In vivo digestibility and performance of growing goats fed maize stover supplemented with browse leaf meals and cotton seed cake based concentrates

E E Ndemanisho* B N Kimoro, E J Mtengeti* and V R M Muhikambele*

Department of Livestock Production, Ministry of Agriculture and Rural Development, P.O. Box 34188, Nairobi, Kenya.
*Department of Animal Science and Production,Sokoine University of Agriculture, P.O. Box 3004, Morogoro. Tanzania
ndema@suanet.ac.tz

Abstract

Rumen degradability, in vivo digestibility and intake studies were undertaken to evaluate the potential of Leucaena leucocephala, Albizia lebbeck, Moringa oleifera and Gliricidia sepium leaf meals compared with cotton seed cake as protein sources for goats. In a rumen dry matter (DM) and crude protein (CP) degradability study, hominy meal (HM), maize stover (MS), and isonitrogenous concentrates (220g CP/kg DM) based on Leucaena (LBC), Albizia (ABC), Moringa (MBC), Gliricidia (GBC) or cotton seed cake (CSC) were used in nylon bags, were inserted into the rumens of 4 fistulated heifers and removed after 2 to 96 hours. In an in vivo digestibility study, 20 goats were fed ad libitum maize stover, supplemented with either of the LBC, ABC, MBC, GBC or CSC concentrates.

There were differences (P<0.05) in DM and CP degradability constants, both between energy feedstuffs (MS and HM) and between protein feedstuffs (leaf meals and CSC). The digestibility study showed differences in DM, organic matter (OM), CP, acid detergent fibre (ADF) and neutral detergent fibre (NDF) intake between treatments (P<0.05), but the corresponding in vivo digestibility coefficients were similar across treatments (P>0.05), except for CP. Total intake varied from 302 ± 4.5 in ABC to 316 ± 0.7 g per day in CSC.

Average growth rate for the goats across treatments was 26.5 ± 2.9 g/d and did not differ among treatments (P>0.05). These weights were rather lower than expected for crossbred dairy goats. This could be attributed to the short period involved in trial, that is not being long enough to allow for tangible growth rate but also due to the maize stover used as basal diet being of too low quality. However, the study suggests that the browses used could replace cotton seed cake as supplement for protein.

Keywords: browse leaf meals, cotton seed cake, growing goats, In vivo digestibility, maize stover

Introduction

Forage trees and shrubs are an integral part of farming system and generally, have multiple uses in all less-developed countries in the tropics (Preston 1995, Khamseekhiew et al 2001). Leucaena leucocephala, Gliricidia sepium, Albizia lebbeckand Moringa oleifera are browse shrubs widely available and fed to animals by farmers in the tropics. Their use as supplements has been shown to enhance intake of poor quality roughages, improve growth rates and increase reproduction efficiency in ruminants (Karachi and Zengo 1997; Alayon et al 1998; Orden et al 2000). The high dry matter degradability values of the leaf meals make them appropriate as supplements with basal diets of poor quality. The high dry matter degradability implies high fermentation and passage rates, thus allowing higher feed intakes by animals. In addition, this feature also facilitates faster release of nutrients to the microbial population in the rumen thus optimising microbial synthesis. In spite of the apparently high dry matter values of these browse plants, there is evidence (Kamatali et al 1992; Azim et al 2002) that animal response is not always predictable and there are differences in their nutritive values. Further, comparison of these browse plants species has not been undertaken effectively with goats. The purpose of this study was therefore to assess the degradability and in vivo digestibility of concentrates based on leaf meals of Leucaena leucocephala, Gliricidia sepium, Albizialebbeck and Moringa oleifera compared to cotton seed cake (CSC) in growing goats.

Materials and methods

Degradability study

Animals and their management

Maize stover, which formed a basal diet, was collected from the University farms in early August 2001 and chopped into 2 - 4 cm lengths using a tractor driven forage chopper. The stover were then stored in a dry concrete pit during the entire period of the experiment. The basal diet was supplemented with concentrates based on Albizia lebbeck (ABC), Gliricidia sepium (GBC), Leucaena leucocephala (LBC), Moringa oleifera (MBC) and cotton seed cake (CSC) as shown in Table 1. The shrubs were harvested at flowering stages around the University farm. They were each dried under the sun for two days while hand turning (twelve times per day) to avoid scorching. The dried leaves were preserved in dried sacks and stored ready for feeding. Cotton seed cake, hominy meal, mineral mixture, salt and vitamins were purchased from various milling enterprises and agro-shops in Morogoro town. All the diets were formulated to be iso-nitrogenous and contained on average 220 g crude protein (CP) per kg dry matter (DM). This was achieved by using different proportions of browse and cotton seed cake. Degradability was estimated by the nylon bag technique, as described by Ørskov (2000). Four heifers with permanent rumen fistulas were used in the study. Prior to commencement of the study, the animals were subjected to a preliminary period of 10 days. The ration during this period, consisting of cut grass (Briacharia/Panicum grass mixture), supplemented with 2.0 kg of a concentrate mixture, consisting of all the four leaf meals, CSC, hominy meal and mineral supplements. Daily feed intakes were recorded and corresponded to roughage to concentrate ratio of 70:30 and this feeding regime was maintained until the removal of the last nylon bags from the rumens.

The energy (ME) of the feedstuffs was calculated according to the following formulae:

OMD = 0.98 DMD - 4.8 (MAFF 1975),

Where OMD = organic matter digestibility and DMD 48 - hour degradability. .

