Effects of different feeding methods on growth and slaughter performance, blood biochemical indexes and intestinal morphology in Minxinan black rabbits

doi:10.21203/rs.3.rs-1751532/v1

Feed restriction after weaning is a common strategy in commercial rabbit farms to improve feed efficiency, promote health and to reduce mortality. However, no study has been published on Minxinan black rabbits. The effects of feed restriction on growth and slaughter performance, intestinal morphology and serum biochemical indexes of Minxinan black rabbits were evaluated in this study. Rabbits in group A (control group) ad libitum intake, the others in feed restriction groups (groups B, C and D) were restricted by 80% of the average daily feed intake of group A the day before. The experimental period lasted 8 weeks. The results indicated that, compared with group A, diarrhea rate of feed restriction groups C was significantly decreased (P < 0.05), the average daily feed intake (ADFI), feed/gain (F/G), abdominal fat weight, abdominal fat rate, the contents of total protein (TP), albumin (ALB), globulin (GLB), alanine aminotransferase (ALT), Low density lipoprotein (LDL) and intestinal crypt depth of feed restriction groups were significantly reduced (P < 0.01). F/G of group D was significantly lower than that of groups B and C (P < 0.05). Efficiency index (EEI) of groups C and D were higher than of groups A and B (P < 0.01). Triglyceride (TG) of groups C and D were significantly lower than group A (P < 0.01). The V/C of duodenum and jejunum of group D was significantly higher than that of group A (P < 0.01). In conclusion, the F/G, diarrhea rate, abdominal fat rate, serum ALT and lipid indexes of Minxinan black rabbits can be reduced, EI and intestinal health can be improved by feed restriction. Feeding twice a day, 30% at 8:00am and 70% at 4:00pm has the best comprehensive effects.

Minxinan black rabbits

Feed restriction

Growth and slaughter performance

Blood biochemistry

Intestinal morphology

Feed restriction programs has been used in post-weaning animals for improving feed efficiency and resistance to digestive system disorders, reducing carcass fat and production costs (Tumova et al. 2021). Study on feed restriction in pigs (Le Floc'h et al. 2014), broilers (van der Klein et al. 2017), sheep (Lima et al. 2022) show that animals can compensate for growth inhibition caused by feed restriction by improving feed efficiency. Feed restriction can be used to reduce morbidity and mortality in growing rabbits (Boisot, Licois, and Gidenne 2003; Gidenne et al. 2009; De Blas 2013), and to improve farm feed efficiency (Knudsen et al. 2014; Birolo et al. 2020a), and to reduce nitrogen emissions and environmental pollution (Birolo et al. 2016; Birolo et al. 2017). It is suggested to reduce rabbit feed intake by at least 20% of ad libitum to reduce post-weaning mortality and 30% to reduce morbidity (Gidenne et al. 2009; Gidenne and Feugier 2009). Time-based feed restriction significantly improved the feed conversion ratio of rabbits and promoted their health (Birolo et al. 2020a, 2020b; Crespo et al. 2020).

Rabbit industry is important in China, its breeding volume and export volume are the world's first, meat rabbit export volume accounted for 27% of the world (Cullere and Dalle Zotte 2018). At present, there is no uniform feed restriction program for rabbits in farm, and the effects of feed intake restriction and time-based feed restriction on local meat rabbits in China have not been reported. Minxinan black rabbit is a genetic resource of livestock and poultry in China. Minxinan black rabbit which is the excellent local breed in Fujian Province has better meat quality, strong adversity resistance and extensive adaptability. The diarrhea rate and mortality of rabbits after weaning are high, which seriously affect the development of meat rabbit industry. Feed restriction plays an important role in reducing production costs and improving feed efficiency in many animals after weaning. However, feed restriction in Minxinan black rabbit has not been described to date.

Therefore, this experiment was conducted to study the effects of four feeding methods on growth and slaughter performance, blood biochemical indexes and intestinal structure of Minxinan black rabbits, and to provide reference for selecting appropriate feeding methods in production.

