Evaluation of head lettuce residue and Mimosa pigra as foliages for rabbits compared to Ruzi grass: Effect on growth performance and production costs on-farm

Supharoek Nakkitset, Choke Mikled^* and  Inger Ledin^**

Royal Project Foundation, Livestock Extension and Development Section,
65 Moo 1 Suthep Road, Maung, Chiang Mai 50200, Thailand.
inalaw@yahoo.com
^*Chiang Mai University, Department of Animal Science, Faculty of Agriculture,
Chiang Mai 50200, Thailand.
^**Swedish University of Agricultural Sciences, Department of Animal Nutrition and Management,
PO Box 7024, 75005 Uppsala, Sweden.

Abstract

Seventy-two weaned rabbits, crossbreds between New Zealand White and the native breed, with an initial live weight of 731 g were distributed to four farmers, 18 rabbits to each farmer, in the Chiang Mai area. The rabbits on each farm were randomly assigned to three treatments according to a Randomized Complete Block Design with farms as block. The treatments were diets with three different foliages, Ruzi grass, head lettuce residue and Mimosa pigra. All rabbits were fed a basal diet of a commercial concentrate at 2% dry matter (DM) of body weight (BW)

There were differences (P<0.001) in total feed DM intake and also in intake of foliages and concentrate. Feed intake was significantly lower for the rabbits offered Ruzi grass than for the other treatments. The finishing weight and daily gain during the thirteen weeks of the experiment were significantly higher for head lettuce residue and Mimosa pigra than for Ruzi grass. The finishing weight was 2.501 kg, 2.488 kg and 2.177 kg and the daily gain 19.4 g, 19.2 g and 15.9 g for the head lettuce residue, Mimosa pigra and Ruzi grass, respectively. Feed conversion ratio was lowest for the head lettuce residue diet, significantly lower than for Ruzi grass and Mimosa pigra (P<0.001).

The highest net profit per kg live weight was obtained when feeding head lettuce residue, 40 Baht/kg BW, compared to 39 Baht and 36 Baht/kg BW when feeding Mimosa pigra and Ruzi grass, respectively.

Introduction

At the present time rabbit raising is an important activity for farmers in the mountainous area in the northern part of Thailand. People belonging to the hill tribes, mostly smallholder farmers, live in this upland area, and work with agriculture in integrated farming systems such as cropping of rice, vegetables and fruit trees combined with raising of livestock. The livestock activities are usually small scale or backyard raising, based on smallholder status and land holding. Livestock raising serves as the family food security and assistance in mixed farming, and also as an insurance in case of crop failure and as a family saving (Devendra and Chantalakhana, 2002 cited by Chantalakhana et al., 2005).

Rabbits are suitable for smallholder farmers to be raised in small scale or backyard systems for subsistence with low level inputs (Lukefahr and Cheeke, 1990; Phimmasan, 2005). The hill farmers could probably produce rabbit meat with low production costs, but in fact have been raising rabbits with high feed costs. Their practice has been to feed the rabbits low quality forages, natural or improved grasses, and commercial concentrates in large amounts. This has led to high feed costs and no net profit. To solve the problem the rabbit feed should be improved by replacing the grass with foliages with higher protein content that can be found easily in the area. Devendra (1988) reported that the foliages are sources of dietary protein and can provide variety in the diet for improved growth performance and reduced feed costs.

The head lettuce (Lactuca sativa) residue, the waste of the grading process, has become a pollution problem in the mountains because the waste is dumped as garbage. Head lettuce has a high protein content of about 350 g/kg DM (Wikipedia, 2007) but also a very high water content.

Mimosa pigra is a kind of weed that is spread by seeds over many areas in South East Asia, and can be found in mountainous areas, especially in river banks and other wet areas. Vearasilp et al. (1981a) reported a potential use of mimosa as a livestock feed resource with relatively high protein content, 200 g crude protein (CP)/kg dry matter (DM). There were no negative effects reported in tests run on this thorny plant in Thailand (FAO, 1997). However, there is really no data on the appropriate use of mimosa as a feed for rabbits.

The objective of this study was to evaluate the effect of feeding head lettuce (Lactuca sativa) residue and Mimosa pigra compared to the roughage normally fed by farmers, e.g. Ruzi grass, on growth performance, feed intake, production costs and net benefit in rabbits raised on-farm.

