Abstract.

The experiments was carried out with the aim to evaluate the rabbit fattening behaviour under replacement of commercial feed by Leucaena leucocephala hydroforages (LLH) in rabbits of the White New Zealand breed.

The feeding experiment was carried out in the rabbit breeding area of to the Artificial Insemination Enterprise of Bayamo.

One hundred and twenty animals with an average weight at weaning of 740 ± 18 g were divided into four groups in a complete random block design over a fattening period of 60 days. 

In the experiment the first group consumed commercial feed for rabbits (control group) while in group 2; 3; 4 the feed was substituted based dry matter by 25% 50% and 75% of hydroforages. 

The supplied feed based on dry matter was adjusted weekly to a proper amount, considering animals´ age.

Feed consumption per cage was daily controlled, live weight of individual animals were registered once a week at the beginning and at the end of the fattening period.

At the end of the fattening trial the animals were slaughtered and the was determined carcass yield. The feed consumption in experiment (LLH) for the control group was 132 g/d and 140; 154; 160 g/d to the rest treatments respectively; there were found final weight of 2.2 Kg for the control and LLH 25 groups and 1.8 Kg of final weight in the last treatment; the daily weight gain was 26 g/d for both groups ( the control group and LLH 25); and 20 g/d for the third and fourth treatments; it was found yield carcass about 55% for all groups.

1. Introduction.

There’s an increasing differences between population and the land production possibilities and at the same time such differences is also present between life status in the developed countries and the status existing in developing countries.

In the latest do not exist correspondence in regarding the high food demand and the poor possibilities for produce (Brown and Kane, 1994).

Nowadays there are at about 840 millions in habitant in the world wide (Gear et al, 2007); it is estimate a tendency for the world population to increase at a rapid rhythm and it is expected an increasing of a 8500 millions for the year 2025; more than 93% of the increasing will take place in the developing countries (Ensminger et al., 1995).

Rabbit meat is one alternative protein source in family diets in the rural areas and the availability and development of a production system for small-scale farms should be a policy of major interest. Rabbit breeding in Cuba is not only an alternative protein source for the families, but also a source of monetary profit by marketing the products, meat and skins as well.

Rabbit meat has a high dietetic value (Lebas et al., 1986). It contains 21 % protein, 1.3% fat, low levels of cholesterol (31.1mg/kg) and is highly digestible. In comparison to other meat, the low cholesterol and fat content is remarkable (Roca, 2007).

The reproductive behaviour of rabbits is extremely high Leyva, (1967) and Camps, (2002) calculated that meat production capacity is higher for traditional livestock (sheep, cattle, pig). Rabbits as herbivore animals which can be fed with hay, forages, by-products and household waste and those are not in competition to human food  (Riverón et al., 2003; Finzi, 2002),

In Latin American countries such as Mexico, Argentina, and Chile the hydroforage feed production technology is very well established. The production of hydroforage feed plants has especially several advantages in urban and peri-urban areas. It is saving space, the yield is about 15kg fresh forage/m2 and harvesting is possible after 9-15 days.

The biomass has a high sanitary status and improved feed quality as Lobera et al., (1991) analyzed. The content of antinutritional components was lower than in traditional grown plants. It is water saving and waste and by products can be used as substrate for growing other plants.

The objective of this experiment was to determine rabbits´ growth performance and meat quality parameters when commercial feed was replaced by different amounts (25, 50 and 75%) of hydroforage Leucaena leucocephala.

2. Materials and Methods.

The experiment was done in the rabbit breeding area in the Artificial Insemination Enterprise of Bayamo, Cuba.

Two feeding experiments were carried out with Leucanea lecucephala hydroforage (LLH) as a supplement of a commercial rabbit feed. The average temperature (minimum and maximum), and humidity during the experimental period in 2006 in Bayamo region was:  24.2°C and 33.2°C; 78% in average respectively (CITMA, 2006).

2.1 Feed production.

The seeds of Leucaena leucocephala were collected in the area around the experimental station. The seeds of Leucaena were harvested according to Funez et al., (1988) from the trees, when the color of the hulls changed from green to brown.

After sun drying, the hulls could be opened easily. Before sowing the seeds, they were soaked for 24 hours, and afterwards they were washed and dried. The planting density was 2 kg seeds/m2.

The seeds were placed in perforated metallic trays, 0.3m2 in size, between two substrate layers of 1cm thickness consisting of grinded (3mm) sugar cane material. The sowing was daily done over a time period of 60 days with the delay in time compared to the feeding trial.

