Hogget trial

Wether lambs on the ad-lib concentrate diet had significantly higher growth rates than the other two diets with heavier sale weights and carcass weights. Killing out % was highest for the stubble turnip group and lowest for the grass group. Wether lambs slaughtered in March were heavier than November lambs and had higher cold carcass weights but live weight gain and killing out % were unaffected. Carcass conformation of wethers was unaffected by either diet or slaughter date but grass-fed lambs were significantly leaner than either of the other feed treatments and November finished lambs were leaner than March lambs.

Similar results were obtained when the performance of all lambs was compared, with concentrate lambs growing significantly faster, resulting in lambs being sold 6 days earlier and being heavier at sale. Slaughter date did not affect carcass conformation or fatness significantly but grass/silage finished lambs were shown to be leaner with poorer conformation. Overall feed costs during the finishing period were lowest for the stubble turnip groups averaging £3.36/head, which were similar to grazed grass at £3.37 with all the other treatments costing over £10.00/head. This resulted in costs/kg DLWG ranging from 45p for turnips to £1.25 for grass silage lambs. For lambs finished in March there was an additional grazing cost of £3.90 to cover the pre-finishing store period.

For the grass- and concentrate-fed hoggets, there was a deterioration in some quality attributes between November and March, most notably in abnormal flavour (which increased) and flavour and overall liking (which decreased). These flavour changes were more important in determining overall liking than the changes in texture and juiciness between the two slaughter times, some of which favoured the March-slaughtered groups, particularly juiciness. But it is noteworthy that all lamb groups produced meat that was tender. A further exploration of the data plotted fat classification against the attributes in the 8-point score and there was no relationship.

Compared with the UK Controls, both groups of grass-fed and concentratefed lambs had weaker lamb flavour and, apart from the November slaughtered grass-fed lambs, a significantly more pronounced abnormal flavour. On the other hand, both stubble turnip groups had quality ratings on a par with the UK Controls and, moreover, there were no significant effects of season of slaughter on this diet. These three groups were the most preferred of all lamb groups. A variety of stubble turnip had been previously shown (Koch et al. 1987) to produce lamb meat that did not differ in flavour from lambs reared on grass/grain. The overall conclusion is that a diet of stubble turnips delivers a high level and consistency of lamb eating quality through the winter months.

The Problem:

A 2004 report (Factors Affecting Lamb Eating Quality – SEERAD) highlighted the effect of season on the abnormal flavour of lamb, with a significant deterioration in flavour, quality and tenderness post Christmas. This could be a reflection of breed, age, sex, system of production or diet, or a combination of these factors. The key question is whether there is a system of production that delivers a level and consistency of eating quality through the winter months that would restore the retailer’s confidence in British lamb outside the main grazing season.

Project Aims:

1. To investigate the variation in lamb meat quality from winter finishing on three diets
2. To produce information on different systems for producers finishing lambs

Approach:

180 mule x Texel lambs will be split into short-keep (for December finishing) and long- keep (for March finishing) groups. These two groups will be further split into three diet groups: grass and concentrates, concentrates only and stubble turnips; so there will be six treatments with 30 lambs in each one.

Lambs will be selected at fat class 2-3L and between 18-21 kg.  Loin samples will be collected from 16 wether lambs from each treatment. Loins will also be collected from 16 grass-fed British and 16 grass-fed New Zealand wether lambs. A taste panel at Bristol University will be used to assess the eating quality of the 8 groups of lambs.

Deliverables:

A final report will be produced by ADAS, and this will be converted into articles and press releases to disseminate the results of this trial. The results could be used to change current practices used by lamb finishers or in procurement by British supermarkets.