Evaluation of Livestock

ANSC 401

selection

the process of choosing an animal to be a parent, champion at a show, etc.

evaluation defined by Webster

to determine the significance, worth, or condition of usually by careful appraisal and study

evaluation defined by Murphey

the use of objective and subjective criteria and measurements in order to determine the value of the animal itself

areas of evaluation

• visual

• performance

• breeding values

visual evaluation is subjective and tends to follow _____ or _____ of the time

trends; styles

evaluate in terms of sex

• bulls

• replacement females

• market cattle

what all do you look for during visual evaluation?

• structural correctness

• muscling

• leanness/fat thickness

• frame size

• capacity

• fleshing ability

• sex character

• breed character

what are the areas of performance evaluation for cattle?

• birth weight

• cow efficiency

• calving interval

• weaning weight

• yearling weight

• average daily gain

• feed efficiency

• mature weight

• carcass measurements

cow efficiency

evaluation that’s determined by dividing the weaning weight of the calf by the weight of the cow at weaning

what should the value of cow efficiency be?

50%

calving interval

the time from one calf to another; should be less than 12 mo apart

weaning weight

weight taken at 205 days or adjusted to 205 days

yearling weight

weight taken at 365 days or adjusted to that date

average daily gain

average pounds of gain per day between two set dates

feed efficiency

measures an animal’s ability to convert feed

carcass measurements

• marbling score

• rib eye area

• fat thickness

number of cows exposed

the number of cows exposed for either artificial or natural service in the present year’s breeding season

conception rate

number of cows pregnant

live calving percent

this is a measure of the success of the cumulative results of the breeding and calving seasons

weaning percent

this measure is also frequently called “percent calf crop weaned”

what is weaning percent recognized as?

the most descriptive single measure of reproductive efficiency

what is the most important concept in male reproduction?

to make sure that no bull being used has problems of fertility

what are the recommended procedure to identify the bulls that’ll be problem breeders?

• physical examination

• scrotal circumference

• semen evaluation

• breeding soundness

physical examination

a competent evaluator should examine each bull for an injury/abnormality. they must evaluate:

• scrotum and testes

• rectal palpation of the internal glands

• examination of the extended penis and prepuce

scrotal circumference

the circumference is an indicator of the bull’s ability to produce sperm and is related to age at puberty in the bull itself, as well as the bull’s daughters

what is an acceptable circumference of a yearling’s scrotum?

at least 30 cm

semen evaluation

percent motility and a description of the morphology should be recorded

breeding soundness

scrotal circumference and the semen should be assessed in comparison with the scoring system recommended by the Society of Theriogenology

what form are breeding values most commonly used in?

expected progeny differences (EPD’s)

where are breeding values recoreded?

in sire summaries

what animal most commonly uses breeding values?

beef and dairy cattle

what’s the point of large scale genetic evaluation?

allows genetic comparison of animals in different flocks; gives an objective way to compare animals in the entire breed

how does large scale genetic evaluation speed up the rate of genetic change?

allows selection from a larger more knowledgeable pool of animals and by increased the accuracy of predictions

sire summaries

a list of genetic predictions, accuracy values and other useful information about sires in a breed

accuracy

a measure of the strength of the relationship between predicted value and the true values

possible change (PC) or standard error of prediction

a measure of the accuracy indicating the potential amount of future change in a prediction; similar to accuracies but not as easy to understand

what is the importance of sire summaries?

• allows for selection

• marketing tools of desirable EPD’s

the importance of selection when using sire summaries

• expands the pool of available sires which increases selection intensity

• using large amounts of data for genetic predictions thus increasing accuracy

• may allow easier management of sire selection risk by being able to identify and use more predictable sires

selection intensity

a measure of how “choosey” breeders are in deciding which individuals are selected

what are the types of EPD’s?

• parent EPD

• nonparent EPD

• pedigree estimate

parent EPD

an EPD for an animal with progeny data. parent EPD’s typically come with associated accuracy measures

nonparent EPD

an EPD for an animal without progeny data. nonparent EPD’s typically do not come with associated accuracy measures and may only be pedigree estimates

pedigree estimate

a genetic prediction based strictly on pedigree data

information supplied for predictions is to allow for….

predictions among animals within a breed

what should you keep in mind when calculating predictions?

there are certain environmental and mating schemes (purebred vs crossbred) that may have a significant effect on actual performance

what is the meaning of zero when interpreting genetic evaluation information?

base value

base (in large scale genetic evaluations)

the level of genetic merit associated with an EPD of zero

what does the definition of base depend on?

the statistical model used for genetic prediction and on various characteristics of the data

base year (in large scale genetic evaluation)

the year chosen to represent the base; the average EPD of all animals born in the base year is zero

EPD’s from animals born after the base year are adjusted according to…

base year values