Effects of particle size of corn and stocking densities on the performance, carcass traits and gastrointestinal tract development of Muscovy ducks in housing

doi:10.21203/rs.3.rs-3228937/v1

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Effects of particle size of corn and stocking densities on the performance, carcass traits and gastrointestinal tract development of Muscovy ducks in housing

https://doi.org/10.21203/rs.3.rs-3228937/v1

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published 14 Dec, 2023

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The current investigation was conducted to investigate the effects of different particle sizes of corn and stocking densities on performance, carcass traits and gastrointestinal tract (GIT) development of Muscovy ducks in housing. 200 Muscovy ducks were distributed in a factorial scheme (2x2) where the treatments were constituted by two stocking densities (2 or 3 birds/m²) and two particle sizes of corn (6 or 8 mm), with five replicated of 10 birds each. At 1, 35, 70, and 90 days old, Muscovy ducks were slaughtered using cervical dislocation method to evaluate the development of heart and GIT. Muscovy ducks managed in the density of 3 birds/m² presented higher (P < 0.05) GIT development, performance and carcass traits regardless of age evaluated. In the same way, Muscovy ducks fed diets using a particle size of corn of 6 mm (Mean Geometric Diameter (MGD) = 781 µm) presented higher (P < 0.05) GIT development, performance and carcass traits regardless of age evaluated. Conclusively, the stocking density of 3 birds/m² and the particle size of corn of 6 mm (MGD = 781 µm) were considered ideal recommendations for Muscovy ducks, providing higher GIT development, which resulted in better performance and carcass traits.

Cairina moschata domesticus

feed efficiency

gastrointestinal tract

Muscovy duck

waterfowl

Muscovy ducks (Cairina moschata domesticus) are native birds from Central and South America (Rodenburg et al., 2005; Scanes and Christensen, 2020), regions characterized by presenting a very developed agribusiness and focusing on poultry production on a large scale (Cruz and Rufino, 2017). However, Muscovy ducks is a little explored species in this production chain by local producers. In Brazil, for example, the literature reported that the low production and development of the local Muscovy ducks production is related to the little specific information on this species, such as adequate nutritional requirements, facilities, management and meat processing protocols among others (Gois et al., 2012; Rufino et al., 2015; Rufino et al., 2017a,b). This is also a reflection of world literature, where almost all the literature on ducks is directed to common ducks (Anas platyrhynchos), mainly Pekin ducks (Shalev, 1995; Rodenburg et al., 2005; Jalaludeen et al., 2022).

The few studies related to the management of Muscovy ducks using different stocking densities are characterized by an expressive variation in their recommendations (Coates and Ernst, 2000; Moreira, 1993; Cruz et al., 2013; Rufino et al., 2017a,b; Bawish et al., 2018). Coates and Ernst (2000), for example, suggested a density of 2 birds/m² for Muscovy ducks at two weeks-age in housing, decreasing to 1 bird/m² from two to four weeks-age, and ½ bird/m² after one month-age. Moreira (1993) recommended a density of 1 bird/m² for Muscovy ducks from 3.0 to 3.5 kg (females) and 4.5 to 5.5 kg (males) in a free-range system, where the slaughter age varies between three to six months. Cruz et al. (2013) reported that Muscovy ducks in housing may be managed using 4 birds/m² for up to 90 days, presenting good performance and carcass traits, while Rufino et al. (2017a) also observed great performance and carcass traits for Muscovy ducks in housing until to 90 days but using between 2 and 3 birds/m².

Relating these basic stocking management results to those on nutritional management, the literature points out the importance of the size, form and structure of feedstuffs particles to influence the nutrient digestibility by the birds (Hamilton and Proudfoot, 1995; Amerah et al., 2007; Chewning et al., 2012; Cruz and Rufino, 2017; Scanes and Christensen, 2020). Major feedstuffs used in poultry diets are ground, normally using a hammer mill, to facilitate its digestion and absorption in the gastrointestinal tract (GIT) (Reece et al., 1986; Cruz and Rufino, 2017), where the volume:weight ratio and particle size are the principal indexes considered in the process of poultry foods production (Nir et al., 1994a,b).

Considering the above, we hypothesized that the particle size of corn in diets for Muscovy ducks should be larger than the recommendation commonly used in diets for broilers (up to 6 mm) due to the morphophysiological differences between these species, especially the larger digestive system (Rufino et al., 2017a; Scanes and Christensen, 2020). In addition, considering the relationship between stocking density and nutritional management (Cruz et al., 2013; Rufino et al., 2017a; Scanes and Christensen, 2020), we hypothesized that it could have an influence of the particle size of corn and stocking density on the performance, carcass traits and gastrointestinal development of Muscovy ducks in housing. Therefore, the objective of the current study was to investigate the effects of different particle size of corn and stocking densities on performance, carcass traits and GIT development of Muscovy ducks in housing.

The current experiment was conducted at the Research Poultry Farm of the Federal University of Amazonas, University campus located at Manaus city, Amazonas State, Brazil. All experimental procedures were performed according to the Local Experimental Animal Care Committee and were approved by the institutional ethics committee of the Federal University of Amazonas, Brazil.

2.1. Facilities, animals, diets and experimental design

The aviary used had a ceiling height of 3.25 m, with structural adaptations allowing ample ventilation in the environment and completely surrounded by native vegetation (trees and shrubs). The temperature and relative humidity were monitored using a digital thermohydrometer, registering averages of 29.6 ºC and 66%, respectively. During the all-experimental period, the Muscovy ducks were monitored for signs of thermal stress caused by the environment, a situation that was not observed during all this.

Male Muscovy ducks (n = 200) of creole strain (Rufino et al., 2017b) from the Experimental Farm of the Federal University of Amazonas (Manaus, Brazil) were used. First, the male Muscovy ducks with 1 day-old were received and housed until 7 days-old in a protective circle with floor covered by wood shavings, tray-type feeders and cup-type drinkers at a rate of 50 birds/m² with an electric heating source in the center. After this period, the ducks were separated into the proposed treatments into pens presenting 4 m² each, tubular-type feeders, hanging-type drinkers and floor also covered by wood shavings. Experimental management stages were classified into starter (8 to 35 days), grower (36 to 70 days), and finisher (71 to 90 days), where the birds received feed and water ad libitum. A lighting program similar to that used for slow-growing broilers (20 hours light + 4 hours dark) was used (Wu et al., 2022).

