Live weight gain, feed consumption and feed conversion ratio
The treatment groups consisting of different amounts of corn silage and concentrated feed had no significant effect on body weight gain, feed consumption and feed conversion rates of domestic geese (P>005, Table 2 and Table 3). During the trial period covering 19-30 weeks, the total feed consumption was 14925.1, 15736.8, 13940.9, 17006.4, 17304.2 kg in the trial groups, respectively. The treatments did not affect weight gain, feed consumption, and FCR because roughage and concentrate were not fed ad libitum to the geese. It has been determined that corn silage up to 40% can be used in goose compound feed without any negative effect on performance. The use of silage at this level will of course lead to a decrease in feed costs.
In previous study by Wang et al. (2017) reported that dried citrus pulp can be used at a level of 12% in geese without adverse effects on growth performance and carcass yield. Also, Chen et al. (2020) suggested that 75% of broken rice could be used to replace corn in goose (28 to 70 days) diets. In addition, a large number of researchers have investigated the effect of different feed ingredients on the performance of geese such as broken rice (Chen et al.2020), citrus pulp (Wang et al. 2017), rygrass-forage (Song et al. 2017; Guo et al. 2020), lupine (Kuzniacka et al. 2020), cassava foilage (Li et al. 2019; 2020), silage (Kokoszynski et al. 2014; Yin and Huang, 2016). Song et al. (2017) suggested that the BW of geese fed with grain fortified grass during the 70-day trial was 3647 g, and an ideal fattening performance could be obtained due to the well-balanced diet of geese fed with a grass and grain supplement diet. In addition, higher feed consumption was found in the group that consumed more grass (54.74 kg) from pasture, confirming that geese were able to digest fiber in feed and ultimately had good growth performance (Song et al. 2017). However, the weight gains and final BWs of feed-only geese did not reach the market standard weight (3500 g) until day 70 due to the lack of crude protein and energy in the diet. Thus, it was emphasized that a grazing regime supported with grain is not only a method that can reach the standard weight of the market at 70 days of age, but also saves on grain feed. It was determined that 5% alfalfa substitution at the beginning and 10% during the growing period did not affect the live weight and feed consumption of the geese (Arslan, 2003).
Negative effects of low fiber diet (2.5%) on growth performance, slaughter performance, serum biochemical parameters and food use (6.1% and 4.3 % according to fiber level) were found in geese up to 70 days (Li et al. 2017). This finding supports that geese, which are herbivorous poultry, need dietary fiber for normal performance. In contrast, Guo et al. (2020) attributed the gradual decrease in the BW of Yangzhou geese with increasing grass intake in the diet, which may be due to the low energy content of the grass, which decreased BW gain in proportion to the increased amount of grass in the diet. Li et al. (2019) 28-70. It has been reported that the addition of cassava foliage (5%) to the goose diets improved carcass characteristics such as body weight gain, feed consumption, abdominal fat content and relative meat content. On the other hand, numerous studies on the use of roughage in Goose production have shown that moderate supplementation of roughage can improve growth performance, gastrointestinal tract development, nutrient digestibility, meat quality and microbial diversity (Wang et al. 2014; Jin et al. 2014; Liu and Zhou, 2013; He et al. 2015; Li et al. 2017; Li et al. 2020). It has been reported that fermented feeds have a significant effect on the caecal microflora composition of geese and can affect host growth, nutritional status and gut health (Yan et al. 2019). Similarly, Yin and Huang (2016) found that supplementing the basal goose diet with 8% fermented alfalfa grass had no significant adverse effects on growth performance, serum antioxidant enzyme activities and digestive parameters, and beneficial microbiota. It was determined that the use of cotton seed meal (>6.73%) decreased the growth performance of the geese at an early age (28-42 days), and increased the growth performance of 6.73% to 26.91% CSM, 28 to 70 days of age (Yu et al. 2019). Liu et al. (2019), who investigated the feeding of wet feed, determined that wet feed had no effect on weight gain, but because it increased feed consumption and feed efficiency, dry feed was more suitable for 28-70-day-old geese. It was determined that the digestibility of DM, CP and NDF in the groups with high crude cellulose content was higher than the control group (Li et al. 2020). In contrast, Borin et al. (2006) reported lower apparent digestibility in chickens and ducks fed a diet supplemented with crude fiber. Geese have a more developed digestive system compared to chickens and ducks (Li et al. 2020). Positive findings in nutrient digestibility reported with rice husk, whole corn, whole wheat, barley or oat supplementation (Vetési et al. 2000; Hetland et al. 2003; Amerah et al. 2009; Lu et al. 2011; Yang et al. 2016). Li et al. (2020) reported that the results obtained in their study can be explained by the fact that birds fed a high fiber diet probably have larger and more developed gizzard sizes. The larger gizzard may increase the grinding of feed, lead to greater exposure of nutrients to digestive juices and better food digestion (Wang et al. 2014; She et al. 2015). This shows that crude fiber may have beneficial effects on food digestibility in goose diets (Li et al. 2020).
