Protein Requirements of Growing Pullets*

PROTEIN REQUIREMENTS OF GROWING PULLETS* ROY E. ROBERTS Agricultural Experiment Station, Purdue University (Received for Publication 5-18-29) The amount of protein from certain sources and with certain basal rations ( \ 2 , 3 , *, 5 ) required to rear chicks during the first 10 to 12 weeks of the growing period has been definitely measured and rations have been formulated which supply an adequate amount of protein during this early period., So far as we know the optimum amount of protein for pullets for the period extending from 10 or 12 weeks of age to maturity has not been determined for any given protein supplement with any specific basal ration. Atwood6 has reported that a poorly-balanced ration, fed to chicks from one week of age to maturity, reduced the rate of growth, the mature weight of the females, and the number of eggs laid, and increased the age at which the first egg was laid, but had little, if any, effect upon the weight of eggs laid. This poorly-balanced ration contained much less protein than is ordinarily used in rations for starting chicks. No attempt was made to measure the effect of different levels of protein upon chicks which had been started on a satisfactory ration. In comparing slow-maturing and early-maturing pullets Kennard 7 found that the slow-maturing pullets were inferior in respect to egg production during the fall and winter months as well as for the entire year, and also in respect to body weight throughout the year. Jull 8 and Parkhurst 9 have reported that the earlier in life that pullets start to lay the greater is the total production for the first year, the lower is the mean egg weight, the lower is the mean body weight at the time laying commences, and the later in life that both maximum body weight and maximum egg weight are attained. Kempster 10 has shown that there is a significant correlation between the rate of sexual maturity and egg production for the first laying year, but has called attention to the fact that in comparing one flock with another, a flock which was allowed longer to mature suffered no handicap so far as future performance was concerned. Lippin* Published with the approval of the Director of the Agricultural Experiment Station, Purdue University. 19

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cott11 observed that the age at laying of the first egg was an important factor in the seasonal distribution of egg weights during the first laying year. These investigators compared earlymaturing and late-maturing pullets from the same flock. The birds had received the same ration so that the differences in time of maturity were due largely to genetic factors. It is a common practice (12, 13, 14) to reduce the percentage of protein in the ration after pullets are 10 to 12 weeks old. The amount of protein which is fed is determined by the experience and ideas of the feeder rather than by any standard based upon experimental evidence. Opinions differ as to how rapidly a pullet should be developed. Some people believe that rations which are too high in protein bring pullets into production before they attain their proper weight and that such pullets are not able to withstand the strain of heavy egg production as satisfactorily as are those which receive a ration carrying less protein and which are allowed a longer growing period, enabling them to attain a greater weight at maturity. TABLE I.

RATIONS FOR F I R S T T E N W E E K S

Ingredients Ground Yellow Corn __. W h e a t Bran W h e a t Middlings Meat Scraps Dried B u t t e r m i l k Salt (NaCl) Cod Liver Oil (Certified) Total

Animal Protein Supplements Meat Scraps and Meat Scraps Dried Buttermilk 51 50 15 15 15 15 15 12 4 1 1 3 3 100 100

It seemed desirable to determine the relative effects of variations in the levels of animal protein on the growth rate of pullets from 10 weeks of age to maturity, their weight at maturity, and their subsequent egg production, in order to have a definite feeding standard for this period. The data here presented were obtained in a preliminary trial in which rather wide variations in the levels of animal protein were used. While it had been planned to continue the experiment through the first lay-

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ing year, urisatisf actory housing conditions made the egg records of little value and they are not included in this report. r - •• •

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EXPERIMENTAL

Two groups of 200 S. C. WhiteLeghornday-old chicks each, were started two weeks apart. During the first. 10 weekOhe chicks were brooded on. indoor laboratory tables previously des.-: cribed.15 The cockerels in the first group were removed at the end of seven weeks and in the second group at the end of eignt weeks.... . -.'. ,..,., The animal protein supplement for 150 chicks in each group was supplied by a combination of meat scraps and dried butter^ milk, while for the other 50 chicks in each group it was supplied by meat scraps alone. The rations used during the first 10 weeks are indicated in Table I. TABLE I I .

R A T I O N S F E D F B O M 10 W E E K S TO MATURITY

Meat Scraps and Dried Buttermilk First 10 Weeks Lot 1 Lot 2 Lot 3 55.07 59.35 Ground Yellow Corn 50.8 15 15 Wheat Bran. 15.. 15 W h e a t Middlings 15 15 9.12 Meat Scraps 15.2 3.04 1.81 Steamed Bone Meal 3.61 1 1 Salt (Nacl) — J _.. 1 Cod Liver Oil (Certified). 3 3 3 100.0 Total 100.0 100.0 Feed

Meat Scraps First 10 Weeks Lot'4 50.8 15 . 15 15.2 1 3 100.0

Analyses: Meat Scraps —49.35% P r o t e i n ; 10.66% P . 0 3 Steamed Bone Meal — 35.88% P 2 0-

When the pullets in each group were 10 weeks old, those which had received the combination of meat scraps and dried buttermilk were divided, according to weight, into three equal lots, designated as Lots 1, 2, and 3, which with the pullets that had received meat scraps alone, designated as Lot 4, were transferred to separate pens in a permanent brooder house. The pullets from the second group of chicks started were placed in these pens two weeks later than those from the first group and at that time the size of the pens which had been 7' x 7' was increased to 7' x 14'.

