Evaluation Of Degradability Of The Steam Treated Rice Straw In Vitro And Its Effects On Digestibility, Growth And Meat Quality Of Goats

Feed shortage is a burning issue hindering the development of livestock production, there is a wide gap between the available feedstuffs and requirements of farm animals. The unavailability of good quality forages during seasonal dry periods make this situation more difficult. However, it is generally realized that lignocellulosic materials such as rice straw represent an underutilized renewable resource and abundantly available all over the world. However, the low protein and digestibility are the hindrances in utilization of these low quality crop residues as a feed. Numerous attempts had been applied to modify such recycled wastes, using different methods to enrich its nutritional values to before being incorporated in animal feeds. Since most of the in vitro experiments on steam treatment have been carried out with different pressure and time, and demonstrated changes in composition and degradability of the straw. Considering the importance of above mentioned fact, a series of in vitro and in vivo experiments were conducted to investigate the optimal steam treatment conditions and its effects on digestibility, growth, rumen morphology, oxidative stability and meat quality of goats.In vitro trail 1. The experiment was conducted to evaluate the effects of steam treatment on composition and in vitro degradability of rice straw. The samples, UTRS (untreated rice straw), STRS-Ⅰ (rice straw exposed to 15.5 kgf/cm2 steam pressure for 90 sec) and STRS-Ⅱ (rice straw exposed to 15.5 kgf/cm2 steam pressure for 120 sec) were prepared. The results revealed that the crude protein (CP), ether extract (EE) and acid detergent lignin (ADL) contents of rice straw were improved after treatment with steam explosion in a time dependent manner (P<0.05). The neutral detergent fiber (NDF), acid detergent fiber (ADF) and organic matter (OM) were higher, while dry matter (DM) and ash contents were lower (P<0.05) in STRS-Ⅰ as compared to UTRS and STRS-Ⅱ groups. Furthermore, STRS-Ⅱ group showed higher concentrations of propionate, acetate, butyrate, and total VFA (P<0.05). While, UTRS group exhibited higher concentration of iso-butyrate and zso-valerate (P<0.05). The concentration of valeric acid and acetate to propionate ratio were not affected by steam explosion treatment. Moreover, STRS-II showed the higher in vitro DM degradability, OM degradability, DNDF and gas production (P<0.05); while, lower DADF and pH (P<0.05) compared with UTRS and STRS-I groups. These findings suggest that the steam treatment at 15.5 kgf/cm2 pressure for 120 sec, may be used to enhance the nutritive value and digestibility of rice straw.In vitro trail 2. On the basis of results obtained in first in vitro trial another study was conducted to compare the nutritive values and digestibility of the steam treated rice straws with alfalfa hay (AH) and Chinese wild rye (CWR). The steam treatment conditions were the same as used in first trial, i.e. STRS-I and STRS-II. The results regarding chemical composition revealed that steam treated straw had higher (P<0.05) dry matter (DM), ash and acid detergent fiber (ADF) contents; lower (P<0.05) organic matter (OM) than AH and CWR, the ether extract (EE) were higher and neutral detergent fiber (NDF) were lower (P<0.05) in AH and STRS-Ⅱ, while the crude protein (CP) were higher and acid detergent lignin (ADL) were lower (P<0.05) in AH than other groups. The concentration of acetate, buryrate and wo-butyrate were almost similar in STRS-II, AH and CWR; valeric and iso-valeric were lower (P<0.05) in CWR and STRS-I than AH and STRS-II, while the propionate and total VFA were higher in AH but similar in CWR and treated rice straw. The in vitro degradability of DM, OM and NDF were significantly higher for AH and STRS-II while, DADF was higher for AH. Steam treated straws showed increased (P>0.05) pH and NH3-N (P<005), while total gas production was higher in AH and STRS-II than other groups. These findings proposed that steam treated straw had better nutrients values and degradability over Chinese wild rye, so it could be partially used as forage for ruminants.In vivo trail 1. The in vivo study was conducted to further concrete obtained results through two in vitro trials and to determine the effects of steam treated rice straw (STRS-I) and (STRS-II) feeding on nutrient digestibility, performance, plasma anti-oxidative potential and rumen morphology of meat goats, digestibility and growth trails were conducted. In digestibility trail twenty male goats were divided in four groups of five goats each and assigned to four experimental diets:Chinese wild rye (CWR); untreated rice straw (UTRS); steam treated rice straw at 15.5 kgf/cm2 for 90 sec (STRS-I) and at 15.5 kgf/cm2 for 120 sec (STRS-Ⅱ) the goats were housed individually in metabolic cages. The results for digestibility trail revealed that the goat fed with CWR and steam treated rice straws (STRS-I and STRS-II) had similar but significantly higher dry matter (DM) and organic matter (OM) digestibility as compared to UTRS. However, the crude protein (CP), neutral