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Effects of medicated and non-medicated molasses-urea multi-nutrient blocks in helminth control in a
Dorper flock
JM Nginyi, JM Mugambi, MK Rugutt, I.N Ogali and D.K. Wamae Helminthology division, Veterinary Research Centre, Muguga North, P.O. Box 32, 00902 Kikuyu, Kenya. e-mail: [email protected] Abstract
A study to investigate the effect of medicated molasses-urea multi-nutrient blocks in a flock of Dorper ewes and lambs in helminth control, risk of development of anthelmintic resistance and host immunity was carried A Faecal egg count reduction test at the beginning of the ewes experiment showed a high efficacy of 98% for albendazole. At the end of the six months of exposure to medicated and non-medicated blocks, the efficacy remained high at over 98%. The results of faecal egg counts showed that the groups of ewes (both Dorper and Red Maasai) on medicated and non-medicated blocks had lower egg counts compared with the controls over the period that they were on feed blocks. For the subsequent period following withdrawal of the blocks, there were no significant differences (p>0.05) between the three groups. In terms of PCV and live weights there were no differences between groups. As for the lambs, there were no significant differences between the treatment groups (p>0.05) in terms of faecal egg counts, PCV and live weights. The findings showed that use of medicated and non-medicated feed blocks was effective in the control of helminth infections in grazing sheep though this was not the case with lambs. The lambs could have been overwhelmed by the infection challenge compared with the adults. Observations from the period after withdrawal of the blocks indicated that feeding the blocks did not interfere with host immunity as levels of infection amongst groups were similar. The drug in the blocks also never interfered with the efficacy of albendazole as faecal egg (Key words: medicated molasses-urea feed blocks, gastrointestinal nematodes, anthelmintic resistance) Effects of medicated and non-medicated molasses-urea blocks in helminth control in a Dorper flock: Nginyi et al Introduction
Medicated molasses-urea feed blocks (MUMB) are high energy and mineral supplement blocks incorporating an anthelmintic. The blocks can be made from a variety of ingredients depending on their local availability, nutritive value, price, existing facilities for their use and their influence on the quality of the blocks (San Soucy et al., 2000). Molasses is a by-product of sugar extraction and provides fermentable substrates and various minerals including trace elements. Because of its pleasant taste and smell, it makes the blocks very attractive and palatable to the animals besides providing energy. Urea, which provides non- protein nitrogen, is the most important component of the blocks. The urea enhances rumen activity by providing a nitrogen source for the development of large populations of desirable rumen microflora. This in turn leads to faster digestion of dry grass and faster rate of passage of feed. The microbes also make all the essential amino acids from nitrogen in urea which is about 42% (Ranjan, 1993). This can lead to increase of the intake of straw by about 40% and digestibility by 20%. Wheat bran or pollard provides the key nutrients including fat, protein and phosphorus. It also acts as an absorbent for the moisture contained in molasses and gives structure to the block. Minerals are added, mainly to supplement phosphorus, sulphur and other minerals. A gelling agent or binder is necessary in order to solidify the blocks. In this case cement is used for this purpose. A drug for the control of gastrointestinal nematodes is also included or left out. The use of medicated molasses-urea feed blocks in sheep and goats has been shown to result both in increased growth rates as well as in very low worm burdens (Raj Kower, 1991; Rafiq, et al., 2000, Gatongi, et al., unpublished data). The feed supplement is particularly useful in times of prolonged feed shortage, as occurs in the arid and semi-arid areas of Kenya. Even the use of non-medicated feed blocks can enable animals survive this period by alleviating pathological effects of chronic helminth infections. In areas with continuous rainfall, medicated blocks prevent constant re-infection with nematode parasites which would otherwise necessitate regular and frequent use of anthelmintics. The technology for making the medicated feed blocks is available for transfer to small ruminant keepers. However, there are some aspects on the use Effects of medicated and non-medicated molasses-urea blocks in helminth control in a Dorper flock: Nginyi et al of this technology which are not yet understood. These include its possible role in the development of anthelmintic resistance, effect on development of host immunity to parasites following continued use, shelf life, drug residues in milk and meat hence possible withdrawal period. The objective of this study was to investigate the benefits of using medicated and non-medicated feed bocks for helminth control in sheep as well as the possibility of any risk of anthelmintic resistance development as Materials and methods
A total of 36 pregnant Dorper ewes were purchased from ranch and brought to VRC Muguga. They were approximately two months pregnant and of uniform size. On arrival at the centre they were stabilized for a period of one month. They were then randomly divided into three groups of 12 ewes each. Each group was identified by applying a different paint colour in the neck region. The sheep were grazed on the same paddocks and supplemented with Rhodes grass hay. Water was provided ad libitum. In the evenings, they were separated into the three groups and housed separately using the colour codes on their necks. The three groups were given the following treatments during housing at night: Group 1: Medicated molasses-urea feed blocks to lick at night (painted red in the neck region); Group 2: Non-medicated molasses-urea feed blocks to lick at night (painted blue in the neck region) and Group 3: Controls (no feed blocks) - painted green. The entrance to the pen housing each group had the same colour painted for ease of identification. An initial faecal egg count reduction test (Vecruysse et al., 2002) was carried out prior to the introduction of the blocks in order to give the efficacy of the drug incorporated in the blocks before the trial. Effects of medicated and non-medicated molasses-urea blocks in helminth control in a Dorper flock: Nginyi et al The ewes in groups 1 and 2 were fed on the blocks for a period of six months. The feed blocks were then withdrawn and the