The Influence of Glycogen on the Tenderness of Broiler Meat

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W. A. MILLER AND R. W. MORRISON

other groups (0 to 3.47 percent) treated with a detergent alone. REFERENCES Cotterill, O. J., and P . Hartman, 1956. Effect of antibiotics on the incidence of spoilage of shell eggs. Poultry Sci. 35: 733-735. Lorenz, F. W., F. X. Ogasawara and P. B. Starr, 1952. Spoilage of washed eggs. 3. A survey of ranch practices and results. Poultry Sci. 31: 221-226. Miller, W. A., 1956. The effect of coating the shells of washed eggs, that formerly were dirty, with antibiotics, upon subsequent spoilage. Poultry Sci. 35:241-243. Miller, W. A., 1957. A comparison of various washwater additives in preventing microbial deterioration in washed eggs that formerly were dirty. Poultry Sci. 36: 579-584. Winter, A. R., 1955. Detergents and sanitizers satisfactory for cleaning eggs. Ohio Farm and Home Research, 40 Sept.Oct.: p. 75, 86, and 87. Winter, A. R. and P. Clements, Properly washed eggs keep well. Am. Egg Poultry Rev. Feb. 1956.

The Influence of Glycogen on the Tenderness of Broiler Meat D. B. MELLOR, 1 P. A. STRINGER AND G. J. MOUNTNEY Texas Agricultural Experiment Station, College Station, Texas (Received for publication February 7, 1958)

A

LL of the specific factors which influence the tenderness of chicken meat have not been determined and classified. Age is known to be one of these factors. Feeding practices and other environmental factors affecting the growing bird are also known to influence tenderness. However, great variations in tenderness exist among carcasses of animals of the same age and reared under the same conditions. The glycogen level of the tissues at the time of death may be one of the basic factors influencing tenderness. 1 Present address: I.I.A.A., Bio de Janeiro, Brazil.

Several workers have demonstrated a relationship between the carbohydrate reserves and the carcass quality of beef cattle and swine. Bate-Smith (1948) in a review of the work of Madsen (1943,1944) reported on the results of fasting, regular feeding and specialized feeding of various levels of sugar on the tenderness of meat from bacon type pigs. In comparing the fed and fasted animals, he found that the higher glycogen content of the muscles of the fed group resulted in a pH of 5.50 as contrasted with 5.87 for the fasted group. Gibbons and Rose (1950) studied the effects of feeding, fasting and fatigue on

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manner, were washed in a detergent and a detergent-sanitizer. Eight detergenttreated groups of eggs revealed 0 to 3.47 (average 1.95) percent found to contain spoilage bacteria, when plated over an 11month storage period at approximately 35°F., and a relative humidity of 65 to 80 percent. The percentage of eggs containing spoilage bacteria in 6 groups treated with a detergent-sanitizer varied from 0 to 4.17 and averaged 0.93 when stored and analyzed in a similar manner. Two groups of eggs (15 and 16) similar to other groups in experiment B, were treated with a detergent and rinsed in water, and then immersed in iced water containing 20 p.p.m. of aureomycin. Surprisingly, the number of eggs containing Gram-negative spoilage bacteria (green Pseudomonas types) was much higher (7.7 and 11.1 percent) than in 8

GLYCOGEN AND M E A T TENDERNESS

crop and proventriculus of chicks fasted 24 to 30 hours. The glycogen level of the Pectoralis major was 915 mg. percent one hour after administration. This is an increase of 142 mg. percent above the fasted level reported in the previous paper (Golden and Long, 1942a). During the second hour and glycogen level increased to 1,150 mg. percent and to 1,344 at the end of the third hour. Silvette and Britton (1934) analyzed the breast and thigh muscles from 20 Brown Leghorn cockerels and pullets. They reported that the breast muscle contained three times as much glycogen as the thigh muscle. The averages of the glycogen values were 0.89 and 0.24 percent, respectively. The effect of fasting, cracked yellow corn feeding and sugar feeding on the muscle glycogen level of six week old New Hampshire cockerels were studied by Murray and Rosenberg (1953). For six cockerels the average white muscle (composite of Pectoralis major and minor) glycogen concentration after a 16 hour fast was 0.05 percent. The 90 birds fed cracked corn for periods of one to ten hours after a 16 hour fast averaged 0.33 percent. The 90 birds fed low grade sugar (sucrose) under the same conditions averaged 0.32 percent. The pattern of glycogen storage during the one to ten hour feeding period was variable for both groups. The present study was undertaken to determine: (1) The effect of feeding sugar prior to slaughter on the glycogen level of the Pectoralis major muscle tissue of broilers and (2) The effect of muscle glycogen level on the pH and tenderness of broiler meat. PROCEDURE