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AVERAGE W E E K L Y W E I G H T S OF PULLETS T H A T LIVED THROUGH 23RD W E E K

Meat Scraps and Dried Buttermilk Meat Scraps First 10 Weeks First 10 Weeks Lot 4 Lotl Lot 2 Lot 3 7.5 7.5 4.5 1.5

Lot Percentage Meat Scrap Protein—10 to 23 weeks „ .„,_„,At Start XT _ , At 23 Weeks 10th 11th 12th 13th 14th 15th 16th 17th ISth 19th 20th 21st 22nd 23rd

Week Week Week Week Week Week Week Week Week Week Week Week Week Week

44 34

44 43

43 39

43 39

Gm. 580 608 687 764 850 898 985 1043 1113 1166 1217 1271 1313 1381

Gm. 574 590 663 735 802 881 964 1019 1067 1108 1144 1201 1237 1304

Gm. 580 579 629 684 746 789 848 896 946 991 1028 1077 1097 1159

Gm. 507 553 629 690 783 854 927 997 1050 1105 1141 1192 1225 1281

The pullets were confined to these pens until those in the first and second groups were 25 and 23 weeks old respectively. During this period they were weighed individually at the end of each week. The pullets in Lots 1, 2, and 3 received rations containing respectively 7.5, 4.5, and 1.5 per cent of meat scrap proTABLE IV.

DISTRIBUTION OF P U L L E T S ACCORDING TO W E I G H T AT

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W E E K S OF A G E

Lot Percentage of Meat Scrap Protein—10 to 23 weeks Grams 801- 900 901-1000 1001-1100 1101-1200 1201-1300 1301-1400 1401-1500 1501-1600 1601-1700 1701-1800

Meat Scraps and Dried Buttermilk Meat Scraps First 10 Weeks First 10 Weeks Lot 1 Lot 2 Lot 3 Lot 4 7.5 7.5 4.5 1.5

1 3 3 5 9 11 8 2 2

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tein. The pullets in Lot 4 received the same ration which they had received from the start and which contained 7.5 per cent of meat scrap protein. The phosphorus supplied by the meat scraps in the rations for Lots 2 and 3 was adjusted by the addition of steamed bone meal to equal that supplied by the meat scraps in the ration for Lot 1, which contained more bone on account of its higher meat scrap content. The rations for the different lots from 10 weeks to maturity are given in Table II. RESULTS

Lots 1, 2, and 3, which received 7.5, 4.5, and 1.5 per cent of meat serap protein from 10 weeks to maturity, will be referred to as the high, medium, and low protein groups respectively. Lot 4, which received 7.5 per cent of meat scrap protein from the start to maturity, will be designated as the constant protein group. Table I I I gives the average weekly weights from the 10th to the 23rd week for the pullets in each lot that lived through this period. In determining the average weekly weights, the combined weekly weights of the older pullets were added to the corresponding weights (taken two weeks later) of the younger pullets, and this total was divided by the number of birds. The number of pullets of each age in the different lots was so nearly the same that any possible differences which might result from a difference in age would not affect the average weight as determined. At 23 weeks of age the average weekly weights of the high, medium, low, and constant protein groups were 1381 ± 17.4, 1304 ± 17.1, 1159 ± 17.5, and 1281 ± 20.4 grams respectively. There was a difference of only 77 grams in the average weights of the pullets in the high and medium protein groups, in favor of the higher protein level, and this small difference is probably not significant. Although the difference of 100 grams (at 23 weeks) between the average weights of the pullets in the high and constant protein groups may be considered significant, it should be noted that the greatest difference which existed at any other period was 77 grams. Also, there were 10 birds in each of these groups in laying conditionat 23 weeks of age. The most marked difference was in the case of the pullets in the low protein group. Their average weight was significantly lower than that of any of the other three lots.

