The effects of whole-plant silage maize as replacement commercial feed on the growth performance, carcase yield, relatively organ weight, blood biochemical, and economical traits in Holdobaki Goose

Abstract This study aimed to investigate the effects of replacing commercial feed with varying proportions of whole-plant silage maize in the diet of Holdobaki geese. The study evaluated growth performance, carcass characteristics, relative organ weight, blood biochemical, and economical traits in 192 fifth-week-old geese. The geese were randomly divided into 4 treatments with 8 replicate pens per treatment and 6 geese per replicate pen. The control group (0SM), which received 0% whole-plant silage maize and 100% concentrate; the 15SM group, which received 15% whole-plant silage maize and 85% concentrate; the 30SM group, which received 30% whole-plant silage maize and 70% concentrate; and the 50SM group, which received 50% whole-plant silage maize and 50% concentrate. The results showed that the final body weight (FBW) and average daily gain (ADG) of the 50SM group were significantly reduced (P < 0.01), and Feed conversion ratio (FCR) was significantly increased (P < 0.01). Compared to the 0SM group, the average daily feed intake (ADFI) was significantly increased in the 15SM, 30SM, and 50SM groups. The abdominal fat yield of the 50SM group was significantly reduced (P < 0.05), and the relative weight of goose gizzards was significantly increased in the 15SM, 30SM, and 50SM groups (P < 0.05). Total triglycerides (TG) levels of 30SM and 50SM were significantly lowered, and blood urea nitrogen (BUN) levels of 15SM and 30SM groups were significantly lowered (P < 0.05). The 30SM group had the highest economic benefit, with an income per goose of $1.92. In conclusion, the findings of this study demonstrate that replacing commercial feed with whole-plant silage maize in the diet of Holdobaki geese has significant effects on their growth performance, carcase yield, relative organ weight, and blood biochemical parameters. The combination of 30% whole-plant silage maize and 70% concentrate improves economic benefits, whereas a substitution rate of 50% has a negative impact on goose growth.

30% whole-plant silage maize and 70% concentrate; and the 50SM group, which received 50% whole-plant silage maize and 50% concentrate.The results showed that the final body weight (FBW) and average daily gain (ADG) of the 50SM group were significantly reduced (P < 0.01), and Feed conversion ratio (FCR) was significantly increased (P < 0.01).Compared to the 0SM group, the average daily feed intake (ADFI) was significantly increased in the 15SM, 30SM, and 50SM groups.The abdominal fat yield of the 50SM group was significantly reduced (P < 0.05), and the relative weight of goose gizzards was significantly increased in the 15SM, 30SM, and 50SM groups (P < 0.05).Total triglycerides (TG) levels of 30SM and 50SM were significantly lowered, and blood urea nitrogen (BUN) levels of 15SM and 30SM groups were significantly lowered (P < 0.05).The 30SM group had the highest economic benefit, with an income per goose of $1.92.In conclusion, the findings of this study demonstrate that replacing commercial feed with whole-plant silage maize in the diet of Holdobaki geese has significant effects on their growth performance, carcase yield, relative organ weight, and blood biochemical parameters.The combination of 30% whole-plant silage maize and 70% concentrate improves economic benefits, whereas a substitution rate of 50% has a negative impact on goose growth.

