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Managing Replacement Heifers

Managing Replacement Heifers. Management. Intensity varies throughout the lifetime of the dairy cow, depending on the needs of the animal Growing heifer needs relatively little attention from weaning to calving But this doesn’t mean management of these animals is less important

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Managing Replacement Heifers

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  1. Managing Replacement Heifers

  2. Management • Intensity varies throughout the lifetime of the dairy cow, depending on the needs of the animal • Growing heifer needs relatively little attention from weaning to calving • But this doesn’t mean management of these animals is less important • Inattention or neglect during this period can have permanent effects on productivity of the animal

  3. Economic Aspects • Averages $1,200 to raise heifer to 24 months • Costs increase ~$50/month for every additional month • Also increases heifer inventory by ~10% for each month • Culling rate also affects heifer inventory required to maintain static herd size • Mortality rate also affects inventory • Costs range from ~$900 to ~$1600/heifer • Lowering costs by $200/heifer can increase profit by $50,000/yr on a 1,000-cow dairy

  4. Total Numbers of Replacement Needed to Maintain Static Herd Size (100-cow herd) Age at First Calving (months)

  5. Challenges and Goals • Average cow milks less than 4 years • Must replace 25% of herd to maintain herd size • Average cull rate over 33% • In addition, ~20% of heifers die before maturity • Makes voluntary culling very difficult • Goal for heifers is to calve before 24 months of age • 1250 pounds • 54 inches

  6. Heifer Growth • Goal: replacement heifer to enter the milking herd as rapidly as possible without compromising health or lactational performance • Well grown heifers can be bred at 13-15 months of age • Heifers calving at younger ages are more productive and return more income than heifers that calve at an older age

  7. Heifer Growth • To achieve early calving goals, heifer growth rates need to be monitored and assessed on a regular basis • Measuring height with altitude stick • Measure weight with scales or measuring tape • Growth rates of 1.75-2 pounds per day are necessary to reach calving weight by 22-24 months of age • Smaller breeds average ~1.4 lbs/day

  8. Heifer Growth • First estrus in heifers depends on size and weight • First estrus shown at ~35% of body weight • Heifers in better condition have stronger signs of estrus and better conception rates • However, overconditioned heifers require more services per conception • Heifers should be bred at 60% of their mature weight • Type of gain is important, fat vs muscle • Calve at 85% of mature weight

  9. Type of Gain • Body condition scores indicate relative fat content • Can be used to indicate “quality” of gain • Score 2.5 at 6 months of age • Score 3.0 at breeding • Score 3.5 at calving • Type of gain determined by protein to fat ratio in ration • Overfeeding energy increases fat content and BCS

  10. Body Condition Scores

  11. Monitoring Growth • Both height and weight important • Height measurements Altitude stick Estimate at feed bunk or on your body • Weight measurements • Scales • Weight tape at withers • Estimate • Use BCS to replace weight??? • Simple and quick (height and BCS combined)

  12. Fig 46-1. Heifer weight can be accurately estimated by measuring heart girth using a weight tape (Courtesy of Iowa State University)

  13. Fig 46-4. By twelve months of age, heifer should be at a body condition score of about 2.75 to 3.0 (Courtesy of Iowa State University)

  14. Fig 46-5. Bred heifers should be targeted towards a body condition score of about 3.5 at calving (Courtesy of Iowa State University)

  15. Breeding Heifers • Heifers should be bred at BCS of 3.0 • Early breeding of heifers yields more profit • Shortens time from birth to lactation • Lowers costs • Lifetime production is greater • Permits faster genetic progress in the herd • Helps maintain established seasonal calving schedule

  16. Mammary Development • Most rapid increase in numbers of secretory cells occurs from 3 months to 2nd estrous cycle • 3 times the rate of somatic growth • High energy intake pre-pubertally may be detrimental • Earlier onset of puberty Less time for secretory tissue development Decreases milk production by up to 15% • Decreased growth hormone secretion • May be alleviated by restoring proper protein:energy ratio • Post-pubertal rates of gain are unrelated to secretory development

  17. Fig 46-3. The type of gain achieved by prepubertal heifers is more important than the rate of gain (Courtesy of Iowa State University)