Animal resource, diets, and feeding programs

The experiment was conducted in the animal house, institute of animal husbandry and veterinary medicine, Fujian academy of agricultural sciences, China. Each rabbit cage size 42cm×50cm×35cm, single cage feeding, ad libitum water. The diets were pellet diets with the following nutrient levels: DE 10.5~10.8 MJ/kg, CP 16.5~17.0 %, CF 14.5~ 16.0 %. The experimental period lasted 61 days, including 5 days of pre-feeding period and 56 days of formal experimental period. A total of 144 Minxinan black form Longyan City Tongxian Rabbit Industry Development Co., LTD with healthy and similar body weight at the age of 30 days were randomly divided into 4 groups with 3 replicates per group and 12 rabbits per replicate (half male and half female). Control group (A group) ad libitum intake, the others three groups (B, C, D) were restricted by 80% of the average daily feed intake of group A the day before. Rabbits in groups B were fed once a day 8:00am. Rabbits in groups C and D were fed twice a day 8:00am 50% 4:00pm 50%, 8:00am 30% 4:00 pm 70%, respectively.

Sample collection and indexes determination

Growth performance

Individual live weight was recorded at the beginning (initial body weight, IBW) and at the end of the experiment (final body weight, FBW) in the morning before feeding. During the whole experiment, rabbit health was monitored daily. The diarrhea rate and mortality rate were recorded daily. Feed intake was measured daily by weighing the feed supplied and refused. The average daily gain (ADG), ADFI, F/G and EI from 5 to 13 weeks were calculated respectively.

ADG（g/d）=（FBW - IBW）/Test days；

ADFI（g/d）=Total feed intake/（Test days×Number of test animals）；

F/G= ADFI / ADG；

Diarrhea rate（%）=（Number of diarrhea / Total number of rabbits tested）×100；

Mortality rate（%）=（number of mortality/Total number of rabbits tested）×100。

EI= (FBW× survival rate) / (feed conversion ratio× on sale day)

Slaughter performance

A total of 18 healthy 13-week-old rabbits in each group with 6 rabbits per replicate (half male and half female) were slaughtered. The slaughter process was carried out as the World Rabbit Science Association recommendations (Blasco A. and J. Ouhayoun, 1996). Pre-slaughter body weight, all carcass weight, half carcass weight and abdominal fat weight were measured. All eviscerated ratio, half eviscerated ratio and abdominal fat rate were calculated respectively. All eviscerated weight is the carcass weight after slaughter, excluding blood, fur, head, tail, limbs (below wrist and hock) and viscera. Half carcass weight is the carcass weight plus heart, liver, kidney and abdominal fat.

All eviscerated ratio（%）= All carcass weight / Pre-slaughter body weight×100；

Half eviscerated ratio（%）= Half carcass weight / Pre-slaughter body weight×100；

Abdominal fat rate（%）= Abdominal fat weight / Pre-slaughter body weight×100。

Blood biochemical indexes

Blood samples of 2 ml were obtained from precaval vein of 18 rabbits/group (9 males and 9 females) at 13 week old. The samples were injected into tubes and allowed to coagulate for 30 min before centrifugation at 3500g for 15 min. The isolated plasma samples were then stored at −80°C until analysis. Blood biochemical indexes were determined by BECKMAN AU2700 automatic biochemical analyzer

Intestinal morphology

After fasting slaughter in the morning of the end of the experiment, 1.0-1.5 cm of intestinal tubes in the middle parts of duodenum and jejunum were cut out, and the intestinal contents were washed with normal saline until clean, and placed in formalin fixed solution. After paraffin embedding and HE staining, image-Pro Plus 6.0 software was used to select 5 complete villi from each section. Villi height and crypt depth were measured for 5 times respectively, and their average value was calculated.

Statistical analysis

Excel 2010 and SPSS 20.0 statistical software were used to process and analyze the data. One-way ANOVA and Tukey multiple comparison method were used to test the significance of differences between groups. P>0.05 was insignificant, P<0.05 was significant, and P<0.01 was extremely significant. Data are expressed as mean ± standard deviation.

Growth performance and health status

There was no significant difference in IBW among all groups (P > 0.05). From 5 to 13 weeks, the FBW, ADG, ADFI and F/G of feed restriction groups were significantly lower than those of control group A (P < 0.01). The FBW and ADG of group D were the highest, and the F/G of group D was lowest among groups. From 5 to 13 weeks, the diarrhea rate of group A was the highest (25.00%), followed by group B (19.44%), group C (8.33%) and group D (8.33%) which was significantly lower than that of group A (P < 0.05). There was no significant difference in mortality rate among all groups (P > 0.05). EI of groups C and D were higher than of groups A and B (P < 0.01). (Table 1).

