Crossbreeding Systems - Rengab Genetics
Rengab Genetics
Crossbreeding Systems
http://www.rengab-dairymeat.info/crossbreeding-systems.html

© 2010 Rengab Genetics

Crossbreeding Systems

Performance Crossbreeding Systems

 

Rengab Genetics advises the use of F1 cows and bulls for dairy-meat production, coming from the crosses of the breeds listed on this site, with the fertile and hardy Philippine Cattle Breed cows. We call this Rengab F1. Almost all breeding studies in tropical areas worldwide have concluded that this exotic-local crossbreed is the optimum combination. Of course, given the proper management, feeding, housing and health maintenance.

There are many Crossbreeding Systems as can be seen below. (from http://www.omafra.gov.on.ca/english/livestock/beef/facts/01-011.htm)

1. Rotational

The rotational system requires establishing two or more breeding herds. In a two-breed rotational system, two groups of crossbred cows are established. Cows sired by Breed A are mated to males of Breed B, and females sired by Breed B are mated to males of Breed A.

In a three-breed rotation, a third breed is added to the sequence. In rotational systems heterosis is retained at high levels, 66% in two–breed rotation, 86% in three–breed rotation. However, fluctuation in breed composition between generations can result in considerable variation in level of performance among cows and calves, unless breeds used in the rotation are similar in performance characteristics. Use of breeds with similar performance characteristics restricts the use that can be made of breed differences to optimize breed complementarity.

2. Terminal

In a terminal system all calves are marketed and replacement females are purchased from outside the herd. This allows for more intensive selection for specific traits in the male and female lines used in the cross. Cows are usually selected for moderate frame, good milking and mothering ability. High growth potential and good carcass characteristics are important in the male line. Heterosis benefits will be maximized when a crossbred cow (F1 female) is mated to a sire of a third breed. In a terminal system females are selected to match environment and resources while males are selected to meet end product targets (i.e. growth and carcass). High degree of complementarity and consistency of progeny is possible. Replacements need to be purchased and are price and availability dependent.

3. Composite

"A population made up of two or more component breeds, designed to retain heterosis (hybrid vigour) in future generations without crossbreeding with other breeds." Composite cattle are hybrid cattle that breed to their own kind, retaining a level of hybrid vigour we normally associate with traditional crossbreeding. Management requirement of a composite herd is similar to a straightbred herd, substantial heterosis can be maintained in composite populations so long as adequate number of sires are used in each generation to avoid inbreeding. Heterosis will vary depending on the number of breeds that were used to form the composite. It can range from 50% of maximum possible heterosis for a 2–breed composite to 87.5% for an 8–breed composite. Selection of breeds going into the composite is also critical. Breed differences should be fully exploited so as to match the composite with the environment in which it will be used and to match it with market specifications. Composites have the potential for "standardizing" commercial cattle, thus reducing the variation we currently see in market animals. Problem cattle today, from the feedlot and carcass perspective, are biologically extreme breeds. These extremes in market cattle are due to purebreds, high percentage animals from extreme breeds or crosses of similar extreme breeds. Often the result of poor crossbreeding decisions. With a composite breed, crossbreeding decisions are made when the breed is formed. Commercial producers just need to choose what composite breed to use. Composites are expected to be complete and balanced in performance and only those composites that fulfill this expectation are expected to survive.

4. Combination Rotational-Terminal