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The Effect of Dietary Fat Level on the Rate of Mortality in Caged Layers*
The Effect of Dietary Fat Level on the Rate of Mortality in Caged Layers* B . E. M A R C H AND JACOB B I E L Y Department of Poultry Science, University of British Columbia, Vancouver, B. C, Canada (Received for publication December 14, 1960)
A
The present paper summarizes the d a t a on mortality obtained in an experiment in which birds were kept in cages and fed diets supplemented with different levels of fat from day-old to 3 years of age.
RESULTS AND DISCUSSION T h e d a t a on causes of mortality are summarized in Table 2. The mortality in each group during each year has been expressed as a percentage of the birds alive in the group a t the beginning of the given year. T h e total percent mortality from the various causes for the three years is given as the sum of the percent mortality in the individual years. The total percent mortality calculated in this way is higher than if the over-all mortality had been calculated from the number of day old chicks placed on experiment. T h e particular method of calculation used was adopted in order to minimize the effect of the decrease in population caused b y a number of factors other t h a n those of interest in the study.
EXPERIMENTAL Starting, growing and laying rations were formulated according to Table 1. The rations were calculated to contain 20, 16.5 and 15 percent protein respectively. Each type of ration was adjusted to contain 2.5, 7.5 and 12.5 percent of fat. The two higher levels of fat were attained b y the inclusion in the ration of 5 and 10 percent respectively of feed-grade animal fat. Since it was desired to study primarily the effect of feeding high levels of fat without providing energy levels t h a t would be excessively high, ground oat hulls were added in equal weight to the supplementary fat in diets supplemented with 5 and 10 percent fat. Protein level was kept constant in the rations of different fat content by increasing the levels
T h e causes of mortality were broken down into four groups. Mortality from leucosis and liver and kidney disorders is shown separately in the table. All other diagnoses of the causes of death of birds in the experiment have been grouped together since either they represent too
* Carried out with the assistance of a grant from the Canada National Research Council. 9
Downloaded from http://ps.oxfordjournals.org/ at New York University on June 19, 2015
of soybean oil meal a n d / o r fish meal and reducing the level of ground wheat. A total of 1,259 day-old White Leghorn pullet chicks was started on the experiment. The chicks were brooded and reared in batteries and then kept in community cages during the laying period. Record was kept of variations in body weights and of the incidence and causes of mortality. The experiment was terminated when the birds were 3 years old.
L T H O U G H the advantages of fat - supplementation of broiler rations have been amply demonstrated, the value of thus increasing the energy level of laying rations is questionable. I t has been reported b y Weiss and Fisher (1957) a n d Donaldson and Gordon (1960) t h a t rations containing high levels of fat fed to laying birds m a y result in obesity and fatty livers leading to a high rate of mortality.
10
B. E. MARCH AND J. BIELY TABLE 1.—Composition of diets, (lb./100 lb.) Starting diets
Metabolizable energyj Cal./lb.
Laying diets
7.5%
12.5%
2.5%
7.5%
12.5%
2.5%
7.5%
12.5%
44.25 15.0 10.0 17.0
42.25 15.0
29.8 15.0
52.30 15.0
39.85 15.0
38.0 15.0
— 20.0
— 12.0
— 13.0
50.0 15.0 15.0
52.0 15.0
— 19.0
54.30 15.0 10.0 10.0
— 10.0
— 14.0
0.05
0.05
0.05
1.75
1.75
1.75
1.75
4.0 2.5 0.5
4.0 2.5 0.5
4.0 2.5 0.5
0.0125
0.0125
0 0125
— — — — — 0.375 — —
— — — — — 0.375
— — — — — 0.375
5.0 2.5 2.5 0.1 1.0
5.0 2.5 2.5 0.1 1.0
6.5 2.5 2.5 0.1 1.0 1.7 0.5
2.0 2.5 2.5 1.0
2.0 2.5 2.5 1.0
3.5 2.5 2.5
0.5
0.5
0.5
0.5
1.0 1.7 0.5
0.01
0.01 0.1
0.1
0.01
0.01
0.01
0.01
0.25 0.05
0.25 0.05
0.25 0.05
0.25 0.05
0.25 0.05
0.25 0.05
0.1
0.022 0.022 200 mg. 200 mg.
