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Feed Requirements Vary During Sow Lactation

Bernie Peet is president of Pork Chain Consulting Ltd. of Lacombe, Alberta, and editor of Western Hog Journal. His columns will run every second week in the Manitoba Co-operator.

Current nutritional recommendations for gestating sows are out of date because today’s genotypes are so much leaner and more productive, says Dr. Ron Ball at the University of Alberta.

Ball says the nutrient requirements of modern sows, and the availability of dietary nutrients for sows, are very poorly known in comparison to our knowledge of growing pigs. The research on which current dietary recommendations are based on is from data from the late 1970s to the early 1990s. Recent work by Ball and his team shows that the current recommendations for both energy and amino acid intake in sows are incorrect by a significant margin. New feeding programs, which use separate diets for early and late gestation, have the potential to save up to $5 per sow per gestation, with the likelihood that sow productivity and longevity will be enhanced, he says.

“Current recommendations for nutrient and energy intake, such as those provided by the U. S. National Research Council (NRC) involve feeding the same amount throughout gestation,” says Ball. “However, practical experience has shown that feed and nutrient intake must be increased during late gestation to maintain performance and sow longevity. Increasing nutrient intake in late gestation allows sows to maintain and improve their body condition prior to farrowing, while meeting the needs of the growing fetuses.”


Applying a single-phase feeding program will lead to overfeeding during early gestation and underfeeding during late gestation, Ball stresses. Overfeeding in early gestation results in a waste of feed and money, while underfeeding in late gestation leads to sows entering lactation in a catabolic state.

Ball’s team has been at the forefront of investigations to better understand the amino acid requirements at different stages of gestation, an area about which there is very little knowledge due to the difficulty of measuring amino acid utilization and excretion in animals. They have pioneered new and faster measurement methods, which have increased our knowledge of this area considerably.

“We have recently measured maintenance lysine requirement of sows,” says Ball. “The dietary lysine requirement was calculated to be 49 mg per kilo of metabolic body weight, which exceeds the current NRC recommendation by 30 per cent.”

Recent German recommendations suggest that amino acid requirements in late gestation are greater than in early gestation, he notes. “They proposed a change of diets on day 85 of gestation to accommodate the greater amino acid requirement caused by increased fetal growth.”

The U of A researchers also made estimates of threonine requirements for early, mid and late gestation. “These were similar for early and mid-gestation to the German figures but markedly lower than NRC recommendations,” Ball says. “However, the threonine intake requirement in late gestation is more than double that required during early gestation, and considerably exceeds the recommendation of both NRC and the German researchers.”

He also notes there is a large degree of uncertainty concerning the magnitude of amino acid requirements and the optimal ratios among the amino acids.

Another factor is that the digestibility values for amino acids in commonly used feed ingredients are significantly higher for sows than those for grow-finish pigs, which are the values generally used for diet formulation.

“Using the correct digestibility values for gestating sows will lead to cheaper gestation diets and must be known to accurately formulate diets using our new requirement values, says Ball. “For example, if the amino acid digestibility of common ingredients is about five per cent greater for sows than for growing-finishing pigs this would reduce diet cost by approximately $1/tonne.”

Similar to amino acids, energy requirement during gestation can be expected to increase as pregnancy progresses, predominantly because of the exponential growth of fetuses during late gestation.


Recent work at the U of A shows that NRC recommendations result in overfeeding energy in early gestation and underfeeding in late gestation, which agrees with results from the German research. Following the NRC scale also uses more feed overall and incurs more cost.

“Feeding according to NRC results in the excess nutrient intake being deposited as body fat and protein, and then mobilized in late gestation when energy and protein intake is insufficient, which is energetically inefficient,” Ball explains. “Feeding sows according to their changing energy needs in gestation can save at least 20 kg of feed per sow per gestation.” More accurate estimation of the Net Energy (NE) in feedstuffs and complete diets for sows can also result in reduced costs, says Ball. “Better NE data will allow more accurate formulation according to the sow’s needs. In gestation this will lead to a reduction in feed allowance of two per cent amounting to approximately five kg during gestation, or $1.25 per sow at a cost of $250/tonne.

A revised feeding program for gestating sows, which achieves a lower energy and lower protein intake for early gestation (day 1 to 84) and uses a higher-energy and higher-protein diet for late gestation (day 85 to 112) will result in major savings on feed costs, Ball says.

“Phase feeding with two diets can be expected to save as much as $5 per sow per gestation or $12.50 per sow per year. Even where it is not practically possible to feed two different diets, phase feeding with a single diet and feeding less in early/mid-gestation may still save $2 to $3 compared to feeding according to the NRC recommendations.”



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