Fifty White Rock broilers were weighed individually and assigned to five groups so that variation in weight and sexes within

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the quality of bacon from Wiltshire hogs. They were unable to obtain significant differences between treatments because of the large variations in glycogen levels. Clark (1952) investigated "dark cutting" in steers which had been fasted from one to seven days before slaughter. He reported no difference in the pH of the muscle tissue that could be attributed to differences in glycogen levels. Using starved and exercised laboratory rats, Rose and Peterson (1951) found that reserve carbohydrates in the muscle tissue were lowered by starvation and seriously depleted by exercise. Starvation combined with exercise increased the loss of carbohydrate reserves. When sugar was fed, the recovery of these reserves was completed in six hours. Twelve hours after the termination of the starvation and exercise period the muscle glycogen level of this group was higher than in the group that had been rested and fed. The effects of feeding an oat chop and sugar mixture to pigs for 4, 8 or 20 hours immediately prior to slaughtering were also studied by these workers. Their results suggested that an eight hour feeding period was optimum even though differences between the groups were not significant because of the small number of animals. The glycogen concentration of the Pectoralis major muscle of young chicks was determined by Golden and Long (1942a, b). They reported that the decrease in glycogen levels during a 24 hour fast was greater for liver tissue than for muscle tissue. The liver glycogen decreased from 2,784 to 364 mg. percent. During this same period the glycogen of the Pectoralis major muscles decreased from 1,093 to 773 mg. percent. To determine the absorption rate of dglucose, these workers (1942b) administered the sugar solution directly into the

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D. B. MELLOR, P. A. STRINGER AND G. J. MOUNTNEY

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the groups and total weight were approxi- birds were weighed individually and their mately equal. Each group was placed in weights arrayed. The birds were then one section of a growing battery and d- assigned to the treatments in such a way glucose (Cerelose 2,001 Brand of dextrose as to equalize the weights in each treatsugar) was fed according to the levels ment group. shown in Table 1. The remainder of the Each group of ten birds was placed in ration consisted of a standard broiler one section of an eight section growing mash. To determine the amount con- battery with free access to a standard sumed, feed was weighed at the begining broiler mash and water for a period of and end of the 48 hour feeding period. The about six hours prior to initiation of the birds were weighed individually at the end experiment. Replicated groups, distriof this period. The average amount of buted at random in the battery, then sugar consumed and the average weight received one of the following treatments: gain were calculated for each group. (1) fasted 16 hours with no water, (2) After the 48 hour feeding trial, four of fasted 16 hours with access to water, (3) the five groups were retained and fed a permitted full access to feed and water, standard broiler mash for five days. These and (4) permitted full access to water and four groups were then re-treated as a diet consisting of 55 parts sugar and 45 previously except that the concentration parts standard broiler mash. After 16 of sugar was different in the various hours, the birds were slaughtered and groups. After the second series of sugar samples of muscle tissue removed and feeding experiments all birds were dis- frozen. Glycogen and pH determinations carded. The concentration of d-glucose fed were made from these samples. This pH to each group in this second feeding trial is determination will be referred to as the initial determination throughout this shown in Trial 2 of Table 1. Glycogen determinations were made by paper. The remainder of the carcasses were the anthrone method of Peterson and chilled overnight, packed in plastic bags Rose (1951) except that the method was and frozen. modified for chicken muscle. To determine the influence of glycogen" To test the effect of freezing on the concentration on tenderness, the eighteen muscle prior to glycogen analysis, a com- birds of highest glycogen concentration parison was made between frozen and and the eighteen birds of lowest glycogen fresh tissue from the same muscle. For this concentration were thawed overnight in a experiment six White Leghorn cockerels refrigerator and then cooked in Westingwere slaughtered and two, four gram, house electric ovens at 375°F. for one and samples of the left Pedoralis major muscle a half hours. Prior to cooking, a two gram were immediately excised from each bird. sample was removed from the left PecOne sample from each of the birds was toralis major muscle for pH determinaused immediately for glycogen determina- tions. The other whole Pedoralis major tion. The other sample was placed in a muscle was cooked and shear values were freezing unit (5°F.) for three days and determined at three positions by a Warthen glycogen determination was made on ner-Bratzler Shear Press. the frozen sample. RESULTS AND DISCUSSION To determine the influence of feeding The average sugar consumption and sugar on the muscle glycogen level, eighty, nine week old, battery-reared, gain in weight for the groups fed levels of male, White Rock broilers were used. The sugar between 20 and 100 percent of the

1031

GLYCOGEN AND MEAT TENDERNESS TABLE 1.—The average sugar consumption and gain of broilers fed different levels of sugar for 48 hours Dietary sugar level

%

Average gain, gms.