monitoring continued for a further six months to determine the effect of feeding the sheep on medicated and non-medicated blocks on the development of immunity. The efficacy of the particular anthelmintic (albendazole) in the medicated feed blocks was tested again after the six month period to establish whether it had changed following continued use of the MUMB. For each of the experimental animals faecal samples for worm egg counts (Gordon and Whitlock (1939) and blood for PCV were collected in addition to recording live weights every two weeks. In the lambs trial, these were ear tagged and painted with the same colour to correspond with the group to which the dams belonged. The lambs were grazed with the ewes during the day and housed at night according to their respective groups. The parameters that were monitored included fortnightly live weights, faecal egg counts and PCV. After weaning at three months the lambs in groups 1, 2 and 3 were treated like the ewes above. During that period, the lambs were housed separately. The growth rate and levels of infection with gastrointestinal nematodes were compared between the three groups and between the Dorper and Red Maasai. On welfare grounds, a PCV cut-off of 15% was used to treat any heavily infected animals. Where necessary, the animals were clinically examined and treated for any other disease during the trial. In the ewes experiment, the results of FECRT at the beginning of the trial showed no resistance to albendazole (Table 1). Results of FECRT after the six months of treatment (Table 2) with the blocks showed that the efficacy of albendazle was similar to that prior to the start of the trial. The six months treatment with blocks into which albendazole was incorporated did not show evidence of interfering with the efficacy of the The ewes were put on the treatment for six months during which the effect of medicated feed blocks on natural helminth infections was investigated. A statistical analysis of differences between the groups showed Effects of medicated and non-medicated molasses-urea blocks in helminth control in a Dorper flock: Nginyi et al that the ewes in the control group had significantly higher FEC (P < 0.05) as compared to those in the MUMB and UMB treatment groups. However there was no significant difference between FEC of ewes in the MUMB and UMB treatment groups (P > 0.05). Similarly, there was a significant difference between the mean PCV of ewes in the control group and those in MUMB group. However there was no significant difference between MUMB and UMB and between UMB and control groups. (P > 0.05). On comparisons of the live weights, there was no significant difference between the control group and both MUMB and UMB groups. The lambs FEC, PCV and weights were monitored fortnightly until the end of the six month trial period. Results showed that FEC of the three groups increased in March and April. This coincided with the beginning of the long rains. Mean FEC of the untreated control group remained higher than the other two groups from March to May. All the lambs were treated at the end of May to reduce mortality due to helminths that was being experienced in May. This explained the decrease in mean FEC that was observed in June (Figure 1). Statistical analysis of FEC data showed no significant difference between the groups (P<0.05). Results of PCV showed decrease in March and April coinciding with the increased FEC observed at that period. During the same period mean PCV ranged between 20 to 22% with the untreated controls having PCV means as low as 19% (Figure 2). However, statistical analysis of PCV data showed no significant difference between the groups (P<0.05). Similarly, there was no significant difference in lamb weight gain between the Discussions and conclusions
Nutrient deficiencies (particularly protein, energy and minerals) and parasitic helminth infections are common in ruminant livestock (Zahari et al., 2006) and are responsible for poor performance in terms of growth rate, milk yield and reproduction. Heavy mortality is also a common feature in young animals. The medicated Effects of medicated and non-medicated molasses-urea blocks in helminth control in a Dorper flock: Nginyi et al molasses-urea multi-nutrient blocks provide double benefits of nutrient supplementation and helminth control particularly in small ruminants. The results from this trial for both the lambs and ewes showed that medicated and non-medicated feed blocks were effective in the control of gastrointestinal helminthes. Although, no significant differences were recorded between different groups, infection levels were higher in the untreated. It was not clear why there was no significant difference between FEC of ewes on medicated and those on non- medicated blocks. It could be that ewes on the non medicated blocks had improved immunity resulting from the mere nutritive supplementation (Coop and Holmes, 1996). The fear by some use of the medicated block technology that continued use could result in development of resistance by the parasites was worth investigating. The results showed that continued use of the medicated blocks by ewes for a period of six months did not affect the efficacy of albendazole. Although data from a longer period of exposure can be even more reassuring, the results from this study helped to dispel fear of using the blocks continuously. Further to the results from this experiment, its recommended that data other aspects on the use the blocks including tissue residues and possible withdrawal periods for livestock products (milk and meat) be investigated. Such data will be necessary for the commercialization of this technology. Acknowledgements
We are grateful for KAPP for providing funds to carry out this work. The valuable input by the technical staff of helminthology laboratory at VRC is specially acknowledged. References
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Table 1: Results of FECRT at the beginning of the experiment

20.58 99.97
-30.22 99.93

Table 2: Results FECRT after withdrawal of blocks

98.10 98.44
85.71 96.10

Table 3: Results of mean FEC in the three treatment groups in the Dorper flock at the treatment
period.
Treatment Control

Table 4: Results of live weight results in the Dorper flock during the treatment period
Treatment Control
Effects of medicated and non-medicated molasses-urea blocks in helminth control in a Dorper flock: Nginyi et al
Figure 1: Mean FEC of lambs during the trial period.
USE OF MUMB ON LAMBS
Sam pling Interval (Months)

Figure 2: Mean PCV of lambs during the treatment period.

USE OF MUMB ON LAMBS
Sam pling Interval (Months)

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