— — — 1,250
0.022 200 mg.
0.1
0.1
0.1
0.022 0.022 0.022 200 mg. 200 mg. 200 mg.
5.0 5.0
—
— 10.0 10.0
— — —
1,330
1,390
1,280
5.0 5.0
—
— 10.0 10.0
1,360
1,390
7.0 2.0 2.0 2.0
—
1,240
2.0 2.0 2.0
—
2.0 2.0 2.0
—
5.0 5.0
10.0 10.0
1,340
1,390
* Trace mineral mix: 6.0% Mn, 0.12% I, 2.0% Fe, 0.2% Cu, 0.006% Zn. 0.02% Co, 27.0% Ca. t Ribo-4, by courtesy of Merck & Co. Ltd., Montreal, P.Q. t Calculated according to Titus (1955). TABLE 2.—Summary of causes of mortality in
hens fed diets of different fat content Fat level in diet
2.5%
7.5%
12.5%
1st year* Leucosis-complex Kidney disorder Liver disorder Other
5.1 0.7 0.9 12.8
4.9 0.9 1.4 14.3
3.7 1.7 1.0 18.1
19.5
21.5
24.5
4.5 3.8 2.9 16.0
4.5 3.5 9.1 17.5
6.4 1.1 6.7 13.8
27.2
34.6
28.0
3.6 2.0 1.5 15.3
1.8 3.6 1.8 10.1
2.6 3.3 2.6 17.9
22.4
17.3
26.4
13.2 6.5 5.3 44.1
11.2 8.0 12.3 41.9
12.7 6.1 10.3 49.8
69.1
73.4
78.9
Total Znd year* Leucosis-complex Kidney disorder Liver disorder Other Total 3rd year* Leucosis-complex Kidney disorder Liver disorder Other Total 0-3 years] Leucosis-complex Kidney disorder Liver disorder Other Total
* The percentages are based on population at beginning of this year. Mortality from accident or cannibalism has been excluded from the calculation. t Total of percentages given for the individual
years.
small a proportion of the total mortality or they were not regarded as being related to the dietary treatments imposed. The incidence of leucosis was similar in all three groups of birds regardless of the fat content of the diet. Similarly the number of birds in which mortality was attributable to some form of kidney dysfunction (e.g. nephritis, kidney haemorrhage, dropsy) did not appear to be related to the level of fat which was fed. Only the incidence of mortality involving liver disorders was affected by the fat content of the diet. Thus over the three years of experiment mortality from liver derangement was approximately doubled when either 5 or 10 percent of fat was added to the basal laying ration. Mortality from miscellaneous causes showed no consistent relation from year to year with the fat content of the diet. It is commonly believed that supplementation of laying rations with fat may result in undesirable gains in weight, particularly in birds kept in cages where activity is somewhat restricted. The average weights of the birds in the experiment at the end of the 1st, 2nd and 3rd years are
Downloaded from http://ps.oxfordjournals.org/ at New York University on June 19, 2015
Ground wheat Ground yellow corn Ground oats Soybean oil meal (44% protein) Fish meal (70-74% protein) Dehydrated cereal grass Distillers dried solubles DL-methionine Limestone Bone meal Iodized salt Manganese sulphate Trace mineral supplement* Vitamin suppiementf Vitamin A dry (10,0001.U. per gm.) Vitamin D3 dry (1,650 I.C.U. per gm.) Penicillin Feeding oil (2,250 A-300 D) Animal fat Ground oat hulls
Growing diets
2.5%
T H E EFFECT OF DIETARY FAT
TABLE 3.—Changes in body weight of hens fed diets of different fat content
Fat level in diet At 1 year old At 2 years old At 3 years old
2.5%
7.5% 12.5%
Average weight (lbs.) 4.9 5.0 5.0 4.9 5.2 4.8 5.4 5.9 5.3
Increment in weight, 1 to 2 years, all birds +0.01 +0.13 -0.20 Increment in weight 1 to 2 years—birds dying in 3rd year +0.002 +0.07 -0.14
body weight during the second year gave no indication of the probability of mortality in the subsequent year. From the literature regarding the effects of feeding high levels of fat to laying birds it was expected that the feeding of as much as ten percent of supplementary animal fat would have resulted in a greater increase in the rate of mortality. Considering the relatively long duration of the present experiment, the effect of fat fed at a high level was not great. It should be pointed out, however, that the present experiment differs in one very important respect from most of the experiments that have been reported. In this test the birds were fed the respective levels of fat from the time they were hatched until they were three years old. Weiss and Fisher (1957) observed that when animal fat was fed to 14-month old hens there was a greater incidence of liver and kidney abnormalities than when fat was fed to 35-week old pullets. It would seem that in