Module 3: Management of Ruminant Breeding Stock Flashcards
single most important factor affecting the economics and profitability of beef cattle breeding operations.
reproduction
Measures for the Bulls include;
- physical and structural soundness
- scrotal size and sperm production capacity
- semen quality, including morphology
- serving ability/ serving capacity
Measures for the cow include;
- weight and age at first estrous cycle
- the inter-calving interval
- lactation status at subsequent pregnancy diagnoses
Measures for the breeder herd include;
- branding and/or weaning rates
- kilograms of calf weaned per 100 kg of cow mated
- conception rates determined by pregnancy diagnoses (PD)
limitations to the above measures include;
- fertility cannot be assessed directly for bulls
- pregnancy status for cows required skills in pregnancy diagnosis
- branding and weaning rates do not provide
- unless birth dates are known and a restricted joining period
- important to consider that these rates must be calculated
benefits of calculating reproductive rates;
- identifying the importance of age, weight, body condition and lactation status
- identifying how management, nutrition, and breeding practices can be modified to optimize fertility.
- making an assessment of wether disease status of both cows.
Bull costs per calf weaned will depend on;
- purchase price
- bull salvage value at ultimate sale
- number of breeding seasons that involve the bull
- whether bulls are checked annually for soundness and fertility
- number of cows per bull
- weaning percentage achieved;
- bull mortality rates
four key components of bull breeding soundness evaluation (BBSE)
i. physical soundness
ii. scrotal size
iii. semen assessment
iv. serving ability
to provide an indication of likely fertility
bull breeding soundness evaluation (BBSE)
assessing a bull’s structural soundness should include a systematic examination.
Physical (structural) soundness
physical (structural) soundness should include a systematic examination of what;
eyes, and surrounding areas, jaws, mouth and teeth, limb structure, joints, stance, gait, hoof, and claw structure
common problems of physical (structural) soundness include;
post legs, sickle hocks, swollen and puffy hocks, bow legs and cow hocks.
the major factors influencing scrotal size include;
i. genotype
ii. age
iii. liveweight
iv. nutrition
v. timing of nutritional stress
common conditions that interfere with fertility and can be diagnosed by palpation of testicles include;
- unequal size of testicles
- hardness of one or both testicles
- thickened scrotal skin
- softness and flabbiness of testicles and tail of epididymis
scrotal size is a useful criterion for assessing bull fertility for the following reason;
- easily measured and is repeatable
- related to a bull’s own fertility
- genetically correlated
Key components of bull fertility;
- Bull Breeding Soundness Evaluation (BBSE)
- Physical (structural) Soundness
- Sheath, prepuce and penis
- Semen and Spermatozoa
- Libido and Serving Ability
is the sexual desire of a male to serve a receptive female.
libido
provides an indication of the bull’s ability to serve.
serving-capacity test
Puberty is defined as the time when a bull is capable of producing 50 million live sperm per millilitres.
Sexual Maturity
other factors affecting bull fertility
sexual maturity, diseases, nutrition, bull wastage
factors influencing when bulls reach puberty include;
- genetic effects
- nutritional influences
such wastage can be due to a large number of factors, including;
- structural defects
- degenerative conditions
- age structure
- reproductive abnormalities
- infertility due to testicular degeneration
- infertility due to disease effects
- traumatic injuries due to fighting
a veterinarian should carry out a BBSE to examine bulls for soundness - prior to sale or purchase, and annually for existing bulls. Such an examination involves.
- checking that the bull’s overall structure (legs, feet, and external reproductive organs) are free from defects.
- assessing the sheath, scrotum, and testicles
- measuring and recording scrotal circumference
- palpating of the testicles
- collecting a semen sample
Reproductive events in the female are marked by;
- expression of estrus
- ovulation and fertilization of the ovum
- implantation, growth, and survival of the embryo and fetus
- maintenance of pregnancy
- birth and survival of a viable calf
- adequate lactation for calf survival
- early return to reproductive activity
signs of estrus include;
- behavioural changes
- swelling and reddening of the vulva
- vaginal mucus discharge adhering to tail and legs
- abrasion of skin
- ruffling of tail hair
- increased tone
the average duration of estrus is 6-18 hours; being slightly shorter for heifers. the length of estrus is affected by:
*breed
*nutrition
*temperature stress
*age
*ovarian abnormalities
*uterine infections