The energy was then estimated as follows:

ME (MJ/kg DM) = 0.15 or 0.16 OMD (Beever and Mould 2000).

The effective degradability was calculated, using a fractional passage rate of 0.04 h ^{- 1} , according to Mgheni et al (2001)

Sample preparation and data collection

All samples were air-dried and ground to pass a 2.5-mm screen of a Christy and Norris hammer mill. The nylon bags used were approximately 7.5 x 10 cm in size with a pore size of about 40 to 50 µm and were filled with approximately 1 g of the respective samples. Rumen incubation times were 0, 2, 4, 8, 16, 24, 48 and 96 h. After removal, the bags were subsequently placed into plastic bags and stored in a deep freezer at a temperature of between -15 ⁰C and -20 ⁰ C to prevent further microbial activity.

After removal from the deep freezer, all bags were thawed, placed into a washing machine and washed for 30 minutes. For the 0 - hour washing loss determination, duplicates of the samples, without incubation in the rumen, were similarly washed in a washing machine for 30 minutes.

In vivo digestibility study

Animals and their management

In vivo digestibility of DM, OM, N, NDF (neutral detergent fibre) and ADF (acid detergent fibre) determination were carried out on 20 cross-bred (local Tanzania x Norwegian Landrace,) male goats aged 6 to 7 months (originating from the intake study). This experiment was conducted three weeks after the feed intake experiment (See intake data in Table 4) where 40 growing goats (20 males and 20 females) had been used. Amounts of feed offered and refusals were recorded daily and samples were taken for subsequent analyses.

Feeding and feed allowance

Maize stover was provided on ad libitum basis (that is to allow for about 10 - 25% refusal) throughout the experimental period. The refusals from the previous day's offer were collected from each animal, weighed, recorded, sub sampled and finally bulked for chemical analysis at the end of the study (Table 1). The supplementary feeds were split into two portions and fed in the morning (0900 h) and afternoon (1400 h). The basal diet was given in the morning (0900 h) after removal of the previous day's refusals. All animals had free access to both water and minerals (mineral blocks) during the entire experiment. The total duration of the study was 17 days (10 days adjustment period and 7 days collection period).

Refusals and faeces collection

During the collection period, samples from the maize stover offered and refusals from each goat were collected, weighed, recorded and bulked. At the end of the study, the bulked refusals from individual animal were thoroughly mixed, re-sampled, oven dried (60^o C for 48 h), ground through a 1-mm sieve and then analysed.

The faeces were thoroughly mixed, weighed and dried to constant weight at 103 - 105 C in a Unitherm forced draught oven for chemical analysis.

In vitro digestibility

Dry matter digestibility and OMD of feed samples offered to experimental animals were determined in vitro using the acid pepsin two-stage method (Tilley and Terry 1963).

Laboratory analyses

Dried samples were milled through a 1 mm screen before being analysed. Feeds and faeces were analysed for DM, OM, N and ash in accordance with AOAC (1990). The ADF, ADL and NDF values were analysed according to Van Soest et al (1991). Wet faeces and urine were analysed for N using the Kjedahl method (AOAC 1990).

Biometrical analyses

The disappearance of DM from the nylon bags was described by the model of Ørskov and McDonald (1979):

P = a + b (1- e^-ct)

Where:

P = percentage degradability at time t.

a = Soluble fraction assumed to disappear from the bag instantly (g/kg)

b = Insoluble but rumen potentially degradable material at time t (g/kg)

c = Rate constant at which b is degraded (1/h).

t = Length of incubation (h).

Effective rumen degradability (EPD) was then calculated using the equation:

EPD = a + bc/(c + k) (Ørskov and McDonald 1979)

where EPD were used to describe the digestion kinetics and to calculate the effective rumen degradability and k = passage rate constant (0.04 h ^{- 1} ).

The 48-hour values were analysed using the General Linear Model (GLM) procedures of the Statistical Analysis System (SAS 1998) using the model:

Y_ij = μ + T_i + e_ij

where

Y_ij = Record of the j^th value belonging to the i^th sample

μ = Overall mean

T_i = Effect of the ith incubation period

e_ij = Error term

A similar model was used to analyse the in vivo digestibility data.

The least square means (LS Means) were computed and tested for significance.
 

Results

Chemical composition of feedstuffs and supplements

The composition of protein supplements and feed ingredients used in the study are shown in Tables 1 and 2.

Maize stover had higher NDF and ADF values and hominy meal had a higher hemicellulose value compared to the other feedstuffs. However, their CP levels were lower compared to values of leaf meals and CSC. Among the leaf meals AL had the highest NDF value and MO the highest CP level. The chemical compositions of the treatment rations were as shown in Table 3.

The supplements were isonitrogenous. However, ABC and CSC had a slightly higher OM values compared to the rest of the concentrates. The ADL of ABC was highest among the concentrates used in the study.

Intake

Intake results are presented in Table 4. The leaf meal supplemented diets had similar trend of intake to maize stover. Goats on LBC had slightly lower DM intakes of maize stover compared to those on other treatments. There were hardly any leftovers in the feed troughs from the supplements.

Growth performance

The results on growth performance are presented in Table 5. There were generally small differences in growth rates between treatments. Goats fed CSC had higher mean gains compared to the other treatments (P<0.05) except GBC.