EFFECTS OF AGE (Weight), FRAME SIZE AND SEX ON CATTLE FEEDING: Considerations for
stocker cattle and feedlot cattle
1. General Goals
* Carcass weight: 600 - 800 lb.
(Equivalent to 1,000 - 1325 lb. liveweight)
- There is a discount if carcasses weigh less than 600 lb.
(<550 lb. for heifers)
- Slaughter costs (per lb. carcass)
- Fit in the box (boxed beef)
* PREFERRED live weight
Steers: 1050-1250 lb.
Heifers: >900 lb.
* Backfat thickness: .30 to .45 inches
* Ribeye area: 12.5 to 14.0 sq. inches
* Yield Grade: 2 or less
* Quality Grade: Select + to Choice -
* Most feeders aim for 70-80% choice while keeping
YG4's to less than 5-10%.
2. Effect of age/weight on ADG and F/G
Weaned calves _vs_ Yearling feeders
(400-600 lb. @ (600-800 lb. @
7-8 mos. old) 14-16 mos. old)
CALVES tend to have (compared to yearlings)...
1) Better feed efficiency
* Growth of muscle, bone, vital organs vs fat deposits
* Slightly greater feed intake relative to body wt.
* Lower maintenance requirement
Therefore, greater portion of diet is for NEg
2) Slightly slower ADG
3) 45-60 more days in feedlot
4) Lighter slaughter wts. (100-200 lb. lighter) at the same degree
of fatness
* Feeders usually feed "grower rations" (higher roughage/
lower energy) until the calves weigh ~700-750 lb. This
allows more skeletal growth.
5) More sickness and greater death losses
6) Approx. same total grain consumption
7) Slightly lower quality grade for younger animals ???
Data are inconclusive. Some research data support this;
other data indicate very little effect of age on quality
grade.
3. FRAME SIZE & FEEDER CATTLE CONSIDERATIONS
a. Comparing large-framed cattle to smaller framed cattle....
* At any GIVEN WEIGHT, large-framed cattle gain faster.
* At a GIVEN WEIGHT, nutrient requirements of
growing/finishing cattle are greater for large-framed
cattle.
* When fed to a CONSTANT WEIGHT, large-framed cattle will
gain faster & have better F/G.
* When fed to a CONSTANT CARCASS COMPOSITION, (e.g., .4-.5"
BF which which would equate to ~25-28% fat in the carcass)
large-framed cattle usually...
- Are less efficient (F.E.)
- Will have only a slight advantage in ADG
- Probably won't have any advantage in days on feed (In
fact, they likely will take 2-3 weeks longer.)
b. When fed to SAME CARCASS COMPOSITION, stockered yearlings will
be 100-200 lb. heavier than calves placed in feedlot soon after
weaning.
c. Nutrient Requirements:
* NEm directly related to weight (The higher NEm requirement
contributes to the poorer F.E. of larger framed cattle.)
* NEg related to sex, frame size, mature size (calf, yrlg,
compensating), body fatness
* CP relationships similar to NEg
4. Importance of sex (Steers vs heifers) in feeding
a. Feeder heifers usually are $5 to $10/cwt less than steers.
At slaughter there usually is only a ~$2 to $3 spread
Some reasons for discounts in heifer feeder cattle...
* Slower ADG
* Poorer F/G
* Risk of heifers being pregnant
* Estrus, riding activity, prolapses
b. MGA
* suppresses estrus
* improves ADG 3-5% & F/G 4-8%
c. Pregnancy
* Well-managed vs. many smaller herds
More of a problem with smaller herds
* If they calve...
- severe dystocia (fat accumulation)
- posterior paralysis common
- prolapse
- retained placenta / antibiotics / withdrawal time
* Pregnancy check; can abort with PGF2 alpha (Lutalyse) if
<150 days into pregnancy
With a good price spread, heifers can be profitable.....Do your
homework! In general, a spread of $8/cwt is about the
breakeven point between feeding steers and heifers. (This is
GENERAL...still do you homework.)