Average sugar consumption, gms.

Trial l 1 20 40 60 80 100

34.5 38.0 -4.0 -45.0 -78.0

34.4 71.2 75.8 73.6 58.7

1 2 3 4 5 6

no

'

Fresh tissue glycogen1

Frozen tissue glycogen1

mcg./gm.

mcg./gm.

1,126.1 460.5 2,252.2 1,367.5 538.6 1,388.8

1,159.8 299.2 2,050.4 953.9 789.4 1,250.0

83.2 60.2 66.8 65.8

Seven week old White Rock broilers. Eight week old White Rock broilers.

diet are shown in Table 1. When groups were fed diets containing more than 60 percent sugar, the total sugar consumption did not increase but in some groups actually decreased. In fact, those birds on the 100 percent sugar diet consumed less sugar than those on the 40 percent diet. The loss in weight that occurred with all groups fed more than 40 percent sugar appeared to be caused by the decreased palatability of the ration. Birds fed a 40 percent sugar diet consumed an average of 71 grams of sugar and 107 grams of broiler mash, or a total of 178 grams per bird, during the 48 hour period. Those birds fed an 80 percent sugar diet consumed a total of 92 grams of feed and those fed a 100 percent sugar diet consumed 59 grams. The average gain and sugar consumption for the nine week old White Rock broilers fed levels of sugar between 55 and 75 percent are shown in Table 1, Trial 2. The group fed 55 percent sugar consumed the maximum amount of sugar (83 grams). Fifty-five percent sugar in the ration was the highest that could be fed without a loss in body weight. The effect of freezing muscle tissue on its glycogen content is shown in Table 2.

The glycogen values of tissue held frozen were slightly lower than those samples analyzed immediately but the order remained fairly constant. However, because of the time required to determine glycogen values, freezing the tissue samples permitted the use of a larger sample of birds than could have been handled if fresh tissue were used. The average glycogen values of the Pedoralis major muscle are shown in Table 3. The birds fasted 24 hours had the highest average glycogen content and the sugar fed group had the lowest. Differences among treatment means were significant at the five percent level. When these differences were tested by Tukey's "Q" test only, the difference between the two extreme groups (the complete fast group and the sugar fed group) was significant. The results reported in this study indicate that higher glycogen values are obtained for broilers when they are fasted. The averages of the group that had access to water (Group 2) and the group that had access to broiler mash and water (Group 3) were not significantly different from either the total fast or the sugar fed, Groups 1 and 4, respectively. However, the trend was from a high glycogen level when birds were fasted 16 hours to a low glycogen level when sugar was fed. Golden and Long (1942a,b) reported an

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1 2

10.9 -15.2 -29.4 -13.4

•a- J

1 Each value is the average of three determinations.

Trial 22 5 65 70 75

TABLE 2.—The effect of freezing on glycogen content

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D. B. MELLOE, P. A. STRINGER AND G. J. MOTJNTNEY TABLE 3.—The average glycogen concentration and initial pB of samples of the Pectoralis major muscle from broilers subjected to selected ante-mortem treatments Glycogen replicates

Group No.

1 2 3

2

mcg./gm.

mcg./gm.

