The majority of P in oilseed co-products is bound to phytate; however, pigs do not synthesize adequate amount of endogenous phytate to liberate the P bound to phytate and the digestibility of P in sunflower meal, therefore is low. Values for ATTD and STTD of P in sunflower meal (SFM) without and with phytase have been reported, but there are no comparative values for the ATTD and STTD of P in sunflower co-products produced in different parts of the world. Therefore, the objective of this experiment was to determine the ATTD and the STTD of P in different sources of sunflower co-products, and to test the hypothesis that regardless of source, microbial phytase increases the digestibility of P in sunflower co-products fed to young pigs.

Experimental design

Seven sources of sunflower meal were used. Six sources of SFM included two sources from Ukraine, two sources from the U.S., and one source from both Hungary and Italy. The sunflower expeller (SFE) was from the U.S. Seven diets based on each source of sunflower co-product were formulated. Seven additional diets were also formulated, and these diets were similar to the previous seven diets with the exception that 500 units per kg of microbial phytase was added to these diets. A total of 112 barrows (17.95 ± 1.37 kg) were used and allotted to a randomized complete block design with 14 diets and four blocks of 28 pigs, two pigs per diet in each block, and a total of eight replicate pigs per diet. Weaning group was considered as the blocking factor. Pigs were housed individually in metabolism crates. The initial 5 days were considered the adaptation period to diets, and fecal samples were collected for 4 days following the adaptation period. Diets, ingredients, and fecal samples were analyzed for Ca and P to calculate for STTD of P and ATTD of Ca in each diet.

Results

Pigs fed diets with phytase had reduced (P < 0.01) concentration of P in feces compared with diets without phytase, and pigs fed diets containing one of the sources of SFM from the U.S. had reduced (P < 0.01) concentration of P in feces compared with the other sources of SFM (Table 1). When phytase was included in the diet, absorption of P was greater (P < 0.01) than if no phytase was added to the diets regardless of the source of sunflower co-product. As a result, diets containing phytase had greater (P < 0.01) ATTD and STTD of P than diets without phytase. One source of SFM from Ukraine and the SFM from Hungary had greater (P < 0.01) STTD of P compared with SFE.

When phytase was added to the diets, absorption of Ca was greater (P < 0.01) regardless of the source of sunflower co-product (Table 2). As a result, diets containing phytase had greater (P < 0.01) ATTD and STTD of Ca than diets without phytase. Diets containing one of the SFM from the U.S. had the least (P < 0.01) excretion of Ca in feces among the sources of sunflower co-product. Calcium absorption was greater (P < 0.01) in diets containing the SFM from Italy or one of the SFM sources from the U.S. compared with the SFM from Ukraine and the other SFM from the U.S. Pigs fed the diet containing one of the sources of SFM from the U.S. had greater (P < 0.05) ATTD of Ca compared with pigs fed diets containing the other source of SFM from the U.S. or one of the Ukraine SFM sources.

Key points

• Differences in digestibility of P in sunflower co-products are likely due to either differences in cultivation conditions or differences in the processing of sunflower seeds.
• Inclusion of microbial phytase to pig diets containing SFM or SFE increased the digestibility of Ca and P regardless of the type of sunflower co-product used.

Table 1. Apparent total tract digestibility (ATTD) and standardized total tract digestibility (STTD) of P in seven sources of sunflower co-product¹

^a-e Means within a row that do not have a common superscript tend to differ (P < 0.05).

¹Data are least squares means of 8 observations per treatment. Except for U.S. 2 and Hungary sources, which had 7 observations per treatment. Phytase × Sunflower source interactions were not significant; therefore, only the main effects are indicated.

²EPL = endogenous P loss. This value was estimated to be at 190 mg/kg DMI (dry matter intake). The daily basal EPL (mg/d) for each diet was calculated by multiplying the EPL (mg/kg DMI) by the daily DMI of each diet (Almeida and Stein, 2010).

³Values for STTD were calculated by correcting values for ATTD for the basal endogenous loss of P (NRC, 2012).

Table 2. Apparent total tract digestibility (ATTD) of Ca in in seven sources of sunflower co-product¹

^a-c Means within a row that do not have a common superscript tend to differ (P < 0.05).

¹Data are least squares means of 8 observations per treatment except for U.S. 2 and Hungary sources (7 observations per treatment). Phytase × Sunflower source interactions were not significant; therefore, only the main effects are indicated.