Research indicates that top-quality rations will lead to improved libido, sperm production in boars.
When almost all boars were used in natural service breeding programs, most pork producers followed standard industry logic when it came to boar nutrition: feed them the gestation sow diet and that will be good enough.
"If semen quantity of a boar in natural service drops from 90 billion cells per ejaculate to 50 billion cells, this is still adequate to get the sow bred," observes Mark Wilson, swine nutritionist with United Feeds of Gridley, IL
A Different Time That drop in semen production becomes unacceptable in today's world of boar studs and mating by artificial insemination (AI), where each dose of semen has financial value.
Wilson says while much of the research on boar nutrition has been inconclusive, some is starting to show that feeding boars better probably pays off.
Following are the key areas of importance to top stud performance and what data shows:
Libido: A few trials showed that libido was not influenced by nutrition, including that ad lib-fed boars didn't increase semen production over moderate-fed boars.
Wilson reported that one confounding factor is that not all genotypes respond the same. Therefore, caution should be used when comparing feeding requirements of traditional and current lean genotypes.
He reported on a study of two genetic lines of Pig Improvement Company boars. Each line had two feeding regimens: one group that was limit fed and one that was fed at a high level of nutrition. The line of boars that showed significant response to higher feeding levels also gained the most body weight. The line which did not see a response showed no weight gain differences regardless of low or high feeding levels.
In more recent trials, restricting protein intake (.31% lysine) reduced boar libido, which was measured by increased time for mounting and start of ejaculation and shortened length of ejaculation time, says Wilson.
Also, he warns, producers may want to rethink scrimping on heat check boar rations. Those cheaper rations may harm libido, and in turn, reduce their ability to detect females in heat.
Overall, most producers feed boars properly, believes Wilson. But these days of low returns they might be thinking about cutting corners. He says to rethink that idea. Higher levels of protein may add $2-3/head, but that still works out to pennies per dose of semen.
"High protein diets tend to produce boars that create higher levels of estrogen in the bloodstream and those boars have been shown to mount quicker and were much quicker to collect," he says.
Sperm production: In a trial done in a cold climate, boars were given from 18 grams to 31 grams of lysine in their diet. The high-energy-fed boars were given 12 lb. of feed, the medium-energy group 8.5 lb. and the low-lysine group got 4.5 lb. of feed a day, reports Wilson. Using the same collection frequencies for the three groups, there were no differences in weekly sperm production out to six weeks. But when the study was extended out to 9 to 12 weeks, there were major differences in sperm output in favor of the high-energy group.
In a related trial done at United Feeds, all the boars responded positively in sperm production when lysine levels were increased from 14 grams to 18 grams per day, he says.
According to Wilson, using the high-protein diet from the previous United Feeds trial, researchers added a top-dress product containing some fiber. The result was an increase in sperm production in just two weeks. He says the top-dress changed the formulation of the ration such that the extra energy produced a change in hormonal expression of those boars and an increase in libido. "Boars were mounting the dummy much faster and we were getting longer collection times."
He theorizes that the boars were probably already producing the sperm. "By top-dressing the ration, we just got them to produce a better collection."
Daily energy requirements for adult working boars are listed in Table 1. Wilson says you need to feed boars liberally. His data shows boars gaining weight produce the greatest amount of sperm. Don't scrimp on boar nutrition as they get older. Boars need to maintain body condition without getting too fat.
Average crude protein for boars should range 14-16%. Lysine should range .55%-1.1%. Energy levels depend on the grain source but run from upper 22 Mcal/kg to the lower 3 Mcal/kg. Fiber content should be about 4.5% of the diet.
Wilson says most boar studs use the following micro-ingredient levels: calcium, .9%; phosphorous, .8% and zinc, 100 ppm.