In every country where I work, pig producers are beset with new virulent diseases. I am not a veterinarian — just a pig management specialist. At least 80% of my work these days involves disease prevention.
I confer with many veterinarians specializing in pigs. They, too, are trying to stem the tidal wave of new diseases that threaten profits.
I am concerned we have become complacent about the beneficial effects of good, natural immunity, especially in the breeding herd. In our race to get expensive gilts into production, we may have forgotten that two vital factors have not kept pace with the swift bodily development that modern genetics and nutrition have given us.
We must remind ourselves of the underdeveloped hormonal readiness of a 275-290-lb. gilt, and we must recognize the underdeveloped immune status of such an animal.
By sheer size and appearance — because they grow so fast and look so fit — we expect these fully developed, modern gilts to have fully developed hormonal systems. Truth is, they do not.
In bodyweight terms, many producers have accepted the current advice not to mate these gilts until they have their second true estrus and have reached 275 lb.
Remind yourself just how fast the gilt can grow these days. Many easily reach 275 lb. by 200 days of age. These young breeding females, full of male genes (rather too many to my way of thinking, as I prefer very “female” females) for rapid flesh deposition, arrive at service insufficiently immune-primed to cope with many of the “new” viruses that are appearing.
I advise my clients to breed them heavier but also to slow them down between 200 lb. and 275 lb. This procedure bears fruit on virtually every problem farm.
These farms are mired in second litter (often third litter) reproductive disappointments. As a result, these young sows get culled and the replacement rate is in the upper 30% and often more than 40%.
So common is this problem globally that a 38% replacement rate is now considered “normal.” This is madness!
A herd that has to cull so many young sows can only count on about 50% natural protection against virus disease. However, one that can put an extra two litters on its average sow herd life is 80% protected (Figure 1). I find this does make a difference to longevity.
You have to give your gilt replacements time to acclimate properly. The latest advice is — three days total isolation, 14 days challenge period (consult your veterinarian for the farm-specific protocol) and then, remove all challenges for at least a five-week rest/fortification period. This could be six weeks for some of the viruses that may be around.
Therefore, in the future, you'd better allow eight weeks from selection to service, and if that means mating at the third estrus, so be it.
Any nutritionist who is up to speed can design a diet that grows a modern, high-performance, high-growth-rate gilt at no more than 1.43 lb./day. This will still give you a sexually mature gilt but with proper hormone balance and a decent immune status at 8 to 8.5 months of age. This will help her give you 60 or more pigs produced/lifetime instead of a miserable 40.
So things like junior gilt production, gilt pools, special gilt developer diets, batch production using gilt stimulation techniques and a watchful eye on things to encourage immunity from your veterinarian are some of the less frenetic ways to go.
Please stop fussing about the cost of all this delay and extra accommodation, feed and overhead. Sure it could cost more, but divide that extra cost/gilt by 20 more pigs sold/lifetime, and it comes back into perspective. Even eight more pigs make it a bargain. Do the sums and you'll see.
We've got to get back to thinking more about natural immunity. I'll have more to say on this in the future. It is too important to ignore.