The majority of P in most plant feed ingredients is bound to phytate. Pigs, however, do not synthesize adequate endogenous phytate to release the P bound to phytate, which results in low digestibility of P in field peas. Values for ATTD and STTD of P in field peas without and with phytase have been reported, but there are no comparative values for the ATTD and STTD of P in field peas adding different levels of phytase. The objective of this experiment is to determine the effect of increasing levels of phytase on the apparent total tract digestibility (ATTD) and standardized total tract digestibility (STTD) of P in field peas fed to growing pigs.
Experimental design
A source of field peas from the U.S. (e.g. U.S. field peas) were procured. A basal diet based on field peas and sucrose was formulated (Table 1). Five additional diets were formulated by adding 250, 500, 1,000, 2000 or 4,000 FTU of phytase (Quantum Blue; AB Vista Feed Ingredients, Marlborough, UK). A total of 48 barrows (15.0 ± 0.9 kg) were allotted to a randomized complete block design with 6 diets, 2 blocks of 12 pigs, and 1 block of 24 pigs, for a total of 8 replicate pigs per diet. 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 P to calculate for ATTD and STTD of P in each diet.
Results
Daily feed intake was increased (linear, P < 0.05) as phytase increased in the diets. Likewise, daily P intake increased (linear and quadratic, P < 0.05) by increasing phytase in the diets (Table 2). However, daily fecal excretion and P concentration in feces expressed as a percent and as in grams decreased (linear, P < 0.01) as phytase increased in the diets. As a consequence, the ATTD and the STTD of P linearly increased (P < 0.01) increased as phytase increased in the diets, which resulted in an increasing (linear, P < 0.01) of P absorbed as well.
Key points
- Microbial phytase used in this experiment was efficient to release the P in field peas.
- The addition of phytase leads to increase P digestibility in field peas, and may be used when young pigs are fed diets with field peas.
Table 1. Analyzed nutrient composition of experimental diets containing field peas (as-fed basis)
1The vitamin-micromineral premix provided the following quantities of vitamins and micro minerals per kg of complete diet: vitamin A as retinyl acetate, 10,622 IU; vitamin D3 as cholecalciferol, 1,660 IU; vitamin E as selenium yeast, 66 IU; vitamin K as menadione nicotinamide bisulfate, 1.40 mg; thiamin as thiamine mononitrate, 1.08 mg; riboflavin, 6.49 mg; pyridoxine as pyridoxine hydrochloride, 0.98 mg; vitamin B12, 0.03 mg; D-pantothenic acid as D-calcium pantothenate, 23.2 mg; niacin, 43.4 mg; folic acid, 1.56 mg; biotin, 0.44 mg; Cu, 20 mg as copper chloride; Fe, 123 mg as iron sulfate; I, 1.24 mg as ethylenediamine dihydriodide; Mn, 59.4 mg as manganese hydroxychloride; Se, 0.27 mg as sodium selenite and selenium yeast; and Zn, 124.7 mg as zinc hydroxychloride.
2The phytase concentrate contained 5,000 units of phytase/g (Quantum Blue; AB Vista Feed Ingredients, Marlborough, UK).
Table 2. Effects of increasing levels of phytase on apparent total tract digestibility (ATTD) and standardized total tract digestibility (STTD) of P of field peas1
1Data are least squares means of 8 observations per treatment.
2Calculated by correcting the ATTD of P with an average basal endogenous loss of P (i.e., 190 mg/kg DMI; NRC, 2012).