Feed Conversion Efficiency Trial

Dairy cows differ in the amount of feed they need for production (feed conversion efficiency) and this $16 million, five-year trial at Whareroa Research Station is identifying most and least efficient individuals. This information will be used to identify genetic markers for efficiency so this trait can be used for future breeding and reduce the amount of feed required for production. From April 2013 LIC will be promoting a gene marker service for feed conversion efficiency available to farmers.

The feed conversion efficiency (FCE) trial, funded by government and by New Zealand dairy farmers, is being run by DairyNZ, LIC and NZ Trade and Enterprise with a sister trial also being run in Australia. International collaboration is needed because about 2000 animals need to be evaluated to identify the genetic marker for FCE, and also because of the costs of this research. The trial’s ultimate aim is to increase productivity in the dairy industry by selecting cows which are the highest converters of feed to milk and identify these by their genetics.

Feed conversion efficiency is important to the New Zealand dairy industry as current selection and breeding criteria for dairy cows are based on a theoretical (not measured) feed consumption, so the gains in productivity are achieved by genetic improvements with no account taken of the actual quantity of feed required.

In a dairy system, FCE is considered to be the efficiency of production from a known amount of feed. Production includes milk, live weight gain (for example muscle and fat) and calves produced. This is best estimated over an entire season of milking.

FCE is not a new concept. It has been used to select efficient pigs and poultry for decades, but measurements in cattle are relatively recent and this trial is the only one involving dairy cows fed forage diets. There have been two main challenges that have prevented FCE measurements in pasture fed dairy cattle. It is very difficult to measure pasture intakes (so this trial uses dried lucerne for screening) and it is much more difficult to measure liveweight gain or production from a large number of cattle, compared with pigs or poultry. This is because cow live-weight varies by 20-30 kg/day (depending on rumen fill) and milking cows often gain or lose condition, which is hard to measure accurately.

The trial began in 2008, with construction of a 28 pen (each 6 x 8 m) facility, each pen having 8 animals and a single feeding station so that only one animal can eat at a time. The animal is identified (electronic ID) as it enters the feeding station and the time, duration and quantity of feed eaten is recorded automatically. The calves are aged between 5 and 9 months when in the facility and are fed for 50 days, after a 10 day acclimation period. The chaffed lucerne has been pressed into cubes (22mm square) and imported from Canada. The cubes don’t fall apart, are palatable, and most important, intakes can be measured accurately.

Although the aim is to select animals with divergent FCE for milk production, the efficiency is being assessed initially by measuring live-weight gain. It would be impractical to measure milk production and feed intake from 1000 milking cows, but efficiency is based on the animals’ biochemistry, and biochemistry will apply in a similar way for milk synthesis, live-weight gain and maintenance. Screening of calves was completed mid 2010 and 10% of the most and least efficient weaners were retained to calve at 2 years of age, so additional measurements could be carried out.

LIC procured the calves for the NZ section of the trans-Tasman trial, with high breeding worth (180-200), typical of those which would be in the national herd in a few years. They were purchased at four days, reared on milk and powder elsewhere and then brought to the facility after weaning at 60 days. They feed only on the lucerne cubes for 26 days and are weighed three times week. Intakes of calves (weaners) were during January to mid-May. Then some of the calves were screened again as lactating cows to ensure that FCE was permanent.

The spread of feed conversion efficiency was demonstrated, in that the 20% most efficient cattle ate 10% less than the 20% least efficient, even though their liveweight gains were the same.

The efficient calves needed 1.2 kg DM/day less for the same weight gain than the average. This is about 15% less than average. Another group needed about 1.2 kg more DM/day than the average.

Calves in the top and bottom 10% for conversion efficiency were retained for future research looking at feed intake and subsequent milk production. No disadvantages have been observed in the high FCE animals subsequently.

A key component of this programme is to ensure that efficient cows are robust and that selection for improved FCE has no detrimental associations with reproduction and health.

Their own calves (second-generation) are now being evaluated in the research facility (February 2013), to demonstrate the heritability of feed conversion efficiency.

Taranaki Research Farm Profile

• Farm area 110 ha effective
• Milking cows 350 cows depending on scientific requirements
• Soil fertility Egmont black loam
• Paddocks 20 (1/2 ha paddocks) 100 (1 ha paddocks)
• Dairy infrastructure 40 – bail rotary dairy
• Automatic cow ID, daily electronic milk weight recording
• Feed Conversion Efficiency stall 28 stalls with ID-controlled electronic weighing feed bins