Effect of palm oil and soya bean oil on growth performance and health of rabbit before and after weaning

Abstract

This study was to verify the impact of the nature of the fat introduced into the feed pellets on growth performance and health of rabbits before and after weaning. Three hundred and sixty rabbits of mean weight 50±1 g and from 40 litters were divided into two groups of 60 rabbits. The experiment was repeated three times. The two groups were fed with two feeds that differ in the nature of the fat introduced into the feed. In the first group, the feed contains 3% of palm oil and the second batch, 3% of soya bean oil. Both oils were characterised and the average weight, the growth rate and the health risk of young rabbits were evaluated before and after weaning. The results show a better performance of rabbits fed soya bean oil compared with those fed palm oil. Before weaning, the rabbits of the group containing soya bean oil showed an average growth of 136.75 g/week and a health risk of 20% against 135.75 g/week and 23% for the batch containing palm oil. After weaning, the average growth and the health risks are respectively 181.25 g/week and 7.5% for the group containing soybean oil against 223.75 g/week and 17.5% for the lot containing palm oil.

Keywords:

• soya bean oil
• palm oil
• growth performance
• health
• rabbit
• weaning

1. Introduction

The breeding of rabbits is currently very profitable, because rabbits require little capital and provide a good quality meat. Rabbit meat is considered as a meat diet because it provides little fat in food (Combes 2004). Despite the dynamism of the livestock sector of the rabbit, many problems remain unsolved. It is the rabbit's digestive health. In fact, digestive disorders appear frequently and result to heavy use of antibiotics in livestock rabbits (Lebas 2005). In this context, farmers and consumers should find alternative strategies to improve the health and growth of animals. Strategies to prevent these conditions are implemented. These are the development of medical prophylaxis, control of the overall conduct of livestock (renewal of breeders, rate of reproduction, feeding programs, etc.). Among these solutions, the feeding appears as an interesting idea. In fact the fundamental role of the food is to provide the organism with nutrients necessary for its maintenance needs, growth and eventually production (lactation, pregnancy, etc.). A food must guarantee appropriate health status of the rabbit (Gallois 2006). Moreover, the immune system is regulated by many hormones including the level of secretion that is dependent on nutritional factors (Klasing and Leschinsky 2000). Like all monogastric animals, many nutrients are implicated in the development of animals (Mourot and Hermier 2001). These include, dietary fatty acids that are of significant interest to the rabbits. Fatty acids are carboxylic acids with aliphatic chains found in animal and vegetable fats, oils or waxes esterified form. These fatty acids may influence animal performance (Lessire 1999). According to Lessire et al. (2003), the work done in poultry has shown that the development of the chicken depends in part on the nature of the fat used in the feed.

If the nature of the fat influences the development of the chicken, what about other monogastric animals such as rabbits?

The objective of this study is to compare the influence of two different vegetable fats on health and growth performance of rabbits before and after weaning.

Both vegetable fats concerned are palm oil and soya bean oil. In fact in Ivory Coast these oils are produced in large quantities. They are also regularly used in animal feed.

2. Material and methods

2.1. Material

2.1.1. Animals

The study was conducted on 360 New Zealand rabbits, one day aged and a body weight of 50±10 g. The rabbits were divided into two (2) groups of 60 rabbits. The experiment was repeated three times.

2.1.2. Raw materials for feed formulations

Corn, soya bean, palm oil, cotton seeds and shells of oysters were purchased at the big market of Abobo, wheat bran was obtained from Grand Mouin d'Abidjan (GMA), rice straw and rice bran were purchased from SODERIZ Agboville. Cocoa husks were supplied by the CONDICAF company. Methionine, lysine, vitamin premix and Dibasic calcium were purchased from PROVETO. Oxyboldine was bought at a drugstore pharmacy.

2.2. Methods

2.2.1. Feed formulation

The feed formulation called soya bean oil and palm oil is detailed in Table 1. The granulation was carried out using as a binder solution of sugar at 50 g/l (water). Soya bean meal and cotton are used after oil extraction using a mechanical press. Extraction was done at 140°C to destroy soybean trypsin inhibitors and cotton gossypol.

Table 1. Feeding ingredients and chemical composition.

