About crossbreeding and the creation of composite breeds Crossbreeding occurs when males and females of different breeds (or even species) are mated and the  resulting offspring are then called crossbreds or “hybrids”.  The hybrid offspring display varying amounts of both breed complementation and “hybrid vigour” or heterosis  which is measured as the performance advantage of crossbreds over the production average of both their  parents. Occasionally, crossbreds will perform even better than either parent; however heterosis should be  measured against the average of the parental breeds. Heterosis can impact many traits, but is especially  useful in improving performance in lowly heritable traits, such as productivity, fertility, adaptability, vitality  and longevity.  The greater the genetic difference between the parental breeds the larger and more dramatic the  expression of heterosis will be. Maximum heterosis is therefore found in crosses between Bos Indicus (Zebu)  cattle and Bos Taurus (European origin) cattle because they do not share any recent common ancestors.   Additional breeds can be added to increase heterosis, but there is a realistic limit to the number of breeds  that usually are included since the management complications multiply as the number of breeds increase.  Another drawback will be the substantial swing in breed composition that occurs between generations and also  between years which results in a great variation in herd appearance as colour, size and body shape.   Presently we have reached this stage in our breeding program. Figures can speak volumes and some of our  production numbers can put flavour to all the dry theoretical talk above (These are not averages but  achievements of individual cows):   - Highest first lactation peak yield of 33 litres per day  - Highest first lactation yield of 9032 litres in 354 days   - Adult cow peak yields of over 40 litres per day  - Lifetime production of over 82.000 litres in 12 lactations  - 14 calvings by 17 years of age  - Average intercalving period of only 331 days over first 10 lactations  - Mortality figures approaching nil  This is what individual members of our “Zebra herd” (as it has occasionally been called with disdain by some  members of the pure-breeding fraternity…) have achieved and most importantly this was done under some of  the most challenging climatic and environmental conditions for dairying imaginable. I believe very few  purebred cows can match some of these figures even under optimal management conditions in the high  altitude regions of Kenya, not to speak of if they had to do this in the coast region with year round high  ambient temperatures, enormous disease challenges and the very low quality of fodder available to them.   Whereas crossbreeding with the goal to produce hybrids has revolutionized production systems from crop  farming to commercial livestock keeping as in poultry (meat and eggs), pig keeping and even some beef  production systems, science has shown, due to complications and limitations described above, that long-term  crossbreeding of dairy cattle for the sake of utilizing heterosis is very difficult unless the intent is to  synthesize a new breed.     Many breeds that are considered purebreds are actually composites if you go back far enough in time. The  understanding of genetics involved in crossing breeds of cattle has progressed enormously in the last 15  years.  We now better understand the results of producing synthetic lines of cattle, which can be maintained  on an ongoing basis when interbred, hence stabilizing new composite breeds. So, composite cattle are a range  of new breeds or new lines of cattle bred specifically to improve hybrid vigor. A planned mating scheme is  designed to combine the desirable traits of two or more breeds into one “package” (or composite).   While hybrids and composites are both crossbreds, hybrids are generally considered to be F1 or first crosses  of purebred parents and composites are a stable inter-mating population originating from crossbred parents.  Composites usually incorporate a combination of breeds, each of which contribute a characteristic desirable  for good performance or environmental adaptability and designed to retain heterosis in future generations  without crossbreeding and then being maintained as a purebred.  Zebu breeds have contributed to several  composites because of their adaptability to hot climates.   Although composite breeds do not sustain as high a level of heterosis as F1 hybrids do, they still offer some  heterosis, with the amount depending on the original breed composition. As more breeds contribute to the  composite, retained individual and maternal heterosis increases.   Composite breeds offer the opportunity to use genetic differences among breeds to achieve and maintain the  performance level (for such traits as climatic adaptability, growth rate and mature size, carcass composition,  milk production and fertility) that is optimum for a wide range of production environments and market  scenarios. Further, composite breeds may provide herds of any size an opportunity to use heterosis and breed  differences simultaneously.   A composite breed must be carefully formed with even greater attention to breed choices and sire selection  than is used in purebred breeding programs. The better the selected sires, the better the final outcome will  be. The commercial user of a composite breed has to worry about few of the constraints that the composite  nucleus herd breeder encounters, as they can be as easily managed as a purebred herd.   Some amazing facts about cross- and composite breeding:   - “KIAN” who was leading the Dutch Holstein charts is actually a 75% Holstein * 25% MRI crossbred  -  “VR Fimbe” is one of the chart leading bulls of Viking Genetics. This Danish Red bull’s genetics are  combined out of 8 dairy and dual purpose  breeds  including Brown Swiss, Montbeliard, Holstein,  Ayrshire and many more! (And I always believed that I alone was truly crazy about crossbreeding...)   - Some of New Zealand’s top index sires over the years have been crossbreds, having better breeding  values than either purebred Holsteins or Jerseys. Semen of crossbred sires is marketed there just as  intensively as that of purebred sires   - The very same imported Norwegian Red sire (Norwegian Red is not even considered a true breed yet…)  was adopted and used by an Ayrshire breeders society as “purebred” Ayrshire and also extensively used  by Dairy Shorthorn breeders in their pedigree breeding program   - Composite dairy breeds are primarily found in hot tropical countries or where cheap pasture based  production is mandatory for the farmer’s survival as for example “Jamaica Hope” in the Caribbean,  “Australian Friesian Sahiwal” and “Australian Milking Zebu” in tropical Australia and…   - “Girolando” in Brazil who where developed through combined effort of farmers and an initiative of the  Brazilian Government and who now produce 80% of the country’s milk   - “Girolando” can produce in excess of 22,000 litres of milk per 365 days lactation!  
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