Experimental diets (Table 1) were calculated according to the reference values provided by Rostagno et al. (2011), except energy and protein (Rufino et al., 2015), calcium (Feijó et al., 2016), available phosphorus (Costa et al., 2019) and sodium (Santos et al., 2020) that used adequate requirements to Muscovy ducks. The composition of these diets was analyzed to confirm the proximate composition of the diets according to the methods described by the AOAC (2019), where moisture content was determined in an oven at 105°C according to method 925.10; ashes content was determined through muffle calcination at 550°C following method 923.03; lipid analyzes followed the method Ba 3–38; total proteins were performed according to the Kjeldahl method, following method 920.87; and the determination of fibers content (crude fiber, neutral detergent fiber and acid detergent fiber) was performed according to Van Soest et al. (1991).

Table 1

Experimental diets composition.
Feedstuffs	Quantities (g/kg)
Feedstuffs	Starter	Grower	Finisher
Corn 7.88%	577.689	664.061	698.656
Soybean meal 46%	362.806	280.665	241.492
Limestone	10.679	11.111	11.533
Dicalcium phosphate	26.244	24.238	21.889
Sodium chloride	8.342	7.081	5.824
DL-methionine 99%	0.711	1.286	1.266
Vitamin and mineral supplement	5.000¹	5.000²	5.000³
Soybean oil	8.529	6.558	14.340
Total (g)	1000.000	1000.000	1000.000
Nutritional levels⁴
Metabolizable energy, kcal.kg^− 1	2,900.00	3,000.00	3,100.00
Dry matter, %	88.134	88.005	88.026
Crude protein, %	21.500	18.000	16.500
Total methionine + cystine, %	0.744	0.705	0.665
Total methionine, %	0.404	0.402	0.382
Total lysine, %	1.153	0.946	0.846
Total threonine, %	0.836	0.718	0.660
Total tryptophan, %	0.270	0.222	0.198
Crude fat, %	3.343	3.334	4.170
NDF, %	11.737	11.555	11.393
ADF, %	4.802	4.457	4.270
Total minerals, %	7.696	7.084	6.601
Calcium, %	1.194	1.137	1.050
Available phosphorus, %	0.600	0.550	0.500
Sodium, %	0.350	0.300	0.250
¹ Vitamin/mineral supplement – starter – content in 1 kg of diet = Folic Acid 4 mg, Pantothenic Acid 62.500 mg, Antioxidant 0.0025 g, Biotin 0.2 mg, Niacin 168 mg, Selenium 1.5 mg, Vit. A 33.500 UI, Vit. B1 8.75 mg, Vit. B12 48 mcg, Vit. B2 24 mg, Vit. B6 12.5 mg, Vit. D3 8,000 UI, Vit. E 70 mg, Vit. K3 7.2 mg, Manganese 375 mg, Zinc 250 mg, Iron 250 mg, Copper 40 mg, Iodine 3.75 mg.
²Vitamin/mineral supplement – grower – content in 1 kg of diet = Folic Acid 3.25 mg, Pantothenic Acid 52 mg, Antioxidant 0.0025 g, Niacin 140 mg, Selenium 1.5 mg, Vit. A 28,000 UI, Vit. B1 0.00275 mg, Vit. B12 40 mcg, Vit. B2 20 mg; Vit. B6 10.4 mg, Vit. D3 6,000 UI, Vit. E 50 mg, Vit. K3 6 mg, Manganese 375 mg, Zinc 250 mg, Iron 250 mg, Copper 40 mg, Iodine 3.75 mg.
³ Vitamin/mineral supplement – finisher – content in 1 kg of diet = Pantothenic Acid 35.35 mg, Antioxidant 0.0025 g, Niacin 102 mg, Selenium 1 mg, Vit. A 9,800 UI, Vit. B12 23.5 mcg, Vit. B2 12 mg, Vit. D3 2,750 UI, Vit. E 50 mg, Vit. K3 2.75 mg, Manganese 375 mg, Zinc 250 mg, Iron 250 mg, Copper 40 mg, Iodine 3.75 mg.
⁴ Analyzed and calculated levels in Dry Matter.

The experimental design was completely randomized in a factorial scheme (2x2), where the treatments were constituted by two particle sizes of corn in the diets (6 or 8 mm) and two stocking densities (2 or 3 birds/m²), with five replicated of 10 birds each. The corn was crushed using a hammer mill (Nogueira Co.© (São João da Boa Vista, Brazil); 28 hammers) driven by a 20CV engine and 3,550 rpm, being capable of processing 1 ton of corn/hour. The treatments consisted of diets formulated with corn from a single batch, which was fractionated in two parts and each fraction was submitted to different milling diameters (mm): 6.0 (Geometric Mean Diameter (GMD) = 781 µm) and 8.0 (GMD = 1085 µm). The GMD was calculated were determined by a standard set of sieves (Committee on Classification of Particle Size in Feeedstuffs, 1969), adapted to express the result in µm, and calculated as follows:

where:

d_gw is geometric mean diameter of the particle sizes

S_gw is geometric standard deviation of the particle sizes

d_i is geometric diameter of particles on the i^th sieve (= d_i X d_i+1]^½

W_i is the weight fraction on the i^th sieve

To avoid additional effects of particle size of diets in general, the other ingredients were standardized in a maximum particle size of 4 mm (MGD = 620 µm).

2.2. Performance and carcass traits

The performance of Muscovy ducks was evaluated considering each stage proposed. The performance variables evaluated were the feed intake (kg.bird^− 1), weight gain (kg.bird^− 1) and feed efficiency (kg.kg^− 1). At 90 days of age, after 12 hours of fasting, ten birds of each treatment were randomly selected for carcass traits analysis. Next, these were weighted, electrically stunned (40 V; 50 Hz), and slaughtered by the cut of the jugular vein. The carcasses were immersed in hot water (60 ºC for 62s), plucked, and eviscerated according to the recommendations described by Mendes and Patricio (2004) in order to determine the yields of carcass, feathers, foot and abdominal fat. The commercial cuts (neck, breast, wing, back, thigh, and drumstick) were separated according to the recommendations described by Gomide et al. (2012) and weighted using an analytical balance (0.01).

