Effects of microbial phytase in pig diets on calcium requirements, post-weaning growth performance, phytate degradation, and nutrient digestibility

Lagos Munoz, Liz Vanessa

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Description

Title

Effects of microbial phytase in pig diets on calcium requirements, post-weaning growth performance, phytate degradation, and nutrient digestibility

Author(s)

Lagos Munoz, Liz Vanessa

Issue Date

2021-08-20

Director of Research (if dissertation) or Advisor (if thesis)

Stein, Hans H

Doctoral Committee Chair(s)

Swanson, Kelly S

Committee Member(s)

• Murphy, Michael R
• Cardoso, Phil
• Bedford, Mike R

Department of Study

Nutritional Sciences

Discipline

Nutritional Sciences

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• Ca and P
• gastric pH
• phytase
• nutrient digestibility
• phytate degradation
• pigs

Abstract

Seven experiments were conducted to test a series of formulated hypotheses regarding Ca and microbial phytase in pig diets. In experiment 1, the hypothesis was that analyzed values for Ca and P in commercial pig diets in the U.S. are not greater than calculated values. However, in 103 diet samples, an average of 0.19% (model; P < 0.05) more total Ca than expected was observed, whereas for total P, the average oversupply was only 0.06% (model; P < 0.05). It was, therefore, concluded that diets used in the U.S. swine industry contain more Ca than formulated, but this is not the case for P. In experiments 2 and 3, the hypothesis was that Ca requirements by pigs expressed as standardized total tract digestible (STTD) Ca can be used to formulate diets without or with phytase. In experiment 2, four diets were formulated with 2 formulation principles (total or STTD Ca) and 2 levels of phytase [0 or 500 phytase units/kg feed (FTU)] and fed to pigs from 11 to 130 kg in a 5-phase program. Results indicated that pigs fed non-phytase diets based on total Ca had greater bone ash than pigs fed STTD Ca diets, but if phytase was used, no differences were observed between formulation principles (interaction; P < 0.05). However, there was no effect of dietary treatment on growth performance of pigs. In experiment 3, the 4 diets used in phase 3 of experiment 2 were fed to 60-kg pigs housed in metabolism crates, and fecal and urine samples were collected for 4 d after a 5-d adaptation period. Results indicated that regardless of phytase, there were no differences in Ca retention between pigs fed STTD Ca and total Ca diets. It was concluded from experiments 2 and 3 that STTD Ca values can be used to formulate diets without affecting bone ash, growth performance, or Ca retention of pigs. In experiments 4 and 5, the hypothesis was that reducing dietary Ca and P reduces stomach pH and diarrhea incidence, and dietary phytase counters negative effects of weaning. In experiment 4, four diets were formulated with 2 levels of Ca and P (deficient and adequate) and 2 levels of phytase (0 or 2,000 FTU). Diets were fed to newly weaned pigs in a 3-phase program with common diets used in phases 2 and 3. In phase 1, at deficient levels of Ca and P, inclusion of phytase resulted in greater average daily gain (ADG) and gain to feed (G:F), but at adequate levels, no effect of phytase inclusion was observed (interaction, P < 0.05). Gastric pH and fecal score were not influenced by dietary Ca and P. However, bone ash after phase 1 was greater (P < 0.05) if diets with adequate instead of deficient levels of Ca and P were used, but no effect of phytase was observed. In experiment 5, two control diets containing 100 or 50% of Ca and P relative to the requirement, and 6 diets in which 500, 2,000, or 16,000 FTU were added to each control diet were formulated, and a 3-phase program was used with common diets fed in phases 2 and 3. Results indicated that reducing Ca and P did not reduce gastric pH or fecal score, but pigs fed the 50% diets had reduced (P < 0.05) ADG in phase 1 and reduced (P < 0.05) bone ash at the end of phases 1 and 3 compared with pigs fed the 100% diets. In both 50 and 100% diets, phytase above 500 FTU increased (P < 0.05) plasma inositol and G:F of pigs. It was concluded from experiments 4 and 5 that reducing Ca and P in phase 1 diets did not influence gastric pH or fecal score, but compromised growth performance and bone ash. However, inclusion of phytase increased inositol absorption and G:F of pigs. In experiments 6 and 7, the hypothesis was that regardless of body weight (BW), increasing levels of phytase increases phytate degradation and nutrient digestibility. In both experiments, pigs with a T-cannula in the distal ileum and 6 diets with 0, 250, 500, 1,000, 2,000, or 4,000 FTU were used. In experiment 6, 11-kg pigs were used and samples were collected after 18 d of adaptation to the diets. Results indicated that apparent ileal digestibility (AID) of Trp (quadratic; P < 0.05), Lys and Thr (linear; P < 0.05) and apparent total tract digestibility (ATTD) of Ca and P (quadratic; P < 0.05) increased as phytase inclusion increased. Inositol in plasma and ileal digesta increased (linear; P < 0.05), but inositol phosphate (IP) 6 and IP5 (quadratic; P < 0.05), as well as IP4 and IP3 decreased (linear; P < 0.05) in ileal digesta as dietary phytase increased. In experiment 7, phytase effects were evaluated in 4 phases in which the same pigs (from 25 to 130 kg) were used. Results indicated that regardless of BW, AID of most AA and ATTD of Ca and P increased (quadratic; P < 0.05) with increasing inclusion of phytase. However, AID of AA linearly increased (P < 0.05), whereas ATTD of Ca (linear; P < 0.05) and of P (quadratic; P < 0.05) decreased as BW of pigs increased. In all phases, concentrations of IP esters in ileal digesta decreased (quadratic; P < 0.05), whereas inositol in ileal digesta increased (quadratic; P < 0.05) with increasing dietary phytase. However, concentrations of IP esters increased (quadratic; P < 0.05) but inositol decreased (linear; P < 0.05) in ileal digesta as BW of pigs increased. It was, therefore, concluded from experiments 6 and 7 that regardless of BW, increasing dietary phytase increased phytate degradation and inositol release and absorption, and consequently, increased Ca, P, and AA digestibility. However, older pigs have reduced Ca and P digestibility, but increased AA digestibility compared with younger pigs and the efficiency of phytase decreased as pigs get older. Overall, commercial pig diets in the U.S. contain more Ca than expected. Diets for growing-finishing pigs can be formulated based on STTD Ca values. The use of high doses of phytase in phase 1 diets may provide benefits to weanling pigs in addition to increased release of Ca and P. The effect of phytase on phytate degradation and nutrient digestibility is independent of BW, but nutrient digestibility and phytase efficiency are influenced by BW of pigs.

Graduation Semester

2021-12

Type of Resource

Thesis

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© 2021 L. Vanessa Lagos

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