Animal and Aquacultural Sciences
Daniel Elius Mushi defended his PhD thesis on 27th May 2009
Ane Gro Siri Skjelfjord
Strategies for improving quality of meat produced from lambs and goats in Norway and in Tanzania – influences of species, breed, sex, age and diet
In Norway, sheep are more popular for meat production than goats. The per capita consumption of mutton is estimated at 5.6 kg per annum, whereas the consumption of goat meat is negligible. Due to seasonality in forage availability, lambs are traditionally slaughtered directly off the mountain grazing to minimize feeding cost. Because of natural variation in weight and lamb condition, however, autumn grazing of some of the lambs on cultivated pastures, supplemented with concentrates, is a common practice in most parts of the country. Such a feeding practice might affect productive performance and meat quality of lambs involved. In Tanzania, unlike in Norway, goats are more popular for meat production than sheep. Goats are raised and finished on pastures, which in most cases are of poor quality, hence take long time to reach slaughter weight and produce carcasses of low uniformity and meat of low tenderness. It can be hypothesized that finishing such goats on concentrate supplement will reduce time to attain slaughter weight, improve quality of carcass and meat produced. Therefore, the existing production systems for sheep and goats in Norway and in Tanzania were studied based on the quality of carcass and meat produced. In addition, response of such systems to different interventions was evaluated in order to increase the share of goat and lamb meat in the total meat consumed in the two countries.
The study was divided into four main experiments. Experiment I evaluated the effects of concentrate feeding regimen, breed and sex of an animal on carcass and meat quality of Norwegian lambs. Experiment II assessed the effects of sex of an animal, month/season of slaughter and feeding intensity on ram flavour in Norwegian lambs. Experiment III examined relative potential of Norwegian lambs, Norwegian and Cashmere goats for meat production. Finally, experiment IV evaluated the effects of concentrate feeding regimen on growth and distribution of non-carcass components, carcass and meat quality of goats in Tanzania.
In experiment I, lambs on ad libitum
access to concentrate had about 5 kg heavier carcasses than those on restricted access. Meat taste intensity increased with level of concentrate supplementation. Difference in meat tenderness between ram and ewe lambs was only evident on ad libitum
concentrate feeding. Nor-X lambs had higher scores for carcass conformation than Norwegian White lambs. Seasonal variations in meat sensory quality were observed in experiment II. Whereas meat from ram lambs slaughtered in September had no noticeable ram taste, meat from such lambs slaughtered in March/April and October/November had noticeably 1.2 units and 0.6 units higher ram taste, respectively, than that from ewe lambs. In experiment III, M. Longissimus dorsi
samples from lambs were less red (a*) and had lower colour intensity (C) and wider hue angle (H) than that from goats. Meat from lambs and Cashmere goats had higher proportions of saturated fatty acids (SFA), especially stearic acid, than the meat from Norwegian goats. Sensory panelists scored lamb meat fattier, juicier and more tender than goat meats. In experiment IV, the proportion of total non-carcass fat (TNCF) in both total body fat (TBF) and empty body weight (EBW) increased with increasing level of supplementation, mainly due to omental fat. Seemingly, the proportion of TNCF in TBF for F1 crossbred goats was higher than that of Small East African (SEA) goats. Goats with ad libitum
access to concentrate supplement (T100) and those with access to 66% of ad libitum
concentrate allowance (T66) were similar in carcass fatness scores, but both were fattier than other diet groups. For goats without access to concentrate (T0), pH-values remained above six even after 24 h post-mortem. Cooking losses increased with increasing levels of concentrate supplementation.
It is concluded that finishing Norwegian lambs on ad libitum
access to concentrate increase quantity of meat produced without degrading its quality. Finishing F1 crossbred goats at access to 66% of ad libitum
concentrate allowance gives optimum carcass and meat quality, and that any increase above this level seems not to improve meat production. Based on the results from sensory assessments of meat, ram lambs should be slaughtered before October, when lambs are below 6 months of age, to avoid off-flavour on meat. The present study has illustrated that Nor-X lambs are superior over Norwegian White sheep based on carcass conformation scores. Furthermore, goats preferentially deposit fat internally as omental fat and F1 crossbred goats have higher non-carcass fat than SEA goats. Finally, meat from Norwegian lambs and Cashmere goats have comparable but higher proportion of SFA than that of Norwegian dairy goats. However, since C18:0, with neutral effect to plasma cholesterol level, was the main contributor of higher SFA in both Norwegian lambs and Cashmere goats, meats from them are nutritionally comparable to that of Norwegian dairy goats. Thus, goat meat is nutritious and different from lamb meat; it should be marketed separately. Promotion for increased consumption of goat meat can be based on its salubrious fatty acid profile.Keywords:
Concentrate supplementations, growth performance, lamb finishing, sensory quality, meat quality, Norwegian lambs, time of slaughter, lambs, goats, breed, fatty acids, production factors, technological factors, critical checkpoints, feedlot-finishing, carcass yield, chevon quality, concentrate feeding, non-carcass yield
Updated: 01.07.09Printerfriendly version
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