2.3. GIT development analysis

At 1, 35, 70 and 90 days-old, after 12 hours of fasting, four birds of each treatment were randomly selected, identified, and weighed. Birds were slaughtered using the cervical dislocation method. The carcasses were plucked and eviscerated according to recommendations described by Mendes and Patricio (2004), where organs and segments were separated and opened to remove digesta content. The birds retired to these analyses were replaced by birds with same age kept on similar conditions in backup pens located in the same aviary in order to kept the stocking densities proposed in the treatments.

At each pre-determined age, it was evaluated the heart weight (g) and GIT development separated into organs (liver (g), pancreas (g), pro-ventricle (g) and gizzard (g)); and segments (oropharynx + esophagus (cm), duodenal loop (cm), jejunum + ileum (cm), cecum (cm) and colon + rectum (cm)) using a precision weighing scale, an electronic pachymeter and a measuring tape. After the birds were removed, they were replaced by analogs managed using similar conditions to maintain the same experimental conditions until the end of the study.

The formula used to evaluate the proportion of each segment of the GIT (RGIT) in relation to the total length of the GIT at the end of each stage was as follows:

$${RGIT}_{\%}=\left(\frac{value \left(in cm\right) of the region evaluated}{value of the total length of gastrointestinal tract}*100\right)$$

The formula used to evaluate the growth rate of the organ or segments of the GIT (GRGIT) of each stage in relation to the previous stage was as follows:

$${GRGIT}_{\%}=100-\left(\frac{value \left(g or cm\right) at the previous stage}{value \left(g or cm\right) at the final of the evaluated stage}*100\right)$$

2.4. Statistical Analyses

All data was analyzed by one-way ANOVA using the R software (2021). All commands were performed according to Logan (2010). Tukey’s honestly significant difference test was used to test the significant differences between the treatments (independent variables) for each dependent variable evaluated. The results are presented as means and the significant level for differences was set as 0.05.

3.1. Performance

At 35 days, Muscovy ducks managed in the density of 3 birds/m² presented higher (P < 0.05) feed intake and weight gain, and better (P < 0.05) feed efficiency (Table 2). At the same age, Muscovy ducks fed diets with lower particle size of corn (6 mm) presented higher (P < 0.05) feed intake (Table 2) and better (P < 0.05) feed efficiency. There was no interaction (P > 0.05) between factors in all variables evaluated.

Table 2

Phasic performance of muscovy ducks fed diets with two particle size of corn and managed into two stocking densities.
Factors¹		Variables¹
Factors¹	FI			WG			FE
Age (days)	35	70	90	35	70	90	35	70	90
SD
2 birds/m²	2.03^b	4.24^a	2.20	0.61^b	1.25^b	0.59^b	3.33^a	3.39^a	3.73^a
3 birds/m²	2.47^a	5.95^b	2.81	0.84^a	1.90^a	0.91^a	2.94^b	3.13^b	3.09^b
PSC
6 mm	2.33^a	4.86^a	2.53^a	0.76	1.55	0.73	3.07^b	3.14^b	3.47^a
8 mm	2.20^b	5.29^b	2.50^b	0.70	1.59	0.76	3.14^a	3.33^a	3.29^b
Effect
SD³	0.04^*	0.03^*	0.12^ns	0.05^*	0.02^*	0.01^*	0.02^*	0.03^*	0.04^*
PSC⁴	0.05^*	0.03^*	0.05^*	0.13^ns	0.11^ns	0.10^ns	0.02^*	0.03^*	0.03^*
SDxPSC⁵	0.44^ns	0.36^ns	0.41^ns	0.42^ns	0.46^ns	0.45^ns	0.39^ns	0.34^ns	0.37^ns
CV⁶,%	4.73	4.82	4.65	7.05	7.11	7.02	9.41	9.39	9.32
¹ SD – Stocking densities. PSC – Particle sizes of corn.
² FI = Feed intake (kg.bird^− 1). WG = weight gain (kg.bird^− 1). FE = feed efficiency (kg.bird^− 1).
³ Averages followed by lowercase letters in the column demonstrate a significant effect of SD on the variables analyzed by Tukey's test at 0.05. ns – non-significant.
⁴ Averages followed by lowercase letters in the column demonstrate a significant effect of PSC on the variables analyzed by Tukey's test at 0.05. ns – non-significant.
⁵ p-value above 0.05 demonstrates a direct influence of one factor on the result of the other and vice versa. ns – not significant.
⁶ CV = Coefficient of variation.

At 70 days, Muscovy ducks managed in the density of 3 birds/m² presented higher (P < 0.05) weight gain, lower (P < 0.05) feed intake and better (P < 0.05) feed efficiency (Table 2). At the same age, Muscovy ducks fed diets with lower particle size of corn (6 mm) presented higher (P < 0.05) feed intake and better (P < 0.05) feed efficiency (Table 2). There was no interaction (P > 0.05) between factors in all variables evaluated.

At 90 days, Muscovy ducks managed in the density of 3 birds/m² presented higher (P < 0.05) weight gain, and better (P < 0.05) feed efficiency (Table 2). At the same age, Muscovy ducks fed diets with lower particle size of corn (6 mm) presented higher (P < 0.05) feed intake (Table 2) and worse (P < 0.05) feed efficiency. There was no interaction (P > 0.05) between factors in all variables evaluated.

In the general performance, Muscovy ducks managed in the density of 3 birds/m² presented higher (P < 0.05) feed intake and weight gain, and better (P < 0.05) feed efficiency (Table 3). In the same way, Muscovy ducks fed diets with lower particle size of corn (6 mm) presented lower (P < 0.05) feed intake and better (P < 0.05) feed intake (Table 3). There was no interaction (P > 0.05) between factors in all variables evaluated.

