Chemical and Physical Properties of Semen 49 



Respiration 



In the presence of oxygen, semen shows a considerable respiratory 

 activity which is correlated both with concentration and motility 

 of spermatozoa. It is usual to express sperm respiration in terms of 

 Z02, a coefficient introduced by Redenz (1933) to denote ^1. O2 taken 

 up by 10^ sperm cells during 1 hr. at 37°; Z02 values reported by 

 Lardy and Phillips (1943a) for bull, cock, rabbit and ram semen, are 

 21, 7, 11 and 22, respectively. The use of Z02 is more convenient 

 than Q02 since the latter involves centrifugation of semen and 

 washing of sperm with an unphysiological fluid such as distilled 

 water; the average Q02 of ram sperm based on the dry weight of 

 washed sperm is about 8. Further references to the subject of sperm 

 respiration measurements, classified according to species are listed 

 in Table 9. 



Chang and Walton (1940) found a close relationship between 

 motility and respiratory activity in ram sperm. Walton (1938) sug- 

 gested measurements of oxygen uptake in bull semen as a supporting 

 method for the assessment of semen quality. Walton and Edwards 

 (1938) compared the breeding records of thirteen bulls, taking as a 

 measure of their fertility the number of matings required to produce 

 pregnancy in cows; when they analysed ten different samples of 

 semen from each of these bulls, they found that there is a close cor- 

 relation between the respiratory activity of semen and fertility 

 assessed on the natural service records. But Ghosh, Casida and 

 Lardy (1949), and Bishop et at., (1954) failed to establish a corre- 

 lation between the respiratory activity of bull semen and fertility, 

 as assessed on the basis of artificial insemination records. 



Further study will probably clear up these uncertainties but in 

 general, when we consider the significance of sperm respiration 

 measurements, there are certain points which must be taken into 

 account. Unlike fructolysis, the respiratory activity of semen is not 

 entirely exogenous since it involves, in addition to the oxidative 

 removal of products of fructolysis (chiefly lactic acid), the endo- 

 genous respiration, i.e. oxidation of some intracellular reserve 

 material, most probably a lipid. Moreover, it is possible to create, 

 experimentally at any rate, conditions under which sperm respira- 

 tion can be dissociated from motility. For example, in the presence 



