown in Table 1. As Table 1 shows, chemical analysis determined the rations to be about
1.0 percent higher in protein than calculated. Mashes of similar protein and energy content were formulated to be fed free choice with whole milo, (see footnote 1, Table 1). Mineral and vitamin adjustments made for such rations are indicated in Table 1. The twelve rations were each fed to two randomly selected groups from 8 to 21 weeks of age. Average body weights were determined by group weighings at 8, 12, 16 and 21 weeks of age. Group feed consumption was recorded for the interval between each body weight determination. At about 14 weeks of age, blinder type anti-picking devices were put on each bird. At 21 weeks of age each group was transferred to a 10X20 ft. laying pen having windows and natural ventilation. All
TABLE 1.—Percent composition of all-mash rations1 Developing ; ration Ingredients
1
Ground yellow corn 18.50 Ground barley — Ground oats 50.12 Wheat mixed feed 20.00 Dehydrated grass3 5.00 Herring fish meal (70% protein) 2.50 Meat and bone scrap (50% protein) — Soybean oil meal (44% protein) — Limestone flour 2.23 Steamed bone meal 1.30 Salt 0.35 Inedible tallow — Analysis Determined protein % 13.2 Calculated calcium % 1.4 Calculated phosphorus % 0.7 Calculated Calories metabolizable energy/lb. 4 1,100
2
3
4
5
6
17.00
17.00
80.71
72.71
64.71
—
—
— — —
— — —
— — —
44.40 20.00 5.00 2.50 1.82 6.08 2.20 0.65 0.35
27.02 20.00 5.00 2.50 3.69 12.31 2.13
—
—.
15.9 1.4 0.7
18.9 1.4 0.7
1,100
1,100
—
0.35
5.00 2.50 1.31 4.39 1.53 2.63 0.35 1.00
Laying ration 35.00 41.90
— —
5.00 2.50 3.16 10.54 1.50 1.95 0.35 2.00
5.00 2.50 5.00 16.70 1.47 1.27 0.35 3.00
3.00 2.50 5.00 7.00 3.30 2.00 0.30
12.7 1.6 0.8
15.8 1.6 0.8
18.8 1.6 0.8
15.3 2.5 0.9
1,425
1,425
1,425
1,260
—
1 Mashes fed with whole milo were changed in mineral and vitamin content as follows: The calcium and phosphorus levels of rations similar to 1, 2 and 3 in protein and energy were increased to 2.0 and 1.0 percent, respectively, and in rations similar to 4, 5, and 6 to 2.2 and 1.1 percent. The levels of vitamins A and D and riboflavin were doubled. Nicarbazin was increased by 50 percent. Protein levels determined are shown in Table 2. 2 The following were added per pound to rations 1-6: 700 LIT. vitamin A, 136 I.C.U. vitamin D 3 , 0.5 mg. riboflavin, 57 mg. D.P.P.D., 56 mg. MnSOi, 1 mg. KI and 57 mg. nicarbazin. The laying ration was supplemented with 3401.U. vitamin A, 340 I.C.U. vitamin D 3 ,1.0 mg. riboflavin, 78 mg. MnSC>4,1.5 mg. KI and 2.27 g. sulfaquinoxaline. 3 17% protein and a guarantee of 19 mg. of carotene per 100 grams. 4 Using values of Titus (1957).
\
160
L. R. BERG TABLE 2.—Effect
Calories1 per lb. mash
1,100
1,425
of protein and energy consumed per bird
i of the developing diet on pounds feed experimental periods Age period
% protein in mash
8-21 wks.
21 8 wks.2 wks. to 21-29 to 50% 50% weeks lay lay
8-12 wks.
12-16 wks.
16-21 wks.
