Bob L. Larson, DVM, PhD

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Heifer Development (Cornerstone of herd
profitability)

• Bob L. Larson, DVM, PhD
• University of Missouri
• Commercial Agriculture - Beef Focus Team

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PERCENTAGE OF COWS PREDICTED TO CALVE IN EACH
20-d PERIOD
1st 20d
2nd 20d
3rd 20d
4th 20d
open
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Challenges
High Nutritional Requirements
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Challenges
High Nutritional Requirements
Immunologically Naive
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Challenges
High Nutritional Requirements
Immunologically Naive
Obstacles To Rebreeding
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Rewards
Superior Cowherd Genetics
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Rewards
Superior Cowherd Genetics
Short Calving Season
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Rewards
Superior Cowherd Genetics
Short Calving Season
Older Average Cow Age
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Rewards
Superior Cowherd Genetics
Short Calving Season
Older Average Cow Age
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Rewards
Superior Cowherd Genetics
Short Calving Season
Older Average Cow Age
Decreased Dystocia
Healthier Calves
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Nutritional Development
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Birth to Weaning
Milk
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(No Transcript)
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Nutrients Supplied by Suckling 20 peak milk
production day 65 of lactation (20)
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Nutrients Supplied by Suckling 20 peak milk
production day 95 of lactation (18.6)
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Nutrients Supplied by Suckling 20 peak milk
production day 155 of lactation (9.8)
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Nutrients Supplied by Suckling 20 peak milk
production day 215 of lactation (2.0)
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Nutrients Supplied by Suckling
To have majority of nutrients to support 2.2 lbs.
daily growth (first 90 d of lactation)
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Nutrients Supplied by Suckling
September 1 for March 1 calf - 76 of nutrients
supplied by grazing
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Nutrients Supplied by Suckling
If forage is scarce after September 1, calf
growth will suffer - should wean heifer and put
on better forage.
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Creep Feeding
Negative Impact
If supplying energy in excess of that needed for
skeletal growth (British cows, good milking cows,
excellent forage etc.) Decreases lifetime milk
production
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Creep Feeding
Positive Impact
If supplementing poor forage, poor milking dam,
or Continental breeds May be more profitable to
wean and place on high-quality forage
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Weaning to Breeding
Target Weight
60-65 of mature weight coincides with puberty
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Target Weight Calculation
Daily gain needed (lbs./day)
(Target Wt. - Present Wt.) number of days
lbs./day
Should monitor gain by weighing a sample of
heifers
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Weaning to Breeding
Overfeeding or underfeeding can have negative
effects Gain does not have to be constant
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Weaning to Breeding
Heifers should be near BCS 6 at the time of
breeding and should stay at that level through
calving
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Breeding to Mid-gestation
Target Weight
80-85 of mature weight at calving as 2-year-old
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Breeding to Mid-gestation
Protein
Overfeeding during breeding season can reduce
fertility (particularly if energy is low) Early
growth cool-season grasses
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Breeding to Mid-gestation
Energy
Good environmental situations - requirements
mostly met with forage Fall-calving heifers will
require supplementation
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Last 60 d of Pregnancy
Target Weight
80-85 of mature weight at calving as 2-year-old
BCS 6 is critical
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Last 60 d of Pregnancy
Deficiencies cause weak calf syndrome
Slow to stand, weak suckle reflex, poor heat
production, poor colostral absorption...
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Last 60 d of Pregnancy
BCS 6 is critical Demands of lactation make gains
after calf is born almost impossible
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First 80 d of Lactation
Greatest Nutrient Demand
Need excellent forage or supplementation
Require 80 d to resume cycling
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4 Strikes Against Rebreeding
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Gaining Weight After Calving
Once protein needs are met - cannot improve gain
on forage-based diets
High-cost, high-concentrate ration required
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KEY
Must calve in BCS 6
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Macrominerals
Sodium - salt is consistently required
Calcium - forage is usually adequate
Phosphorus - forage quality affects
supplementation needs
Magnesium - periods of deficiency
Potassium - situations of deficiency
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Cobalt - not much is known
Copper - Iron, sulfur, molybdenum
Iodine - deficiencies seldom reported
Manganese - situations of deficiency
Selenium - deficiency and toxicity occur
(activity tied to Vit E)
Zinc - most frequent deficiency
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Vitamins A and E -
Deficiencies cause repro. losses
Prolonged drought or storage will reduce
availability
Rapidly destroyed by oxygen, heat, light, and
trace minerals
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Vitamins A and E -
Vitamin A supplementation is inexpensive and no
toxicity problems are reported
27,000 IU/day to 39,000 IU/day
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Vitamins A and E -
Vitamin E toxicity has not been demonstrated in
cattle
Early evidence suggests that levels higher than
500 IU/day may be beneficial for reproduction
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Thiamin -
Polio - nervous system problems
Deficiency seen with high concentrate (feedlot)
diets
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Niacin -
Benefits (feed efficiency, ADG) seen when fed to
cattle on high concentrate rations
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Feed Additives
Recommended in weaning rations
Ionophores will control (not treat)
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Feed Additives
Increases the number of heifers that reach
puberty by the start of the breeding season
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Management Practices
Deworming
Growing cattle are most adversely affected by
internal parasites
Improved gain results in earlier puberty
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Management Practices
Implanting
Negative affects when given at birth, near
weaning, or when repeated
No long-term positive effects if given according
to label