ANSC 313 Lecture Notes - Lecture 8: Weaning, Semen Analysis, Birth Weight
LECTURE 19!
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Beef Cattle!
selection objectives!
beef cattle have low level of management= should emphasize genetic potential!•
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selection criteria!
reproduction- female!•
conception rate 0-0.1!◦
calving intervals 0-0.1!◦
fetal survival ( embryonic loss)!◦
has not been much improvement !‣
survival to weaning!◦
mothering ability!‣
milk quality- not studied much in beef cattle!‣
calving ease!◦
pelvic measurements ?!‣
twinning?!◦
almost everywhere is against twinning!‣
!
backfat was negatively correlated to super ovulation response!
suggest that the animals that would be good for beef may not be good for reproduction!•
!
ovulation!
number of embryos per flush was repeatable in 3 consecutive flushes!•
correlation between size of flush of dam and her response to super ovulation was NOT •
significant!
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selection criteria !
reproduction- males!•
sperm count!◦
sperm morphology!◦
scrotal circumference 0.4-0.6!◦
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growth!
birth weight 0.3-0.4!•
weaning weight 0.3-0.35!•
post weaning gain 0.5-0.55!•
genetic correlations!
weaning wt. : postman gain 0.46!•
weaning weight : carcass grade 0.53!•
NOTE: larger calves = more calving problems!
!
"adjusted" weights!
age!•
weaning wt. adjusted to 205 days!◦
ty to weight between 160-250 days!◦
sex!•
heir calf : steer calf : bull calf!◦
