Selection of beef cattle

Question 1

what is the most important thing in commercial beef cattle operations

Answer 1

reproduction or the creation of new wealth

Question 2

what does beef cattle having low management emphasize

Answer 2

genetic potential

Question 3

what are some reproductive traits for females

Answer 3

-conception rate (0-.1)
-calving interval (0-.1)
-fetal survival to weaning (depends of mothering ability and milk quality)
-calving ease (pelvic measurements
-twinning

Question 4

what are some correlations with reproduction

Answer 4

-back fat was negatively correlated to super ovulation response
-r=-.66, P=.001(signif)

Question 5

what are some reproductive traits for males

Answer 5

-sperm count
-sperm morphology
-scrotal cirumfrence

Question 6

what does scrotal circumference positively correlate with

Answer 6

-sperm count
-age of puberty
-fertility in daughters
h2=.4-.6
>=32cm

Question 7

growth traits

Answer 7

-birth weight (.3-.4)
-wean weight (.3-.35)
-postwean gain (.5-.55)

Question 8

genetic correlations of growth

Answer 8

-weaning wt:postwean gain .46
-weaning wt:carcass grade .52

Question 9

what are some factors for adjusted weights

Answer 9

-age
-sex
-age of dam
-twins

Question 10

adjusted weights: age

Answer 10

-weaning wt. adjusted to 205 days
-(150-250 day target)

Question 11

adjusted weight: sex

Answer 11

heifer calf(1.1)=steer calf(1.05)=bull calf(1.0)

Question 12

adjusted weight: dams age

Answer 12

2-+15%
3-+10%
4-+5%
5-10-0%
greater then 11-+5

Question 13

adjusted weight: twins

Answer 13

twin is 75% of singleton

Question 14

feedlot gain

Answer 14

-h2=.50-.55
-feed/gain efficiency:
-6:1 6lbs to get 1lb
-6 is good in lot
-6.5 more typical
-feed conversion: 1lb gained while fed 5lbs 1/5 or .2

Question 15

carcass quality heritability

Answer 15

-slaughter grade .4-.45
-rib eye area .55-.6
-tenderness .5-.6
-marbling .4-.45

Question 16

when does tenderness of a carcass matter

Answer 16

farm gate

Question 17

camera grading system for rib eye

Answer 17

-check the 12-13 rib
-in the thinnest area
-take several measurements
-also look at yellow im fat

Question 18

what is marbling highly correlated with

Answer 18

-to palatability (juiceness, flavour)
-grade fat (which is an average of 3 back fat measurements)

Question 19

what are some meat quality tests

Answer 19

-marbling test
-tenderness test

Question 20

why is longevity an important trait in beef cows

Answer 20

-heifers have more problems calving but “olds” abort more
-overall production costs are lower if cows kept longer

Question 21

why is there so many breeds and species of beef cows

Answer 21

they have a wide variety of different environments
-heat tolerence
-pasture conditions
-parasite resistance

Question 22

mating systems of beef cattle

Answer 22

-inbreeding (reducing fertility, calf survival)
-crossbreeding (norm of commercial, using complementation and heterosis, increased fertility and weight)

Question 23

purebred cattle

Answer 23

-main product:
-bulls
-semen
-some embryos

Question 24

selection systems

Answer 24

-individual selection:
typical in commercial industry for cows and bulls (use of EPDs increasing)
-independent culling:
most common: growth and fertility