Table 3

General performance of muscovy ducks fed diets with two particle size of corn and managed into two stocking densities.
Factors¹	Variables²
Factors¹	FI	WG	FE
SD
2 birds/m²	8.47^b	2.45^b	3.48^a
3 birds/m²	11.23^a	3.65^a	3.05^b
PSC
6 mm	9.71^b	3.03	3.22^b
8 mm	9.99^a	3.06	3.25^a
Effect	p-value
SD³	0.01^*	0.01^*	0.01^*
PSC⁴	0.05^*	0.79^ns	0.05^*
SDxPSC⁵	0.90^ns	0.88^ns	0.67^ns
CV (%)	4.74	7.01	9.37
¹ SD – Stocking densities. PSC – Particle sizes of corn.
² FI = Feed intake (kg.bird^− 1). WG = weight gain (kg.bird^− 1). FE = feed efficiency (kg.bird^− 1).
³ Averages followed by lowercase letters in the column demonstrate a significant effect of SD on the variables analyzed by Tukey's test at 0.05.
⁴ Averages followed by lowercase letters in the column demonstrate a significant effect of PSC on the variables analyzed by Tukey's test at 0.05. ns – non-significant.
⁵ p-value above 0.05 demonstrates a direct influence of one factor on the result of the other and vice versa. ns – not significant.
⁶ CV = Coefficient of variation.

3.2. Carcass traits

Muscovy ducks managed in the density of 3 birds/m² and fed diets with lower particle size of corn (6 mm) presented higher (P < 0.05) slaughter weight, carcass yield, abdominal fat and breast; and lower (P < 0.05) back (Table 4). There was no interaction (P > 0.05) between factors in all variables evaluated.

Table 4

Carcass traits of muscovy ducks fed diets with two particle size of corn and managed into two stocking densities.
Factors¹	Variables²
Factors¹	SW	CY	FT	FO	AF	NE	BE	WI	TI	DR	BA
SD
2 birds/m²	2.55^b	78.78^b	4.76	3.24	0.78^b	11.28	24.12^b	15.06	11.74	9.12	28.68^a
3 birds/m²	3.75^a	80.52^a	4.65	3.31	1.16^a	11.00	26.83^a	15.97	11.54	9.56	25.10^b
PSC
6 mm	3.16^a	80.28^a	4.91	3.25	1.09^a	10.58	28.99^a	14.90	11.30	9.60	24.63^b
8 mm	3.13^b	79.03^b	4.50	3.30	0.85^b	10.71	25.96^b	14.98	10.97	9.08	28.30^a
Effect	p-value
SD³	0.01^*	0.05^*	0.84^ns	0.61^ns	0.05^*	0.08^ns	0.05^*	0.15^ns	0.16^ns	0.17^ns	0.01^*
PSC⁴	0.05^*	0.05^*	0.47^ns	0.74^ns	0.05^*	0.12^ns	0.05^*	0.12^ns	0.12^ns	0.11^ns	0.03^*
SDxPSC⁵	0.88^ns	0.79^ns	0.82^ns	0.65^ns	0.79^ns	0.49^ns	0.53^ns	0.54^ns	0.28^ns	0.29^ns	0.28^ns
CV (%)	6.77	2.88	2.35	8.28	4.38	8.92	9.85	4.55	6.31	9.49	8.20
¹ SD – Stocking densities. PSC – Particle sizes of corn.
² SW = Slaughter weight (kg.bird^− 1). CY = Carcass yield (%). FT = Feathers yield (%). FO = Foot yield (%). AF = Abdominal fat yield (%). NE = Neck (%). BE = Breast (%).
WI = Wing (%). TI = Thigh (%). DR = Drumstick (%). BA = Back (%).
³ Averages followed by lowercase letters in the column demonstrate a significant effect of SD on the variables analyzed by Tukey's test at 0.05. ns – non-significant.
⁴ Averages followed by lowercase letters in the column demonstrate a significant effect of PSC on the variables analyzed by Tukey's test at 0.05. ns – non-significant.
⁵ p-value above 0.05 demonstrates a direct influence of one factor on the result of the other and vice versa. ns – not significant.
⁶ CV = Coefficient of variation.

3.3. GIT development

Biometrics of the GIT of 1-day-old Muscovy ducks were made to be used as a basis for estimating the phasic growth. The average results are presented in Table 5. In general, we observed that most of the GIT in 1-day-old ducks is in the small intestine area, mainly in the jejunum + ileum, the main area of nutrient absorption.

Table 5

GIT of muscovy ducks at 1 day-old.
Variable	Mean results¹
Heart, g	0.32
Liver, g	1.29
Pancreas, g	0.14
Pro-ventricle, g	0.42
Gizzard, g	2.03
Total length of GIT, cm	49.89
Oropharynx + oesophagus, %	7.780
Duodenal loop, %	14.35
Jejunum + ileum, %	58.730
Cecum, %	12.29
Colon, %	6.82
¹All data represent the mean of 16 replicates.

At 35 days-old, Muscovy ducks managed in the density of 3 birds/m² presented a higher (P < 0.05) weight of liver, pancreas, pro-ventricle and gizzard; and a higher (P < 0.05) total length of GIT, oropharynx + oesophagus, duodenal loop and jejunum + ileum (Table 6). At the same age, Muscovy ducks fed diets with a lower particle size of corn (6 mm) presented a higher (P < 0.05) weight of liver and gizzard, and a higher (P < 0.05) total length of GIT (Table 6). There was no interaction (P > 0.05) between factors in all variables evaluated.