Mash Milo
Mash Milo
Mash Milo
Mash
Milo
13.2 12.9
4.22 2.68
.97
5.62 2.92
1.87
6.93 2.51
4.08
16.78 8.11
6.92
5.12 5.87
21.89 20.90
13.89 13.39
15.9 16.2
4.30 2.65
1.20
5.66 2.53
2.26
6.89 2.26
4.23
16.84 7.43
7.69
5.48 5.76
22.32 20.87
13.83 13.59
18.9 18.8
4.03 2.44
1.44
5.52 2.67
2.53
6.96 1.77
4.52
16.50 6.87
8.49
5.30 5.85
21.81 21.21
13.67 13.53
12.7 12.8
3.46 2.90
.63
4.53 3.07
1.43
5.74 3.30
3.36
13.73 9.10
5.40
6.21 6.62
19.93 21.12
13.39 13.44
15.8 16.0
3.48 2.55
.87
4.73 2.79
1.97
5.81 2.56
3.44
14.01 7.89
6.28
5.33 5.69
19.34 19.85
13.51 13.42
18.8 18.8
3.56 2.63
.80
4.67 2.68
2.02
5.57 2.37
3.90
13.80 7.67
6.72
4.79 5.87
18.59 20.25
13.45 13.34
1
Metabolizable calories. From 21 weeks all birds fed same all-mash laying ration containing 15.3 percent protein and 1,260 Calories per pound. 2
24 pens were located in the same house. Artificial light was used to extend light to a 13 hour day. All groups were fed the same all-mash laying ration containing 15.3 percent protein and approximately 1,260 Calories of metabolizable energy per pound (Table 1). Egg production data to 29 weeks of age was obtained. Average weight of eggs was ascertained by group weighing all eggs
laid each Sunday, Tuesday and Thursday. Group body weights were recorded at the conclusion of each four week period. RESULTS AND DISCUSSION
No culling was done during the entire test period from 8 to 29 weeks of age. Total mortality during the test was 1.3 percent. Table 2 presents the amount of feed
TABLE 3.—Analysis of variance of feed consumption data of Table 2 Mean squares for Source of variation Total Treatments Protein level (P) Energy level (E) Mash vs. Mash+Milo (M) PXE PXM EXM PXEXM Error :
d.f.
Total feed 8-21 wks.
Total feed to 50% lay
Total-feed 21-29 wks.
2.4735** .5310 16.3846** .0176 .9279 .5028 6.8586** .0122 .3128
.0628 .0167 .3038** .1768* .0007 .0054 .0888 .0382 .0328
23 11 2 1 1 2 2 1 2 12
2.6097** .0015 20.3320** 1.6276** .0055 .1317 6.2935** .0881 .1421
Significant at the 5 and 1 percent level, respectively.
\
161
NUTRITION OF DEVELOPING PULLETS TABLE 4.—Effect
of protein and energy level of the developing diet on body weight, days to 50% lay, rate of lay and egg weight
Treatment variables Lbs. body weight at Calories % Proper lb. tein in mash mash
1,100
1,425
Whole milo
8 wks. 21 wks. 29 wks.
Age at 50% lay, days
Eggs Egg Egg % lay 29th per bird wt. at wt. 29th to 29 50% lay week week wks. grams grams
13.2 12.9
No Yes
1.43 1.41
2.98 2.98
3.80 3.81
171 175
88.3 87.3
27.7 25.4
46.9 46.2
51.0 50.5
15.9 16.2
No Yes
1.38 1.44
2.95 3.05
3.82 3.87
172 175
90.2 90.7
27.9 26.1
46.9 47.4
50.7 50.8
18.9 18.8
No Yes
1.39 1.45
2.99 3.12
3.74 3.89
172 174
89.4 90.5
28.5 27.8
46.4 47.3
50.9 50.8
12.7 12.8
No Yes
1.43 1.43
2.94 2.96
3.80 3.78
176 177
88.2 86.6
25.4 23.7
47.0 48.6
50.4 51.0
15.8 16.0
No Yes
1.44 1.42
3.03 3.05
3.81 3.84
173 174
88.2 91.5
26.9 26.3
46.3 47.4
50.4 50.4
18.8 18.8
No Yes
1.42 1.42
2.98 3.08
3.80 3.82
171 175
92.0 91.4
28.9 26.3
46.0 47.4
50.1 50.5
consumed per bird during different age periods with the different rations. The effect of the developing diets on body weight, age at 50 percent lay, rate of lay and egg weight are shown in Table 4. Tables 3 and 5 show the analysis of variance of the data presented. Decreasing the energy content of the ration from approximately 1,425 Calories of metabolizable energy per pound to
1,100 Calories increased feed consumption about 20 percent. This amounts to approximately a 6.15 percent increase in consumption for each decrease of 100 Calories in the diet. This result agrees with the value of 6.17 percent per 100 Calories observed at this station with laying hens (Berge* al., 1956). Protein level of the ration had no effect on the amount of feed eaten per bird. This
TABLE 5.—Analysis of variance of data shown in Table 4 Mean squares for Source of variation
d.f.
