Growth performance of Abergelle goats fed grass hay supplemented with pigeon pea (Cajanus cajun (L.) Millsp) leaves

Desta Tekle, Gebreslassie Gebru and Meseret Redae

Abergelle Agricultural Research Center, PO Box 44, Abyi Addi, Tigray, Ethiopia
destate14@gmail.com

Abstract

The experiment was conducted at Abergelle Agricultural Research Center farm in northern Ethiopia using 20 intact yearling male Abergelle goats with initial body weight of 15.47 + 2.01 kg. The objective of the study was to determine the feed intake, digestibility and growth performance of Abergelle goats fed 0, 150, 300 or 450 g/d of dried pigeon pea leaves as a supplement to native grass hay.

The goats lost live weight when fed native grass hay as the sole diet. Supplementing the hay with dried pigeon pea leaves to provide 50% of the diet DM, increased linearly the DM intake and the growth rate and improved the feed conversion. It is proposed that the growth rate response to increasing proportions of pigeon pea leaves in the diet reflected the role of the condensed tannin in the pigeon pea leaves in enhancing the rumen escape (bypass) of the protein, thereby increasing the protein and metabolizable energy (ME) status of the diets.

Key words: bypass protein, digestibility, feed conversion, tannin

Introduction

Communal natural pasture is the major feed source for goat in Tanqua Abergelle district of Tigray region, northern Ethiopia (Alemu 2015). Limited amount of crop residues and hay are offered to small ruminants during the dry season (Gebremariam and Belay 2016). According to Tolera et al (2000), supplementation with legume foliages creates an opportunity to minimize body weight losses during the dry season and to enhance productivity of goats in East Africa. Forage  legumes have the added advantage of improving soil fertility by fixing s appeanitrogen and thereby enhancing crop yield (Tolera et al 2000).

Pigeon pea (Cajanus cajun (L.) Millsp.) is an erect short lived perennial shrub and is among the best forage legumes adapted to arid and semi-arid environments (Mengistu 2008). According to Sheahan (2012), it makes an excellent, high-protein forage for livestock. Preferred method of feeding pigeon pea foliage is by cutting and feeding to livestock either fresh or conserved because damage to the branches may result when livestock browse the foliage (Sheahan 2012). Recently, pigeon pea varieties namely, ''Kibret'' and ''Tsgab”, which are suitable for lowland areas have been selected and released by Humera Agricultural Research Center in Ethiopia. In Tanqua Abergelle district, it is observed that there is a demand of such improved forage varieties by both extension workers and farmers.

A study by Belay et al (2016) revealed higher weight gain for grazing Abergelle sheep supplemented with dried pigeon pea leaves. However, there appears to be no information on the value of pigeon pea leaves in diets for goats.

Therefore, the objective of this study was to evaluate feed intake, digestibility and growth performance of Abergelle goats fed different levels of dried pigeon pea leaves as a supplement to native grass hay.

Materials and methods

Study area

The experiment was conducted at Abergelle Agricultural Research Center farm in Tanqua- Abergelle district of northern Ethiopia (13⁰ 14’06” N and 38⁰58’50” E). The climate is categorized as hot to warm, sub-moist with an altitude ranging from 1300 to 1800 masl. The annual mean rainfall is between 400 and 600 mm while the mean temperature is between 28 and 42 ⁰C (TAOARD 2015).

Goats and their management

A total of 20 intact yearling male Abergelle goats (15.5+ 2.01 kg) were purchased from the local market and housed in separate pens. They were treated against internal and external parasite with oral anthelmintic (Albendazole 7.5 mg/kg live weight) and Ivermectin (0.2 mg/kg live weight, by subcutaneous injection).

Experimental design and treatments

The goats were blocked into five groups according to their initial body weight and allocated in a randomized complete block design to four treatments and five replications. The treatments were dried pigeon pea leaves (PPL) at 0, 150, 300 g and 450 g/day as supplements to native grass hay fed free choice (around 20% refusal on DM basis) as their basal diet. Salt blocks and water were freely available.