Table 6

Heart and GIT of muscovy ducks at 35 day-old fed diets with two particle size of corn and managed into two stocking densities.
Factors¹	Variables²
Factors¹	HRT	LVR	PAN	PVT	GZD	GIL	ORE	DLP	JEI	CEC	COL
SD
2 birds/m²	5.01	24.43^b	2.96^b	5.90^b	37.90^b	195.87^b	8.42^b	11.03^b	60.24^b	12.13	5.49
3 birds/m²	5.48	30.04^a	3.52^a	6.92^a	46.43^a	204.99^a	9.00^a	12.38^a	62.93^a	12.51	5.87
PSC
6 mm	5.27	27.98^a	3.36	6.54	42.66^a	202.11^a	8.72	11.50	61.97	12.18	5.63
8 mm	5.22	26.49^b	3.12	6.28	41.68^b	198.64^b	8.68	11.89	61.29	12.46	5.67
Effect	p-value
SD³	0.35^ns	0.01^*	0.05^*	0.01^*	0.01^*	0.01^*	0.02^*	0.05^*	0.01^*	0.84^ns	0.76^ns
PSC⁴	0.33 ^ns	0.05^*	0.25^ns	0.12^ns	0.05^*	0.01^*	0.15^ns	0.86^ns	0.15^ns	0.94^ns	0.99^ns
SDxPSC⁵	0.25^ns	0.32^ns	0.19^ns	0.12^ns	0.21^ns	0.11^ns	0.21^ns	0.18^ns	0.17^ns	0.22^ns	0.18^ns
CV⁶,%	18.90	21.41	17.41	12.66	14.49	10.45	14.99	18.06	10.28	15.68	14.53
¹ SD – Stocking densities. PSC – Particle sizes of corn.
² HRT = heart (g). LVR = liver (g). PAN = pancreas (g). PVT = pro-ventricle (g). GZD = gizzard (g). GIL = total length of GIT (cm). ORE = oropharynx + oesophagus (%). DLP = duodenal loop length (%). JEI = jejunum + ileum length (%). CEC = cecum length (%). COL = colon length (%).
³ Averages followed by lowercase letters in the column demonstrate a significant effect of SD on the variables analyzed by Tukey's test at 0.05. ns – non-significant.
⁴ Averages followed by lowercase letters in the column demonstrate a significant effect of PSC on the variables analyzed by Tukey's test at 0.05. ns – non-significant.
⁵ p-value above 0.05 demonstrates a direct influence of one factor on the result of the other and vice versa. ns – not significant.
⁶ CV = Coefficient of variation.

At 70 days-old, Muscovy ducks managed in the density of 3 birds/m² presented a higher (P < 0.05) weight of heart, liver, pancreas and gizzard; and a higher (P < 0.05) total length of GIT (Table 7). At the same age, Muscovy ducks fed diets with a lower particle size of corn (6 mm) presented a higher (P < 0.05) weight of heart, liver, pancreas and gizzard; and a higher (P < 0.05) total length of GIT (Table 7). There was no interaction (P > 0.05) between factors in all variables evaluated.

Table 7

Heart and GIT of muscovy ducks at 70 day-old fed diet-s with two particle size of corn and managed into two stocking densities.
Factors¹	Variables²
Factors¹	HRT	LVR	PAN	PVT	GZD	GIL	ORE	DLP	JEI	CEC	COL
SD
2 birds/m²	15.44^b	50.50^b	3.53^b	8.53	54.51^b	213.10^b	9.79	11.53	60.94	12.02	5.69
3 birds/m²	16.61^a	58.46ª	4.05^a	8.61	58.56^a	220.99^a	9.50	11.93	60.24	12.33	6.00
PSC
6 mm	16.80^a	59.43^a	4.01^a	8.63	58.06^a	222.38^a	9.56	11.58	60.54	12.71	6.04
8 mm	15.25^b	49.53^b	3.57^b	8.50	55.00^b	213.11^b	9.68	11.85	60.24	12.20	5.62
Effect	p-value
SD³	0.03^*	0.02^*	0.02^*	0.15	0.05^*	0.03^*	0.12^ns	0.14^ns	0.11^ns	0.15^ns	0.13^ns
PSC⁴	0.02^*	0.01^*	0.03^*	0.11^ns	0.04^*	0.04^*	0.12^ns	0.08^ns	0.14^ns	0.13^ns	0.18^ns
SDxPSC⁵	0.32^ns	0.22^ns	0.14^ns	0.16^ns	0.25^ns	0.12^ns	0.28^ns	0.12^ns	0.17^ns	0.11^ns	0.10^ns
CV⁶,%	14.71	10.58	13.17	13.08	14.47	10.15	11.94	16.09	9.71	11.35	10.67
¹ SD – Stocking densities. PSC – Particle sizes of corn.
² HRT = heart (g). LVR = liver (g). PAN = pancreas (g). PVT = pro-ventricle (g). GZD = gizzard (g). GIL = total length of GIT (cm). ORE = oropharynx + oesophagus (%). DLP = duodenal loop length (%). JEI = jejunum + ileum length (%). CEC = cecum length (%). COL = colon length (%).
³ Averages followed by lowercase letters in the column demonstrate a significant effect of SD on the variables analyzed by Tukey's test at 0.05. ns – non-significant.
⁴ Averages followed by lowercase letters in the column demonstrate a significant effect of PSC on the variables analyzed by Tukey's test at 0.05. ns – non-significant.
⁵ p-value above 0.05 demonstrates a direct influence of one factor on the result of the other and vice versa. ns – not significant.
⁶ CV = Coefficient of variation.

At 90 days-old, Muscovy ducks managed in the density of 3 birds/m² presented a higher (P < 0.05) weight of heart, liver, pancreas, pro-ventricle and gizzard; and a higher (P < 0.05) total length of GIT, jejunum + ileum and cecum (Table 8). At the same age, Muscovy ducks fed diets with a lower particle size of corn (6 mm) presented a higher (P < 0.05) weight of heart, liver, pancreas, pro-ventricle and gizzard; and a higher (P < 0.05) total length of GIT, jejunum + ileum and cecum (Table 8). There was no interaction (P > 0.05) between factors in all variables evaluated.

