The Simbra Breed

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In his overhead value assessment and setting of a breeding goal, the Simbra breeder must always bear in mind the following relative economic values pertaining to extensive beef production:  REPRODUCTION/FERTILITY = 10; PRODUCTION (WEIGHT GROWTH) = 2 and PRODUCT (CARCASS) = 1.

Only cows that are adapted to their environment calve regularly, and they can only be adapted if they have the desired correct legs, hair coating, size, length, rump, etc. as dictated by nature.  BY SELECTING FOR REPRODUCTION, YOU ARE IN FACT ALSO INDIRECTLY SELECTING FOR STRUCTURAL SOUNDNESS. 

“Select for fertility and the rest will follow.  Unbelievable! Yes, but accountable.”  (Reini Rusch).

The fertile heifer/cow

No judge can “see” the reproduction rate – therefore we make use of the annual Simpro herd analysis and indicate the Simbradex on the show cards.  Breeders must nevertheless be aware of the following (from a lecture by Cas Maré):

    ■  Forequarter:  Femininity and high fertility are associated with a wedge-shaped body with the deepest point through the body, the belly, being close to the udder, with a
        wedge-shaped narrowing to the front, starting at the first rib.  The fertile cow has an inconspicuous brisket and large belly girth and shows no heavy muscle development
        in fore- or hindquarters.  This is in direct contrast with the bull where a well-developed forequarter and a narrow, but well- muscled hindquarter are typical masculine
        characteristics. 
    ■  Fat:  Cattle that are too fat have lower fertility and infertile cattle get fat.  The actual producers are never fat.  The low fertile heifer is usually big, heavy and fat and appears
        masculine.  Fertile cows are not big and beefy in conformation and cows should therefore never be judged for beef or carcass characteristics.
    ■  Size:  Extremes in size, both small and big, should be avoided, although the reasons for doing so could differ.  The low fertile heifer is usually big and heavy.  
    ■  Shoulder blades hump:  In the fertile cow the hump and neck are lean in appearance. The highest point of the shoulder blade bones is slightly muscled and moves
        alongside and protrudes above the dorsal vertebrae when the animal moves.  In the description of excellence of many breeds one does, however, find that “looseness of
        shoulder” is considered an undesirable property.  There is, however, no evidence that a loose shoulder has ever been detrimental.  In fact – a well-muscled firm shoulder
        or a rising dorsal vertebra in a cow is an indication of low fertility.
    ■  Udder:  Early signs of infertility that are normally treated with a good measure of suspicion are:  shrunken teats sunk into the udder, long hair and underdevelopment of the
        udder.  By the way, visual appraisal of the udder is of no value in determining milk production, but sustained milk production is at least dependent on the functional
        effectiveness and conformation of the udder.
    ■  Sex organs:  A sign of questionable fertility (even if the animal is presently in calf) is underdevelopment of the external genital orifice with fat deposit around the tail head.

The fertile bull

In a bull there are some visually assessed properties which are a prerequisite for high fertility.  According to C. Maré positive signs of male hormone excretion are normally associated with the following:

    ■  Muscle definition and heavy forequarter development .
    ■  A well-developed and heavy and muscular hump.
    ■  Masculine behaviour,  traction and retraction of testicles.
    ■  Movement of the sheath and coarse hair growth on sheath and switch.
    ■  Coarse hair growth on head and neck

Concerning the latter, the opinion of Drayson, who studied 15 537 bulls from 19 breeds, is as follows:  “Look first at the coarseness of hair on a bull’s head and face.  The most fertile bulls generally have quite coarse and curly hair, with the hair most tightly curled when the bull is at his peak of sperm production between three to seven years of age.  How curly is “curly”? If you take a curl of hair strand between your thumb and index finger and pull it straight, it immediately returns to its curly position when you release it.

Coarse, straight hair is a step down the fertility ladder, although the bull should still have good fertility.  But, be careful of a bull with fine, straight hair.

The same principles apply to neck hair as to head and poll hair.  Coarse and curly hair suggests the bull is highly fertile.”

