Young sheep - Increasing resistance
Feed extra protein 
Susceptibility of young sheep to worm infections is a major constraint to sheep production. Young sheep, especially Merinos, are most susceptible to worms between weaning and one year of age.

In young worm-infected sheep protein is diverted from muscle and wool growth to fighting the worm infection and repairing the damaged intestines.

Young animals often can't get enough protein from pasture, especially low quality pasture. It is even more difficult for them to get enough protein from pasture when they have worms.

Research has shown that supplementary feeding of young sheep with a bypass protein and high quality pastures can increase their resistance to worm infection. Examples of bypass protein supplements are cottonseed meal, canola meal and copra meal. Examples of high quality pasture are those that contain, as a percentage of herbage mass, 20-30% legume and are growing on fertile soils. Contact a professional advisor for appropriate supplements in your area.

Young sheep - increasing resilience 
Improved protein and energy nutrition can increase production in worm-infected animals. If the nutritional demands of infection (i.e. direct loss of nutrients such as blood sucking with barbers pole worm and indirect losses associated with the immune response to the worm) are met, then additional nutrients will be used for muscle and wool growth.

Improved protein nutrition can be supplied by supplements, such as cottonseed, canola or copra meal. Improved energy nutrition can be supplied by grains like oats, barley, maize or lupins. Providing high quality pastures for animals to graze will increase both protein and energy nutrition. Contact a professional advisor for appropriate supplements in your area.

In this section:

• Research trial results

 Research trial results from feeding young sheep

Using nutrition to increase the resilience to worm infection of young sheep
Several researchers have demonstrated how improved nutrition can increase production in worm-infected animals.

1. Young worm-infected sheep that were fed extra protein had the same live weight gains of other young sheep that were not infected sheep with worms. Researchers in New Zealand (Bown et al. 1991) supplemented young sheep with either protein or energy, and then infected them with black scour worms. Other sheep were not given extra protein and energy, but were also infected with worms.
Live weight gain was increased most by protein supplementation. Protein supplementation increased live weight gain by a factor of 2.3 over non-supplemented, worm-infected sheep. In addition, live weight gain of the protein-supplemented, worm-infected sheep did not differ from that of the uninfected sheep. Energy supplementation also increased live weight gain of infected sheep, but to a lesser degree (increased by a factor of 1.2 over non-supplemented, worm-infected sheep).

2. A 20% increase in the energy content of the diet of young sheep with worms led to a doubling of growth rate over a ten week period.

Work conducted at the University of New England (Kahn et al. 2000) with recently weaned Merino sheep infected with black scour worm has demonstrated that a 20% increase in the energy content of the sheep's diet led to a doubling of growth rate over a 10 week period. In the same experiment, a 60% increase in the protein content of the diet resulted in a 50% increase in growth rate.

3. Supplementation with protein or energy resulted in the same increase in live weight gain as that achieved by drenching.

The effectiveness of energy and protein supplementation on increasing the resilience of grazing sheep to worm infection has also been investigated (van Houtert et al. 1996). Young Merino sheep grazing drought-affected pasture were fed a supplement of either a 50:50 mixture of fishmeal and lucerne chaff (100 g/day), a 67:33 mixture of sunflower meal and lucerne chaff (150 g/day) or whole oats (150 g/day) (Table 1).

Table 1. Supplement type, amount of supplement fed and daily supply of metabolisable energy, crude protein and bypass protein from the supplement.

Some sheep received no supplements, and were either drenched or left undrenched. Worm infections consisted of barber's pole worm (67%) and black scour worm (33%). All of the supplements increased weight gain compared to that of the non-supplemented, undrenched animals. There were no differences between the three supplements. Importantly, supplementation with energy or protein resulted in the same increase in live weight gain achieved by drenching.

Figure 1: Live weight gain of Merino sheep over 14 weeks when either undrenched and fed one of a variety of supplements or drenched and not fed any supplements.
Source: van Houtert et al. (1996).

4. When young sheep grazed on high quality pasture, there were no differences in live weight gains between those sheep that had many black scour worms and those that had none.

Live weight gains of young Merino sheep grazing a high quality pasture (11 MJ ME/kg DM; 20% crude protein; 40% white clover) and given either an anthelmintic capsule or 15,000 black scour worm larvae were compared. Over the 10 weeks of the experiment the weight gains of the animals given either the capsule or the worm larvae were the same. Faecal egg counts during the 10 week period were 0 epg for animals given the capsules and reached 800 epg for the worm-infected animals.

Figure 2: Live weight gain of Merino sheep (6-7 months of age) grazing high quality white clover based pasture and given an anthelmintic capsule on day 0 or 15,000 black scour worm larvae on day 7. Source: Kahn et al. (2001).