Every day at 4.00 p.m. the planting was watering. Harvesting time was after 21 days twice a day.

2.2 Housing of animals.

Animals were placed in galvanized wire cages (5 animals in each one). The cages dimension was 0.76 m x 0,76m x 0.45m. These cages were put in line and at 1.5m from the floor, separated at 0.5m from the wall, and at 2m from the roof.

2.3 Experimental design and animal feeding

The rabbits were weaned at the age of 35 days with 740 ±18g of body weight and adapted for 7 days to the control feed and to the alternative feedstuff; the different treatments were constituted before feeds adaptation. Animals, in experiment received experimental diets with LLH, the last 35 days of the 60 day fattening period.

One hundred and twenty rabbits of the White New Zealand breed after adaptation were divided into four groups with 6 replies in each group and 5 animals per cage in a random complete block design.

Diets consisted of commercial pellet concentrated feed alone (control group) or replaced by 25%, 50% and 75% of hydroforage on DM basis (group LLH25, LLH50 LLH75). The composition of the commercial feed is illustrated in table 1.

Table 1. Composition of the commercial feed

The feed amount supplied (on DM basis) was calculated weekly, considering the animals´ age according to Maertens et al, (1998), under considering that feeding forages needs a higher amount due to material losses and nutrient density. Feeding was twice a day at 9:00 and 16:00 hours.

The hydroforage was harvested daily immediately before feeding. Water was provided ad libitum. The feed consumption of the two components was registered daily.

The animals were weighted at the beginning and at the end of the experiments, and during the course of the experiments, the measurement was once per week.

At the end of the fattening period, rabbits were slaughtered and the carcass was analyzed according to the method described by Blasco et al, (1990). There were controlled carcass weight, carcass yield, fore quarter weight (FQW), intermediate part of carcass (IPC) and hind quarter weight (HQW) the parameters.

2.5 Chemical analysis.

Feed chemical composition was given by feed factory of Bayamo. The hydroforages chemicals analysis, including the Ca and P content was done according to the standard AOAC methods (1995) in Jorge Dimitrov Research Institute.  

2.6 Calculation and statistical analysis

The metabolizable energy of the feed (1) and the hydroforages (2) was estimated by the following formulas (Garcías et al., 1989).

ME (Mcal/kg DM)= 3260+0.455 CP-4.037 CF+3.517 EE.

ME (Mcal/kgDM)= 2.66 –0.0199x(%CF)

                     1Mcal = 4.187 MJ

The feed conversion and daily gain was calculated according to Corso et al., (1997).

The experimental design was a complete random block design. 

Data processing was done with the statistic program, version 4.3 (Stat Soft, 1998).

By means of applying a variance analysis of simple classification for each one of the replies and for media comparison, it was used the Duncan test (1955).

The statistical model was:      Yij= M + Ti + E ij

Yij :  i – epsimo treatment observation of the j- epsimo repetition.

M : Effect of the general middle.

Ti : Effect  of the i – epsimo  treatment.

E ij : Effect of the random error.

3. Results and Discussion.

The nutrient content of the hydroforages and the control diet is shown in table 2.

The commercial rabbit diet is in accordance with the nutritional requirements of growing rabbits (Riverón et al. 2003; De Blas and Mateos, 1998). Hydroforages has lower calculated energy contents by 25% compared to the control diet. The CP content is double in LLH and 25% compared to the commercial feed. LLH has a high Ca content and a wide Ca: P ratio. The total energy content in the different feedstuff is not really big, but it is a little low in the diets when the hydroforage levels increased. Control feed has an aminoacids composition according to rabbit requirement (Ensminger et al., 1995), but hydroforage has low essential aminoacids content (Metheonin and Cystin).

Table 2.  Nutrient content of the feed components g/kg DM

LLH: Leucaena leucocephala hydroforage.

The levels of metabolizable energy contained in the commercial feed are in correspondence with the levels required for the growing rabbits according to Ensminger et al., (1995), which recommends a metabolizable energy in the order from 10 to 12 MJ/kg MS contained in the feeds for young rabbits; in the diets where the hydroforage was included the tendency of this nutrient was diminishing according to the hydroforage inclusion percent, this element affected the fattening period in the finish phase.

