Intake, relative palatability index and preference class of selected Bor, South Sudan browse species fed to crossbred growing goats

M T Deng¹, J O Ondiek and P A Onjoro

Department of Animal Sciences, Faculty of Agriculture, Egerton University, P O Box 536, Njoro, Kenya
mamerjohn99@gmail.com
¹ Department of Animal Production, Faculty of Agriculture, Dr. John Garang Memorial University of Science and Technology, Bor, South Sudan

Abstract

A study was conducted to investigate intake, palatability and preference class of the selected five browse species namely: Balanites aegyptiaca, Tamarindus indica, Cordia sinensis, Ziziphus spina-christi and Grewia tenax. Rhodes grass (Chloris gayana) was included as basal diet. In a Completely Randomized Design, four crossbred (Small East African x Toggenburg) growing goats with initial mean body weight (16.6 ± 0.04 kg) and 4-5 months of age were offered the above mentioned browse species each in an individual pen of (1.5m x 2.5m) using a cafeteria feeding approach. This was to determine the browse species DM intake, palatability and preference class.

Results showed that the DM intake (g) and relative palatability index (%) ranked the same as follows in descending order: G. tenax > Z. spina-christi > B. aegyptiaca > C. sinensis > T. indica. Preference class was G. tenax and Z. spina (high>60%), B. aegyptiaca (medium 35-55%) and low (<25%) for C. sinensis and T. indica, respectively. It was concluded that Grewia tenax was the highest in DM intake, relative palatability index and relatively the most preferred whereas T. indica was the least.

Key words: browse species, Cordia sinensis, Grewia tenax

Introduction

The palatability of browse forages is an important factor of goat production, particularly when the forages are consumed to provide a major part of the daily nutrient intake. Yusmadi and Ridla (2008) describe palatability as feed characteristics by organoleptic senses (smell, taste, and sight), texture and temperature, giving rise to stimuli and attractiveness of animal to consume. While preference refers to selection of a plant species by the animal as a feed or is a proportional choice of two or more feeds (Hussain et al 2009).

Due to high cost and deficiency of nutrients in feeds, goat keepers need to be aware of alternative feeds and supplement to meet the requirement for improved nutrition of goats. The challenge is the acceptability of feed materials that are available locally. The desert date (Balanites aegyptiaca), Grewia tenax, Ziziphus spina-christi, Tamarindus indica and Cordia sinensis are common, wide spread and remain green most of the year and provide nutrients such as crude protein, vitamins and minerals that are most often lacking in the dry season. Acceptability of feeds by goats is a predicament in feeding and nutrition. Therefore, the study was to determine intake, palatability and preference class of the selected five browse species as alternative feed resource for goats.

Materials and methods

Browse species collection and preparation

Fresh leaves from branches of the five selected browse species:Grewia tenax, Tamarindus indica, Balanites aegyptiaca, Ziziphus spina-christi, and Cordia sinensis were collected from several stands in the rangeland of Bor County, Jonglei State in South Sudan (figure 1) between November and March 2015. Bor County is characterized by tropical wet and dry climate. It lies between latitude 6^o12ʹ 45ʺ N and longitude 31^o 33ʹ 39ʺ E with an altitude of 407-430m above sea level and annual mean rainfall and temperature of 891 mm and 27.3^oC -33.7 ^oC, respectively (Climate-Data.org, 2013). The fresh leaves of the five selected browse species were harvested separately from several trees or shrubs by hand picking. The browse species were selected based on local farmers' knowledge of the species consumed by goats and also based on their availability throughout the seasons. They were also judged by farmers to be palatable to goats and sheep. The collected forages were air dried in the shade of constant weight for 4 days, then pooled, packed and stored in bags before their export to Egerton University, Kenya for subsequent laboratory analysis and feeding trials. At Egerton University, the dried leaves were ground to pass through 4 and 1mm sieves for feeding trials and chemical analysis, respectively, (AOAC, 1990).

