Most swine diets must be supplemented with calcium because most plant ingredients commonly used in diets for pigs contain relatively little calcium. One way to add calcium is to include inorganic sources such as dicalcium phosphate or calcium carbonate; however, animal ingredients such as meat byproduct meals can also be used. These ingredients, often used as a protein source, are also a good source of calcium. To our knowledge, values for apparent (ATTD) and standardized (STTD) total tract digestibility of calcium in animal sources have not been reported. Therefore, an experiment was conducted to determine the ATTD and STTD of calcium in four calcium sources of animal origin.

The secondary objective of the study was to test the hypothesis that the addition of microbial phytase to diets containing calcium sources of animal origin would increase the digestibility of calcium. Although animal sources do not contain phytate, swine diets are composed primarily of plant ingredients, and the phytate in those ingredients might form complexes with the calcium in the animal sources.

A total of seventy-two pigs with an average initial body weight of 14.91 kg were randomly assigned to be fed nine experimental diets. The first four diets were corn-based diets containing meat and bone meal, meat meal, poultry byproduct meal, or poultry meal as the only source of calcium. Another four diets were identical to  the first four with the exception that they also contained 500 phytase units (FTU) of microbial phytase (Quantum Blue, AB Vista, Marlborough, UK). The ninth diet contained no calcium, and was used to measure basal endogenous losses of calcium.

After a five day period of adaptation to the diets, feces were collected and analyzed to determine the ATTD of calcium and phosphorus. The ATTD of calcium was adjusted using the basal endogenous losses to calculate the STTD.

When microbial phytase was not added to the diets, the ATTD and STTD of calcium was greatest (P < 0.05) in poultry byproduct meal and poultry meal (Table 1).  Calcium digestibility did not differ among poultry meal, meat and bone meal, and meat meal. When phytase was added, the ATTD and STTD of calcium did not differ among the ingredients. The ATTD and STTD of calcium did not increase when phytase was added to the diets.

• The ATTD and STTD of calcium is greater in poultry byproduct meal than in meat and bone meal and meat meal, and the same as in poultry meal, when no phytase is added to the diets.
• Microbial phytase does not affect the digestibility of calcium in meat and bone meal, meat meal, poultry byproduct meal, and poultry meal when included in corn-based diets.

Table 1. Apparent (ATTD) and standardized (STTD) total tract digestibility of calcium by pigs fed meat and bone meal, meat meal, poultry byproduct meal, or poultry meal without or with microbial phytase

^a-bMeans within a column not sharing a common superscript are different (P < 0.05).

This report is based on unpublished research by Laura Merriman, Carrie Walk, and Hans H. Stein.