Materials and methods

In an attempt to find answers to these questions three experiments were carried out. The first two experiments were conducted to investigate the role of ruminants in the dissemination of buda. The third experiment evaluated buda's nutritive-value. Experiment 1 involved evaluation of budainfested sorghum fed to animals, and experiment 2, the response of buda seed to incubation in rumen liquor in vivo and in vitro.

Experiment 1

Three animals - a goat, a sheep, and a camel - were fed for four weeks, commencing 1 September 1979, on forage sorghum (Sorghum bicolor var. Abu Sabeen) which was heavily invested with buda. Faeces of each animal were collected daily and spread on hard cloth material under the sun to dry. Two weeks after feeding was discontinued, the sun dried faeces were collected and ground into powder using a large local wooden mortar. Subsamples of faeces 100 9 each were used as inoculum material. Clay pots (12 cm diameter) were filled with 2 kg of river silt to which the inoculum material was added as required. There were four treatments, using soil inoculated with (a) infested goat faeces, (b) infested sheep faeces, (c) infested camel faeces, and (d) no faeces (control). Each pot was sown with eight seeds of sorghum, which were later thinned to four seedlings per pot. A randomized complete block design with four replications was used. Statistical analysis was performed on transformed data (square roots).

Experiment 2

Seeds of three buda populations - from Shambat, Medani, and Abu Na'ama - were collected in November 1979, and in August 1980 were subjected to incubation periods in rumen liquor in vivo and in vitro to test the effect on their germination capacity.

In the in vivo part of the experiment, 0.01 9 samples of each seed population were wrapped in 2 x 2 cm squares of Nitex material, which were then tied firmly into bags using synthetic plastic string with a lead of about 30 cm. The bags were suspended in the rumen of a fistulated sheep for different periods of time. There were five treatments: incubation for one day, incubation for two days, incubation for four days, incubation for eight days, and no incubation (control).

At the end of each treatment, the seeds were removed from the bags and washed thoroughly with distilled water and then were sterilized by soaking in a 1 per cent chlorine solution (as sodium hypochlorite) for five minutes. They were then washed thorouqhiv again and left to dry overnight on Whattman filter paper.

Each sample was divided into six portions placed on separate discs, with approximately 30 seeds per disc. The seeds were then set up for preconditioning at 23 C on moist giass-fibre filter paper as described by Parker et al. (1977).

The discs of preconditioned buda seeds were dabbed on dry filter paper to remove excess moisture and placed in groups of six in a petri dish which contained glass-fibre filter paper moistened with 5 ppm of GR 45 (synthetic germination stimulant). The dishes were then closed, wrapped in polyethylene bags, and incubated at 33 C for 24 hours. After this incubation period the germinated seeds were counted.

The in vitro part of the experiment was carried out under laboratory conditions using Tilley and Terry's (1963) technique for in vitro digestion of forage crops. Statistical analyses were performed on transformed data (arcsin).

Experiment 3

An air-dried sample of buda was taken from a random sample collected at different times of the growing season and from different geographical locations within Sudan. The plant was chopped into small pieces and ground in a Christy Norris mill using a 0.8 mm sieve. The dry matter of the weed was then determined and the proximate analysis was carried out according to the official methods of analysis of the Association of Official Agricultural Chemists (AOAC 1956).

Buda was also fed to six lambs (Sudan desert-sheep) for a period of 17 days in order to determine its digestibility and nitrogen retention. During the experimental period the animals were housed in metabolic crates especially designed for total urine collection. Faeces collection was carried out by canvas bags fitted to the animals by harnesses.

The material under investigation was offered ad libitum, and free access to water was maintained. The experiment started with a 10day preliminary period in which no faeces or urine collections were made. This period was to ensure the adaptation of the animals to the harnesses, bags, and crates and of the rumen microbes to the feed being consumed by the animals (Lloyd et al. 1956). The feed was offered once a day, at 8.00 a.m. Any residues from the previous day were collected at 7.30 a.m., dried, and weighed, and the amount was deducted from the drymatter weight of food provided. Daily subsamples of the food being offered and of the residues of each animal were treated in a manner similar to that described by El-Hag (1976). . and urine from each animal were collected separately each day before providing the day's ration and received a treatment similar to that described by Abou Akkada and El-Shazly (1965).

The dried samples of the residues and faeces were ground in the mill mentioned above, and the samples were redried before weighing for analysis. Total nitrogen in the urine was estimated by the micro-Kjeldahl method used by El-Shazly (1958).

On the last day of the experimental period, samples of rumen liquor were obtained by means of a stomach tube. The first sample was collected at 8.00 a.m., just before introducing the feed, and the second about three hours after feeding. The rumen liquor was strained through two layers of gauze and kept for immediate analysis. Total VFA and ruminal ammonia nitrogen were determined by the method explained by Abou Akkada and El-Shazly (1958, 1965).

TABLE 10. Mean number of buda (Striga hermonthica) plants per pot