Practical decision making

why do we want to manage domestic animal breeding?

• select desired traist

• select against negative traits

what does management of breeding require

• assessment and measurement of traits that’ve been inherited

what are 5 examples of assessing for selective breeding, how do we describe these traits?

1. milk production

2. growth rate

3. fleece quality

4. elbow/hip dysplasia

5. thoroughbred galloping speed

these are measurable traits

what is heritability (h²)

• proportion of phenotypic superiority of parents seen in offspring

if h²=0, what does this mean?

• none of the superiority of parents is passed onto offspring

if h²=1, what does this mean?

• all superiority of parents is passed onto offspring

what are the most important (economically) traits of dairy cow breeding?

• quantitative and those observed in females

what opportunity do bulls provide as we only need 1 bull for many cows?

• selection opportunity

why has a large increase in genetic potential been possible? (3)

1. accurate recording of milk yields

2. development of AI industry

3. development of techniques to estimate breeding value of cattle

what does PTA mean?

• predicted transmitting ability

what is PTA

• the amount of a particular trait an animal is predicted to pass onto offspring - average expected improvement of daughter

what is EBV and for what animals is it used for?

• estimated breeding value

  • meat production

what are 4 production traits we select for

• milk

• fat

• protein

• persistency

what are some health, welfare and fitness traits we select for?

• SCC

• mastitis

• fertility index

• lifespan

• locomotion

• calf survival

• lameness advantage

• TB advantage

what are 5 management traits we select for?

• temperament

• ease of milking

• calving ease

• maintenance

• carcass index

why do we look at production for trait selection?

• we can estimate how much more milk a daughter will produce compared to herd average

what can type traits be sueful for?

• determining cow suitability for sustained production for example

what does direct CE tell us?

• it predics the ease at which a calfe born by that sire will be born

what does maternal CE predict?

• ease with which the daughter will give bith

what does the mastits index tell us

• selection for mastitis improvement - negative values are desirable

what does dtr fertility tell us

• for every +1 point = improvement in calving interval by 0.6 days

what does lameness tell you

• every point predices one percent change of daughters becoming lame per lactation

what does maintenance tell us?

• indicates cost of maintaining smaller vs larger cows

what does tb advantage tell us?

• for every +1 point = 1% fewer daughters expected to become infected

what are the 2 management goals that need to be balanced when selectively breeding?

• health and welfare

  • profit

why do we want more reliable PTAs?

• more accurate predictions

what is a genetic index?

• combination of a number of individual traits into an index

what are 2 indexes used in the UK?

• PLI - profitable lifetime index

  • fi = fertility index

what does PLI tell us?

• the amount of money expected to gain from a daughter ofter her lifetime compared to the herd average

what do we sue to compare gneetics between animals?

• SNPs - genetic markers in DNA

what does using SNP/genetic markers help with in bulls?

• greater reliablity/confidence in them

how do we semen sex?

• use DNA weight - X chromosomes have more DNA than Y chromosomes

  • label DNA with fluorescent dye and organise by flow cytometry

why semen sex?

• allows farmer more control over offspring they produce → more females, more replacement heifers, fewer males = lowered dystocia risk

what are 2 disadvantages of semen sexing

• lowered fertility

• higher cost

when don’t we recommend semen sexing/

• using it in herds with poor fertility

what drives breeding priorities?

• profitability

what sires do we want to avoid using?

• low PLI - want top 50%