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Introduction
Using intensive animal systems with a short generation interval is a way to minimize animal protein deficit in developing countries (Isikwenu, 2013). In this sense, cuniculture stands out as a promising economic activity (Iyeghe-Erakpotobor & Esievo, 2010). The high cost associated with production of these animals has been a setback in the livestock industry. However, growing interest in rabbit (Oryctolagus cuniculus L.) production has stimulated the search for high-quality alternative protein sources which is expected not to compete with human food (Adedeji et al., 2013; Quintero de Vallejo, 1993).
In recent years, tropical forages have been highlighted as a less expensive and locally available source in the tropics. Moreover, potential of tree fodder in diet is determined by its excellent nutritional composition and digestive utilization ability of animals (Medugu, Mohammed, Raji, Barwa & Zhinma, 2012.). This situation has stimulated the search for local food alternatives, using the existing infrastructure to materialize the exploitation of new raw materials as food sources and generate production patterns adjusted to the current social and economic reality of any environment (Esminger, Oldfield & Heinermann, 1990).
In this sense, tropical forages can improve the quality of diets traditionally used in animals. Crude protein content of these species is generally higher compared to various pastures (CATIE, 1985). Therefore, the aim of this study was to evaluate effect of tropical forages as morera (Morus alba L.), cacara (Erythrina poeppigiana (Walp.), O.F.Cook), and gold button or mirasol (Tithonia diversifolia (Hemsl.) A. Gray) included in an alternative diet on the fattening performance of rabbits.
Material and methods
The research was carried out in the experimental farm "La María", belonging to the Faculty of Animal Sciences of Universidad Tecnica Estatal de Quevedo (UTEQ), province of Los Ríos-Ecuador. The farm is located at a latitude of 01° 06' S and 79° 29' of longitude W, at an altitude of 73 m.a.s.l., in the tropical humid forest (THF) ecological zone.
As the aim of this study was to assess the effects of dietary fat in growing rabbits based on tropical forages, 48 male New Zealand rabbits of 35 days of age were considered, with an average weight of 475.47 ± 74.23 g of dry matter.d-1.
Rabbits were allocated in collective cages (two rabbits per experimental unit) of 0.50 m x 0.50 m x 0.40 m distributed in four treatments and six replicates in a completely randomized design. To identify significant difference among treatments and statistical significance for all comparisons was made at p < .05, and the fattening trial was analyzed using the GLM procedure using the Statistical Analysis Systems (SAS™) software (SAS, 2004).
In this sense, the evaluated treatments were as follows: T1: commercial concentrate ad libitum (control); T2: commercial concentrate 50 g + Morera ad libitum; T3: commercial concentrate 50 g + Caraca ad libitum, and T4: commercial concentrate 50 g + gold button ad libitum.
Variables measured were: forage intake (FI); balanced intake (BI); intake feed in g of dry matter (IFDM); final weight (FW); growth rate (GR) of fattening rabbits; feed conversion rate (FCR); weight to channel (PC), performance to channel (PC) and profitability.
In addition, animals were weighed and feed intake was measured weekly during the experimental stage to determine forage intake (FI); balanced intake (BI); feed intake in g of dry matter (FI); final weight (FW); weight gain (WG); feed conversion rate (FCR); weight to channel (WC), performance to channel (PC) and profitability, respectively.
Subsequently, rabbits were sacrificed with an average weight of 3067 ± 258 g, but they were fasted 20 h before sacrifice; however, transportation time was not considered since they were sacrificed and trials were subjected to approval by the Animal Protocol Review Committee of UTEQ, following the procedures of meat hygiene manual. Likewise, total mortality during fattening period was calculated considering all animals.
Nonetheless, three shrub forages were verified according to the forage bank established at the minor species program of UTEQ. In fact, an equalization cut was made allowing to maintain a supply and harvest for 30 days after, i.e. from the initial cut, shoots were used until the end of the experiment. In addition, each feed cut lasted for 12 hours. Nevertheless, fattening rabbits received water ad libitum through automatic drinking troughs. Alternatively, rabbits were dewormed at the start of the experiment and after 21 days, with Panacur (0.5 cc.animal-1); furthermore, Sulfavit (2.0 g.L-1 of water) was also supplied every 14 days to inhibit coccidian development. In fact, at the end of the 56 days the research lasted, 100% of the animals were sacrificed to establish the performance to channel variable measure.