There was no significant effect on slaughter weight and carcass yield, liver, gizzard and abdominal fat weights and ratios of the treatment groups (Table 4, P>0.05). The lack of effect of treatments on performance was due to the animals not being free fed. The fact that S20 had a higher heart weight percentage than the others was thought to be due to trial measurement error. The fact that the maize silage substituted at the highest level (40%) in the diet had similar carcass weight to the control group fed with fully concentrated feed confirms the hypothesis of this study.
Kokoszyński et al. (2014) reported that dilution of the commercial diet alone with whole-crop maize silage for young fattening geese had a positive effect on production economy and carcass composition. In this study, 17-week-old geese carcasses contained more chest and thigh muscles and less skin and subcutaneous fat compared to the control group. Considering the decrease of nearly 50% in the consumption of commercial feed mixture in favor of cheaper corn silage, the fact that the production profitability of geese increased in this diet is parallel to our research. At 21.97 kg of silage consumption per goose (55% of feed consumption), at the end of oat feeding (17 weeks), geese receiving silage had significantly longer bodies and drumsticks compared to fed geese (Kokoszyński et al. 2014). Geese fed diets containing 4.3% and 6.1% fiber had larger body sizes, heavier internal organs (heart, gizzard, proventricle, duodenum, jejunum, ileum, and cecum), compared to the 2.5% fiber group, with hot and cold carcass yield and breast yield was found to be greater (Li et al. 2017).
In contrast, Song et al. (2017) found that geese grazing reduces carcass yield, although the BW of geese with grain-fortified grazing is similar to grain-only indoor geese. Similarly, carcass yield, breast yield and thigh yield of grass fed geese with supplemental grain were significantly higher than those of grass fed geese only. In contrast, Guo et al. (2020) when fed under intensive feeding conditions with ryegrass in a ratio of 1.5:1 or 2:1, will contribute to good growth performance and increase in meat essential amino acids, essential fatty acids, total amino acids, n-3 fatty acid, Zn, and SFA content, it has reported that it will provide high quality goose production. He et al. (2015) found that four different fiber sources (corn straw silage, steam-popped corn straw, wheat straw and rice straw) had no effect on CAA and carcass properties. These differences observed between studies may be related to the composition and consumption of different roughages.
Findings that roughage consumption increases the amount of abdominal fat and breast and thigh meat because it causes more energy intake (Liu and Zhou, 2013; Wang et al. 2014, Li et al. 2019) differed from our research. On the other hand, the finding of Arslan (2003) that the addition of alfalfa grass to the diet in the initial (5%) and growing (10%) periods leads to a better quality carcass by reducing the fat ratio of goose carcasses contradicts the results of these researchers. However, the above research findings that roughage consumption does not change slaughter weight and carcass yield are consistent with our research.