No feed or water for 16 hours prior to 2,259.5 slaughter Access to water but no feed for 16 hours 2,447.3 prior to slaughter Access to water and broiler mash until time 1,858.5 of slaughter Access to water, 55 percent sugar and 45 per- 1,178.9 cent broiler mash until time of slaughter

increase in the glycogen content of the Pectoralis major muscle of chickens after an injection of d-glucose into the proventriculus, and a lowering when they were fasted for 24 hours. These results are not directly comparable with the present study because of age differences in the chickens used. Golden and Long (1942a, b) used four-week old chicks compared with nine-week old broilers used in this study. In a comparison of the muscle glycogen levels of fed and fasted New Hampshire cockerels, Murray and Rosenberg (1953) also reported higher glycogen levels in groups fed up to the time of slaughter. However, these workers found such great variability existed in their birds that they were able to report only the average muscle glycogen levels for each group. Previous reports of the effects of fasting before slaughter and its relation to muscle glycogen content with beef cattle and swine have been controversial. Clark (1952) reported a decrease in the muscle glycogen level of steers fasted for two days but found no further decrease during the remaining five days of the fasting period. According to his work, a fasting period of 16 hours would be expected to decrease rather than increase the muscle glycogen level. Howard and Lawrie (1956), on the other hand, have demon-

1

2

2,292.9

6.2

6.4

1,400.5

6.3

6.3

1,510.3

6.3

6.4

1,329.0

6.2

6.2

strated that glycogen reserves can be low in well-fed, rested animals and high in fasted animals or those that have taken compulsory exercise. They postulated that perhaps there are species differences and differences in the temperaments of individual animals which account for the variations in glycogen reserves. Perhaps some carbohydrate-sparing mechanism operates in muscles during periods of stress. The average initial pH values for the fresh samples of the Pectoralis major muscle tissues are given in Table 3. Although differences ranged from a pH of 6.2 to 6.4 none were significant at the five percent level. One would not expect differences because the time period between slaughter and the pH determination was too short for glycolysis to produce sufficient acid to significantly lower pH. To determine whether a relation existed between tenderness and glycogen content, the shear strength of the Pectoralis minor muscles of the 18 birds with highest glycogen content and the 18 with lowest were determined. In Table 4 is shown the relation between the glycogen content, pH value and shear value for the 36 carcasses. No significant difference was found between the pH values of the high and low glycogen groups.

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4

1

pH replicates

GLYCOGEN AND M E A T TENDERNESS TABLE 4.—The final pH of the Pectoralis major and shear values of whole Pectoralis minor muscle from 36 selected birds of high and low glycogen concentration High

Low

Glycogen

Final pH

Shear

1 2 3 4 5 6 7 8 9 10 11 12 13 14 IS 16 17 18

5,501 5,079 4,430 3,906 3,703 3.664 3,628 3,541 3,392 3,328 3,312 3,272 2,967 2,888 2,775 2,681 2,437 2,422

6.0 6.5 6.3 6.1 5.9 6.2 5.8 6.1 5.5 5.9 6.2 5.1 5.4 5.9 5.9 5.9 6.2 6.0

3.75 3.58 4.00 5.00 5.58 3.00 4.58 3.08 3.83 4.50 5.75 3.41 4.75 3.41 3.13 4.58 3.83 4.41

Average

3,495.8 5.9

4.12**

Final Glycogen1 pH

Shear

897 883 855 850 775 767 748 694 678 667 599 557 534 520 481 426 373 270

6.6 6.1 5.9 6.3 6.1 6.1 6.1 6.1 6.0 6.2 6.0 6.2 6.4 6.2 6.4 6.4 5.8 6.2

4.75 6.50 4.75 5.41 5.83 6.33 4.08 5.00 4.33 8.00 7.83 5.33 4.91 7.66 4.33 4.91 4.25 7.00

643.0

6.2

5.62**

1

Micrograms per gram of Pectoralis major muscle. ** Significant at the .01 probability level.

The average shear value of the high glycogen group was significantly less than that of the low glycogen group. Therefore, it is concluded that the difference in shear values obtained in the present experiment is an expression of a difference in tenderness between birds with high and low glycogen concentrations. SUMMARY A study was made to determine the influence of muscle glycogen concentration on tenderness of poultry. Eighty White Rock broilers were systematically assigned to four groups and either fasted, allowed access to water only, to broiler mash and water, or to a sugar-broiler mash mixture and water for a 16 hour period immediately prior to slaughter. The effects of these ante-mortem treatments on the birds, the glycogen concentration, pH and resultant tenderness of the meat were determined. Muscle glycogen was determined on a comparable sample of the Pectoralis major muscle excised from each bird. The fasted

