Reproduction

Pregnancy Diagnosis

Rectal palpation has been the standard method of pregnancy testing cattle for many years. This involves using a gloved hand and arm to palpate the reproductive tract of the cow through the rectal wall. Over many years and hundreds of thousands of cattle, the use of manual palpation is still the gold standard for pregnancy diagnosis. An experienced veterinarian can diagnose pregnancy from 35 days of gestation. In addition an experienced veterinarian can provide a vast combination of information while pregnancy testing, from nutrition and management practices to information on breakdowns in fertility, bull problems. In most cases a veterinarian will also provide additional services while on property, for example equine dentistry or pregnancy diagnosis, dog vaccinations and other services.

In recent years ultrasound has been used more commonly as a method of pregnancy testing. Ultrasound produces a black and white picture of the uterus and embryo being scanned using reflected sound waves. Although it is possible to scan the uterus through the abdomen (externally), most pregnancy diagnosis is performed by passing the ultrasound probe into the rectum (either in the hand or on an extendable arm) and examining the uterus through the rectal wall.

The advantages of each system
There is often a misplaced belief that ultrasound is better or more accurate than manual pregnancy testing.

Manual palpation is a proven, safe and reliable system of diagnosis that is suitable for all cattle at all stages of pregnancy. An experienced operator can give results that are 100% accurate on whether a cow is in calf or not and with early foetal aging can be accurate to within about two weeks. Foetal age can be, and is often now assessed later in pregnancy, although the aging becomes slightly less reliable. Manual pregnancy diagnosis needs very little equipment and no power source.

Ultrasound’s big advantage is less operator fatigue, especially when testing on rotary dairies for example. Speed is often cited as an advantage but speed of testing will depend on many factors, including facilities, pregnancy rate, time of pregnancy, how fat the cows are etc. In the right conditions ultrasound can be significantly quicker than manual testing, but in reality the conditions often mean there is no difference. In the “ideal” animal, ultrasound requires less skill than manual palpation.

The disadvantages of each system
Operator fatigue is the biggest disadvantage of manual palpation. This is most pronounced in good facilities where the throughput is rapid so the arm does not have time to recover between cattle.

Injuries to the testing arm are also relatively common. These include over-extension injuries of the elbow joint and the arm being bashed against a rail. Long term there is also the risk of chronic repetitive strain type injuries. These can be minimized by good technique, but eventually affects most operators. Acquiring and maintaining the tactile skills for manual palpation takes time and a large number of examinations.

The biggest disadvantage of ultrasound is that it is not very specific for non-pregnants. The empty uterus contains no fluid, so is often hard to visualize, especially in fat animals. This leads to the other main disadvantage meaning only rarely can a group of cattle be pregnancy tested without having to use manual palpation to clarify the status of individual animals. Some reasons that manual pregnancy testing may be needed include: too deep, too fat, small uterus hiding next to the bladder, poor probe contact due to dry faeces, air or pelvic shape are all reasons a percentage of cattle cannot be satisfactorily examined by ultrasound. This can vary from 2 % of cows examined to 30% or more in certain groups.

The variability between cows means acquiring good ultrasound skills to be able to assess animals that are not “ideal” takes a lot of training and practice. Foetal aging also takes experience and is unreliable once the foetus is too deep to visualize. The stage this occurs can vary, but is normally > 4 months of gestation. If the pregnancy is too deep, manual palpation must be used to confirm the stage of pregnancy.

Other disadvantages of ultrasound include the cost of the equipment, cost of repairs, and the need for a power supply with some machines. Heat also affects some machines, resulting in poor image quality.

The National Cattle Pregnancy Diagnosis Scheme
The NCPD Scheme has been developed over a number of years to promote excellence in the skills of pregnancy diagnosis among cattle veterinarians. Cattle veterinarians that have passed a practical examination conducted by an accredited examiner are then accredited to use the NCPD tags on cattle they pregnancy test for their clients. This scheme ensures accuracy and traceability. Accredited pregnancy testers must have performed at least 2,000 manual pregnancy tests and prove to the examiner they are 100% accurate on pregnancy status and within the agreed tolerance for foetal aging. Examiners must have performed 40,000 + pregnancy tests and be approved by the ACV as examiners. Ultrasound accreditation can be achieved also, with manual accreditation as a prerequisite.

Bull Soundness Examination & Bull Testing

It is easy for producers to focus their efforts and resources on female fertility within their breeding herd, resulting in the genetic selection of herd sires to be overlooked. Selection of sires on appearance alone has seriously limited the Australian beef industry rate of gain.

The Australian Association of Cattle Veterinarians have determined that fertility is the ability of a bull to achieve, by natural service, a pregnancy rate of 60% and 90% in 50 normally cycling females, within three and nine weeks of mating, respectively.

Tableland Veterinary Service offers the service of Bull Breeding Soundness Examinations (BBSE) to producers and studs by experienced and qualified veterinarians.

The BBSE was developed to standardize bull fertility testing and to provide a consistent measure of bull fertility. The evaluation requires a bull to meet a set of standards for key fertility components, which indicate whether a bull has a high probability of being fertile.

The components are:

  • Scrotal circumference and tone or resilience
  • Physical examination for faults in the head, legs, joints, feet, sheath and penis
  • Semen analysis for motility
  • Morphology (or structure of the individual sperm cells)
  • Serving Ability (Not routinely carried out with Bos indicus bulls)

A summary of the five components of bull fertility in the BBSE follows:

  • Scrotum – Scrotal circumference/size in centimetres where testes shape is within normal range. The minimum values depend on breed and age of the bull.
  • Physical – Within the constraints of a standard examination, there is no evidence of any general physical/structural condition or of a physical condition of the reproductive tract indicating sub-fertility or infertility. This evaluation will identify structurally unsound bulls in legs, feet, sheath and general structure.
  • Semen – Crush-side assessment indicates that the semen is within normal range for motility, colour and percent progressively motile and is suitable for laboratory evaluation.
  • Morphology – Semen examination of percent normal sperm using high power magnification to ensure minimum standards for normal function are achieved.
  • Serving – The bull is able to serve normally as demonstrated in a standard test and shows no evidence of fertility limiting defects.

Morphology – why it is important!

  • Morphology in a BBSE is basically the ‘structure’ of individual sperm cells. The structural attributes that require a specialised microscope to view are frequently just as important, if not more important as far as affecting a bulls fertility.
  • These attributes are important as they can affect the ability of individual sperm to move within the female reproductive tract, and the ability of sperm to fertilise an egg
  • Bulls continuously produce semen within the tubules in the testicles. The testicles are about 2ºC cooler than body temperature. Between the head, body and tail of the epididymis there is a long tube for storage and maturation of the spermatozoa produced. This production pipeline takes about 6-8 weeks from the start of production to when the semen is ready for ejaculation. As semen is continually produced, unused semen is excreted in the urine of all bulls.

Tableland Veterinary Service strives to improve producer profitability and productivity by promoting BBSE and reproductive performance of females. We recommended that bull buyers request a complete BBSE when sourcing bulls. It is important to note that a bull with unknown fertility (and genetic merit for fertility) is going to affect herd function and profitability well into the next decade.

For more information on our reproduction services, please contact your nearest Tableland Veterinary Service clinic today.