The effects of roughage on carcass characteristics and particularly relative meat production vary as they are influenced by bird species and digestive physiology. Normally, as the fiber content in the diet increases, these feeds with a lower digestible energy content but occupying more space in volume cause an increase in the volume of the digestive tract of the animal, thereby making the digestive tract volume and the weight of the digestive organs more compatible (Wang et al. 2014). ). Moreover, poultry fed a roughage diet have shorter intestinal components, a larger diameter, and higher intestinal surface area than those fed whole grain diets (Jin et al. 2014; Wang et al. 2014). In general, poultry with a higher relative weight or relatively longer length by different gastrointestinal tracts are considered more beneficial in terms of fiber source utilization. As a matter of fact, Li et al. (2019) stated that the roughage (Cassava foliage) diet increases the relative length and weight of the small intestine in geese, while more cellulose and less nutrient content in the same volume causes the digestive organs to grow and the frequency of contractions due to the physically enlarged gizzard wall. Jin et al. (2014), Wang et al. (2014), She et al. (2015) also reported that roughage supplementation had similar effects on geese. Song et al., (2017) claimed that geese would reach their full potential when allowed to consume grass from pasture fortified with grain, protein, collagen, Mg and Cu content, and that this feeding regimen is an ideal model for goose production.
Nutrient content of meat
Table 5 shows that there was no significant effect (P>0.05) of treatments on crude protein, dry matter and ash values of goose breast meat. However, crude fat percentages were higher in S10, S20, S40 groups compared to S30 meats (P<0.05). This situation shows that since the geese were not fed in ad libitum diets, the physiological environment was not provided for excessive fattening of all groups.
Goose is an important grass-fed poultry for meat. Thus, goose meat products are low-fat, low-cholesterol and high-protein (Fowler et al. 2018; Li et al. 2020). Tang et al. (2020) reported that the protein content of goose meat is 22.3%, the fat content is 11%, and more than 99% of the total fat consists of unsaturated fatty acids. The composition of the meat, especially the amount of fat, can vary according to the diet of geese (Boz et al. 2019). The nutritional composition of meat muscle (including protein, fat and collagen) is an important indicator of meat quality (Kuzniacka et al. 2020) and their amount constitutes nutritional value. As a matter of fact, consumers associate the smell, taste and flavor of a poultry product with its quality (Matyba et al. 2021; Karasu and Öztürk, 2018; Oğul and Öztürk, 2018; Doğan and Öztürk, 2019). Therefore, the nutrient content of meat is an important criterion in determining meat quality (Ozturk et al. 2010; 2014; Erener et al. 2011; Sarıca et al. 2014; Dogan and Ozturk, 2019). Marbling, known as intramuscular fat distribution, is considered as an element that improves meat quality, apart from other fats, as it positively affects the aroma and flavor of meat. Indeed, Lebret and Guillard (2005) and Arslan et al. (2003) reported that more protein and collagen and less fat accumulated in muscle in grazing geese, which may be due to the lower energy content of the feed. Kuzniacka et al. (2020) determined that protein and intramuscular fat content and water content in breast or thigh muscles were higher in the substituted lupine (30-35%) groups than in the soybean meal group. Li et al. (2020), using cassava foliage (5% and 10%) as roughage, reported that there was no difference between the treatments in terms of dry matter, crude protein and crude oil ratios. On the other hand, Arslan (2013) showed that the growth rate in pasture-based feeding was slower than in intensive and semi-intensive feeding, but low-fat carcass was obtained. The protein content and muscle collagen in breast and thigh meats were higher and the fat content was lower in the grazing treatment compared to the control (Song et al. 2017).
Physiological studies on how nutrient content changes in goose meat tissue are limited. One of the rare studies on this subject showed that differentially expressed genes related to the insulin signaling pathway can increase protein synthesis and fat production, and that the interaction network of these genes is mainly related to the endocrine system. The differentially expressed genes related to the growth and function of the pituitary organs can regulate the growth and development of the body by affecting the synthesis and secretion of pituitary hormones, which will help to understand the regulatory mechanism of goose growth and development (Tang et al. 2020). Due to the complexity of the processes involved in the synthesis and catabolization of proteins, waterfowl typically use their protein stores as an energy source in extreme situations where lipid stores are depleted (Blem, 1990). It has been observed that the nutrients in goose meat can also change seasonally, protein stores are more stable than lipids and slightly increase as winter progresses, lipid stores are highest in November and lowest in February. It has been determined that there is an increase in endogenous lipid stores of geese at the beginning of winter, when high-energy food sources are most abundant, and a decrease as winter progresses (Massey et al. 2020). Fat ratio in meat may vary depending on the animal's breed, age, energy/protein ratio in feed, balance of nutrients in the diet and production system (Ozturk et al. 2012; Hughes et al. 2014; Boz et al. 2017; Uhlirova et al. 2018; Haraf et al. 2021).
