Morula kernel cake as a dietary component in complete diets for Tswana sheep

Abstract

Lack of locally produced high quality feed ingredients for livestock, especially to supply protein is an impediment to increased productivity in Botswana. Driven by the need to fill this gap, a series of experiments were conducted to evaluate the nutritive value and utilisation of Morula (Sclerocarya birrea) Kernel Cake (MKC) in diets of sheep. Therefore, this thesis reports results from those studies and the first study chemically characterised MKC in comparison to Sunflower Seed Cake (SSC). MKC was found to be a rich source of gross energy, protein, phosphorus and magnesium. Lysine was the limiting amino acid in MKC when compared to SSC. However, cysteine and tyrosine were greater in MKC than in SSC. On the other hand, summation of essential amino acids values resulted in a similar value between the two seed cakes (MKC and SSC). Dry matter in situ degradability of MKC indicated that it is highly degradable in the rumen compared to the dry matter of SSC. Nevertheless, the potential degradabilities of CP were similar for both SSC and MKC. But the protein of MKC contained higher bypass protein than that of SSC. The major fatty acids in MKC were found to be palmitic acid, stearic acid and oleic acid. Two growth trials and nitrogen balance studies were conducted to understand the impact of graded inclusion of MKC in lamb’s complete diets. The trials indicated that MKC was a good source of RDP but also RUP to the host animal that elicited desired growth performance. Additionally, the inclusion of 12% MKC was noted to give the best results as it was not harmful to the lambs and promoted improved growth and normal blood metabolites. A follow-up fattening trial was done using the best diet from graded level study. The diet with 12% MKC inclusion level was compared with other two conventional protein supplementary sources used in complete diets of lambs (SSC and Lucerne (Medicago sativa)). SSC and Lucerne are imported from abroad at high cost to the country and subsequently to the livestock farmers. The growth performance of fattened lambs across the three protein sources treatments was similar. However, nitrogen retention was better in Lucerne based diet and lowest in sunflower seed cake-based diet. In addition, the Longissimus dorsi muscle from lambs in MKC treatment was rich in oleic acid and the cooked meat steaks tended to have numerically better sensory attributes than in the other two treatments. MKC diet was found to have higher gross margin analysis value than Lucerne diet (commercial diet). Therefore, MKC is suited for use in diets of ruminants to supplement both energy and protein in areas where it is locally available. The inclusion level of MKC in total diet dry matter should not exceed 12% to iii

minimise amount of ether extract in the total diet. A study on effect of Morula oil on rumen fermentation or microbiota should be conducted or a study on in situ ruminal degradation of diets used in the graded MKC inclusion in lamb diets.