Effects of drenching soybean oil and fish oil on intake, digestibility and growth of cattle in the Mekong Delta, Vietnam
 

Nguyen Thi Hong Nhan^*, Nguyen Trong Ngu^*, T R Preston^** and R A Leng^***

^*College of Agriculture, Cantho University, Cantho, Vietnam
 nthnhan@ctu.edu.vn; ntngu@ctu.edu.vn
^**UTA Colombia, AA48 Socorro, Santander, Colombia
trpreston@mekarn.org
^***PO Box 814, Coolum Beach 4573, Australia
rleng@ozmail.com.au

Abstract

Three Sindhi-Yellow cattle were fed a basal diet of rice straw ad libitum and para grass (1% of LW on DM basis) and given a single drench of 6 ml/kg LW of either soybean oil or fish oil. The experiment was carried out according to a 3*3 Latin square design, beginning with 20 days of adaptation followed by 21 days of data collection, in which three sub-periods of 7-days were divided to measure feed intake and digestibility. In a second experiment, 15 Sindhi-Yellow growing cattle (136-143 kg) at a cooperative farm were arranged into 3 treatments with 5 replicates. The cattle were fed on the same diets as in experiment 1 and kept for 90 days after being given a single dose 6 ml/kg LW of soybean oil or fish oil.

In both oil treatments, apparent digestibility was improved from 54.4 (control) to 61.3 and 60.9% for soybean and fish oils. In the on-farm trial, growth rate increased to 383 and 387g/day in cattle given the oil drench compared to the control animals (338 g/day). Feed conversion ratio tended to be better in cattle given the oil drench.  There were no differences between fish oil and soybean oil in the degree of beneficial effects on the cattle. Both can be applied for fattening cattle under farm conditions.

Key words: Defaunation, feed conversion, grass, growth, on-farm, protozoa, rice straw,

Introduction

The first research published on this subject (Nguyen Thi Hong Nhan et al 2001) was stimulated by observations of farmer practice in Central Vietnam. Subsequent experiments in Cambodia (Mom Seng et al 2003), in An Giang province of South Vietnam (Nguyen Thi Hong Nhan et al 2003) and in Cantho University (Nguyen Thi Hong Nhan et al 2007a), confirmed that soybean oil eliminated the protozoa from the rumen resulting in faster growth rate of the cattle.. In addition to soybean oil, fish oil is also used by farmers in An Giang province for fattening their cattle about 3 months before slaughtering. The use of fish oil originated from the fact that catfish oil is abundant in the region and it is less competitive with human needs.

In all the trials done so far, there has been no detailed comparison between vegetable oil and fish oil. It is not known if cattle responses are similar for both these sources of long chain fatty acids. In the Mekong Delta (MD), many farmers have specialized in cattle fattening; they purchase lean cattle, often from Cambodia, and fatten them with a combination of grass, rice straw and rice bran. It is therefore of considerable interest for these farmers to know the relative advantages of the two sources of oil as a means of improving the efficiency of their fattening system.

The objectives of this research were therefore to determine the effects of the two sources of oil on digestibility and growth performance of cattle fed on rice straw and grass.
 

Materials and Methods

Experiment 1

Treatments and design

Three growing crossbred Sindhi-Yellow cattle (145-160 kg) were allocated to three treatments according to a Latin square design. The treatments were:

RG: Rice straw ad libitum plus natural grass (1% LW, DM basis)
RGSO: Similar to RG with a single dose drench of soybean oil at 6ml/kg LW
RGFO: Similar to RG with a single dose drench of fish oil drench at 6ml/kg LW

All cattle were given a rumen supplement containing 1.5% sulphur, 5% salt, 5% bone meal, 73.5% rice bran. The oil was given orally (Photo 1).

Experimental procedures

The animals were vaccinated against foot and mouth disease and de-wormed before the initiation of the experiment. After 20 days of adaptation, the cattle were given a single dose of soybean oil or fish oil (Photos 2 and 3) followed by three sub-periods of 7 days each to measure feed intake and digestibility.

Data collection

Feeds offered and refused were recorded daily during each consecutive 7 day period. Feces were collected daily and frozen at –18C for later analysis. The determination of dry matter (DM) was by drying at 65ºC for 24 h. Analysis of crude protein (CP), ether extract, ADF and NDF were according to AOAC (1990).  

Experiment 2

Fifteen young beef cattle with initial live weight from 136 to 143 kg on a cooperative farm were allotted to the same 3 treatments and the same basal diet as in Experiment 1. The cattle were fed for 90 days after being drenched orally with the oil.  During this period, they were totally confined in a shed; drinking water and rumen supplement  were available all the time.

The cattle were weighed on 2 consecutive mornings at the beginning, and after 30, 60 and 90 days of the trial. Feed intake and residues were measured daily and representative samples were collected and bulked weekly for chemical analysis including DM, CP, NDF, ADF and ash.

Statistical analysis

Data on feed intake and digestibility were subjected to analysis of variance using the least squares General Linear Model (GLM) procedure of the Minitab Statistical Software Release 13.2 (2000). Sources of variation in Experiment 1 were treatment, animals, periods and error; and in Experiment 2, treatments, replicates and error.
 

Results and discussion

Experiment 1

The composition of the rice straw and grass is in Table 1.

There was a very slight indication (P=0.30) that intakes appeared to be depressed during the first 7 days following the oil drench (Table 2). Coefficients of apparent digestibility of DM and crude protein were increased in days 8-15 and 16-21 by some 7 percentage units by both types of oil drench (an overall increase of 16%).