The influence of age and breed on stallion semen

This study reports on the variation in semen quality and in spermatozoal and behavioral characteristics of 168 stallions representing 9 breeds and ranging in age from 2 to 26 yr. Semen samples were collected into an artificial vagina and the number of mounts and urethral pulsations per semen sample were recorded. Semen characteristics were examined for total volume, gel-free volume, gel volume, color score, mass activity, nonmotile spermatozoa, dead spermatozoa, semen density, spermatozoa concentration, total number of spermatozoa and semen pH. Morphological characteristics of the spermatozoa included abnormal heads, abnormal mid-pieces, abaxial mid- pieces, protoplasmic droplets and abnormal tails. Sources of variation were evaluated and the overall means calculated by least-squares analyses of variance for nonorthogonal data. The significance of breed effects and between stallion variability were estimated using mixed-model procedures. All semen characteristics with the exception of color and urethral pulsations had significant variation due to age. Semen quality (gel-free volume, sperm concentration, total sperm numbers and sperm abnormalities) was poorest in stallions under 3 yr of age and over 11 yr. Significant breed variation was apparent in most cheracteristics except for pH, semen color, abnormal midpieces and urethral pulsations. It is recommended that both the age and breed of stallion be taken into consideration when evaluating stallion semen

COLLECTION OF SEMEN FROM STALLIONS AT STUD

Semen was collected from 222 stallions of 13 breed or colour types in southern Queensland and northern New South Wales. A total of 648 collection attempts were made, using an artificial vagina, during 4 consecutive breeding seasons (1974/5 to 1977/8). Modifications were made to the techniques used by previous workers because collections were made at commercial studs using minimal animal restraint. Of all collection attempts, 621 (96%) were successful, while at least one semen sample was collected from each of 216 stallions (97%). There were no significant relationships between stallion collection failures and breeding season, time of year or age and breed of stallion. Time of year (seasons and months) was the only factor having a significant relationship with collection failures; highest failure rates occurring in autumn and winter. The techniques described are applicable for breeding soundness examinations of untrained stallions and for collection of semen for artificial insemination. Copyrigh

Morphological characteristics of stallion spermatozoa

A study of the morphological characteristics of stallion spermatozoa was conducted at the semen laboratory of the Department of Animal Production during four breeding seasons. A total of 590 ejaculates collected from 216 stallions aged from 2 to 26 years and including 13 breeds or colour types was examined. Overall means for the spermatozoal characteristics of these stallions and the classes of head and tail abnormalities are presented and compared with results of other works. Scanning electron micrographs are included to illustrate recognised abnormalities

Effects of a protein deficient diet and urea supplementation on lactating mares.

Six lactating mares were fed either a low protein diet or the same diet with added urea ad libitum over 71 days. The quantity consumed by the mares, milk intakes of their foals, milk composition, plasma urea nitrogen (PUN), mare liveweight changes and foal growth rates were measured. The mares were unable to consume sufficient quantities of either diet to meet their nitrogen requirements and all lost weight. Adding urea to the diet significantly increased PUN in mares and foals, raised urea concentrations in the milk, decreased the mares' feed intake and significantly increased their weight loss. Low concentrations of protein were measured in milk from mares on both diets. Milk intakes of all the foals were reduced and they showed poor growth rates

A study of nonsurgical embryo transfer in the mare

The success rate of nonsurgical embryo recovery was influenced neither by year nor by season within years. The preferred method of nonsurgical embryo transfer was by Cassou pistolette. From a total of 15 attempts to transfer embryos nonsurgically, 9 (60%) were successful. Of the five attempts during February through April 1982, only one was successful in producing a live foal. The degree of synchrony between the ovulations of the donors and recipients in these five attempts ranged from +3 to -3 d. The recipient of the successful transfer ovulated on the same day as the donor. Eight of the ten attempts during September through December 1982 produced live foals. Synchronization of ovulations between the donors and recipients in these transfers ranged from 0 to -2 d. Repeated attempts to recover embryos had no deleterious effects on fertility of the donors

Ovarian activity in fillies treated with anabolic steroids prior to the onset of puberty.