assessing the results obtained in any study of the effect of fat on livability consideration has to be given to the age at which supplementary fat is supplied in the diet and probably also to the previous dietary history of the animals. In the present experiment it is likely that the comparatively small effect of high fat diets on livability in birds over an extended period was due to the fact that the birds were accustomed to the levels of fat fed from the time they were hatched. If there is a metabolic adjustment to high levels of fat then the stress imposed on the metabolism of the birds by the high levels of fat may accordingly have been less than if supplementary fat had been suddenly introduced into the diets when the birds were mature. The fact that White Leghorns were used in the experiment may also have been a factor mediating against an appreciably greater level of mortality in the
Downloaded from http://ps.oxfordjournals.org/ at New York University on June 19, 2015
shown in Table 3. The birds on the control diet, without added fat, showed no change in weight during the 2nd year and gained approximately ten percent in the 3rd year. The birds fed the diet containing five percent added fat (7.5 percent total fat) gained during the 3 year period and were the heaviest of the three groups at the conclusion of the experiment. The birds on the diet containing ten percent fat (12.5 percent total fat) slightly declined in weight during the second year and then showed a gain in weight of about 10 percent similar to that in the control birds during the third year. Although the increased mortality in the birds fed 5 percent of supplementary fat might seem to be related to the greater gains in weights in this group compared with those of the birds on the unsupplemented rations this possibility is not confirmed by the data on the birds fed 10 percent of supplementary fat. The data on the body weights were therefore analyzed to ascertain if the average change in weight of birds during the second year afforded any indication of the probability of survival during the third year. Table 3 shows the average increments in body weight during the second year of birds dying during the subsequent year compared with the average increments in weights of all the birds during the second year. It will be seen that the change in
11
12
B. E. MARCH AND J. BIELY
The effect of the additional energy contributed to the rations by the supplementary fat ]has, by this means, been reduced in order that any effect due to the fat per se might be more readily apparent. It may accordingly be concluded that a high level of fat, when fed over a prolonged period from the time the chicks were hatched had very little harmful effect on the livability of the birds. It is significant that the increase in mortality from liver derangement was similar with both the 5 and 10 percent levels of supplementary fat and that there was only
a difference of 50 Cal./lb. in the calorie content of the rations so supplemented. SUMMARY
Mortality was studied in White Leghorn pullets subjected to three dietary regimens under which the birds received 2.5, 7.5 or 12.5 percent of fat from the time of hatching until they were 3 years old. Mortality from liver derangement was approximately doubled when either 7.5 or 12.5 percent of fat was fed but no other untoward effects on mortality rate were noted. The lack of general adverse effects from the addition of fat may be explained by the fact that the level of energy in the diet was not increased commensurate with the level of supplementary fat. It is concluded that fat per se, when fed continuously at levels up to 12.5 percent in a well-balanced ration not excessive in energy content, has no adverse metabolic effects. ACKNOWLEDGMENT
The authors are indebted to Gordon Young (B.C.) Ltd. for the animal fat used in the study. REFERENCES Donaldson, W. E., and C. D. Gordon, 1960. The effect of 3 % added animal fat on laying hen performance. Poultry Sci. 39: 582-587. Titus, H. W., 1955. Scientific Feeding of Chickens. Inter-State Publishers, Granville, Illinois, U.S.A. Weiss, H. S., and H. Fisher, 1957. Plasma lipid and organ changes associated with the feeding of animal fat to laying chickens. J. Nutrition, 61: 267280.
