Prolific worm-resistant meat sheep for Maharashtra, India

• National Chemical Laboratory, India
• University of Melbourne, Australia
• CSIRO Livestock Industries, Australia
• Nimbkar Agricultural Research Institute, India

Indian sheep in general have low fertility and, in 12 of the 15 agroclimatic regions of the country, their growth is limited by parasitic worms. The supply of sheep meat and skins cannot meet the national demand, and the cost of meat rises annually, while the shepherd families that farm the sheep live in poverty. Breeding programs that result in more lambs per ewe could vastly increase meat production in India, particularly if the offspring's resistance to diseases and parasites was strengthened too.

Parasitic worms interfere with a sheep's wool and meat growth, and make the animal weak, susceptible to other diseases and liable to die. For many years, farmers in Australia have dosed their sheep regularly with anthelmintic drugs to combat the helminth worms, but the worms are becoming immune and customers are beginning to object to chemicals in food and wool. Indian farmers cannot generally buy the expensive drugs.

The sheep initially selected for this project were the Deccani, Bannur and Garole breeds. Deccani sheep, a coarse-woolled meat breed, are the most common in Maharashtra. Bannur sheep produce hair and are considered to have a good body conformation for meat production. They yield more mutton per weight of carcass than other Indian meat sheep, while also being one of the better indigenous breeds.

Garole sheep come from the hot, humid, swampy Ganges delta and appear able to graze standing in water without getting footrot. These small sheep are the most prolific of the Indian breeds andmay have contributed some ancestry to the Booroola Merino, whose first-cross ewes produce twice as many lambs per ewe mated as other Merino strains in Australia.

In the early stages of the project the Awassi breed, a fat-tailed sheep raised for meat, milk, and wool in the various countries of the Middle East, was also added to the breeding program.

To evaluate the efficiency of lamb production and parasite resistance of the Deccani and Bannur breeds, their reciprocal crosses and their crosses with the Garole and Awassi breeds with a view to subsequent development of a suitable composite meat sheep breed for Maharashtra. In Australia the scientists sought answers to the problem of worm resistance to anthelmintic medication

The project scientists undertook a crossbreeding program, selecting for higher lambing percentages and increased resistance to disease and internal parasite infestations. Productivity was measured as the weight of lamb produced per weight of ewe, and the concentrations of worm eggs in the lambs' faeces provided a measure of worm infestation. Until then, almost no systematic trials had studied the various breeds' resistance to gastrointestinal nematodes, but this project postulated that genetic differences in disease resistance between and within Indian sheep breeds could be exploited to make production more efficient.
Apart from the main cross-breeding program, Garole x Deccani rams were mated with Deccani ewes in a separate trial to test for a single gene for prolificacy. That study also attempted to ascertain if the Garole was indeed an ancestor of the Booroola Merino.
In Australia meanwhile, field experiments measured how time of weaning affected the count of parasitic worm eggs in the faeces of sheep selected locally for their worm resistance. Similar counts monitored the effects of supplementary feeding to lambs and young adult sheep, and of moving the sheep to different grazing areas. A detailed study was made in the animal house to see how tanniferous feeds, such as Gliricidia and other leguminous browse shrubs, affected a sheep's output of faeces and worm eggs. Such trials helped determine whether faecal egg count could to be used by breeders as a standard measure of resistance to gastrointestinal parasites.

The outcomes of this project have the potential to significantly alter sheep production in India. The breeding program yielded much useful information about the comparable reproductive performance and gastrointestinal nematode (GIN) resistance of Deccani, Bannur, Awassi and Garole breeds. The scientists also detected superior genetic resistance to GIN infection in Garole crossbreeds.
New protocols and tests enabled quick and accurate identification of sheep carrying the prolificacy gene, using blood samples collected on FTA filter paper. The scientists determined the genetic basis of the prolificacy in Garole sheep and concluded that the gene was highly likely the same as that which led to high prolificacy in the Booroola Merino in Australia. Tests also indicated that the gene could be introduced into other breeds to increase prolificacy.
A study of four shepherds' flocks revealed significant subclinical production losses from uncontrolled GIN infection in Deccani sheep in semi-arid Maharashtra state. A hallmark of the project was the high degree of trust gained from the shepherds. This extended to the introduction into their flocks of rams carrying the prolificacy gene, where previously they had opposed introduction of any new breeds. Audio visual materials have been developed as teaching aids to extend the work among the shepherds.
In Australia a great deal was learnt about the relationship in Merino sheep between GIN, diet and dietary supplements. The scientists found that pastures enriched with legumes did not increase the resistance or resilience to infection to GIN in young sheep. They also learnt valuable information about the effect of drenching and nutritional supplementation on gaining repeatable egg counts from the sheep under study for worm resistance.
The project studies contributed considerable capacity building and at least four related research projects have now commenced. One of these is a large project to develop gene markers for worm resistance in sheep, to be undertaken by the University of New England in collaboration with the University of Melbourne, with funding from Australian Wool Innovation Pty Ltd. A second ACIAR project was also developed to consolidate, extend and take to fruition the findings of this project.