Optimizing the use of energy in pig feeds

With the cost of dietary energy more than doubling in the last eight years, it’s vitally important to optimize the efficiency with which it is utilized.

Meeting the energy specifications of a typical grower diet now represents about 85 per cent of the cost of the diet and over 50 per cent of the total costs of pig production, John Patience of Iowa State University said at the recent London Swine Conference in Ontario.

“One of the most critical questions revolves around the relationship between caloric density of the diet, daily caloric intake by the pig and pig growth rate — which in turn relates to barn throughput,” he said.

“Whereas in the past, barn throughput was closely linked with low feed cost and maximizing net income, with rising feed costs, maintaining barn throughput has become increasingly expensive.”

This means that, for some farms, growth rate must be reduced to increase net income.

Prior to 2005, formulating for energy in the diet was simpler because a limited range of energy sources was used. But today, a wider number of ingredients is used and the relative cost of the energy in those ingredients changes over time, making formulation more difficult. For example, in 2005, energy from fat cost about 60 per cent more than energy from corn — today that differential is only 36 per cent, he said.

“Energy from DDGS used to cost 41 per cent more than from corn, but today it is only 16 per cent more,” said Patience (see Table 1).

“These changing price relationships will influence how much of a given ingredient is likely to be used in a feeding program. This, in turn, will put pressure on the upper limits a nutritionist assigns to certain ingredients and can change purchasing practices, especially if forward booking is employed.”

The net impact of changing energy costs can be minimized by considering all aspects of pricing changes, including ingredient cost relationships, he said.

Maintenance cost is high

Maintenance is a very important aspect of energy utilization in the pig, but one that is often overlooked, Patience said.

About one-third of the energy that the pig eats goes to maintenance, 20 per cent is used in protein deposition and 46 per cent in fat gain, he noted.

“To maximize efficiency, we must reduce the energy spent for maintenance,” he said. “This can be done by optimizing thermal comfort, minimizing social stressors and maintaining the highest possible health standards because fighting disease uses up energy.”

Maximizing growth rate by various means reduces the time spent in the barn, which results in fewer days of maintenance energy costs, he said. Reducing maintenance energy costs increases the amount of energy that is directed towards lean gain.

The pigs’ energy intake impacts how comfortable they feel in the barn, said Patience.

“Unthrifty pigs eat less than their healthy contemporaries and, because of this, they are chilled at a temperature that is perfectly comfortable for healthy pigs,” he said.

“Therefore, unthrifty pigs need to be kept in warmer and less drafty conditions, for example by providing localized heating or covering their lying area.”

Every additional day that the pig is in the barn represents another day’s worth of maintenance, so this maintenance cost is very much under the control of the producer, he pointed out.

However, when feed costs are high, it may be financially advantageous to feed a less expensive diet and accept the associated slower growth because the overall cost of production is lower, he added.

“Certainly, in the traditional Corn Belt of the U.S., the trend to lower energy diets is very clear, and is one of the drivers for the construction of new grow-out facilities, he observes.

Individual farm response

It is important to know the response of pigs on an individual farm to changes in dietary energy density.

“Under most commercial conditions, lowering dietary energy concentration is likely to reduce daily energy intake and thus growth rate,” he said. “There are exceptions to this broad generalization. If your farm is one of these exceptions, you have much greater flexibility in adjusting dietary energy concentration than would otherwise be the case, because you have the option of feeding a lower-energy diet and maintaining growth rate.”

Individual farms or systems must develop their own feed intake curves that apply to their farm, and not depend on universal data obtained from some other remote, and possibly very different, location, he said.

Understanding daily energy intake is crucial to success, as it provides the foundational knowledge required to determine how the pig will respond to changes in diet cost and energy content, he said.

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