NEWS AND NOTES {Continued from page 8) to the late Tom Newman to commemorate his outstanding services to poultry husbandry and as one of the founders and the first Secretary of the Scientific Poultry Breeders' Association, the fore-runner of the Poultry Association. The Award, made each year, consists of a medal and £50 sterling, and is known as the Tom Newman Memorial International
Award for Poultry Husbandry Research. The Award is an international one, and is made to the hving author, either male or female, of the most important contribution in poultry husbandry research work, pubhshed the previous year, for the benefit of poultry husbandry. It is made each year by the Award Committee
{Continued on page 39)
Downloaded from http://ps.oxfordjournals.org/ at New York University on June 19, 2015
birds fed the high levels of fat. Donaldson and Gordon (1960) found that in heavy breeds three percent of added fat in the diet increased mortality with a considerable incidence of kidney or liver haemorrhages. In light breeds, on the other hand, the addition of fat to the laying ration did not affect mortality and the effect on weight gain was less. It should also be remarked that in the present experiment, although birds were fed 5 and 10 percent supplementary animal fat, the energy contents of the rations were not increased commensurately. By the addition of ground oat hulls to the diets supplemented with fat, the range in metabolizable energy between the control diet and the diet containing 10 percent of oat hulls was approximately 150 Cal./lb. and only 50 Cal./lb. between the rations containing 5 and 10 percent of added fat.
A
The present paper summarizes the d a t a on mortality obtained in an experiment in which birds were kept in cages and fed diets supplemented with different levels of fat from day-old to 3 years of age.
RESULTS AND DISCUSSION T h e d a t a on causes of mortality are summarized in Table 2. The mortality in each group during each year has been expressed as a percentage of the birds alive in the group a t the beginning of the given year. T h e total percent mortality from the various causes for the three years is given as the sum of the percent mortality in the individual years. The total percent mortality calculated in this way is higher than if the over-all mortality had been calculated from the number of day old chicks placed on experiment. T h e particular method of calculation used was adopted in order to minimize the effect of the decrease in population caused b y a number of factors other t h a n those of interest in the study.
EXPERIMENTAL Starting, growing and laying rations were formulated according to Table 1. The rations were calculated to contain 20, 16.5 and 15 percent protein respectively. Each type of ration was adjusted to contain 2.5, 7.5 and 12.5 percent of fat. The two higher levels of fat were attained b y the inclusion in the ration of 5 and 10 percent respectively of feed-grade animal fat. Since it was desired to study primarily the effect of feeding high levels of fat without providing energy levels t h a t would be excessively high, ground oat hulls were added in equal weight to the supplementary fat in diets supplemented with 5 and 10 percent fat. Protein level was kept constant in the rations of different fat content by increasing the levels
T h e causes of mortality were broken down into four groups. Mortality from leucosis and liver and kidney disorders is shown separately in the table. All other diagnoses of the causes of death of birds in the experiment have been grouped together since either they represent too
* Carried out with the assistance of a grant from the Canada National Research Council. 9
Downloaded from http://ps.oxfordjournals.org/ at New York University on June 19, 2015
of soybean oil meal a n d / o r fish meal and reducing the level of ground wheat. A total of 1,259 day-old White Leghorn pullet chicks was started on the experiment. The chicks were brooded and reared in batteries and then kept in community cages during the laying period. Record was kept of variations in body weights and of the incidence and causes of mortality. The experiment was terminated when the birds were 3 years old.
