In order to reduce costs and improve the profitability of poultry production in tropical countries, the replacement of imported grains by locally available plant foliage as non-conventional feeds (Dale 2007) has been studied due to their high nutritional value. However, it is of great importance the knowledge of their physicochemical characteristics and their effect on poultry nutrition and physiology that will account for the productive responses (Rodríguez et al. 2006).
Among these new alternatives is the mulberry tree which was sown in Asian countries 4 500 years ago for sericulture (Kitahara 2001). It belongs to the Moraceae family, Dicotyledonous class; Urticaceous subclass (Boschidini 2006). It represents a forage alternative of good adaptation to the tropics and subtropics (Medina et al. 2009), its fibrous fractions are low regarding other foliages (Albert 2006) and by the physicochemical properties of its soluble and insoluble compounds can exert various physiological effects on the gastrointestinal tract of monogastric species, especially poultry, that due to their digestive condition are not capable of degrading high amounts of fiber (Gonzalvo et al. 2001).
The objective of this study was to assess the effects on the morphometry of the GIT and accessory glands of heterozygotic naked neck chickens fed mulberry leaf meal (mfM).
1 Materials and Methods
1.1 Location, soil
This investigation was carried out in the province of Los Ríos, Ecuador, located at 01º06’ South latitude and 79º29’West latitude, at 75 masl, with an average annual temperature of 24.7º C; 87 % relative humidity; 2613 mm rainfall, 886 h of annual heliophany and sandy-slime-clayey soil.
1.2 Sowing and plant drying
The mulberry var. Criolla, was sown using 40 cm cuttings (tilted), at a rate of 40 cm between plants and rows one meter apart, in an area of 5000 m2 divided in three lots (1667 m2/lot) by age (30, 45 and 60 d of sprout), fertilized with organic fertilizer (300 kg/ha). One year after its establishment, leaves were manually collected, dried in the shade, in cement floor for three days, and later homogenized and ground for sending them to the laboratory. Average chemical composition of mulberry leaves of 45 d of sprout was (%): 92.8 DM, 24.8 CP, 2.96 Ca, 0.38 P, 39.5 NDF, 27.9 ADF, hemicellulose 17.5, cellulose 12.4, lignin 6.10 and 8.74 MJ/kg ME.
1.3 Animals and diets
Forty eight heterozygotic naked neck chickens (T451N, Sasso 2010), 24 males and 24 females with average live weights between 750 to 800 g were used for attaining the correct representativeness of the sample by sex and by weight, of 28 days of age vaccinated against Newcastle. They were housed in metallic cages and were adapted to the experimental diets from 14 d. Animals received four diets/ treatments for the growing and final stages, with three levels (3, 6 y 9 %) of mulberry foliar meal (mfM) and a control (maize-soybean) formulated according to the requirements for this poultry category (Table 1) and they had free access to water and feed.
Table 1 Composition of the diets with different inclusion levels of mulberry leaf meal for growing *1 and finishing *2 heterocygotic naked neck chickens |
1.4 Chemical analyses
DM and protein content were determined according to AOAC (2006), neutral detergent fiber (NDF), acid detergent fiber (ADF), hemicelluloses, cellulose and lignin according to Goering and van Soest (1970).
1.5 Statistical method
A random block design with four treatments and six replications per treatment (12 chickens/treatment: 6 females and 6 males) was applied. For the analysis of results, SAS (Statistical Analysis System), version 9.3 (2013) was used. Duncan’s (1955) multiple range test was used for mean comparisons.
1.6 Experimental procedure
Animals were weighed at 91 d and at 2 hours and 30 min after feed intake. Slaughtering was by the bleeding of the jugular vein method (Sánchez 1990) for extracting the accessory organs (liver and pancreas) and the digestive tract. For their analysis, this latter was divided into proventriculus, gizzard, small intestine and cecum. The digestive organs were weighed, full and empty, and results were expressed as relative to live weight (LW) %.
2 Results and Discussion
There were significant differences (P<0.05) in the relative weight to the live weight (LW) (%) of all indicators of the full GIT. With the higher inclusion levels (6 and 9 %) of the MFM weight of GIT increased and differed (P < 0.05) from the control (Table 2). However, the weights of the proventriculus and ceca of the empty GIT, regardless of the inclusion levels of MFM, were similar but differed (P < 0.05) significantly to the control. On the other hand, the gizzard with the highest inclusion level increased its size and differed from the remaining treatments (Table 3).
Table 2 Relative weight (% live weight) of the full gastrointestinal tract |
Table 3 Absolute weight of the empty gastrointestinal tract |
GIT weight changes could be due to an adaptation process of the chickens for increasing the fermentative capacity of the coarse feed (Savón 2005). Similar responses were observed by González et al. (2007) in broilers and Rodríguez et al. (2006) in layers. As can be observed (Table 1), the fiber percentage both in the growing and finishing phases increased for the levels of 6 and 9 % mfM in comparison to the control.
Correct the values in Table 3, which seem incorrect as very high values are reported. Infact, after emptying, they should have been lower than those of Table 2.
These values are higher than those reported (4 %) Sasso (2010). Thus, the excess fiber in diet increased the weight of these GIT indicators, in agreement to the observation of Itzá et al. (2010).
González- Alvarado et al. (2006) have studied the influence of the type of fat added to the feed and the inclusion of two types of fiber at diet 3 % (oat husk and beet pulp) and observed that the GIT, proventriculus and gizzard increased their size. This is probably due to the increase of the water retention capacity and the enlargement capacity of the fiber. These results have been confirmed by Jiménez Moreno et al. (2006).
The increase of the size of the gizzard is due to greater gastric activity for realizing the mechanic digestion of the fibrous components. The gizzard is a crushing organ of the feed in the birds, but it also acts as filter because it retains or allows the passage of the particles to the duodenum depending upon their characteristics (Mateos et al. 2006). Coarse particles are retained until they attain the critical size determined by the diameter of the pylorus (González- Alvarado et al. 2006; Albetis 2010 and Pietschs 2014) that have an effect on a greater mechanical work and with this its muscle development. In addition, these effects are related with the physical form, chemical nature (source and origin), type of fiber, processing to which is submitted, adaptation and animal characteristics (age and live weight) (Martínez et al. 2010).
In this sense, diets rich in non-amylaceous polysaccharides provoke modifications in the intestinal morphology, mainly in ceca weight. This effect is due to an adaptation process of the birds for increasing the fermentative capacity through the presence of bacteria and fungi as observed in pigs, poultry and man (Apajalahti and Kettunen 2002; Donalson et al. 2005; Dunkley et al. 2007; Rodríguez et al. 2012).
Martínez et al. (2010) used three levels of mulberry foliar meal (5, 10 and 15 %) and a control (maize and soybean). With 10 % of meal, ceca distended its size, cholesterol (mmol/L) decreased and fermentability increased with higher production of short chain fatty acids (mmol/L). Other researchers (Rodríguez et al. 2006; Martínez et al. 2008) have found similar results on utilizing other fiber sources for broiler and layer feeding.
With the highest inclusion levels of MFM the relative weight of liver and pancreas increased (P < 0.05) in comparison to the control and 3 % meal (Table 4). According to Martínez et al. (2010) these organs increased their weight through their function for degrading the fibrous feed, by their contribution, with their secretions.
Table 4 The results suggested that mulberry foliar meal could be used upto 3 % in diet without affecting the morphometric indicators of the full GIT of heterocygotic naked neck chickens |
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