  18. Rumen Development • Rumen in prepubertal heifer undergoes changes during this period • Rumen capacity is limited at weaning • By two months of age the rumen comprises 50% of the stomach mass • By six months the rumen comprises 60% of stomach and is fully functional • Limited rumen capacity during this period limits ability of these animals to consume enough forage to meet nutritional requirements • High-moisture feeds (haylage, silage) or pastures are difficult to incorporate into rations for heifers under 6 months of age because of intake issues

  19. Fig 46-6. By nine months of age, rumen capacity is adequate such that nutritional needs are nearly met by ingestion of high quality forage alone (Courtesy of Iowa State University)

  20. Nutrition of the Prepubertal Heifer • Forage quality is critical • Heifer has limited capacity for dry-matter intake • Lowly digestible forages decrease rate of passage, increase rumen fill, impair growth rates • Recommended energy intakes for prepubertal heifers is 0.72 Mcal per pound of dry matter for growth rate of ~1.7 lbs/day • Protein-to-energy ratios should be maintained at 6:1 if growth rate is ~1.7 lbs/day • Higher growth rates require higher ratio • Lower growth rates (weather, disease) require less protein

  21. Nutrient Requirements • Vary with age and growth rate • Affected by environmental conditions Restrictions to access to feed and water Parasite loads increase energy requirements up to 10% Ambient temperature lower critical temperature ~10 degrees F if dry Wind Mud covering or wet hair coats increases LCT to about 40 degrees F

  22. Fig 46-7. High quality forage provides the foundation for a good heifer ration (Courtesy of Iowa State University)

  23. Compensatory Growth • Ability to have above normal growth rates following period of energy restriction • Restricted animals develop increased energetic efficiency • Improved efficiency of nitrogen utilization/recycling • Efficiencies maintained following return to full feed • improved mammary development • increased lactational efficiency • Start “program” after 5 months of age with alternating periods of full feed and restricted feed • Difficult to implement practically unless heifers tightly grouped

  24. Vaccinations • Timing of initial vaccinations should be varied depending on passive immunity status of calves and health status of herd • Early initiation of vaccination program leads to lower levels of protection for vaccinated animals • Selection of vaccines based on • Incidence of disease • Potential cost of disease • Cost of vaccine • Effectiveness of vaccine

  25. Vaccinations • Effectiveness of vaccines compromised by several factors • Improper storage or administration • Use of disinfectants to clean syringes • Antagonistic reactions when mixing more than one vaccine • Administering antibiotics or other drugs at the same time as the vaccine can diminish the immune response • Vaccinating sick animals results in an inadequate immune response

  26. Parasite Control • Heifers with heavy parasite loads decreases feed efficiency and may develop diarrhea and anemia • Parasitic loads can increase energy requirements by up to 10% • Adjust ration and management strategies to match actual farm conditions • Coccidiosis is common internal parasite • Oocytes are ingested and penetrate gut of heifer • Results in impaired feed efficiency and diarrhea • Ionophores prevent and control coccidiosis • Bedded manure packs should be cleaned often and thoroughly

  27. Fig 46-8. Coccidiosis is a common protozoal parasite affecting young heifers. Infected heifers appear listless and unthrifty (Courtesy of USDA)

  28. Housing Considerations • Many different types of housing, but certain criteria must be met • Excellent ventilation • Adequate space • Ready access to feed and water • Housing should allow heifers to be grouped in small groups to minimize stress and competition at feed bunk • Age spreads shouldn’t exceed 1 month • Weight spreads shouldn’t exceed 100 pounds

  29. Fig 46-9. Postweaned calves should be housed in small groups of 4 or 6 calves per pen to minimize socialization difficulties (Courtesy of Iowa State University)

  30. Fig 46-10. Heifers should be housed in groups that closely limit age and weight differences (Courtesy of Mark Kirkpatrick)

  31. Summary • Management of replacement heifers has significant impact on their performance as cows • For example, overfeeding prepubertal heifers decreases potential for milk production • Management of replacement heifers has significant impact on dairy farm profitability • Rearing costs vary dramatically between farms • Effects on cow performance • Often MORE opportunity for improvement in profitability through heifers than cows

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