Biological Cycle of the Beef Cow

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Biological Cycle of the Beef Cow

• The biological cycle of the cow has implication
  on reproduction, nutrition, and genetics
• Therefore the biological cycle has everything to
  do with the economic forces of beef production
• To optimize production efficiency we must
  understand the requirements of the cow throughout
  the cycle
• nutritional requirements of the beef cow
  fluctuate from very low (lower than any other
  livestock) to moderately high

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Gestation length is approximately 282 days

• 1st trimester 94 days
• 2nd trimester 94 days
• 3rd trimester 94 days
• 365 days/yr - 282
• 83 days to get her rebred

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Biological Cycle of the Beef Cow
Born Day (-430)
Bred, June 1 Day 1
120 d bred lactation High mid
83 d Early lactation Very high!
Post-partum Interval 83 days
1st Trimester 94 days
3rd Trimester 94 days
2nd Trimester 94 days
100 d Mid gest Very low
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Annual energy requirement and hay intake 1200
lb cow, 20 lb milk at peak
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Annual protein requirement and hay intake 1200
lb cow, 20 lb milk at peak
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Goal of Managing the Biological Cycle of the Beef
Cow

• Plan the calving season so that the time of
  greatest animal need will coincide with time of
  greatest nutrient supply.
• Two factors
• Range readiness
• Biological cycle of the beef cow

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The economic return of a grazing program depends
on forage quantity, quality, and harvest
efficiency Goal is match the seasonality of
grasses with the season of livestock use
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Seasonal quality and quantity of grazable forage
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MSU Cow Nutrition Symposium
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WHY CHANGE?
Matching the forage resources
Altered marketing strategies
Competing enterprises
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Mixed grass prairie dominated by cool-season
grasses
150-d mid-April to mid-September growing season,
338 mm average
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40.0
37.2
35.6
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273
229
181
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224
222
203
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Approximate Feed Inputskg/cow/year
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Conclusions

• Time of calving and age at weaning affected
  weaning weights of calves
• Must consider all goals in choosing calving and
  weaning times
• Feed costs must be weighed against calf prices
  and herd size to determine optimum calving time

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Matching forage and cows requirement, Deseret
Land and Livestock, From 1995 Intermountain Cow
Symposium

• Reduce dependency on harvested forages - lower
  annual feed cost
• Harvest hay on only productive land ? lowered
  /ton of hay
• Decreased annual labor cost of feeding cows

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Hay production changes at the ranch
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Selected costs per cow per year
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Conclusion

• Postponing the calving season to approximately
• 40 days before maximum forage growth
• can be beneficial.
• Reduced cost in feeding
• Better utilization of range forage
• Increase in reproductive performance
• Cleaner environment
• Better weather condition
• Higher price for weaned calves
• Why do many ranchers calve in February?