This study investigated the effects of zero, low (0.55), medium (1.1) and high (2.2 mg/kg LW) boldenone undecylenate on the reproductive physiology of sixteen fillies from the ages of 7 to 11 months until 2 years. Ovarian activity measured by cross-sectional area, total number of ovulations, total number of follicles and the number of large follicles (greater than 30 mm in diameter) was significantly reduced by steroid treatments. Of fillies that ovulated during the first breeding season, the age of first ovulation and the second breeding season was significantly delayed in the high dose group. Final clitoral diameters and the increase in clitoral diameter over the period of the study were significantly greater in the treated groups

Milk and water intakes of foals sucking grazing mares.

Intakes of milk and milk nutrients were determined for 8 foals at 11–18 days of age and for 10 foals at 30–44 days and 60–74 days of age while sucking grazing mares. Water intakes (sources other than milk) of the foals were determined at 30–44 days and 60–74 days of age. Five of the 10 mares were fed a protein supplement (24% crude protein) in addition to grazing during the stud season. The protein supplement did not influence foal intakes of milk and milk nutrients, milk composition, weight gains of the mares or the growth rate of the foals. Foal milk intakes increased (

Synthesis and absorption of cysteine from the hindgut of the horse

The extent to which cysteine synthesised by microbes within the hindgut of the horse is incorporated into plasma cysteine was estimated by an isotopic technique in two horses fed four different diets. The results showed that between 1 per cent and 6 per cent of the plasma cysteine was of microbial origin. It is argued that the maximum contribution of microbial cysteine, and presumably other amino acids of microbial origin, to the plasma pool is 12 per cent of the net supply. These data support the hypothesis that microbial amino acid synthesis within the hindgut of the horse does not significantly affect its amino acid status

Preliminary study of ovarian activity in fillies treated with a GnRH vaccine.

OBJECTIVE: To investigate the effects of two doses (200 and 400 mg) of a water-soluble gonadotrophin-releasing hormone vaccine on the ovarian activity of 2-year-old fillies. DESIGN: A controlled vaccination dose rate experiment. ANIMALS: Six 2-year-old Australian Stock Horse fillies were randomly allocated to three treatment groups; unvaccinated controls, those receiving 200 mg of the vaccine and those receiving 400 mg of the vaccine. RESULTS: Ovarian activity of the treated fillies was suppressed at the peak of breeding season while that of untreated controls continued normally. The control fillies displayed oestrous activity and behaviour. Suppression of ovarian activity occurred for 25 and 30 weeks in the 200 and 400 mg groups, respectively. These differences were not significant. Ovarian activity ceased 2 to 3 weeks after primary vaccination. Antibody titres were low (330) until after the booster immunisation when they rapidly peaked at 22,000 and 28,000 in the 200 mg and 400 mg groups, respectively. Plasma progesterone concentrations of the treated fillies remained below 3.18 nmol/L while GnRH was suppressed. The vaccine had no significant effect on plasma androstenedione concentrations. Recovery from the effect of the vaccine was associated with development of ovarian follicles, normal oestrous behaviour and ovulation. Three of the four treated fillies and one of the controls conceived during the next breeding season and foaled normally. All the treated fillies conceived and produced normal foals in the following two breeding seasons. CONCLUSION: Both dose rates suppressed ovarian function and prevented oestrous behaviour. These effects were reversible and the subsequent fertility of the vaccinated fillies was normal

Immunocastration of colts and immunospeying of fillies

A series of experiments using an ovalbumin conjugated gonadotrophin releasing hormone was used to stimulate antibody production, suppress testosterone secretion and depress testicular function in yearling and 2 year old colts and fillies. In the preliminary experiment, an injectable oil-based formulation was administered to yearling colts. Testicular development and testosterone secretion were retarded for a period of approximately 28-32 weeks while antibody titres were greater than 1:1000. An implant and water-soluble vaccine (200 and 400 mg) is presently being tested in 2 year old colts. Testicular dimensions and testosterone concentrations decreased following vaccination. Preliminary results indicate that the effects of the implant are reversible and last for approximately 30 weeks. The water-soluble vaccine produced effective antibodies for 10-19 weeks. Plasma testosterone of all colts was reduced to gelding levels (0.2 ng/mL) while antibody titres were greater than 1:1000. Semen evaluation, morphometric analysis and daily sperm production data indicate that the testes recovered normal function. These experiments are continuing and more definitive data on the vaccine and its reversibility will be available at their conclusion. Ovarian activity of the treated fillies (200 and 400 mg) ceased soon after vaccination. Their progesterone concentrations have remained below 1 ng/mL for 20 weeks. The untreated control fillies have continued to cycle normally as determined by ovarian ultrasonography and progesterone concentrations