Effect of dietary supplementation of leaves as source of condensed tannins on the performance of lambs

A Dey^*, Narayan Dutta, K Sharma* and A K Pattanaik

Centre of Advanced Studies in Animal Nutrition, Indian Veterinary Research Institute, Izatnagar- 243 122, India
^*Present address: Malda Krishi Vigyan Kendra, Uttar Banga Krishi Viswavidyalaya, Mathurapur, Manikchak, Malda- 732 203, India
directorcasan@ivri.up.nic.in

Abstract

This study investigated the effects of dietary supplementation of Ficus infectoria on the performance of lambs. Twenty four non-descript lambs were randomly divided into four groups of six each in a completely randomized block design to receive either a conventional supplement (CT-0) or experimental supplements CT-1.0, CT-1.5 and CT-2.0 containing 1.0, 1.5 and 2.0% condensed tannins (CT), respectively by replacement of wheat bran of supplement CT-0 with ground tree leaves of Ficus infectoria to meet their requirements for maintenance and growth.

The supplementation of CT up to 1.5 per cent in the supplement did not interfere with the nutrient intake or digestibility, however, a depressing effect on dry matter (DM), organic matter (OM) and acid detergent fibre (ADF) digestibility at 2.0 per cent CT level was apparent without any detrimental affect on intake. Feeding of CT containing diets particularly at 1.5 and 2.0 per cent levels significantly (p<0.05) influenced N utilization and improved its retention. Digestible crude protein (DCP) and total digestible (TDN) values of the composite diets were comparable, except for significantly (p<0.05) lower TDN (%) in CT-2.0 than the control. Intake of DCP and TDN was comparable irrespective of dietary treatments, except for significantly (p<0.05) lower intake of lambs under CT-2.0 as compared to CT-1.0. The average daily growth rate and wool growth for a period of 180 d showed a significant (p<0.05) increase by the supplementation of CT at 1.5 per cent through Ficus infectoria leaves.

It may be concluded that condensed tannins from Ficus infectoria leaves at 1.5% level in the supplement could be used for improving the performance of lambs.

Key words: condensed tannins, Ficus infectoria, growth, lambs, proteins, wool

Introduction

Extensive protein degradation in the rumen often results in wastage of dietary proteins, particularly in productive ruminants such as growing animals, which have high protein requirements. Protection of proteins is essential for productive animals, where the protein requirement of these animals cannot be met from a sole microbial source. There has been considerable interest in reducing ruminal degradation of proteins. Studies have indicated that feeding proteins, which are resistant to microbial breakdown in the rumen but available in the post rumen, significantly increased growth rate and production of milk and milk protein (Terrill et al 1992; Wright et al 1998).

Various treatments have been used to protect proteins from rumen degradation and thereby to provide by-pass protein to the lower tract. However, these treatments may impair the subsequent availability of some amino acids, notably lysine, cysteine, tyrosine and leucine (Ashes et al 1984; Schonhusen et al 1986). Moreover, an increasing number of consumers demanding healthy and natural foods have pushed organic livestock farming that are reputed to be environment friendly, sustaining animals in good health, with high welfare standards and prohibit routine use of growth promoters, animals’ offals or any other chemicals and additives to livestock rations. Thus, the use of formaldehyde and other chemicals to protect proteins from ruminal degradation has no scope in organic animal farming (IFOAM 2006). It is therefore imperative to explore alternative organic protectants of protein to improve protein utilization and make animals more productive. In this context, there is a growing interest in the possible use of CT as organic protectant of protein in the ration of animals.

CT (Proanthocyanidins) form complexes with proteins that are stable over the pH range of 3.5-7.0, but dissociate in the abomasum and anterior duodenum. This protects proteins from microbial hydrolysis and deamination in the rumen and increases the availability of feed proteins for digestion and post-rumen absorption (Makkar 2003; Min et al 2003).

Ficus infectoria is an evergreen tree hugely growing in Northern parts of India. They are generally planted for shade and not used as fodder tree due to high tannin content. A standard size Ficus infectoria tree can provide about 5-6 quintals fresh leaves from one lopping. Preliminary study with graded levels of CT in the substrate (1-2%) through Ficus infectoria leaves indicated significant reduction on in vitro nitrogen degradability of groundnut cake (Dey et al 2006).  Keeping this background in view, the present investigation was under taken to study the effect of graded levels of CT from Ficus infectoria on growth and wool production in growing lambs.
 

