ORIGINAL SCIENTIFIC PAPER 235 Incresing Dietry Energy with Strch nd Soluble Fibre nd Reducing ADF t Different Protein Levels for Growing Rbbits Mrco TAZZOLI 1 Mrco BIROLO 1 Eirini FILIOU 1 Angel TROCINO 2 ( ) Andre ZUFFELLATO 3 Gerolmo XICCATO 1 Summry The effect of incresing dietry energy by incresing both strch (14% to 20%) nd soluble fibre (9.6% to 11.6%) nd decresing ADF content (21% to 13%) t two crude protein levels (14% nd 15%) ws ssessed on helth, growth performnce, cecl fermenttive ctivity, gut mucos trits, nd crcss nd met qulity of growing rbbits rered from 34 to 76 dys of ge. At wening, 306 rbbits were divided into six groups nd fed d libitum six diets formulted ccording to bi-fctoril rrngement with 3 (strch+soluble fibre)/adf rtio (L=1.2; M=1.8; H=2.8) x 2 protein levels. The contemporry increse of dietry strch nd soluble fibre nd the reduction of ADF linerly incresed the digestibility of dry mtter, energy nd ll nutrients, decresed feed intke nd improved feed conversion (3.65 to 2.76 in rbbits fed diets L nd H; P<0.001); it incresed morbidity (P=0.09) but did not ffect mortlity due to epizootic rbbit enteropthy; t cecum, VFA production rised (52.1 to 61.9 mmol/l) nd ph (5.90 to 5.67) nd N mmoni lowered (4.85 to 1.93 mmol/l); the villi/crypts rtio (4.42 vs. 3.81 nd 3.95 in rbbits fed diets L, M nd H) decresed in non liner mode. The decrese of the protein level did not ffect growth performnce, but nerly hlved mortlity (28.9% vs. 16.3%; P=0.01) nd incresed cecl ph (5.70 to 5.87; P=0.05). Wek effects of the dietry tretments were mesured on crcss trits nd met qulity. Key words strch, soluble fibre, insoluble fibre, protein, growing rbbits 1 Deprtment of Agronomy, Food, Nturl Resources, Animl nd Environment, University of Pdov, Agripolis, I-35020 Legnro, Pdov, Itly 2 Deprtment of Comprtive Biomedicine nd Food Science, University of Pdov, Agripolis, I-35020 Legnro, Pdov, Itly e-mil: ngel.trocino@unipd.it 3 Veronesi Veron S.p.A., I-37142, Quinto di Vlpnten, Veron, Itly Received: April 23, 2013 Accepted: June 26, 2013 ACKNOWLEDGEMENTS This study ws funded by the University of Pdov, Itly (2011 CPDA119830). Agriculture Conspectus Scientificus. Vol. 78 (2013) No. 3 (235-239)
236 Mrco TAZZOLI, Mrco BIROLO, Eirini FILIOU, Angel TROCINO, Andre ZUFFELLATO, Gerolmo XICCATO Aim The present study imed t evluting whether the increse of dietry energy obtined by contemporry increment of strch (14% to 20%) nd soluble fibre (9.6% to 11.6%) concentrtion t the expense of ADF supply (21% to 13%) nd the vrition of protein level (14% to 15%) cn ffect helth sttus, growth performnce, digestive efficiency, cecl fermenttion ctivity nd gut mucos trits, nd crcss nd met qulity in growing rbbits. Mteril nd methods A totl of 306 wened Hyplus crossbred rbbits (Hyphrm, Groupe Grimud, Roussy, Frnce) of both genders were put in individul cges (285 x 410 x 285 mm) t 34 d of ge, divided into six groups (51 rbbits ech), homogeneous in verge live weight nd vribility, nd given d libitum ccess to six experimentl pelleted diets until slughter (76 d of ge). The diets (L14, M14, H14, L15, M15 nd H15) were formulted s combintion of three (strch+soluble fibre)/adf rtios (low, L=1.2; moderte, M=1.8; high, H=2.8) combined with two crude protein levels (14% nd 15%) (Tble 1). No ntibiotics or drugs were included in the feed. Individul live weight nd feed intke were recorded three times week. Helth sttus ws controlled dily. Epizootic rbbit enteropthy (ERE) occurred