Total 23 Treatments 11 Protein level (P) 2 Energy level (E) 1 Mash vs. mash+milo (M) 1 PXE 2 PXM 2 EXM 1 PXEXM 2 Error 12 :
Egg Egg Body wt. Body Days to % l a y Eggs/bird wt. at wt. at wt. 29 21 wks. wks. 50% lay 29th wk. to 29 wks. 50% 29th lay wk. .0059* .0124** .0002 .0210** .0026 .0053 .0010 .0012 .0016
.0031 8.64** .0027 6.00 .0008 14.00* .0096 43.00** .0002 9.50* .0045 .50 .0054 1.00 .0016 2.50 .0032 1.75
Significant at the 5 and 1 percent level, respectively.
6.35 23.42** .48 .50 3.40 4.83 .07 5.51 2.50
4.5845** 10.8028** 5.8411* 15.9088** 1.6482 .3147 .0081 1.5701 .8092
1.03 .37 .48 3.68* 1.49 .25 1.82 .59 .75
.16 .06 .51 .07 .13 .01 .46 .18 .14
162
L. R.
was true with both energy levels and with both the all-mash and mash-whole grain systems of feeding. Evidently the protein level of the lowest protein rations was high enough to prevent an increase in appetite caused by an amino acid or protein deficiency. With the 1,100 Calorie mashes, the birds fed by the mash-whole milo system ate about 1.5 pounds less feed during the 8-21 week period than those fed the allmash diets. This decreased consumption with the mash-whole milo system of feeding was true for each protein level and for each of the experimental periods 8-12, 1216 and 16-21 weeks of age. In contrast, with the 1,425 Calorie mashes, pullets fed by the mash-whole milo system ate about 0.5 pound more feed per bird during the 8-21 week period than those fed mash only. Whereas the birds tended to consume less feed on the mash-whole milo system during each of the three periods on the low energy diet, with the high energy diet consumption increased only during the 16-21 week period. During the 8-12 and 12-16 week periods, feed consumption was the same with both systems of feeding. Statistical treatment of the 8-21 week feed consumption data showed significance at the 1.0 percent level of probability for differences resulting from energy level and method of feeding and for the interaction between energy level and method of feeding. During the interval from 21 to 29 weeks of age, when all of the birds were fed the same all-mash laying ration, the energy level of the developing mash and the method of feeding during the developing period exerted some influence on the amount of feed consumed. The birds raised on the 1,425 Calorie diet consumed an average of 13.4 pounds of the laying ration as compared with 13.7 pounds for those fed the 1,100 Calorie diet. This dif-
BERG
ference was significant at the 1.0 percent level. Birds raised on the mash-grain system also tended to eat less feed during the early laying period. The average difference of 0.2 pound per bird for the eight week period was significant at the 5.0 percent level of probability. Among those treatments in which the birds had access to mash and whole milo, the percentage of the total ration consumed as whole milo increased as the level of protein increased. This was true with both levels of energy. Likewise in each of the periods, (8-12, 12-16 and 16-21 weeks) the percent of the ration eaten as whole milo increased. Table 6 shows the approximate levels of protein and energy in the rations consumed by the birds fed mash and whole milo as compared with those fed the allmash diets. Increasing protein levels of the mash with the free choice system of feeding resulted in increased body weights at 21 weeks of age. The average weights with the 13 and 18.8 percent protein mashes were 2.97 and 3.10 pounds, respectively. A similar trend was not as evident with the all-mash rations. The increased weight gains resulting with each greater protein level of the mash with the mash-milo system do not seem to be due to the increased Calories resulting from the milo consumption because no similar protein effect was noted with either the high or low energy level in the all-mash diets. If energy level or energy-protein ratios of the diets are involved in the differences between the allmash and mash-grain system in ability to promote weight gains the fact would indicate that the developing pullet can select the correct proportion of mash to whole grain to provide the desirable ratio of nutrients for body weight increases. The birds fed mash and milo were heavier than those fed by the all-mash system
NUTRITION OF DEVELOPING PULLETS
163
TABLE 6.—Protein and energy content and C/P ratios of diets consumed during experimental periods Treatment variables
8-12 weeks
12-16 weeks 3
Calo- % ries1 Pro. Whole per lb. in milo mash mash
% Pro. 2 total ration
Cal./ lb.. total ration
C/P ratio total ration
% Pro. total ration
Cal./ lb. total ration
C/P ratio total ration
% Pro. total ration
Cal./ lb. total ration
C/P ratio total ration
13.2 12.9
No Yes
13.2 12.3
1,100 1,220
83 100
13.2 12.0
1,100 1,276
83 107
13.2 11.8
1,100 1,308
83 111
15.9 16.2
No Yes
15.9 14.4
1,100 1,241
69 86
15.9 13.5
1,100 1,314
69 97
15.9 13.3
1,100 1,330
69 100
18.9 18.8
No Yes
18.9 15.7
1,100 1,268
58 " 81
18.9 14.8
1,100 1,320
58 89
18.9 14.2
1,100 1,350
58 95
12.7 12.8
No Yes
12.7 12.4
1,425 1.448
112 117
12.7 12.1
1,425 1,465
112 121
12.7 11.9
1,425 1,472
112 123
15.8 16.0
No Yes
15.8 14.6
1,425 1,457
90 100
15.8 13.7
1,425 1,478
90 108
15.8 13.6
1,425 1,481
90 109
18.8 18.8
No Yes
18.8 16.9
1,425 1,455
76 86
18.8 15.2
1,425 1,480
76 97
18.8 14.9
1,425 1,484
76 99
1,100
1,425
1 2 3
Metabolizable energy calculated. Whole milo was calculated at 10.5 percent protein. C/P ratio refers to Calories of metabolizable energy per pound/percent protein in the diet.
