Selection of beef cattle Flashcards
what is the most important thing in commercial beef cattle operations
reproduction or the creation of new wealth
what does beef cattle having low management emphasize
genetic potential
what are some reproductive traits for females
-conception rate (0-.1)
-calving interval (0-.1)
-fetal survival to weaning (depends of mothering ability and milk quality)
-calving ease (pelvic measurements
-twinning
what are some correlations with reproduction
-back fat was negatively correlated to super ovulation response
-r=-.66, P=.001(signif)
what are some reproductive traits for males
-sperm count
-sperm morphology
-scrotal cirumfrence
what does scrotal circumference positively correlate with
-sperm count
-age of puberty
-fertility in daughters
h2=.4-.6
>=32cm
growth traits
-birth weight (.3-.4)
-wean weight (.3-.35)
-postwean gain (.5-.55)
genetic correlations of growth
-weaning wt:postwean gain .46
-weaning wt:carcass grade .52
what are some factors for adjusted weights
-age
-sex
-age of dam
-twins
adjusted weights: age
-weaning wt. adjusted to 205 days
-(150-250 day target)
adjusted weight: sex
heifer calf(1.1)=steer calf(1.05)=bull calf(1.0)
adjusted weight: dams age
2-+15%
3-+10%
4-+5%
5-10-0%
greater then 11-+5
adjusted weight: twins
twin is 75% of singleton
feedlot gain
-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
carcass quality heritability
-slaughter grade .4-.45
-rib eye area .55-.6
-tenderness .5-.6
-marbling .4-.45
when does tenderness of a carcass matter
farm gate
camera grading system for rib eye
-check the 12-13 rib
-in the thinnest area
-take several measurements
-also look at yellow im fat
what is marbling highly correlated with
-to palatability (juiceness, flavour)
-grade fat (which is an average of 3 back fat measurements)
what are some meat quality tests
-marbling test
-tenderness test
why is longevity an important trait in beef cows
-heifers have more problems calving but “olds” abort more
-overall production costs are lower if cows kept longer
why is there so many breeds and species of beef cows
they have a wide variety of different environments
-heat tolerence
-pasture conditions
-parasite resistance
mating systems of beef cattle
-inbreeding (reducing fertility, calf survival)
-crossbreeding (norm of commercial, using complementation and heterosis, increased fertility and weight)
purebred cattle
-main product:
-bulls
-semen
-some embryos
selection systems
-individual selection:
typical in commercial industry for cows and bulls (use of EPDs increasing)
-independent culling:
most common: growth and fertility