soon fter one week of tril nd ll rbbits were treted with ntibiotics in wter (timulin nd colistin) from 48 to 57 dys of ge. At 42 d of ge, 36 rbbits (6 per diet) out of the 306 initil rbbits were slughtered to smple cecl content nd gut mucos (jejunum nd ileum). The digestibility coefficients nd digestible energy (DE) concentrtion of the experimentl diets were mesured in vivo on 72 rbbits mong those on tril (12 nimls per diet) from 49 to 52 dys of ge ccording to Perez et l. (1995). Diets, feces, cecl contents nd gut mucos were nlyzed ccording to the methods detiled by Trocino et l. (2013). The soluble fibre content ws obtined by subtrcting NDF fter correction for sh nd protein from TDF (Trocino et l., 2013b). At 76 d of ge, 120 rbbits were selected (20 nimls per diet) representtive in terms of verge weight nd vribility nd slughtered. After 24 h of cooling t 4 C, the crcsses were dissected ccording to the interntionl scientific protocols (Blsco et l., 1993). The dt of performnce, digestibility coefficients, intestinl mucos trits nd cecl fermenttion ctivity were submitted to ANOVA with (strch+soluble fibre)/adf rtio, protein level nd their interction s min fctors nd using the GLM procedure of SAS (SAS Institute, Cry, NC, USA). Orthogonl contrsts were used to test the liner nd qudrtic response to the increse of the (strch+soluble fibre)/adf rtio. Mortlity, morbidity, nd snitry risk (i.e., mortlity+morbidity) were nlysed by the CATMOD procedure of SAS. Results nd discussion Despite the occurrence of ERE which severely ffected rbbits during the first weeks on tril (verge mortlity: 22.6%), nimls recovered well thnks to the ntibiotic tretment nd showed stisfying performnce for the genetic type used: rbbits weighed on verge 2831 g t 76 dys of ge, with dily weight gin of 44.1 g/d, feed intke of 141 g/d nd feed conversion of 3.21 in the whole period of growth. As the interctions were not significnt, the results re presented nd discussed ccording to the min fctors. Effect of (strch+soluble fibre)/adf rtio When the rtio incresed from 1.2 to 1.8 to 2.8, the digestibility of energy nd ll nutrients linerly rised (Tble 2), especilly fibre frctions with the exception of soluble fibre (85-90%); therefore the DE concentrtion incresed from 9.7 to 11.0 to 12.2 MJ/kg (Tble 1); growth rte did not chnge (Tble 3) but feed intke linerly decresed (P<0.001) both in the first nd second period of the Tble 1. Ingredients (%), chemicl composition nd nutritive vlue of the experimentl diets Diet L14 M14 H14 L15 M15 H15 Ingredients Dehydrted lflf mel 16% CP 37.00 18.50 0.00 36.00 18.00 0.00 Whet brn 21.00 18.50 16.00 30.00 25.00 20.00 Brley 16.00 24.50 33.00 10.50 20.25 30.00 Dried beet pulp 17.48 25.39 33.30 13.50 21.75 30.00 Soyben mel 50% CP 4.00 7.75 11.50 6.00 10.00 14.00 Sunflower oil 1.00 1.50 2.00 1.00 1.50 2.00 Other ingredients 3.52 3.86 4.20 3.00 3.50 4.00 Chemicl composition Dry mtter, % 89.3 89.1 88.9 89.6 88.9 88.4 Crude protein, % 14.3 14.3 14.2 14.8 15.2 15.1 Ether extrct, % 3.39 3.65 4.01 3.81 3.74 4.17 TDF, % 42.7 40.2 37.3 43.7 40.3 35.9 NDF, % 34.7 30.5 26.4 36.3 31.3 26.2 ADF, % 18.4 14.9 11.4 18.9 15.0 11.2 ADL, % 2.7 1.7 0.8 2.9 1.8 0.8 Soluble fibre, % 10.0 11.1 12.0 9.1 10.0 11.2 Strch, % 14.0 17.8 21.2 12.4 16.2 19.6 Digestible energy (DE), MJ/kg 9.8 11.2 12.2 9.6 10.8 12.3 Digestible protein/de, g/mj 10.5 9.1 8.6 11.4 10.5 9.4 Molsses, limestone, diclcium phosphte, slt, L-lysine, DL-methionine, DL-threonine, vitmin-minerl premix.