Figure 1. Map of Bor browse species collection site (Source: DIVA-GIS Website, 2017)

Study site

The experiment was conducted at sheep and goat section of Tatton Agricultural Park (TAP), Department of Animal Sciences; Egerton University in Njoro Campus during the month of April, 2016. The area lies at an altitude of 2238m above sea level, with an annual mean range temperature of 17 ^oC-22^oC and annual rainfall of 900-1200mm (EMS, 2009).

Experimental design, animals and housing

In a Completely Randomized Design, four crossbred (Small East African x Toggenburg) growing goats with initial mean body weight (16.6 ± 0.04kg) and 4-5 months of age were confined in separate individual pens of (1.5m x 2.5m) and used in the study. The goats were treated for internal and external parasites with Ivermectin and adapted to 2weeks. The adaptation phase was necessary for familiarizing goats to the tested browse species and confinement.

Feed, feeding and management

A Palatability study was conducted in a cafeteria feeding approach described by Larbi et al (1993a) using Grewia tenax, Tamarindus indica, Ziziphus spina-christi, Balanites aegyptiaca and Cordia sinensis. Chloris gayana hay was provided as basal diet.

Each pen was provided with a water container and a hanged wooden feed troughs at 30cm height designed in a way that each were partitioned into six compartments to accommodate each of the five tested browse species and hay. This was to ensure that each goat had free access to all of the five tested browse species. The 4 mm chopped browse species was offered at the rate of 200g each every day at 8:00am East African time with allowance of 30 minutes feeding time. The refusals were collected, weighed and intake determined by difference. Each day, the physical positioning of the tested browse species in the feed troughs were altered to eliminate possible biasness from goats' inborn preferences for one side. ChoppedChloris gayana hay, water and mineral supplement were offered ad libitum. The pens were cleaned and the previous day's residues of Chloris gayana hay removed before browse forage, hay or water was offered.

Data collection and measurements

Feeds offered and refused were weighed to determine the amount consumed every day. The intake data was used to determine the relative palatability of the browse species. Palatability was calculated for each browse species, separately for each goat as daily feed intake divided by that of the highest feed intake and expressed as percentage means as shown in the formulae below (Larbi et al, 1993b) and then ranked in each goat and separated out classes of high (>60%), medium (35-55%) and low palatability (<25%) (Lambart et al., 1989; Obour et al., 2015).

Chemical analysis

Samples of feeds offered and refused were collected every day, pooled for each goat and subsampled for proximate and fibre analysis. Dry matter, total nitrogen and ether extracts were determine according to AOAC (1990) methods. Crude protein (CP) was obtained by multiplying Nitrogen (N) in feeds by the factor (6.25). Neutral detergent fibre (NDF) and acid detergent fibre (ADF) were determined according to ANKOM²⁰⁰ Technology (2014). The extraction of phenolics was carried out by using 70% aqueous acetone and total extractable phenols (TEPH) determined using Folin Ciocalteu procedures as described by Julkunen- Titto (1985) and Evitayani et al (2004).

The concentration of TEPH was calculated using the regression equation of tannic acid standard. Condensed tannin (CT) was measured and calculated as leucocyanidin equivalent, following the method of Porter et al (1986).

Statistical analysis

The data was analysed by general linear model option of the ANOVA program in the SAS (2002) software (version 9.0); sources of variation was browses species and error.

Results

The proximate composition of the browse species and hay is presented in Table 1. There were considerable variation in browse proximate composition except DM. The CP, tannins (CT, PHE), and ether extract contents are presented in figure 2, 3 and 4, respectively in ascending order. Among the browse species, G. tenax had the highest CP while the lowest were recorded in T. indica. C. sinensis had the highest NDF and ADF contents while B. aegyptiaca and G. tenax had the lowest NDF and ADF contents, respectively. T. indica was observed to be the highest in condensed tannin and total extractable phenolics ((≥60g/kg).