(P<.01). Energy level of the developing mashes had no effect on the rate of body weight increases. When the birds were 29 weeks old, after having been on the same laying ration for eight weeks, none of the developing rations had any effect on body weight. The protein levels of the 1,100 Calorie all-mash rations had no effect on the average age of the pullets when they attained 50 percent production. With 1,425 Calorie diets, increasing the level of protein decreased the days required to 50 percent lay. The birds fed the higher energy mashes required an average of one day longer to reach 50 percent lay. Practically all of this increase was due to the increased time required by the birds on the lowest protein diets. The interaction between protein and energy levels was significant at the 5 percent level. With each protein and energy level of the mash, giving the birds access to whole milo increased the time to reach 50 percent lay.
)
16-21 weeks
The average delay over the entire experiment was 2.5 days, (P<.01). The groups attained peak production during the 28th and 29th weeks of age. The average rate of lay on the various treatments during the 29th week varied from 86.6 to 91.5 percent (Table 4). Neither energy level of the developing diet nor method of feeding during the developing period had any statistically significant effect on the rate of peak production attained. However, the peak production of the pullets fed the lowest protein mashes averaged about 2.0 percent lower than that of those fed the higher protein diets, (P<.01). To the age of 29 weeks the pullets fed the low energy developing mashes had laid an average of one egg more per bird than those fed the high energy mashes (P<.05). Those fed by the all-mash system had produced 1.5 more eggs per bird than those fed mash and whole milo (P<.01). With the three protein levels of
164
L. R.
the developing mash, each increasing increment resulted in an average increase of 0.75 eggs per bird (P<.01). Neither protein nor energy level of the developing diet had any effect on weight of eggs produced when the birds attained 50 percent lay or at peak production (29th week of age). These results support previous findings from this station, (Berg and Bearse, 1958). When the birds reached 50 percent lay, the eggs produced by the pullets fed mash and milo averaged about 1.0 gram heavier than those which had been fed all-mash (P<.05). This result can probably be associated with the increased age and size of these birds when 50 percent lay was attained. This effect of method of feeding was not present with the eggs laid during the 29th week. The results of the present test support previous findings from this station (Berg and Bearse, 1958) which showed that giving birds from 8 to 20 weeks of age a free choice ration of mash and whole grain delays age to 50 percent lay by two to four days when compared with an all-mash diet. In the present test this was true whether the mash portion of the diet contained 1,100 or 1,425 Calories of metabolizable energy per pound. The increase in days to 50 percent production owing to feeding whole milo was similar with mashes differing widely in energy content. Therefore the effect of the milo consumed would not seem to be due to the resulting increase in energy content of the feed. Likewise, the effect of milo feeding was not necessarily due to a reduction in quantity of protein consumed. This fact is evident when the mash-milo diets with 1,100 Calories and 16.2 and 18.8 percent protein in the mash are compared with the 13.2 percent all-mash ration. With these two mash-milo diets, the percent protein of the total consumed rations was greater
BERG
than with the all-mash diet, but more days were required to reach 50 percent lay. The milo did change the amino acid composition of the total ration consumed from that of the all-mash diets and may have been responsible for the delayed onset of egg production. Changes in mineral and vitamin content of the total ration resulting from milo consumption should not have affected these results because these materials were increased in the mash portion of these rations to compensate for the decreased mash consumption. Previous results (Berg and Bearse, 1958) indicated that developing pullets do not require more than 15 percent protein from 8 to 12 weeks, not more than 13 percent from 12 to 16 weeks and less than 12 percent from 16 to 20 weeks. In the present test, pullets fed all-mash diets containing 13.2 percent protein gained in body weight as rapidly, attained 