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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