Navarro D. M. D. L., E. M. A. M. Bruininx, L. de Jong, H. H. Stein. 2019. Effects of inclusion rate of high fiber dietary ingredients on apparent ileal, hindgut, and total tract digestibility of dry matter and nutrients in ingredients fed to growing pigs. Anim. Feed Sci. Technol. 248: 1 - 9. Link to full text.

McGhee Molly L. and Hans. H. Stein. 2018. Apparent and standardized ileal digestibility of AA and starch in hybrid rye, barley, wheat, and corn fed to growing pigs. J. Anim. Sci. 96:3319–3329.  Link to full text.

Navarro D.M.D.L., J.K. Mathai, N.W. Jaworski, H.H. Stein. 2018. Amino acid digestibility in six sources of meat and bone meal, blood meal, and soybean meal fed to growing pigs. Can. J. Anim. Sci. 98: 860–867. Link to full text. 

Requirements for P for growing pigs are expressed as the requirement for standardized total tract digestible (STTD) P, whereas requirements for Ca are usually expressed as requirements for total Ca. It is, however, recognized that diets for pigs are most accurately formulated based on a STTD Ca:STTD P ratio, and recent work has generated values for STTD of Ca in most Ca containing feed ingredients, which makes it possible to formulate diets based on STTD Ca.

Recent data from the University of Illinois have indicated that if STTD P is at the requirement, a ratio between STTD Ca and STTD P that is less than 1.35:1, 1.25:1, and 1.10:1 maximizes growth performance of pigs from 25 to 50 kg, 50 to 85 kg, and 100 to 130 kg, respectively. However, the STTD Ca:STTD P ratio needed to maximize bone ash is greater than the ratio needed to maximize growth performance. An attempt to estimate the requirement for STTD Ca by pigs from 11 to 25 kg was also made, but due to a reduction in ADG and G:F as dietary Ca increased, an optimal STTD Ca:STTD P ratio could not be estimated.

Calcium may be absorbed by transcellular or paracellular transport. Transcellular transport is the primary route if dietary Ca is low, but if dietary Ca is adequate or high, Ca is mainly absorbed using the paracellular route via the tight junctions. However, there are limited data demonstrating effects of dietary Ca concentration on abundance of genes related to transcellular and paracellular transport of Ca in the small intestine of pigs.

Therefore, the objectives of this experiment were to test the hypotheses that a STTD Ca:STTD P ratio less than 1.40:1 maximizes growth performance of pigs from 11 to 25 kg and that increasing dietary Ca downregulates abundance of genes related to transcellular absorption of Ca and tight junction proteins in the small intestine.

Lee, S. A., Vanessa Lagos, and Hans H. Stein. 2018. Effect of dietary calcium on growth performance of growing pigs. Pages 173 - 184. XXXIV Specialization Course FEDNA, Madrid, Nov. 22 - 23, 2018. Link to full text (.pdf)

Leucine, Val, and Ile are categorized as the branched-chain AA (BCAA) because of the structural similarity of their side chains. All 3 BCAA share the enzymes that are involved in the first 2 steps of their catabolic pathway. The first step is a transamination step catalyzed by BCAA transaminase (BCAT) and producing branched-chain α-keto acids (BCKA). The second step is an irreversible degradation step catalyzed by branched-chain α-keto acid dehydrogenase (BCKDH). In the second step, Leu has been considered a key regulator as its BCKA metabolite (α-keto isocaproate) stimulates activation of the BCKDH complex in the liver. When excess Leu in diets is offered to pigs, degradation of all 3 BCAA may increase because of increased activity of BCAT and BCKDH. Leucine and Trp are both categorized as large neutral AA, and they share a common uptake pathway across the blood-brain barrier. Therefore, it is possible that excessive Leu may result in reduced Trp uptake into the brain due to competition for transporters, resulting in reduced serotonin synthesis.

Direct fed microbials (DFM) are defined as live microorganisms that offer a health benefit for the host when administered in appropriate and regular quantities. Bacillus-based DFM are aerobic, spore-forming bacteria that may enhance the host animal’s immune response and improve growth performance in weanling pigs. Bacillus spp. also produce extracellular enzymes that may enhance digestibility and absorption of nutrients.

An experiment was, therefore, conducted to test the hypothesis that two DFM containing Bacillus strains (provided by Chr. Hansen A/S, Horsholm, Denmark) improve the apparent ileal digestibility (AID) of AA, CP, and GE, the apparent total tract digestibility (ATTD) of CP and GE, and hindgut digestibility of CP and GE when fed to growing pigs.

Digestibility of Ca and P is most correctly determined as standardized total tract digestibility (STTD). Data for the STTD of P in most feed ingredients have been published, and the STTD of Ca has also been determined in many feed ingredients. However, in practical diet formulation, values for STTD of Ca and P obtained in growing pigs are also applied to sows although there is a lack of comparative data between growing pigs and sows.

Therefore, an experiment was conducted to test the hypothesis that no differences exist between gestating sows and growing pigs for basal endogenous losses, STTD, and retention of Ca and P.

Lee, S. A., G. A. Casas, and H. H. Stein. 2018. The level of feed intake does not influence digestibility of calcium and phosphorus in diets fed to gestating sows, but gestating sows have reduced digestibility of calcium and phosphorus compared with growing gilts. Can. J. Anim. Sci. 98:591-594. Link to abstract