19 March 1999

Cattle genes key to feed conversion rate

FEED conversion efficiency traits are as heritable as growth rate traits in beef cattle.

The heritability of 0.46 was discovered by Australian researchers investigating net feed efficiency.

MLC beef scientist Duncan Pullar last week told delegates at a technical workshop in Cirencester, Glos, that there is tremendous potential for improving breeding programmes by selecting for feed conversion efficiency.

"There is a lot of variability among beef cattle for this trait. But headway in breed improvement could be made in only a few generations by selecting and breeding with better performers who have a good chance of passing on these genes.

"But we havent the structures in place to identify superior performers, and its difficult to measure individual feed intakes," he explained.

Dr Pullar said that trials on a large scale were so expensive it was prohibitive and therefore the MLC could not currently be involved.

The Australian research is still at an early stage but hopes are that genetic markers can be established for these traits. This would help avoid measuring large numbers of individual animals, but was a long way in the future, he said.

However, at least one breed society is investigating some performance comparisons involving feed efficiency, said Dr Pullar.

The Limousin society-backed bull testing station at Richard Bradleys Westmoor Farm, Finghall, Yorks will monitor individual feed intakes. It will therefore be able to rank bulls at the station on feed conversion efficiency, he said.

Crushed oilseed rape feed viable milk yield boost

BOOSTING milk yields by feeding crushed rapeseed is viable for dairy producers, according to CEDAR research.

Chris Reynolds of Reading University told delegates at a technical workshop held in Cirencester, Glos, last week that feeding crushed double low oilseed rapeseed is an effective way to boost milk yields.

Feeding rapeseed up to 3% dry matter inclusion had no adverse effect on feed intake. It also led to increased milk yield without changing milk protein and milk fat composition, he said.

"Decide what you want from your cows. If it is high yield then increasing fat content by adding crushed rapeseed to the complete diet could help."

Results from the trial, which involved feeding four different grass silage-based diets to 40 cows over a 20-week period, showed positive benefits for including rapeseed.

"But we didnt feed them rapeseed, to give extra fat, until they were in peak lactation and we carefully introduced a change in diet over a week to stop feed intakes dropping."

However, a digestibility trial showed that when rapeseed was used in complete diets alongside maize and grass silage there was a significant drop in milk fat levels. This could have been due to a change in the rumen environment caused by adding maize, said Dr Reynolds.

Producers contemplating adding rapeseed should use a feeder wagon to ensure that the diet remains palatable and cows feed intakes are maintained. Other considerations are cost, storage and processing.

"Work out how much rapeseed will cost and whether you can process it cheaply. For example, access to a portable crimper could be useful as this is an effective way to crush rapeseed," he said.

Rapeseed costs £122/t, and crushing costs £15/t, giving a total of 38p/kg fat. "However, including the protein benefit from adding rapeseed – worth 15p/kg protein – means the adjusted cost for fat is 23p/kg."

This compares favourably to commercial fat additives, such as Megalac at 55p/kg fat, he said.

Despite concerns of how long crushed rapeseed stores it lasted for up to six months in fertiliser bags during the trial without showing any signs of becoming rancid. &#42

CORRECTION

WHERE grass contamination is a concern, grass N content is too high, sugar levels are too low or grass quality is poor, silage must be made in good weather conditions, and not as suggested in the article on silage making in last weeks Grass and Forage supplement.

Steven Edmunds also wishes to point out that out of the best performing 50% of additives, the bottom 25% will give a result in two out of ten occasions, while the top 25% will give a result nine out of ten times. &#42

SHEEPTAGGING

NSA supports tagging sheep with a flock identification only, and not sequential numerical tags. This may have been misinterpreted by some readers in last weeks SIA Paris Show report. &#42

BSASfree offer

STUDENTS can now join the British Society of Animal Science free of charge.

The society, which holds its annual conference in Scarborough, Yorks, next week, is offering free membership for undergraduate students. It hopes to attract more young scientists who will continue to be members when they move into industry.

Student members will receive a quarterly newsletter covering latest research and developments, reduced rates at society meetings, papers from the annual conference on CD-ROM, and the opportunity to enter for scholarships and prizes administered by BSAS. It also runs a summer placement scheme, helping students obtain relevant placements. &#42