Incresing Dietry Energy with Strch nd Soluble Fibre nd Reducing ADF t Different Protein Levels for Growing Rbbits 237 Tble 2. Digestibility coefficients (%) (Strch+soluble fibre)/adf rtio Protein level RSD Rbbits, n 23 21 22 33 33 Dry mtter 58.2 66.4 75.6 <0.001 0.37 67.1 66.4 0.13 1.86 Crude protein 72.5 73.0 75.4 <0.001 0.08 72.5 74.8 <0.001 2.05 Ether extrct 79.2 81.2 85.4 <0.001 <0.01 81.4 82.4 <0.01 2.32 TDF 37.4 49.6 61.6 <0.001 0.92 50.2 50.0 0.14 3.21 NDF 27.0 37.6 51.0 <0.001 0.14 39.4 37.7 0.07 3.68 ADF 17.8 27.1 40.4 <0.001 0.09 28.3 28.6 0.83 4.41 Soluble fibre 85.5 89.4 88.7 0.12 0.20 85.0 90.8 <0.001 6.61 Strch 97.5 98.0 98.6 <0.001 0.47 98.1 98.0 0.03 0.23 Gross energy 59.0 66.6 75.2 <0.001 0.33 67.5 66.4 0.02 1.99 Residul stndrd devition. b Liner component of vrince. c Qudrtic component of vrince. Tble 3. Performnce nd helth sttus from 34 d until 76 d of ge (Strch+soluble fibre)/adf rtio Protein level RSD Rbbits, n 71 65 66 108 94 Live weight, g At 34 d 974 987 972 0.92 0.34 986 970 0.27 99 At 55 d 2041 2034 1985 0.13 0.53 2036 2004 0.28 212 At 76 d 2826 2862 2804 0.63 0.23 2829 2832 0.93 255 First period (34-55 d) Dily weight gin, g/d 50.5 50.2 47.9 0.13 0.53 50.3 48.7 0.28 10.1 Feed intke, g/d 145 128 107 <0.001 0.54 127 126 0.76 19 Feed conversion 2.89 2.69 2.38 <0.001 0.60 2.56 2.75 0.07 0.72 Second period (55-76 d) Dily weight gin, g/d 37.4 39.4 39.0 0.19 0.26 37.8 39.5 0.10 7.2 Feed intke, g/d 175 159 132 <0.001 0.04 152 158 0.05 20 Feed conversion 4.82 4.12 3.44 <0.001 0.90 4.16 4.09 0.51 0.79 Whole tril (34-76 d) Dily weight gin, g/d 44.0 44.8 43.4 0.63 0.23 44.0 44.1 0.93 6.1 Feed intke, g/d 160 144 120 <0.001 0.12 140 142 0.33 17 Feed conversion 3.65 3.22 2.76 <0.001 0.65 3.19 3.23 0.28 0.25 Helth sttus d Mortlity, % 21.1 23.3 23.3 0.79 16.3 28.9 0.01 Morbidity, % 17.8 20.0 31.1 0.09 25.9 20.0 0.32 Snitry risk e, % 38.9 43.3 54.4 0.10 42.2 48.9 0.26 Residul stndrd devition. b Liner component of vrince. c Qudrtic component of vrince. d Probbility of χ 2 -test. e Mortlity + morbidity. tril nd, s consequence, feed conversion improved (P<0.001). The improvement of feed conversion in diets with higher DE obtined incresing strch nd soluble fibre in replcement of insoluble fibre ws expected (Bls nd Gidenne, 2010; Trocino et l., 2013b), wheres the consequences on helth sttus were less obvious. A higher morbidity ws observed in rbbits fed the highest (strch+soluble fibre)/adf rtio (from 17.8 nd 20.0% to 31.1%; P=0.09), but mortlity ws not modified (Tble 3). As reviewed by Bls nd Gidenne (2010), helth of rbbits my impir when strch is incresed t the expense of insoluble fibre, while positive effects my be recorded when soluble fibre replces insoluble fibre, especilly in presence of ERE (Xiccto et l., 2006; Gómez-Conde et l., 