Growth performance and nutrient digestibility of growing rabbits fed diets containing palm press fibre as a replacement for wheat offal

E A Adeyeye¹, O A Adeyeye², A T Amos¹, O P A Idowu², D U Kareem¹, O T Orbugh¹ and A O Oso¹

¹ Department of Animal Nutrition, Federal University of Agriculture, P M B 2240 Abeokuta, Nigeria
adeyeyeea@funaab.edu.ng
² Agricultural Media Resources and Extension Centre (AMREC), Federal University of Agriculture, P M B. 2240 Abeokuta, Nigeria

Abstract

A study was conducted with growing rabbits to determine the growth performance and nutrient digestibility using palm press fibre (PPF) as a replacement for wheat offal (WO). Forty (40) un-sexed hybrid growing rabbits with initial weight range (712.50-812.50g) were used. The rabbits were acclimatized for a week during which commercial chicken grower mash was fed. A grower diet was formulated and the WO in the diet-T1 (PPF0) was replaced at PPF25 (T2), PPF50 (T3), PPF75 (T4) and PPF100 (T5). The rabbits were weighed individually and was distributed on weight equalization to the five dietary treatments which was replicated four times with two rabbits per replicate. The experimental diets and water were given ad libitum throughout the study which lasted fifty six (56) days without supplemental forage. Data on feed intake (FI), weight gain, feed conversion ratio (FCR) and mortality were collected for growth performance indices while crude protein (CP), crude fibre (CF), ether extract (EE), ash and nitrogen free extract (NFE) were obtained for nutrient digestibility. Data generated were subjected to analysis of variance (ANOVA). There were quadratic trends in performance criteria as WO was substituted by PPF. At the highest level of replacement of WO by PPF, the performance indices were reduced (p>0.05). Rabbits fed diets containing PPF recorded significant higher CP and ash digestibility when compared with the control (PPF0) group. It was concluded that the traditional fibre source (WO) for growing rabbit could be substituted with PPF up to 100% without adverse effect growth performance and nutrient utilization.

Key words: growth, hybrid, nutrient, rabbit, replacement

Introduction

Rabbit is a monogastric animal with a well-developed caecum that facilitate hind-gut fermentation of fibrous feedstuffs, proximal and distal colon that harbours fermentative microbiota (Irlbeck 2001). Fibres are germane to the functionality of the rabbit gut motility, to this end cellulolytic feed ingredients that are undigested and unabsorbed by other monogastric animals are employed in rabbit nutrition. Dietary fibre is essentially important because it helps in maintaining mucosa functionality and serve as substrate for microbiota (Lukefahr et al 2004). It has been opined (Arijeniwa et al 2000) that rabbits can thrive on all forage diets, however, optimum performance can only be achieved in a mixed feeding regime consisting of forage and compounded diets.

Availability of forages which are the main source of fibre is scarce in peri-urban making rabbit nutrition herculean task to producers. The processing of composite ration with optimal level of fibre is inevitable in this regard. For several decade, wheat offal (WO) has been used as a conventional source of fibre in monogastric nutrition. The high cost of formulated concentrates and pelletized feeds compounded from this traditional fibre ingredient militates against increased rabbit production (Agunbiade et al 2001). Therefore, substituting with under-utilized unconventional feedstuff that is readily available at low cost could be an alternative, partially or totally replacing the expensive conventional feed ingredient (WO). One of such readily available fibrous materials is palm press fibre (PPF).

Palm press fibre (PPF) is the by-product of palm oil industry and available in all palm oil processing facilities in Nigeria. It is gotten when the oil in the palm fruits has been extracted and the kernels separated, the left-over fibre is called PPF. Houndonougbo et al (2012) reported that PPF contains high levels of crude fibre and ether extract (36.4 and 21%) with low crude protein (4%) and minerals contents (0.31% calcium and 0.13% phosphorus). They opined that PPF can be dried and pelleted to overcome the problems of poor keeping quality and bulkiness (Collingwood 1958). It has been reported (Houndonougbo et al 2012) that PPF can be employ in the diet of growing rabbits up to 15%. However, the potential utilization of PPF in the nutrition of growing rabbits has not been well researched. Therefore, it is hypothesised in this present study that PPF should be able to replace certain proportion of WO in the diets of growing rabbits. Its usage will not only lower the cost of production but add to the profitability of the palm oil processing industries and reduce the environmental impact.