Figure 2. Crude protein contents of the five South Sudan browse species in ascending order

Figure 3. Condensed tannin and total extractable phenolics contents of the five South Sudan browse species in ascending order

Figure 4. Ether extracts content of the five South Sudan browse species in ascending order

Daily intake, palatability and preference for browse forages

The mean daily DM intake (g), palatability (%) and preference of the five selected browse species are presented in Table 2. Palatability differences were manifested in the variation in DM intake. The order for palatability ranking is from the most palatable species to the least palatable based on DM daily intake and relative palatability index: G. tenax > Z. spina-christi > B. aegyptiaca > C. Sinensis > T. indica. In this study, G. tenax had the highest DM intake with T. indica having the least. Means were also grouped into high (>60%), medium (35%-55%) and low (<25%) preference classes. Preference for G. tenax and Z. spina-christi was the highest (>60%) while C. sinensis and T. indica recorded low preference (<25%). It was noted that those browse species with highest DM intake were most palatable and preferred by goats (figure 5). The CP contents observed justified browse forage use as feed supplement for it influenced feed intake and also improve the efficient utilization of poor quality hay. The concentration of CT ranged between (3-38 g/kg DM) is of nutritional benefits whereas as CT and PHE (>50g/kg DM) is detrimental for it reduce intake due to its astringent property. Other factors responsible for low intake could be smell, taste, texture and preference parameters like ether extract content. The senses (smell, taste, sight) enable goats to discriminate among feeds and provide pleasant or unpleasant feelings associated with feeding. Therefore increase or decrease from intake, palatability and preference could be as a result of the browse nutrient and toxin contents, the nutritional needs of the goat, and the goat's past experience with the feed.

Figure 5. Average daily DM intake (DMI) and relative palatability index (RPI) of the five South Sudan browse species in ascending order

Discussion

The CP contents of the most of species were consistent with values reported by (Welay et al 2011; Balehegn et al 2015 and Elseed et al 2015) for B. aegyptiaca and Z. spina-christi and for other species in the tropical region rangelands. NDF and ADF characteristic values were consistent to the values reported by (Singh and Oosting 1992; Bakshi 2007). The CT and PHE agreed with the values reported by (Welay et al 2011; Balehegn et al 2015 and Elseed et al 2015). G. tenax was the most preferred whereas T. indica was the least. The highest daily intake and relative palatability index observed in G. tenax was attributed to the highest CP which influenced intake of feeds (NRC 2000). The lowest intake of T. indica could be attributed to the highest condensed tannin and total extractable phenolics. This is consistent with findings of Barry et al (1984) and Waghorn (2008) who reported that high CT contents (>50 g/kg DM) reduced voluntary feed intake and palatability due to its astringent property. This is also in agreement with Obour et al (2015) who reported that Broussonetia papyrifera was the least palatable due to high CT (69.6g/kg-70.9g/kg DM). The low preference for T. indica and C. sinensis could be attributed to high ether extract and condensed tannin contents. In this study, preference parameters such as ether were the highest in C. sinensis and T. indica and this was in consistent with Obour et al (2015) who reported that Broussonetia papyrifera was the least preferred due to high condensed tannin and ether extract. These results, however, contradicted the finding of Hardison et al (1954) who reported that high ether extract to indicate high preference.

Conclusion

• G. tenax was the highest in DM intake, most palatable and preferred whereas T. indica was the least.
  
  
• This highlights browse species as supplemental feed with low quality basal diet.
  
  
• Though, T. indica was the least preferred, presence of variety of species may be important during periods of scarcity and severe feed shortages.

Acknowledgment

This material is based upon work supported by the United States Agency for International Development, as part of the feed the future initiative, under the CGIAR Fund, award number BFS-G-11-00002, and the predecessor fund the Food Security and Crisis Mitigation II grant, award number EEM-G-00-04-00013. The senior author is grateful to USAID for funding this work.

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Received 20 January 2017; Accepted 6 June 2017; Published 1 September 2017

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