The Effect of Myotonia on Muscle Mass in the Myotonic Goat

 

 

 

 

 

 

 

 

Sarah Winningham Dobbins

Department of Biology

Tennessee Technological University

Cookeville, Tennessee

38505-0001

Abstract

Myotonic goats possess a genetic mutation which inhibits muscle relaxation after muscle stimulation occurs. This characteristic leads to an overall increase in muscle contraction over the lifespan of the goat, which leads to increased muscle tone and therefore muscle mass.

 

Key Words: myotonic goat, fainting goat, myotonia, muscle mass

 

 

Introduction

Myotonic goats have a genetic mutation that causes a decrease in muscle chloride conductance (Beck, et al 1999). This creates a condition in which, once stimulated, a muscle is unable to relax in the normal amount of time (Tapscott, et al 2001). The effect of this inability to relax sometimes causes the goat to “faint,” hence the name “fainting goat” (Vite, et al 1999).

Lee explored the connection between anthropometric measures, such as skinfold measurement, and specific measures, such as bioelectrical impedence. He found that there is a direct correlation and that the precision of anthropometric measures is roughly equal to that of using the bioelectrical impedance (Lee, et al 2000).Through measurements of height, weight, length, circumference, and body fat, muscle mass was estimated according to the methods of Swantek and used to compare and contrast the myotonic and normal goats (Swantek, et al 1999).

As Ellis stated, a positive correlation can be found between the circumference of muscles in limbs and overall muscle mass. Likewise, a negative correlation can be found between body fat (measured with the skinfold calipers) and overall muscle mass (Ellis 2001).

The objective of this study is to find whether the genetic condition of myotonia increases muscle mass. The findings may have a direct impact on the use of myotonic goats as meat goats, and an indirect impact on the study of myotonia congenita in humans.

 I project that the myotonic goats will have increased muscle mass in comparison with the normal goats because of the increased overall stimulation.

 

Methods and Materials

Using a standard tape measure, measurements were taken from the hoof to the shoulder and the rump to the chest of each myotonic goat. The measurements were recorded in the data table.  The same measurements were then taken from the normal goats and recorded in the data table. The tape measure was also used to measure the circumference of legs, neck, and chest from each goat. Skinfold measurements were taken from all four limbs and torso using skinfold calipers. The goats were then weighed on a standard scale. All data was recorded as measured (Ellis 2001).

After acquiring all the necessary data, the numbers were analyzed to estimate muscle mass using a standard bar chart. The chart shows a clear representation of muscle mass as a function of circumference, size, and height to weight ratio, and allows comparison between normal and myotonic goats (Swantek, et al 1999).

 

 

Results

Figure 1.  a comparison of the weight of both types of goats.
 
           

Figure 2.  a comparison of anthropomorphic measurements in both types of goats
 

As seen in Figures 1 and 2, the myotonic goats had a greater overall circumference and weight and a lesser skinfold measurement. According to Ellis, the elevated limb and neck circumference in addition to the added weight and lower skinfold measurements has a direct correlation to elevated skeletal muscle mass (Ellis 2001). Therefore, the myotonic goats were found to, in fact, have a higher skeletal muscle mass than the normal goats.

 

 

Limb Front (cm)

Limb Rear (cm)

Neck (cm)

Length (cm)

Height (cm)

Weight (kg)

Skinfold (cm)

Avg. Normal Goat

 

13.93

17.45

37.19

64.23

45.90

128.8571

2.30

Avg. Myotonic Goat

 

15.06

19.67

41.00

61.32

63.50

146.7714

1.11

Table 1. A brief view of the average anthropomorphic values in both goats.   

 

Discussion

The FFM (Fat-Free Mass) of the myotonic goats, in general, was higher than that of the normal goats, even though most of the goats were of the same age. This finding is in agreement with the findings of Wildeus, who also purported that the genetic condition of myotonia in animals would in turn increase their skeletal muscle mass (Wildeus et al, 1998).

The data gathered was also consistent with the approaches of Lee and Ellis (2000, 2001). The use of anthropometric measures to gather data and estimate muscle mass was accurate and the results were consistent with their expectations. The genetic condition described by Beck (1996) is the main proponent responsible for this increase in fat free mass.

 

Conclusion

            Overall, the myotonic goats presented a greater muscle mass than the normal goats. These findings are consistent with the hypothesis and with the literature, and may have an impact on meat goat husbandry in the future.

Literature Cited

Beck, C.L.; Fahlke, C.; and George, A.L. Jr. 1996. Basis for decreased muscle chloride conductance in the myotonic goat.  Proc. Natl. Acad. Sci. USA  93(20):11248-52.

 

Ellis, Kenneth J. 2001. Selected Body Composition Methods can be used in Field Studies. J. Nutr. 131: 1589S-1595S

 

Lee, R.C.; Wang, X.; Heo, M.; Ross, R.; Janssen, I.; and Heymsfield, Steven B. 2000. Total-body skeletal muscle mass: Development and cross-validation of anthropometric prediction models. American Journal of Clinical Nutrition. 72(3): 796-803

 

Swantek, P.M.; Marchello, M.J.; Tilton, J.E.; and Crenshaw, J.D. 1999. Prediction of Fat-Free Mass of Pigs from 50 to 130 Kilograms Live Weight. J. Anim. Sci. 77:893-897.

 

Tapscott, Stephen J and Thornton, Charles A. 3 August 2001. Reconstructing Myotonic Dystrophy. Science. 293: 816-817

 

Vite, C.H.; Melniczek, J.; Patterson, D.; and Giger, U. 1999. Congenital Myotonic Myopathy in the Miniature Schnauzer: an Autosomal Recessive Trait. Journal of Heredity. 90(5): 578-580

 

Wildeus, S.; Fernandez, J.M. 1998. Persistence of lactation in three breeds of goats in a forage-based meat production system. American Society of Animal Science. 76:24.

 

Appendix I

Raw data

 

Limb Front (cm)

Limb Rear (cm)

Neck (cm)

Length (cm)

Height (cm)

Weight (kg)

Skinfold (cm)

Normal 1

13.97

17.78

36.83

63.50

49.53

132

2.50

Normal 2

13.21

16.51

35.56

63.50

45.72

123.2

2.30

Normal 3

16.00

19.81

38.10

67.31

48.26

136.4

2.00

Normal 4

11.43

13.46

37.34

62.23

44.45

121

2.40

Normal 5

13.21

17.78

36.07

63.50

45.72

116.6

2.20

Normal 6

15.24

18.29

39.62

66.04

41.91

147.4

2.20

Normal 7

14.48

18.54

36.83

63.50

45.72

125.4

2.50

Avg. Norm.

13.93

17.45

37.19

64.23

45.90

128.86

2.30

 

 

 

 

 

 

 

 

Myotonic 1

16.51

20.32

40.64

58.42

60.96

121

1.00

Myotonic 2

15.75

19.05

38.10

63.50

63.50

127.6

1.20

Myotonic 3

16.51

20.83

43.18

60.96

66.04

143

1.00

Myotonic 4

16.26

19.30

40.64

58.42

64.77

158.4

1.20

Myotonic 5

13.46

21.34

45.72

63.50

60.96

162.8

1.10

Myotonic 6

13.21

18.54

40.64

63.50

62.23

167.2

1.00

Myotonic 7

13.72

18.29

38.10

60.96

66.04

147.4

1.30

Avg. Myo.

15.06

19.67

41.00

61.32

63.50

146.77

1.11