No abstract

This study investigated the effects of supplementary dietary lipid sources on the fatty acid profile and lipid oxidation of eggs. Five isoenergetic (12.6 MJ AME/kg DM) and isonitrogenous (170 g CP/kg DM) diets were formulated, using a control diet (50 : 50 blend of fish-and linseed oil), fish oil, sunflower oil, high oleic acid (HO) sunflower oil and tallow at a 30 g/kg inclusion level. Two hundred individually caged HyLine Silver-Brown hens (20 weeks of age) were randomly allocated to the five dietary treatments (n = 40 hens/treatment). Birds received the experimental diets from 20 weeks of age. At 30 weeks of age, 12 eggs per treatment were randomly selected for analyses of egg yolk fatty acid methyl esters (FAME), thiobarbituric acid reactive substances (TBARS) and peroxide values (PV). Dietary lipid sources affected FAME, TBARS and PV of egg yolk significantly. The fish oil treatment resulted in the highest TBARS (0.27 mg malonaldehyde/kg yolk) and PV (3.96 milli-equivalent peroxide/kg fat) whereas the HO sunflower oil resulted in the lowest TBARS (0.13 mg malonaldehyde/kg yolk) and PV (2.77 milli-equivalent peroxide/kg fat). Fish oil also resulted in the lowest n-6 to n-3 ratio (1.16 to 1), while sunflower oil resulted in the highest ratio (24.6 to 1). Results indicate that the fatty acid profile of eggs could be altered by means of dietary intervention. However, an improvement of omega-3 type fatty acids of eggs will result in a higher susceptibility to lipid oxidation and possibly a shorter shelf-life of stored eggs. ________________________________________________________________________________

________________________________________________________________________________ AbstractThe influence of a synthetic or natural antioxidant and lipid saturation on the apparent digestibility of nutrients in a standard lamb finishing diet was investigated. The four dietary treatments consisted of the same basal diet, providing 187 g CP-, 355 g NDF-and 71 g EE per kg DM, but differing in supplemental lipid source (30 g/kg of either saturated beef tallow or unsaturated soybean oil) and type of antioxidant included (125 g/ton of either a synthetic or natural antioxidant). The digestibility study was conducted over a period of 12 days (including a 4-day adaptation to the faecal collection bags). Twenty-eight S.A. Mutton Merino lambs (45.1 ± 3.0 kg) were randomly allocated to the four dietary treatments (n = 7 lambs/treatment). Composite feed, feed refusal and faecal samples of individually penned lambs were collected for chemical analysis. The apparent digestibility coefficients, digestible nutrient and available energy content were calculated accordingly. The DMI of the lambs did not differ significantly between the various experimental diets. The inclusion of unsaturated soybean oil reduced the apparent digestibility of NDF in the diet. The apparent digestibility of NDF seems to be higher when a natural antioxidant was included in the diet. The comparatively negative effects of the unsaturated lipid source and synthetic antioxidant on the apparent digestibility of NDF were associated with a significantly lower digestible NDF content in the experimental diet. Accordingly, soybean oil resulted in a significantly lower ME content in the diet. However, estimating ME from DE with a constant factor of 0.8 probably underestimates the ME content of diets supplemented with lipids rich in unsaturated fatty acids. The latter are known to reduce methane production, and hence, energy losses. _______________________________________________________________________________________

________________________________________________________________________________ AbstractA study was conducted to investigate the effects of a synthetic or natural antioxidant and fat saturation, in a standard feedlot diet, on fatty acid composition and oxidative stability of lamb. The four dietary treatments consisted of the same basal diet providing 187 g crude protein (CP), 355 g neutral detergent fibre (NDF), and 71 g ether extract (EE) per kg dry matter (DM), differing in fat source (30 g/kg of either saturated beef tallow or unsaturated soybean oil) and type of antioxidant included (125 g/t of either a synthetic or natural antioxidant). Eighty four S.A. Mutton Merino lambs weighing 27.6 ± 1.7 kg were divided into four groups and randomly allocated to four dietary treatments (n = 21 lambs/treatment) subdivided into 7 replicates/treatment (n = 3 lambs/replicate). After an adaptation period of 8 days, all lambs received complete diets for a further feeding period of 41 days. At termination of the study, seven lambs per treatment, weighing 45.1 ± 3.0 kg, were randomly selected and slaughtered. Loin chops from each carcass were used for fatty acid, colour (a * values) and thiobarbituric acid reactive substance (TBARS) analysis. Meat colour was determined on days 0 and 7 after being stored at 4 ºC under fluorescent light. The malonaldehyde content per kg meat was determined on days 0, 7 and 90 after being stored at -18 ºC in the dark. It was found that dietary treatment had no effect on colour stability as depicted in a * values. The malonaldehyde content per kg meat was higher on days 0 and 90 for the unsaturated soybean oil treatment. Beef tallow inclusion resulted in an increase in palmitoleic acid, where soybean oil inclusion resulted in an increase in linoleic and α-linolenic acids in both lean and subcutaneous fat tissue. Natural antioxidant inclusion in the diet only increased the palmitoleic acid content of subcutaneous fat. The results suggested that the fatty acid profile of lamb meat can be favourably manipulated by the source of fat included in the diet. ________________________________________________________________________________

________________________________________________________________________________ AbstractA study was conducted to determine the effect of different limestone particle sizes in layer diets on bone quality characteristics at end-of-lay hens. Calcitic limestone (360 g Ca/kg DM) that is extensively used in commercial poultry diets was obtained from a specific South African source. Limestone particles were graded as small (<1.0 mm), medium (1.0 -2.0 mm) and large (2.0 -3.8 mm) and included (94.4 g/kg) into isoenergetic (14.3 MJ AME/kg DM) and isonitrogenous (172 g CP/kg DM) layer diets. Sixty-nine, individual caged Lohmann-Silver pullets, 17 weeks of age, were randomly allocated to the three treatments (n = 23) for the determination of various bone dimensional and mechanical properties at end-of-lay. At 70 weeks of age, 10 birds per treatment (n = 10) were randomly selected and sacrificed for the removal of tibia and humerus bones. Different limestone particle sizes had no effect on bone weight, length or diameter at 70 weeks of age. However, an increase in limestone particle size resulted in a significant increase in tibia breaking strength and -stress. These results suggested that larger particles limestone (>1.0 mm) have a beneficial effect on improving the mechanical properties of bone of older laying hens. ________________________________________________________________________________