Effects of Steam Treated Rice Straw-Based Diet on the Physico-Chemical Properties of Goats Longissimus Muscle

The present study was carried out to investigate the effects of steam treated rice straw-based diets on, physico-chemical properties of longissimus muscle of goat. Goats were assigned to rice straw treated with steam at 15.5 kgf/cm 2 for 120 Sec (STRS) and untreated rice (UTRS) straw-based diets. After 60 days all goats were slaughtered and 50 g of muscle longissimus dorsi (LD) was removed from left side of carcass for determination of meat quality and fatty acid prole. 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. Signicantly higher protein and lower moisture was observed for meat of STRS group than UTRS, however the fat, ash contents, meat color and pH were not different between the groups. The TBARS values gradually increased in stored meat. The different diet did not affect the composition of fatty acids. Total saturated ( ∑ SFA) monounsaturated fatty acids ( ∑ MUFA) for UTRS and total polyunsaturated fatty acid ( ∑ PUFA) for STRS group was higher (P > 0.05). It is concluded that the goats fed on treated straw diet (STRS) maintained carcass yield, dressing % and meat composition without negative impact on meat characteristics.


Introduction
The use of cereal grains, wheat and barley straws have become a common practice for ruminant feeding (Al-Dalain et al. 2020) but grain based commercial supplements may not be economical for growing and nishing meat goats because high starch supplement in feed lead to decrease in pH and ber digestibility (Mwangi et al. 2019). The brous by products such as cereal straws are a main component of the ruminant diet in tropical and subtropical areas during both cropping seasons and dry or winter periods (Ghasemi et al. 2014). It is, however, imperative that for increasing the productivity in the livestock sector, effective strategies should be designed to improve the e ciency of crop residues (Kurokochi and Sato, 2020).
Nevertheless, supplementation of feedstuffs along with crop residues may improve the nutritive value of crop residues or treatment with chemicals which enhance digestibility after partially solubilization of The consumers demand high quality and convenient meat products with natural avor and taste (Karami et al. 2011). The unsaturated fatty acids contents in meat have importance related to the consumer's health (Paengkoum et al. 2013). It has been investigated that in the tissue of caprine and bovine fatty acid pro le is being in uenced by diet, age and production system (Dhanda et al. 1999). In meat, together with metal ions, heme proteins, and reactive oxygen species, highly peroxidizable poly unsaturated fatty acids (PUFA) may be considered prooxidant components and the risk of oxidation lift by increasing unsaturated fatty acids in meat. The free-radicals are involved in the oxidation of lipids that is a primary reason of shelf-life reduction and rancidity development in many kinds of meats (Luciano et al. 2011;Paengkoum et al. 2013).
However, different studies showed that residues of crop supplementing with other feed stuffs or increasing digestibility by using chemicals and/or feed taken after dissolving crusting substances (Cellulose, hemicellulose and lignin) that cause improvement in ruminant performance (Abebe et al. 2004). Very limited information is present regarding characteristics of carcass and meat quality of goats when reared on steam treated rice straw feeding. Hence, the aim of present study was to determine steam treated straw in order to search economical ration (growing and nishing) for meat-goat to minimize negative impact on the environment of rumen while feeding high-starch diets to ruminants.

Materials And Methods
Steam treatment of rice straw The rice straw was obtained from the agricultural eld of Nanjing Agricultural University. The samples were chopped, and steam treated for 120 Sec at steam pressure of 15.5 kg f/cm 2 (STRS-2). The College of Engineering Nanjing Agriculture University designed the steam explosion machine and dried treated and untreated rice straws was transported to experimental farm.
Location and description of the study area The experiment was conducted at the goat farm situated at Liuhe Animal Science Base of Jiangsu Academy of Agricultural Science, Zhuzhen, Nanjing, China. There is mean annual temperature of about 28°C (82 °F) in July, while -7 C (19 F) in January months respectively. Moreover, this area has an approximately 1,100 millimeters (43 inches) average rainfall, 117 rainy days and have almost 76% mean relative humidity.

Animals' management and feeding
The experiment was conducted according to the animal care and guidelines of the Animal Care Committee, Nanjing Agricultural University China. Ten Xuhuai goats (18.47±0.39 kg) were equally divided into two feeding groups and were assigned to untreated (UTRS) or steam treated (STRS) rice straw diets (Table 1) in a 60-day trial period, a 7 day adaptation period was provided to the goats prior to start of the trail. The goats were kept in a 15′×20′ shed with height at center 10′, side walls of chain link fencing 6′, slatted oor, troughs used for feeding and a central alley. Goats were offered feed on ad libitum twice daily at 08:30 and 16:30 hour (h).

Meat sampling and carcass traits
At the end of 60 days trail all the goats were individually weighed and humanely slaughtered after an 18 h fasting. After slaughtering animals were hanged for skinning which was removed in order head (up to the atlanto-occipital joint) forefeet and hind feet up to the carpal-metacarpal joint and the tarsalmetatarsal joint respectively. The muscle samples were subsequently taken from left side of carcass. A sample of about 50gm from left side longissimus dorsi (LD) muscle was taken and at -20°C stored for further analysis. Fasted live and carcass weight were recorded immediately after slaughtering and the dressing percentage was calculated by dividing the carcass weight with live weight and expressed as a percentage (%).

