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Texel LAMBPLAN Trial investigates growth and muscle EBVs
The European approach to carcase classification

Texel LAMBPLAN Trial investigates growth and muscle EBVs.

The WA Texel Breeders Association PIRD trial demonstrating to producers, processors and retailers the influence of the LAMPLAN growth and muscle index on body type, market preference and retail value of prime lambs has continued with the remaining lambs carried through to heavier carcase weights. The first part of the trial involved measuring the production differences between these lambs at the sucker stage and a summary of these results and some background information are presented below.

• Sucker lambs from rams with high estimated breeding values (EBVs) for growth had faster growth rates, heavier carcase weights but smaller eye muscles than sucker lambs from rams with high EBVs for muscle.

• Carryover lambs from rams with high EBVs for growth had heavier carcase weights but lighter loin and rack cuts and lower retail meat yields than carryover lambs from rams with high EBVs for muscle.

LAMBPLAN provides two indices in which the estimated breeding values (EBVs) for growth, fat and muscling are weighted as either 60% growth, 20% fat and 20% muscling (60:20:20) or 80% growth, 10% fat and 10% muscling (80:10:10). As a very high EBV for one trait will compensate for a lower EBV in another trait, rams can have an equally high index, but have very different muscling and growth EBVs. There are two very different carcase types that correspond to high growth and high muscling EBV in high index rams, making them suitable for different markets.

A trial was set up to compare the progeny of high index rams with either high EBVs for growth or high EBVs for muscle. The individual ram EBVs and index values shown relate to their performance at post weaning age, which is aimed at weight range 40-70kg liveweight (Table 1). The Carcase+ index is similar to the 60:20:20 index, but has been calculated using post weaning figures assessed at liveweights 45-70kg. This makes the index a better estimate of performance for a producer of prime lamb in the carcase weight range 20-24kg.

Table 1. Average EBVs and index values for the high muscle and high growth rams.

‘960002, 970003 muscle group rams. 980044, 970062 growth group rams.
(Click on image for enlargement)

The main findings from the sucker slaughtering were that lambs sired by high growth rams had heavier liveweights and carcase weights while lambs sired by high muscle rams had higher dressing percentages, deeper eye muscles and lighter coloured meat. There were no differences between groups in fat cover measured as GR tissue depth.

The growth group was significantly heavier liveweight than the muscle group for both first and second cross lambs at 4.1kg and 5.2kg respectively and 1.1kg and 1.4 kg for hot carcase weight. The diminishing difference between groups from liveweight to carcase weight indicated a higher dressing percentage from the muscle groups.

Lambs that did not reach slaughter weights as suckers were held on a maintenance diet as they were destined for the WA domestic market (18 –23kg) and therefore made little weight gain during summer. On the 4^th February they were put into a feedlot to finish and were slaughtered on the 22^nd March 2001.

Lambs were carried through summer at almost constant weight going into a feedlot on 4^th February to prepare for a late March slaughter. 189 lambs were slaughtered on 22^nd March 2001, and all were measured the following day for GR tissue depth with hot carcase weight also recorded. These measurements were used to select 10 carcases per group, to be boned into retail meat cuts. The carcases were selected by taking 5 either side of the average hot carcase weight for each group, and as close as possible to average for GR.

The carcases were split in half down the spine, with the fore quarter, leg and loin sections then cut and weighed separately. The loin and leg sections were fully boned out to retail products, while the fore quarter section was made into a standard square cut shoulder product. Total fat, bone and trimmings were recorded for each carcase. The boning was completed by four boners from Goodchild Meats, and each boner dealt with a random selection of lambs from each group.

The data was analysed using growth and muscle groups for first and second cross lambs, which included the progeny from the two sires used in each group. A linear regression model was used to account for boner and CWT.

The growth rates of each group ranged from 252 to 285 grams per head per day for one month on feedlot with the 2^nd cross muscle recording the highest daily weight gain but none were significantly different (Table 2). There were no differences between growth and muscle groups for GR measurement.

The boned leg products were of similar weights with only the muscle group’s average silverside weight 51g heavier than the growth group in the second cross lambs (Table 3). This difference translated to a 2% higher average leg meat yield and $0.58 greater average leg meat value for the second cross muscle half carcase compared to growth. This amounts to $1.16 per carcase and $1,160 over a drop of 1000 lambs, a substantial reward for meat processors paying on hot carcase weight only.

The muscle groups had a heavier loin in both the first and second cross lambs and a heavier rack in the second cross lambs. This improved backstrap meat yield and total backstrap value but the difference was not significant (Table 4). If the increased values of each leg ($0.58) and each backstrap ($1.04) in the second cross lambs are combined, the total increase in retail value of a carcase from the muscle group is $3.24 per head.

There were no differences between growth and muscle groups in either first or second cross lambs for weight of fat (Table 5). The muscle group had 0.132 kg less bone than the growth group in the second cross lambs.

Trimmings from the boning of leg and loin were measured, but not included in the analysis due to large differences in the components of trimmings between boners. The Square cut shoulder could not be analysed either due to missing values from one boner.

Lambs sired by the high growth rams were heavier and grew faster than lambs sired by the high muscle rams, at the sucker stage. However, as carryover lambs there was no significant difference in liveweight between the two groups, with the lambs sired by the muscle type rams growing equally as fast as the lambs sired by the growth type rams in the feedlot. This may be because by this age and stage of maturity the growth type lambs were starting to plateau in growth rate as they approached their potential frame size, while the muscle type lambs were able to continue to put on flesh.

