Changing lambing time reduces parasite burden for sheep meat production enterprises

The control of diseases in livestock is important for maximising animal welfare outcomes, ensuring the incomes of livestock producers and minimising the environmental impact of livestock production. Gastro-intestinal nematode (GIN) parasites are ubiquitous globally and infect domestic animals, causing disease, deaths and production loss. Haemonchus contortus is a particularly pathogenic GIN causing widespread disease in sheep and goats. We characterised the seasonality of GIN parasites in two northern districts of the Australian state of New South Wales using data from government and commercial diagnostics laboratories. The results suggested that in these regions, parasitism with Haemonchus contortus could be reduced by changing lambing time from spring (August/September) to autumn (May/June). We conducted a sheep grazing trial over three consecutive production cycles contrasting two lambing seasons and two grazing feed regimes. Results show that changing lambing time from spring to autumn did result in a significant decrease in parasitism for autumn-born lambs relative to spring-born lambs and reduced the number of treatments needed for lambs from 3.4 to 1.0 applications per year. We analysed a comprehensive set of other animal health and animal production data to see whether the change to autumn lambing was accompanied by other important changes in the production system. Most animal health and animal production data indicated little difference between autumn and spring lambing systems. The number of lambs conceived, born and raised in the autumn lambing system exceeded the numbers from the spring lambing system. However, feed provision limitations were observed with the autumn lambing system and higher neonatal death rates were observed in autumn-born lambs. We conclude that autumn lambing systems in summer rainfall areas can be as productive as spring lambing systems, and that the benefit for GIN parasitism will make the change worthwhile, especially with higher levels of anthelmintic resistance. However, future attention to feed provision and neonatal lamb mortality in the autumn lambing system will enable a still more profitable outcome.