Muscle pH and color
The digital pH meter (Hanna, Model HI9918, USA) was used to measure the pH values of meat samples. The pH value was recorded at 45 min of post-mortem as pH 45 min, and pH 24 h at 24 h of post-mortem on the muscle (longissimus dorsi) after equilibration to room temperature. The calorimeter (Konica Minolta, CR -400, Japan) was used to assess the color of muscles for lightness (L*), redness (a*) and yellowness (b*).

Chemical analysis of meat
Moisture contents of meat were estimated by the loss in weight of 3 g minced meat and the LD muscle samples were dried for 48 h in oven at 105°C. The dried samples were aged in a mu e furnace at 550 °C for 8h and the ash contents were recorded. Analysis of crude protein (CP) by using 1 g of sample following Kjheldahl method as detailed in the AOAC (2000). The total fat contents were determined from 5 g samples in a Soxhlet apparatus following a 6-cycle extraction with petroleum ether.

Measurement of lipid oxidation
The lipid oxidation was evaluated by measuring Thiobarbituric acid reactive substances (TBARS) by utilizing malondialdehyde (MDA) standard with the help of chemical diagnostic kit (Nanjing Jiancheng Bioengineering Institute, Nanjing, China) and values were expressed as nmol/mg protein.

Fatty acid pro le
Muscle samples were taken gently, and external visible fat was removed. The samples were ground homogeneously to estimate fatty acid composition. The total lipids were extracted following the chloroform-methanol procedure. Extracted lipids were trans methylated into fatty acid methyl esters and isolated by Gas Chromatograph using a Shimadzu GC-2010 equipped with CP-WAX 30M I.D.0.32 mm capillary column. The nitrogen and hydrogen were used as carrier and fuel respectively whilst the air as a combustion-supporting gas were used at constant flow rate of 3, 47 and 400 ml/min, respectively. Spilt ratio was 1:10 and 1 μl was injected. The detector and injection port were maintained at 250 °C.
The fatty acids were calculated individually according to the relation of peak area to the total area. The fatty acids were denoted as the part of each individual fatty acid to the total of all fatty acids present in the sample. The combinations and ratios of fatty acids were calculated as desirable fatty acids (DFA), total saturated fatty acids (SFA), total unsaturated fatty acids (UFA), total monounsaturated fatty acids (MUFA), polyunsaturated fatty acids (PUFA), UFA/SFA and PUFA/SFA, respectively.

Statistical Analysi
The statistical analyses were performed by using software (SPSS 16.0 K for Windows, Chicago, IL) and the obtained data were expressed as the means ± SEM values. The mean values were compared by Oneway analysis of variance technique and signi cant difference at (P< 0.05) among the means were found by Turkey's comparison test.

Chemical composition and carcass traits of meat
The meat from the goats offered with steam treated rice straw (STRS) exhibited higher mean percentage of protein and lower moisture (P 0.05) contents as compared to the meat of goats fed with untreated rice straw ration (UTRS). Similarly, the fat percentage was higher and ash contents were found lower in meat of the STRS group than UTRS group, however the differences were not signi cant between the groups ( Figure 1).
The results regarding carcass traits are presented in Figure 2. The goats of STRS groups had a higher fasting body weight than goats of UTRS groups. Carcass yield and dressing percentage followed a similar trend where these were recorded higher (P<0.05) in STRS fed goats than those fed UTRS diet.

pH and Meat Color
The physical characteristics, i.e., pH and color of the meat are presented in Table 2. The results revealed that the pH of meat at 45min as well as at 24h remained unchanged (P > 0.05) between the UTRS and STRS groups. Moreover, the lightness (L*) and yellowness (b*) values were recorded higher and redness (a*) was lower in the STRS group as compared to the UTRS group, despite the lack of statistically signi cant differences.

Fatty acid pro le
The effect of the diets on the composition of fatty acid of goat kids is presented in Table 3. Muscles from both STRS and UTRS groups contained oleic, palmitic and stearic fatty acids as most abundant fatty acids. The oleic and stearic acid were found higher in meat of UTRS goats, while the palmitic acid was higher in meat of the STRS group without any statically differences between the groups. However, SFA like capric, myristic, margaric and eicosanoic for UTRS group were higher and in consequence the total saturated fatty acids were also found higher (P>0.05) in UTRS group as compared to the STRS group. While lauric, pentadecanoic and behenic acids were higher (P>0.05) for STRS group. The palmitoleic (MUFA) and other polyunsaturated (PUFA) i.e. linoleic, linolenic and arachidonic were recorded higher in STRS group, resulting in higher total polyunsaturated fatty acid and unsaturated fatty acid proportion than UTRS group which further resulted in higher UFA:SFA and PUFA:SFA despite the lack of statistically signi cant differences. Whereas the stearidonic acid and total monounsaturated fatty acids were higher (P>0.05) in UTRS group. There was also no difference (P>0.05) for desirable (C18:0+UFA) fatty acids between the two groups.

