N. L. Trottier

Effects of xylanase supplementation on the apparent digestibility and digestible content of energy, amino acids, phosphorus, and calcium in wheat and wheat by-products from dry milling fed to grower pigs.

Wheat by-products are feedstuffs that vary in nutritional value, partly because of arabinoxylans that limit nutrient digestibility. Millrun is a byproduct from dry milling wheat into flour and contains varying amounts of the bran, middlings, screening, and shorts fractions. The digestible nutrient content of mill-run is not well known. Effects of xylanase supplementation (0 or 4,000 units/kg of diet) on energy, AA, P, and Ca digestibilities were studied in a wheat control diet and 5 diets containing 30% of a by-product (mill-run, middlings, shorts, screening, or bran) in a 2 x 6 factorial arrangement of treatments. The wheat control diet was formulated to contain 3.34 Mcal of DE/kg and 3.0 g of standardized ileal digestible Lys/Mcal of DE. Diets contained 0.4% chromic oxide. Each of 12 ileal-cannulated pigs (32.5 +/- 2.5 kg) was fed 6 or 7 of 12 diets at 3 times the DE requirement for maintenance in successive 10-d periods for 6 or 7 observations per diet. Feces and ileal digesta were each collected for 2 d. Xylanase tended to increase (P < 0.10) ileal energy digestibility by 2.2 percentage units and the DE content by 0.10 Mcal/kg of DM and increased (P < 0.05) ileal DM digestibility by 2.8 percentage units; a diet x xylanase interaction was not observed. Xylanase increased (P < 0.05) total tract energy and DM digestibilities and the DE content. A diet x xylanase interaction was observed; xylanase increased (P < 0.05) total tract energy digestibility of the millrun diet from 72.1 to 78.9%, DE content from 3.19 to 3.51 Mcal/kg of DM, and DM digestibility from 71.5 to 78.6%. Diet affected (P < 0.05) and xylanase improved (P < 0.05) digestibility and digestible contents of some AA in diets and by-products, including Lys, Thr, and Val. Xylanase increased (P < 0.05) Lys digestibility by 13.8, 5.0, 5.2, 6.0, and 14.1 percentage units in millrun, middlings, shorts, screening, and bran, respectively. Diet affected (P < 0.01) total tract P and Ca digestibilities. Xylanase increased (P < 0.05) digestible P and Ca contents. In summary, nutrient digestibility varies among wheat by-products. Millrun contained 2.65 Mcal of DE/kg of DM, which xylanase increased to 3.56 Mcal of DE/kg of DM. Xylanase improved nutrient digestibility and DE content in wheat by-products; and the extent of improvement depended on the by-product. Xylanase supplementation may maximize opportunities to include wheat byproducts in swine diets and ameliorate reductions in nutrient digestibility that may be associated with arabinoxylans.

Creatine Synthesis Is a Major Metabolic Process in Neonatal Piglets and Has Important Implications for Amino Acid Metabolism and Methyl Balance

Our objectives in this study were as follows: 1) to determine the rate of creatine accretion by the neonatal piglet; 2) identify the sources of this creatine; 3) measure the activities of the enzymes of creatine synthesis; and 4) to estimate the burden that endogenous creatine synthesis places on the metabolism of the 3 amino acids required for this synthesis: glycine, arginine, and methionine. We found that piglets acquire 12.5 mmol of total creatine (creatine plus creatine phosphate) between 4 and 11 d of age. As much as one-quarter of creatine accretion in neonatal piglets may be provided by sow milk and three-quarters by de novo synthesis by piglets. This rate of creatine synthesis makes very large demands on arginine and methionine metabolism, although the magnitude of the demand depends on the rate of remethylation of homocysteine and of reamidination of ornithine. Of the 2 enzymes of creatine synthesis, we found high activity of l-arginine:glycine amidinotransferase in piglet kidneys and pancreas and of guanidinoacetate methyltransferase in piglet livers. Piglet livers also had appreciable activities of methionine adenosyltransferase, which synthesizes S-adenosylmethionine, and of betaine:homocysteine methyltransferase, methionine synthase, and methylene tetrahydrofolate reductase, which are required for the remethylation of homocysteine to methionine. Creatine synthesis is a quantitatively major metabolic process in piglets.