Materials and methods

Study area

The experiment was carried out at the Rabbit Unit of the Directorate of University Farms (DUFARMS), Federal University of Abeokuta, Ogun-State, Nigeria. The farm is located in the tropical rainforest vegetation zone of South-Western Nigeria on latitude 7°10´ N and longitude 3°2´ E. The prevailing climate is tropical humid with an average annual rainfall of 1037 mm and a mean ambient temperature of about 34.7°C (Federal University of Abeokuta Meteorological Station).

Ethical approval

Animal Ethics Committee guidelines of the Federal University of Agriculture, Abeokuta (FUNAAB 2014) was strictly adhered to throughout the duration of the experiment.

Sourcing of test ingredient

The test ingredient (PPF) was obtained from the Palm Oil Enterprise of FUNAAB Integrated venture (FIV). The PPF was separated from the kernel and sun‑dried by spreading thinly on a clean concrete slab for five consecutive days (till constant moisture of 10–11%). The dried PPF was milled using a hammer mill and was passed through a 2 mm sieve and stored in air tight container

Experimental diets and design

Five (5) experimental diets were formulated according to the recommendation of NRC (1994), such that PPF was included to replace wheat offal (WO) at 0, 25, 50, 75 and 100% levels in diets 1, 2, 3, 4 and 5 respectively. Hence, the experiment was arranged in a completely randomized design. The gross composition of the experimental diets are presented in Table 1.

Management of experimental rabbits

Forty (40) un-sexed hybrid growing rabbits with initial weight range (712.50-812.50g) were obtained from a reliable farm. The rabbits were acclimatized for a week during which commercial chicken grower mash was fed. The rabbits were weighed individually and was distributed on weight equalization to the five dietary treatments which was replicated four times with two rabbits per replicate. The experimental diets and water were given ad libitum throughout the study which lasted fifty six (56) days without supplemental forage.

Data collection

Proximate composition and fibre fraction

The proximate composition of the test ingredient (PPF) was carried out according to AOAC (2000) and fibre fraction by Van Soest et al (1991)

Growth performance

Initial body weight (g/rabbit) was obtained before the commencement of the experiment.

Weekly live body weight was measured and average daily weight gain per rabbit was calculated as total final body weight - total initial body weight divided by the number of rabbits in a replicate. Daily feed intake (g) was obtained as the difference between quantity of feed given the previous day and the left over and divided by the number of rabbits in a replicate. Feed: gain ratio (FGR) was calculated as the ratio of daily feed intake and daily weight gain.

Mortality was recorded as it occurred, and mortality percentage was calculated as number of dead rabbits divided by total number of rabbits stocked multiplied by 100.

Digestibility trial

At the end of the experimental period, a digestibility trial was conducted for 7 days. A rabbit per replicate was picked and taken to the metabolic cage which was cleaned and disinfected. Three (3) days acclimatization was carried out during which respective diets were given. After acclimatization, a known quantity of feed which was a little above their daily feed intake was offered. The excreta void was collected, weighed and oven dry. The process was repeated for three (3) days. The dried sample was pulled together (after weighing) according to replicate samples, faecal and the palm press fibre was analyze according to AOAC (2000).

Statistical analyses

Data were subjected to One-way Analysis of Variance (ANOVA) in a Completely Randomized Design using General Linear Model procedure of the SAS version 9.0 software package for windows (SAS, 2002). Means of significant results was compared by Duncan Multiple Range Test of the same package.

Results

The proximate composition of PPF (Table 2), indicated that it contains minimal level of crude protein (CP), low proportion of ash and Acid detergent lignin (ADL), moderate levels of ether extract (EE), crude fibre (CF) and Acid detergent fibre (ADF) with high percentage of neutral detergent fibre (NDF).

