Ewes - increasing resistance and resilience
Best results - feed extra protein
During late pregnancy and early lactation the resistance of adult ewes to worm infection is usually lost or reduced, resulting in a rise in faecal egg count around the time of lambing. As a result, worm eggs from ewes are a major source of worm infection for young lambs.

The loss of resistance occurs at the same time as nutrient requirements are increasing, particularly the need for extra protein for milk production.

If the increased protein demands of the ewe for milk production can be met by appropriate supplements, additional nutrients can be used in maintaining immunity to worms.

Protein supplementation has recently been shown to be highly effective at reducing the breakdown in resistance to worm infection and resulting contamination of pastures with worm larvae.

Resilience to infection in pregnant and lactating ewes can also be increased through improved nutrition. As with young sheep, both protein and energy supplementation have been shown to be beneficial.

In this section:

• Research trial results

 Research trial results from feeding ewes

Two research groups have recently demonstrated how improved nutrition can increase the resistance and resilience of ewes to worm infection.

1. Worm burdens of ewes fed high protein diet were reduced by 87%

Researchers in New Zealand have recently demonstrated the impact of protein supplementation on worm numbers in lactating ewes. Coopworth ewes infected with both black scour worm and  brown stomach worm were fed diets that provided different levels of energy and protein.

The low and high levels of metabolisable energy provided 10.7 and 13.2 MJ/day, respectively, during pregnancy, and 19.3 and 23.6 MJ/day during early lactation. The low and high levels of protein provided 94 and 110 g metabolisable protein/day, respectively, during pregnancy, and 170 and 200 g/day during early lactation. (Metabolisable protein is a scientific term that describes the supply of microbial and bypasses protein, adjusted downwards for the percentage absorption across the gut.)

Three weeks after lambing the worm burdens of ewes fed the high protein diet were reduced by 87%. The high energy diet did not result in reduced worm burdens.

Figure 1: Number of worms recovered from Coopworth ewes 3 weeks after lambing when fed diets to provide for low and high levels of energy and protein. Source: Donaldson et al. (1997).

In contrast, the high energy diet was more effective than the high protein diet at increasing live weight gain in the ewes. Increasing energy supply by 23% led to a 50% increase in live weight gain. Increasing protein supply by 17% led to only a 13% increase in live weight gain.

2. Supplementation of grazing ewes with cottonseed meal reduced mean faecal egg count by about 30%

Research conducted jointly by the University of New England and CSIRO (Kahn et al. 1999) over two years investigated the benefits of supplementing grazing ewes during late pregnancy or early lactation with cottonseed meal (250 g/day). Infections were a mixture of barber's pole worm (12%), brown stomach worm (10%), black scour worm (58%) and large bowel worm (20%).

Supplementary feeding prior to lambing was effective in both years, and feeding after lambing in one year. Averaged over the two years, supplementation reduced mean worm egg count by about 30% (from 600 epg to 430 epg).

Supplementation was also somewhat successful in increasing live weight gain. The weight gain was small, 1.5 kg for a 43 kg ewe after 6 weeks of supplementary feeding, and disappeared after when the feeding stopped.