ผลของแหล่งอาหารแป้ง digestibility เจริญเติบโต และลักษณะคุณภาพของสุกรที่เจริญเติบโตไฮไลท์•ข้าวบาร์เลย์ ข้าว ข้าวโพด และถั่วเป็นแหล่งของแป้งได้ทดสอบในสุกร•รูปแบบของลำไส้การย่อยอาหารของแป้งแหล่งอาจมีผลต่อลักษณะการเจริญเติบโตและลึก backfat•ลักษณะพิเศษที่หายากถูกตรวจสอบคุณภาพเนื้อสัตว์บทคัดย่อBarley, rice, maize and peas as starch sources were tested to study if differences in glycemic index may affect feed utilization, productive performances and quality traits for growing pigs. Four experimental diets were formulated to include 420 g starch/kg, provided by barley, barley/broken rice, barley/maize or barley/peas combinations (diets coded B, R, M and P, respectively). A 45% of total starch from diets R, M and P was provided by broken rice, maize or peas. The in vitro characterization of feeds showed that the rapidly digestible starch fraction was highest for R (P<0.001) and no differences were recorded among the other diets, whereas the slowly digestible fraction was higher for B and M than for R (P<0.01) and that higher than for P (P<0.01). Then the resistant starch fraction was higher for P than for B and M (P<0.001) and those higher than for R (P<0.001). The rate of glucose release was fastest with R (P<0.001), and estimations of glycemic index were highest for R and lowest for P (P<0.001). For the in vivo trial, a total of 72 Duroc×(Landrace×Large White) crossbred gilts, with 63.0±4.55 kg body weight (116±3 days of age) was used. Statistical trends (P model<0.10) were observed for ADG and FCR; gilts fed diet P grew faster (P<0.05) and had a lower FCR (P<0.05) than those fed diet R. The apparent organic matter digestibility for diets R and P was lower than for diet B (P<0.001) but higher than for diet M (P<0.01). Similarly, the apparent crude protein digestibility was higher with diet R than with diet M (P<0.01). Gilts consumed from 32% to 40% of available feed within the first 2 h after offering, then the rate dropped from 2 to 4 h (P<0.05) and was virtually nil from 10 to 12 h for all diets. There was a limited influence of diet on carcass and meat characteristics but the intramuscular fat from pigs fed B showed higher (P<0.001) total saturated fatty acids and lower (P<0.001) total monounsaturated fatty acid contents than that from pigs fed M. It can be concluded that the pattern of gut digestion of the starch source may affect backfat thickness and growth performance of gilts, with scant effect on meat quality.1. บทนำแป้งเป็นแหล่งพลังงานหลักในอาหารสำหรับสุกรในระบบการผลิตแบบเร่งรัด ถึงถึง 400 – 500 g/kg น้ำหนักแห้งอาหาร ดี ธัญพืชธัญพืชเป็นแหล่งอาหารสำคัญของแป้ง การหาค่าเฉลี่ย 60 – 80% ของอาหารทั้งหมด แต่ส่วนผสมอื่น ๆ เช่นกิน ถือเป็นแหล่งของแป้ง (ฮูเวอร์และโจว 2003) มันเป็นที่ยอมรับกันว่า แป้งเกือบหมดย่อยในลำไส้หมู (Bach Knudsen, 2011 ชิก Noblet, 1993) อย่างไรก็ตาม ปัจจัยตามกำเนิดโบตานิค เช่นสัดส่วนของ amylase และ amylopectin โครงสร้างโมเลกุล และ crystallinity ขนาดอนุภาค และโต้ตอบกับคอมโพเนนต์ตัวดึงข้อมูล รวมทั้งผลิตเอนไซม์ในระบบของสัตว์ย่อยสลายหรือแปรรูปธัญพืช อาจมีผลต่ออัตราการใช้ประโยชน์แป้ง (Bach Knudsen, 2011 ฮูเวอร์ และ โจว 2003 และเลห์แมน และ โรบิน 2007) ได้Starches have been classified by Englyst et al. (1992) on the basis of the rate and extent of their enzymatic digestion as rapidly digestible starch (RDS), slowly digestible starch (SDS) and starch that is not digested by α–amylase and brush-border enzymes in the small intestine (resistant starch, RS). It is assumed that differences in proportions of these fractions affect the postprandial glucose availability and insulin blood concentration (van der Meulen et al., 1997 and van Kempen et al., 2010) and therefore the energy utilization and protein and lipid metabolism (Drew et al., 2012 and van den Born et al., 2007). Consequently, the nature of the starch source may influence growth traits, as well as carcass and meat fatness, and such effect would depend on the rate glucose is released from its digestion, i.e., the changes in blood glucose concentration (glycemic index, GI; Giuberti et al., 2012a, Jenkins et al., 2002 and van Kempen et al., 2010). The GI is also related with the feeding pattern, since high postprandial glucose level induces long-lasting effects on satiety ( Bach Knudsen, 2011 and Menoyo et al., 2011).Maize and barley are widely used as starch sources in pig diets, but the inclusion of legumes such as peas or beans as protein source also implies an input of starch. Rice has also been considered as feed for pigs, as broken rice (Mateos et al., 2007), although restricted to piglets because of competence with human diets. Maize starch digestion is partially protected by the endosperm protein matrix (Svihus et al., 2005), whereas the small particle size of rice allows for a fast digestion (Tester et al., 2004). Regarding peas, the crystal structure