Feeding domestic geese with different amounts of corn silage and concentrate had no effect on a*, b* and pH values of breast and thigh meats (P>0.05). On the other hand, while S00 and S10 had the highest value in breast meat L* value, S20 and S30 groups followed these groups, while S40 was at the lowest level (Table 6). The L* value of thigh meat was lower in the S40 group than all other groups (P<0.05), and there was no difference among the other groups.
Kuzniacka et al., (2020) determined that the addition of lupine instead of soybean meal to the diet did not have a negative effect on goose meat color and water holding capacity and meat characteristics, but negatively affected growth performance. On the other hand, Song et al. (2017), Wang et al. (2009) and Liu et al. (2011)'s findings on different feeding regimes did not change the pH values of goose meat are similar to our study. Also, the findings of Kuzniacka et al. (2020), who reported that the pH value of the meat was higher (7.9-8.2) in the soybean meal group, differs from our study. While consumers primarily consider issues such as the price, appearance and color of meat when purchasing meat, the most determining factor as a quality criterion is actually color (Sarıca and Yamak, 2010; Karasu and Öztürk, 2018; Ogul and Ozturk, 2018; Dogan and Ozturk, 2019; Li et al., 2020). The surface colors of meat are largely controlled by pigments composed of myoglobin, hemoglobin and cytochrome C. There is a positive correlation between total pigment concentration and Fe and a* value, and a negative correlation with L* value. In particular, meat with a high a* value has a darker color (Boulianne and King, 1998). It has been shown that roughage or high level fiber content increases the L* value in geese (Castellini et al., 2002) and broilers (Liu et al., 2013) and lowers the final pH of the goose or broiler. Using cassava foliage (5% and 10%) as roughage, Li et al. (2020) reported that there was no difference between the treatments in a* and b* values. They found an increase the pH and shear force of the breast muscle and a decrease in L* values in the control group. Shrinkage caused by low pH; It can be explained by the shrinkage of the fibers, decreasing the water binding ability and increasing the light scattering (Warriss, 2000). pH value, which is an important index of meat quality, is one of the factors affecting shelf life. The pH determined in our study was similar to the pH level found in thigh or breast meat of Yakan et al. (2012) and Sarıca et al. (2014) who experimented under extensive conditions in Turkish geese (32-36 weeks old), Boz et al. ( 2019) was found to be higher the pH values (5.74 to 7.02) reported in other studies with local Turkish geese (Kirmizibayrak et al. 2011; Boz et al. 2017) were similar to or lower than those in this study. PH values may vary depending on age, production system and nutrition (Hughes et al.2014; Boz et al. 2019).
Breast meat consists of white, thigh meat consists of red fibers. Red fibrils contain more myoglobin, less glycogen and glycolytic enzymes than white fibrils (Aberle et al. 2001). Therefore, although it has been reported that the pH in thigh meat is higher than breast meat (Oz and Çelik, 2015; Boz et al. 2019), in our study, a relatively higher pH was found in breast meat, which is close to each other. Properties such as pH value, water holding capacity, cooking loss, hardness, springiness, stickiness, cohesion, chewiness, color and shelf life are effective features in determining meat quality (Ozturk et al. 2012; Dogan and Ozturk, 2019; Kuzniacka et al. 2020). While the decrease in the pH of the meat decreases the bacterial load, the increase in the pH shortens the shelf life of the meat as it increases the pathogenic microbial load (Şekeroğlu and Diktaş, 2012; Ozturk et al. 2012; Dogan and Ozturk, 2019). In addition, high pH causes an undesirable appearance (dry, firm and darker color) in meat and a firmer appearance by preventing intramuscular protein degradation (Sarica et al. 2014). A pH below 5.7 in meat is considered an indicator of low meat quality (Alvarado et al. 2007). Boz et al. (2019) reported that the differences between meat color of geese and commercial lines may be related to late slaughter age (28 weeks) and pasture feeding. Boz et al. (2019) attributed the color and pH differences to the body weight difference in domestic goose varieties, while Liu et al. 2011; Yalçın et al. 2014; Boz et al. (2017) attributed meat quality characteristics such as pH, color and dry matter to growth characteristics, growth rate and body weight. Hughes et al. (2014) reported that the color and pH of meat may change depending on age, production system and feeding. Li et al. (2020) found that the pH of breast meat was higher in the control group than in the groups with high crude cellulose content. Similar results were obtained by Liu et al. (2013) in geese and by Castellini et al. (2002) in broilers by Mourӑo et al. (2008). This finding could possibly be attributed to the fact that feed intake improves the carbohydrate level and thus decreases glycogen metabolism, which can maintain the acid-base balance in the animal (Castellini et al. 2002; Foulkes and Cohen, 2010; Li et al.2020).