Table 8

Heart and GIT of muscovy ducks at 90 day-old fed diets with two particle size of corn and managed into two stocking densities.
Factors¹	Variables²
Factors¹	HRT	LVR	PAN	PVT	GZD	GIL	ORE	DLP	JEI	CEC	COL
SD
2 birds/m²	16.98^b	59.22^b	3.76^b	8.77^b	58.70^b	224.48^b	10.47	12.30	57.18^b	12.86^b	5.51
3 birds/m²	20.13^a	60.44^a	4.32^a	9.90^a	63.87^a	236.99^a	10.55	12.18	58.58^a	14.14^a	5.96
PSC
6 mm	20.13^a	60.44^a	4.12^a	9.59^a	63.87^a	237.11^a	10.75	12.18	58.37^a	14.13^a	6.03
8 mm	16.98^b	49.62^b	3.96^b	8.68^b	58.70^b	221.86^b	10.59	12.00	56.99^b	13.01^b	5.96
Effect	p-value
SD³	0.05^*	0.05^*	0.04^*	0.02^*	0.02^*	0.02^*	0.15^ns	0.12^ns	0.03^*	0.01^*	0.15^ns
PSC⁴	0.01^*	0.04^*	0.02^*	0.05^*	0.05^*	0.01^*	0.11^ns	0.11^ns	0.05^*	0.05^*	0.12^ns
SDxPSC⁵	0.18^ns	0.11^ns	0.12^ns	0.15^ns	0.20^ns	0.15^ns	0.16^ns	0.12^ns	0.15^ns	0.19^ns	0.11^ns
CV⁶,%	14.55	19.57	13.17	11.09	16.13	10.12	12.79	14.96	11.37	10.13	12.34
¹ SD – Stocking densities. PSC – Particle sizes of corn.
² HRT = heart (g). LVR = liver (g). PAN = pancreas (g). PVT = pro-ventricle (g). GZD = gizzard (g). GIL = total length of GIT (cm). ORE = oropharynx + oesophagus (%). DLP = duodenal loop length (%). JEI = jejunum + ileum length (%). CEC = cecum length (%). COL = colon length (%).
³ Averages followed by lowercase letters in the column demonstrate a significant effect of SD on the variables analyzed by Tukey's test at 0.05. ns – non-significant.
⁴ Averages followed by lowercase letters in the column demonstrate a significant effect of PSC on the variables analyzed by Tukey's test at 0.05. ns – non-significant.
⁵ p-value above 0.05 demonstrates a direct influence of one factor on the result of the other and vice versa. ns – not significant.
⁶ CV = Coefficient of variation.

Evaluating the growth rate of the GIT in relation to the previous stage, we observed in all evaluated organs that the initial stage is where the greatest development occurs. In addition, it was also possible to observe that the growth rate of the organs of the GIT decreases with age. Throughout the length of the segments of the GIT, this relationship occurs in the opposite way.

At 35 days, both stocking densities and the particle size of corn did not interfere (P < 0.05) in the growth rate of the organs of the GIT (Table 9). However, Muscovy ducks managed in the density of 3 birds/m² presented higher (P < 0.05) growth rates in the duodenal loop, jejunum + ileum and cecum (Table 10). At the same age, Muscovy ducks fed diets with a lower particle size of corn (6 mm) presented higher (P < 0.05) growth rates in the oropharynx + oesophagus, duodenal loop, cecum and colon (Table 10). There was no interaction (P > 0.05) between factors in all variables evaluated

Table 9

Growth rate in relation to the previous stage of heart and main organs of the GIT of muscovy ducks fed diets with two particle size of corn and managed into two stocking densities.
Factors¹		Variables²
Factors¹	HRT			LVR			PAN			PVT			GIZ
Age (days)	35	70	90	35	70	90	35	70	90	35	70	90	35	70	90
SD
2 birds/m²	93.33	56.45^b	17.71^b	94.84	28.80^b	11.92^b	94.95	17.20^b	16.35^b	91.54	23.11^b	19.18^b	94.15	26.19	20.23^b
3 birds/m²	93.28	69.33^a	30.63^a	94.42	47.61^a	31.52^a	93.84	28.35^a	26.06^a	93.24	25.41a	24.19^a	94.64	25.49	24.21^a
PSC
6 mm	93.47	65.62^a	25.64^a	94.76	41.03^a	27.68^a	95.01	25.14^a	31.63^a	91.78	25.83^a	22.87	94.74	26.66	23.70
8 mm	93.14	60.16^b	22.72^b	94.49	35.38^b	15.77^b	93.78	20.40^b	10.78^b	93.00	22.69^b	20.50	94.04	25.01	20.75
Effect	p-value
SD³	0.97^ns	0.05^*	0.05^*	0.60^ns	0.03^*	0.02^*	0.66^ns	0.05^*	0.03^*	0.11^ns	0.05^*	0.05^*	0.15^ns	0.93^ns	0.05^*
PSC⁴	0.78^ns	0.04^*	0.05^*	0.74^ns	0.05^*	0.04^*	0.62^ns	0.05^ns	0.01^*	0.27^ns	0.05^*	0.80^ns	0.36^ns	0.84^ns	0.68^ns
SDxPSC⁵	0.22^ns	0.12^ns	0.15^ns	0.23^ns	0.14^ns	0.13^ns	0.21^ns	0.10^ns	0.11^ns	0.22^ns	0.12^ns	0.10^ns	0.25^ns	0.13^ns	0.11^ns
CV⁶,%	2.49	2.09	5.68	1.66	4.75	1.52	5.10	6.91	8.74	2.33	6.51	8.49	1.58	6.08	6.19
¹ SD – Stocking densities. PSC – Particle sizes of corn.
² HRT = heart (%). LVR = liver (%). PAN = pancreas (%). PVT = pro-ventricle (%). GZD = gizzard (%).
³ Averages followed by lowercase letters in the column demonstrate a significant effect of SD on the variables analyzed by Tukey's test at 0.05. ns – non-significant.
⁴ Averages followed by lowercase letters in the column demonstrate a significant effect of PSC on the variables analyzed by Tukey's test at 0.05. ns – non-significant.
⁵ p-value above 0.05 demonstrates a direct influence of one factor on the result of the other and vice versa. ns – not significant.
⁶ CV = Coefficient of variation.