Lambs from the high muscle rams tended to contain more muscle than lambs from the high growth rams. This was evident in the first cross sucker lambs which had larger eye muscles and in the second cross carryover lambs which had heavier loin and leg retail cuts. The use of a high muscle ram not only improved meat yield, but also had the most impact on the yield of high value cuts.

Using well-muscled rams to produce progeny with higher meat yields will become increasingly important, especially if WA processors implement VIAscan and payment grids become based on lean meat yield. However, under current marketing systems which are based on carcase weight a high growth index is more profitable for the producer while the high muscle index is more profitable for the processor, as the current weight and fat payment system does not identify and reward producers for high yielding carcasses.

The full results of the trial will be available on www.texel.org.au

The WA Texel Stud Breeders Association would like to thank sponsors of the trial; GENSTOCK and A&A Branding Company for their support and also Goodchild Meats and the Department of Agriculture for their collaboration and resources.

The European approach to carcase classification

Dr Sarah Wiese and Maria Wood

“Chuckem” Narrogin and “Te Rakau” Bindi Bindi

The issue of establishing a payment system which accurately rewards carcase value has been tackled differently by different countries. In Australia the use of weight and fat score grids as a payment system is well established and utilised however there has been no widespread use of a conformation classification system. The VIAscan video image anaylsis technology has been developed to improve predictions of lean meat yield however adoption and implementation of payment systems based on VIAscan data has not been rapid.

This article looks at the implementation, use and perceived benefits of using carcase conformation classification systems in Europe.

In most European countries a visual conformation classification system forms part of the carcase assessment process along with a fat cover assessment. Lamb classification in the EU is on a voluntary basis and is not a requirement under EU law, unlike beef where it is a statutory requirement. There is no standard European scheme in place and systems vary slightly between countries although most are based around the EUROP conformation grading system and a visual numeric fat score.

France

The French government has adopted the SEUROP grid as obligatory. The objective of this classification was to ensure greater transparency in transactions and to encourage production of carcases of better quality (less fat and greater yield).

This system has encouraged

• Producers to no longer produce carcases which are too fat, and not appreciated by the consumer, and to make use of improved genetics to obtain greater meat yields.
• To renumerate producers according to the quality of the carcase based on a grid of conformation score and fat score.

Sweden

Sweden had one of the earliest classification systems in place. By 1964, 70-80% of the meat sold in the Stockholm meat market was sold by description without inspection. All carcasses produced in Sweden intended for sale on the open market have to be classified according to rules issued by the Swedish Board of Agriculture.

Carcases are classified according to age (suckler lamb, lamb or sheep), conformation and into seven classes for fat from M (completely lacking) through to L (light), N (normal), B (3-5 mm), C (5-10mm), D (10-15mm) and E (more than 15mm). For the fatter classes a linear measurement of fat depth over the loin muscle is made between the 10th and 11th rib by making a cut and inserting a rule. Making the measure similar to our C site fat measurement rather than GR tissue depth used in the Australian fat scoring system.

Netherlands

Neither are the wholesalers or retailers willing to pay for the SEUROP system as they prefer to make a visual selection to suit their different markets.

United Kingdom

The UK first implemented a classification system in 1973, this used 5 numeric fat classes based on visual assessment and four conformation scores, ‘Z’ very poor, ‘C’ poor, average (no letter code) and ‘E’ extra. More recently the UK has adopted the EUROP classification for conformation (there is no “S” grade used for sheep in the UK ) and retained the numeric (1-5) assessment for fatness.

The scheme is designed to describe the main characteristics of the carcase without attributing any qualitative judgement. The main objective is to indicate the likely yield of the carcase - of course the actual yield will depend on the butchery specifications in place in a particular business.

The selection of the particular approach (EUROP and numeric fat scale) was based on the assumption that there would ultimately be a Europe-wide classification scheme for sheep. The classification scheme was therefore based on the existing Europe-wide scheme for cattle as it was felt appropriate to devise a scheme that was likely to match any future European requirements.

The reason for the introduction of the EUROP scheme was the desire for a common language for describing the carcase to improve industry communication. The main argument was that farmers were not being paid fairly for better animals and therefore there was little incentive for breed improvement. Over fatness has always been considered as the main issue with carcase quality in the UK . Introduction was not driven by any concerns over consumer satisfaction and there was no intention for it to be used as a prediction of eating quality.

Advantages of classification

Some of the initial reasons for and concerns with adopting a system of classification in the UK are described in a report ‘Inquiry into Fatstock and Carcase Meat Marketing and Distribution’ completed in 1964. Most of these reasons are still equally relevant today and were as follows;

• To provide an effective means of reflecting consumer preferences back to the producer. The resulting price structure should stimulate the supply of those kinds of meat most in demand.
• To provide a more reliable means of reflecting the costs of production and marketing different kinds of meat through the marketing system to the producer.
• To reduce marketing costs, since retailers could buy by description over the telephone without a personal visit to inspect carcases.
• To encourage long term contract trading directly between producers and retailers as the existence of standard descriptions would enable contract specifications to be more readily described, adhered to and checked.
• To assist deadweight marketing since the classification could be used as a basis for deadweight pricing.
• Price comparisons would be made easier across the trade and inter-regional trade would be facilitated.

Most of the concerns with the adoption of a classification system were in relation to;

1.       The classification system being practical.

2.       The cost of operating such a scheme.

3.       The room for subjectiveness and therefore differences in standards.

4.       That it does not attempt to grade carcases on an eating quality characteristics.