Growth performance

Results of growth performance, table 3 and figures 1-3 shows that there were slight quadratic trends in performance criteria of the growing rabbits as wheat offal (WO) was substituted by palm press fibre (PPF). At the highest level of replacement of WO by PPF, the performance indices were reduced although, there were no (p>0.05) different among the treatments.

Figure 1. Effect of replacing wheat offal with palm press fibre on average final weight (AFW) of growing rabbit	Figure 2. Effect of replacing wheat offal with palm press fibre on average daily weight gain (ADWG) of growing rabbit

Figure 3. Effect of replacing wheat offal with palm press fibre on feed conversion ratio (FCR) of growing rabbit

Digestibility

Results of digestibility (Table 4), rabbits fed diets containing PPF recorded (p<0.05) higher crude protein (CP) and ash digestibility when compared with the control (PPF0). Other parameters examined were not (p>0.05) affected by the treatments.

Discussion

The proximate composition and fibre fraction of the palm press fibre (PPF) recorded in this study is at variance with the report of Wan Zahari et al (2000) and Houndonougbo et al (2012). Values for crude fibre and ether extract reported in this present study are higher than values reported by these authors except crude fibre (41.2 %) by Wan Zahari et al (2000). Also, NDF and ADF reported in this study are lower than 84.5 and 69.3 % revealed in the findings of Wan Zahari et al (2000). The discrepancies in these reports could be as a result of composition and residual oil in the fibre due to method of oil extraction (manual presser).

The non-significance difference in the growth performance among the treatment group is an indication that the test ingredient (PPF) is sufficient to meet the nutrient need of the growing rabbits. This result is in tandem with the report of Houndonougbo et al (2012) who found no significant difference in growth performance of growing rabbits fed diets containing varying levels of PPF. In addition, Mafimidiwo et al (2022) recorded significance difference only on feed intake which decreased as the level of urea-molasses treated corn cob was increased in the diet. Similar to these findings was the report of Sobayo et al (2008) when growing rabbits were fed with fermented maize milling waste. In like manner, Ajimohun et al (2024) stated that graded levels of Millet offal as a replacement for wheat offal in the diets of weaner rabbits did not influenced growth performance. The similarity of these findings could be as result of higher fibre content of the materials. It has been established (Combes et al 2013) that dietary fibre is very important in rabbit nutrition because of its role in feed intake and proper functioning of the gastrointestinal tract. Therefore, an optimal level of fibre and adequate balance of digestible fibre should be maintained. This is an indication that PPF can substitute WO up to 100% in the diet of growing rabbit.

The improved ash digestibility reported in this present study is in agreement with Osho et al (2013) which found improved ash digestibility with growing rabbits fed diets containing optimum fibre and digestible energy. However, Mafimidiwo et al (2022) observed elevation in ash digestibility of rabbits fed the control diet compared with rabbits fed varying levels of urea-molasses treated maize cob (UMTMC). The improved CP digestibility reported in this study did not agreed with the report of Mafimidiwo et al (2022) who found no significant difference among the treatments. The improved CP digestibility with rabbits fed diets containing PPF could have explained similar growth performance across treatments. This suggest that the rabbits utilized the nutrients in the PPF similarly as WO in the control diet (PPF0). It has been reported (Gidenne and Perez 2000) that diets with high NDF (hemicellulose) are well digested by rabbits because they have high utilization for these fibre fractions. The result of the fibre fraction of PPF showed that the proportion of digestible fibre (NDF) is high which could further explained the improved nutrient digestibility with rabbits fed diets containing PPF.

Conclusion

In the time of feed stuff crises, the traditional fibre source (WO) for growing rabbit could be substituted with palm press fibre (PPF) up to 100% without adverse effect growth performance and nutrient utilization.

Acknowledgment

The authors are grateful to Palm oil processing unit, FUNAAB Integrated Venture (FIV), Federal University of Agriculture Abeokuta (FUNAAB), Abeokuta, Ogun state for the supply of the palm press fibre used for the study.

Conflict of interest

The authors declared no conflicts of interest with respect to research, authorship and publication of this article.

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