Table 10

Growth rate in relation to the previous stage of the segments of the GIT of muscovy ducks fed diets with two particle size of corn and managed into two stocking densities.
Factors¹		Variables²
Factors¹	ORE			DLP			JEI			CEC			COL
Age (days)	35	70	90	35	70	90	35	70	90	35	70	90	35	70	90
SD
2 birds/m²	16.61	11.82^b	32.42^b	14.78^b	12.32^b	57.72^b	8.56^b	6.49^b	57.76^a	16.98^b	13.13	56.74^a	11.14	8.48	65.70^a
3 birds/m²	17.93	15.71^a	37.39^a	20.27^a	13.13^a	65.71^a	10.72^a	10.42^a	51.16^b	21.67^a	15.56	43.73^b	13.09	10.57	54.51^b
PSC
6 mm	19.20^a	18.60^a	38.10^a	19.19^a	14.43^a	65.44^a	10.65^a	8.08	55.27	23.50^a	14.01	52.90^a	13.45^a	10.34	60.03
8 mm	15.33^b	8.93^b	31.71^b	15.86^b	11.02^b	57.99^b	8.63^b	8.82	53.65	15.15^b	14.70	47.57^b	10.78^b	8.72	60.17
Effect	p-value
SD³	0.84^ns	0.03^*	0.05^*	0.03^*	0.05^*	0.03^*	0.05^*	0.03^*	0.03^*	0.03^*	0.53^ns	0.01^*	0.16^ns	0.61^ns	0.01^*
PSC⁴	0.05^*	0.01^*	0.03^*	0.05^*	0.05^*	0.05^*	0.05^*	0.85^ns	0.63^ns	0.05^*	0.86^ns	0.05^*	0.05^*	0.69^ns	0.97^ns
SDxPSC⁵	0.20^ns	0.18^ns	0.21^ns	0.23^ns	0.22^ns	0.25^ns	0.23^ns	0.22^ns	0.21^ns	0.23^ns	0.25^ns	0.20^ns	0.19^ns	0.15^ns	0.13^ns
CV⁶,%	7.61	5.83	4.06	6.57	5.52	12.81	7.43	9.04	11.85	5.07	5.23	2.17	8.33	8.26	15.84
¹ SD – Stocking densities. PSC – Particle sizes of corn.
² ORE = oropharynx + oesophagus (%). DLP = duodenal loop length (%). JEI = jejunum + ileum length (%). CEC = cecum length (%). COL = colon length (%).
³ Averages followed by lowercase letters in the column demonstrate a significant effect of SD on the variables analyzed by Tukey's test at 0.05. ns – non-significant.
⁴ Averages followed by lowercase letters in the column demonstrate a significant effect of PSC on the variables analyzed by Tukey's test at 0.05. ns – non-significant.
⁵ p-value above 0.05 demonstrates a direct influence of one factor on the result of the other and vice versa. ns – not significant.
⁶ CV = Coefficient of variation.

At 70 days, both stocking densities and particle size of corn did not affect (P < 0.05) the growth rate of the gizzard (Table 9). However, Muscovy ducks managed in the density of 3 birds/m² and fed diets with a lower particle size of corn (6 mm) presented higher (P < 0.05) growth rates in the heart, liver, pancreas and pro-ventricle (Table 9). In the segments of the GIT, Muscovy ducks managed in the density of 3 birds/m² presented higher (P < 0.05) growth rates in the oropharynx + oesophagus, duodenal loop and jejunum + ileum (Table 10). At the same age, Muscovy ducks fed diets with a lower particle size of corn (6 mm) presented higher (P < 0.05) growth rates in the oropharynx + oesophagus and duodenal loop (Table 10). There was no interaction (P > 0.05) between factors in all variables evaluated

At 90 days, Muscovy ducks managed in the density of 3 birds/m² presented higher (P < 0.05) growth rates in the heart, liver, pancreas, pro-ventricle and gizzard (Table 9). In the segments of the GIT, Muscovy ducks managed in the density of 3 birds/m² presented higher (P < 0.05) growth rates in all the segments evaluated (Table 10). At the same age, Muscovy ducks fed diets with a lower particle size of corn (6 mm) presented higher (P < 0.05) growth rates in the heart, liver and pancreas (Table 9). In the segments of the GIT, these Muscovy ducks presented higher (P < 0.05) growth rates in the oropharynx + oesophagus, duodenal loop and cecum (Table 10). There was no interaction (P > 0.05) between factors in all variables evaluated

Initially, we observed that the Muscovy ducks managed in the density of 3 birds/m² presented higher performance, carcass traits and GIT development than those managed in the density of 2 birds/m² regardless of age evaluated. The literature reported that feed efficiency is directly related to stocking densities, where changes in physical space affect the feed behavior of birds and, consequently, the development of their GIT and carcass traits (Garcia et al., 2002; Cruz et al., 2013; Rufino et al., 2017a,b). Front this, if the stocking density does not cause any apparent discomfort to the birds, respecting the animal welfare rules and allowing the birds to express their full genetic potential in feed efficiency and body development, consequently, this is the better density to be used in that environmental condition (Lewis et al., 1997; Garcia et al., 2002; Cruz et al., 2013).

This is an interesting point because Rodenburg et al. (2005) reported that, such as observed in broilers, higher stocking densities also may provide better performance and carcass traits for ducks and Muscovy ducks in housing, even their recommendations of birds/m² being below those used for broilers in industrial production systems. According to Rufino et al. (2017b), ducks and Muscovy ducks tend to present growth curves and behavior in housing more similar to slow-growing broilers than conventional broilers, implying a stocking density with few birds/m², generally being recommended from 4 up to 7 birds/m² in low-temperature environments. However, due to the lack of accurate information related to the management of Muscovy ducks in housing, in addition to their peculiar characteristics, Lewis et al. (1997), Cruz et al. (2013) and Bawish et al. (2018) recommended that the stocking densities for Muscovy ducks in production stage (1 to 90 days) should be below than those used for slow-growing broilers, do not being higher than 4 birds/m² to obtain better performance and carcass traits.

In this study, we observed all these points and, considering the results obtained, it was clear that Muscovy ducks may be managed in housing using densities of up to 3 birds/m² presenting great GTI development, performance and carcass traits, indicating that this is an ideal recommendation for the management of these birds in housing. It is a fact that this recommendation is slightly below those indicated by other studies (Lewis et al., 1997; Cruz et al., 2013; Bawish et al., 2018). But, considering the environment where the Muscovy ducks were managed, a tropical climate with high temperatures and relative humidity, this recommendation provided a pleasant enough environment for full body development and productive response, obtaining results superior to those reported by these studies.

