No description available.

No description available.

No description available.

No description available.

A programme of study was undertaken to assess the effect of pretreating raw soya bean and processed full fat soyabean meals with protease enzymes prior to use in liquid feed for grower and finisher pigs. A series of laboratory studies was undertaken to examine the efficacy of three microbial proteases (P2, P3 and P4) in partially hydrolysing soya protein and in reducing the levels of trypsin inhibitors in raw soyabean. Pretreatment consisted of steeping ground soyabean for 24 h at 20° C in the absence (control) or presence of 20 000 units gˉ¹ N of P2, P3 or P4. Pretreating raw soyabean (RSB) with P2, P3 and P4 significantly (P < 0.05) reduced trypsin inhibitor levels from 28.53 to 19.98, 17.17 and 18.35 (s.e.m.1.14) mg trypsin inhibited gˉ¹ soya respectively. Pretreating RSB, micronized (MIC) or autoclaved (AUT) soyabean meal with P2, P3 or P4 resulted in increases in soluble a.-amino nitrogen of 5.22, 7.08, and 6.58 (RSB), 5.11, 5.57 and 4.32 (MIC) and 3.56, 7.03 and 6.18 (s.e.d. 0.06) mg gˉ¹ soya respectively and in vitro digestibility of nitrogen of 7.6 %, 9.9 %and 6.4 % (RSB), 4.9 %, 8.3 % and 2.8 % (MIC) and 11 %, 8 % and 12.2 % (AUT) respectively compared with the appropriate controls. Feeding trials were conducted in which pretreated soya was added to a basal cereal diet. Pretreatment of RSB with P4 resulted in a significant (P < 0.05) increase in ADG of 0.08 kg pigˉ¹ dˉ¹ (s.e.d. 0.04) in grower pigs (33.5 ± 4 kg) over the 6 week duration of the trial but had no significant effect on FCR. Pretreatment of AUT with P4 did not significantly improve performance. In a feeding trial with grower/finisher pigs pretreatment of RSB with P3 resulted in significant (P < 0.05) improvements of 0.10 (s.e.d. 0.04) kg pigˉ¹ dˉ¹ in ADG and 0.476 (s.e.d. 0.19) in FCR. Pretreatment of MIC with P3 resulted in a significant reduction (P < 0.05) of 4 d (s.e.d. 1. 7) in the time taken for pigs to attain slaughter weight.

The major serine proteinase inhibitors Kunitz and Bowman-Birk-type trypsin are key anti-nutrients responsible for the low nutritional value of raw soy cake, the by product of oil expression from soybean. Traditionally, proteinase inhibitors are eliminated from soy cake through intensive heating, which is highly costly. The long term goal is to generate soybean seeds devoid of trypsin inhibitors through tissue culture and genetic modification of soybean. The RNAi technology has been selected in this study as a technique for down-regulation or silencing these two major serine trypsin inhibitors. Conserved regions, which have been identified by searching NCBI and EMBL database, were targeted for down regulation. Seed specific promoters were also isolated to drive the expression of hairpin constructs designed to down-regulate selected conserved regions of the inhibitors in soybean seeds. RNAi silencing constructs were designed for use in soybean transformation. Ultimately, a tissue culture and transformation protocol for a local soybean variety PAN 512 was established for transformation with two designed RNAi constructs. Suitability of selected promoters was tested by attaching promoters to the gus gene and evaluating specificity of seed expression after soybean transformation using the Agrobacterium tumefaciens strain EHA101. Future work will focus on further optimisation of the transformation protocol and generation of transformed plants carrying the designed silencing vectors. Copyright / Dissertation (MSc)--University of Pretoria, 2010. / Plant Science / unrestricted

No description available.