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6. Effect of grass or cassava foliage on growth and nematode parasite infestation in goats fed low or high protein diets in confinement
Authors: Seng Sokerya and Preston T R 2003
Livestock Research for Rural Development (15) 8 Retrieved, from
http://www.cipav.org.co/lrrd/lrrd15/8/kery158.htm
Summary: There were two experiments conducted from April to October 2002 at the ecological farm of the University of Tropical Agriculture (UTA), about 12 km from Phnom Penh , Cambodia . This region is located in a monsoon tropical climate where mean air temperature is in the range of 33 to 40 ° C in April to May and 20 to 29 ° C from June to December. The goats were confined individually in wooden pens with 1*1.5 m floor area, fitted with raised slatted floors about 1.2 m higher from the ground in a building with open sides and a thatch roof. The feeders are situated on the outside of the pen, where the animals can put their head to eat or drink. This also facilitates the feeding and collection of feed residues.
Experiment 1 : The three treatments were different forages, or combinations of forages, as supplements to a basal diet of Brewer's spent grains. The supplements were G (cut natural grass), C (cassava foliage), GC (a mixture of grass and cassava foliage [50:50 DM basis]). There were four replications in a randomized block design (RCBD), after blocking the animals on the basis of live weight and sex. The experimental period was 80 days. Twelve crossbred Bach Thao goats (6 males and 6 females) were used in this experiment with the average body weight of 20 kg for males and 16 kg for the female goats of between 5 to 8 months of age. They were treated with Ivermectin before starting the experiment. There was an adaptation period of one week before starting the experiment to accustom the goats to the housing and the feeding system. Brewer's spent grain was used as the basal diet at a restricted level, of 50% of the expected ad libitum intake, which was estimated to be about 4% of liveweight on dry matter basis (Peacock 1996). The supplements were foliage from cassava, cut natural grasses or the mixture of the two given on a 50:50 (DM basis) ad libitum. The feeds were offered 2 times per day in the morning about 10 am and in the afternoon about 3 pm. Water was always available. Cassava foliage was harvested daily from semi-perennial plots in the ecological farm of UTA. The foliage (leaves, petioles and green stems) was from re-growths harvested regularly at 50 to 80 day intervals (Preston et al 2001), the hard stems being cut about 50cm from the ground for the first harvest and 5 to 10cm from the point of the first cutting for the next harvest. The natural grasses were collected in the field around the area of the ecological farm every day in the morning before feeding. Live weight was recorded at the beginning, every 10 days and at the end of the experiment. The amounts of feed offered and refused were measured and recorded daily, separately for the basal diet and the supplements. Representative samples of feeds offered and refused were analysed for dry matter by micro-wave radiation (Undersander et al 1993) and nitrogen content (AOAC 1990). The cassava foliage was analysed for the concentration of HCN (AOAC 1990) and condensed tannins (Burns 1971). After weighing the animals, faecal samples were taken directly from the rectum to determine the concentrations of the parasite eggs (EPG).
Experiment 2 : 4 treatments were arranged in a CRD design using 16 goats and a basal diet of wheat bran. The treatments were: C (cassava foliage), CG (mixture of grass and cassava foliage [50:50 DM basis]), G (grass) and Gt (grass plus injection of Ivermectine at the beginning of the experiment). The C, CG and G treatments followed those in Experiment 1 (but without anthelmintic), while the Gt treatment was the same as "G" but with injection of Ivermectin. The basal diet of brewer's grain was also replaced by wheat bran which has a lower protein content to allow a better observation on the effect of the supplementation. The animals in each treatment were blocked according to EPG level in the beginning of the trial. The highest fecal egg count animals were allocated to the cassava treatment (C), and the lower ones to the grass treatments. There were 4 replications (individual animals) in each treatment and the experimental period was 70 days. Sixteen female goats of the local breed were used. The body weights were in the range of 8 to 12 kg and the ages between 3 and 5 months of age. A longer period of adaptation (21 days) was necessary because the goats on the "C" and "CG" treatments were slow to adapt to the cassava foliage. Feeding and management were similar to the procedures used in Experiment 1, except that wheat bran replaced the Brewer's grain and the feeding level was restricted to 200 g (air-dry basis) daily. The measurements were similar to those employed in Experiment 1. In addition, at the end of the trial, one goat from each treatment was slaughtered to determine the total worm burden in the intestinal gut. The eggs in the faeces were cultured to identify the species of the infective larva using the faecal sample from the slaughter animals. Digestibility of dry matter, organic matter and nitrogen was determined by taking samples of feed, feed residue and faeces over 5 days at the end of the trial, bulking them to obtain representative samples, which were then analysed for acid insoluble ash using the method of Van Keulen and Young (1977). The faeces samples were taken from voided excreta under the individual pens.
Abstract: Two experiments were conducted to find out the effect of cassava foliage compared with grass on the growth rate and parasite infestation of growing goats. Twelve crossbred goats, treated with Ivermectin before starting, were used in experiment 1 which lasted 80 days. There were 3 treatments according to the source of forage (Cassava alone, Cassava + Grass [50:50 percent in DM] and Grass alone) as supplement to a basal diet of brewer's grains. Experiment 2 was with 16 local goats allocated to 3 treatments with no initial injection of Ivermectin (Cassava alone, Cassava + Grass [50:50 percent in DM] or Grass alone) and a 4th treatment of grass alone with injection of Ivermectin at the start. In this experiment the basal diet was wheat bran. In both experiments, the forage supplement supplied about 50% of the diet DM. The goats given diets containing cassava foliage had faster growth and better feed conversion. EPG were either lower on cassava supplemented diets compared with the grass alone (Experiment 1) or declined with time from high initial values (Experiment 2). DM digestibility was apparently depressed on the cassava, compared with the grass, diets but this negative nutritional effect appeared to be more than compensated by the much higher protein intakes with cassava. It is suggested that the better performance on the cassava diets was due to the higher protein intake and that the protective action against nematode parasites was due to the content of condensed tannins.
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