Materials and methods

Animals and feeds

Twenty-four 6-month-old non-descript lambs (11.73 ± 0.22 kg), were allocated to four dietary treatments in a completely randomized block design at the onset of the experiment. The lambs were penned individually with free access to fresh water in ventilated sheds and allowed exercise out-doors in an adjacent dry paddock daily. Four iso-nitogenous supplements CT-0, CT-1.0, CT-1.5 and CT-2.0 were formulated containing 0, 1.0, 1.5 and 2.0% CT, respectively in the supplements and fed to the lambs with a basal diet of wheat straw to meet their requirements for maintenance and growth (50 g per day) as recommended by Kearl (1982). Ficus infectoria leaves were harvested in one lot in the month of July from the IVRI campus. The leaves were dried and ground in an electric grinder before mixing in the supplements. Dried and ground Ficus infectoria leaves were incorporated in different proportion to the supplements by replacing of wheat bran to bring CT content to 0, 1.0, 1.5 and 2.0 per cent of supplements on dry matter basis. The ingredients and chemical composition of the supplements and wheat straw are given in Table 1.

The amount of supplements was adjusted fortnightly as per the body weight changes of each animal to meet their CP requirement for maintenance and growth (50 g per day). 

Experimental procedures

Each group of six lambs was randomly allocated to one of the four supplements (Table 1). The daily allowance of the supplements was offered in single meals (at 09.30h) in the morning and wheat straw was then offered ad libitum, when all the lambs had consumed the concentrate. A small quantity of green fodder (about 100 g oats/ maize) was also offered to take care of vitamin A requirement of lambs.   Left straw residues were weighed 24h post-feeding to ascertain daily feed consumption. The feeding trial was carried out for 201 days duration including the first 21 days for adaptation and subsequent 180 days for measurement. Daily DM intake and fortnightly BW of all the lambs were recorded before feeding in the morning throughout the study.

A digestion and N balance trial were conducted after 90 days of experimental feeding. The trial lasted for 9-days with a 3-days adaptation period to accustom the lambs to cages prior to 6-day collection and measurement period. Samples of feed offered and refused were collected daily. Total daily (24h) faecal and urine outputs  were recorded and a  sub sample of the  faeces (20%) collected and dried at 80± 2°C for 24 h in a forced-draft oven for dry matter estimation. Pooled samples were ground and stored for chemical analysis. Representative samples of each daily faecal and urine collection were pooled for 6 days and preserved in diluted (1:4) sulfuric acid for N estimation.

Shearing was done by hand scissors at the on set and completion (180 d) of experiment. The total wool yield was weighed for each lamb and average daily wool yield was calculated. Staple length was measured by metric scale and fibre diameter by lanometer. An average of 10 wool fibre taken at random was used as the representative measurement.

Chemical and statistical analyses

Samples of feeds, residues and faeces were milled to pass through a 1 mm sieve and analyzed for their proximate constituents (AOAC 1995). The fibre fractions, neutral detergent fibre (NDF) and acid detergent fibre (ADF) were estimated according to the methods of Van Soest et al (1991). The CT content of Ficus infectoria leaves was estimated by Butanol-HCl method (Makkar 2000). The results obtained were subjected to analysis of variance and treatment means were ranked using Duncan’s multiple range test (Snedecor and Cochran 1994).
 

Results and discussion

Chemical composition of feeds

The chemical composition of supplements and wheat straw is given in Table 1. The chemical composition of wheat straw offered as basal feed was within the normal range and comparable to values reported for Indian feeds and fodder (Narayan Dutta and Sharma 2004; Sharma et al 2004).    Ficus infectoria leaves containing 9.4% CT were used as a protectant of dietary protein in the ration. The experimental supplements were isonitrogenous and isocaloric. The concentration of NDF and ADF was higher in CT containing supplements than in conventional supplements, which could be attributed to the high cell-wall constituents usually present in leaf meal (Anbarasu et al 2004). 

Intake and nutrient utilization

Total DM intake (g/kg W^0.75) during metabolism trial was comparable among dietary treatments. Similarly, intake of wheat straw and concentrate moiety was also comparable among the dietary treatments (Table 2).