Introduction
Goose meat is an essential part of traditional Chinese cuisine because of its high content of essential amino acids that are crucial for human growth and development.Chinese consumers highly appreciate it for its high-quality protein, abundant amino acids, vitamins, and minerals.Although China produces approximately 540 million meat geese annually, which accounts for 94% of the global total, the per capita consumption remains less than one goose.The high production cost is a significant challenge for the development of the goose industry, and it is essential to reduce production costs urgently to facilitate industry growth and meet the demand for goose meat among consumers (Hou & Liu, 2023).
The Holdobaki goose, developed by the Hungarian Holdobaki Goose Corporation, is a highly regarded dual-purpose breed known for its down and egg production.It is particularly popular among the largest European waterfowl farming and processing enterprise.The Holdobaki goose is famous for its tender meat, high protein content, low fat, and low cholesterol, making it a prized ingredient in international cuisine.The breed has a brooding period of 28 days, at 60 days, which can reach up to 4.5 kilograms.After 180 days of feeding, male geese can weigh between 8-12 kilograms, while females can weigh between 6-8 kilograms.Additionally, the breed exhibits excellent reproductive performance, with an average annual egg production of up to 50 eggs, each weighing between 170-190 grams.The Holdobaki goose is known for its wide adaptability to different feeds and can tolerate coarse feeds.It has excellent digestion and absorption capabilities, especially with grass and powder feeds, like whole-plant silage maize.This breed has several advantages, including short production cycles, low costs, and strong disease resistance, which makes it an ideal experimental material (J.Chen et al., 2022).
Geese, being herbivorous animals, have a natural advantages over other poultry species in digesting and utilizing dietary fiber (Adli et al., 2022).They have a well-developed intestinal tract that contains various bacteria that can decompose cellulose and produce enzymes that react with cellulose to produce volatile fatty acids, ammonia, and carbon dioxide (4).Geese secrete gastric acid to dissolve chyme, which they can absorb and utilize (Lu et al., 2011;Yang et al., 2018).This ability of geese to tolerate rough feed and utilize high-yield, low-cost forage, straw, or silage can be taken advantage of in production.By partially replacing concentrate in the goose diet, costs can be reduced (Guo et al., 2020;He et al., 2015).Forages lose their nutritional value quickly after mowing and most stop growing in winter.Crop straws are not very palatable and have low utilization rates (Wang et al., 2022).However, silage is promising and stable source of roughage for geese due to its high output, low cost, high nutritional value, and long storage time (Ferraretto et al., 2018).Maize is the most productive crop in China and is widely grown.It has good silage adaptability and provides high-quality silage that is rich in nutrients, aromatic, highly digestible, and contains more than 8% crude protein (Cui et al., 2022;Haerr et al., 2015;Keady et al., 2007;Wu et al., 2021).A recent study conducted in Turkey found that adding silage maize to the diet of male indigenous geese does not harm their growth performance or meat nutritional components.In fact, it can improve the tenderness and firmness of the meat, and also helps reduce production costs by up to 40% (Aslan & Öztürk, 2022).These results suggest that using whole-plant silage maize as a substitute for part of the concentrate in the diet of meat geese is feasible.This study aims to investigate the effects of replacing commercial feed with different proportions of wholeplant silage maize in the diet on various aspects of Holdobaki geese, such as growth performance, carcase yield, relative organ weight, blood biochemical, and economical traits.

Materials and methods
Animal protocols in this study were approved by the Shanghai Science and Technology Committee (STCSM) with license number SYXK (HU): 2015-0007 and conducted in compliance with authorized guidelines and regulations.All possible measures were taken to reduce the suffering of the geese involved in the study.

Animal and housing
In this study, 192 5-week-old Holdobaki geese were used.The research was conducted for 4 weeks in the naturally ventilated, windowed research cluster of the Zhuanghang Comprehensive Experimental Station of the Shanghai Academy of Agricultural Sciences, from August to September 2020.The geese were housed individually in compartments with a floor area of 1.9 m x 1.9 m x 0.5 m (3 animals/m2).All compartments are equipped with water troughs and feeder basins, geese can eat or drink freely.The temperature inside the goose housing facility was maintained within the range of 15 to 24 degrees Celsius, while the humidity was maintained between 50% and 70%.These environmental conditions were optimized to provide a suitable rearing environment that promotes the growth and well-being of the geese, ensuring the integrity and validity of the experimental results.

Experimental design and treatments
A total of 192 5-week-old Holdobaki geese (half male and half female) were obtained from Anhui Gui Liu Livestock Group, and whole-plant silage maize was purchased from Shanghai Nonghao Feed Co., Ltd.Prior to the experiment, each goose was weighed to determine its initial body weight.Subsequently, the 192 geese were randomly divided into four treatment groups, with 8 replicates per group and 6 geese per replicate (consisting of an equal number of males and females).The determination methods for crude protein (CP) in the basal diet and whole-plant silage maize were conducted following the procedure described by the Association of Official Analytical Chemists (AOAC) in 2005 (AOAC, 2005).The determination method for crude fiber (CF) was carried out according to the procedure described by the AOAC in 2000 (AOAC, 2000).The determination method for metabolizable energy (ME) was conducted following the procedure described by Miller et al (Miller & Judd, 1984).Based on the nutrient composition of the whole-plant silage maize and the proportion of maize replacing the alternative feed, the basal diets for each treatment group were formulated according to the nutritional standards for geese outlined in the National Research Council 1994(NRC 1994).The whole-plant silage maize was chopped using a forage cutter and thoroughly mixed with the basal diets of each treatment group to prepare the experimental diets.The treatment groups consisted of: 0SM, the control group, using 100% concentrate feed; 15SM, using 15% whole-plant silage maize and 85% concentrate feed; 30SM, using 30% whole-plant silage maize and 70% concentrate feed; and 50SM, using 50% whole-plant silage maize and 50% concentrate feed.To ensure freshness, an experimental diet was prepared every 3 days.The nutritional composition of the diets for each treatment group and the WECS can be found in Table 1 and Table 2, respectively.

