Nutritional Needs of the Stallion

by EQ

Stallions will need more energy during the breeding season as most will increase their daily voluntary exercise, such as walking paddock fences, in anticipation of breeding. Forage, usually in the form of hay, should be provided at minimums of 1% of body weight per day (4.5 kilos of hay for 450 kilos of weight). Grain should supplement the forage at levels to maintain a moderate body condition. Body condition can be estimated visually by the level of fat cover on the stallion’s neck, back, ribs, shoulder, and croup. Typically, condition level should allow for enough fat cover so that individual ribs are not seen, the croup appears rounded, and the neck and shoulders blend smoothly into the body.

Breeding management factors affecting daily spermatozoa output

The role of a breeding stallion is to impregnate mares. This means producing semen containing adequate quality and numbers of spermatozoa to fertilise a mare’s ovum. Spermatozoa are produced daily in the seminiferous tubules of the stallion’s testes. The testes are housed in the protective covering of the scrotum, which functions to regulate the temperature of the testes. Temperature regulation is important because abnormal rises in temperature – such as those caused by injury of infection – will decrease spermatozoa production. Since stallions need about fifty-seven days to produce mature spermatozoa, injuries and infection can have long-term effects on the breeding season.

Testicular size is a good indicator of sperm production capability; stallions with larger testicles will normally have larger daily spermatozoa output. As such, measurement of scrotal circumference is one of the procedures that veterinarians conduct as part of a breeding soundness exam. Total scrotal width is smaller in two to three year old stallions than in their older counterparts. Stallions that are two or three years old are expected to have smaller daily sperm outputs and spermatozoa reserves. Due to this sexual immaturity, two year old stallions should be limited to breeding a small number of mares, if any at all. Otherwise, conception rates will be undesirable because of low spermatozoa numbers, and the stallion may develop a low sex drive from overuse. Even though spermatozoa production begins as early as twelve to fourteen months of age in most colts, results of numerous research trials recommend waiting until the stallion is three years old before using him as a breeding stallion.

Daily spermatozoa production is also influenced by season. Lowest production, a decline of about 50% from peak values, is expected from March through August. Production of spermatozoa increases as daylight grows longer in September, peaks in November and December, and then declines significantly in January and February. Artificially extending the length of the day by using lighting programs will enhance a stallion’s semen production.

Stallions will typically remain fertile beyond their twentieth year of age. The age that stallions stop producing spermatozoa will vary between stallions. It is important that semen is routinely evaluated on all stallions, especially when using older stallions because of the expected decrease of semen production with age.