Dietary Protein Intake and Stage of Lactation Differentially Modulate Amino Acid Transporter mRNA Abundance in Porcine Mammary Tissue

To test the hypothesis that under restricted and surfeit protein intake the mammary gland undergoes adaptive regulation, changes in mammary tissue mRNA abundance of cationic amino acid (AA) transporter (CAT)-1, CAT-2B, alanine/serine/cysteine/threonine transporter 1 (ASCT1), and broad specificity transporter for neutral and cationic AA (ATB(0,+)), and CAT-1 protein abundance were investigated at 2 stages of lactation. Eighteen sows were allocated to a 2 x 3 randomized incomplete block design with 2 stages of lactation (early and peak) and 3 protein levels: deficient (D), adequate (A), or in excess (E) of lactation requirement. In early lactation, compared with A, sows fed E had lower (P = 0.05) piglet growth rate and sows fed D or E had lower (P < or = 0.05) casein yield. In early lactation, piglet growth rate and milk protein and casein yield increased from D to A and decreased from A to E (quadratic, P = 0.095, P < 0.05, and P < 0.01, respectively). Protein intake did not affect CAT-1, ASCT1, ATB(0,+) mRNA abundance, or CAT-1 protein level. Overall, CAT-2B mRNA abundance decreased linearly with increasing protein intake (P < 0.05). Compared with A, E decreased CAT-2B mRNA abundance (P < 0.05). Compared with early lactation, peak lactation did not increase CAT-1 mRNA abundance or relative CAT-1 protein content, but increased abundance of ASCT1 and ATB(0,+) mRNA (P < 0.01). Mammary CAT-2B appears to be adaptively regulated in vivo at the transcription level, whereas ASCT1 and ATB(0,+) mRNA abundances are associated only with stage of lactation. Neither protein intake nor stage of lactation affects porcine mammary CAT-1 gene expression in vivo.

Cationic and neutral amino acid transporter transcript abundances are differentially expressed in the equine intestinal tract

To test the hypothesis that AA transporter transcripts are present in the large intestine and similarly expressed along the intestinal tract, mRNA abundance of candidate AA transporter genes solute carrier (SLC) family 7, member 9 (SLC7A9), SLC7A1, SLC7A8, and SLC43A1 encoding for b(0,+)-type AA transporter (b(0,+)AT), cationic AA transporter-1 (CAT-1), L-type AA transporter-2 (LAT-2), and L-type AA transporter-3 (LAT-3), respectively, was determined in small and large intestinal segments of the horse. Mucosa was collected from the equine small (jejunum and ileum) and large intestine (cecum, left ventral colon, and left dorsal colon), flash frozen in liquid nitrogen, and stored at -80 degrees C. Messenger RNA was isolated from tissue samples, followed by manufacture of cDNA. Relative quantitative reverse transcription-PCR was conducted using the 2(-DeltaDeltaCT) method, with glyceraldehyde-3-phosphate dehydrogenase serving as the housekeeping gene. Compared with the jejunum, cationic and neutral AA transporter SLC7A9 mRNA abundance was similar in the ileum, cecum, and large intestinal segments. Compared with the jejunum, cationic AA transporter SLC7A1 mRNA abundance was similar in the ileum and decreased in the cecum, left ventral colon, and left dorsal colon (P < 0.001). Neutral AA transporter SLC7A8 mRNA abundance decreased from the cranial to caudal end of the intestinal tract (P < 0.001). Neutral AA transporter SLC43A1 mRNA abundance was similar in the ileum and left dorsal colon and increased in the cecum (P < 0.01) and left ventral colon (P < 0.1) compared with the jejunum. Cationic and neutral AA transporter SLC7A9 mRNA abundance was similarly expressed in the large compared with small intestine, whereas cationic AA transporter SLC7A1 was of low abundance in the large intestine; neutral AA transporters SLC7A8 and SLC43A1 were differentially expressed with decreased abundance of SLC7A8 and increased abundance of SLC43A1 in the large intestine. Results indicate that the large intestine might contribute to both cationic and neutral AA uptake and absorption predominantly via transporters LAT-3 and b(0,+)AT.

Transcript abundance of hormone receptors, mammalian target of rapamycin pathway-related kinases, insulin-like growth factor I, and milk proteins in porcine mammary tissue.

