Somatic cell counts make proof list
MILK producers can now add somatic cell counts to the list of traits on which they base sire selection with the long-awaited release by the Animal Data Centre of SCC proofs for UK proven bulls.
The predicted transmitting ability (PTA) information will enable producers to differentiate between sires which will have a beneficial effect on herd cell count and those which will adversely affect it, says ADC director Gordon Swanson.
"PTAs for somatic cell counts are expressed as percentages," he explains. "Bulls with negative values can be expected to pass on a reduction in cell count; those with a positive PTA will increase SCCs in daughters."
Ranked on ITEM, 55 of the top 100 Holstein Friesian bulls with UK progeny tests have SCC evaluations which are either negative or less than 10%. "There is generally no problem in using these bulls in most herds. But where herd SCC is very high, for example more than 350,000 cells/ml, the aim should be to use bulls with negative SCCs," suggests Mr Swanson.
The top 10 Holstein Friesian bulls ranked on ITEM demonstate a wide range of SCC evaluations (see Table). However, Mr Swanson cautions SCCs have lower heritability than production traits. "We are urging farmers not to over-emphasise their value," he says.
Minimum reliability for publication is 30% and the initial proof of a bull may change substantially as more daughters are added, warns Mr Swanson. *
• Look for negative values.
• Beware: Low heritability.
• Minimum reliability 30%.
Top ITEM bulls
Somatic cell count PTAs for top 10 UK proven Holstein Friesian bulls ranked on ITEM index (February 98)
Bull SCC PTA %
MOET Jenny Ensign 9
Norrielake Cleitus Luke 7
Genus Melville -3
Sir Marke Acclaim 11
MOET Flirt Dilemma 28
Etazon Griffith 20
MOET Alicia Ecliptic 3
Genus Pathfinder 16