New pastures improve stock health

Date: 2009-02-01 | Category: Resources

Pasture renewal can have a significant impact on animal health, a high priority for farmers who ranked it most important after pasture quality.

A new pasture can change the endophyte status, reduce facial eczema, be chosen to alter internal parasite dynamics or have an impact on sheep fertility.  Trace element and macro nutrient supply may also be altered.

Ryegrass Endophyte

Ryegrass endophyte research was reviewed in the 1999 Grassland Research and Practice Series volume 7 and provided a comprehensive insight into the range of endophyte related issues on New Zealand farms.

Production in dairy herds was reduced by 6-23% and only in some seasons, depending on environmental conditions.  This did not account for losses that may be related to the inability of cows to be milked due to ryegrass staggers.

The impact of ryegrass endophyte in sheep farming also covers a range, depending on environment. In spring the liveweight gain of hoggets has been decreased by up to 35%, and in summer and autumn by up to 95%.  A delay in lambing date has also been reported, though no other impacts on sheep reproduction have been measured.

Research into beef production has produced results ranging from no response in the Manawatu to a 21% decline in the growth rate of yearling heifers and weaner bulls in Northland.

This indicates the importance of environment on the impacts of wild-type endophytes as more negative effects are measured when temperature and humidity increase.

The response of Red deer to endophyte has seen little research.

Elk and Wapiti types are susceptible to staggers, while Red deer are more tolerant. No difference in liveweight gain was detected in Red deer grazing either endophyte-free or high endophyte ryegrass in Otago.

In an attempt to quantify the impacts of ryegrass staggers it is suggested that significant costs would be incurred as a result of stock deaths which may increase by 2-10%, supplementary feeding to help alleviate the symptoms and lower liveweight gain in lambs. Extra labour may also be needed to monitor flock health and feed out.

Since the publication of the Grassland Research and Practice volume 7 major advances in the types of endophyte available have been made. These include the commercialisation of AR1, NEA2 and AR37.

Sheep production on pastures with AR1 endophyte has been intensively studied.

No significant differences in sheep growth rates, lambing percentages and dag burdens have been recorded between ryegrass with AR1 or with no endophyte. Both AR1 and nil endophyte ryegrass produced higher lamb growth rates and lower dag scores than wild type endophyte.

Cows grazing AR1 infected ryegrass pasture produced an extra 26kg MS/cow or 74kg MS/ha and it is suggested this is related to improved utilisation of the AR1 ryegrass.

The new novel endophytes, AR1 and AR37, were compared with wild type endophytes. Cows grazed on ryegrass infected with wild-type endophytes produced 20% less milksolids (1kg MS/day) compared to the new endophyte pastures (1.2kg MS/day).

In an indoor trial during summer, cows fed AR1 produced 12% more milksolids than those fed AR37 and 17% more than those fed pastures with wild-type endophyte. In autumn, cows fed ryegrass with new endophytes had similar milk production to those fed ryegrass without endophyte.

Facial eczema

Maintaining high grazing residuals is seen as the key tool for controlling facial eczema associated with the build up the mycotoxins produced by saprophytic fungi growing in ryegrass pastures.

Other strategies suggested include grazing animals on alternative forages or crops in high risk periods.  This argument can support pasture renewal practises that include alternative species to ryegrass or improved cultivars.

Internal parasites

Research has suggested that some pasture species may have anthelmintic properties or influence nematode larval dynamics on pasture.

Further research has investigated the true roles of pasture species in internal parasite management in more depth. One trial found that only chicory fed lambs had regularly lower faecal egg outputs than other pasture species.

Some suppressive influence of plantain and legumes were evident though not always present.  Adult burdens were only suppressed by chicory diets.

Both faecal egg output and adult worm burdens are generally higher for grasses than legumes, while some herbs have some effects.

Low dags are not a good indicator as Lotus tends to support high adult numbers and larval output but low dags and good animal performance.  There are some differences between grasses, though larval challenge is always relatively high.

Some research points to variations in parasite effects between pasture species.

The liveweight gain, wool growth and faecal egg count was evaluated for ewe lambs grazing on a range of herbages with and without condensed tannins over a six week period.

The pasture species compared were Maku lotus, Lotus corniculatus, sulla, plantain, lucerne and ryegrass/white clover.

Drenched lambs grazing lucerne had the highest liveweight gain (243g/day) and lambs grazed on plantain had the lowest liveweight gain at 51g/day.  The lamb growth rates were lower for the un-drenched animals ranging from those grazed on sulla (175g/day) down to a loss of 2g/day for the animals grazing on plantain.

Wool growth followed similar patterns and the faecal egg counts were lowest on animals grazing sulla and highest on those grazing Maku lotus. High production levels in lambs with high worm burdens grazing sulla and Maku indicates these herbages could be used to reduce the use of anthelmintic drenches.

In another trial five forage species (Lotus corniculatus, Lotus pedunculatus, Hedysarum coronarium, Onobrychis viciifolia and Dorycnium rectum) containing high levels of condensed tannins significantly improved animal production and reduced the dependence on anthelmintic drenches.

Parasite burdens and lamb growth was also evaluated on ryegrass swards compared to other swards including browntop, Yorkshire fog and tall fescue.

Lambs grew best on the ryegrass sward, followed by those on Yorkshire fog, then browntop and growth weights were poorest on the tall fescue swards.

Published courtesy of Country-Wide - May 2008. An edited extract from AgResearch's Literature Review.

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