L5

• In NZ only 30 -80 % beef heifers bred at 15 months (note it actually is 14 – 16 months), compared to ~100% dairy

  
• Huge potential to increase productivity and efficiency in industry by increasing uptake of heifer mating. Estimate there is a 15% increase in profitability. Estimate there is a 15% increase in profitability.
• Dystocia is one of the key factor deterring beef farmers from calving 2-year-old heifers
• Reasons farmers do not breed heifers at 15 months


  • calving problems (dystocia)
  • low in-calf rates
  • re-breeding problems at 27 months
  • stunting of heifers growth and mature size
  • an extra mob to look after
  • more small calves
  • extra feed over winter required to grow heifers
  • more management skills required

  
• Benefits of calving heifers as 2 year olds

  • The unproductive life of each female in the herd is reduced
  • Lifetime output of cows is increased

  
• United Kingdom study states reducing age at first calving from three to two years of age is a method to reduce GHG (methane) production by 6.9%. Another study in USA indicated a reduction of 14%
• Limitations to the adoption of 2 year old calving


  • Stage of farm development
  • Loss of a mob of dry stock - can not be used as a 'buffer mob'
  • Need to carefully select bull to use over heifers
  • Calves are usually 10-15 kg lighter than those from 3 year olds (wean early)
  • Lower % of heifers pregnant as 3 year olds

  
• Critical Minimum Weight


  Joining Weight at which 85% or more heifers get pregnant (diagnosed 6-8 weeks after bull removal) in a 42 day joining period

  
• Cant get much more than 85-90% in calf over 42 days because of conception rates of 60-75%
• Usually 60% of mature live weight
• Relationship between liveweight and Conception rate

  • Liveweight increases, % in calf over 45 day mating period increases
• Target minimum liveweights for breeding heifers at 15 months

  • Weaning: 200-220 kg
  • 1st winter: 220-260 kg
  • 1st mating: 300-330 kg
  • 2nd winter: 440-470 kg
  • Calving: 460-490 kg
  • 2nd mating: 460-490 kg

  
• Feeding Programme for Heifers

  • Post weaning to the end of winter: moderate LWG (0.2 kg/day), feed 6-7 cm pasture around 1500-1800 kg DM/ha
  • End winter to mating: High LWG (0.7-1.0 kg/day), feed 10-12 cm pasture or 2000-2500kg DM/ha
  • Keep LWG high over the joining period and into the summer and autumn

  
• Unmated vs mated heifer feed requirements: Extra 850 Kg feed requirement

  
• Factors associated with onset of Puberty

  • Liveweight, liveweight gain, ratio of fat to lean
  • Season
  • Genetic factors early or late maturing breeds
  • Stress
• Breed of sire


  Age at puberty, Live weight at puberty
• Angus were heaviest at puberty
• Angus x Jersey were lighter than Angus x Friesian and Angus x KiwiCross at puberty
• Mean age at puberty similar for all breeds, just under 13 months
• Lactating heifers require 60% more feed than a dry heifer
• To achieve high performance focus on


  • Condition score and feeding levels
  • Time of mating/calving
  • Heifer health
  • Bull fertility and performance
• Calve at the right time ensures heifers consume surplus feed, are able to grow calves at 1.0 kg/day, are on a rising plane of nutrition to meet condition score for mating (cs of 7), and are not competing for feed with other high priority stock

  
• To successfully mate heifers at 15 months

  • Set a growth pathway from weaning to a minimum joining liveweight at 14 month
  • Use a small breed type and select a bull with an EBV for birthweight below the breed average and look at calving ease EBVs
  • Join for 42 days at the same time as cows
  • Overmate (join more heifers than needed as replacements) then cull after pregnancy testing
  • Could cull late 2nd cycles heifers and ensure 75% calve in first 21 days of calving
  • Feed as a growing animal until last 2 months of pregnancy (450+ kg) then on maintenance feed
  • Ensure heifers calve in 'fit' condition

  
• "The management package"


  • Adopt a suitable minimum joining weight
  • Considered bull selection
  • Linking joining date to mature cows
  • Use of a short joining period
  • Appropriate nutrition levels from 6 –30 months of age
  • Attention to physical fitness of heifers
  • Having realistic expectations

  
• Aim for: 85 % pregnant after 42 day joining period, 60 - 75% calve in first 21 days, 95 % calf survival, 95% pregnant as rising 3 year olds. but note there are additional feed costs and if yearling heifer in-calf rates are less than 70 % then there may be no benefits
• Heifer breeding and shortening the calving period

  • All heifers that enter the herd should calve over no more that 42 days
  • This ensures the main herd will have a calving duration of 49 -63 days
  • Use restricted heifer joining periods as method of tightening the calving duration in main herd
  • Calving pattern (number in first 21 days is crucial to this)