Growth performance
Geese were weighed at the beginning (week 5) and end (week 9) of the experiment after an 8-hour fast.The consumption of experimental diets (whole-plant silage maize + concentrate feed) was recorded for each replicate column.Average daily gain (ADG), average daily feed intake (ADFI), and Feed conversion ratio (FCR) were then calculated for each goose.The calculation methods of growth performance indicators were as follows: ADG = (FBW-IBW)/number of days in the experiment FCR = feed consumption/total weight gain ADFI = FCR x ADG

Carcase yield and sample collection
At the end of the 9th week of the experiment, one male goose close to the average body weight was selected from each replicate and artificially slaughtered after blood was collected from its wing vein.The blood was left to stand at room temperature for 2 hours, then centrifuged at 3000 rpm for 10 minutes to separate the serum, which was collected for determination of biochemical levels.After the goose was slaughtered by jugular vein bloodletting, it was placed in a hot water pool at 55°C for 2 minutes, plucked, and weighed using a poultry depilator to obtain the carcass weight.The abdominal cavity was then opened, all organs, trachea, and crop were removed, and the remaining weight was obtained to determine the eviscerated weight.The complete left pectoralis major muscle was isolated along the midline of the goose sternum, and the complete left thigh muscle was isolated along the goose tibia.These isolated muscles were weighed, bagged, and stored at 4°C for subsequent testing.The contents of the goose cecum were placed in 2 ml EP tubes, quick-frozen in liquid nitrogen, and stored at −80°C

Feeding cost and economic benefit
According to the FBW and ADFI data provided in Table 3, the Carcass yield and Eviscerated carcass yield data are found in Table 4, while the gizzard yield and liver yield data are given in Table 5.A preliminary estimate of the feed cost and meat production benefit for a single test goose was made using the following calculation method:

Statistical analysis
The experimental data were processed using Microsoft Excel 2003 (Redmond, Washington, USA).One-way analysis of variance was conducted using SPSS software version 19.0 (Chicago, IL, USA) to test for significant differences between groups using the Duncan multiple range test.The results were expressed as mean ± standard error (Mean ± SEM) and a P-value of less than 0.05 was considered statistically significant.The data were modeled using the following equation: Where: Y ijk = dependent variable, μ = overall mean value, τ j = fixed effect of the j th of τ factor, and e ijk = residual value from unpredictable error.Sτ ij and S i are taken to be independent variables that are chosen at random (Sholikin et al., 2023).Therefore, the validation test was conducted using the root mean square error (RMSE) following (Adli et al., 2023).

RMSE ¼
ffi ffi ffi ffi ffi ffi ffi ffi ffi ffi ffi ffi is the sum of all variants of the component, σ 2 e is the variant due to the predictor dispersion and σ 2 d is the specific distribution of the variant.

Growth performance
Results of growth performance are shown in Table 3.The initial body weight (IBW) of geese in each group was not significantly different (P > 0.05).The FBW and ADG of geese in the 50SM group were significantly lower than in the other groups (P < 0.001).The FCR of the control group was significantly lower compared to the other groups (P < 0.001), and the FCR of the 50SM group was significantly higher compared to the 15SM and 30SM groups (P < 0.001).The average daily feed intake (ADFI) of geese in the control group was significantly lower compared to the 15SM, 30SM and 50SM groups (P < 0.001).

Carcass traits and relative organ weight
The results of carcass traits are shown in Table 4.The abdominal fat yield of geese in the 50SM group was significantly lower than that in the other groups (P < 0.05).The results of the organ relative weight are shown in Table 5.The gizzard yield of geese in the 0SM group was significantly lower than that in the other groups (P < 0.01).