Table 1

Effects of different feeding methods on growth performance of Minxinan black rabbits
Trait	Groups				P-value
Trait	A	B	C	D	P-value
IBW(g)	537.56 ± 45.79	545.35 ± 49.50	533.94 ± 50.01	534.33 ± 34.91	0.692
FBW(g)	1737.21 ± 105.75^Aa	1641.42 ± 81.25^Bb	1638.42 ± 74.32^Bb	1654.22 ± 66.47^Bb	<0.001
ADG (g/d)	21.41 ± 0.30^Aa	19.58 ± 0.51^Bb	19.72 ± 0.37^Bb	20.00 ± 0.22^Bb	<0.001
ADFI(g/d)	107.07 ± 0.61^Aa	86.49 ± 1.24^Bb	86.61 ± 0.93^Bb	85.54 ± 0.87^Bb	<0.001
F/G	5.00 ± 0.04^Aa	4.42 ± 0.06^Bb	4.39 ± 0.13^Bb	4.28 ± 0.03^Bb	<0.001
Diarrhea rate(%)	25.00 ± 8.33^Aa	19.44 ± 4.81^Aab	8.33 ± 0.00^Ab	8.33 ± 8.33^Ab	0.029
Mortality rate(%)	5.56 ± 4.81	8.33 ± 0.00	2.78 ± 4.81	5.56 ± 4.81	0.487
EI	360.45 ± 4.21^Bb	373.85 ± 4.44^Bb	398.77 ± 8.80^Aa	401.41 ± 2.68^Aa	<0.001
SDM, standard deviation of the mean; IBW, initial body weight; FBW, final body weight; ADG, average daily gain; ADFI, average daily feed intake; F/G, feed/gain; EI, efficiency index. In the same line, values with no letter or the same letter superscripts mean no significant difference (P>0.05), while with different small letter superscripts mean significant difference (P<0.05), and with different capital letter superscripts mean significant difference (P<0.01) by the Tukey test.

Slaughter traits

The pre-slaughter weight, all carcass weight, half carcass weight, abdominal fat weight and abdominal fat rate of feed restriction groups B, C and D were significantly lower than those of group A (P < 0.01), but there were no significant differences in all eviscerated ratio and half eviscerated ratio among all groups (P > 0.05) (Table 2).

Table 2

Effects of different feeding methods on slaughter performance of Minxinan black rabbits
Trait	Mean ± SDM				P-value
Trait	Group A	Group B	Group C	Group D	P-value
Pre-slaughter weight (g)	1731.93 ± 46.92^Aa	1640.97 ± 44.31^Bb	1634.64 ± 33.57^Bb	1643.56 ± 32.69^Bb	<0.001
All carcass weight (g)	877.55 ± 41.09 ^Aa	848.9 ± 32.31^ABab	838.75 ± 31.36^Bb	833.69 ± 26.05^Bb	<0.001
All eviscerated ratio (%)	50.66 ± 1.69	51.74 ± 1.61	51.31 ± 1.53	50.72 ± 1.19	0.124
Half carcass weight (g)	978.39 ± 46.66 ^Aa	925.5 ± 27.81^Bb	917.75 ± 32.47^Bb	912.44 ± 26.95^Bb	<0.001
Half eviscerated ratio (%)	56.48 ± 1.91	56.41 ± 1.52	56.14 ± 1.49	55.51 ± 1.12	0.231
Abdominal fat weight (g)	21.58 ± 2.19 ^Aa	16.03 ± 0.65^Bb	16.08 ± 0.43^Bb	16.03 ± 0.44^Bb	<0.001
Abdominal fat rate (%)	1.24 ± 0.11 ^Aa	0.98 ± 0.03^Bb	0.98 ± 0.02^Bb	0.98 ± 0.02^Bb	<0.001
SDM, standard deviation of the mean; In the same line, values with no letter or the same letter superscripts mean no significant difference (P>0.05), while with different small letter superscripts mean significant difference (P<0.05), and with different capital letter superscripts mean significant difference (P<0.01) by the Tukey test.