Ingredients (%)	Palm oil batch	Soya bean oil batch
Corn	19	19
Wheat bran	12	12
Rice bran	12	12
Rice straw	10.5	10.5
Cocoa shell	20.50	20.50
Soya bean meal flour	17	17
Palm oil	03	–
Soybean oil	–	03
Shells of oysters	0.9	0.9
Cotton waste cake	3	3
Premix*	2.1	2.1
Energy (kcal/kg)	2441	2441
Crude protein (%)	16	16
Fat (%)	2.4	2.4
Crude fibre (%)	15	15
Calcium (g/kg)	0.9	0.9
Total phosphorus (g/kg)	0.45	0.45
Sodium (g/kg)	0.2	0.2
*Premix (lysine 0.25%; methionine 0.1%; phosphate bi calcique 0.6%; vitamin premix 0.6% vitamin total 0.05%).

2.2.2. Determination of the average weight

The average weight (AW) is the ratio between total weight of subjects (TWS) in a given batch and the number of subjects (NS) of this batch (Lebas 2007).

2.2.3. Determination of the average weight gained

The average weight gained (AWG) is determined weekly. It represents the difference between the average weight (AWc) of the current week and that of the previous week (Lebas 2007). It is determined as follows:

AWG: average weight gained (g)

AWp: weight of the previous week (g)

AWc: average weight of the current week (g)

2.2.4. Determination of the growth rate

The growth rate represents the ratio between weight gained and growth period (Lebas 2007).

GR = Growth Rate (g/week)

2.2.5. Determination of the rate of mortality

The rate of mortality is the ratio between the number of the dying animals and the initial total number of subjects in the batch multiplied by 100 (Lebas 2007).

2.2.6. Determination of morbidity

The morbidity rate is the ratio between the numbers of animals sick on the total number of original subjects in the trial multiplied by 100.

2.2.7. Determination of the health risk (HR)

The health risk is the combined rate of mortality and morbidity.

2.2.8. Chemical analysis

Chemical analysis of feeds was performed. The dry matter, organic matter, ash, phosphorous (P), calcium (Ca), potassium (K), sodium (Na) and lipid content were determined by the method AOAC (1990). The neutral detergent fibre, acid detergent fibre, hemicellulose and the cellulose were determined by the method of Van Soest et al. (1991). The nitrogen content was determined by the method of Kjedahl (AOAC 1990). Crude protein was calculated by multiplying the nitrogen content by 6.25. The energy has been determined by calorimetry. As for the fatty acid composition, it was determined by gas chromatography using the method developed by Park and Goins (1994).

2.2.9. Statistical analysis

Analysis of variance (ANOVA) 6 was used to compare weight gains, the index of consumption and the average weights obtained with each type of feed with the statistical software. The comparisons at the 5% were made with DUNCAN test. For the comparison of morbidity, mortality and health risks, it was carried out according to the Student test.

3. Results and discussion

3.1. Results

3.1.1. Chemical characteristics of palm oil and soya bean oil

Chemical analysis of both oils is recorded in the following.

These two oils differ in acidity than the observed values are still low compared with acid oils. However, the value of palm oil is higher. The fatty acid profiles are also very different. Indeed, palmitic acid represents nearly half of the fatty acids of palm oil (45.1%) against only 11.2% in soya bean. Palm oil is also richer in oleic acid than soya bean oil (38.3% against 21.7%). In contrast, soya bean oil is best provided in linoleic acid than palm oil (53.4% against 9.8%). The polyunsaturated fatty acids represent 61.6% of total fatty acids in soya bean oil against 10.1% in palm oil. Palm oil is best provided in total saturated acids than soya bean (51.2% against 16.3% for soya bean). Soya bean oil is 26 times richer in alpha linolenic acid than palm oil (Table 2).

Table 2. Chemical composition of palm oil and soybean oil.