Lipid oxidation
The results regarding the effects of straw feeding on lipid oxidation in fresh and stored meat of goats are presented in Figure 3. Slightly lower values of TBARS as units of malondialdehyde (MDA) were recorded in STRS than UTRS group in fresh and stored meat. However, the differences were not signi cant between the steam treated rice straw and untreated rice straw fed goats.

Meat color and pH
The fall in the pH rate and ultimate pH are major decisive of meat quality and are associated to the glycogen breakdown rate, while the meat color, is one of the most important parameter of consumer choice (Pi et al. 2005). The pH was found not effected with different feeding diets both groups of goats fed on UTRS and STRS maintained normal pH value (5.9-6.5). The similar ndings have been reported by Safari et al.(2011a), stated that there was no difference in meat pH at 45 min or 24 h between the goats fed on treated wheat straw, untreated wheat straw, treated wheat straw with hay or untreated wheat straw with hay.
The meat color is dependent of many individual factors and their correlations, but the Chevon has higher redness and lower lightness than the lamb, mostly because of the lower intramuscular fat of goat carcass (Kannan et al. 2001). Abdullah and M usallam, (2007), showed that feeding regimen has no effect on color variables. The meat color characteristic was not found to be differed between the untreated and treated straw fed goats which in accordance with the ndings of Pi et al. (2005) showed that the redness (a*), yellowness (b*) and lightness (L*) values of meat were not in uenced by the treated or untreated rice straw-based diets. The results are parallel to the results in the native black goat of Jordan investigated by Abdullah and Musallam (2007).

Fatty acid pro le
It has been described that the fatty acid profile of tissues is affected by diet (Abbasi et al. 2020). The values investigated for meat fatty acid contents in present study agreed with those noted for goats (Banskalieva et al. 2000). However, in our study the difference between treated and untreated rice straw fed goats for meat fatty acid had no signi cance. The prevalence of three abundant fatty acid i.e., palmitic acid, stearic acid and oleic acid accounted in the range of 75% to 78%, dominated by oleic acid which accounted 38% to 40% of total fatty acids, these nding are satis ed with values commonly established for goat (Atti et al. 2006). The higher oleic acid values (C18:1) may be attributed to the higher animal biosynthesis from stearic acid (C18:0) (Rule et al. 1997), it indicates that the straw feeding had no negative impact on oleic acid biosynthesis which had an improvement in meat quality. The proportions of the DFA's which include all unsaturated fatty acids and stearic acid, noted in this study were around 76% for both group that was in the range of (61-80%) as observed by Banskalieva et al., (2000) for goat meat. Jaakamo et al. (2019) observed that the percentage of grass and concentrate in a diet affects PUFA. However, higher (P>0.05) amount of UFA and MUFA observed in STRS diets re ecting that the treated straw feeding had no negative impact on carcass unsaturated fatty acid characteristics.

Lipid oxidation
The mechanism of lipid oxidation starts after death immediately, as circulation of blood stops and metabolic processes are blocked, in results free radicals are produced which may cause the oxidation of meat pigments and generate rancid odors and avors (Arshad et al. 2018). The MDA level for fresh and stored meat was not found affected by the treated and untreated straw feeding, however an accepted rise in MDA was recorded after one and two-week storage, in this study statistically diet was not a major effect, but it was the effect of aging and storage that re ected rise in oxidative values as the quality of meat did decrease over time, because the TBARS value of meat enlarge with storage (Franco et al. 2012).

Conclusion
The results of the present study suggested that it is possible that steam treated rice straw could effectively be used as partially replacement of roughage during dry periods as the goats fed on treated straw diet maintained similar carcass yield, dressing % and meat composition traits compared to those given the conventional diets, without a negative impact on meat characteristics. However, the fatty acid pro le and oxidative stability were not found to be affected by the treatments therefore more research are needed to optimize the level of steam treated rice straw provided in the diet to obtain a balance between the production of meat and its nutritional quality.

Declarations Acknowledgments
The research was conducted at Nanjing Agricultural University, China. Authors are thankful to the College of Animal Science & Technology for providing the necessary facilities to carry out this research.

Funding Information
The project was nancially supported by China Scholarship Council, People's Republic of China.

Con ict of interest
We certify that there is no con ict of interest with any nancial organization regarding the material discussed in the manuscript.

Ethical statement
The study was approved by the institute ethics committee, and the trial/sampling procedure was carried out following ethical standards. The manuscript does not contain clinical studies or patient data.

Consent to participate
All the authors critically reviewed and read the manuscript as well as approved the contents.
Consent for publication I assure that manuscript has not been previously published, is not currently submitted for review to any other journal and will not be submitted elsewhere before a decision is made by this journal.

Data availability
The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.