Biochemical indicators
The results of the serum biochemical indicators are shown in Table 6.The blood urea nitrogen (BUN) levels in the control group were significantly higher than those in the other groups (P < 0.001).The total triglycerides (TG) level in the control group was significantly higher than those in the 30SM and 50SM groups (P < 0.001).

Economical traits
The results of the breeding cost and economic benefit analysis for the test geese are presented in Table 7.
As shown, the 30SM group exhibits the highest economic benefit, with a single goose yielding an income of 1.92 $.

Growth performance
As herbivorous waterfowl, geese benefit from consuming an appropriate amount of crude fiber, which promotes intestinal development and reduces the occurrence of diseases (Xi et al., 2022).
According to (Ardiansyah et al., 2022), the digestive characteristics and physiological structure of geese enable them to effectively digest plant cell walls.(Li et al., 2017) found that controlling the dietary crude fiber level at 6.1% significantly improves the FBW and ADG of geese, but reduces the ADFI.(Zhou et al., 2018) observed that when the dietary crude fiber level reaches 8.1%, the ADFI of Carlos geese significantly increases.Furthermore, (Liu et al., 2007) discovered that as the dietary crude fiber level increases, the ADFI of geese increases, while ADG initially increases and then decreases.The results of this experiment demonstrate that substituting whole-plant silage maize for commercial feed significantly increases the ADFI and FCR of geese.However, when the proportion of whole-plant silage maize substitution exceeds 50%, the growth performance of geese is affected, resulting in a significant decrease in body weight and daily weight gain.This finding aligns with the study conducted by (Fox et al., 2017).The possible reason for this phenomenon may be the unique aromatic scent of whole-plant silage maize, which attracts geese to feed on it.Additionally, as herbivorous waterfowl, geese require an appropriate level of crude fiber (5% ~7%) in their diet, which is fulfilled by the inclusion of whole-plant silage maize, thereby increasing their feed intake.However, excessive substitution of whole-plant silage maize can disrupt the uniformity and nutritional concentration of the feed mixture.Table 1 indicates that as the proportion of whole-plant silage maize substitution increases, the CP and ME content in the diet decreases, resulting in reduced absorption and utilization of nutrients by geese.Consequently, geese may need to increase their feed intake to meet their normal physiological metabolic needs, leading to an increase in feed intake but slower body weight growth rate (Zhang et al., 2013).

Carcase yield and relative organ weight
The efficiency of meat production in livestock is influenced by the deposition of nutrients in animal muscle tissue and the weight of the carcass and muscle tissue.The goose gizzard, which is an important internal organ in meat geese, plays a significant role in evaluating the economic benefits of meat goose farming.(Kokoszyński et al., 2014) conducted a study which showed that adding silage maize to the diet of White Kołuda W31 geese increased the weight of the leg muscles and reduced subcutaneous fat.However, (Aslan & Öztürk, 2022) found that supplementing with silage maize had no significant impact on the weight of the carcass, liver, gizzard, abdominal fat, or the proportion of turkey geese.The results of the study showed that, feeding whole-plant silage maize to geese resulted in an increase the proportion of goose gizzards and a decrease in abdominal fat compared to the control group.The relative carcass weight of the geese in the 30SM group also increased significantly.However there was no significant impact on muscle surface color or weight.It was observed that goose gizzards play a crucial role in grinding and digesting plant cell walls.As silage maize is rich in crude fiber, geese require more developed gizzards to process it (Yu et al., 2022).Therefore, the proportion of gizzards in experimental geese was positively correlated with the proportion of silage maize in their diet.Compared to concentrated feed, silage maize feed has a higher amount of crude fiber which is only present in the goose intestine for a short period of time.This can limit the production of glucose and fatty acids, which are primarily used to sustain the life activities of the goose.Only a small portion of these fatty acids and glucose contribute to fat synthesis.Therefore, the replacement ratio of whole-plant silage maize is negatively correlated with the abdominal fat ratio of geese (Gruber et al., 2018).

