Voi 5 (1996): 413^119. Effects of expanding on the nutritive value of wheat bran in pig diets Matti Näsi, Kirsi Partanen and Pasi Laurinen Department ofAnimal Science, P.O. Box 28, FIN-00014 University of Helsinki, Finland Nutrient digestibility and protein utilization responses in pigs to the expanding process of wheat bran were evaluated. The digestibility and nitrogen balance study was conducted with nine finishing bar- rows (live weight of 75-93 kg) using a two-period reversal design with a 2 x 2 factorial arrangement of treatments. Wheat bran, untreated or expanded with a Kahl expander at a temperature of 105- 110°C, was included at two levels of 150 or 300 g kg 1 in barley-based diet supplemented with miner- als and vitamins and fortified with lysine. The level of wheat bran in the diet had a diminishing effect on organic matter (OM), neutral detergent fibre (NDF), and hemicellulose (HC) digestibilities of the diet and tended to decrease those of crude protein (CP) and ash. Expanding of the wheat bran affected a non-significant improvement on ether extract (EE), NDF, acid detergent fibre (ADF) and HC di- gestibilities of the diet. Nutrient digestibilities of wheat bran and expanded wheat bran computed by regression were 0.64, 0.67 for OM; 0.70, 0,70 for CP; 0.47, 0.63 for EE; 0.35, 0.40 for NDF and 0.01, 0,16 for ADF, respectively. Feed values of untreated and expanded wheat bran were 11.45 and 12,08 MJ ME kg 1 DM, 7.84 and 8.02 MJ NE kg' 1DM and digestible crude protein 1 13 and 1 10 g kg' 1 DM respectively. The expanding process had no effect on nitrogen retention or protein utilization param- eters measured. Processing of wheat bran with an expander had only a slight improving effect on the nutritive value of bran in pig diets. Key words: cereal by-products, fibrous feeds, processing, digestibility, nitrogen balance ntroduction Thermal pressure conditioning or expansion of compound feeds or feed ingredients is increas- ingly used in feed mills. With the expander, it is possible to achieve higher temperatures and pres- sures compared to conventional pelleting. The advantages of a combination of expander and pellet mill are claimed to be improved pellet quality and digestibility and an overall reduc- tion of bulk density (Wettstein and Wild 1990). The beneficial effects of expanding also include elimination of antinutritional factors and im- provement of hygienic quality of feeds. In addi- tion, feed ingredients in liquid form can be used more easily in feed mixtures treated with an ex- pander. The scientific information available con- © Agricultural and Food Science in Finland Manuscript received July 1996 413 AGRICULTURAL AND FOOD SCIENCE IN FINLAND https://www.c-info.fi/en/info/?token=DA1uO06oiuisqRan.LlqtdtfhfUeMmAw-MblrCA.ORitXfZvC6ynpXeXyLXOuQBNRuGhPBFT6dJj77Go3AXAMg83fl3SI4P1zYWLnEovTXMNK7jNGpZei6rSfNUA2d7UrikS6j9Xvj-SdLLkCZ4_FACsUCKCxSIi-GFEk-MP49kiwR23edYIAYZDQZSlVtwQb-RN0khlpl6_xLTnN1Q0ltqFxjx8lDHLPZprTlSUmckl8bEFNnEs83wgV0UFwKwUMe1QMqa0O8ttG-brONHAm2XrOBxgpIEMwwFhBj9oRJafKnGjNqBle3Cfp1a1Ic0GFg4tvsps8fYgtvnkIlX0yRk6ktZYGg Näsi, M. et al. Effects of expanding on the nutritive value ofwheat bran cerning the responses of expanding to nutritive value of various feed ingredients, especially fi- brous by-products, is scarce. The improving ef- fect of expanding on nutritive valueof barley or wheat middlings in diets for growing pigs has, however, been limited (Näsi 1992, Laurinen et al. 1995, Siljander-Rasi et al. 1995). Wheat bran is available as a feed ingredient at a reasonable price. Therefore it is tempting to add it to grower feeds for pigs in order to de- crease feed costs. Wheat bran has a relatively high phytase activity which promotes its use in feed formulas for pigs in order to reduce phos- phorus excretion in faeces (Helander et al. 1994). Wheat bran has a rather high content of dietary fibre which decreases digestibily of nutrients and protein utilization. The dietary inclusion of wheat bran should be restricted to not more than 40 g kg' 1 added NDF to optimize the perform- ance of growing pigs (Cromwell et al. 1992). The main dietary fibre components of wheat bran are pentosans or arabinoxylans. The arabinoxylan content of wheat bran ranges from 206 to 262 g kg' 1 which makes the digestibility of the nutri- ents in bran low (Graham et al. 1986, Bach- Knudsen and Hansen 1991). The processing treatments of fibrous feedstuffs are carried out in order to rupture the cell wall matrix and to modify the chemical structure of the constitu- ents to render them more susceptible to enzyme degradation in the small intestine, thus improv- ing the digestibility and utilization of nutrients. It has also appeared to be an opportunity for cell wall degrading enzymes to improve the nutri- tional value of wheatbran for pigs (Inborr 1994). The objective of the current study was to in- vestigate the effects of the expanding process of wheat bran on nutrient digestibility and protein utilization in pigs fed barley based diets. Material and methods The digestibility and nitrogen balance experi- ment was conducted with nine castrated males (Landrace x Large White), with an initial weight of 74.6 (SE 2.54) kg and final weight of 92.6 (SE 2.42) kg using a two-period trial, in which the pigs were randomly allotted to the treatments. None of the pigs received the same diet twice. The experimental diets were arranged 2x2 fac- torially with two inclusion levels of wheat bran (150 and 300 g kg '), either untreated or treated with the expanding process. The expanding of wheat bran was conducted with a Kahl expand- er at a temperature of 110°C, and the pressure applied was 20 bar. The addition of steam was 50 g kg ', half of which was applied through the inlet while the other half was injected in the bar- rel. The throughput of material was 10-12 tons per hour. The diets were barley-based supple- mented with lysine (2 gkg' 1), minerals and vita- mins according to the recommendations of Salo et al. (1990). The pigs were fed twice daily ac- cording to a restricted feeding regime (2600 and 2800 g d 1). The daily ration was divided into two equal meals and mixed with water (1:1 w/v) and between meals water was offered ad libi- tum. During the whole experiment, the pigs were kept in metal metabolism cages equipped with collection trays, allowing separate collection of faeces and urine. Each period comprised of 5 days of adjustment and 5 days of total collec- tion of faeces and urine. Total faeces were col- lected daily, stored at -18°C until the end of the collection period, thawed and the composition was analysed. Urine was collected daily into 40 ml of 10 N H, S0 4 sampled, and stored at 4°C until the end of the trial when analyses of N and urea were carried out. The proximate composi- tion of the feed ingredients were analysed using AOAC (1984) methods. The neutral and acid detergent fibre were analyzed according to Ro- bertson and van Soest (1981). Two observations were excluded because of poor appetite of one pig during the first period and another pig be- cause of vomiting during the second period. The other animals completed the experiment success- fully and the average daily weight gain during the entire experiment was 720 g. No differences in palatability of the variously treated wheat bran 414 AGRICULTURAL AND FOOD SCIENCE IN FINLAND https://www.c-info.fi/en/info/?token=DA1uO06oiuisqRan.LlqtdtfhfUeMmAw-MblrCA.ORitXfZvC6ynpXeXyLXOuQBNRuGhPBFT6dJj77Go3AXAMg83fl3SI4P1zYWLnEovTXMNK7jNGpZei6rSfNUA2d7UrikS6j9Xvj-SdLLkCZ4_FACsUCKCxSIi-GFEk-MP49kiwR23edYIAYZDQZSlVtwQb-RN0khlpl6_xLTnN1Q0ltqFxjx8lDHLPZprTlSUmckl8bEFNnEs83wgV0UFwKwUMe1QMqa0O8ttG-brONHAm2XrOBxgpIEMwwFhBj9oRJafKnGjNqBle3Cfp1a1Ic0GFg4tvsps8fYgtvnkIlX0yRk6ktZYGg Vol. 5 (1996): 413-419. in the diets were observed. Refusals of the diets were negligible. The data were subjected to a least square analysis of variance (Snedecor and Cochran 1989) using the model Yjjk =p+A.+ Pj + Tk + e... where A, P and T are the effects of animal,ijk . ’ period and treatment, respectively. To calculate the digestibility coefficients of nutrients in wheat bran the data were inserted into a multiple re- gression equation Y = aXj + bX 2 , in which Yis the total amount of nutrients digested from the ratio (g/d), X, and X 2 are the amounts of nutri- ents consumed from barley and wheat bran (g/d), and a and b are the digestible fractions of nutri- ents in barley and wheat bran, respectively (Sch- neider and Flatt 1975). The metabolizable and net energy values of wheat bran were calculated according to Schiemann et al. (1972), CVB (1991) and Tuori et al. (1995). Results and discussion The chemical composition of the experimental feeds is given in Table 1. Only small differences and no systematic effects of treatment were found in the proximate composition of expand- er processed wheat bran compared with the un- treated one (Table 1). This agrees with the pre- vious results which revealed no systematic im- pact of expansion on chemical composition of barley or wheat middlings (Näsi 1992,Laurinen et al. 1995, Siljander-Rasi et al. 1995). Pressu- rized hydrothermal processing is expected to gelatinize starch and increase solubility of die- tary fibre and decrease the content of insoluble dietary fibre (Fadel et al. 1988,Ralet et al. 1990). The present treatment conditions were too mild to achieve a sufficiently strong processing effect on composition. The maximum tempera- ture reached with addition of steam (5%) during expansion was about 105-110°C. However, ma- jor effects are usually obtained at temperatures over 130-I4O°C (Hancock 1992). The chemical composition of the present wheatbrans was quite Table 1.The chemical composition of the dietary ingredi- ents (g kg' 1 ). Barley Wheat Expanded bran wheat bran Dry matter 868 873 871 Ash 24 55 53 Crude protein 115 160 157 Ether extract 32 61 60 Crude fibre 60 102 98 Nitrogen free extract 769 623 633 NDF 215 399 405 ADF 51 108 113 Hemicellulose 164 292 292 NDF = neutral detergent fibre, ADF = acid detergent fibre similar to the average values given in feed ta- bles (Tuori et al. 1995). On the other hand, de- pending on the origin and milling process, the chemical composition, especially the contents of starch and dietary fibre, may vary considerably. The average dry matter intake of the experimen- tal diets was 86 g kg ' metabolic body weight and there were no differences in the palatability of the two sources of wheat bran. The apparent total tract digestibilities of the dietary nutrients are presented in Table 2. The level of wheat bran inclusion in the diet had a significant effect on digestibility of carbohy- drates. Digestibilities of OM (PcO.Ol), NDF (P<0.01) and hemicellulose (P<0.05) were sig- nificantly decreased in diets supplemented with 300 g kg ' wheat bran compared to a lower in- clusion level. Digestibilities of ash and crude protein also tended to be lower (P