We have examined the effect of dietary fats containing n-3 polyunsaturated fatty acids on the conjugated linoleic acid (CLA) content of beef m. longissimus lumborum. Four groups of eight Charolais steers were given, for 120 days, grass silage plus a barley/sugar-beet feed concentrate containing one of four fat supplements: Megalac (saturated), linseed (high 18: 3),fish oil (high 20: 5 n-3, eicosapentenoic acid and 22: 6 n-3, docosahexaenoic acid) or linseed plus fish oil. The concentrates supplied 400 g/kg dry-matter (DM) intake and were designed to supply 45 g/kg of the total dietary fat calculated to be 60 g/kg of DM and to contain similar amounts of linoleic acid. Muscle from steers given the Megalac supplement contained 11·3 mg CLA per 100 g muscle and this was increased two- to three-fold in animals given the more unsaturated fat supplements. The increased deposition of CLA was similar for both linseed and fish oil supplements although the concentrations of total n-3 polyunsaturated fatty acids in the fish oil diet were much less than in the linseed diet. This suggests potent inhibition of conversion of CLA to trans vaccenic acid by fish oil fatty acids or their rumen metabolites.

No abstract

Two experiments were conducted to determine whether the decreased proportion of fast muscle fibers seen previously in 2-wk-old lambs from ewes that were dietary restricted from d 30 to 70 of gestation are still evident in older lambs and what the consequences may be in terms of growth rates and carcass composition. Throughout both experiments, ewes were fed on an individual basis according to the recommended dietary allowance throughout pregnancy relative to metabolic BW (BW(0.73)). Control groups were fed as above, and the treatment groups had their nutrient supply reduced to 50% of this recommended allowance from d 30 to 70 (Exp. 1) or d 30 to 85 (Exp. 2) of gestation, after which they were returned to the same level of nutrition as the control group. All twin lambs were kept with their dams, and at 2 wk were given access to creep. After weaning, lambs were individually housed and fed ad libitum to 24 or 17 wk of age for Exp. 1 and 2, respectively. Although not significant (P = 0.18), growth to 24 wk (Exp. 1) resulted in a small decrease in the protein content and therefore an increase in the fat:lean ratio in the carcass of lambs subjected to maternal dietary restriction. This was not apparent when animals were slaughtered at 17 wk (Exp. 2; P > 0.68). Few significant effects of maternal dietary restriction on the fiber type composition of muscles were observed. In Exp. 1 the number of fast fibers increased (P < 0.008) with no effect on slow fiber number in LM. In Exp. 2 an increase in the total number of fibers in male lambs and an increase in type II (A and B) fibers in female lambs were observed in the LM, and an increase in IIB fiber number was observed in semitendinosus (ST) muscle from male lambs. Prenatal maternal dietary restriction during the time of muscle differentiation demonstrated an increase in type IIB muscle fibers and increase in intramuscular fat; although significant, effects on subsequent carcass quality of lambs were relatively small. These data suggest that the lambs adapted to changes in muscle fiber composition previously observed at 2 wk. However, lambs in this study were well fed during postnatal growth. Whether offspring would still have been able to compensate if they had received poor nutrition postnatally and whether that failure to compensate would have influenced carcass composition remain to be determined.

Scollan, N. D., Greenwood, P. L., Newbold, C. J., Yanez Ruiz, D. R., Shingfield, K. J., Wallace, R. J., Hocquette, J. F. (2010). Future research priorities for animal production in a changing world. ? Animal Production Science, 51 (1), 1-5. IMPF: 00.83 Sponsorship: Cocoa Research UKThis paper reports the outcomes from an International Workshop on 'Animal Production in a Changing World' held in Clermont-Ferrand (INRA-Theix, France) on 9-10 September 2009 in which 35 participants from 15 different countries participated. The main objective was to discuss the main challenges within the livestock sector: its environmental impact and role in global climate change; balancing the need for increased production of animal products coupled with a lower footprint and addressing societal needs in terms of product quality for the consumer. Five key lectures presented the main drivers of animal agriculture: population growth, environmental impact, mitigation and adaptation options, efficiency of production and quality of animal products. The key lectures highlighted the synergies between research needs and strategies dedicated to improving food quality and safety and those devoted to decreasing the environmental impact of ruminant livestock production. After the lectures two discussion groups were set up to discuss the main research priorities in relation to reducing environmental footprint and improving product quality. The main remarks from the group working on product quality were that the existing knowledge is not fully applied, the priorities with regards to quality differ between developing and developed countries and that, as one component in assessing food quality, an environmental index needs to be established taking into account carbon footprint, water and energy use. The discussion within the group working on environmental issues highlighted the importance of focusing on whole life cycle analysis in the mitigation area, while the adaptation strategy should be based on selection for profitable animals under different production systems. In summary, a fundamental shift in designing our production systems is required to help ensure present needs for animal products are met without compromising future generations.Peer reviewe