April 24, 2006	Monday	Rabi-ul-Awwal 25, 1427

In Pakistan, livestock productivity is low and genetic potential of the animals is not being fully exploited due to so many factors but worm infestation is the most important one. It is a rife, affects all classes of livestock and constantly hampering the development of livestock industry in Pakistan. The animals become unthrifty, prone to other infections and ultimately death occurs especially in young animals.

The gastrointestinal tract of animals harbor a wide variety of worms mainly nematodes, which cause clinical and sub-clinical parasitism. Among helminths, the most prevalent parasites in Pakistan are nematodes followed in order by cestodes and trematodes. The identified species of parasites included Strongyloides papillosus, Haemonchus contortus, Bunostmum phlebotomum, Oesophagostomum radiatum, Cooperia spp., Trichstrongylus spp., Toxocara vitulorum, Ostertagia ostertagi, and Nematodirus spp. In cestodes, Moniezia benedeni and Moniezia expansa have been reported.

Such parasites adversely affect the nutritional status and even cause death of the host. The economic losses to livestock industry due to worm infestation are much higher than those caused by other diseases. A lowered profitability up to 15% has been reported only due to Strongyloides spp. Some scientists have reported 76% incidence and 50% weight loss due to gastrointestinal parasites in buffalo calves.

Various studies on gastrointestinal parasites indicated that they reduce growth rate, milk yield and feed intake. Even normal parasitic loads may be responsible for reducing up to 30% growth rate in sheep. The studies showed that nematodes have an effect on milk production and deworming increases yield almost 1 litre/day as compared to control. It is also very imperative to control parasitic trematodes because they are causative agents of various diseases and are responsible for death, morbidity and lowered resistance.

An incidence up to 65.5% have been reported in cattle, responsible for progressive anemia, marked emaciation, persistent diarrhea and upto 60% mortality in cattle. In Germany, where liver trematodes were not a serious problem the annual losses were estimated to be 2.03 million marks due to liver condemnation in cattle and the losses were even higher due to the effect on milk and meat.

Tape-worms infestation reduces the slaughter yields by 3.4%, increased the water content of meat and reduced its protein and fat content. Hence, worm infestation is one of the major factors for low livestock productivity and profit. Thus, it is need of hour to control this problem through better management as is being done in developed countries.

Recently an efficacy trial of three commonly used dewormers was conducted by the scientists of University of Agriculture, Faisalabad. They compared albendazole, levamisole and oxfendazole group of anthelmintics against gastrointestinal parasites of animals by calculating number of eggs of parasite in one gram of faeces.

It was found that the maximum decrease in number of eggs was found in albendazole treated animals followed by levamisole and oxfendole. The best dewormer finalized after efficacy trial was used for performance trials. The effect of deworming on the growth rate of animals was observed. The results of present study showed that there is more weight gain in albendazole treated cow calves compared with untreated control group. In order to determine the effect of deworming on the milk yield of animals, the initial milk yield of the animals was compared with that of daily percent increase in the milk yield throughout the course of study.

The milk production was also enhanced in the treated animals. In goats, anthelmintic treatment has been found to induce a 4-8% increase in milk production. In another research ivermectin, a most commonly used anthelmintic has also been found to increase the growth rate of bulls. Moroever, ivermectin produced additional 0.94 L milk per day compared with untreated control cows.

This increase in weight gain may be attributed to decrease stress and better fodder consumption of animals. In parasitic burden, the animal does not utilize the full energy from the ingested fodder as the parasites take their share from that ingested food. Secondly, they penetrate themselves through their specialized organs (suckers, hooks etc.) into the layers of intestine to suck blood.

This leads to anemic condition of the animal. In chronic cases, the animal becomes lethargic and too weak to graze properly. This decreased intake of food leads to decreased energy uptake and decreased efficiency in terms of milk production or body weight (meat production).

In our country, the economic losses due to worm infestation are very high, although no exact figure is available but it is fact that millions of rupees are lost every year due to milk reduction, rejection of meat, edible offals, depreciation of wool, skin hides, delayed age at maturity due to slow growth rate, death of animals particularly in younger ones and high production cost due to the use of drugs. It is routine practice throughout the world to control worm infestation, maintain the health status and production improvement of the animal through deworming (a management tool). A very little/no information is available regarding efficacy of various dewormers/ anthelmintics under local condition and impact of deworming on growth rate and milk yield in dairy animals.