Texture profile analysis and organoleptic quality characteristics of meat
Since the determination of meat quality made by organoleptic methods is subjective, the quality characteristics of goose meat were also determined objectively by analyzing the texture profile (Öztürk and Turhan, 2020) (Figure 1). There was no difference between the treatment groups in terms of springiness, cohesiveness, chewiness and resilience characteristics (P>0.05, Figure 1). Hardness (N) values decreased with the addition of silage (P<0.05), except for the S20 group. This observed trend can be interpreted as a general decrease in the firmness of goose meat with the addition of silage to the diet. On the other hand, in terms of adhesiveness, which is an indicator of unhealthy meat, S00 was found to be higher than the other groups (P<0.05). The decrease in adhesiveness and hardness in meat as the silage substitution in diet increases is a very good development in terms of increasing consumer appreciation for meat.
It is desirable that fresh meat be firm, brightly colored, with no broth separated and with little binding texture. In contrast, hardness may result from increased connective tissue in the meat or from rigor motility after slaughter. On the other hand, the fact that the meat is softer indicates that the intramuscular fat tissue increases, in other words, the amount of marbling increases. On the other hand, the concentration of fat in other parts of the body, such as shell fat, rather than in the form of marbling, causes a decrease in fat between the muscles and further hardening of the meat (Öztürk and Turhan, 2020). Although no results were obtained in our study to support this finding in meat fat analysis, the decrease in hardness in texture profile analysis can be interpreted as an increase in meat marbling. This shows that the addition of corn silage instead of concentrated feed to the diet of domestic geese reduces the hardness of the meat and provides soft meat that is more suitable for consumers. According to the organoleptic meat quality test, there was no difference between the treatment groups in terms of sensory quality characteristics (appearance, flavour, hardness, tenderness, juiciness, chewiness and overall acceptability) of goose meat (Table 7, P>0.05).
Physical properties such as meat color and water holding capacity play an important role in the quality assessment of meat and meat products (Barbera et al. 2019; Oğul and Öztürk, 2018; Doğan and Ozturk, 2019). These properties also affect the suitability of raw meat for further processing and the economy of meat production. The quality of meat obtained from broiler geese depends on genotype, age and management system, especially diet (Uhlirova et al., 2018). The quality and quantity of muscle tissue in the carcass depends on the composition of the feed used in their diet (Ozturk et al. 2010; 2012; 2014; Kuzniacka et al. 2020).
Numerous studies on the use of roughage in goose production have shown that moderate supplementation of roughage can improve growth performance, gastrointestinal tract (GIT) development, nutrient digestibility, meat quality and microbial diversity (Liu and Zhou, 2013; Wang et al. 2014; Jin et al. 2014; He et al. 2015; Li et al. 2017). Supporting the findings of these researchers, Kuzniacka et al. (2020) reported that the inclusion of broad beans in the goose diet had a positive effect on meat quality. Geese can reach their full potential when allowed to consume grass from pasture fortified with grain, protein, collagen. Indeed, Song et al. (2017) found that leg yields were lower in the grain fed regimen compared to the grazing groups. This result shows that geese can produce a higher thigh yield with the grazing model (Castellini et al. 2002), indicating that this roughage replacement feeding regimen is an ideal model for goose production. Shearing force is an index to evaluate the tenderness of meat, and meat with lower cutting force is softer. Li et al. (2020) stated that the shear force in control geese was higher than in those fed diets with higher crude fiber diets. On the other hand, Liu and Zhou (2013) found that the consumption of meadow grass had no effect on shear force in goose meat. This inconsistency in results may be related to forage composition and consumption.