Experimental diets

Native grass, dominantly of Cynodon dactylon, was harvested at approximately 50% flowering and sun dried before storage. Pigeon pea trees of a variety known as 'Kibret' were cultivated at Gerb Giba experimental site of Abergelle Agricultural Research Center. At 50% flowering, it was cut at 0.5 m height including the whole branches. Immediately after harvest, it was air dried under shade on a plastic sheet covered floor for ten days with adequate turning. The leaves were separated from the stems and branches by shaking and light beating, and stored in sacks until used for feeding.

Feeding trial

The feeding trial was over 90 days following 15 days of adaptation. Feed offered and refused were recorded daily throughout the experimental period. DM intake was determined as the difference between amounts of feed offered and refused on DM basis. Each goat was weighed fortnightly in the morning after overnight fasting using spring balance of 50 kg capacity and 200 g precision.

Digestibility trial

Digestibility coefficients were measured at the end of the feeding trial for 7 consecutive days after 3 days of adaptation for the goats to adapt to the fecal bags. Daily fecal excretion of each goat was mixed and 10% kept in airtight plastic bags and stored at -20 ^oC. Finally, fecal samples were pooled for each goat and a 20% sub-sample taken to determine chemical composition.

Laboratory analysis

Samples of feeds offered and refused were analyzed for DM, ash and N using the procedures outlined by AOAC (2005). Neutral detergent fiber (NDF), acid detergent fiber (ADF) and acid detergent lignin (ADL) were analyzed according to Van Soest et al (1991).

Data analysis

Data were subjected to analysis of variance using the general linear model procedure of SAS version 9.2 (SAS 2008). Treatment means were compared using Tukey studentized range (HSD) test. The statistical model was:

Y_{ij =} u + t_{i +} b_{j +}ε_ij

Where: Y_ij= response variable; u= overall mean; ti= treatment effect i; b_j= block effect j and εij= random error.

Results and discussion

The low crude protein of the native grass hay (Table 1) explains:  the loss of live weight when hay was fed as the sole diet; and the response in DM intake (Figure 1), in growth rate (Figure 2) and in feed conversion when supplemented with dried pigeon pea leaves (Table 2). The improvement in digestibility coefficients likewise reflected the improved status of the diet with pigeon pea leaf supplementation.

Figure 1. DM intake of Abergelle goats increased linearly as pigeon pea leaves replaced the basal diet of native grass hay	Figure 2. Live weight gain of Abergelle goats increased linearly as pigeon pea leaves replaced the basal diet of native grass hay

The linear response in growth rate of the goats with increasing proportions of pigeon pea leaves in the diet indicates that the leaves from this tree are good sources of rumen escape (bypass) protein. This is probably the result of their moderate levels of condensed tannin that are reported to be in the range of 1.4 to 2.8% in the DM (Alexander et al 2007), levels considered to favor their effect in reducing the solubility of the leaf protein and thus promoting its rumen bypass characteristics (Barry and McNabb 1999).

Preston and Leng (1987) hypothesized that bypass protein has the dual effect of increasing both the protein and metabolizable energy (ME) status of ruminant diets. In the present experiment, the increase in ME status as a result of PPL supplementation was probably the result of the 100% linear increase in the DM intake rather than the response in digestibility which was not linear and was improved by only 18%.

Conclusion

• Goats lost live weight when fed native grass hay as the sole diet
  
  
• Supplementing the hay with dried pigeon pea leaves to provide 50% of the diet DM, increased linearly the DM intake and the growth rate and improved the feed conversion.
  
  
• It is proposed that the growth rate response to increasing proportions of pigeon pea leaves in the diet reflected the role of the condensed tannins in the pigeon pea leaves in enhancing the rumen escape (bypass) of the protein, thereby increasing the protein and metabolizable energy (ME) status of the diets.

Acknowledgements

The authors thank the Tigray Agricultural Research Institution (TARI) for funding this research.

References

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Received 20 May 2018; Accepted 20 July 2018; Published 1 August 2018

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