Fat inefficiency

Results for beef

The changes of fat trim and saleable meat during growth have been model in beef based on lipid and protein deposition and growth rates for different breeds, gender and under intensive and extensive feeding system. For example, the ratio of fat trim to saleable meat yield increased from 0.14 to 0.26 during growth from 440 to 630 days of age for a medium-sized breed of steers under intensive feeding.

The energy required at a growth rate of 0.6 kg/d increased from 11.39 to 20.24 MJ/kg when the body weight increase from 200 to 500 kg, indicating the high effect of energy requirement for maintenance with increasing body weight. Doubling the growth rate to 1.2 kg/d increased the energy required to 12.61 and 22.42 MJ/kg for 200 and 500 kg body weight, respectively, suggesting the high efficiency of body growth at low body weight.

The age dependent move through fat and conformation classes of R4L to R4H was 39 (37) and 53 (51) days for a medium-sized breed of steers (heifers) under intensive and extensive feeding system, respectively. For a large-sized breed corresponding age dependent move was 62 (39) and 78 (58) days, indicating the lower fat deposition of a large compared to a medium-sized breed. In particular heifers showed a short time period between those carcass classifications at substantially lower body weight.

Within the finishing period, the feed energy wasted over a range of carcass classifications, occurred in particular for intensive fed beef cattle (e.g. medium-sized breed of steers required during growth from fat class R4L to R4H 4,760 MJ feed energy and resulted in negative profit of -£11.37), whereas extensive fed beef cattle still achieved a profit as defined as return from saleable meat minus costs for feed (e.g. medium-sized breed of steers required during growth from fat class R4L to R4H 5,668 MJ feed energy and resulted in positive profit of £37.07). These calculations include the energy and fed costs associated with maintenance requirements in moving from one fat class to the next. However, the calculation does not include all other variable and fixed costs as well as the difference in return of investment associated with the different finishing systems. The profit decreased substantially with poorer conformation and fat classes.

In beef the average differences in fat trim between sexes were 0.23%, with highest difference of 0.7% in -U4H. Between beef breeds, Hereford showed at fat class 4H 1.8 to 2.4% higher fat trim than Charolais. At mean weight, the intensive fed cattle showed slightly less fat trim than extensive fed cattle.

Results for lamb

Similar models have been developed and resulted for female lambs in an increase in the ratio of fat trim to saleable meat from 0.048 to 0.077 from 100 to 211 days of age.

For female lambs, the time of growth from fat class 2 to 3L or 3H was 26 or 47 days, respectively. For castrated lambs, corresponding time of growth from fat class 2 to 3L or 3H was 35 to 90 days, indicating the higher fat deposition of female lambs.

In lamb, the feed wasted occurred when female animals had moved from fat class 3H to 4L and castrated lamb from 3L to 3H, at a liveweight of 39 kg and above for both sexes, indicating the high maintenance requirements of lambs at those weights. For castrated lambs, the move from fat class 3L to 3H resulted in a deficit of £0.50, whereas the corresponding profit for female lambs was £0.73. The weight of castrated lambs was 2kg higher so that the feed costs associated with higher maintenance requirement of castrated lambs due to higher body weight was the reason for the difference between genders in profit.

In sheep, with increase in fat class from 1 to 5, the fat trim increased by 4.7%, whereas with decrease in conformation classes from E to P, the fat trim increased by only 0.4%.

For the UK, the upper level of the annual benefit of avoiding excess fat during processing was estimated to be £339 m in beef and £66 m in sheep.

Planned activity

The report will be used as part of the BRP selection message, and disseminated through bulletins and briefings.

The Problem

In 2010, 13.6% of beef carcases and 23.3% of lamb carcases were over-fat. This represents massive inefficiency within the industry, both on-farm and in the processing sector. From a producer’s perspective, the major factor that is not fully understood is the feed wasted by laying down unwanted fat. From a processor’s perspective, there is an issue with time spent trimming plus the need for disposal.

Project Aims

• To review the impacts of genetics, age and diet on the tendency of animals to lay down excess fat (15% of report)
• To highlight how the tendency to deposit lean tissue and fat changes over the lifetime of an animal (5%)
• To demonstrate, using example systems, how much energy is required to lay down lean tissue vs fat in megajoules (10%)
• To estimate the time taken to move through fat classes for lambs and finishing cattle (25%)
• To calculate the amount of feed (in DM and MJ) wasted for a variety of carcases – range of conformation and fat classes, and weights – and for the industry (15%)
• To assess the amount of fat trim for a range of carcases – range of conformation and fat classes, and weights – and time spent trimming (15%)
• To explain the process of disposing of fat from the processing sector, with costs (15%)

Approach

SAC will develop a model that will be used to look at the growth of fat and lean tissue as the animal ages.  They will also use information from the lamb VIA and the beef yield trials to calculate the amount of fat trim through a range of carcases.

Deliverables

The results will be disseminated to the industry and incorporated into the BRP selection messages.