Stocking density is a critical point for poultry production and welfare. To a certain extent, it is believed that higher economic returns can be obtained as the number of birds/m² increases (Scanes and Christensen, 2020). However, an excessive number of birds/m² can also cause a significant reduction in health and welfare, consequently causing negative effects on performance (Xie et al., 2014; Bawish et al., 2018). The stocking densities of birds in industrial systems must respect, among other things, the physiological characteristics of the animal and the environment where it is housed (Estevez, 2007; Scanes and Christensen, 2020). Obeying this, it is possible to find ideal recommendations for stocking densities, such as observed in this study.

In the other part of the study, it was clear the influence of the particle size of corn on feed behavior and body development of Muscovy ducks in housing, where birds fed diets using a particle size of corn of 6 mm (MGD = 781 µm) presenting higher performance, carcass traits and GIT development regardless of age evaluated. The influence of the corn particle size on the development of main organs related to food digestion (pro-ventricle, gizzard, liver and pancreas) and nutrient absorption regions (duodenal loop, jejunum, ileum, cecum and colon) in each stage was very evident. Curiously, another point observed is that while the organs related to digestion presented their most accentuated growth in the initial stages of the GIT development, the nutrient absorption regions showed the opposite behavior.

It was also interesting to note that the particle size of corn that provided higher results for Muscovy ducks in this study was higher than that normally recommended for broilers (4 mm) (O’Connor, 1987; Hamilton and Poundfoot, 1995; Hetland et al., 2004; Amerah et al., 2007). In addition, the performance and carcass traits results obtained in this study were better than those reported by other studies with Muscovy ducks using a particle size of corn similar to that used for broilers (Cruz et al., 2013; Rufino et al., 2015; Rufino et al., 2017a). Apparently, this particle size of corn may provide higher stimulus in the GTI of Muscovy ducks at all stages of production and result in better performance and carcass traits.

It is possible to affirm that the corn used in diets for Muscovy ducks should have a particle size larger than that recommended for broilers, and this fact may be related to the own physiology of this bird species. According to Moran Jr (1987), birds tend to prefer the particle size that suits their beak, regulating intake according to the particle size of the food provided. Front this, it is easy to think that larger birds tend to prefer larger food particles, especially considering that Muscovy ducks naturally reach a body size larger than broilers being managed as breeders or at the end of the production cycle (Shalev, 1995; Scanes and Christensen, 2020; Jalaludeen et al., 2022).

On the other hand, the literature also reported that the particle size of corn cannot be very large, because it can cause serious damage to the GIT of the birds and impair its performance and carcass traits (Hamilton and Poundfoot, 1995; Amerah et al., 2007), such as observed in this study. According to O’Connor (1987), the particle size of foods causes a significant effect on the bird’s development due to its substantial influence on nutrient absorption and energy metabolism. Non-uniformity or inappropriately sized particles may cause selectivity in the birds during the feeding, in addition to problems related to acceptance or rejection of these foods, and increase or decrease of the energy needed for grinding during the processing of the diets (Reece et al., 1986; Scanes and Christensen, 2020).

Physiologically, studies reported that a non-adequate particle size of the foods, too small or too big, may cause a lower GIT development due to the absence of chemical and enzymatic stimuli in the main areas of digestion and absorption of nutrients (Jacobs et al., 2010; Chewning et al., 2012). This condition causes the food to be poorly processed or used very little by the birds' organism, restricting the bird from presenting its full development potential (Sauveur, 1990; Nir et al., 1994a,b).

Our results are in agreement with these factors presented in the literature, demonstrating that a particle size of corn slightly above the recommendation for broilers provides an adequate condition for the Muscovy ducks to express its productive potential in GIT development and, consequently, in performance and carcass traits. In addition, it reinforces the fact that Muscovy ducks in housing, despite having some similarities with broilers during the management and at other basic points of production, have their specific requirements, which should be further researched and emphasized by researchers and producers.

The results from the current study indicated that Muscovy ducks in housing managed in a density of 3 birds/m² and fed diets using a particle size of corn of 6 mm (MGD = 781 µm) presented higher GTI development, resulting in better performance and carcass traits. Adequate recommendations of stocking densities and particle size of foods for Muscovy ducks appear to improve the development of their GIT at all stages of their productive life, which results in better results of performance and carcass traits.

Author contribution

Experimental plan and design were conceived, planned, and developed by Leandro de Carvalho Maquiné, João Paulo Ferreira Rufino, Frank George Guimarães Cruz, and Pedro de Queiroz Costa Neto. Primary research draft was written by Leandro de Carvalho Maquiné, and João Paulo Ferreira Rufino. Leandro de Carvalho Maquiné, João Paulo Ferreira Rufino, Kelven Wladie dos Santos Almeida Coelho, Gilberto Batista Viana Filho, and Francisco Alberto de Lima Chaves prepared materials and methods. Leandro de Carvalho Maquiné, João Paulo Ferreira Rufino, Kelven Wladie dos Santos Almeida Coelho, Gilberto Batista Viana Filho, and Francisco Alberto de Lima Chaves collected data. Leandro de Carvalho Maquiné, and Kelven Wladie dos Santos Almeida Coelho performed laboratory analysis. Leandro de Carvalho Maquiné, and João Paulo Ferreira Rufino performed statistical analysis and result interpretation. Manuscript was reviewed and edited by Leandro de Carvalho Maquiné, João Paulo Ferreira Rufino, Frank George Guimarães Cruz, and Pedro de Queiroz Costa Neto. Ultimate manuscript was read and approved by all authors

Funding

None.

Data availability

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

Ethics approval

The study protocol was approved by the Animal Ethics Committee at Faculty of Agrarian Sciences, Federal University of Amazonas, Brazil, and the experimental procedures were performed in accordance with the internationally accepted standard ethical guidelines for animal use and care.

Consent for publication

All authors give consent for publication.

Consent to participate

Not applicable.

Conflict of interest

The authors declare no competing interests.

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Effects of particle size of corn and stocking densities on the performance, carcass traits and gastrointestinal tract development of Muscovy ducks in housing

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Journal Publication

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Abstract

1. Introduction

2. Material and methods

2.1. Facilities, animals, diets and experimental design

2.2. Performance and carcass traits

2.3. GIT development analysis

2.4. Statistical Analyses

3. Results

3.1. Performance

3.2. Carcass traits

3.3. GIT development

4. Discussion

5. Conclusion

Declarations

References

Status:

Journal Publication

Version 1