Masters Degrees (Animal, Wildlife and Grassland Sciences)

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Browsing Masters Degrees (Animal, Wildlife and Grassland Sciences) by Advisor "Einkamerer, O. B."

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    The effect of dietary lipid saturation and antioxidant sources on performance and meat quality of lambs
    (University of the Free State, 2014-05-27) Booyens, Käte Erna; Einkamerer, O. B.; Hugo, A.; Van Der Merwe, H. J.
    English: A study was conducted to investigate the influence of antioxidant source and fatty acid saturation in a standard finishing diet on apparent digestibility, production performance, fatty acid composition and oxidative stability of lamb. The four dietary treatments consisted of the same basal diet (187 g CP- and 355 g NDF/kg DM) differing in the lipid source (30 g/kg of either saturated beef tallow or unsaturated soyabean oil) and type of antioxidant included (125 g/ton of either a synthetic or natural antioxidant). Eighty-four S.A. Mutton Merino lambs (27.64 ± 1.72 kg) were randomly allocated to the four dietary treatments (n=21 lambs per treatment) and subdivided into seven replicates per treatment (n=3 lambs per replicate). After dietary adaptation of 8 days all lambs received the experimental diets for the remaining period (41 days). A digestibility study was conducted over a 12-day period (4-day adaptation to the faecal bags followed by an 8-day collection period). Seven lambs per treatment were randomly selected and slaughtered at completion of the production study. Physical carcass characteristics, muscle pH, muscle- and subcutaneous fatty acid composition, as well as meat oxidative- (malonaldehyde content) and colour stability was measured. The apparent NDF digestibility was reduced (P =0.0548) with the inclusion of unsaturated soyabean oil in the diet compared to saturated beef tallow. This was associated with a significant (P <0.05) lower digestible NDF and ME content in the experimental diet. No significant (P >0.05) differences in dry matter intake, daily gain and feed efficiency of lambs occurred. The addition of unsaturated soyabean oil significantly increased (P =0.0003) the efficiency of ME utilisation in the diet. Lipid saturation level in finishing diets for lambs did not influence (P >0.05) the physical carcass characteristics and meat pH of lambs. Saturated beef tallow increased (P <0.05) the monounsaturated palmitoleic- and oleic acid content of lamb subcutaneous and/or muscle tissue, whereas the more unsaturated soyabean oil increased (P <0.05) the polyunsaturated linoleic acid, α-linolenic acid and CLA content of both muscle fat and subcutaneous lipid tissue. Monounsaturated vaccenic acid was increased in lamb meat when unsaturated soyabean oil was included in combination with the natural antioxidant. The total PUFA, total n-6 fatty acid and PUFA:SFA ratio of lamb meat increased (P <0.05) with the inclusion of the more unsaturated soyabean oil in the diet. A higher (P <0.0001) n-6:n-3 ratio occurred in the intramuscular fat of lambs fed the unsaturated soyabean oil diet. Unsaturated soyabean oil negatively influenced (P <0.05) the oxidative stability of lamb meat on days 0 (fresh) and 90 (frozen), compared to saturated tallow. The inclusion of a synthetic compared to a natural antioxidant in the diet decreased (P =0.0672) the apparent digestibility of NDF, which was also associated with a significantly (P =0.0159) lower digestible NDF content of the experimental diet. The meat pH measured 45 minutes after slaughter was significantly (P =0.009) decreased when a synthetic antioxidant was added to the diet. Meat pH measured at 24 hours post slaughter was lower (P =0.0433) when a natural antioxidant was added to the diet. With the exception of the natural antioxidant that increased (P <0.05) the saturated palmitic- and monounsaturated palmitoleic acid content of subcutaneous and/or muscle fat, and decreased (P <0.05) the monounsaturated stearic acid content of intramuscular fat, dietary antioxidant type did not to effect (P >0.05) the fatty acid composition of lamb meat, neither the colour- nor oxidative stability. These results suggest that the fatty acid profile of lamb can be manipulated by the saturation level of the lipid source included in the diet. However, the replacement of saturated tallow with unsaturated soyabean oil did not result, from a human health point of view, in the desirable PUFA:SFA and n-6:n-3 ratios in muscle fat and subcutaneous lipid tissue. Therefore, the manipulation of the fatty acid content of finishing diets to achieve the desirable ratios within lamb meat, as well as the optimal inclusion level of a bioflavonoid antioxidant warrants further research.
