Dairy Heifer Rearing and Optimal Replacement

Sourcing Dairy Herd Replacements

  • Home-reared: Benefits include known breeding and disease status; risks involve requirements for additional labor, buildings, and land.

  • Contract reared: Negates the need for farm-owned labor/land but introduces risks regarding the rearer and biosecurity.

  • Flying herd: Buying in replacements allows all cows to be bred to beef bulls for calf sales; risks include market volatility and biosecurity.

Heifer Growth Target Milestones

  • Average Target Growth Rate: 0.7−0.8 kg/d0.7-0.8\,\text{kg/d} for a Holstein-Friesian with a mature body weight of ~700 kg700\,\text{kg}.

  • Birth: ~40 kg40\,\text{kg}.

  • Weaning (6−8 wks6-8\,\text{wks}): 2×2 \times birth weight (~80 kg80\,\text{kg}).

  • Puberty (9−12 mths9-12\,\text{mths}): 40%40\% mature BW (~280 kg280\,\text{kg}).

  • Conception (13−15 mths13-15\,\text{mths}): 55−60%55-60\% mature BW (~400 kg400\,\text{kg}).

  • First Calf (24 mths24\,\text{mths}): 85−90%85-90\% mature BW (~615 kg615\,\text{kg}).

  • Mortality: Total heifer losses average 14.7%14.7\% to first breeding and 22.4%22.4\% to first calving.

Neonatal Care and Colostrum (The 3 Qs)

  • Quantity: 10%10\% of BW within 2 hrs2\,\text{hrs} of birth (3−4 litres3-4\,\text{litres} for H-F calves), repeated within 12 hrs12\,\text{hrs}.

  • Quality: Must be >50\,\text{g/L} of IgG. Use a Colostrometer (green zone) or Brix refractometer (>22\%). Avoid bacterial contamination.

  • Quickly: First feed given ASAP for optimal passive immunity.

  • Impact of IgG: Low blood IgG (0−10 ZST0-10\,\text{ZST} units) results in 9.8%9.8\% mortality compared to 3.2%3.2\% for good uptake (20+ ZST20+\text{ ZST} units).

  • Milk Yield: Feeding 4 litres4\,\text{litres} vs. 2 litres2\,\text{litres} of colostrum increases first lactation yield by 955 kg955\,\text{kg} (Faber et al., 2005).

Housing and Legal Requirements

  • Legislation: Based on Animal Welfare Act 2006, FAWC’s Five Freedoms, and Welfare of Farmed Animals (England) Regulations 2007.

  • Space Standards: Individual pens are prohibited after 8 weeks8\,\text{weeks}. Minimum space for weight <150\,\text{kg} is >1.5\,\text{m}^2; >200\,\text{kg} requires >3.0\,\text{m}^2.

  • Environment: Calves need protection from adverse weather, predators, and biting insects. Calf jackets are used if temperatures are below +10∘C+10^{\circ}\text{C}.

Nutrition and Rumen Development

  • Feeding Requirement: Calves <28\,\text{d} must be fed at least two liquid milk feeds per day.

  • Rumen Stimulus: Offering starter concentrate and water stimulates development; rumen can function from 5 days5\,\text{days} of age.

  • Water Access: Ad libitum water increases starter feed intake (1.46 kg/d1.46\,\text{kg/d} vs. 0.3 kg/d0.3\,\text{kg/d} when restricted).

  • Weaning Decision: Base on concentrate intake (1 kg/d1\,\text{kg/d} if CP > 22\%; 2 kg/d2\,\text{kg/d} if CP < 22\%) rather than age or weight.

Age at First Calving (AFC) and Economics

  • Efficiency Target: optimum AFC is 22−24 months22-24\,\text{months}.

  • Cost of Delay: Rearing cost is 2.31/\text{day}. Total cost at 24 months24\,\text{months} (1,307) vs. 36 months36\,\text{months} (1,638).

  • Breakeven: Profitability typically begins during the 2nd lactation; net loss persists through birth and the 1st lactation.

  • Longevity: 86%86\% of heifers calving at 22−23 months22-23\,\text{months} are alive at 5 years5\,\text{years}, compared to only 33%33\% of those calving at 32−36 months32-36\,\text{months}.