As alluded to earlier, animal performance is based both on genetics and the environment. Producers can adjust weaning weights in order to compare individual lambs born the same farm, since these animals have theoretically all been exposed to the same environmental conditions.
The estimated day weight can then be adjusted for more factors. The following table lists adjustment factors to account for the age of the ewe, sex of the lamb, birth type, and rearing methods for three breeds of sheep Targhee, Suffolk, and Polypay as well as generic breed adjustments. This handbook can be purchased through the American Sheep Industry Association and through select sheep supply companies. A twin ewe lamb was born on January 2 nd , weaned on March 4 th , and was raised as a twin.
The dam is 2 years old. Therefore, the adjusted day weight of this ewe lamb is This calculation allows producers to better compare lambs and make more informed selection decisions.
The Sheep Production Handbook also contains tables for adjustments to adult fleece weights for ewe age and for the expected number born adjustments for ewe age. In addition to using individual performance and EBVs, anyone involved in sheep production should have the skills to evaluate the physical characteristics of individual rams for their potential as breeding stock.
Producers should be able to visually evaluate sheep structure and they should also be able to evaluate muscling. In order for a ram to be sound on his feet and legs, he must be structurally correct.
Correct structure enables the ram to move properly and proper movement allows rams to comfortably mount ewes during breeding. To be able to evaluate or select structurally correct rams, producers must first have an understanding of the parts of a sheep as well as each part's correct structure.
Remember, selection should begin with a look at performance records followed by visual evaluation. Visual appraisal can be a good indicator of frame size, muscling, body structure, feet and leg structure, and breed character. Correct skeletal structure is important and essential for any animal to move to feed and water. This structure can be observed in shoulder angle, pastern angle and levelness of the hips and top line from neck to dock.
The angle of the shoulder should be approximately 45 degrees, while the pastern angle should be approximately 50 to 55 degrees or slightly more. Skeletal angles in the shoulders, hips and legs are all important for ease of movement. When angles are within appropriate ranges, the animal is generally level across their topline and able to move freely.
When making visual selection decisions for correct structure, it is important to know all the external parts of a sheep. Each part has an ideal characteristic for breeding rams. Producers should select rams that possess correct structure as well as other visual characteristics and good performance data.
There are a number of undesirable feet and leg characteristics that animals can exhibit. As you evaluate animals, you should be aware of these issues:. Pigeon toed : An animal is pigeon toed or toed-in if when viewed from the front, the toes turn towards each other rather than pointing straight forward.
Bowlegged : An animal is bowlegged if when viewed from the front, the knees curve out away from each other or if viewed from the rear, the hocks curve out away from each other. Splayfooted or toed-out : An animal is splayfooted or toed-out if when viewed from the front, the toes turn out away from each other rather than pointing straight forward. Knock-kneed : An animal is knock-kneed if when viewed from the front, the knees lean toward each other and are not in a straight line with the legs.
Cow hocked : An animal is cow hocked if when viewing the hind legs from the rear, the hocks, which are the hind leg joints, are turned inward or are placed too close together. This causes the toes to turn outward. Sickle hocked: An animal is sickle hocked if when viewing the rear legs from the side, the hock has too much angle or set.
A line dropped perpendicular from the pin bones to the ground should lie parallel to the cannon bone. A sickle hocked cow has hocks that angle too much, which causes the animal's feet to stand too far underneath their body.
Often these animals will droop excessively from hooks to pins. Post legged: An animal is post legged if the hock has too little angle or set. The animal is too straight through the joint, which results in a very stiff, restricted movement due to the lack of flexibility. More sheep become unsound because of being post legged than sickle hocked. Buck kneed : An animal is buck kneed, or "over at the knees", if the full extension of the animal's knee cannot occur.
When observed from the side, the legs appear slightly bent. This is usually seen in sheep that are too straight in the shoulder. Calf kneed: Calf kneed is the opposite of buck kneed. This means that the animal stands "back at the knees" when viewed from the side. Weak pasterns : Weak pasterns, which are the leg bones between the hoof and fetlock, can be determined by visually looking at their angle.
Weak pasterns have more than the normal slope to them and can indicate a structural fault. As mentioned previously, correct pastern angle should be approximately 50 to 55 degrees or slightly more. Sound hind legs are vital to the mating ability of rams, because during mating, most of the ram's weight is supported by the hind legs. A ram with hind leg defects may suffer pain while moving or mounting, which may interfere with his desire to mate.
In an aging ram with faulty conformation, defects become more apparent and may tend to decrease their ability to breed larger groups of ewes. The ram's legs should be free of excessive swelling at any of the joints, and joint flexure should be smooth and free of locking in any position. A sheep with straight hind legs, or post legs, is predisposed to swollen hocks and arthritis in the hind leg joints. A sheep with post leg or sickle hocks also may have more difficulty moving earlier in life, leaving it lame or unable to move freely throughout a pasture or, in the case of rams, to breed ewes.
Other visual characteristics to consider when evaluating rams relate to how filled out the animal may appear. Rams selected for breeding should exhibit volume and capacity. Indicators of volume are:. Sheep with more volume are generally easier fleshing. That is, they produce external fat easily and are usually lower maintenance than sheep that lack volume. Rams should be selected with volume in mind in order to transmit these traits to offspring. The muscling of an animal is also important to the meat animal industry.
Heavily muscled animals tend to produce more meat and less fat than animals with less muscle. Consumers prefer lamb with larger loin chops and with less fat. Some rams produce a lot of lambs while others produce very few. In any group of rams there will always be a wide variation in the serving capacity of individual animals, ranging from very high to very low.
