Health Highlight 14 December 2013
INTER is the time of year when farms have most problems from
both rats and mice. It’s logical if youthink about it really,the weather is colder so theymove indoors to anice warm shed with aready supply of feed –in other words afarm feed store will do nicely! While rodent infestations have traditionallybeen controlled only when they reachtroublesome lev- els,today’s farmassurance require- mentsmakeeffective and verifiable rodent control essential on ayear- round basis in order to avoid the rodents spreading disease,eating and contaminating feed, as well as causing serious damage to the buildings.
THE species most commonlyfound in Europe is known as the Norway rat(Rattus norvegicus).Aless com- monlyfound species,the blackor roof rat, (Rattus rattus), is largely restricted to port areas,but they both live alongside man, invading his buildings and eating his food. Importantlyratstransmit diseases whichare potentiallyfatal to man, suchasWeil’s disease and murine typhus. Damage by rats to the fabric of
buildings can be costly. Fires can easilybestarted after arat has gnawed acable. Gas and water pipes are also at risk and ratbur- rowing can undermine foundations
Sally Harmer, animal health manager for Clynderwen and Cardiganshire Farmers (CCF) highlights seasonal health management issues and solutions in the cattle and sheep sectors.
Sally Harmer Animal health manager
and damage water courses. Physicallyvery strong, rats have
been known to survive fortwo days in open water,toswim amile in open sea and to get through agap of less than 25mm.
MICEcarry diseases suchassalmo- nella and can transmit atype of Leptospirosis,but not Weil’s dis- ease.Th
eir continual dribbleof urine contaminates food and feed- stuffs.Th
ey are aparticular prob- lem in poultry units and pig hous- ing, and avery real pest in grain stores,warehouses and domestic premises. Because mice can reachsexual
maturity 42 days after birth, popu- lations grow muchfaster than those of rats,whichtake about twice the time to reachmaturity. The difficulty of preventing
access,coupled with rapid popula- tion growth and natural dispersal of mice,means thatalarge building maycontain anumber of colonies, eachofwhichmust be treated as a separate infestation and control needs to be tackled systematically.
WITH food safety in mind, the need to guard against contamination is placing growing constraints on how and where rodenticides can be used, shifting the emphasis to bait- ing outside buildings and better environmentalmanagement to pre- vent infestations. Repopulation
TAKE YOUR PICK: Farmers should choose the right time to control rat infestations to achieve the best results.
The best modern strategy territories
cleared of rats and mice by treat- mentprogrammesmakesfarmcon- trol acontinuous challenge and ‘fire brigade’ treatment is insuffi- cient to achieve the level of control required today.
involves an annual cycleoftreat- ments at key times of the yearwhen rodents are most vulnerableand the system permits the safest con- trol. The best time to use rodenti- cides is when there is the least amount of alternative food avail- able, so it makes sense thattreat- ment times are designed to fitwith the farm’s particular annual pro- duction cycle–between batches of stockoraround key seasonal changes,for instance. Because rats thrive best in stable
environments and become especial- ly wary to change,control will gen- erallybebetter when undertaken ahead of, rather than during or immediatelyafter major changes.
Typical signs of ratactivity Holes or burrows in rough
ground, earth banks and unmade floors
Well-worn runs along the sides of
buildings with smear marks and hairs Droppings at feeding sites,
around burrows and along ratruns Gnawing and chewing damage to
materials and buildings Foot prints in soft surfaces and
tail swipes in stored grain Acharacteristic smell in
Good bait management While baiting in external bur-
rowshas been found to give the best ratcontrol, it can present greater risks to other wildlife. Wherever possible,secure bait-
ing containers sited between bur- rows and nests and the main sources of food are preferable. Forthe greatest success the bait
LOCATION IS KEY: This diagram shows good areas to lay down bait on atypical mixed farm.
should be presented as close to the burrowand as distant fromalterna- tive food sources as possible. With rats,baiting containers should always be placed along well-
travelled runs. Sites thatthe rats consider safe
should be chosen –alongside walls, in recesses,atthe edges of hayor strawstacks,and in undergrowth (see diagram, left). The precise location of baiting
points is farless important with mice,the key to control being asuf- ficient number in the general area of activity. Plenty of baiting points is vital to
ensure as manyrodents as possible are abletoconsume alethal dose of bait as rapidlyaspossible. Failure to replenish bait often enough is acommon reason for poor rodent control. This and the removalofbaits
before acomplete cessation of rodent activity all too often pre- vents the entire population from consuming alethal dose. Baiting points should, ideally, be
checked and topped-up wherever necessary every three to four days - or six or seven times during atypi- cal three to four week programme. Don’t forget to record baiting
activity in the record book. In summary,toachieve the best
and safest control of rats and mice on farm:
Appreciate the increasing chal-
lenge posed by the competing pres- sures of safety and growing behav- ioural resistance. Understand the key elements of
natural rodent behaviour thatcan best be exploited to ensure the most rapid, complete and reliablecon- trol.
Plan and implement regular,
integrated control programmes based around effective rodenticide baiting in sufficient, well-located and secure containers. Take full advantage of modern
bait technology to significantly increase the speed and reliability of rodenticide consumption. Thanks to BASF forproviding
someof the information used in this article.
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