Mulberry leaves as sheep feed supplement // 10 Aug 2009

Mulberry leaves (Morus alba) are growing under varied climatic conditions, ranging from temperate to tropical, all over the world. The biomass yield of fresh leaves is often in the order of 25-30 tonnes/ha/year with a cutting interval of about 9-10 weeks, while leaves have a high protein content (18 to 25% in DM) and high (75 to 85%) in

vivo DM digestibility (Ba et al. 2005). Therefore mulberry leaves have a high potential as a protein-rich forage supplement to be used in feed for monogastrics, ruminants and rabbits (Benavides 2000). Since mulberry leaves are rich in nitrogen, sulphur and minerals (Singh and Makkar 2002) they have the potential to be used as a supplementary feed for improving livestock productivity.

 

 

However, little information is available on their nutritive value and benefits, as a high-quality supplement to low-quality roughages or replacing grain-based concentrates in ruminant feeding. The objective of the present study was to evaluate the nutritional value of mulberry leaves in terms of chemical composition, nitrogen solubility, non-protein nitrogen, protein fractionation and in vitro true digestibility of DM and to determine the effects of mulberry leaves, partially substituting lucerne hay and concentrates, to the digestibility of sheep diets.

 

Mulberry leaves (the white mulberry variety Local 1) were obtained from a plantation kept by the Department of Sericulture at the Agricultural University of Athens that was periodically harvested. The mulberry leaves were

Mulberry is cultivated on a semi-extensive scale in various parts of Greece, particularly in northern areas.

shadow dried for 12 days before their nutritional value was determined in vitro and used in a digestibility trial with sheep at the Department of Nutrition Physiology from the same University. All samples were ground in a Wiley mill (1-mm screen) and stored in airtight jars before further nutritional evaluation. Nitrogen (N) solubility was determined using the solvents: a) McDougall’s buffer, b) 0.02 N NaOH and c) 0.15 N NaCl, as described by Crooker et al. (1978). Solubility was determined using a concentration of 25 mg feed N/100 ml of solvent (Wohlt et al. 1973; Crooker et al. 1978).

 

The amount of extracted N was determined in a 50-ml aliquot of supernatant liquid and the soluble N reported as a percentage of the total N in the feed. The soluble non-protein nitrogen (NPN) was determined in the 50 ml solution containing the soluble N fraction by precipitating the protein with trichloro-acetic acid (TCA) using the procedure described by Ganesh and Grieve (1990). Total true protein content represented the difference between the crude protein and the soluble NPN fraction. Soluble protein fractions were obtained via consecutive

extraction procedures (Gavrilyuk et al. 1973) that used 1 N NaCl in phosphate buffer (pH 7.0), 70% ethanol and 0.05 N NaOH. By classic definition (Osborne 1924), these solutions extracted albumins, globulins, prolamins and glutelins, respectively. The remainder was calculated by difference and characterised as insoluble (or structural) proteins.

 

All chemical analyses were done in triplicate. Samples were ground through a 1-mm screen and analysed for contents of dry matter, organic matter (OM), ether extracts (EE), crude fibre (CF) and crude protein (CP) by standard methods of the Association of Official Analytical Chemists (1990). The N was determined on a Kjeltec Auto 1030 Analyzer (Tecator) using selenium catalyst and 1% boric acid with bromocresol green/ methyl red indicator solution. The filtrate (50 ml) was analysed by the macro-Kjeldhal procedure (AOAC 1990) for soluble N determination. Neutral detergent fibre (NDF), acid detergent fibre (ADF), acid detergent lignin (ADL), cellusose and hemicellulose contents were analysed as outlined by Van Soest et al. (1992). Chromic oxide (Cr2O3) was determined in samples of feed and faeces by acid digestion and spectrophotometry at 440 nm following the procedure described by Fenton and Fenton (1979). The in vitro true digestibility of DM (IVTD) was estimated using sheep rumen liquor as the source of microbial enzymes for the ruminal phase of digestion according to Goering and Van Soest (1970) using a neutral detergent solution and a DAISYII Rumen Fermenter.