Effect of drenching with cooking oil on performance of local “Yellow” cattle fed rice straw and cassava foliage

 Nguyen Thi Hong Nhan, Nguyen Van Hon, Nguyen Trong Ngu, Nguyen Thi Thu Hong*, T R Preston** and R A Leng***

 Cantho University, Cantho, Vietnam
nthnhan@ctu.edu.vn
*An Giang University, An Giang
** regpreston@utafoundation.org
*** rleng@ozemail.com.au

Abstract

The experiment was carried out at a cooperative farm with 20 female cattle of the local “Yellow” breed, divided into 10 groups (pens) with 2 animals in each  (5 replicates per treatment). The treatments were administration of an oil drench (groundnut oil) or no oil drench. The basal diet was: Urea-sprayed rice straw (2% urea) offered ad libitum + fresh cassava leaves (3 kg/day). The experiment lasted 90 days. The groundnut oil drench (5 ml / 1 kg live weight) was given once at the beginning of the trial. The cattle were weighed (average of two daily consecutive weighings) at the beginning, and after 45 and 90 days.  Samples of rumen fluid were taken by stomach tube before eating in the morning, on the day before oil treatment, and after 45 and 90 days, for counting of protozoa and determination of rumen ammonia and pH.

Growth rates were 28% higher (234 g/day) for cattle given the oil drench compared with the control (183 g/day). After 45 days the rumen protozoa numbers and rumen ammonia concentrations were depressed in cattle given the oil drench compared with the control animals (0.272*10⁵/ml vs 0.40*10⁵/ml) and  (116 vs 133  mg/litre), respectively.

Key words: Cassava leaves, cattle, drench, growth, oil, rice straw, urea
 

Introduction

Eliminating the protozoa from the rumen of cattle and sheep has been shown to improve growth rates, as the bacterial population increases and the microbial protein flow from the rumen is increased when the protozoa are absent (Leng 1989). The early procedures for eliminating the protozoa required dosing the animals with a chemical surfactant, and was a difficult procedure which often resulted in the death of the animals, thus there was little impact of the technology at farmer level. Recently, it was observed by scientists in Central Vietnam,  that oral administration of a single dose of groundnut oil was regularly used by farmers in the area as their experience was that this resulted in better performance of their animals.  These observations were followed up by Nguyen Thi Hong Nhan and co-workers (2001) who showed that the effect of the oil drench was to kill the rumen protozoa and that the treated animals subsequently grew faster with better feed conversion.  These findings were confirmed by Seng Mom et al (2001) in a trial in Cambodia in which local cattle fed rice straw, a rumen supplement (urea and minerals) and fresh cassava foliage, grew faster after being dosed with standard cooking oil purchased in the local market. These researchers also showed that the effect of the oil was mainly against the large protozoa (Holotrich and Dasytrich spp), and because these organisms have a half life of over 120 days (Leng 1989), there was a considerable delay before they were re-established in the rumen.  By contrast, the smaller protozoa (mainly Entodinia spp) were quickly re-established (half-life of less than 20 days; Leng 1989), and returned to normal levels within about one month of the oil treatment.  It was hypothesised that, as the small protozoa occupied less space in the rumen than the large protozoa, the beneficial effects of higher bacterial population would be maintained (Seng Mom et al 2001).

The research to be reported in this paper aimed to demonstrate at farmer level the advantages of the oil treatment in local cattle fed on rice straw as the basal diet.

 

Materials and methods

Experimental design

The experiment was carried out at a cooperative farm in An Giang province. Twenty female cattle of the local ("Yellow") breed (average initial weight 82 kg) were selected and allocated  at random into 10 pens (Photo 1) each with 2 animals, to give 5 replications of the two treatments which were:

• C:  Urea-sprayed rice straw (2% urea) offered ad libitum  + fresh cassava leaves (3 kg/day)

• GO: The same as "C"  but the animals were dosed with groundnut oil (5ml/kg live weight) at the beginning of the trial.

The experiment lasted 90 days.

Feeding system

Urea was sprayed on the rice straw (2 kg urea dissolved in 50 litres water and sprayed onto 100 kg rice straw) using a watering can immediately before it was offered to the animals.  The sprayed straw was supplied at approximately 50% more than the recorded intakes.  Cassava leaves (including petioles) were harvested from the lower parts of cassava plants on nearby farms, that had been planted for root production (the farmers considered that this procedure did not affect the subsequent root yield). The leaves were fed fresh immediately after they were  harvested at a fixed level of 3 kg/animal/day. The groundnut oil was purchased in the local market. I t was administered to the animals after an over-night fast, using a bamboo tube as a "dosing" bottle (Photo 2 ).

 

Photo 2: Administering the groundnut oil	Photo 3: Taking the rumen samples with a stomach tube and vacuum pump

Measurements

Intakes were recorded separately of the straw and the cassava leaves. The cattle were weighed on two consecutive days at the beginning, after 45 days and after 90 days. Samples (about 100 ml) of rumen fluid was taken with a stomach tube using a  vacuum pump) in the morning before eating (Photo 3), on the day before oil treatment, and after 45 and 90 days, for counting of protozoa and determination of rumen ammonia and pH. pH was determined immediately with a portable digital meter. Samples of the rumen fluid were put into an ice-box to transport them to the College of Agriculture in Cantho University. Part of the sample was distilled directly for determination of ammonia. Another portion of the sample was treated with methylene blue to stain the protozoa which were counted in a Malasser cell (0.2mm chamber), under a microscope at 10X magnification. DM and N in feed samples and ammonia in rumen fluid were determined according to AOAC (1990) procedures.

 

Results and discussion

Intake of rice straw and cassava leaves was depressed during the first 45 days following drenching with groundnut oil (Table 1). From 46 to 90 days,  intakes of rice straw were the same on both treatments, but continued to be lower for the cassava leaves in the cattle dosed with the oil. Overall from 0 to 90 days, intakes of rice straw tended to be lower (P=0.12) for cattle dosed with oil and were significantly lower for the cassava leaves. The reduced intake of straw and cassava leaves in the 45 days immediately following oil administration is presumed to be due to the disturbance of the rumen ecosystem caused by the high dose of oil. A similar depression of feed intake following oil treatment was also noted by Nguyen Thi Hong Nhan et al (2001).  There were no apparent toxic effects from feeding fresh leaves of cassava which agrees with the experiences of Seng Mom et al (2001) with cattle, and Seng Sokerya and Rodríguez (2001) and Theng Kouch et al 2003) with goats.

Growth rates did not differ during the first 45 days after oil treatment but were higher in the 46 to 90 day period and in the overall 90 days of the trial, for the cattle dosed with oil  (Figure 1). These findings are similar to those reported by Nguyen Thi Hong Nhan et al (2001) and Seng Mom et al (2001).