2007; Mrtínez-Vllespín et l., 2011). In the present tril, the increse of soluble fibre likely counterblnced the negtive effects on helth of incresing strch nd decresing ADF, therefore permitting to use high energy diets without consequences. With the increse of the (strch+soluble fibre)/adf rtio, VFA production t cecum linerly incresed nd ph vlue nd N-mmoni decresed; the proportion of cetic cid tended to rise nd tht of propionic cid to decrese (Tble 4). The mjor vilbility of fermentble crbohydrtes, both s strch nd soluble fibre, promoted cecl VFA production nd reduced N-mmoni levels (Jehl nd Gidenne, 1996; Bls nd Gidenne, 2010; Trocino et l., 2013b), nd likely modified cecl microflor, in rbbits fed higher dietry (strch+soluble fibre)/adf rtio. However, s demonstrted by the higher digestibility, lso insoluble fibre my hve been more susceptible to microflor fermenttion in the cecum, becuse of the lower lignifiction nd complexity of the cell wlls or different hemicellulosic constituents (Crbño et l., 2001; Grcí et l., 2002). Previous studies correlted improvements in helth sttus with better brrier function of the intestinl mucos in rbbits fed higher levels of the most soluble fibre frctions (from 7 to 12%) t the
238 Mrco TAZZOLI, Mrco BIROLO, Eirini FILIOU, Angel TROCINO, Andre ZUFFELLATO, Gerolmo XICCATO Tble 4. Cecl content nd intestinl mucos trits (Strch+soluble fibre)/adf rtio Protein level RSD Cecl content ph 5.90 5.78 5.67 0.03 0.93 5.87 5.70 0.05 0.24 N-NH3, mmol/l 4.85 2.59 1.93 <0.01 0.32 2.67 3.58 0.24 2.23 Totl VFA, mmol/l 52.1 61.4 61.9 0.03 0.24 56.3 60.6 0.23 10.5 C2, % mol. 81.8 82.3 84.6 0.07 0.45 82.9 82.8 0.99 3.63 C3, % mol. 5.19 4.52 4.36 0.09 0.54 4.95 4.44 0.20 1.15 C4, % mol. 12.5 12.7 10.5 0.18 0.32 11.6 12.2 0.65 3.51 C5, % mol. 0.57 0.55 0.56 0.87 0.85 0.57 0.55 0.81 0.21 C3/C4 rtio 0.45 0.37 0.49 0.66 0.20 0.44 0.43 0.85 0.21 Jejunum mucos Villi height d, μm 839 733 751 <0.01 0.01 780 768 0.58 64 Crypts depth, μm 192 194 192 0.99 0.69 188 197 0.14 19 Villi/crypts 4.42 3.81 3.95 0.02 0.03 4.19 3.92 0.10 0.47 Ileum mucos Villi height, μm 601 617 660 0.26 0.76 639 612 0.51 125 Crypts depth, μm 148 159 155 0.33 0.23 152 155 0.58 17 Villi/crypts 4.09 3.97 4.27 0.63 0.52 4.24 3.97 0.38 0.91 Residul stndrd devition. b Liner component of vrince. c Qudrtic component of vrince. d Villi height: 867, 758, 715, 811, 706 nd 786 μm in rbbits fed diets L14, M14, H14, L15, M15, H15; probbility of R x P interction = 0.03. Tble 5. Results t commercil slughter nd crcss qulity (Strch+soluble fibre)/adf rtio Protein level RSD Slughter weight (SW) d, g 2756 2788 2748 0.87 0.39 2765 2763 0.96 213 Gut incidence e, %SW 18.4 18.5 18.6 0.59 0.87 18.6 18.4 0.67 1.53 Chilled crcss (CC), g 1695 1703 1682 0.68 0.60 1691 1694 0.90 142 Dressing out, %SW 