L T H O U G H the advantages of fat - supplementation of broiler rations have been amply demonstrated, the value of thus increasing the energy level of laying rations is questionable. I t has been reported b y Weiss and Fisher (1957) a n d Donaldson and Gordon (1960) t h a t rations containing high levels of fat fed to laying birds m a y result in obesity and fatty livers leading to a high rate of mortality.
10
B. E. MARCH AND J. BIELY TABLE 1.—Composition of diets, (lb./100 lb.) Starting diets
Metabolizable energyj Cal./lb.
Laying diets
7.5%
12.5%
2.5%
7.5%
12.5%
2.5%
7.5%
12.5%
44.25 15.0 10.0 17.0
42.25 15.0
29.8 15.0
52.30 15.0
39.85 15.0
38.0 15.0
— 20.0
— 12.0
— 13.0
50.0 15.0 15.0
52.0 15.0
— 19.0
54.30 15.0 10.0 10.0
— 10.0
— 14.0
0.05
0.05
0.05
1.75
1.75
1.75
1.75
4.0 2.5 0.5
4.0 2.5 0.5
4.0 2.5 0.5
0.0125
0.0125
0 0125
— — — — — 0.375 — —
— — — — — 0.375
— — — — — 0.375
5.0 2.5 2.5 0.1 1.0
5.0 2.5 2.5 0.1 1.0
6.5 2.5 2.5 0.1 1.0 1.7 0.5
2.0 2.5 2.5 1.0
2.0 2.5 2.5 1.0
3.5 2.5 2.5
0.5
0.5
0.5
0.5
1.0 1.7 0.5
0.01
0.01 0.1
0.1
0.01
0.01
0.01
0.01
0.25 0.05
0.25 0.05
0.25 0.05
0.25 0.05
0.25 0.05
0.25 0.05
0.1
0.022 0.022 200 mg. 200 mg.
— — — 1,250
0.022 200 mg.
0.1
0.1
0.1
0.022 0.022 0.022 200 mg. 200 mg. 200 mg.
5.0 5.0
—
— 10.0 10.0
— — —
1,330
1,390
1,280
5.0 5.0
—
— 10.0 10.0
1,360
1,390
7.0 2.0 2.0 2.0
—
1,240
2.0 2.0 2.0
—
2.0 2.0 2.0
—
5.0 5.0
10.0 10.0
1,340
1,390
* Trace mineral mix: 6.0% Mn, 0.12% I, 2.0% Fe, 0.2% Cu, 0.006% Zn. 0.02% Co, 27.0% Ca. t Ribo-4, by courtesy of Merck & Co. Ltd., Montreal, P.Q. t Calculated according to Titus (1955). TABLE 2.—Summary of causes of mortality in
hens fed diets of different fat content Fat level in diet
2.5%
7.5%
12.5%
1st year* Leucosis-complex Kidney disorder Liver disorder Other
5.1 0.7 0.9 12.8
4.9 0.9 1.4 14.3
3.7 1.7 1.0 18.1
19.5
21.5
24.5
4.5 3.8 2.9 16.0
4.5 3.5 9.1 17.5
6.4 1.1 6.7 13.8
27.2
34.6
28.0
3.6 2.0 1.5 15.3
1.8 3.6 1.8 10.1
2.6 3.3 2.6 17.9
22.4
17.3
26.4
13.2 6.5 5.3 44.1
11.2 8.0 12.3 41.9
12.7 6.1 10.3 49.8
69.1
73.4
78.9
Total Znd year* Leucosis-complex Kidney disorder Liver disorder Other Total 3rd year* Leucosis-complex Kidney disorder Liver disorder Other Total 0-3 years] Leucosis-complex Kidney disorder Liver disorder Other Total
* The percentages are based on population at beginning of this year. Mortality from accident or cannibalism has been excluded from the calculation. t Total of percentages given for the individual
years.
