Maturation Phase

Cycle Seminiferous Epithelium

Spermatids in the maturation phase are termed Sd. This phase is the final stage of spermiogenesis and also spermatogenesis, resulting in spermatid development. During this phase the manchette continues to migrate caudally, supporting the flagellar canal. The annulus migrates to its permanent site at the junction of the mid-piece and the principal piece, drawing down caudally with it the plasma membrane of the flagellar canal. As a result the flagellar canal shortens and subsequently disappears....

Sorbitol

Sorbitol, a sugar alcohol, is also present in significant quantities in equine semen. Its function is to ensure an equilibrium in osmotic pressure between seminal plasma and the spermatozoa (Mann, 1975). It may also provide an additional source of energy. It is a normal intermediary product of the conversion of glucose to fructose. However, in the stallion the major energy source is glucose and, therefore, it is unlikely that sorbitol is present due to this conversion (King and Mann, 1959).

Seminal Plasma

Seminal plasma is the fluid fraction of semen. It may be isolated for analysis by centrifugation or filtration of the semen sample. This allows the fluid fraction to be isolated from the spermatozoa. There have not been many comprehensive studies carried out on the biochemical components of stallion seminal plasma but it is likely that it may not, in general, differ significantly from that of other domestic animals, though some differences do occur (Table 4.6). In general, seminal plasma...

The First Meiotic Division

Meiosis Stages Their

The first meiotic division is subdivided into several stages - prophase, metaphase, anaphase and telophase - usually denoted by 1 e.g. prophase 1 as they are part of the first meiotic division. Prophase is further subdivided into leptotene early prophase , zygotene middle prophase , pachytene, diplotene late prophase and diakinesis. It is a more complicated and slower process than the equivalent stage in mitosis and the prophase of meiosis 2, and so takes up the greatest part of the 18.7 days...

Citric acid

Significant concentrations of citric acid can also be identified in stallion semen. It is an organic acid, derived mainly from the vesicular glands. The concentration of citric acid in the secretions of the vesicular glands has been reported to be as high as 4 mg ml-1 but it is generally nearer to 1 mg ml-1. The concentration of citric acid in the whole semen sample varies with the contribution made by the vesicular glands, which in turn is affected by among other things season. The function of...

The Second Meiotic Division

The second meiotic division is again subdivided into prophase, metaphase, anaphase and telophase, denoted this time by 2 in order to differentiate them from those of the first meiotic division. Prophase 2 follows a short interphase prior to the secondary meiotic division. At this time the secondary spermatocytes have spherical nuclei with chromatin flakes of varying sizes. Prophase 2 marks the appearance of another spindle within the cells Kimball, 1983 . As with metaphase 1, metaphase 2 marks...

Golgi Phase

The acrosome region is an enzyme-containing vesicle and, like other enzyme-containing vesicles in the spermatid, it is developed from the Golgi apparatus. The Golgi responsible for the development of the acrosome region is evident in the Sa spermatid close to the nucleus. The Golgi produces vesicles that fuse to form a large vesicle in close association with the nucleus of a late Sa spermatid. This vesicle also produces membrane-bound enzymes. The resultant large vesicle is termed the acrosome...

Glycerylphosphorylcholine

GPC is a base found in concentrations of 0.4-3.8 mg ml 1. It is produced largely by the epididymis, and hence it is secreted as part of the sperm-rich fraction Dawson et al., 1957 Chow et al., 1986 . A significant amount of the total acid-insoluble organically bound phosphate of seminal plasma is found in GPC. GPC concentrations in epididymal secretions are reported to be in the order of 10 mg ml1 or greater. The function of GPC is unclear the fact that it is produced in the epididymis leads to...

Acrosome Phase

Plasma Membrane

Spermatids in the acrosome phase are termed Sc. It is during the acrosome phase that significant elongation of the nucleus occurs Johnson et al., 1990 . In addition, a specialized organelle, unique to spermatids, becomes evident Fig. 4.21 . This organelle, termed the manchette, is only transient. It is composed of a series of microtubules attached to each other by linking arms, and is isolated, enfolding the caudal or lower end of the now elongating ii tairut rnniiMVi a-vraz-inu ii tairut...

Testicular Size

Relationship Testicular Volume

Table 3.2 illustrated the effect that testicular weight has on output of spermatozoa and how this is related to age. Testicular weight is correlated with testicular size, which can be more easily measured, either by calipers or by ultrasonic scanning Rath and Brass, 1988 Love et al., 1991 . No adverse effect of using linear scanning has been reported Rath and Brass, 1988 . Using these methods, a linear relationship between testicular size and daily spermatozoan output DSO is evident Fig. 4.23...

Anatomy

Structure Plasma Membrane

A spermatozoon may be divided into five main sections the head, the neck, the mid-piece, the principal piece and the end-piece Fig. 4.2 Dott, 1975 Johnson et al., 1980 Johnson, 1991a Amman and Graham, 1993 Christensen et al, 1995 . The head of the stallion spermatozoon is illustrated in Figs 4.3-4.6. Several authors have reported various dimensions for the head. Its length has been reported to vary from 4.9 to 10.6 pm, with a maximum width of 2.5-3.91 pm. Fig. 4.2. A diagrammatic representation...

Physical Abnormalities

Horse Cryptorchid Testis

The major physical abnormalities that affect spermatogenesis are those that involve the testis and its function. It is beyond the scope of this book to discuss the numerous conditions in detail and so a summary of the major problems will be given. Firstly, the classification of a 'normal' stallion should be considered. It has been reported that up to one in five stallions can be considered to be abnormal in some aspect of the testes. The range is vast, from the minor to the life-threatening...

Spermatozoa

The spermatozoon is a unique cell within the stallion's body, being haploid in nature and with the unique function of fertilization. The processes involved in the production of a spermatozoon are collectively termed spermatogenesis and will be considered in detail later in this chapter. It is important to remember that the process does not end until the fusion of the nuclear material of the spermtaozoon and the oocyte takes place, rather than when the spermtozoa are released from the...

Testicular Disease Or Infection

Infection of the testes may have a systemic or localized cause. Either will result in elevated testicular temperature and associated decline in spermato-genesis. The magnitude of the decline in fertility rates and the time period reflects the severity of the disease and the duration of the problem. Recovery, when it occurs, will be somewhat delayed, as the prime site of effect, as far as spermatogenesis is concerned, is the germinal cells. The spermatogenic cycle being 56 days, this period of...