Blood biochemical indexes

As shown in Table 3, the contents of TP, ALB, GLB and ALT of group A were significantly higher than those of feed restriction groups (P < 0.01). There were no significant differences in glutamyltranspeptidase (GGT), total cholesterol (CHOL) and high density lipoprotein (HDL) among groups (P > 0.05). Triglyceride (TG) of group A was significantly higher than that of group B (0.96 VS 0.82 mmol/L, P < 0.05) and extremely significantly higher that of groups C and D (0.96 VS 0.63 and 0.54 mmol/L, P < 0.01). Low density lipoprotein (LDL) of group A was extremely significantly higher than that of feed restriction groups (P < 0.01), and there was no significant difference among feed restriction groups (P > 0.05).

Table 3

Effects of different feeding methods on blood biochemical indexes of Minxinan black rabbits
Trait	Mean ± SDM				P-value
Trait	Group A	Group B	Group C	Group D	P-value
TP(g/L)	56.47 ± 2.51^Aa	38.29 ± 4.69^Cc	42.39 ± 6.62^Bb	39.97 ± 3.80^BCbc	<0.001
ALB(g/L)	34.50 ± 1.40^Aa	26.50 ± 2.27^Bb	27.97 ± 3.24^Bb	26.93 ± 2.00^Bb	<0.001
GLB(g/L)	21.98 ± 1.89^Aa	11.79 ± 2.81^Cc	14.41 ± 3.83^Bb	13.04 ± 6.51^BCbc	<0.001
ALT(U/L)	63.78 ± 11.80^Aa	48.14 ± 16.86^Bb	47.63 ± 12.33^Bb	45.80 ± 10.44^Bb	<0.001
GGT(U/L)	7.53 ± 1.60	7.02 ± 1.91	6.64 ± 2.20	7.13 ± 1.69	0.270
CHOL( mmol/L)	1.49 ± 0.73	1.32 ± 0.59	1.44 ± 0.63	1.50 ± 0.64	0.649
TG( mmol/L)	0.96 ± 0.27^Aa	0.82 ± 0.27^Ab	0.63 ± 0.17^Bc	0.54 ± 0.15^Bc	<0.001
HDL( mmol/L)	0.68 ± 0.15	0.71 ± 0.10	0.72 ± 0.15	0.73 ± 0.17	0.558
LDL( mmol/L)	0.47 ± 0.04^Aa	0.42 ± 0.04^Bb	0.41 ± 0.05^Bb	0.39 ± 0.04^Bb	<0.001
SDM, standard deviation of the mean; In the same line, values with no letter or the same letter superscripts mean no significant difference (P>0.05), while with different small letter superscripts mean significant difference (P<0.05), and with different capital letter superscripts mean significant difference (P<0.01) by the Tukey test.

Intestinal morphology

The villus length of duodenum in group A was extremely significantly lower than that in groups C and D (P < 0.01). The villus length of jejunum in group A was lower than that in group C (P < 0.01). The crypt depth of group A was significantly higher than that of feed restriction groups (P < 0.01), and that of group B was significantly lower than that of group C (P < 0.05). There was no significant difference in duodenal crypt depth among all groups (P > 0.05).The ratio of villus length to crypt depth (V/C) of duodenum and jejunum in group D was significantly higher than that in group A (P < 0.01) (Table 4 and Fig. 1).

Table 4

Effects of different feeding methods on intestinal morphology of Minxinan black rabbits
Trait	Tissue	Mean ± SDM
Trait	Tissue	Group A	Group B	Group C	Group D	P-value
Villus length(µm)	Duodenum	895.41 ± 68.70^Cc	932.93 ± 78.57^BCbc	995.66 ± 78.61^ABab	1048.54 ± 117.84^Aa	<0.001
	Jejunum	633.58 ± 124.75^ABbc	595.61 ± 116.15^Bc	714.75 ± 113.60^Aa	705.82 ± 125^Aab	<0.001
Crypt depth(µm)	Duodenum	254.91 ± 98.70	217.74 ± 79.47	227.8 ± 55.89	209.89 ± 80.47	0.103
	Jejunum	177.70 ± 43.98^Aa	106.65 ± 24.70^Cc	139.23 ± 45.05^Bb	115.38 ± 23.51^BCc	<0.001
V/C	Duodenum	3.88 ± 1.63^Bb	4.88 ± 1.89^ABab	4.67 ± 1.38^ABab	5.57 ± 1.74^Aa	0.006
	Jejunum	3.82 ± 1.28^Bb	5.87 ± 1.71^Aa	5.57 ± 1.91^Aa	6.38 ± 1.82^Aa	<0.001
SDM, standard deviation of the mean; V/C, Villus length/Crypt depth. In the same line, values with no letter or the same letter superscripts mean no significant difference (P>0.05), while with different small letter superscripts mean significant difference (P<0.05), and with different capital letter superscripts mean significant difference (P<0.01) by the Tukey test.