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Ram desire, ability and stamina Your rams' productivity will also be affected by how they want to mate, and their physical ability to perform during joining. Ram desire and mating Desire, or libido, refers to a ram's urge to mate. Ram nutrition and mating You must ensure your rams receive good nutrition, as poor nutrition will affect sperm production and reduce libido. Ram age and desire to mate Age also affects a ram's desire to mate. Mating ability A ram's success rate in inseminating ewes is known as its mating ability.
Mating stamina Stamina, or serving capacity, is a combination of libido and mating ability, and refers to the paddock mating performance of a ram.
Also consider Learn more about sheep health and disease prevention. Curling the lip is called the "flehmen response. The ram may fail in several initial attempts to mount the ewe. He may repeatedly mate the same ewe. Rams will tend to select older ewes over younger ewes and sometimes will choose ewes of their own breed over ewes of another breed.
Some producers prefer to use one ram per group of ewes. If more than one ram is used, the older ram s will usually dominate the younger ram s and may prevent the less dominant ram s from breeding. The rams may fight at the expense of mating ewes. It will be more difficult to detect infertile rams or male-oriented rams in multi-sire situations. In large flocks, multi-sire matings are usually necessary. On the other hand, single-sire matings run the risk of low conception rates or an extended lambing season if a ram with reduced fertility or libido is used.
Breeding Soundness Exam Preparing a ram for breeding should start well in advance of the breeding season. You should never wait until the last minute to purchase or select rams or check their readiness for breeding. Rams should be purchased at least several months before the start of the breeding season. The purpose of a breeding soundness exam BSE is to evaluate a ram's potential breeding ability. While only a low percentage of rams are sterile, many rams have reduced fertility.
Research has shown that 10 to 15 percent of rams that are given a BSE fail or have questionable fertility. A BSE should be conducted by a veterinarian or other trained individual. The BSE consists of two parts: a physical examination and a semen evaluation. Rams should be evaluated for lameness, body condition, and any other physical defects which could interfere with the breeding process. Rams need to be free from footrot or foot scald, and if necessary have their hooves trimmed prior to being joined with ewes.
The general health of the ram should be evaluated by observing his eyes, feet, legs, prepuce, and penis for any defects that could interfere with breeding. The testes and epididimides should be palpated. A testicle that has scar tissue or is abnormally small will reduce the breeding capacity and endurance of the ram.
Swelling of the epididymis could be an early indication of epididymitis Brucella ovis. Scrotal circumference Scrotal circumference width of the testicles at the widest point should be measured as it gives a good indication of a ram's breeding ability. Scrotal circumference will vary with season and body condition, but should be at its maximum peak during the fall breeding season. Ram lambs with a scrotal circumference of less than 30 centimeters and adult rams with a scrotal circumference of less than 32 centimeters should probably not be used for breeding.
There is some evidence to suggest that rams with larger testicles will sire more prolific ewes and that his offspring will reach puberty earlier. Increased scrotal circumferences have been associated with increased ejaculate volume and sperm motility in mature rams.
There is a correlation between scrotal circumference and body weight in all breeds. Differences of up to 30 percent have been observed in rams in spring and autumn. The table was developed for US range rams.
Standards may be different for smaller breeds or breeds in other countries. For example, Swedish researchers recommended a minimum scrotal size of 26 and 28 cm, respectively for ram lamb and mature rams of the Gotland breed. In the UK, there are different standards for lowland vs. Semen samples can be collected using electro-ejaculation or via an artificial vagina. Usually veterinary assistance is required to collect semen.
Semen should be evaluated for sperm motility, morphology, and white blood cells. The minimum acceptable standards are fair gross motility or 30 percent individual motility and 70 percent normal morphology. White blood cells in the semen are an indication of infection e.
A BSE does not include an evaluation of a ram's sex drive or breeding behavior. Libido sex drive The willingness to breed ewes is highly variable among rams and can have a major impact on sheep production, especially in a single-sire mating scheme. Libido is a ram's desire to mate. It is regulated by the release of testosterone, produced by specialized cells in the testes.
Some breeds of rams show libido almost continuously once they reach puberty. In other breeds, there is a marked decline in libido during the non-breeding season.
Underfed and overfat rams may show reduced libido. A ram's desire to mate also decreases with age and disease conditions, such as arthritis. Some rams have inheritantly poor libido. In fact, studies have shown that up to 15 percent average of 8 to 10 percent of rams are homosexual and will not mate with ewes. Unlike heterosexual males, male-oriented rams do not experience an LH surge when exposed to estrus ewes. They also have a reduced capacity for producing testosterone. Animal scientists are hoping to develop a blood test which would identify rams that will not mate with ewes.
There is some evidence to suggest that rearing rams in an all-male environment may have a detrimental effect on mating behavior. A "serving capacity test" can be conducted to determine a ram's desire to mate ewes. In a serving capacity test, rams are exposed to estrus ewes, and their breeding activity is recorded over a period of two weeks or more. Research has shown that a serving capacity test is useful for identifying low and high-performing rams. Ram serving capacity may be affected in utero by number and sex of siblings.
Rams born as co-twins were shown to have the highest serving capacity and single born rams the lowest. In another study, long-term selection for reproductive rate in ewes did not affect mating behavior in male offspring.
However, serving capacity or breeding behavior is a heritable trait. The simplest way for a producer to evaluate mating behavior is by observing breeding performance as rams are exposed to ewes.
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