Bulls should be fit and not fat

Coetzer
sums up his research regarding the above as follows:  “Excessive fatness in bulls can lead to fat deposit in the scrotum which can hamper thermo regulation, leading to possible semen deformities.  Furthermore, bulls that are too fat are more inclined to develop leg and hoof problems which decrease libido.  Another problem with such bulls bought at an auction is that the new owner often tries to slim down the bull by drastically reducing the energy intake and sometimes also immediately starts with mating.  The metabolic challenge that fat catabolism poses to the bull, in addition to the novel experience of an unfit bull having to defend himself against a new group of bulls, more often than not leads to failure of such a bull to produce progeny for several months.  While overfeeding is more detrimental, underfeeding can negatively influence semen production and libido.”

In his studies on fat Coulter found that “the fat bulls in our tests showed a reduction of 50% sperm reserves, half as many mobile sperm, one third as many normal sperm and eleven times less services.” 

Richardson also studied fat bulls and summarises his findings as follows:  “High energy rations fed to young bulls in order to achieve rapid growth rates or fatten the bull for a show does adversely affect reproductive characteristics of the bull.”

Pruitt reports as follows:  “Bulls fed high gaining rations often lay down fat in the scrotum, and this results in lower fertility.  The testes normally maintain a temperature four to six degrees cooler than body temperature.  If fat deposits develop in the neck of the scrotum, the countercurrent heat exchange, where warm blood from the body is cooled by the blood in the testes, is disrupted.  Sperm production is not normal at higher temperatures and results in impaired reproductive traits. “ 

The business end of a bull

“When I buy a bull, I always start by looking at the back end of the bull.  That’s where the business end is.  I want to see large testicles and a well shaped scrotum.  That’s the most important part of a bull.  No matter how good he is otherwise, if he can’t sire calves, he’s no good to me.  It doesn’t matter if he’s the best walking bull in the world if he hasn’t got the equipment to do the job.”  (Anonymous)
. 

Lusby; Hunlun; Curtis; Bosman and Morrow all found that the reproduction potential of a bull depends largely on the appearance and size of its scrotum.  The high correlation with semen production, semen quality and puberty of daughters stresses the importance of scrotal circumference.  Of the discriminatory scrotal deviations that judges should take heed of are portrayed in our  basic principles of judging.  From a genetic point of view, it is mainly hypoplasia (underdevelopment of one or both testes) that is undesirable.

Our Society has, from as early as 1985, been prescribing minimum testicle circumference per weight requirements, since scrotal circumference is, according to above-mentioned researchers, positively correlated with semen production, semen quality, puberty of bull and puberty of daughters.  The correlations below were found in British beef breeds:

Scrotal circumference

30

32

34

36

38

% good semen

13%

20%

52%

65%

95%

On our Breedplan 400-days’ weighing lists there is space for scrotal circumference and this important BLUP breeding values will be provided to breeders that are already measuring all their bulls (between age 350 – 550 days).  Scrotal sticks are available from inspectors.

Twisted scrotum

The effect of scrotal twisting on the fertility of a bull has been debated in many judges’ circles.  In a subjective evaluation of 15 beef breeds at 15 phase C bull testing centres, Van Rooyen found that 54% of the bulls had displayed scrotal twisting (87% to the left).  According to him semen tests had proved beyond doubt that scrotal twisting has no negative effect on normal testicular development or functions.  It was also found that scrotal twisting is indeed moderately to highly heritable in male progeny.  The stud industry should look with cautious seriousness at scrotal twisting. Testicular torsi is the twisting of testes within the scrotum and must not be confused with scrotal twisting (twisting of the entire scrotum).  T. torsi is a painful condition with direct detrimental influence on the function of the testes.

This you cannot see

An important but visually not observable problem is a lack of libido with resulting low conception.  Causes I have come across in the literature are, amongst others:

    ■  Heritibality (Johansson en Rendel).
    ■  Too heavily used at too early an age (Neumann).
    ■  The well known too much or too little:  overworked, overfed, underfed, used too soon in a new environment (buying) and of course any condition of ill health  (several
         researchers
).

Since infertile and poor quality semen is not visible in the bull, we make testing compulsory for sales under the rules of the Society. 

CP Massmann, 2003

 

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