As reviewed by Parigi Bini (1988) and Lebas, (1989),different estimates of digestible energy requirements for maintenance of growing rabbits has been found, varying from 10.5 MJ/Kg DM to 12 MJ/ Kg DM  in New Zealand rabbits.

An increasing in the level of dietary energy intake can also affect composition of body gain and the partition of energy retained as protein and fat.

The body composition changes are not linearly correlated with digestive energy, because some constituents (fat) tend to increase more than proportionally, the maximum average daily growth is achieved when the digestive energy concentration is between 11 and 11.5 MJ/KgDM (Partridge et al., 1989).

The minerals levels in the control diet and the rest diets are according to the minerals requirements growing rabbits (Ca - 0.5% and P - 0.3 % in ratio), stated by Ensminger et al., (1995) and Ponce the Leon et al, (1998). No diets exceeded the mineral requirements but, no one remained below these.

Calcium, phosphorus, and magnesium are minerals which take part in many functions, especially in blood composition, bones, and process related with energy and physiology nervous system control.

Other minerals are required in the diet in less quantity, but they are also important: cooper, zinc, manganese, selenium, and others, which play their role in life and reproduction (Vinent, 2003).

Table 3 illustrates the feed and nutrient consumption during the whole experimental time of 60 days and the protein and fibre content in the consumed diets. 

The feed consumption by the control group was equal with 5.2 kg feed/ kg average live weight for the whole fattening period. The control groups had a feed intake about 130 g/d. 

The exchange with hydroforage shows different trends in total feed consumption (150 g/d). Feeding LLH increased the feed intake with increasing ratio of LLH in diet. As the ratio of hydroforages in the consumed diets indicates, there was a selection in favour of the control feed in experiment.

The protein intake in experiment one increased at 180% in LLH 75 compared to the control group. With 26.5% CP in diet in this group a large protein surplus over the requirements do exist.  The decrease in fibre content is not remarkable.

Table 3.  Total DM intake, hydroforage consumption and nutrient contribution in both experiments during the whole experimental period (60 days)

Non significance difference (n.s.) P<0.05; means with different superscripts (a, b) within the same columns differ at P<0.05.  LLH: Leucaena leucocephala hydroforages.

In relation to the amount of protein in the ration in this experiment, the concentrated feed cover the requirements for this nutrient to the animal category of fattening according to De Blas and Mateos, (1998), these authors argued that, the protein has to be 17% of the ration, but this nutrient is in excess in the diets of the groups from two to four in experiment one.  When diets contain protein values above 20%, it can increase the disorder metabolic; it is the condition to allow the presence of Clostridium and E. coli (Gidenne, 1997).

In other studies carried out by García -Palomares et al., (2006), they have indicated that, an increase of the nitrogen flow reaching the terminal ileum incremented the populations of Clostridia spp.

The level and source of plant protein included in starter diets also have an influence on intestinal disorders, as a decrease of dietary protein content or an increase in ileal protein digestibility reduced the flow of protein towards the fermentative area and decreased the mortality  (Carabaño et al., 2008);

In the case of crude fibre content in different rations, the commercial feed had the levels of fibre that the animals needed according to above mentioned authors, that recommend between 13 – 14 % of crude fibre.

The live weight, at the beginning and at the end of the fattening period, the daily live weight gain and feed conversion ratio, is illustrated in table 4 for the complete period last 35 days of fattening (excluding the 7 days adaptation period).

During the complete fattening period, the final live weight and daily live weight gain in control group, and 25% substitution groups in experiments showed no significant differences; the final live weight for the third and fourth groups reached the 87% and 80% one respect to control group. With increasing amount of hydroforage in the diet, the final body weight and daily live weight gain, decreased significant with great differences. The feed conversion ratio worsened significant with increasing amounts of hydroforages in the diets.

In the last 35 days of fattening period, the daily live weight gain diminished in all treatment groups and feed conversion ratio increased 1kg per kg gain compared to the total experimental time, in the last stage of the experiments the third and fourth treatments the feed conversion ratio was 4.5.

Table 4. Body weight, weight gain and feed conversion ratio of rabbits fed different amounts of hydroforage during the whole experiment and the last 35 days (d) of fattening period.

non significance difference (n.s.) P<0.05; means with different superscripts (a, b) within the same columns differ at P<0.05. LLH: Leucaena leucocephala hydroforage.