	Palm oil	Soya bean oil
Acidity (%)	5.8±0.7	0.3±0.1
Fatty acid% total fatty acids
C12:0 lauric acid	0.2±0.1	0,09±0.02
C14:0 myristic acid	1.2±0.2	0.1±0.05
C16:0 palmitic acid	45.1±0.5	11.2±0.3
C18:0 stearic acid	4.2±0.2	4.1±0.1
C18:1 oleic acid	38.3±1.2	21.7±0.8
C18:2 linoleic acid	9.8±0.7	53.4±1.3
C18:3 α linolenic acid	0.3±0.1	8.1±1.1
C20:0 arachidonic acid	0.5±0.2	0.4±0.1

3.1.2. Growth and health parameters of the rabbits before weaning

Average weight based on the oil incorporated into the feed. The average weight of rabbits over time is shown in Table 3. It appears from the analysis of this table that the average weights of rabbits increased with time whatever nature of the oil incorporated into the rabbits feed. From birth to their third week of life, the rabbits whose mothers ‘feed contains palm oil and those whose mothers’ feed contains soybean oil have a similar growth. But after the fourth week, the rabbits fed soybean oil had higher growth than those fed palm oil (Table 3).

Table 3. Variation of average weight of young rabbits before weaning.

	Average weight (g)
Period	Palm oil batch	Soya bean oil batch
1st week	53±4.5^a	52±4^a
2nd week	133±7^a	132±3.5^a
3rd week	268.5±12^a	268±11.5^a
4th week	431±9.5^a	432±11^a
5th week	596±13^a	600±21^b
The same letter on the same line means that, there is no significant difference between the batches.

Growth rate based on oil incorporated into the feed. The growth rates of rabbits with time are shown in Table 4. It appears from the analysis of this table that the growth rates of young rabbits increased with time whatever nature of the oil incorporated into the feed of rabbits. From birth to their third week of life, the rabbits whose mothers ‘feed contains palm oil and those whose mothers’ feed contains soya bean oil have a similar growth rate. But, after the third week the rabbits fed soya bean oil had higher growth than those fed palm oil (Table 4).

Table 4. Growth rate of young rabbits before weaning.

	Growth rate (g/week)
Period	Palm oil batch	Soya bean oil batch
1st Week	80±5^a	80±4.3^a
2nd week	135.5±7^a	136±5^a
3rd week	162.5±10^a	163±11.5^a
4th week	165±13^a	168±16^b
The same letter on the same line means that, there is no significant difference between the batches.

Status of health of young rabbits before weaning. Table 5 shows the values of mortality, morbidity and health risk of young rabbits before weaning. The mortality rate is the same whatever the oil used. However, rabbits fed palm oil have a high morbidity and an index of health risk than those fed soya bean oil (10% against 6.66% for morbidity and 23.33% against 20% for health risk) (Table 5).

Table 5. Status of health of young rabbits before weaning.

	Palm oil batch	Soya bean oil batch
Number of dead	8	8
Mortality	13.33%	13.33%
Number of sick	6	4
Morbidity	10%	6.66%
Index of health risk	23.33%	20%

3.1.3. Growth and health parameters of the rabbits after weaning

Average weight based on the oil incorporated into the feed. The average weights of young rabbits after weaning are shown in Table 6. It appears from the analysis of this table that the average weights of rabbits increased with time whatever the nature of the oil incorporated into the feed of rabbits. All along the fattening (after weaning), the rabbits fed soya bean oil have a high growth compared with those fed palm oil (Table 6).

Table 6. Evolution of average weight after weaning.

	Average weight (g)
Period	Palm oil batch	Soya bean oil batch
1st week	736±21^a	748±25^b
2nd week	890±16^a	908±24^b
3rd week	1057±24^a	1088±30^b
4th week	1237±18^a	1283±25^b
5th week	1461±20^a	1643±30^b
The same letter on the same line means that, there is no significant difference between the batches.

Growth rate of young rabbits after weaning. The average growth rates (after weaning) are shown in Table 7. It appears from the analysis of this table that the growth rates of young rabbits increased with time whatever the nature of the oil incorporated into the feed of rabbits. The variation of the growth rate is low for two batches of rabbits in the first week. Outside of the first week, the growth rates are high and even higher than those of young rabbits before weaning. All along the fattening, the rabbits fed soya bean oil have a high-growth rate compared with those fed palm oil (Table 7).

Table 7. Growth rate (g/week) of young rabbits after weaning.

