Influence of browse-tree leaves supplementation on digestibility, rumen fermentation and performance of goats fed mixed grass hay

M I Okoruwa and I Ikhimioya

Department of Animal Science, Ambrose Alli University, P.M.B. 14, Ekpoma, Edo State, Nigeria
odionokos@yahoo.com

Abstract

The study was carried out to assess the effect of supplementation of mixed grass hay with browse-tree leaves on rumen fermentation, digestibly, N retention and growth and feed conversion of goats. Twenty four goats with initial body weight of 8.00 ± 0.41kg were housed individually and assigned to four treatment diets of mixed grass hay or hay (70%) supplemented with leaves (30%) of Paraserianthes falcataria, Moringa oliefera or Calliandra calothyrsus.

Apparent digestibility of DM, crude protein and crude fiber, and N retention were increased by browse-leaf supplementation. There were decreased population of rumen protozoa and increased  rumen propionate when the grass hay was supplemented with leaves from the browse trees. These changes were reflected in higher feed intake and better growth and feed conversion as the basal diet of grass hay was supplemented with the leaves from the browse trees.

Keywords: Calliandra, growth, Moringa, nutrient retention, Paraserianthes, propionate, protozoa

Introduction

The sustainability of ruminant livestock production in the tropics is faced with the problem of inadequate supply of year-round feeds. This nutritional constraint is probably the most pressing factor contributing to the low supply of animal protein to the human populace in Nigeria. The dry season is the most challenging limitation, characterized by insufficient feed of poor quality (Babayemi2007). Grasses in tropical regions are low in nitrogen and high in fibre especially during the dry season. This negative effect of nutritional status results in low performance in goats (Okoruwa 2019). It has been recognised that intake and efficient utilisation of fibrous feeds are influenced by the rate of rumen fermentation (Nouala et al 2006) and the balance of nutrients absorbed in the intestine. Improvement in the nutritive value, removal of nutritional limitations by rumen fermentation and balance supply of nutrients to host animals will result in improvement of goat productivity.

One of the feasible options to this feed shortage is the supplementation with concentrate mixtures that has resulted in increased feed intake in more intensive production systems as reviewed by Nouala et al (2006). However, these supplements are often not fed due to their unavailability and high cost of ingredients.

The global interest in multi-purpose trees as forage and feed supplement for ruminants has increased research on their nutritive value. Trees offer advantages over grasses in terms of higher dry matter yields and capacity to retain high-quality foliage under stress condition (Theng Kouch et al 2003). This may offer considerable potential for use in ruminant livestock production systems in Nigeria to alleviate and complement their low feed value of native pasture (Okoruwa 2019).Thus, research trends have been directed towards investigating alternative plant protein sources available in the rural communities to replace conventional feed sources that are associated with high cost and competitive demand as food for humans.

Browse trees such as Paraserianthes falcataria, Moringa oleifera and Calliandra calothyrsus can be an option to sustain better performance in goats without the use of expensive concentrate diets. It was reported by Norton (2003) that browse-tree leaves have high quality nutrients as well as medicinal attributes for feeding ruminants that make them potential replacements for conventional protein sources in goat production (Norton 1994).Therefore, the use of browse-tree leaves to supplement poor quality grasses can be one of the most productive and sustainable practices for increasing goat production in Nigeria. Hence, this study was planned to assess the effect of browse-tree eaf supplementation on digestibility, nutrient retention, rumen fermentation and performance of goats fed mixed grass hay.

Materials and methods

The study was carried out at the Ruminant livestock Unit of the Teaching and Research Farm of Ambrose Alli University, Ekpoma, Nigeria.

Experimental diets

Mature fresh leaves of Paraserianthes falcataria (PL), Moringa oleifera (MO) and Calliandra calothyrsus (CC) were obtained daily from trees from around Ekpoma. The leaves were dried under shade for 5 days before use. Equal proportions of guinea grass and elephant grass were obtained within the farm. They were chopped, mixed together and air-dried under shade to 80-85% dry matter. Thereafter, they were stored in bags and kept in a dry area. The mixed grass hay was used as the sole diet for the control group, while combinations of the mixed grass hay and each of the three browse-tree leaves in a ratio of 70:30 (DM basis) were  used in the other dietary treatment groups.

The four experimental diets were; MGHS (100% mixed grass hay), MGPF (70% mixed grass hay with 30% leaves of Paraserianthes falcataria), MGMO (70% mixed grass hay with 30% leaves of Moringa oliefera) and MGCC (70% mixed grass hay with 30% leaves of Calliandra calothyrsus).

Animals, design and management

Twenty-four West African dwarf male goats aged 8 to 9 months with initial average weight of 8.00 ± 0.41kg were housed in pens (two goats per pen). The feeding trial was arranged as a completely randomized design with four treatments each with 3 replicates (2 goats per pen per replicate). The goats were offered the diets twice daily at 8:00am and 4:00pm. The quantity of the diet offered to each goat was given at a rate of 5% dry matter basis of their body weight.The percentage ratio of the test leaves to the basal diet of mixed grass hay was used to determine the proportion of each plant leaf in the daily feed allowance offered to each goat. The quantity of feed provided was adjusted after every week according to live body weight change. The goats also had free access to water throughout the experimental period. The trial was conducted for 84 days exclusive of a 14-day adaptation period.