61.5 61.1 61.2 0.37 0.45 61.2 61.3 0.58 1.63 Reference crcss (RC) f, g 1429 1435 1417 0.69 0.64 1426 1428 0.92 127 Dissectible ft, %RC 3.16 3.35 3.33 0.44 0.61 3.27 3.29 0.94 1.01 Hind legs, %RC 33.0 32.7 32.7 0.44 0.55 32.9 32.6 0.31 1.00 Hind leg muscle/bone rtio 6.07 6.60 6.13 0.76 0.01 6.15 6.36 0.25 0.61 Residul stndrd devition. b Liner component of vrince. c Qudrtic component of vrince. d Live weight immeditely before slughter; e Incidence of the full gstro-intestinl trct. f Chilled crcss without hed, liver, thorcic orgns nd kidneys. expense of insoluble fibre (Álvrez et l., 2007; Gómez-Conde et l., 2007). However, this ws not our cse, since villi height nd villi/crypt rtio of jejunum decresed, which should be rther considered negtively (Tble 4). On the other hnd, the ileum mucos morphology ws not ffected by dietry tretments, s lso found in other studies of ours (Xiccto et l., 2008; Trocino et l., 2010, 2011). The effect of the experimentl fctors ws hrdly mesurble on slughter results (Tble 5), prt from significnt nd qudrtic chnge of the hind leg muscle to bone rtio (P=0.01) which indictes tht diets with n intermedite (strch+soluble fibre)/adf rtio re probbly the most equilibrte nd cpble of stimulting the highest musculr growth of rbbits. Effect of crude protein level The decrese of dietry crude protein (CP) from 15% to 14% s-fed lowered CP digestibility (Tble 2), likely becuse of the higher protein rte derived from lflf mel rther thn soyben mel; besides, lower digestibility vlues were recorded for soluble fibre. Quite surprisingly, limited decrement of dietry CP nerly hlved the mortlity rte (16.3% vs. 28.9%, P=0.01). On the other hnd, it did not ffect productive performnce in the whole period, even if feed conversion tended to lower during the first period of tril nd growth nd feed intke decresed during the second period (Tble 3). In fct, if 15% s-fed of dietry CP usully covers protein requirements for growing rbbits (de Bls nd Mteos, 2010), the supply of min limiting mino cids (lysine, methionine nd threonine) my permit reduction until or below 14% (Trocino et l., 2000; Grcí-Plomres et l., 2006). A higher dietry protein lowered cecl ph (5.87 to 5.70) (Tble 4), wheres ll microbil popultions benefit from high protein content in the cecum for their development nd prolifertion. However, some pthogenic strins of E. coli nd Clostridi spp. my be t n dvntge when there is n excess of protein (Grcí-Plomres et l., 2006; Chmorro et l., 2007; Crbño et l., 2009). In fct, Mrtínez-Vllespín et l. (2011) found tht reducing dietry protein from 17.5 to 14.5% lowered mortlity ( 19.9 percentge points) of rbbits ffected by ERE during post-wening period (28-49 d of ge), s we observed in the present tril.
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