The relationship between semen quality and mineral
composition of semen in various ram breeds
H.A. Abdel-Rahman, M.S. El-Belely
*, A.A. Al-Qarawi, S.A. El-Mougy
Department of Veterinary Medicine, Faculty of Agriculture and Veterinary Medicine, King Saud University, P. O. Box 1284, Bureidah, Al-Qassim, Saudi Arabia
Received 18 October 1999; accepted 18 February 2000
Abstract
Semen was collected during the breeding season from rams by electroejaculation from two native (13 Najdi and 8 Naemi) and three imported (6 Merino, 7 Somalian and 9 Sudanese) sheep breeds. There was a marked reduction in sperm concentration and the percentage live spermatozoa (p<0.01) produced by the Somalian (Barbari) and Sudanese (Sawakni) breeds. On the other hand, these two breeds showed the highest percentage of spermatozoal individual motility (p<0.05) and the highest concentrations of sodium (Na) chloride (Cl) and inorganic phosphorus (P) in the whole semen, seminal plasma and spermatozoa. Superior sperm density, percentage live spermatozoa and seminal concentrations of potassium (K) and calcium (Ca) were evidenced in the Najdi, Naemi and to a lesser extent, in the Merino rams. The biological effects of these inorganic constituents, together with magnesium (Mg), in the semen on semen quality should be considered in the interpretation of the results obtained in the fertility evaluation of the various ram breeds.#2000 Published by Elsevier Science B.V.
Keywords:Minerals; Spermatozoa; Breeds; Ram
1. Introduction
Genetic improvements of farm animals rely on the intensive use of a few superior males either for natural mating, or in arti®cial insemination programs. The production of meat and milk may be increased through selective breeding of ewes with rams exhibiting desir-able genetic combinations. However, sperm density, viability and activity as well as other sexual charac-teristics of the different breeds may limit the extent to which rams can be used for breeding. The in¯uence of the major biologically active inorganic components on these sperm parameters has been extensively studied in various breeds of rams (Scott et al., 1963; Dott and White, 1964; Wallace and Wales, 1964; Quinn et al.,
1965;Quinnand White,1966;Stechell, 1974;Hamamah and Gatti, 1998). However, these investigations were con®ned to one speci®c breed and came to no conclusion regarding the effect of breed on the interaction between the chemical composition of semen and semen quality. The present attempt was, therefore, conducted to identify the breed-related variations in inorganic ele-ments including Na, Cl, K, Ca, P and Mg of the dif-ferent seminal fractions and their concentration effects on semen quality of native and imported sheep breeds.
2. Materials and methods
Twenty one native (13 Najdi and 8 Naemi), 6 Australian (Merino), 7 Somalian (Barbari) and 9 Sudanese (Sawakni) rams were selected at the *Corresponding author.
expected time of greatest output of spermatozoa (October to February 1998) from the farm of the Faculty of Agriculture and Veterinary Medicine, King Saud University, together with a private farm nearby to Bureidah. Animals were clinically healthy and ran-ging in age from 2 to 5 years. When the ®ve breeds are combined, they produce an age pro®le (2.90.3 years) typical of a single breed.
Semen collection by electroejaculation from the 43 rams was undertaken using a bipolar electrode with a 4-s stimulation period and an 8-s rest period. Imme-diately after collection, each sample was placed into a portable, temperature controlled waterbath (378C) to prevent cold shock and only samples of good initial motility (not <70%) were evaluated. Each ejaculate was evaluated for the following criteria:
1. Individual spermatozoa motility percent, semen was diluted with 2.9% sodium citrate dihydrate solution was recorded on a subjective scale of (0±100%) to the nearest 5% after viewing several microscopic ®elds.
2. Sperm cell concentration was quanti®ed by direct cell count using the improved Neubauer haemo-cytometer (Sorenson, 1979).
3. Percentage live sperm was recorded as described by Campbell et al. (1956). Duplicate smears from each freshly collected ejaculate were stained with eosin-nigrosin stain. A total of 200 spermatozoa were examined randomly (100 in each of the two smears).
Following evaluation, approximately two-thirds of the collected sample was processed as follows:
1. Semen was drawn off into a capillary blood tube and centrifuged at 4000gfor 5 min to obtain the packed sperm volume (PSV) according to the equation:
PSV % Length of packed sperm column mm
Length of total semen column mm 100
2. 50ml of semen was drawn into a tube containing 1 ml deionized water (dilution rate1:21) to provide a lysed sperm sample (LSS)
3. The remaining semen sample was centrifuged as previously mentioned for harvesting of the seminal plasma sample (SPS).
Concentrations of the electrolyte in spermatozoa were determined according to the formula reported by Mulei and Daniel (1988) with certain modi®cations:
Inter-spermatic mineral content
10021Aÿ 100ÿPSV B PSV
whereAandBare concentrations (mg/100 ml) of the mineral in LSS and SPS, respectively.
