2nd livestock test

Question 1

Phenotype =

Answer 1

genotype + environment

Question 2

Genetic improvement is…

Answer 2

Cumulative between generations and is permanent. The environment is neither permanent nor cumulative

Question 3

What is selection?

Answer 3

The first step – select the best breed (eg Jersey for dairy, Angus for beef). The second step – select the best parents (based on some estimate of genetic merit (not phenotype)).

Question 4

What is heritability (complex traits)?

Answer 4

For genetic improvement to occur the trait(s) be similar to relatives. Heritability is the proportion of variation in a trait that is controlled by genes and it ranges from 0 to 1.
Heritability of 0.5 is high allowing rapid genetic change. Heritability of 0.1 is low allowing slow genetic change

Question 5

What is a breeding value (BV or EBV)?

Answer 5

A statistical measure of all the genes affecting a trait. The average BV for a population is 0, BVs can be positive or negative. The BV for an animal without other information is ½ BV from mother + ½ BV from father. Calf BVs can be better or worse than parents.

Question 6

What is a selection index?

Answer 6

The sum of breeding values for different traits weighted by their importance. Has different names (eg. Breeding Worth (BW) in dairy, NZ Standard Maternal Worth in sheep).

Question 7

How do farmers select rams to genetically improve lamb

carcass weight?

Answer 7

Step 1 – decide on what animal traits are important (will depend on whether progeny are retained for breeding, if ‘yes’ maternal traits are important). Step 2 – choose breed(s). Step 3 – choose rams.

Question 8

Maternal traits and breeds

Answer 8

Number of lambs, ewe size, GHG, wool, disease/parasite resistance. Breeds - new composites eg TEFRom, Coopworth, Perendale, Romney.

Question 9

Terminal traits and breeds

Answer 9

Growth traits, carcass weight, meat traits. Breeds - Suffolk, Texel, Poll Dorset, new composites eg SufTex, FocusPrime.

Question 10

Choosing rams for carcass weight (CW,

Terminal breeds)

Answer 10

Ram breeders select on BVs to improve CW. NZGE is the national sheep recording and genetic evaluation service owned by Beef + Lamb NZ. Submit animal data to NZGE and get BVs returned. Commercial farmers will buy rams to meet their farming objectives and budget, some will consider BVs

Question 11

TSG sire report is comprised of…

Answer 11

Page 1 – background info (note base year = 1995). Pages 2 to 4 – list of flocks in analysis. Pages 6 to 11 – list of 200 rams ranked in order of TSG

Question 12

Flock and herd age structure

Answer 12

Due to culling and deaths, a flock/herd has more young
stock than old stock (eg. a flock of 1000 ewes with age groups of 2yo, 3yo, 4yo, and 5yo, cannot have 250 ewes in each group because: some ewes will die each year, the farmer will cull some ewes each year)

Question 13

How do farmers select semen to genetically improve cow milk protein?

Answer 13

Step 1 – decide on what animal traits are important (milk production, disease traits, conformation traits, feed efficiency). Step 2 – choose breed(s). Step 3 – choose AI or natural mating (tail-up & heifers). Step 4 – choose AI company. Step 5 – choose “bull of day” (most common) or specific bulls

Question 14

Breeds for milk protein

Answer 14

Primarily Holstein-Friesian, Jersey, and their cross
(KiwicrossTM). However, Jersey is smaller and Holstein-Friesian produces larger milk volume. Other breeds are now of minor importance (eg Ayrshire, Milking Shorthorn, Guernsey, Brown Swiss)

Question 15

Dairy National Breeding Objective (NBO)

Answer 15

8 traits: milk volume, milk protein, milk fat, fertility,
liveweight, somatic cell score, body condition score and
residual survival. BVs weighted to produce Breeding Worth (BW). If too many to discuss, consider milk protein. Data is collected into a national database and used to produce BVs and published for all farmers.

Question 16

Advantages of a fleece on sheep

Answer 16

Keeps the sheep warm and alive in very cold, wet and windy conditions, can help keep the sheep cool in very hot, sunny, dry conditions, protects the skin against sun damage, reduces food requirements in cool conditions, makes sheep easier to catch

Question 17

Potential disadvantages of a fleece on sheep

Answer 17

can make lambing ewes insensitive to cold conditions that will kill lambs, limit the ability of sheep to lose heat in hot, moist conditions, limit the appetite of the sheep when there is surplus feed, reduce body and wool growth, limits access to the teat for lambs, increases risk of casting, limit the vision of sheep, accumulate dung and mud, catch in vegetation, makes elimination of external parasites more difficult, increases the risk of fly strike - increases insecticide required

Question 18

Why remove wool?

Answer 18

Most breeds have been bred not to shed, income through the sale of wool, animal health (fly, lice), avoid negative effects of heat stress, improve wool quality, shearing pregnant ewes can improve lamb survival, less casting of pregnant ewes, better access to teats for lambs

Question 19

Preparing sheep for shearing

Answer 19

They should be dagged at least two weeks pre-shearing (allows any shed stain to wash or fade out), grazing paddock selection (potential contamination needs to be considered), avoid wet/muddy areas and areas with contamination of seed head, ewes should be off feed at least 12 hours before, care needed with heavily pregnant ewes, dark fibred sheep should be drafted off and not penned with white sheep and shorn last, ewes drafted into lines if there are large disparities in staple length, shed should be clean and free from contaminants, there should be enough ‘bins’ to allow for wools of different types

Question 20

Shearing comb types

Answer 20

Blade (stubble length variable (generally greater than 9mm)), standard comb (3 – 5mm), cover comb (7 - 9mm)

Question 21

Shearing & Animal welfare

Answer 21

Post shearing sheep are susceptible to a cold environment, but with a combination of cool temps with wind and rain can cause death. To limit deaths: shelter from wind, good feeding levels post-shearing, short time off feed, do not shear if weather is poor, stop shearing earlier in the day, use cover-comb or blades

Question 22

Advantages of frequent shearing

Answer 22

Fewer cast sheep, fewer problems with flystrike, better wool color, less wool in the oddment categories, less crutching and dagging, more even cash flow

Question 23

Disadvantages of frequent shearing

Answer 23

If outside optimal length can reduce wool prices, extra shearing costs, extra risk of deaths from cold stress, increased chance that shearing may conflict with other procedures such as breeding or lambing