small a proportion of the total mortality or they were not regarded as being related to the dietary treatments imposed. The incidence of leucosis was similar in all three groups of birds regardless of the fat content of the diet. Similarly the number of birds in which mortality was attributable to some form of kidney dysfunction (e.g. nephritis, kidney haemorrhage, dropsy) did not appear to be related to the level of fat which was fed. Only the incidence of mortality involving liver disorders was affected by the fat content of the diet. Thus over the three years of experiment mortality from liver derangement was approximately doubled when either 5 or 10 percent of fat was added to the basal laying ration. Mortality from miscellaneous causes showed no consistent relation from year to year with the fat content of the diet. It is commonly believed that supplementation of laying rations with fat may result in undesirable gains in weight, particularly in birds kept in cages where activity is somewhat restricted. The average weights of the birds in the experiment at the end of the 1st, 2nd and 3rd years are
Downloaded from http://ps.oxfordjournals.org/ at New York University on June 19, 2015
Ground wheat Ground yellow corn Ground oats Soybean oil meal (44% protein) Fish meal (70-74% protein) Dehydrated cereal grass Distillers dried solubles DL-methionine Limestone Bone meal Iodized salt Manganese sulphate Trace mineral supplement* Vitamin suppiementf Vitamin A dry (10,0001.U. per gm.) Vitamin D3 dry (1,650 I.C.U. per gm.) Penicillin Feeding oil (2,250 A-300 D) Animal fat Ground oat hulls
Growing diets
2.5%
T H E EFFECT OF DIETARY FAT
TABLE 3.—Changes in body weight of hens fed diets of different fat content
Fat level in diet At 1 year old At 2 years old At 3 years old
2.5%
7.5% 12.5%
Average weight (lbs.) 4.9 5.0 5.0 4.9 5.2 4.8 5.4 5.9 5.3
Increment in weight, 1 to 2 years, all birds +0.01 +0.13 -0.20 Increment in weight 1 to 2 years—birds dying in 3rd year +0.002 +0.07 -0.14
body weight during the second year gave no indication of the probability of mortality in the subsequent year. From the literature regarding the effects of feeding high levels of fat to laying birds it was expected that the feeding of as much as ten percent of supplementary animal fat would have resulted in a greater increase in the rate of mortality. Considering the relatively long duration of the present experiment, the effect of fat fed at a high level was not great. It should be pointed out, however, that the present experiment differs in one very important respect from most of the experiments that have been reported. In this test the birds were fed the respective levels of fat from the time they were hatched until they were three years old. Weiss and Fisher (1957) observed that when animal fat was fed to 14-month old hens there was a greater incidence of liver and kidney abnormalities than when fat was fed to 35-week old pullets. It would seem that in assessing the results obtained in any study of the effect of fat on livability consideration has to be given to the age at which supplementary fat is supplied in the diet and probably also to the previous dietary history of the animals. In the present experiment it is likely that the comparatively small effect of high fat diets on livability in birds over an extended period was due to the fact that the birds were accustomed to the levels of fat fed from the time they were hatched. If there is a metabolic adjustment to high levels of fat then the stress imposed on the metabolism of the birds by the high levels of fat may accordingly have been less than if supplementary fat had been suddenly introduced into the diets when the birds were mature. The fact that White Leghorns were used in the experiment may also have been a factor mediating against an appreciably greater level of mortality in the
Downloaded from http://ps.oxfordjournals.org/ at New York University on June 19, 2015