It is important to note that bromatological analysis of green foliage was performed on dried samples in a forced air oven at 65°C for 48 hours, and proximal composition were respectively determined by duplicate according to AOAC (1990), following procedures No. 934.01 and 973.49, respectively.
Conversely, algebraic expressions based on the economic theories of Krugman & Wells (2006), and Samuelson & Nordhaus (2009), were considered as follows: Total cost, total income and utility for profitability were used to establish profitability. Total cost was obtained by multiplying the activity or input by the respective price, followed by equation 1 as follows:
Equation 1
Where:
PC = Production cost
Px = Input or X activity price
X = Input or activity
Total income was obtained by multiplying yield (kg of meat) by its market price. The algebraic expression is followed by equation 2 as follows:
Equation 2
Where:
TIT= Total income ($.kg-1) Py= Market price ($.kg-1)
Y= Yield (kg.ha-1)
Profitability was obtained by subtracting total costs from total income using equation 3 as follows:
Equation 3
While profitability was obtained with equation 4:
Equation 4
Results
Chemical composition of fresh foliage
Chemical analysis of fresh foliage of tropical shrub tree species assessed is shown in Table 1.
Table 1 Chemical composition of fresh foliage of M. alba, E. poeppigiana and T. Diversifolia harvested at thirty days
DM: dry matter; OM: organic matter
Source: Results of laboratory tests carried out in Agrolab in 2016.
In addition, dry matter (DM) and organic matter (OM) showed their best proportions, in order: M. alba (26.2 %; 92 %), E. poeppigiana (22.1 %; 89%) and T. diversifolia (14 %; 87 %).
Protein values had a moderate variation, whereas E. poeppigiana and M. alba showed values above 20% protein, while fiber was twice as high for E. poeppigiana (32.1%), with a slight reduction in forage intake. Nonetheless, M. alba with 15.2 % fiber had higher acceptance in consumption followed by T. diversifolia (Table 2). However, these shrubs were acceptable and no problems were reported by supplying these foliages in fresh form.
Productive parameters
The highest dry matter (balanced and forage) consumption was similar among diets T1: control, T2: inclusion of M. alba, and T4: inclusion of T. diversifolia (83.92 ± 4.31, 83.90 ± 1.08, 81.72 ± 2.85 g DM.animal-1.day-1) over (p < .05), T3: inclusion of E. poeppigiana (75.99 ± 1.58 g DM. animal-1.day-1). However, it was possible to obtain differences (p <.05) in weight gain between the control treatment (28.81 ± 2.55 g) compared to T2, T3 and T4 (25.24 ± 1.98, 23.55 ± 1.03 and 20.18 ± 1.70 g, respectively). Relative gains were found when using unconventional diets for fattening rabbits in tropical environments (Table 2). In addition, feed conversion rate (FCR) (Table 2) had a similar trend in treatments T1: concentrate, T2: inclusion of M. alba and T3: inclusion of E. poeppigiana (2.93 ± 0.27; 3.34 ± 0.28 and 3.23 ± 0.19).
Table 2 Productive parameters in fattening rabbits with tropical forages
1Means in a row not sharing superscripts significantly differ at Ρ < .05.
BC: Balanced consumption. TFC: Tropical forages consumption. FI: Feed in take. FW: Final weight. WG: Weight gain. FCR: feed conversion rate. WC: Weight to channel. PC: Performance to channel.
Likewise, performance to channel (PC) in T1: control and T3: inclusion of E. poeppigiana (57.15 ± 0.61; 56.0 ± 1.11 %) was not affected by the inclusion of green foliage of E. poeppigiana (Table 1), which have allowed to obtain satisfactory results when fattening rabbits fed with tropical forages.
Economic analysis
Treatment T3: Balanced + E. poeppigiana presented the lowest production cost (58.79 USD); the highest income was reported in T1 followed by T3 and T2 (108.5, 89.80 and 88.95 USD, respectively), and the highest utility was found in T1 (36.32) followed by T3 (31.02) (Table 3).
Table 3 Expenses, income and utility ($USD) in fattening rabbits with tropical forages
Sale Price in January 2017 = 7.5 $USD.
Furthermore, T3 diet, which included green foliage of E. poeppigiana, showed a higher yield (52.75 %) compared to the control T1 (50.32 %), followed slightly by T2 (44.35 %), which should be related with the higher meat production of does recorded with T3 diet (Figure 1).