Materials and methods

Location and climate of the study area

The experiment was carried out at 4 farms belonging to 2 centres of the Royal Project Foundation, Chiang Mai, Thailand about 140 kilometres from the city. Three of the farms belong to the Khun Phae Development Centre and the last farm to the Wat Chan Development Centre. The altitude of the areas where the farms are situated is about 1,000 m above sea level. The climate is tropical monsoon, with a wet season from May to October and a dry season from November to April. Average rainfall during the experiment was around 1,220 mm and the highest mean temperature was 27^oC and the lowest mean temperature 14^oC. The experiment started in October 2006 and finished in January 2007.

Animals and management

The animals used in the experiment were weaned rabbits of about 6 to 7 weeks of age and with an average body weight (BW) of 731 (SD=17.4) g. The experimental rabbits were crossbreds between native rabbits and New Zealand White. There were 72 animals in total, and 18 rabbits were allotted to each farm with no regard to sex. The rabbits were confined to individual cages made from metal net and bamboo with the size 90x90x60 cm. Before the start of the experiment the rabbits were dewormed using Ivermectin injection, 0.1 ml/kg BW.

Feeds and feeding systems

As the basal diet in the growth experiment a commercial feed for growing pigs from 30 kg to 60 kg was used. The CP content was about 160 g/kg DM. Major ingredients in the commercial concentrate feed were maize and rice bran as energy sources and soybean meal and fishmeal as protein sources. The concentrate was fed at a level of 2% (in DM) of BW. The concentrate was bought from the feed shop in the city.

The foliages used in the experiment were Ruzi grass, head lettuce residue and Mimosa pigra. Head lettuce residue was collected every day from the grading house at the Royal Project development centres, which are in the same area as the farms. Before being offered the head lettuce residue was air dried for 10 to 12 hours. Mimosa pigra was collected from the fields near the river bank and cut approximately 15 cm from top (leaves and stem included) and the leaves from the part >15 cm from the top were also included. Ruzi grass was available in the area around the farms. Mimosa pigra and Ruzi grass were harvested once per day at about 17.00 h.

The foliages were hung in the cage and offered ad libitum at a level of 120% of the average individual intake the previous week. Clean water was available at all times.

The foliages were fed twice daily at about 7.00 h and 16.00 h, with 50% of the feed offered at each occasion. The concentrate was offered once daily in the morning.

Experimental design

The experimental design of the growth experiment was a RCBD. The experiment had 3 treatments and 4 blocks (farms). There were 6 rabbits in each treatment.

The treatments were:

• RG: Ruzi grass (ad libitum) + concentrate feed at 2% DM of BW (control).

• HL: Head lettuce residue (ad libitum) + concentrate feed at 2% DM of BW.

• MP: Mimosa pigra (ad libitum) + concentrate feed at 2% DM of BW.

Data collection and analysis

The rabbits in the growth experiment were weighed at the beginning of the experiment and then every 7 days, always in the morning before feeding. Feed offered and refused was weighed every day to calculate feed intake and determine feed conversion ratio from DM intake. The feeds and feed residues were sampled every day for analysis of the chemical composition by proximate analysis, for dry matter (DM), ash, N and crude fiber (CF) according to AOAC (2000). Foliages in the field were sampled every week for analysis DM. The feed samples were collected by the farmers or the research assistant.

Statistical analysis

The data were analysed using the ANOVA GLM option of the Minitab version 14.12 (2004) software. Sources of variation were treatment (different foliages), block (different farms) and error. The means were compared using Tukey's pairwise comparison test. The statistical model for the growth experiment was:

Y_ij = m + T_i + B_j + e_ij where T_i= treatment, B_j= block and e_ij=random error.

Economic analysis

Economic analyses was done using current prices in Baht (B) to calculate the production cost based on total income and total expenses (concentrate and animals).

Results

The chemical characteristics of the experimental feeds are shown in Table 1. Mimosa pigra had a high protein and fiber content, 179 g and 241 g/kg DM, respectively. Head lettuce had also a high protein content but very low DM content and Ruzi grass had a high fiber content.

Total DM intake, and intake of foliages and concentrate were significantly different among the treatments (P<0.001) (Table 2). The highest total DM intake was from the Mimosa pigra diet compared to the head lettuce residue and Ruzi grass diets, 100 g, 90 g and 78 g/day, respectively.

Protein and fiber intakes were significantly higher in the Mimosa pigra diet than in the head lettuce residue and Ruzi grass diet (P<0.001). The live weight at the start and at the end of the experiment, daily gain and feed conversion ratio are presented in Table 3.