Period	Palm oil batch	Soybean oil batch
1st week	154±20^a	160±24^b
2nd week	167±16^a	180±20^b
3rd week	180±20^a	195±30^b
4th week	224±18^a	360±25^b
The same letter on the same line means that, there is no significant difference between the batches.

Status of health of young rabbits after weaning. Table 8 shows the values of mortality, morbidity and health risk index. These values are different according to the type of the oil incorporated into the feed. The rabbits fed palm oil have mortality, morbidity and health risk index higher than those fed soya bean oil. The mortality of the rabbits fed palm oil is the double of those fed soya bean oil (10% against 5%). In terms of morbidity, the batch fed palm oil has morbidity three times higher than that fed soya bean oil (7.5% against 2.5%). About the index of health risk, it is respectively 17.5% and 7.5% for the palm oil batch and soya bean oil batch (Table 8).

Table 8. Status of health of young rabbits after weaning.

	Palm oil batch	Soya bean oil batch
Number of dead	4	2
Mortality (%)	10	5
Number of sick	3	1
Morbidity (%)	7.5	2.5
Index of health risk (%)	17.5	7.5

3.2. Discussion

The similarity observed on the growth and survival of two batches of rabbits (soya bean oil and palm oil) during the first weeks of life could be explained by the diet constituted largely of milk. Indeed, the rabbits begin consuming solid feed as from the third week of their lives (Hudson et al. 2000). The rabbit like the child born with an important equipment of immunoglobulins transmitted by the mother during the pregnancy period (Brambell 1969).

At the birth, the colostrum and the breast milk complete these antibodies. In addition to its richness in nutrients and high-energy growth factors (epidermal growth factor, insulin-like growth factors 1 and 2, transforming growth factor α and β), the colostrum contains many antibodies. It also contains cells implicated in immune defence, such as macrophages, leukocytes, lymphocytes B and T. These macrophages are able to produce lysozyme, complement components and interferons. The breast milk also transmits the same type of cells and antibodies (Uruakpa et al. 2002). The colostrum and the milk of the rabbit would contain IgG and IgA (Godzińska et al. 1970). The difference at level of average weight, growth rate and the health status of the two batches after the fourth week reflects a strong impact of the fat quality incorporated into two batches on the growth and health performance. This difference confirms that the effect of feed on the digestive functions of the young rabbit is constructed over time (Kelly and Coutts 2000). At the birth, the development of the humoral immune system of the rabbit is not complete. The histological structures of the peripheral lymphoid tissues are immature and antibody production has not started. The antibody response to antigens is minimal until 2 or 3 weeks old (Knight and Winstead 1997). The antibody repertoire must diversify in order to recognise a large number of environmental antigens. This diversification is late in rabbit, in contrast to poultry, sheep and cattle, for which it is initiated before the birth. In rabbits, the diversification of antibodies is not regulated only by ontogenic factors. But external factors such as the microflora and the feed have an essential role. It has even been shown in rabbits with ligated cecal appendix at birth (not contact with the intestinal contents) that the diversification of VDJ genes almost disappeared at 12 weeks old. The genesis of this primary repertoire would be dependent on exogenous factors (Lanning et al. 2000). The good performance of the batch containing soya bean oil would be linked to the feed composition of this batch (mainly fatty acid profile of soya bean oil). The chemical analysis of soya bean oil and palm oil indicates a difference in terms of both fatty acid profiles and in terms of acidity of oils. This composition is in accordance with that stated by Lessire et al. (2003). This difference in composition of these oils incorporated in the feed would justify the differences observed at the level of the average weight, the growth rate and the survival of two batches after the third week of life. In fact polyunsaturated fatty acids represent 61.6% of total fatty acids in soya bean oil against 10.1% in palm oil. However, the structure of fatty acids (carbon chain length and the presence of double bond) has an impact on growth and health of animals (Lessire et al. 2003). The polyunsaturated fatty acids (essential fatty acids) are incorporated into cell membranes to maintain their fluidity. They constitute a barrier function that allows important nutrients to enter cells (Laidlaw 2003). Polyunsaturated fatty acids are essential to all life particular by their presence in biological membranes (Laidlaw 2003). In fact biological membranes are composed mainly by polyunsaturated fatty acids from feed. Dietary polyunsaturated fatty acids are used to renew the phospholipids and to prevent important deterioration of the skin and hair. They are also involved in the cohesion of cells and the formation of tissues and cell membranes. This explains their importance in the growing phase because of the multiplication of cells (Sinclair et al. 2000; Perezet al. 2005; Romieu et al. 2005). According to Brenna (2001), polyunsaturated fatty acids are transformed into substances similar to hormones called eicosanoids, which serve various physiological functions such as growth and cell division. They also have an essential role in regulating of the immune response (Crevel and Saul 1992; Klasing and Leshchinsky 2000[Leshchinsky and Klasing 2000 changed to Klasing and Leshchinsky 2000]; Fortun-Lamorthe and Bouiller 2004). The richness of soya bean oil in alpha linolenic acid compared with palm oil is also an advantage in terms of health for the soya bean oil batch. Soya bean oil is 26 times richer in alpha linolenic acid than palm oil. However, this fatty acid has a specific role. It participates to membrane structures and it is essential for normal growth and biological functions of many tissues (Bourre 2004a). The differentiation and function of brain cells require alpha linolenic acid. Alpha linolenic acid has an important function for the structure of nerve cells (Bourre 1984, 2004b). Many animal experiments have shown that polyunsaturated fatty acids are implicated to the creation and the maintenance of various organs and participate to the prevention of many diseases (Bourre 2005). They are also involved to the mechanisms of some immune responses and seem to have a significant analgesic (Yoshida et al. 2003; Perez et al. 2005). Linoleic acid, the precursor of omega-6, is responsible for the cardiovascular and immune balance (Demaison and Moreau 2002). The low performance observed in the batch of palm oil compared with the batch of soya bean oil is not only related to its low content of polyunsaturated fatty acid but also it could be linked to the richness in saturated fatty acids of this oil. In fact the palm oil is rich in saturated fatty acid.

