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G. IGBOELI and A. M. RAKHA

Summary.

Whole semen, seminal plasma and the pre-ejaculate fraction collected from ten Angoni bulls four times a week for 6 weeks were analysed for sodium (Na+) and potassium (K+) concentrations using a flame photometer and for calcium (Ca++) and magnesium (Mg++) using an atomic absorption spectrophotometer.

Na+ concentrations (mg/100 ml) in whole semen, seminal plasma and the pre-ejaculate fraction were 320±9·9, 347±8·4 and 335±47·1, respectively. Corresponding values for K+ were 69·4±3·1, 71·4±4·5 and 152±37·8; for Ca++ were 34·0±1·4, 35·3±1·1 and 4·1±1·4 and for Mg++ were 8·8±0·06, 8·3±0·3 and 5·7±1·7.

These concentrations were compared to the cation composition in blood. Correlation coefficients were calculated.

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G. IGBOELI and A. M. RAKHA

The relationship between testis size, sperm reserves, ejaculate volume and sperm concentration are well established, (Ortavant, 1956; Almquist, Amann & O'Dell, 1958; Hale & Almquist, 1960; Hahn, Foote & Seidel, 1969). In a another report, Igboeli & Rakha (1971) showed that the ejaculate volume and the number of spermatozoa per ejaculate of mature Angoni bulls (Central African Zebu) are less than those values reported for breeds from more temperate areas. No previous reports appear to be available on the testis size, and gonadal and extra-gonadal sperm reserves of indigenous Central African bulls.

Thirty, sexually mature, indigenous breeding bulls—ten Africander, ten Angoni, and ten Barotse—were slaughtered, and the reproductive organs were removed. The left and right testes and epididymides were trimmed and weighed. After careful removal of the tunica albugínea, each testis was homogenized at 6000 rev/min for 2 min. After recording the homogenate volume, a sample of the homogenate was diluted 1:40 v/v using physiological saline containing antibiotics. The caput, corpus, and cauda of the epididymis were minced separately with sharp pointed scissors in individual beakers containing 20 ml of physiological saline and

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G. IGBOELI and A. M. RAKHA

Summary.

Although it was generally believed that Angoni bulls (Central African Zebu) would not serve the artificial vagina, a total of 229 ejaculates were collected from ten bulls during a 6-week period. Four ejaculates were collected each week, two after 4 days' rest and two after 3 days' rest following a limited teasing procedure.

Ejaculate volume was significantly higher in the first than in the second ejaculates and higher after 4 than after 3 days' rest. The percentage of progessively motile spermatozoa in the ejaculates did not differ significantly. Over 70% of the ejaculated spermatozoa were morphologically normal. The mean total number of spermatozoa/ejaculate and sperm output/week averaged 5·6×109 and 22·6×109, respectively.

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W. E. Berndtson and G. Igboeli

Summary. The 12- to 24-month-old Holstein bulls were electroejaculated twice on each of 3 days per week throughout the study. After a 2-week stabilization period and subsequent 2-week pre-treatment period, 7 bulls were given 50 i.u. oxytocin via the jugular vein 10 min before each first ejaculate for 10 weeks. The 7 control bulls were handled identically but did not receive oxytocin. All bulls were castrated at the end of the study. Oxytocin was without effect on spermatogenesis (P > 0·10). Oxytocin did not alter the total number of spermatozoa harvested per collection day (P > 0·10), but increased the number of spermatozoa in first ejaculates by an average of 34·2% (P < 0·025). Oxytocin did not affect sperm quality (P > 0·10) as judged by the motility of spermatozoa in fresh semen or by the motility or percentage of spermatozoa with intact acrosomes in thawed semen. It is concluded that 50 i.u. oxytocin enhanced sperm output in first ejaculates of electroejaculated bulls without altering daily sperm production or seminal quality.

Keywords: bull; spermatogenesis; sperm output; oxytocin; semen

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A. M. RAKHA, G. IGBOELI and D. HALE

Summary.

A total of 333 oestrous cycles was observed in fifty-five sexually mature cattle of Central African breeds. Silent ovulation accounted for 13% of the cycles. The normal cycle lengths averaged 21·89±1·64, 22·68±3·68 and 24·25±2·27 days for the Angoni, Barotse and Boran breeds, respectively. The lengths of the corresponding oestrous periods were 16·26±1·08, 17·43±1·18 and 14·79±3·03 hr. Ovulation occurred 31·50±1·45 hr from the time of onset of oestrus. Most animals came into heat around sunrise and sunset. Cervical changes were photographed.

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A. M. RAKHA, D. HALE and G. IGBOELI

The timing of puberty in relation to the life-span governs, in part, the total number of young produced and consequently the reproductive potential. The object of the present study is to determine the age of puberty in the local breeds of cattle under the normal ranching conditions of Central Africa. The experiment included eighteen Angoni, fifteen Africander, and twenty-three Mashona heifers, and ten Hereford heifers for comparison, born in September, October and November 1967. Observations began when the animals were 9 months of age. The animals were weighed and their ovaries were palpated per rectum every fortnight. Dimensions of the ovaries, presence or absence of follicles and/or corpora lutea (cl) and changes in uterine size and texture were recorded. Oestrus was detected by young, raddled, vasectomized bulls, and animals were observed twice daily
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O. E. Okwun, G. Igboeli, J. J. Ford, D. D. Lunstra and L. Johnson

The objective of this study was to determine the number of Sertoli cells per boar, daily sperm production, and germ cell yield per type A spermatogonium in mature Whitecross, Meishan, and West African boars. The paired parenchymal mass was greatest in the Whitecross boars and greater in Meishan than in West African boars. Daily sperm production per boar (× 109) differed significantly (P <0.05) among breeds (Whitecross: 12.5 ± 1.5; Meishan: 6.0 ± 0.5; West African: 2.9 ± 0.3). Daily sperm production per boar was positively (P <0.01) correlated with parenchymal mass (r=0.97), number of A spermatogonia per testis (r = 0.88), and Sertoli cells per testis (r=0.87). Daily sperm production per gram of testis was similar among breeds. Number of Sertoli cells and number of type A spermatogonia per boar were greater for the Whitecross but similar in the Meishan and West African boars. The number of Stage VII germ cells per Sertoli cell was greater (P < 0.05) in the Meishan (39.08 ± 5.07), but similar in the Whitecross (19.91 ± 1.62) and West African boars (15.81 ± 2.43). The number of type A spermatogonia per testis was highly and positively (P < 0.01) correlated with number of Sertoli cells per testis (r = 0.95), and parenchymal mass (r = 0.88). There was a trend for the spermatid yield per type A spermatogonium to be greater in the Meishan boars, and this ratio was positively correlated with spermatid:Sertoli cell ratio (r = 0.62) but not with daily sperm production per boar or Sertoli cells per testis. No significant germ cell degeneration occurred during the long meiotic prophase, but the loss of progeny during postprophase of meiosis averaged 32.62% across all breeds. Germ cell degeneration was similar (P > 0.05) across breeds during spermiogenesis, and on average amounted to 8.6%. The increased number of type A spermatogonia and of Sertoli cells associated with larger testes for the Whitecross over West African or Meishan boars is sufficient to explain the higher sperm production in the Whitecross. However, the lower index of degeneration and more efficient Sertoli cell function in Meishan boars results in the daily sperm production being intermediate between that of the Whitecross and West African boars.