Discussion
Chemical analysis of fresh foliage of tropical shrub tree species assessed show that their nutritional contents are higher than what is found in pastures.
Moreover, ash results are related to OM content, and conversely, when higher MO content is found, a lower mineral content is also found (Herrera, Fortes, García, Cruz and Romero, 2008).
Results are comparable in variability to what Carmona (2007) reported when studying the effect of forage trees and shrubs species used, showing the chemical composition of M. alba with 25 % DM, 15 % and 28 % protein, 15 % fiber. In addition, E. poeppigiana showed values of 23-35 % DM, 15-25 % protein, 16-38 % fiber, and values for T. diversifolia, were DM 24-35%, protein 15-28 % and fiber 16-38 %.
However, the DM intakes reported by Nieves, López and Cadena (2001) are higher when using diets with non-traditional products (flour) + 300 g of fresh forage of Trichanthera gigantea (105.10 ± 4.88 and 106.14 ± 3.72 g.dia-1). This higher consumption may be due to low polyphenols and tannins contents in the foliage of Trichantera according to some authors. Despite this, weight gains do not exceed (19.01 ± 5.24 and 19.79 ± 2.97 g), i.e. compared to those reported in the present study. Therefore, consumption results of DM obtained by Nieves, Terán, Cruz, Mena & Gutiérrez (2011) when using diets including foliage of T. gigantea (115.30, 118.57 and 113.77 g dia-1), occurs because of high contents of digestible nutrients, but do not increase significantly daily weight gain (18.17, 18.15 and 20.93 g, respectively).
Some literature citations on the influence of alternative food sources in fattening rabbits are described by Quintero, García and Peláez (2007) and Montejo, López & Lamela (2010), where they have included up to 30 % T. diversifolia flour and 30 % lebbeck tree (Albizia lebbeck (L.) Benth.) flour obtaining weight gains of 20.3 and 16.3 g, respectively. In fact, in a previous work by Rodríguez & Bazó (1997), the authors noticed a weight gain of 21.3 g when fattening rabbits when using 50% of commercial concentrate + 50% of green leucaena (Leucaena leucocephala (Lam.) de Wit). Moreover, in another experiment with these same diets, Martín, Noda & Pentón (2007), demonstrated that it is possible to substitute up to 50 % of commercial concentrate for pelleted leaf of M. alba, without significant differences in weight gain (22 g and 25 g). Moreover, several authors have found that daily feed intake and daily weight gain when fattening rabbits seem to be affected by the inclusion of green foliage in a conventional diet (concentrate), which has allowed proposing its use for fattening rabbits.
Furthermore, feed conversion rate had a similar trend in treatments T1, T2, and T3; these results exceed those reported by Nieves et al. (2001), who obtained weight gains by dietary inclusion levels of non-traditional products as follows: (flour) + 300 g of fresh forage of T. gigantea in the diet for rabbits. Similarly, Quintero et al. (2007), with three levels of T. diversifolia flour (15, 30 and 45%, respectively) in the diet (4.8, 4.2 and 4.4), and according to Nieves, Rojas & Terán (2005), found that this type of dietary fat, influenced the process of nutrient utilization and biological efficiency (WG and FCR) due to digestibility changes of ingested nutrients.
Additionally, performance to channel in T1 and T3 was not affected by the inclusion of green foliage of E. poeppigiana green foliage, which have allowed to obtain satisfactory results when fattening rabbits fed with tropical forages. Consequently, the combination of tropical forage resources is a safe alternative for subsistence of cunicular exploitation with less dependence on commercial concentrated feed (Nieves, Rojas & Terán, 2005; Rodríguez & Bazó, 1997).
On the other hand, T3 diet, which included green foliage of E. poeppigiana, showed a higher yield compared to the control T1, followed slightly by T2; this should be related with the higher meat production of does recorded with T3 diet. In this sense, the use of tropical forages offers economic advantages and represents a potential alternative to fattening rabbits in tropical rural conditions.
Conclusion
Results found in this study indicate that the use of green foliage of tropical forage species such as E. poeppigiana and M. alba in the New Zealand rabbits bred in the Ecuadorian littoral for fattening, is an alternative food option as an unconventional raw material to help improve the sustainability of these production systems; this leads in turn to lower food costs and maintains productive rates in conditions of the Ecuadorian humid tropics.