The diet controlled at 95% ad libitum feed intake did not affect growth performance and slaughter performance of growing rabbits, and 85% did not affect growth rate, and the feed conversion ratio remained unchanged (Romero et al. 2010). Diarrhea rate and mortality rate of post-weaning rabbits can be reduced only when the intake is controlled at less 80% of ad libitum intake, with little impact on growth performance and slaughter performance (Gidenne and Feugier 2009). However, the protective effect of feed restriction on intestinal health has been found, which disappears after the resumption of ad libitum feeding (Knudsen et al. 2014; Alabiso et al. 2017). The sudden resumption of ad libitum feeding from feed restriction usually leads to the peak of feed intake and then the peak of digestive tract diseases. (Akbarian et al. 2014; Knudsen et al. 2014). The method of gradual transition from feed restriction to ad libitum feeding can prevent excessive feeding and waste of diet after resuming ad libitum feeding, and the intake peak and excessive consumption of diet in fattening stage (Birolo et al. 2020b), but method of gradual transition is cumbersome to use.

In this trail, from 5 to 13 weeks control group A ad libitum intake and the other three groups were restricted 80% of ad libitum intake in group A the day before. The diarrhea rate of group A was the highest (25.00%) among groups, and significantly higher than that of group C (P < 0.05). Mortality was similar among all groups (5.56% on average), and any restriction strategy does not significantly reduced it.There was no significant difference in mortality rate among all groups (P > 0.05), which was consistent with previous studies (Gidenne and Feugier 2009) that feed restriction could reduce diarrhea rate. In fact, some studies showed that post-weaning rabbits which were restricted feeding can reduce morbidity and mortality (Gidenne and Feugier 2009; Knudsen et al. 2014; Birolo et al. 2016; Knudsen et al. 2017), but in other studies feed restriction even tended to increase rabbit’s mortality rate (Birolo et al., 2020). There is no clear explanation for the differences among studies and a combination of factors such as diet, farm health status, methods of feed restriction used, or housing type might be behind them.

The FBW, ADFI, ADG and F/G of feed restriction groups B, C and D were significantly lower than those of group A (P < 0.01). Among the feed restriction groups, the FBW, ADG and EI of group D were the highest, and the F/G of group D was significantly lower than that of groups B and C (P < 0.05). These results indicated that the feed restriction of 80% free feed intake can reduced diarrhea rate and increased feed conversion ratio, and growth rate was affected which could be compensated by reducing diarrhea rate. The EI is a comprehensive measure of rabbit production, reflecting various indicators of a rabbit flock including body weight, survival rate, feed conversion ratio, production management, etc. It's also a profit indicator, and the bigger the index, the bigger the profit. EI of groups C and D were higher than of groups A and B (P < 0.01).

Slaughter performance reflects the deposition and distribution of nutrients in different parts of meat rabbits. All carcass weight, all eviscerated ratio, half carcass weight and half eviscerated ratio are important indicators to measure slaughter performance of meat rabbits, and their levels are closely related to dietary nutrition level. In this trial, the pre-slaughter weight, all carcass weight, half carcass weight, abdominal fat weight and abdominal fat percentage in restricted feeding groups were significantly lower than those in group A (P < 0.01), but all eviscerated ratio and half eviscerated ratio were not significantly different from those in group A (P > 0.05). This may be due to the relatively balanced development rate of all parts of the Minxinan body during the growth stage (from weaning to market). This indicates that feed restriction of 80% free feed intake with different methods has no effect on slaughter rate, which is consistent with other authors found no effect (Birolo et al. 2020a). Knudsen et al. found that the slaughter rate of growing rabbits was significantly reduced when growing rabbits were fed at 75% free feed intake for 4 weeks (Knudsen et al. 2017). Feed restriction significantly reduced the percentage of perirenal fat (Tumova et al. 2021; Tůmová et al. 2021). In this experiment, the abdominal fat weight and abdominal fat percentage in feed restriction groups were significantly lower than those in ad libitum feeding group A.