group of broilers had a higher muscle glycogen level than did the group which had been fed the sugar-broiler mash mixture. The other two groups were intermediate in glycogen level and did not differ significantly from either the fasted birds or the sugar-fed birds. Muscle shear values obtained from the Pectoralis minor muscle of the 18 birds of highest glycogen concentrations were lower than the shear values of corresponding muscles from the birds of lowest glycogen concentrations. The pH of the muscle tissue decreased from an initial value of 6.4 to a final pH of 5.9 for the group of carcasses with highest glycogen concentration. However, the pH of the group of carcasses with the lowest glycogen level did not change. REFERENCES Bate-Smith, E. C , 1948. Physiology and chemistry of rigor mortis with special reference to the aging of beef. Advances Food Res. 1: 1-38. Clark, G. E., 19S2. A study of some of the factors relating to glycogen content and the resulting color of the lean tissue of beef. M. S. Thesis, A. and M. College of Texas. Gibbons, N. E., and D. Rose, 1950. Effect of antemortem treatment of pigs on the quality of wiltshire bacon. Can. J. Res., F, 28: 438^50. Golden, W. R. C , and C. N . H. Long, 1942a. The influence of certain hormones on the carbohydrate levels of the chick. Endocrinology, 30: 675-686. Golden, W. R. C , and C. N. H. Long, 1942b. Absorption and disposition of glucose in the chick. Amer. J. Physiol. 136: 244-249. Howard, A., and R. A. Lawrie, 1956. Studies on beef quality. Part 2, Food Investigation, Special Report 63, Her Majesty's Stationery Office, London 1-79. Koonz, C. H., M. I. Darrow and E. O. Essary, 1954. Factors influencing tenderness of principal muscles composing the poultry carcass. Food Tech. 8:97-100. Madsen, J., 1943, 1944. Investigations on the keeping quality of pork from animals which have been fed feed containing sugar. Nord. Jordbrugsforskning 1943, 5-6, 340 (Chem. Centr. 1944, I, 1939).

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Bird

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D. B. MELLOR, P. A. STRINGER AND G. J. MOTJNTNEY

Murray, H. C , and M. M. Rosenberg, 1953. Studies on blood sugar and glycogen levels in chickens. Poultry Sci. 32: 805-811. Peterson, R., and D. Rose, 1951. Estimation of glycogen by use of Anthrone. Can. J. Tech. 29: 317-321.

Rose, D., and R. Peterson, 1951. Depletion of carbohydrate reserves by starvation and exercise. Can. J. Tech. 29: 421-427. Silvette, H., and S. W. Britton, 1934. A chemical consideration of red and white muscle. Amer. J. Physiol. 109: 98.

G. R. J. LAW 3 AND I. L. KOSIN Department of Poultry Science, State College of Washington, Pullman (Received for publication February 8, 1958)

I

N RECENT years, several investigations have been directed at studying the relationship of ambient temperature and reproductive ability in turkeys. These studies, particularly those of Burrows and Kosin (1953), Mitchell and Kosin (1954), and Kosin et al. (1955) have included fertility and hatchability and, more recently, semen metabolism (Kosin, 1958) as criteria for determining the effects of environment on the reproductive performance. The present study was designed to study the reproductive ability of the domestic male turkey as revealed by differential counts of spermatozoa; testes weight; and pertinent histology of the testes, epididymides, vasa deferentia and thyroid glands. MATERIALS AND METHODS

Eighty 32-week-old Broad Breasted Bronze male turkeys hatched on April 23, 1

Scientific Paper No. 1680. Washington Agricultural Experiment Stations, Pullman, Project No. 803. 2 Supported, in part, by Federal Funds for Regional Research (W-7) under the Hatch Amended Act. 3 Present address: Department of Poultry Husbandry, University of California, Berkeley.

1952 were distributed at random equally into two environmental groups: outdoor group (an uncontrolled ambient temperature and partly controlled light), and indoor group (controlled ambient temperature and light). The males had been separated from the females since they were approximately ten weeks old. All birds were fed an all-inclusive turkey breeder ration with feed, water and grit available ad libitum. The outdoor environment consisted of two outdoor pens of equal dimensions providing about 750 square feet of space per pen. The only protection from weather was a shelter with open sides provided in each of these two pens. The intensity of centrally located lights in the pens was adjusted to five foot-candle power at about eighteen inches above the floor. The indoor environment consisted of two pens providing 200 square feet each and located in a well insulated, completely enclosed building. The temperature was maintained between 55° and 50°F. Artificial light of five foot-candle intensity was provided. The day length of each environment was adjusted to at least thirteen hours of light. When the sunrise-sunset period outdoors

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Seasonal Reproductive Ability of Male Domestic Turkeys as Observed under Two Ambient Temperatures 12