When the live weight gain of the control group is analyzed during the fattening period, it was found that the daily gain at the beginning of the experiment was about 34 g/d similar values to the ones established for rabbits of the New Zealand breed (De Blas et al., 1998), with environmental temperature from 15° C to 22° C, and metabolizable energy levels of 10 MJ/kg DM - 11.5 MJ/kg DM; they established  live weight gain of 33 - 38 g/d in a period from 35d to 45d of animals´ age, but from the 60 days of age to the end of the experiment these values were diminished gradually, they were becoming  lower with regard to the values of live daily gain reported by the authors mentioned, which have established a live weight gain of 36 g/d during the whole period.

Live weight gain was lower in the treatments where the animals were fed with higher levels of hydroforage, probably because of the low presence of essential aminoacids in the hydroforage. 

According to Ly and Macias, (1995), who stated that Leucaena has great content of essential aminoacids, except metheonin and cystin (0.1% and 0.2% respectively); however, this behavior is in relation to what Ponce de Leon et al., (2002) achieved, who stated that in the specialized enterprise, the fatten period occurs between the 35 days (weaning whit 600 and 700g of living weight) to 91 days with daily middle gain 15 to 21g/d for New Zealand White rabbits and others rabbits breeds.

This increase according to the authors is reached with diets of 60:40 feed - forage, although with feed ab libitum is possible to obtain 30g/d between 90 and 100 days age.

Gains lower than 20 g/d were also reported by Abdel-Ghany et al., (2000) in Egypt for New Zealand White rabbits under warm climatic conditions.

The values of daily gain weight are low in treatment 3 and 4, this results, may be, due to the low dry matter content of the diet. Other reason could be done for the low energy content in the experimental diet; it was of paramount importance to the growing rabbits at the last experimental period.  Higher results to the ones achieved in this experiment, were reported by Ponce de León (2002), feeding the animals with different levels (10; 15; and 20% of inclusion) of dehydrated citric pulp.

The low indexes of conversion shown for the last experimental groups are explained for the lowest weight gain of these which may be influenced for the low percentage of hydroforage dry matter which in the case of rabbits should be between 3 to 3.5 to be considered as good according to what has been stated for others authors. 

Nieves, et al. (2002) evaluated the Leucaena leucocephala and Arachis pintoi foliage acceptation in White New Zealand rabbits in fattening stage. They estimate dry matter consumption values of 73.95 g/d (SE± 0.96); 73.26 g/d (SE ± 1.24); 58.16 g/d (SE ± 6.45) and 63.21g/d (SE ± 4.25).

When comparing the percentage of daily gain weight different groups respect to the control one, it is observed that the treatment LLH 25% achieved a 86.23% of the weight reached for this, the LLH 50 reached 64.24%, and LLH 75 the 58.30%. The final weights were affected when increase the hydroforage levels, it is due to difference concentration of the nutrients in the ration, in this case, the protein was too high in the diet. In the case of the protein in the experiment LLH the consumptions of this nutrient was very high and was poor in experiment two, generally, when the protein levels are low (11%), it produces worse growth indexes, and above (20%) it causes complications in the digestive processes of these animals (Savón, 2002).

After 60 days of age, a deterioration in the animals growth rate were observed, these values of live weight were less in relation with the standard growth curve described by Meartens et al., (1998). Never the less the animals of experiment one reached their final weights a little higher than the animals of experiment two.

These final weight value results of the rabbits are similar than the ones got for Ruiz-Feria et al (1998) that using Leucaena leucocephala leaves and cactus (Opuntia sp.) in fresh for New Zealand rabbits in growing stage, experimental diets were 100, 90, 80 or 70% commercial pellets with corresponding levels of 0, 10, 20 or 30% Leucaena leaves (dry matter basis), they reported rabbits final weight of 2.6 Kg to the control group and 2.1 Kg of final live weight to the rest groups.

They stated that, reduced growth performance in forage-fed rabbits may have been attributable to poorer diet quality and/or the adverse effects of toxic compounds, such as mimosine and trypsin and chemotropism inhibitors, and tannins present in Leucaena leaves.

However, growth performance was generally improved at 10 and 20% leucaena levels when cactus was included when it was excluded in the diets.

Binh et al., (1991) feeding the animals with concentrated, rice by-product 23%, middle grain rice 20%, maize 33%, fish meal 2%, popcorn meal 16%, cassava meal 5%, and mineral premixture 1%, obtained a final living weight about 1200g and 1450g, being these lower.

For all carcass characteristics shown in table 5, control group and LLH