The gut is an important defense barrier for human and animals (Yang et al. 2019). The small intestine is a tissue of digestion and absorption, and the integrity of its mucosal morphology reflects the digestion and absorption of diet. The length of villi and crypt depth are the most direct indicators of the morphological integrity of small intestine mucosa. The longer length of villi in the small intestine means the larger absorption area, the stronger absorption and utilization of nutrients. Intestinal crypt depth reflects the maturity rate of epithelial cells. The shallower the crypt, the better the digestion and absorption function. In this experiment, Crypt depth of jejunum in feed restriction groups were significantly lower than group A (P < 0.01). The villus length of duodenum in group D was significantly than that in group A. The V/C of duodenum and jejunum in group D were significantly higher than that in group A (P < 0.01). The results showed that group D had the best intestinal improvement effect and was beneficial to improve the absorption and utilization of feed nutrients.

Serum biochemical indexes can reflect the metabolic status of animal body physiology (Ewuola 2008). Serum total protein and albumin contents mainly reflect the absorption, synthesis and decomposition of protein. Serum globulin is a mixture of a variety of proteins, including immunoglobulin and complement, and a variety of glycoproteins. In this experiment, the contents of TP, ALB and GLB in group A were significantly higher than those in feed restriction groups (P < 0.01), indicating that feed restriction of 80% free feed intake reduced protein absorption. Serum ALT is an important indicator to judge liver function. Under normal physiological conditions ALT activity is low. Only when the permeability of tissue cells increases or is damaged, its activity will increase, and then enter the blood, increasing the content of ALT in serum. The results of this study showed that ALT of feed restriction groups were significantly lower than that of group A (P < 0.01), therefore feed restriction reduced ALT and had protective effect on liver function. Feed restriction has no adverse effect on liver cells of fattening pigs (Batorek et al. 2012). The contents of CHOL, TG, HDL and LDL in serum can reflect the lipid metabolism of the body. The decrease of CHOL, TG and LDL is beneficial to prevent hyperlipidemia. There were no significant differences in CHOL and HDL among all groups (P > 0.05) in the trial. TG in groups C and D was significantly lower than that in groups A and B (P < 0.01), the reason may was the energy intake of rabbits in the feed restriction groups could not meet the needs of the body, which would lead to decrease in the metabolic rate, and the serum TG needed to be transported to various tissues and organs for oxidation for energy. In this study, LDL in feed restriction groups were significantly lower than that in group A (P < 0.01), indicating that feed restriction reduced serum LDL content, which was consistent with the results of other authors (Xu 2017).

The feed restriction of 80% free feed intake can improve the intestinal morphology of Minxinan black rabbits, promote the intestinal health, increase economic index, decrease the serum lipid content, feed to gain ratio, diarrhea rate, and the feed restriction method of feeding twice every day (fed 30% at 08:00 and 70% at 16:00) has the best comprehensive effects.

Funding

This research was supported by the National Modern Agricultural Industrial Technology System construction Project (CARS-43-G-5, China).

Author contributions

X.P. contributed to the conception of the study; D.J., S.K., Y.F. performed the experiment; D.J., X.P., performed the data analyses and wrote the manuscript; J.X., L., C.F. helped perform the analysis with constructive discussions. All authors read and approved the manuscript.

Acknowledgements

The authors are thankful to the Tongxian ranch in FuJian for the rabbit support for this experiment. We are particularly grateful to Mr. Gan Qianfu and Mr. Wu Xun for their support and help in the process of analysis.

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.

Ethics statement

All procedures involving animals followed the guidelines for the care and use of experimental animals approved by the State Council of the People’s Republic of China.

Data Availability Statements

The data that support the findings of this study are available from the corresponding author upon reasonable request.

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Effects of different feeding methods on growth and slaughter performance, blood biochemical indexes and intestinal morphology in Minxinan black rabbits

Status:

Journal Publication

Version 1

Abstract

Figures

Introduction

Materials And Methods

Animal resource, diets, and feeding programs

Sample collection and indexes determination

Growth performance

Slaughter performance

Blood biochemical indexes

Intestinal morphology

Statistical analysis

Results

Growth performance and health status

Slaughter traits

Blood biochemical indexes

Intestinal morphology

Discussion

Conclusion

Declarations

References

Status:

Journal Publication

Version 1