As sows have been selected for greater milk production and productivity levels have been improved in commercial units, both milk production and litter weaning weights have increased substantially, says Casey Neill, a nutritionist with PIC North America. With increased potential for milk production, management and nutritional factors must be changed to meet these demands for lactation, he told delegates at the London Swine Conference held March 31 and April 1.
“Sows can produce more milk per kg of body weight than cows,” he points out. “If a 182-kg sow produces 11 kg of milk/day that would be 0.06 kg of milk per kg of body weight. A 909-kg cow can produce 45.5 kg of milk/day that would be 0.05 kg of milk per kg of body weight.”
A wide range of environmental and management factors influences lactation feed intake, but nutrient level of the diet is the most critical, especially energy and amino acids, Neill says. In particular, gilts have a much higher dietary lysine requirement due to their lower feed intake. Recent studies in the U.S. have demonstrated that the total lysine requirement in the diet for gilts is around 1.25 per cent. This reduces to 1.05 per cent for second-parity sows and 0.85 per cent for third-parity sows due to their higher feed intakes.
“Total lysine intakes of 70 g/ day or 62 grams of SID lysine/ day optimize reproductive and milk production performance in PIC sows,” says Neill. “Because gilts eat 10 to 15 per cent less than sows the per cent SID lysine in the lactation diet must increase compared to a mature sow herd. Because we target 62 grams of SID lysine/day we must formulate based on feed intake and not only per cent SID lysine,” he adds. Trials show that as dietary lysine percentage increases from 0.83 per cent up to 1.2 per cent, piglet growth rate during the suckling period increases from 262 to 288 grams/day.
Nutrient intake in the first lactation has a huge impact on subsequent productivity. “If the gilt loses more than 10 per cent of her body weight, then performance in the subsequent parity will suffer,” Neill stresses. The results in Table 1 show that as weight loss increases, weaning to estrus interval, the percentage of sows bred by seven days after weaning and total born in the subsequent litter are impacted significantly.
In addition to lysine requirements, the maximum amount of synthetic lysine in lactation diets and the ideal ratios of other amino acids have also recently been validated, Neill notes. The use of synthetic amino acids leads to improved performance but lowers diet cost. “These studies indicate that up to 0.30 per cent synthetic lysine can be added to gilt diets without deleteriously affecting reproductive or milk production performance,” he says. “This response has also been validated in older-parity sows.”
In addition to amino acid intake, proper energy intake is essential for maximizing milk production in sows. Both the amount of and type of energy can influence milk production. “Recently in the United States, various forms of self feeders have been evaluated in order to maximize feed intake, Neill points out. “Commercial field research has demonstrated an improvement of seven per cent in feed intake compared with hand-feeding systems, along with less labour required for feeding.”
“In addition to evaluation of self-feeders, we have evaluated optimum feeding pattern for maximizing lactation intake in commercial systems,” he says. “Based on these data, the recommendation for feeding PIC sows is to scale feed at 1.8, 1.8, and 2.7 kg for days zero, one, and two respectively of lactation followed by ad-libitum access to feed.”
Mild restriction for three days followed by full feeding from day four through the end of lactation resulted in increased feed intake and reduced body weight loss.
Adding fat to lactation diets is another route to increasing energy intake, however results of recent trials are somewhat inconclusive. “A trial carried out in Oklahoma during the months of July to September compared added fat levels of zero, two, four, and six per cent,” Neill explains. “The researchers reported that when caloric intake was increased there were no beneficial effects on any measured criteria, except for improved litter gain in parity-three-plus sows.”
“Another internal research trial was conducted with 1,020 PIC gilts and sows with two treatment levels of zero and five per cent added fat,” Neill says. “The weaning weight from pigs that nursed from gilts and sows fed five per cent added fat were 0.18 kg heavier. However the difference in weight was not maintained at 22 weeks after weaning. Also, there were no differences in sow performance reported.”
The modern sow has a tremendous capacity for milk production given proper nutrition and feeding management, Neill concludes. “Milk production levels of over 11 kg/day can be achieved in commercial situations,” he notes. But, to achieve these levels, specific requirements for lysine and energy intake must be achieved.