#17-116

Complete

Date Full Report Received

06/29/2018

Date Abstract Report Received

06/29/2018

Corn germ meal (CGM), a co-product of the corn wet milling industry, is an ingredient that could be used to reduce the cost of swine diets. Efficient use of any ingredient requires an accurate estimate of energy content and metabolizable energy (ME) is the standard energy measurement that is used in diet formulation in the US. However, there are few published estimates of the ME content of CGM. In addition, for ingredients high in fiber, such as CGM, using the ME system overestimates the energy available to the animal for production. An approach that has been advocated to overcome the problem with using ME is to determine the productive energy (PE) of ingredients such as CGM. This is estimated from the growth performance, in particular feed and energy efficiency, of pigs fed a diet including the test ingredient with that of pigs fed a reference diet based on a standard ingredient (e.g., a corn-soybean meal based diet). Determination of PE is relatively easy to carry out, can be conducted on commercial as well as research units, and does not require specialized facilities or equipment. However, the appropriate methodology to determine PE has not been investigated and the optimum approach to estimate PE has not been established. Therefore, the objectives of this research were to estimate the PE of CGM based on growth studies conducted at either a university research unit or a commercial production facility across various weight ranges in the growing-finishing period. In addition, these estimates of PE were compared with direct measurement of the ME of CGM using a standard metabolism study.
Four experiments were conducted; 2 growth performance evaluation studies (at either a Commercial or University research site), and 2 metabolism studies to measure the ME content of ingredients and diets used in the growth studies. Three diets were compared [a Control diet based on corn and soybean meal and 2 diets containing 20% CGM (with and without added fat)] across 4 growth periods [Early Growing (64 to 141 lb live weight), Late Growing (141 to 211 lb live weight), Finishing (141 to 280 lb live weight), and Growing-Finishing (64 to 280 lb live weight)]. A total of 3,672 and 576 barrows and gilts housed in mixed-sex groups of 34 and 4 were used in the Commercial and University experiments, respectively, giving 12 replicates per diet for each growing period at each site. The CGM used was from a single source and a single diet phase was used in each growth period. The ME value of CGM used to formulate diets, based on previous research, was 2,548 kcal/kg. Two standard metabolism studies were carried out to directly measure the ME content of corn and CGM and also of the 3 diets that were use in the Early Growing period of the growth study, respectively.
The growth performance of pigs at the University site was more variable than at the Commercial site which was most likely the result of the larger group sizes and total numbers of animals used at the Commercial site. In addition, estimates of the PE of CGM were much more variable for the 3 diets and growth periods at the University site. Also, the PE of CGM estimated in the Finishing period at both sites was greater than estimates from the other growth periods. The ME of corn and CGM measured directly in metabolism studies were similar to estimates published by NRC (2012); however, the estimate of ME of CGM was considerably greater than the PE estimated from the growth studies. The ME of the Control diet used in the Early Growing period measured in the metabolism study was similar to the formulated value for this diet. However, the ME values for the 2 CGM diets used in the Early Growing period determined in the metabolism study were greater than the formulated values.
The results of this research suggest that the most appropriate approach to estimate PE would be using large-scale, controlled research studies carried out under commercial conditions rather than relatively small-scale studies under university conditions. Also, this research suggests that PE could be accurately determined over a relatively short period early in the growing period rather than over the entire growing-finishing period. Finally, the direct measurement of ME of CGM and of diets containing CGM from metabolism studies confirmed that this approach generally overestimates the energy available to the pig for growth which emphasizes the potential benefit of the use of the PE approach.

Key Findings:
The results of this research suggest that:

  • Corn germ meal is a viable ingredient that can be used in diets for growing-finishing pigs (at least up to 20% inclusion level).
  • The Metabolizable Energy value of CGM determined using a metabolism study (the conventional approach) overestimated the energy available to the pig for growth; this supports the use of the Productive Energy concept for the estimation of the energy value of corn germ meal and other fibrous ingredients.
  • Estimates of Productive Energy of corn germ meal based on growth assays were:
    • Influenced substantially by the research conditions and the weight range over which the assay was conducted.
    • More consistent when measured under controlled commercial conditions and relatively early in the growing period than when measured under University research conditions and at heavier weights.
    • Were greater when measured in finishing than in growing pigs, suggesting that, in theory, a different energy value should be used for fibrous ingredients for different weights of pigs.
  • The most appropriate approach to estimating PE is in large-scale controlled studies carried out under commercial conditions during the early growing period.

Contact:
Mike Ellis
Department of Animal Science
University of Illinois
Email: mellis7@illinois.edu
Phone: 217 333 6455