of its starch, high amylose proportion and cell structures enclosing starch granules give it a certain extent of resistance to amylase digestion (Hoover and Zhou, 2003 and Sun et al., 2006). Thus, the estimated GI ranked starch sources as: rice>barley>maize>peas (Drew et al., 2012, Giuberti et al., 2012b, Menoyo et al., 2011 and van der Meulen et al., 1997).The objective of this work was to evaluate whether the GI of the starch source may affect growth and fattening of growing-finishing pigs. Thus, four sources of starch (barley, broken rice, maize and peas) differing in their digestion rates were characterised in vitro, and their GIs were estimated. Then the four sources were included in diets for growing pigs and their productive performances, diet digestibility and quality traits were tested.2. Materials and methods2.1. Experimental feedsFour experimental diets were formulated to include 420 g starch/kg, provided by barley, barley/broken rice, barley/maize or barley/pea combinations (diets coded B, R, M and P, respectively). In order to formulate homogeneous diets, a fixed amount of a common starch source (490 g/kg), such as barley, was included. Therefore, a proportion of 43–45% of total starch from diets M, R and P was provided by maize (614 g starch/kg), broken rice (698 g starch/kg) or peas (472 g starch/kg), whereas all starch in diet B came from barley (511 g starch/kg). In diet P, peas partly substituted barley but also soybean meal as protein source (crude protein content of peas 204 g/kg). In diet R, soybean hulls were included to maintain a similar fibre level among diets. Diets were formulated to be isonutritive to meet or exceed the levels recommended by FEDNA (2013) for growing pigs. The ingredient composition and nutrient content of the experimental diets are shown in Table 1.Table 1. Ingredient and chemical composition of the experimental diets.Diet BarleyBroken riceMaizePeasIngredients (g/kg as-fed basis) Barley grain 780 490 490 490 Broken rice – 230 – – Maize grain – – 270 – Peas – – – 400 Soybean meal (440 g crude protein/kg) 172 198 198 60 Blended fata 20 19 10 19 Soybean hulls – 33.5 3 4.3 Calcium carbonate 10 10 10 10 Dicalcium phosphate 8 10.5 9 8 Sodium chloride 4 4 4 4 l-Lysine 1.5 0.8 1.5 – dl-Methionine 0.5 0.2 0.5 0.7 Vitamin and mineral premixb 4 4 4 4 Calculated compositionc (g/kg as-fed basis) Metabolisable energy (Kcal/kg) 3093 3141 3118 3111 Starch 403 426 426 426 Lysine 9.0 9.4 9.2 9.6 Methionine 3.0 3.0 3.1 2.9 Threonine 5.9 6.5 6.1 6.1 Tryptophan 2.0 2.1 1.9 1.7 Calcium 6.7 7.5 6.9 6.7 Digestible phosphorous 2.4 2.5 2.4 2.6 Analysed composition (g/kg as-fed basis) Dry matter 902 897 901 900 Organic matter 934 940 940 938 Crude protein 173 167 172 180 Neutral detergent fiber 158 151 150 151 Ether extract 39 36 39 38 Fatty acids (g/100 g total fatty acids) C14:0 1.6 1.8 1.1 1.5 C16:0 31.5 31.7 27.4 28.3 C18:0 10.3 11.7 7.6 10.5 C18:1 26.0 26.3 25.8 29.2 C18:2 16.8 13.2 21.5 17.3 C18:3 1.3 1.4 1.7 1.4 aMixture of fat from cattle and pig.bProviding (per kg of diet): vitamin A (retinyl acetate): 6500 IU; vitamin D3 (cholecalciferol): 2000 IU; vitamin E (all-rac-α-tocopheryl acetate): 6 IU; vitamin B2 (riboflavin): 4 mg; vitamin B6 (pyridoxine): 1.5 mg; vitamin B12 (cyanocobalamin): 16 mg; niacin: 18 mg; d-pantothenic acid (dl-calcium pantothenate): 9 mg; choline (choline chloride): 75 mg; Zn (zinc oxide): 110 mg; Mn (manganese oxide): 16.6 mg; Fe (ferrous sulphate): 99.9 mg; Cu (copper sulfate): 12 mg; Co (cobalt sulfate): 0.48 mg; Se (sodium selenite): 0.21 mg; I (calcium iodate): 0.99 mg; 4920 6-Phytase: 499.8 FTU; E 4818 Endo-1,4 beta xylanase: 10 IU.cEstimated according to FEDNA (2010).Table options2.2. in vitro characterization of starchTo characterize the in vitro digestion pattern of starch, three different samples of each feed taken at the first, medium and last part of the in vivo experiment (see Section 2.3) were analysed in duplicates following the procedure described by Englyst et al. (1992) with the modifications proposed by Giuberti et al. (2012b). Pepsin (SIGMA P-7000, Sigma–Aldrich, Steinheim, Germany), pancreatin (SIGMA P-1750Sigma-Aldrich, Steinheim, Germany), amyloglucosidase (E-AMGDF100, Megazyme, Bray, Ireland) and invertase (SIGMA I-4504, Sigma–Aldrich, Steinheim, Germany) were used for enzymatic digestion. Samples were incubated at 39 °C for 0, 20, 60, 120 and 240 min, and released glucose was determined using a glucose oxidase kit (GOPODK-GLUC 07/11, Megazyme, Bray, Ireland) and reading at 510 nm wavelength. Results were expressed as glucose released per min or as proportion of total starch content that was determined enzymatically from samples ground to 0.5 mm using a commercial kit (Total Starch Assay Kit K
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