detergent fiber (NDF) and acid detergent fiber (ADF) digestibility was significantly higher in STRS-Ⅱ than the other treatment groups. In growth trail the goats of UTRS and STRS-II, were used and housed in sheds. Results revealed that the average daily feed intake and weight gain was higher (P<0.05) for STRS-Ⅱ groups than UTRS. While, the steam treated straw feeding had no effects on relative organ weights. The plasma SOD and TAOC activities were higher and MDA was lower (P<0.05) in STRS-Ⅱ at 60 d. Whereas, the plasma GSHPx, CAT, ALT and AST at 30 and 60 d, while SOD, TOAC and MDA at 30 d were not differ (P>0.05) between the groups. The empty gut and the weights of all four compartments of the complex stomach were higher (P<0.05) in STRS-Ⅱ, while the gut fill was higher in goats of UTRS group. The rumen papillae length, width and surface area were higher (P<0.05) in STRS-Ⅱ as compared to the goats of UTRS group. In this trail it was observed that steam treatment of rice straw (at 15.5 kgf/cm2 for 120 sec) increased apparent nutrient digestibility and average daily weight gain. Further, the steam treated rice straw feeding had positive effects on anti oxidative potential, complex stomach and rumen morphology of growing meat goats.In vivo trail 2. The trail was conducted to investigate the effects of steam treated rice straw (at 15.5 kgf/cm2 for 120 seconds) feeding on growth performance, plasma volatile fatty acid profile and nutrient digestibility of goats kept under different housing system. Twenty male goats (18.69±0.34 kg) were used in a 84 d trail. The goats were divided into four groups of five goats each to receive steam treated (STRS) or untreated (UTRS) rice straw diet under closed house (CH) and open house (OH) systems. The results revealed that the goats fed with steam treated rice straw (STRS) had significantly higher dry matter (DM) organic matter (OM), crude protein (CP), neutral detergent fiber (NDF) and acid detergent fiber (ADF) digestibility, similarly the average daily weight gain and feed conversion ratio was higher in STRS under both CH and OH systems than UTRS groups. The plasma protein and insulin in STRS and cholesterol in UTRS groups was higher (P<0.05) at 60 d. The plasma amylase, lipase, T3, T4 and glucagon at 30 and 60 d, while total protein, cholesterol and insulin at 30 d were not differ (P>0.05) among the groups. The plasma acetate, propionate, butyrate and total volatile fatty acid were higher (P<0.05) in STRS groups at 30 and 60 d. The housing conditions had no effects (P>0.05) on these parameters. The steam treatment of rice straw at 15.5 kgf/cm2 for 120 sec increased apparent nutrient digestibility, hence increased the growth and feed efficiency of growing goats.In vivo trail 3. To investigate the effects of steam treated rice straw diets on carcass yield, composition, fatty acid and lipid oxidative stability the goats were assigned to steam treated rice straw at 15.5 kgf/cm2 for 120 sec (STRS) and untreated rice straw (UTRS) based diets for a trail lasted for 60 days. At the end of the trail all goats were killed and from the left side of carcass longissimus dorsi (LD) muscle was removed for determination of meat quality and fatty acid profile. The results showed that the steam treated rice straw diet improved (P<0.05) carcass yield and dressing% of goats as compared to untreated rice straw fed goats. Further, significantly higher protein and lower moisture was observed for meat in STRS group than UTRS, however the fat and ash contents, meat color (L*, a* and b*) values, pH45m and pH24h were not differ between the two groups. The malondialdehyde (MDA) values increased gradually after one and two weeks storage, but the values were not different (P>0.05) for two experimental groups. The fatty acid composition did not differ between the dietary treatments. However, total saturated fatty acids (∑SFA) and total monounsaturated fatty acid (∑UFA) for UTRS and total polyunsaturated fatty acid (∑UFA) for STRS group was higher (P>0.05). The goats fed on treated rice straw diet (STRS) maintained carcass yield, dressing% and meat composition without negative impact on meat characteristics.On the basis of obtained results from these experiments it could be concluded that; steam treatment at 15.5 kgf/cm2 for 120 sec, had positive effects on nutritive value and in vitro degradability of rice straw. Steam treatment at 15.5 kgf/cm2 for 120 sec, had better in vitro degradability as compared to Chinese wild rye. The goats fed with steam treated rice straw diet demonstrated higher digestibility, feed intake and weight gain than the goats fed with untreated rice straw diet under different housing systems. The steam treated rice straw feeding had positive effect on plasma volatile fatty acids, anti-oxidative potential and morphological characteristics of fore stomach and rumen of goats. The goats fed with steam treated rice straw diet had better carcass composition and dressing%, however the overall meat quality was not differ between the treated and untreated rice straw fed goats. Therefore, it is possible that steam treated rice straw could effectively be used as partially replacement of roughage during seasonal dry periods.