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).

The comparable intake by lambs irrespective of dietary treatments are in agreement with the earlier observations (Wang et al 1996; Komolong et al 2001)  that moderate levels (1-4%) of CT in the diet from various plant sources exerted no significant effect on feed intake. Digestibility coefficient of DM and OM were comparable among CT containing diets, however, digestibility of DM, OM and ADF in lambs fed diet CT-2.0 was significantly (p<0.05) lower relative to control. Digestibility of CP and NDF were comparable among the dietary treatments (Table 2). The nutritional effects of tannins are associated with their ability to bind with proteins (dietary and enzymes), structural carbohydrate polymers found in plant cell walls and minerals with an overall effect of lowering the bioavailability of nutrients at specific sites in the gastro-intestinal tract (Ndluvo 2000). In the present study the addition of CT upto 1.5% of supplement does not seem to interfere with the microbial activity or total tract digestibility of nutrients, however, a depressing effect on DM digestibility at CT-2.0 level was apparent without detrimentally affecting dietary intake. This may probably be due to interference of CT with microbial attachment or depressing cellulolytic bacterial population (McSweeney et al 1998).

The nutrient density in terms of DCP and TDN of the composite diets were comparable, except for significantly (p<0.05) lower TDN (%) in treatment CT-2.0 than the control. Intake of DCP and TDN (g/kg W^0.75) was comparable irrespective of dietary treatments, except for significantly (p<0.05) lower intake of lambs under CT-2.0 as compared to others given diet CT-1.0 (Table 2).

The absence of any detectable adverse effect on the health of experimental animals suggests that lambs were on balanced diets with no apparent deleterious consequences. Except for DCP, all the animals had enough nutrient intake of TDN irrespective of dietary treatments to meet the requirements for maintenance and growth (50 g/d). The findings suggest that plane of nutrition was not affected adversely with CT supplementation in conformity with the earlier reports (Terrill et al 1992; Waghorn et al 1994) indicating no adverse effect of dietary inclusion of CT below 5% level on nutrient intake and utilization.

Daily intake (g/d) of N was comparable among irrespective of dietary treatments, except CT-1.5 which had significantly higher N intake (Table 3).

All the lambs had positive N balance indicating adequate nutritional level of all the lambs, irrespective of dietary treatments. However, N-retention was significantly (p<0.05) higher   at CT-1.5 and CT-2.0 levels as compared to control. Another feature of N utilization as evident by significantly higher N retention as percentage of absorbed N (an indicator of availability of amino acid-N at tissue level) in animals given CT protected concentrate was apparently due to better amino acid availability and apparent biological value of CT protected diets (Barry and McNabb 1999).

Voluntary feed intake, growth and feed conversion ratio

The overall DMI (g/ day) by lambs was significantly (p<0.05) higher for CT-1.5 followed by CT-1.0 and comparable values were recorded for treatment CT-0 and CT-2.0.  The fortnightly body weight changes are depicted in Figure 1.

The initial live weight  was comparable irrespective of dietary treatments, however, lambs fed CT-1.5 recorded significantly higher (p<0.05) average final body weight (kg) relative to their counterparts given diet CT-0 and CT-2.0, although body weight of animals under CT-1.0 was comparable to other treatments. Similarly, the total body weight gain (kg) for the period of 180 days and average daily gain (ADG, g) for lambs under the treatment CT-1.5 was significantly (p<0.05) higher as compared to their counterparts kept on other dietary treatments. Feed conversion ratio (FCR) (kg DMI/ kg gain) was comparable irrespective of dietary treatment except for significantly (p<0.05) lower FCR in lambs given CT-1.5 as compared to CT-2.0 (Table 4).

The positive response of ADG and FCR to 1.5% level of CT in the supplement gives an indication that the binding effect of tannins was pronounced only at this level by supplying protein to the lower gut and subsequently its more efficient use for tissue growth (Ngwa et al 2002). Based on current market rate, per kg cost of formulated supplements CT-0, CT-1.0, CT-1.5 and CT-2.0 worked out to be Rs. 6.8, 6.3, 6.1 and 5.8, respectively. The cost of per kg body gain was reduced in CT containing supplements fed groups as compared to control (CT-0). Cost of per kg body gain was comparable between CT-1.0 and CT-2.0 treatments; however, it was lowest in CT-1.5 group. The body weight gain was Rs 8.0 (1.0 US dollar = Rs 45.0) cheaper (Rs 34 Vs 42) in CT-1.5 as compared to control. 

Wool yield and quality

The total wool yield (g) and yield per day (g) were significantly (p<0.05) higher for the treatment CT-1.5 as compared to similar wool yield by lambs in CT-0 and CT-2.0 treatments. However, no significant difference was recorded in wool yield of animals either fed CT-1.0 or CT-1.5 diets (Table 4). The increase in fleece weight in the present experiment at 1-1.5% CT level could be due to CT increasing the absorption of SAA and also that of all other EAA (Min et al 2001). The wool quality in term of fibre length (mm) and fibre diameter (mm) was similar (p<0.05) in lambs supplement containing treatments.
 

Conclusions

· Ficus infectoria leaves could be used as a potential source of condensed tannins

· A discernible positive impact was evident on N retention, growth rate and wool production in lambs given supplement containing 1.5% condensed tannins from Ficus infectoria leaves.

· Supplement containing Ficus infectoria leaves (upto 16%) was found to be economically viable for lambs during growth period.

Acknowledgement  

This study was financially supported by funds provided by the Indian Council of Agricultural Research (AICRP), New Delhi, India.

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Received 23 March 2007; Accepted 8 October 2007; Published 12 December 2007

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