Better Pork - June 2007

Nutrition

Field peas can replace soybean meal in growing pig diets

A U.S. experiment clearly indicates that field peas can take the place of soybean meal in corn-based diets without hurting performance or quality, provided diets are balanced for amino acids

by JANICE MURPHY

Field peas have been grown for centuries around the globe, but historically they have been produced for human consumption. Over the past 25 years, the industry has also found markets for them in livestock feeding. Field peas have traditionally been fed to ruminants, but they are now also more commonly included in diets fed to pigs.

Research previously suggested that field peas could be included in diets fed to nursery pigs at 18 per cent and to growing-finishing pigs at 36 per cent without negatively affecting performance or carcass composition. At an inclusion rate of 36 per cent, field peas replace all the soybean meal in the late finisher diet, but soybean meal is still needed in the grower and the early finisher diets to meet the pig’s requirement for individual amino acids.

Researchers in South Dakota recently set out to test whether field peas can completely replace soybean meal in diets fed to growing and finishing pigs without affecting performance, carcass quality or the palatability of pork. At an average weight of 22 kilograms, 48 growing pigs were randomly allotted to one of three experimental treatments – control, medium field peas and maximum field peas. Pigs were fed grower diets for 35 days, early finisher diets for 35 days and late finisher diets for 45 days.

Pigs receiving the control treatment were fed corn-soybean meal diets. All diets fed to pigs receiving the medium treatment contained 36 per cent field peas with varying amounts of corn. Soybean meal was also included in the grower and the early finisher diets fed to pigs on this treatment.

On the maximum treatment, no soybean meal was used in the diets, and field peas were included at levels of 66, 48 and 36 per cent respectively in the grower, early finisher and late finisher diets. The inclusion rate of lysine was reduced, while the inclusion of methionine, threonine and tryptophan increased as the concentration of field peas in the diets increased, since pea protein contains more lysine but less of the other amino acids than soybean protein.

The results from the experiment are summarized in Table 1. Pig performance showed that treatment had no impact on average daily feed intake, average daily gain or feed efficiency in each of the periods studied or overall. Based on performance, it appears that, as long as diets are properly formulated to meet amino acid requirements, the inclusion rate of field peas is irrelevant.
 
This particular experiment did not attempt to measure palatability of the peas. Since feed intake on the pea-based diets was similar to the control diet in all phases, it is clear that feed intake is not influenced by the inclusion of field peas in the diets.

Following along with the performance data, there were no differences in carcass composition among the treatment groups. However, carcass quality appeared to improve slightly with the addition of field peas. The subjective and objective colour scores suggested that dietary field peas made the longissimus muscle darker and more desirable compared to the corn-soybean meal control. The researchers postulated that this difference might have come about because field peas contain less fat than corn, resulting in less fat in the pea diets to influence the colour of the meat.

Another interesting observation was that drip loss from pork chops decreased with increasing levels of field peas (3.39, 2.51 and 1.95 per cent respectively for pigs fed control, medium pea and maximum field pea diets). No obvious explanation for this result is available.

However, the researchers suggest that the combination of darker colours and lower drip losses in pigs fed pea-diets might indicate that field peas cause physiological changes in the meat. In order to identify the specific mechanisms involved, further research is necessary. Despite the improvements, the trained taste panellists did not detect any differences in the palatability of pork chops between treatments.

Data from this particular experiment clearly indicate that field peas can replace soybean meal in corn-based diets fed to growing and finishing pigs without negatively affecting performance, carcass composition, carcass quality or pork palatability, provided that diets are balanced for amino acids.

The researchers recommend that producers ultimately base their formulation decisions on economics since there appear to be no biological restrictions on the use of field peas in diets fed to growing and finishing pigs.

Where substitutions are planned, a good rule of thumb is that three per cent field peas will replace approximately two per cent corn and one per cent soybean meal if sources of methionine, threonine and tryptophan are included to balance amino acid levels. At the same time, the inclusion of lysine and the phosphate source can be reduced. BP

Janice Murphy is the former Swine Nutritionist with the Ontario Ministry of Agriculture, Food and Rural Affairs.

Sources:
Stein, H. H, Everts, A. K. R., Sweeter, K. K., Peters, D. N., Maddock, R. J.,
Wulf, D. M., and Pedersen, C. 2006. The influence of dietary field peas (Pisum sativum L.) on pig performance, carcass quality and the palatability of pork. J. Anim. Sci. 84:3110–3117.
Stein, H. and de Lange, K. 2007. Alternative feed ingredients for pigs. Proceedings of the London Swine Conference. p. 103.