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Stock Alert 14th April 2011

Osteragia Outbreaks in 1st Calving Heifers

We have recently been alerted to a number of cases of mobs of autumn calving 1st calf heifers breaking down with severe and sudden loss of condition and profuse watery scour. Coming up to calving these heifers were generally in very good condition.

These cases are most likely to be cases of what is known as Type II Ostertagiosis.

Type II Ostertagiosis is caused by the small brown stomach worm Ostertagia sp.

It occurs when the worm larvae that are picked up over last spring, summer or early autumn don’t develop on to the adult stage immediately, but rather burrow into the wall of the 4th stomach (abomasum) and hibernate. The trigger that makes them hibernate is very complex and not fully understood however it seems that the conditions of late 2010 and early 2011 have encouraged Ostertagia larvae to burrow and hibernate.

These hibernating worm larvae (often called inhibited larvae) can then in periods of stress (calving and early post calving period of a 1st calving heifer) emerge en mass to develop further causing severe damage to the stomach lining. This damage leads to often severe fluid and protein loss in the animal. Loss of condition, bottle jaw and brown/green watery scour (“breakdown\”) is generally the result.

Generally these cases have occurred when the Producer has not drenched their heifers prior to calving as they have been looking a picture of health and enjoying good pasture conditions. In many cases however there has been a ‘time-bomb’ ticking away waiting for a stress trigger to set it off.

If the condition has occurred on your property then drench ASAP with a ML drench such as Vetmec Injection or Pour-on. Separate the worse affected heifers and their calves into a hospital group and supplement with good quality hay/silage and consider re-drenching 3-4 weeks after the initial drenching treatment.

To prevent this condition occurring susceptible cattle must be effectively drenched prior to calving.

If you are still coming up to calving then it would pay to act now and drench your 1st (and maybe your 2nd ) calving heifers or if you are a spring calver then remember, even though we have had a very good season and the cattle are looking in good order, to drench prior to calving with an effective drench.

If you have already calved and didn’t drench your heifers prior to calving then a drench now or at marking could be definitely warranted.

This condition is not restricted to this class of stock although they are the most commonly affected. I’ve seen the condition in old cows on their 6th and 7th calf. These real old cows seem to be just as prone as the young cattle to this condition. The condition can also be triggered in mobs of dry steers or heifers by periods of stress.

Chemvet Australia Pty Ltd
1/8 Rocklea Drive
Port Melbourne, Vic, 3207 

T 1800 243 683