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    ItemOpen Access
    The effect of NDF content in finishing diets on performance and meat quality of lambs
    (University of the Free State, 2016-02) De Klerk, Inalene; Einkamerer, O. B.; Hugo, A.; Greyling, J. P. C.
    English: A study was conducted to investigate the effect of incrementally increasing NDF levels of finishing diets on apparent digestibility, production performance, FA composition, oxidative stability and tenderness of lamb. The five dietary treatments were formulated to contain a similar nutrient composition, differing only in respect to the NDF content as the primary parameter. The NDF content increased from low roughage (primarily lucerne hay as fibre source) inclusion to a high roughage inclusion rate representing a dose-response trial in the following order: 12.76% (T15), 17.69% (T30), 22.53% (T45), 27.48% (T60) and 32.40% (T75) NDF/kg DM, respectively. No rumen modifiers or buffers were added to the diet. Sixty (60) South African Mutton Merino wether lambs (29.3±1.8 kg) were randomly allocated to the five dietary treatments (n=12 lambs per treatment) and further subdivided into 12 animals per replicate (n=1 lamb per replicate). After dietary adaptation of 10 days all lambs received the experimental diets for the remaining period (51 days). Live weight and feed intake were recorded on a weekly basis. A digestibility study was conducted over a 12-day period (4-day adaptation to the faecal bags followed by an 8-day collection period) where seven lambs (mean 48.11±2.94 kg live weight; total of 35 lambs) were randomly allocated to each treatment (n=7 lambs/treatment). At the end of the production study all lambs were slaughtered. Physical carcass characteristics, muscle and subcutaneous FA composition, meat oxidation (malonaldehyde content), colour stability, as well as meat tenderness were measured. The data was subjected to analysis of variance (PROC ANOVA) of the SAS program, version 9.2 (SAS, 2008). Tukey’s honest significant difference (HSD) test was used to identify significant differences (P <0.05) between treatments. From the results of the present study it is apparent that an incremental increase in the NDF content of lamb finishing diets presented a significant decrease (P <0.05) in DM, OM, NSC, GE, CP and EE digestibilities, as well as ash solubility. In addition, the significant (P <0.05) decrease in digestible OM, NSC and EE dietary content were associated with diet digestibility and resulted in a significant decrease (P <.0001) in ME content following an increased NDF incremental inclusion. A high roughage inclusion in finishing diets for lambs (T75) resulted in a significant (P <0.05) reduction in MEI, ADG, FCR, and therefore cold carcass weight and dressing percentage. Increased dietary NDF content significantly (P <0.05) increased saturated stearic acid, and significantly (P <0.05) decreased monounsaturated oleic and vaccenic acid, polyunsaturated linoleic acid, as well as total PUFA, n-6, n-6:n-3 and PUFA:SFA ratios of both lamb meat and adipose tissue. Apart from the NDF content significantly (P <0.05) affecting the monounsaturated palmitoleic acid (decreased) and polyunsaturated CLA (C18:2c9t11;n-6) content of muscle tissue, as well as total SFA (increased) and MUFA (decreased) content of only adipose tissue, the effect of dietary treatment between lamb deposit sites seem to be similar. Neutral-detergent fibre content did significantly (P <0.05) affect meat colour stability stored for 7 days at 4oC. Neutral-detergent fibre content had no effect (P >0.05) on meat tenderness. These results suggest that the FA profile of lamb can be manipulated by altering the NDF content of the finishing diet. This however did not result, from a human health point of view, in the desirable PUFA:SFA and n-6:n-3 ratios in muscle and subcutaneous lipid tissue. It is proposed that, to increase the total UFA content and its desirable effect on the mentioned ratios of lamb meat, regression equations should be used to establish the optimum response at a given NDF inclusion. Further research attempting to manipulate specific FAs (single or total) or FA ratios of lamb meat via dietary means to meet consumers’ demands need further attention.