50 percent lay as soon, and laid practically the same number of eggs per bird to 29 weeks of age as birds fed rations containing 15.9 or 18.9 percent protein when the rations contained approximately 1,100 Calories of metabolizable energy per pound. Although the birds on the low protein diet had a peak production 1.0 to 2.0 percent lower than those on the higher protein diets, the rate of 88.3 percent must be considered satisfactory. Thus it is concluded that the protein requirement, during the period from 8 to 21 weeks, of White Leghorn pullets such as used in this test is not over 13.2 percent with diets containing 1,100 Calories per pound. The results obtained with the 12,9 percent protein1,100 Calorie mash fed free choice with milo showed that pullets will gain in weight as well and enter production nearly as rapidly with approximately 12.0 percent protein as with higher levels. The increase in time required to reach 50 percent lay as the level of protein de-
I
N U T R I T I O N OF D E V E L O P I N G P U L L E T S
creased from 18.8 to 15.8 to 12.7 percent with diets containing 1,425 Calories per pound indicate t h a t the protein requirement with this level of energy may be higher t h a n with the lower energy level. I t is interesting to note, however, t h a t the pullets fed the high energy diet with only 12.7 percent protein made weight gains similar to those made with higher protein levels and had a peak production of 88 percent. In this test the pullets made practically the same progress in development with widely varying Calorie/Protein ratios (Table 4). With the all-mash 1,100 Calorie diets the ratios varied from 58/1 to 8 3 / 1 . When the birds were given access to whole milo the birds increased the ratio to as high as 111/1 during the 16-21 week period. The C / P ratio of the diet does not appear to be as critical for the developing pullets as it is for the younger chick, Combs (1955), Vondell and Ringrose (1958). SUMMARY A 3 X 2 X 2 factorial experiment involving levels of approximately 13, 16 and 19 percent protein and 1,100 and 1,425 Calories of metabolizable energy per pound in the mash with two systems of feeding (all-mash and m a s h + w h o l e milo free choice) was conducted with White Leghorn pullets from 8 to 21 weeks of age. The effect of these treatments on ability of the pullets to enter production was determined by feeding all birds the same laying mash containing 15.3 percent protein and approximately 1,260 Calories per pound from 21 to 29 weeks of age. The results of the study show t h a t energy level of the developing rations had no effect on body weight gains, rate of peak production or size of eggs produced. With protein levels of 12.7 percent or
165
less, the high energy diet increased days to 50 percent lay. Energy content of the diet had no effect on age at 50 percent lay with protein levels of 13.7 percent or higher. Giving the pullets free access to whole milo with mash caused an increase in days to 50 percent lay, increased body weight at 21 weeks of age but had no effect on peak rate of lay. With the low energy mashes, feeding whole milo resulted in a decrease in total feed consumed, whereas with the high energy mashes it caused an increase in the amount of feed eaten. With pullets fed all-mash rations, 13.0 percent protein in the developing diet resulted in body weights and egg size equal to t h a t obtained with higher protein levels. This low protein level permitted the attainment of a peak production rate of 88 percent. With the mash and milo system of feeding, increasing protein level resulted in increased body weight. With this system of feeding, consumption of rations with 12 percent protein resulted in a peak production of 87 percent. REFERENCES Berg, L. R., G. E. Bearse, R. S. Hansen, L. S. Jensen and J. McGinnis, 1956. Energy level of the diet for laying hens in Western Washington. Washington Agri. Exp. Sta. Tech. Bull. 22, pp. 1-25. Berg, L. R., and G. E. Bearse, 1958. Protein and energy studies with developing White Leghorn pullets. Poultry Sci. 37: 1340-1346. Blaylock, L. G., 1956. The protein requirement of growing birds. Poultry Sci. 35: 1133. Combs, G. F., 1955. Energy-protein ratio approach for poultry feed formulation. Flour and Feed. Aug. 1955, p. 4-5. Titus, H. W., 1957. Energy values of feedstuffs for poultry. Unpublished mimeographed material, 14 pp. Vondell, R. M., and R. C. Ringrose, 1958. The effect of protein and fat levels and calorie to protein ratio upon performance of broilers. Poultry Sci. 37: 147-151.