Na and K were determined in the whole semen, seminal plasma and spermatozoa by emission ¯ame photometry, Ca by atomic absorption spectrophoto-metry, whereas Cl, P and Mg were assessed using commercial diagnostic kits (bio-Merieux, France).
The statistical signi®cance of the results was eval-uated by the least-squares analysis of variance using the general linear models (GLM) procedures of the Statistical Analysis System (SAS, 1996).
3. Results
As shown in Table 1, the overall mean values (SE) of sperm count (1943.4132.3106
/ml), percentage of motile spermatozoa (80.56.4%) and percentage of live spermatozoa (75.25.8%) were signi®cantly affected by breed. Spermatozoa of the native (p<0.01) and Merino (p<0.05) rams were higher in concentrations and percentage live than Barbari and Sawakni rams (Table 1) displaying the highest (p<0.01) percentage of motile spermatozoa than the former breeds.
In all of the breeds studied, concentrations of Na, Cl and P in the seminal plasma always exceeded those in the spermatozoa, while concentrations of K, Ca and Mg was greater in the spermatozoa. Despite this general agreement between breeds, the Barbari and Sawakni rams showed the highest (p<0.01) concentrations of Na, Cl, and P whereas the other breeds displayed the highest (p<0.05) concentrations of K and Ca in the whole semen, seminal plasma and spermatozoa. There was no de®nite trend in the distribution of Mg in the different semen fractions amongst breeds.
the Na, Cl and P concentrations of the whole semen decreases and the K, Ca and Mg increases as the ejaculate becomes more dense. The percentage of motile spermatozoa decreases as the K and Ca levels
increase and the Na, Cl, P and Mg decrease. The percentage live (unstained) spermatozoa were corre-lated positively with K and Ca and negatively with P in the different semen fractions (Table 2).
Table 1
Semen quality and concentrations of the major inorganic components in the semen of various ram breedsa
Breed Semen quality Material Na (mg/100 ml)
Cl (mg/100 ml)
K
(mg/100 ml) Ca (mg/100 ml)
P
(mg/100 ml) Mg (mg/100 ml) Najdi (n13) S.C.b2251.6227.4** Semen 192.318.1 183.518.6 87.58.8* 20.92.8 10.61.8 9.30.8
%Mc74.87.5 Plasma 194.619.2 236.424.1 31.43.2* 16.82.0 13.21.4 8.00.7 %Ld76.46.9* Sperm 86.69.3 130.213.3 145.614.9* 25.63.3* 8.01.0 9.91.1 Naemi (n8) %S.C. 2468.4239.6** Semen 129.213.1 141914.4 118.312.1** 26.92.8* 8.91.4 9.71.0 %M 77.26.8 Plasma 158.116.3 163.417.2 75.27.8** 20.22.4 10.31.8 8.40.8 %L 79.98.1** Sperm 91.910.4 118.811.1 161.616.4** 32.43.5** 5.81.1 10.31.2 Merino (n6) %S.C. 2036.5201.3* Semen 156.315.9 174.217.6 109.111.2** 24.32.9* 9.21.3 11.61.3 %M 81.38.5* Plasma 202.621.4 216.322.8 66.36.8** 19.12.0 11.71.5 9.80.9 %L 74.17.6* Sperm 114.311.5 133.714.0 153.715.2** 28.82.8* 6.61.0 13.41.5 Barbari (n7) %S.C. 1644.8206.2 Semen 231.623.4** 250.124.9** 78.38.1 22.22.3 11.11.2 10.81.2 %M 84.28.2** Plasma 244.225.1** 276.328.1** 34.43.5 21.62.5 13.41.3 9.11.0 %L 70.97.3 Sperm 217.719.8** 223.921.7** 122.212.3 22.32.2 7.90.8 12.31.3 Sawakni (n9) %S.C. 1318.2115.6 Semen 263.226.0** 279.628.6** 66.46.8 19.62.0 12.41.2* 11.11.2 %M 86.68.5 Plasma 308.131.9** 300.329.9** 28.53.1 18.21.9 16.51.2* 7.90.6 %L 68.26.9 Sperm 219.822.5** 257.825.2** 104.310.5 20.72.1 8.40.6 14.21.4* Overall (n43) %S.C. 1943.4132.2 Semen 194.214.3 205.417.1 51.44.6 22.81.6 10.41.3 10.51.2
%M 80.56.4 Plasma 221.418.8 238.221.4 47.23.7 19.21.3 13.41.8 8.60.6 %L 75.25.8 Sperm 145.511.4 172.615.3 137.011.5 26.32.3 7.30.6 12.10.9
aAll values are MeanSE.
bRepresents spermatozoal count106/ml. cPercentage of motile spermatozoa. dPercentage of live spermatozoa.
