Lec 27

• Crossbreeding


  Mating of individuals of different breeds
• Terminal crossbreeding


  Mating of individuals of specific breeds of sire which are mated to specific breeds of dam and no replacements are produced
• Rotational crossbreeding


  Mating of individuals of two or more sire breeds in a cycle where replacement females are kept from a generation
• Crossbreeding systems

  • Terminal Crossbreeding
  • Rotational Crossbreeding
• Terminal Crossbreeding


  Specific breed(s) of sire mated to specific breed(s) of dam
• Rotational Crossbreeding

  1. Sire breeds used in a cycle

  2. Replacement females kept from each generation
• Two-breed Rotational Crossbreeding System


  Uses sires of 2 different breeds in alternate generations and crossbred females are retained for maternal stock
• Three-breed Rotational Crossbreeding System


  Uses sires of 3 different breeds in a cycle and crossbred females are retained for maternal stock
• % Retained Heterosis in Rotational Crossbreeding = (2^n - 2) / (2^n - 1) x 100, where n is the number of breeds in the system
• % Retained Heterosis in 2-breed Rotational Crossbreeding = 67%
• % Retained Heterosis in 3-breed Rotational Crossbreeding = 86%
• Advantages of Rotational Crossbreeding


  • Generates replacement females
  • Uses some heterosis
  • Sire breeds of similar size to produce uniform offspring
• Disadvantages of Rotational Crossbreeding

  • No breed complementarity
  • Loss of heterosis
  • Multiple breeding groups
  • Variation between generations
• Composition of crossbred mean in Rotational Crossbreeding

  Herd mean + 1/2 each direct breed effect + 1/2 each maternal breed effect + 2/3 individual heterosis + 2/3 maternal heterosis
• Example of 2-breed rotational crossbreeding system: Brahman - Angus matings
• Composition of mean of Brahman - Angus (Brangus) crossbred


  • Herd mean + 1/2 direct Brahman breed effect + 1/2 maternal Angus breed effect + 2/3 individual heterosis of Brahman - Angus crossbred + 2/3 maternal heterosis of Brahman - Angus crossbred dams
• Composition of mean in Rotational Crossbreeding Systems

  • 2-breed: 1/2 direct breed effect, 1/2 maternal breed effect, 2/3 individual heterosis, 2/3 maternal heterosis
  • 3-breed: 1/3 direct breed effect, 1/3 maternal breed effect, 6/7 individual heterosis, 6/7 maternal heterosis
  • 4-breed: 1/4 direct breed effect, 1/4 maternal breed effect, 14/15 individual heterosis, 14/15 maternal heterosis
• Three-breed rotational crossbreeding in beef cattle: Charolais - Brahman - Angus, 86% Retained Heterosis
• Advantages of Three-breed Rotational Crossbreeding


  • Generate own replacement heifers
  • Heavier weight from three-breed combination
  • Higher litter size
• Disadvantages of Three-breed Rotational Crossbreeding


  • May produce variability in progeny produced
  • Not capitalizing on maternal heterosis
  • Need more breeding pastures
• Three-breed Rotational Crossbreeding in pigs: Duroc - Yorkshire - Landrace, 86% Retained Heterosis
• Rotational-Terminal Crossbreeding System

  Utilizes the advantages of heterosis (both individual and maternal heterosis are maximised) & breed complementarity (maternal ability in the crossbred dams and growth & carcass merit in sires). Keeps some replacement females. Requires multiple breeding pens or pastures. Rotate sire breed every four years.
• Starting a crossbreeding system with an existing herd


  Determine genetic makeup of the herd

  2. Cull animals that cannot fit plan

  3. Choose sires to produce female replacements

  4. Build a herd of females that fit the environment

  5. Determine market possibilities

  6. Choose some sires that will produce offspring (with the females) that will match the market
• Challenges in crossbreeding

  • Easier to be carried out in herds of more than 50 cows

  Rotate sire breed every 4 years

  Use composite breed

  Requires more paddocks and more breeds of bulls

  Use terminal sire and cross with purchased females

  More records and identification

  Matching different breeds to capitalize on breed differences

  Keeping heterosis and generating females at the same time
• Breeding Objectives for Swine Production

  • Terminal crossbreeding system - mating lean fast growing males to prolific crossbred females with all resulting offspring going to the market

  Rotational crossbreeding system - rotating several of dual purpose sires in the production of market animals and replacement females
• Breeding Goals for Swine Production

  • Terminal sires - Emphasis on post weaning traits

  Dual purpose maternal and dual purpose breeds - Selection on a combination of reproductive and postweaning traits
• Deviation Ratio


  Used to estimate genetic merit of an individual when contemporaries' performance is available. Calculated as (individual's performance - contemporaries' average) / contemporaries' average x 100
• Example of using Deviation Ratio to estimate genetic merit of a boar: Boar A gained 40% faster than his contemporaries
• Breeding Goals for Swine Production

  • Boar A: Deviation from contemporaries group = +0.3, Breeding Value of contemporaries group = 0.5, Breeding Value of boar A = 0.8

  Boar B: Deviation from contemporaries group = +0.1, Breeding Value of contemporaries group = 0.8, Breeding Value of boar B = 0.9
• Terminal sire is crossed to crossbred sows to produce fast growing pigs of superior carcass quality
• Breeds for Swine Production

  • Landrace

  Duroc

  Hampshire

  Yorkshire
• Breeding Objectives for Meat Goat Production

  • Consider production system and market specification

  Tropical environment – climatic and feed factors

  Carcass of medium weight (15 – 18 kg) of less than 2 years of age

  Emphasis on total productivity
• Choosing sire and dam breeds for Meat Goat Production

  • Prolificacy and maternal ability of females/does

  Post weaning traits (ADG and carcass) of males/bucks
• Breeding Goals for Meat Goat Production using Purebreds

  • Seek available breeds – Boer, Jamnapari

  Develop herd improvement programme

  Create own nucleus herd and adopt open breeding scheme
• Breeding Goals for Meat Goat Production developing Crossbreds

  • Choose dam and sire breeds with desirable traits to meet production requirement and market specification

  Crossbreeding and selection

  Develop composite breed
• Breeds to consider for Meat Goat Production

  • Boer

  Jamnapari

  Spanish

  Kacang
• Crossbreeding System for Meat Goat Production

  Dam breeds – Jamnapari, Kacang crosses, Feral

  Sire breed – Boer

  Develop genetically uniform dam line based on Jamnapari breed

  Identify sources of top quality Boer goat semen and bucks

  Develop F1 Boer x Jamnapari crosses

  Interse mate to F4 generation

  Select and upgrade the Boer – Jam composite breed
• A Composite Goat Breed for Meat Production