WHat as happened to the good old  traditional Hereford, Angus and Shorthorn cattle was the cry of despair uttered frequently throughout the country, not that long ago,by both commercial beef breeders and dairy farmers alike, as they struggled with increased calving difficulty, decreased calving percentages and cow herds that could no longer “hack the pace”. Today while some of these problems still exist, many herd owners have learnt from their experiences and are much more selective in the bulls they use. So what created these problems and where did they originate?

    It all started in the late 1960’s/early 70’s when a small group of American researchers decided to investigate carcase composition. In brief ,they slaughtered a group of traditional Angus steers, best described as “blocky” in appearance and compared their carcase composition with a group of less traditional ones that had considerably more “stretch” .

      The entrails and hides were removed from the slaughtered animals and were blast frozen in as close to their natural standing position as was possible. Once frozen, a bandsaw was used to cut the carcases at critical reference points along their length, thereby providing cross-sectional views of particularly the fat and lean content. Many critical measurements were taken, however it was plain to see the “blocky” carcases had a much higher fat to lean than those of their more  “stretchy”  counterparts. News of this research spread like the plague, resulting in a breeding frenzy that rapidly changed the appearance of most breeds in North America.

       By “blindly”selecting for height and length and neglecting carcase conformation, animals quickly took on the appearance of the human equivalent of bean poles.

        These cattle were heavy at birth and had high growth rates, were devoid of fat (efficient converters of feed to lean meat), displayed very shallow muscling, were very late maturing and had high mature weights.

Unfortunately nearly all of these traits are undesirable in an efficient cow herd. One of the ways of breeding taller cattle is to select those with a more upright shoulder blade setting (there is also a corresponding change to the angles in the hind limbs).

 These angle changes, including an  increase in the angle to the hock, reduced the shock-absorbing capacity of the limbs and forced the animals up on to their toes.

    In short they produced unsound cattle. We saw the results of these changes briefly in New Zealand.

    However on our hills, they were a  disaster and quickly culled themselves. These  tall, slabby, late maturing types brought with them very high birth weights consequently damaging the breeds’once bullet- proof, easy calving reputation, particularly in the eyes of dairy farmers. For commercial  beef  farmers the results were equally devastating: increased calving problems, reduced weaning percentages, more dry cows reduced cow longevity and higher percentages of bulls breaking down, just to name a few. One could have justifiably argued that our traditional breeds needed a little extra growth but certainly not in the form these new American genetics delivered it.

     This episode demonstrates the damage that can be created by single- trait selection, which in this case was frame size..

      Some breeders have learnt from this experience, while others haven’t and  there is now a new threat on the horizon in the form of intra-muscular fat or marbling. While   there is plenty of evidence to suggest that it’s presence in meat improves juiciness and flavour, not tenderness, the degree to which the trait is incorporated into a breeding programme needs to be related to its relative economic importance in the production system / market in which it is being used, and also its negative effects on other traits being selected for, for example too much and carcase yield suffers—too little and meat quality suffers.

 

 

Sometimes, it pays

To leave well alone

Livestock

Straight Furrow May 10th 2005

This and that