LIMOUSIN CALF TRIAL CONFIRMS WORTH OF EBV

Posted 29 October 2001

THE USE of a high Beef Value Limousin bull can dramatically increase the financial value of commercial finished calves, the results from a trial at Harper Adams University College, Shropshire, have shown.

The trial, which compared Limousin calves sired by bulls with either a high Beef Value or below average Beef Value, was carried out by the university college’s animal science research centre for the British Limousin Cattle Society and the MLC.

Simon Marsh, senior lecturer at Harper Adams, who supervised the trial, said: “Beef Value is an assessment of the economic genetic merit of an animal. In the trial, the theoretical economic difference between the progeny from the sires should have been £11 per calf in favour of the bull with the high Beef Value.

“In this study the difference in financial value was £17.10, exceeding the predicted value by £6.10 per calf. The majority of the results from this trial confirm that Estimated Breeding Values (EBVs) can provide a reasonably accurate measure of an animal’s genetic merit.”

Pedigree beef cattle breeders who record with the Signet Beefbreeder service have their records analysed by a Best Linear Unbiased Prediction (BLUP) which uses the weights and measurements that have been recorded for an individual - and its relatives - to determine likely performance of progeny.

The analysis calculates EBVs for several traits of economic value, which are the assessment of genetic merit of the animal. Using BLUP methods, consistent genetic improvement has been made.

EBVs are calculated for 200-day weight, 400-day weight, fat depth, muscle depth and muscle score. An economic assessment, or index, is calculated using this data, called the Beef Value. EBVs are also calculated for birth weight, calving ease and gestation length, to give an index called Calving Value.

The trial Limousin calves were bred from the college’s Holstein-Friesian dairy herd. Their sire was either the high Beef Value bull, Ronick Hawk (LM 29) which is in the top 10 per cent of the breed, or the below average Beef Value bull Staveley Hurricane (LM 7) which ranks in the bottom 25 per cent of the breed.

Calves were reared through to slaughter on a fermented whole-crop wheat silage/cereal beef system. The performance of the heifer calves was also compared to some market purchased calves.

“The calves sired by Ronick Hawk recorded significantly higher carcase weights compared to the calves sired by the low EBV bull,” said Mr Marsh. “While the statistical analysis of the data indicated no significant differences in any of the other measured traits, the Ronick Hawk calves recorded superior daily live weight gains, slaughter live weights, conformation scores and killing out percentage.”

The majority of abattoirs require carcasses weighing from 260 – 380kg grading at fat class 3 or 4L with a conformation grade of R and above with carcasses outside this specification financially penalised.

Achieving minimum carcase weight is of particular concern for intensively reared heifers. Ronick Hawk-sired heifers (table 2) recorded heavier carcase weights compared to the calves sired by the lower EBV bull and the market purchased calves. Only 25 per cent of the Ronick Hawk heifers were below 260kg, compared to 62.5 per cent and 63.6 per cent of the low EBV bull and the market purchased calves respectively.

Calves sired by Ronick Hawk recorded heavier slaughter live weights and carcase weights and were 26.9kg and 16.0kg heavier (average for bull and heifer calves) respectively. However, the Ronick Hawk bull and heifer calves took an extra 4.8 and 15 days respectively to reach slaughter condition compared to the low EBV bull’s calves. The heifer calves sired by the low EBV bull recorded similar performance to the market purchased calves.

The trial began in April 1999 with the insemination of the college’s Holstein-Friesian dairy cows.

Calves were born from January to March 2000 and reared through to slaughter on a silage/cereal beef system with 14 bulls and eight heifers per sire. A further 11 Limousin cross Holstein heifers of unknown breeding were purchased as reared calves in June 2000 and reared alongside the heifers.

From birth the calves received a minimum of three litres of colostrum within six hours. They were then transferred to individual calf pens and reared to weaning at five weeks of age on a low cost early weaning system, with four litres per day of whole milk plus ad-lib early weaning concentrates.

During the period from weaning to six months old, they received ad-lib 14 per cent crude protein proprietary intensive beef nuts as well as ad-lib straw. From six to 14 months old they received ad-lib silage (fermented whole-crop wheat at 41.7 per cent DM, 11.6ME, 8 per cent CP, 30.7 per cent starch) plus restricted trough-fed 17 per cent crude protein concentrates (bulls 4.0kg, heifers 2kg per head per day)

From 14 months old to slaughter they were fed ad-lib 13 per cent crude protein protein barley/soya concentrates plus ad-lib straw.

The original objective was to finish the cattle at approximately 14 months old on the silage beef system, with increased concentrate feeding levels prior to slaughter to achieve fat class 3 (bulls) and 4L (heifers). This plan changed due to the outbreak of foot and mouth disease in the UK in February 2001 since it was not possible to market the cattle in March or April.

The concentrate feeding levels were therefore ‘held back’ to delay fat deposition. In May however, the stocks of whole-crop became depleted but with the recommencement of the marketing of fat cattle, the decision was therefore taken to finish the cattle on ad-lib cereals.

Feed intakes were recorded on a group basis from the start of the trial and were recorded through to slaughter.

Total feed intake for the heifers was 2,406 kg/head of DM compared to 3,029 kg/head for the bulls. The estimated feed conversion ratio at kg DM feed to kg gain was 5.42 for heifers and 5.31 for bulls.

Gross margins per head were calculated based on the feed prices prevailing at the time of the trial - rearing concentrates at £150/t; finishing concentrates at £95/t; whole-crop at £60/t DM (this includes seed and establishment, fertiliser, sprays, harvesting, additive, storage costs and rent for a 11t DM/ha yield and excludes area aid payments). All cattle were sold to ABP, Shrewsbury.