Effect of soybean variety and processing on growth performance of young pigs. Maria Palacios. 1. , Robert A. Easter. 1. , Theodore Hymowitz. 2. , Kevin T.
Effect of soybean variety and processing on growth performance of young pigs Maria Palacios1, Robert A. Easter1, Theodore Hymowitz2, Kevin T. Soltwedel1 and James E. Pettigrew1 1
Department of Animal Sciences; 2 Department of Crop Sciences University of Illinois at Urbana – Champaign Background The soybean is known as an excellent source of protein when formulating diets for swine. However, this potential can be achieved only if certain quantity of heat is applied. Osborne and Mendel (1917) were the first to report that raw soybeans had a growth-depressing effect in rats. Generally, these heat labile factors are protease inhibitors, lectins, goigotrens and antivitamins. The most common way of eliminating these factors is by heating or “toasting” the soybeans in a processing plant, being sure that temperature, duration of the heating, particle size and moisture are controlled. Another way to inactivate these factors is by dry extrusion (without steam). It is well known that antinutritional factors present in raw soybeans can cause inhibition in growth, decreased feed efficiency, goiterogenic responses, pancreatic hypertrophy, hypoglycemia and liver damage in non ruminants animals depending upon species, age, size, sex, state of health and plane of nutrition. Liener (2000) defines protease inhibitors of soybeans as proteins that can be categorized as those that have a molecular weight of about 20,000 daltons and a specificity directed primarily against trypsin, known as the Kunitz trypsin inhibitor (Kunitz, 1945); and those that have a molecular weight between 6,000 to 10,000 daltons and are capable of inhibiting chymotrypsin as well as trypsin at independent binding sites, referred as the Bowman-Birk trypsin inhibitor (Bowman, 1944; Birk 1961). Lectins are glycoproteins that have the ability to bind to carbohydrate–containing molecules on the epithelial cells of the intestinal mucosa, in which the extent of this binding determines its toxicity. They are also called hemaglutinnins, based on their ability to agglutinate red blood cells (van Heugten, 2001). Schulze et al. (1995) conducted a study to investigate the metabolic flow of purified soy lectin incorporated in diets and their effect on nitrogen passing the terminal ileum. Isotopic nitrogen analysis of the ileal digesta collected in this manner revealed an increased loss of endogenous nitrogen, which was attributed to increased secretion of protein, resulted from damaged caused by lectin on the intestinal mucosa. Performance of pigs fed raw Kunitz free soybeans is adversely affected, in the nursery and the grower stages. Growth reductions of 44% and 38% were observed in pigs fed raw Kunitz free soybeans, compared to a soybean meal diet (Stickler, 1992). This research suggested that raw soybeans free of the Kunitz trypsin inhibitor still have others antinutritional factors that affect growth in pigs. Douglas et al. (1999), conducting a study in male chicks from 8
to 17 days of age, suggested that the nutritional value of raw lectin free soybeans is greater than raw conventional soybeans but is less than raw Kunitz free soybeans and soybean meal, suggesting that the trypsin inhibitor is a greater antinutritional factor than lectins. The objective of this study was to evaluate the efficacy by which two different genetically modified soybeans improve growth performance in young pigs. The varieties tested were: Williams 82 (WM), a commercial variety; Isoline L90-8047, a lectin free variety (LF) and Isoline X97-0101, a lectin free and Kunitz trypsin inhibitor free variety (LFKF). Materials and Methods One hundred and forty gilts and barrows with an average initial weight of 13.89 kg were randomly assigned to one of the following dietary treatments for a period of 28 days. Each variety of soybean was fed as raw (R) or as dry extruded (E) soybeans in a corn soybean diet. Commercially available heated, solvent-extracted dehulled soybean meal (SBM) was included in a corn soybean meal diet as the positive control. A total of seven dietary treatments formulated to 1.01% lysine and 3600 kcal DE/kg were used in this study (Table 1): 1.SBM, 2.WM–E, 3.LF–E, 4.LFKF–E, 5.WM–R, 6.LF–R and 7.LFKF–R. Pigs were housed in a mechanically ventilated grower facility at the University of Illinois Swine Research Center in partially slatted floors. Feed and water were available ad libitum. Individual pig weights and pen feed intakes were recorded weekly. The study was conducted as a Randomized Complete Block Design with 7 treatments, 5 blocks/treatment and 4 pigs / pen (2 gilts and 2 barrows). Results and Discussion The overall daily weight gain (kg/pig), overall daily feed intake (kg/pig) and overall gain: feed ratio (g: kg) are presented in Table 2, Table 3 and Table 4 respectively. Performance was similar (P>0.05) among pigs fed the SBM and the extruded soybean diets but was poorer (P