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' Table IV shows the distribution of the pullets according to weight at 23 weeks of age. The weight of the pullets in the high protein group ranged from 1100 to 1700 grams. The range in weights was greater for the medium and constant protein groups with a few birds weighing less than 1100 grams. The distribution in these two lots was quite similar which is in agreement with the average weights as given in Table III. The low protein group had more birds in the lower weight groups and with one exception the weights in this lot did not exceed 1400 grams. The high and medium protein groups had 44 pullets each at the start and the low and constant protein groups 43 pullets each. Of the 10 pullets which were lost in the high protein lot, nine were killed by a rodent when 13 and 15 weeks old. Only one pullet died in the medium protein lot while four died in each of the other two lots. The four pullets which died in the constant protein lot were the smaller birds in this group. DISCUSSION

The small difference between the average weights of the pullets in the high and- medium protein groups suggests that in many cases pullets are being fed more animal protein during the growing period than is necessary for satisfactory growth. If this is verified by additional trials, the use of less protein during the growing period will be justified since some economy will result. The slower growth of the pullets in the low protein group as compared to that of the pullets in the other groups indicates that 1.5 per cent of meat scrap protein is not sufficient for maximum growth from 10 to 23 weeks. The slight difference in weight, which existed between the pullets in the high and constant protein groups at 10 weeks of age, was maintained with some variation throughout the growing period, when both lots were receiving the same ration. While the significance of this difference may be questioned, there is the possibility that it may be advisable to give chicks a ration relatively high in protein during the first 10 to 12 week in order to give them a good start. There is a slight suggestion of more uniform growth in the pullets which received the ration carrying the largest amount of

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protein. If this tendency should prove to be consistent, it would, in all probability, justify the use of the extra amount of protein. With the exception of the pullets in the low protein group, it seems doubtful whether the differences in the average weights which existed in the different lots of pullets at 23 weeks of age would be apparent for any length of time after the birds were given the same laying ration. What relative effect the ration, which was used during the first 10 weeks of the growing period, would have if continued to maturity remains to be determined. According to present plans for the next experiment all chicks will receive the same ration during the first eight weeks. This ration will contain somewhat more animal protein than was used in the starting ration in the present experiment. From eight weeks to maturity one lot will be continued on the starting ration and the other three will receive 7.5, 4.5, and 2.5 per cent of meat scrap protein respectively. This will check the levels of 7.5 and 4.5 per cent meat scrap protein used in the present experiment; will give one lot which receives one per cent more animal protein than did the lowest in the present experiment; and will give one lot with a relatively high protein level from the start to maturity. Since the change from the starting to the growing rations will be made at eight rather than at ten weeks of age, any differences which may result from the different levels of protein should have more opportunity to become apparent. In the present experiment it was planned to keep a record of egg production but unsatisfactory housing conditions made the egg records of little value. I n the next experiment individual pullet weights, egg records, and egg weights will be kept during the first laying year. It should not be inferred that the relative results which were obtained when the different levels of protein were fed with our basal ration would be the same with other combinations of feeds, since it is possible that the quantity and quality of amino acids present in the basal ration would have some influence upon the quantity of protein concentrate needed. SUMMARY

1. The data presented indicate that with our ration the inclusion of 4.5 per cent of meat scrap protein may be satisfactory

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for growing pullets from 10 weeks of age to maturity. However, there is a suggestion that 7.5 per cent of meat scrap protein gives somewhat more uniform growth during this period. 2. I t seems that 1.5 per cent of meat scrap protein in our ration is not sufficient for maximum growth from 10 to 23 weeks. 3. There appears to be some advantage in feeding a ration relatively high in protein during the first 10 weeks in order to give the chicks a good start. 4. The effect of the different levels of protein upon the maximum weight attained by pullets and upon the number and weight of eggs laid remains to be determined. BIBLIOGEAPHY 1

CABBICK, C. W., HAUGE, S. M., AND PRANGE, R. W., POULTRY SCIENCE,

1927, VI, 162. 2 PRANGE, R. W., HAUGE, S. M., AND CARRICK, C. W., POULTRY SCIENCE,

1927, VI, 302. = PBANGE, R. W., CARKICK, C. W., AND HAUGE, S. M., POULTRY SCIENCE,

1928, VII, 95 « PRANGE, R. W., HAUGE, S. M., AND CARRICK, C. W., POULTRY SCIENCE,

1928, VII, 186. s PRANGE, R. W., CARRICK, C. W., AND HAUGE, S. M., POULTRY SCIENCE,

1928, VII, 233. «W. Va. Agr. E x p . Sta., Bui. No. 179, 1923. T Ohio Agr. E x p . Sta., Monthly Bui. Nos. 71-72, 1921, 163. S J U L L , M. A., POULTRY- SCIENCE, 1924, I I I , . 153. 9PARKHURST, R . T . , POULTRY SCIENCE, 1 9 2 6 , V , 1 2 1 .

10 Missouri Agr. E x p . Sta., Research Bui. No. 78, 1925. 11 LippiNCOTT, W. A., PARKER, S. L., AND SCHAUMBURG, L. M., POULTRY SCIENCE, 1925, IV, 127.

12 P u r d u e E x t . Bui. No. 137, 1927, 14. is Ohio A g r . E x p . Sta., B i m o n t h l y Bui. No. 118, 1926, 12. 1*111. Agr. E x p . S t a . Circular No. 329, 1928, 10. is CARRICK, C. W., POULTRY SCIENCE, 1925, V, 98.