Dietary effects of sclerocarya birrea caffra nut meal in growing-fattening male dorper sheep
Date
2018
Authors
Malebana, Ingrid Marumo Mokgadi
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Abstract
In Sub-Saharan Africa, the cost of producing livestock products is increasing due to the use of imported soyabean meal (SBM) as a dietary protein source in feeds. Reliance on the costly SBM can be reduced by developing alternative dietary protein sources for feeds. Seeds from indigenous trees are potential sources of nutrients including protein. In a series of experiments, the potential of Marula nut meal (MNM) to substitute SBM in lamb fattening diets was evaluated. Chapter 3 characterised and compared the nutrient and anti-nutrient composition of two MNMs (MNM1: produced using hydraulic filter press, MNM2: produced using cold press) and SBM.
The MNMs’crude protein (CP) content, which ranged from 33% (MNM1) to 39% (MNM2), was lower than that of SBM (51%). The MNMs’ essential amino acid content ranged from 40 to 70% compared to that of SBM. The gross energy (GE), ether extract (EE) and total monounsaturated fatty acid (TMUFA) content of the MNMs were significantly higher (P<0.05) compared to that of SBM. The MNMs had a higher (P < 0.05) phosphorus and magnesium content than SBM. Compared to SBM, MNM2 had a higher oxalate and phytate-phosphate content, but a lower saponin and tannin content (P<0.05). MNM2 was used in the in vivo study (chapter 4) as a dietary protein source, due to it having a higher CP content and in vitro digestibility compared to MNM1.
Chapter 4 interrogated the effects of MNM2: denoted as MNM, as a dietary protein source on growth performance, feed efficiency and health of Dorper lambs. Dietary MNM neither affected the growth, feed efficiency nor the liver and kidney function of the lambs. In chapter 5 the effect of dietary MNM2: denoted as MNM, due to its higher CP content than MNM1, was evaluated on meat quality. Substituting SBM with MNM at 0, 50 and 75% resulted in meat with high CP (P<0.05) but low EE content while substituting at 25 and 100% resulted in meat with high EE (P<0.05) but low CP content. Dietary MNM significantly increased the total saturated and TMUFA concentration in the meat. Complete substitution of SBM with MNM yielded fatty meat rich in oleic acid, manganese and selenium (P <0.05).
The MNM can replace SBM in lamb fattening diets without compromising growth, feed efficiency, liver and kidney function and meat quality. However, substitution of SBM with MNM at high inclusion levels results in increased lipid content in the meat.
Description
A thesis submitted to the Faculty of Health Sciences, University of the Witwatersrand, School of Physiology, in fulfilment of the requirements for the degree of Doctor of Philosophy.
Johannesburg, 2018.