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  • Author: B. W. PICKETT x
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W. E. BERNDTSON, B. W. PICKETT and T. M. NETT

The normal equine breeding season begins in the spring and extends through mid-summer. It is characterized by marked increases in sperm output and seminal volume, as well as behavioural changes manifested in decreased reaction time and the number of mounts per ejaculation (Pickett & Voss, 1972). The production of androgenic steroids by the equine testis has been investigated both in vivo (Lindner, 1961) and in vitro (Savard & Goldzieher, 1960; Bedrak & Samuels, 1969; Oh & Tamaoki, 1970) but the testosterone level in peripheral plasma has not been reported (Lindner, 1961) and seasonal influences upon testicular function have received little attention. The object of this study was to establish the influence of season on the concentration of testosterone in the peripheral plasma of the stallion.

Two ejaculates were collected from

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J. J. LUCAS, B. W. PICKETT and R. J. KOMAREK

Summary.

Semen records of ten ejaculates from each of ten Yorkshire boars were used to estimate the boar and ejaculate variance components for eleven semen characteristics. These data were used to estimate the power of the test. In ten of eleven characteristics, a minimum of five boars and five ejaculates per boar provided at least a 90% chance of detecting a difference of 50% of the mean. For these same ten characteristics, a minimum of fourteen boars and forty-three ejaculates per boar provided at least a 90% chance of detecting a difference of 25% of the mean.

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E. E. SWIERSTRA, M. R. GEBAUER and B. W. PICKETT

Summary.

The cycle of the seminiferous epithelium of the stallion was divided into eight stages, using as criteria the presence of meiotic divisions, shape of the spermatid nuclei and location of spermatids with elongated nuclei in the tubule. The mean frequencies of stages 1 to 8 were 16·9, 14·9, 3·2, 15·8, 7·4, 13·5, 12·6 and 15·7%, respectively. The duration of one cycle of the seminiferous epithelium was 12·2 days (S.E.±0·1) as determined by injecting a single dose of 700 μCi of [3H]thymidine into each spermatic artery of six stallions and removing testes at different intervals after the isotope injection. The life-span of primary spermatocytes was 19·0 days, secondary spermatocytes 0·7 days, spermatids with round nuclei 8·7 days, and spermatids with elongated nuclei 10·1 days. Radioactive spermatozoa were observed in the caput epididymidis 35 days after [3H]thymidine injection. The volumetric percentages of testicular components were: spermatogonial nuclei, 0·6; primary spermatocyte nuclei, 4·2; secondary spermatocyte nuclei, 0·1; round spermatid nuclei, 2·1; elongated spermatid nuclei, 1·0; Sertoli cell nuclei, 1·6; tubular cytoplasm, 45·7; lumina, 3·4; basement membranes, 2·6; and intertubular spaces, 38·7%. The seminiferous tubules made up 61·3% of the testicular volume. The diameters of the seminiferous tubules varied significantly among stallions, but not among stages. The average length of the seminiferous tubules per testis was 2419 m (range 1667 to 3726 m).

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S. GOMBE, W. C. HALL, K. McENTEE, W. HANSEL and B. W. PICKETT

Summary.

Histological studies of adenohypophyses of male Friesian and Ayrshire calves, aged 1 to 2 months, and measurements of plasma or serum LH by solid phase radioimmunoassay in Angus, Holstein, Guernsey and Jersey bulls, ranging in age from 7 months to 2 years were carried out to determine factors influencing gonadotrophin secretion. The gonadotrophin-secreting delta cells constituted 3% of the cell population of the cortical region of the adenohypophyses at 1 month of age and 4% at 2 months of age. Considerable quantities of LH (3·7±0·3 ng/ml) were present in plasma samples of Angus bulls at 7 to 9 months of age. The levels rose to 4·3±1·1 ng/ml at 12 to 14 months and, at 2 or more years of age, basal LH values were of the order of 7 to 10 ng/ml plasma or serum. No breed differences were noted either in pituitary histology or LH concentrations.

Teasing and ejaculations caused no increase in serum LH values for up to 3 hr after sexual excitement, irrespective of whether a bull or an oestrous cow was the teaser. Large irregularly occurring daily fluctuations in serum LH (0 to 50 ng/ml) were found in 6-year-old Holstein bulls. Similar but smaller variations (1 to 16 ng/ml plasma) were found in the younger Angus bulls aged 7 to 14 months. A distinct 24-hr variation in serum LH was found in two Holstein and two Guernsey bulls aged 1½ to 2 years. The diurnal serum LH values were twice the nocturnal values, an abrupt change-over occurring at 18.00 hours when most of the bulls were lying down. Hourly variations were small and insignificant during the morning and afternoon.

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R. J. KOMAREK, B. W. PICKETT, E. W. GIBSON and R. G. JENSEN

Summary.

In forty-one ejaculates from six boars totalling 7·5 1. the spermatozoa, analysed on an individual ejaculate basis where possible, contained an average of 12·0% lipid which was composed of phospholipids (74·7%), cholesterol (12·6%), diglycerides (5·7%), triglycerides (4·5%) and wax esters (2·4%). Only a small portion of the dry matter of seminal plasma was lipid (0·23%), which was composed of phospholipids (64·7%), cholesterol (17·7%), diglycerides (5·8%), triglycerides (5·3%) and wax esters (6·5%). The gel fraction contained 0·32% lipid, composed of 51·6% phospholipid, 28·3% cholesterol, 6·3% diglycerides, 6·0% triglycerides and 7·8% wax esters.

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R. J. KOMAREK, B. W. PICKETT, E. W. GIBSON and R. N. LANZ

Summary.

Twenty-nine ejaculates of semen were collected from five stallions (four thoroughbreds and one quarterhorse) for this study. The volume of semen, cell count and gel volume/ejaculate averaged 105 ml, 143 × 106/ml and 36·8 ml, respectively. Dry matter content of semen was 3·00%, gel 2·84% and seminal plasma 2·77%; while micrograms of dry matter/106 cells averaged 19·8. The lipids from spermatozoa, seminal plasma and gel from each ejaculate were extracted, and the pooled lipid samples of each fraction were analysed quantitatively for the major lipid classes. Spermatozoa contained 14% lipid, while the seminal plasma and gel contained 2·07% and 2·10%, respectively. The spermatozoal lipid contained phospholipid (58·7%), cholesterol (13·7%), diglycerides (9·0%), triglycerides (8·0%), and wax esters (10·6%). The seminal plasma and gel contained the same lipid classes and the percentages of each were in the same order as above, for seminal plasma: 74·4, 12·1, 3·6, 3·2 and 6·7; for gel: 75·0, 10·0, 5·3, 4·3 and 5·4.