*p<0.05; **p<0.01.
Table 2
Correlation between major inorganic constituents of ram semen and semen quality
Na Cl K Ca P Mg
S.C.a: semen constituent ÿ0.581** ÿ0.611** 0.736** 0.290* ÿ0.301* 0.292* S.C.: plasma constituent ÿ0.663** ÿ0.725** 0.169 0.283* ÿ0.425** 0.336* S.C.: sperm constituent ÿ0.355* ÿ0.299* 0.386** 0.316* ÿ0.511** 0.343* %Mb: semen constituent 0.215 0.191 ÿ0.224 ÿ0.096 0.242 0.188
%M: plasma constituent 0.421** 0.285* ÿ0.236 ÿ0.133 0.327* 0.213 %M: sperm constituent 0.379** 0.314* ÿ0.574** ÿ0.306* 0.284 * 0.468** %Lc: semen constituent ÿ0.268 ÿ0.139 0.363* 0.294* ÿ0.292* ÿ0.081
%L: plasma constituent ÿ0.236 ÿ0.088 0.446** 0.325* ÿ0.308* 0.194 %L: sperm constituent ÿ0.270 ÿ0.104 0.618** 0.303* ÿ0.276* ÿ0.076
aRepresents spermatozoal count106/ml. bPercentage of motile spermatozoa. cPercentage of live spermatozoa.
4. Discussion
Extensive studies on evaluating semen parameters were conducted in rams of different breeds. The higher sperm density and percentage live sperm shown by the native breeds (Najdi and Naemi) agreed with those reported for the British (Suffolk) rams (Jennings, 1976; Jennings and McWeeney, 1976) and the Egyp-tian (Awassi and Ossimi) rams (Amir, 1966; Abdel-Hakeam et al., 1978; Abou-Ahmed et al., 1986; Seida et al., 1986). While no data are available in the literature concerning results of semen characteristics in the Barbari and Sawakni rams, results of sperm density and viability estimates reported by Salamon (1964), Dott and Foster (1972) and Lino and Braden (1972) in Merino rams at Australia so far exceeded our results. The discrepancy might be related, in part, to environmental factors such as high ambient tempera-ture and low humidity in the relevancy current study, which has been shown to affect semen characteristics in the ram (El-Wishy et al., 1976; Loubser and Van Niekerk, 1983; Abou-Ahmed et al., 1986).
In this study, the overall mean (Table 1) of ion concentrations found in the whole semen is in agree-ment with that recorded in the ram by Scott et al. (1963), Wallace and Wales (1964) and Stechell (1974), but Na, Cl and K values were about twice the level reported by Quinn et al. (1965) and Quinn and White (1966).
The correlations set out in Table 2 might explain the encountered variations in semen quality of the various ram breeds studied. As might be expected from the distribution of the ions between the sperm and plasma, higher concentrations of K, Ca and Mg in the whole semen of the native breeds may be due to the more dense ejaculates. The positive correlation (Table 2) between all, except K and Ca, ions in plasma and spermatozoa and the percentage motility could explain the higher motility evidenced by the Barbari and Sawakni spermatozoa. Moreover, the higher sper-matozoal K and Ca levels notably caused some reduc-tion in spermatozoal activity in the native and Merino breeds. These results support the reports of earlier work that K was detrimental to metabolism at high concentrations (Cragle and Salisbury, 1959) for bull spermatozoa and that Ca depressed the metabolism of bull and ram spermatozoa and exaggerated the detri-mental effects of K (Blackshaw, 1953). The data
suggest a reciprocal relationship between intracellular contents of K, Ca and P with respect to percentage live sperm (unstained); a high percentage of live cells being associated with high K and Ca and low P levels. These results were true for the native (Najdi and Naemi breed) and Merino spermatozoa and this meant that the K, Ca and P are concerned with the perme-ability of ram spermatozoa as reported by Mikulecky and Tobias (1964).
In conclusion, the distribution of major ions studied between sperm fraction and seminal plasma could provide the basis for variation of semen quality between ram breeds and should be considered in the interpretation of the results obtained in the evalua-tion of the fertility of rams.
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