shown in Table 3. The birds on the control diet, without added fat, showed no change in weight during the 2nd year and gained approximately ten percent in the 3rd year. The birds fed the diet containing five percent added fat (7.5 percent total fat) gained during the 3 year period and were the heaviest of the three groups at the conclusion of the experiment. The birds on the diet containing ten percent fat (12.5 percent total fat) slightly declined in weight during the second year and then showed a gain in weight of about 10 percent similar to that in the control birds during the third year. Although the increased mortality in the birds fed 5 percent of supplementary fat might seem to be related to the greater gains in weights in this group compared with those of the birds on the unsupplemented rations this possibility is not confirmed by the data on the birds fed 10 percent of supplementary fat. The data on the body weights were therefore analyzed to ascertain if the average change in weight of birds during the second year afforded any indication of the probability of survival during the third year. Table 3 shows the average increments in body weight during the second year of birds dying during the subsequent year compared with the average increments in weights of all the birds during the second year. It will be seen that the change in
11
12
B. E. MARCH AND J. BIELY
The effect of the additional energy contributed to the rations by the supplementary fat ]has, by this means, been reduced in order that any effect due to the fat per se might be more readily apparent. It may accordingly be concluded that a high level of fat, when fed over a prolonged period from the time the chicks were hatched had very little harmful effect on the livability of the birds. It is significant that the increase in mortality from liver derangement was similar with both the 5 and 10 percent levels of supplementary fat and that there was only
a difference of 50 Cal./lb. in the calorie content of the rations so supplemented. SUMMARY
Mortality was studied in White Leghorn pullets subjected to three dietary regimens under which the birds received 2.5, 7.5 or 12.5 percent of fat from the time of hatching until they were 3 years old. Mortality from liver derangement was approximately doubled when either 7.5 or 12.5 percent of fat was fed but no other untoward effects on mortality rate were noted. The lack of general adverse effects from the addition of fat may be explained by the fact that the level of energy in the diet was not increased commensurate with the level of supplementary fat. It is concluded that fat per se, when fed continuously at levels up to 12.5 percent in a well-balanced ration not excessive in energy content, has no adverse metabolic effects. ACKNOWLEDGMENT
The authors are indebted to Gordon Young (B.C.) Ltd. for the animal fat used in the study. REFERENCES Donaldson, W. E., and C. D. Gordon, 1960. The effect of 3 % added animal fat on laying hen performance. Poultry Sci. 39: 582-587. Titus, H. W., 1955. Scientific Feeding of Chickens. Inter-State Publishers, Granville, Illinois, U.S.A. Weiss, H. S., and H. Fisher, 1957. Plasma lipid and organ changes associated with the feeding of animal fat to laying chickens. J. Nutrition, 61: 267280.
NEWS AND NOTES {Continued from page 8) to the late Tom Newman to commemorate his outstanding services to poultry husbandry and as one of the founders and the first Secretary of the Scientific Poultry Breeders' Association, the fore-runner of the Poultry Association. The Award, made each year, consists of a medal and £50 sterling, and is known as the Tom Newman Memorial International
Award for Poultry Husbandry Research. The Award is an international one, and is made to the hving author, either male or female, of the most important contribution in poultry husbandry research work, pubhshed the previous year, for the benefit of poultry husbandry. It is made each year by the Award Committee
{Continued on page 39)
Downloaded from http://ps.oxfordjournals.org/ at New York University on June 19, 2015
birds fed the high levels of fat. Donaldson and Gordon (1960) found that in heavy breeds three percent of added fat in the diet increased mortality with a considerable incidence of kidney or liver haemorrhages. In light breeds, on the other hand, the addition of fat to the laying ration did not affect mortality and the effect on weight gain was less. It should also be remarked that in the present experiment, although birds were fed 5 and 10 percent supplementary animal fat, the energy contents of the rations were not increased commensurately. By the addition of ground oat hulls to the diets supplemented with fat, the range in metabolizable energy between the control diet and the diet containing 10 percent of oat hulls was approximately 150 Cal./lb. and only 50 Cal./lb. between the rations containing 5 and 10 percent of added fat.