These saturated fatty acids represent 51.2% of total fatty acids against 16.1% for soya bean. But saturated fatty acids may influence the implementation of the bacteria in the digestive tract. A precocious perturbation of the first sequence of implantation of bacteria in the digestive tract may affect the microbial balance later (Abecia 2006). This perturbation affects the viability of rabbit thereafter (Abecia 2006). The symbiotic microflora of the digestive tract of the rabbit ensures microbial digestion and is also implicated in the digestive health of its host. It provides a protection against potentially pathogenic micro-organisms, stimulates the host immunity and diversification of the repertoire of antibodies (Lanning et al. 2000; Guarner and Malagelada 2003). However, the low-growth rates observed at the first week after weaning for the two batches of rabbits are linked to the stress of weaning and the increase ingested solid compared with milk. During weaning, the mother is separated from the children. The baby rabbits are moved to new cages. The change of cage causes stress that has the low growth as an effect (Gallois 2006). During weaning, the nutrients from milk are removed. While, these nutrients are more digestible than those from the feed pellet. Hence it is normal that these nutritional compensation by ingesting pellets feed will be late. After the period of stress, the increased of the ingestion of pellet quality stimulates the development of animals (Gallois 2006). This explains the fastest growing during the post-weaning compared to the pre-weaning for the two batches. The mortality rates obtained during this study are less than those recommended in rabbits by Cuniculture Magazine (2005). Indeed, the mortality rate obtained during our work is 13.33% for both oils during the pre-weaning. During the post-weaning, mortality rates are 10% for the palm oil and 5% for soya bean oil. But according to Cuniculture Magazine (2005), the mortality rate is 15% before weaning and 10% to 14% in fattening. This difference of mortality may be linked to the different composition of the basic feed and the breeding conditions. In fact the quality of feed, the environmental hygiene and the monitoring are factors that can affect the health of the animal.

4. Conclusion

The nature of the fat used in the formulation of feed pellets has an impact on growth and health of rabbits. Soya bean oil by its essential fatty acid composition improves the performance of growth and survival of rabbits compared to the use of the palm oil, which is rich in saturated fatty acids. The efficiency of soya bean oil on performance of rabbits is best pronounced during the post-weaning than the pre-weaning.