Supplementing cassava root meal and processed cassava

leaves to diets based on forage maize or natural grasses

and rice straw for growing male swamp buffaloes
 

Dao Lan Nhi, Mai Van Sanh and Le Viet Ly

National Institute of Animal Husbandry, Hanoi

Abstract

Two experiments were conducted to evaluate the effects of different levels of cassava root meal and processed cassava leaves as supplements to diets based on whole maize plants or natural grasses and rice straw on the performance of growing male buffaloes. In each experiment, 20 male buffaloes of 19 to 21 months of age and body weight of 180 to 210 kg were divided into 4 groups of 5.  In Experiment 1, the buffaloes were fed whole maize plants (10 to 12 kg/day) and rice straw (ad libitum) and supplemented with a mixture of cassava root meal (CRM) and cassava leaf meal (CLM) (ratio 1:1) with levels of 0.8, 1.6, 2.4 and 3.2 kg/day.  In Experiment 2, the buffaloes were fed natural grasses (12 to 15 kg/day), rice straw (ad libitum), supplemented daily with 0.5 kg cassava root meal plus 1.4, 2.8, 4.2 or 5.6 kg ensiled cassava leaves (ECL).

Increased levels of cassava root meal and cassava leaf meal, or ensiled cassava leaves, resulted in increased dry matter (DM) intake and body weight gain.   

Key words:  Buffaloes, maize, rice straw, cassava, leaves, roots, growth
 

Introduction

The major feeds for buffalos are natural grasses and crop residues such as maize stover and rice straw, which have low protein and energy contents. Supplementation with high protein and energy feeds is necessary for the growing buffalo to maximize the potential for meat production. In Vietnam, cassava is one of the most important crops for farmers in mountainous provinces. The yield of cassava leaves during root harvesting is reported to be 2.5 to 3.0 tonnes/ha, containing 500 to 600 kg dry matter and 110 to 130 kg crude protein (Bui Van Chinh, personal communication). However, farmers in the mountain provinces do not pay much attention to using cassava leaves as animal feed. The great limitation of using cassava leaf as animal feed is its concentration of cyanogenic glucosides (Göhl 1998). The most common procedures for reducing the concentration of these substances are sun-drying and ensiling. It has been claimed  that cassava leaves should be ensiled or dried before feeding to ruminants (Wanapat et al 1997; Wanapat 2001); however,  there are also reports that the fresh leaves can be fed in fresh form, and as a sole protein supplement support excellent growth rates in cattle fed molasses-urea (Ffoulkes and Preston 1978) or untreated rice straw (Seng Mom et al 2001). Good results with using fresh cassava leaves have also been reported in goats (Seng Sokerya and Rodríguez 2001).

The objective of the following experiments was to study the effects of different levels of cassava root meal and processed cassava leaves as supplements to diets based on natural grasses and crop residues on the performance of growing male buffaloes.
 

Materials and methods

Location:

The experiments were carried out at the Centre for Livestock Research and Development in a mountainous region of Thai Nguyen province, and Dai loc Village in Vinh Phuc province in 2000-2001.

Experimental design:

Forty male swamp buffaloes at 19 to 21 months of age, with live weights of 180 to 210 kg were used in two experiments. In each experiment, 20 buffaloes were blocked and divided into 4 groups (5 per group) with a randomized block design according to body weight and age of the animals.  In Experiment 1, the buffaloes were fed basal diets of whole maize plant (10 to 12 kg/day), rice straw ad libitum, and supplemented with 0.8, 1.6, 2.4 and 3.2 kg/day of a mixture of cassava root meal (CRM) and cassava leaf meal (CLM) (ratio 1:1). In Experiment 2, the buffaloes were fed natural grasses (12 to 15 kg/day), rice straw ad libitum  and supplemented daily with 0.5 kg cassava root meal plus 1.4, 2.8, 4.2 or 5.6 kg ensiled cassava leaves (ECL) (Table 1).   

Processing cassava leaves:

The fresh cassava leaves were collected during root harvesting. They were sun-dried and ground to make leaf meal (CLM) or ensiled with 10% cassava root meal and 0.1% salt  for 45 to 50 days before feeding.

Animal feeding and management:

The maize plants or natural grasses and rice straw were given at 7:00, 11:00, 15:00 and 18:00 h daily. Cassava root meal and cassava leaf meal  (or silage) were given at 7:00 and 15:00 h daily. The bufaloes were kept individually indoors with daily exercise for a few hours outside the barn. Water was available in a trough, which was cleaned every day.

Data collection procedure:
 

The feed offered was weighed daily. Refusals were weighed every morning before new feeds were given. Body weight was determined every month (animals were weighed in the morning before feeding and drinking). Feed composition was analyzed twice a month. The duration of the experiment was 3 months (excluding 10 days of feed adaptation).

Statistical analysis:
 

Data were  analyzed by ANOVA, using the General Linear Model option of the Minitab (1998) software. Sources of variation were treatments and error.
 

Results and discussion

Chemical composition of feeds:

The chemical composition of the diet ingredients was in accordance with expectations (Table 1). The mean content of HCN was 14.6 mg/kg in ensiled cassava leaves and 18.7 mg/kg in cassava leaf meal. These data are lower than those reported by Bui Van Chinh et al (1992) (23 to 34 mg/kg) and Du Thanh Hang et al (2000) (60.9 mg/kg).

Feed intake and body weight gain of buffaloes in Experiment I
 

Buffaloes in the first 3 treatments readily consumed most feeds supplied, indicating no toxic or palatability problems. However, buffaloes on the highest level of the mixture of cassava leaf and root meal consumed only 80% of the amount offered (Table 2). Dry matter intake and live weight gain increased following the increase of CRM and CLM, up to 2.4 kg/day.