Data collection

Daily feed offered was recorded and leftovers were collected in the morning of the next day to estimate voluntary feed intake.

Goats were weighed at the commencement of the trial (after the adaption period) and subsequently at weekly intervals.

At the end of the feeding trial, the goats were transferred into individual metabolic cages for collection of feces and urine. Records of daily feed offered, feed refusals, fecal and urinary outputs were kept for 7 days after 7 days of physiological adjustment to the cages. At the end of the study, fecal samples for each goat were bulked, mixed and about 10% of sub-sample was pooled and kept in plastic bags in the freezer (-20°C) for analysis. Urine sub-samples were collected in plastic bottles with 4 drops of diluted sulphur acid (10% H₂SO₄) to prevent loss of ammonia. Apparent digestibility and nitrogen retention were calculated based on DM consumed, feces and urine voided.

Rumen liquor samples were collected four hours post feeding using a stomach tube inserted to a depth of 110 –130cm through the oesophagus. The first portion (about 30ml) of the sample collected was discarded to reduce saliva contamination. The rumen pH was determined immediately using a digital pH meter. A fraction of the rumen liquor sample was stored in10% formal-saline prior to the direct microscopic counts of the rumen protozoa. The other fraction of rumen fluid was bulked for each animal and made free of coarse particles by straining through layers of cheese cloth. Thereafter, part of the filtrate was acidified with 1ml of a 5% (v/v) orthophosphoric acid solution and stored frozen in the air tight plastic container to measure total volatile fatty acid (VFA) concentration. Separate 10ml sub-samples were treated with 2ml of 25% meta-phosphoric acid and centrifuged at 584rpm for 15min for subsequent measurement of individual volatile fatty acids.

Chemical analysis

Samples of leaves, feeds and feces were analyzed following the procedures of AOAC (1990). Rumen VFA fractions were measured according to the procedures described by Mor et al (2019).

Statistical analysis

Data were subjected to descriptive statistics and analysis of variance (ANOVA) using the general linear model procedure of SAS (2000). Where significant treatment effects were found, means were separated by Duncan’s multiple range test (Steel and Torrie 1990). The linear model used for the analysis was as follows

Yij = U + Ai +eijk

Where;

Yijk = independent variable (intake, digestibility.......)

U = overall mean of the observed variable

Ai = effect due to i^th treatment diets

eij = effect of random residual error

Results

Apparent digestibility of DM, crude protein and crude fiber, and N retention were increased when the basal diet of grass hay was supplemented with the leaves from the browse trees (Tables 1 and 2).

The increases in diet digestibilityand N retention were reflected in increased feed intake and growth rate and better feed conversion (Table 3).

The most important benefits from browse-leaf supplementation of the grass hay were the decrease in protozoal counts and the increases in rumen propionate (Table 4).

Figure 1. Anti-nutritional compounds (TT Total tannin, CT Condensed tannin, Sap Saponins, Phy Phytates) in the three browse-tree leaves	Figure 2. Relationship between rumen protozoa and molar propionate in rumen fluid of goats fed browse-tree leaves as supplement to grass hay
Figure 3. Relationship between rumen propionate concentration and live weight gain	Figure 4. Relationship between rumen propionate concentration and feed conversion

Discussion

The potential benefits in growth and feed conversion conferred on a diet of grass-hay by supplementation with browse-tree leaves (Table 3) are various. The leaves provide a source of nitrogen for growth of rumen bacteria that provide protein to the ruminant animal as well as enhancing diet digestibility (Table 2). Tannins in the tree leaves (Table 1) react with the protein in the tree leaves, protecting them from microbial attack, thus facilitating the rumen escape of some of the protein for more efficient enzymic digestion in the intestines (Barry and McNabb 1999). The tannins per seare toxic to rumen protozoa thus they indirectly create more space and nutrients for growth of bacteria (Li 2019). More importantly they reduce production of methane through direct inhibition of of methanogenic bacteria, which facilitates positive changes in the rumen fermentation as the hydrogen not taken up by methanogenic bacteria results in increased production of propionic acid, which is the major precursor of glucose for more improved growth and feed conversion (Preston and Leng 1987) as seen in the data in Figures 3 and 4.

Conclusions

• Apparent digestibility of DM, crude protein and crude fiber, and N retention in growing goats were increased when a basal diet of grass hay was supplemented with leaves from Paraserianthes falcataria, Moringa oleifera or Calliandra calothyrsus.
  
  
• There were decreases in protozoa counts and increases in rumen propionate in the goats fed the browse tree leaves. These changes were reflected in higher feed intake and better growth and feed conversion as the basal diet of grass hay was supplemented with the leaves from the browse trees.

References

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Received 16 April 2020; Accepted 28 April 2020; Published 1 June 2020

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