research facilities like a dedicated dairy herd ( s ) and breeding scientists .
Local dairy cattle breeding geneticists provide a valuable service to dairy farmers participating in the national milk recording scheme by estimating the genetic merit of dairy cows , heifers and bull for dairy farmers . Farmers are provided annually a herd genetic profile indicating the genetic merit of each animal . Also included are genetic trends for production traits for the herd in comparison to the national herd . However , expanding genetic analyses for other traits is hampered by the non-availability of records like LW and fertility traits other than calving interval . The possibility of estimating genetic parameters for LW , body condition score and fertility traits based on service records has however been demonstrated .
The reason for the lack of breeding and selection research in the dairy industry stems from the fact that breeding requires long term studies . The progeny of sires selected today only complete a first lactation four years later . This should be followed by at least 3-4 generations to enable determining the lifetime effect of a specific breeding programme .
A general misconception exists among nutritionists , veterinarians and research managers that breeding studies within dairy herds are in opposition to short-term feeding trials . Breeding research requires accumulating records of cows over time . Statistical programmes for genetic analyses are adapted to accommodate missing records . Dairy herds used for nutritional research should in any event have a well described breeding objective as a standard operating procedure . It would be easy to include a second breeding objective on a portion of the dairy herd to be able to compare a specific breeding objective ( or treatment ) within the control herd . Records accumulated over time could be made available to geneticists .
Practical experience has shown that limited information is available from commercial herds as records usually do not include a control treatment . Often there is a lack of pedigree information while breeding strategies may have changed over time . Dairy farm breeding objectives are also affected by economic factors and managers which may result in the termination of specific breeding strategies .
Large vs . small cows There is an ongoing debate in South Africa about large vs . small cows . Farmers often indicate breeding towards medium framed cows as part of the herd ’ s breeding objective . At present there is little scientific basis for this and is probably related to the emphasis breed societies put on this trait . Local dairy farmers are not keen to select for higher milk yields mainly because of perceived unfavourable correlations to fertility and LW . With the amount of information currently being recorded on the progeny of service sires , perceived negative correlations can be overcome by applying selection indexes based
AgriKultuur | AgriCulture
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