Blood biochemical
Animal metabolic by-products enter the bloodstream, and the serum's biochemical parameters can indicate the animal's health and metabolism (F.Chen et al., 2022).BUN is a product of protein metabolism and its levels can increase due to a high-protein diet and high catabolic state (Yu et al., 2019).The study showed that replacing 15% to 30% of whole-plant silage maize in the goose diet reduced BUN levels, but increasing the replacement ratio to 50% caused, the BUN levels rise again.This may be due to geese having lower digestibility of protein form whole-plant silage maize compared to feed maize, resulting in reduced protein content involved in BUN production and subsequently lowering BUN levels.When geese consume a high level of whole-plant silage maize, they need to maintain a higher catabolic state in order to fully digest and break down the maize to meet their nutritional requirements.This elevated catabolic state can lead to an increase in BUN levels.The lipid metabolism of geese can be measured by TC, TG, HDL-C, and LDL-C.This research showed that feeding geese with whole-plant silage maize increased their TC, HDL-C, and LDL-C levels, but     there was no significant difference.However, when the replacement ratio of whole-plant silage maize reached 30-50%, the serum TG levels in geese significantly decreased.This reduction may be attributed to a lower efficiency of geese in digesting and utilizing wholeplant silage maize.A high replacement ratio leads to a slower rate of energy generation from the digestion of whole-plant silage maize in geese, resulting in a reduced surplus energy available for TG synthesis.As a result, the TG levels in the experimental group decreased.In contrast, the control group had a higher surplus energy available for TG synthesis in the liver, and the synthesized TG combined with cholesterol (TC) to be transported and stored in Means with different superscript letters in the same row differ extremely significantly (P ≤0.01).TP: total protein, AST: aspartate aminotransferase, ALT: alanine aminotransferase, AKP: alkaline phosphatase, ALB: albumin, GLOB: globulin, BUN: blood urea nitrogen, GLU: glucose, TC: total cholesterol, TG: total triglycerides, HDL-C: high-density lipoprotein cholesterol, LDL-C: low-density lipoprotein cholesterol extraliver tissues, forming adipocytes.The relatively higher serum TC levels in the experimental group may be a result of TC being consumed during the formation, transport, and storage processes of triglycerides (Wei et al., 2022).The decrease in relative abdominal fat weight in the experimental group supports this explanation.

Economical traits
The cost of goose seedlings and feed are the primary drivers of meat goose production cost, accounting for around 35% and 60% of the production cost, respectively.As the price of goose seedlings is subject to market fluctuations, reducing the cost of feed is crucial to enhance the economic efficiency of meat goose production.Our experiment showed that substituting commercial feed with whole-plant silage maize is an effective strategy.However, it is essential to note that excessive or inadequate substitution ratios of whole-plant silage maize can have negative impacts.A low substitution ratio increases feed consumption and costs, while a high ratio reduces the absorption and utilization efficiency of nutrients in the feed, thus affecting the normal growth of geese.After careful consideration, we determined that a 30% substitution ratio provides the optimal balance between reducing production costs and promoting normal growth, while also increasing the yield of highly valued goose gizzards in the Chinese market.

Conclusion
Overall, using whole-plant silage maize as a substitute for commercial feed in the diet is an effective way to increase the economic benefits of broiler goose production.However, it is crucial to monitor the proportion of whole-plant silage maize substitution, with 30% proportion yielding the maximum benefit.

Feed
Cost = Unit Price of Whole-Plant Silage Maize Feed (kg) x Replacement Ratio of Whole-Plant Silage Maize x ADFI (kg) x Feeding Days + ADFI (kg) x Commercial Feed Ratio x Feeding Days x Commercial Feed Unit Price (kg) Meat Production Benefit = Eviscerated Carcass Yield x FBW (kg) x Unit Price of Goose Meat (kg) + Gizzard Yield x Carcass Yield x FBW (kg) x Unit Price of Liver (kg) + Liver Yield x Carcass Yield x FBW (kg) x Unit Price of Liver (kg) Feeding Cost = Feed Cost + Cost of a Single Gosling Economic Benefit = Meat Production Benefit-Feeding Cost

Table 1 . Ingredients and nutrient compositions of experimental diets
1Analyzed values given for metabolizable energy (ME), crude protein (CP), crude fiber (CF), and available phosphorus (P).Calculated values given for lysine, methionine, cysteine, and arginine.

Table 3 . Effects of whole-plant silage maize replacing commercial feed on the growth per- formance of Holdobaki geese
Means with different superscript letters in the same row with significance different (P < 0.01).IBW: Initial Body Weight, FBW: Final Body Weight, ADG: Average daily gain, FCR: Feed Conversion Ratio ADFI: Average Daily Feed Intake

Table 6 . Effects of whole-plant silage maize replacing commercial feed on the blood bio- chemical of Holdobaki geese
A-B