Prolactin, glucocorticoids, and insulin are commonly used to induce milk protein synthesis in bovine mammary cell cultures. In addition, administration of GH increases milk yield in dairy cows, likely via the mammalian target of rapamycin (mTOR) pathway and IGF-I synthesis. As such, the hypothesis of this study was that mRNA abundance of hormone receptors, mammalian target of mTOR pathway-related kinases, IGF-I, and milk protein-encoding genes increases in the porcine mammary gland in response to greater lactation demand. Selected genes included those encoding for receptors of GH (GHR), insulin (INSR), glucocorticoid (NR3C1), prolactin (PRLR), IGF-I (IGF-I), mTOR (FRAP1), and p70S6 kinases (RPS6KB1), and the milk proteins α-lactalbumin (LALBA) and β-casein (CSN2). Mammary tissue was biopsied from 4 sows on d 110 of gestation (prepartum), d 5 and 17 of lactation, and d 5 after weaning (postweaning), and gene expression was quantified by reverse-transcription quantitative PCR. Compared with prepartum, d 5 of lactation increased (P < 0.001) NR3C1, tended to increase (P = 0.06) GHR, and decreased (P < 0.001) PRLR mRNA abundance. Compared with d 5 of lactation, d 17 of lactation increased PRLR (P < 0.001) and decreased GHR (P < 0.01). Expression of INR and FRAP1 did not differ when comparing either prepartum or d 17 of lactation with d 5 of lactation. Compared with d 17 of lactation, postweaning decreased (P < 0.001) PRLR, did not affect INSR, and increased both IGF-I and GHR (P < 0.05) mRNA abundance. From prepartum to d 17 of lactation, NR3C1 mRNA abundance was positively correlated with CSN2 (r = 0.85; P < 0.001) and LALBA mRNA abundance (r = 0.79; P = 0.002), whereas mRNA abundance of GHR tended to be positively correlated with that of IGF-I (r = 0.46; P = 0.06). In conclusion, expression of the genes NR3C1, PRLR, GHR, and IGF-I changed in the porcine mammary gland during the prepartum to postweaning periods, but only NR3C1 mRNA abundance was positively correlated with expression of CSN2 and LALBA.

Effect of dietary arginine supplementation and environmental temperature on sow lactation performance

Abstract The objective of this study was to investigate whether supplemental dietary arginine increases lactation performance in sows subjected to a hot environment. A total of 66 multiparous sows were allotted in a 2×3 factorial arrangement, consisting of two environments and three dietary treatments. Sows were maintained in a thermoneutral environment of 20°C (TN) or heat-stressed in a hot environment of 29.4°C (HS), starting on day 95 of gestation. From day 110 of gestation to weaning, sows were provided one of three corn–soybean meal based dietary treatments formulated to contain 0.96% arginine (1:1 arginine:lysine), 1.34% arginine (1.4:1 arginine:lysine), and 1.73% arginine (1.8:1 arginine:lysine), for control (C), medium (ME), and high (HI) dietary treatments, respectively. Respiration rate and rectal temperature increased in HS sows compared to TN sows (P 0.10) for either HS or TN sows. Arginine supplementation reduced feed intake (P

Transcript abundance of amino acid transporters, β-casein, and α-lactalbumin in mammary tissue of periparturient, lactating, and postweaned sows

The objective of these experiments was to test the hypothesis that transcript abundance of cationic AA transporter- and milk protein-encoding genes increase in the porcine mammary gland in response to higher lactation demand. Genes of interest included those encoding for the milk proteins α-lactalbumin (α-LA) and β-casein (β-CN; LALBA and CSN2, respectively), and AA transporter b(0,+)AT, y(+)LAT1, y(+)LAT2, ATB(0,+), CAT-1, and CAT-2b (SLC7A9, SLC7A7, SLC7A6, SLC6A14, SLC7A1, and SLC7A2, respectively). Mammary tissue was biopsied from 4 sows on d 110 of gestation (prepartum), on d 2 (early postpartum), on d 5 (early), and d 17 (peak) of lactation, and on d 5 after weaning (postweaning), and mRNA of target genes quantified by reverse transcription quantitative PCR. Compared with prepartum, CAT-1, ATB(0,+), y(+)LAT2, β-CN, and α-LA mRNA abundance was higher at early lactation, whereas compared with early lactation, only CAT-1 and α-LA mRNA abundance was higher at peak lactation. The CAT-2b, y(+)LAT1, and b(0,+)AT mRNA abundance did not differ when comparing either prepartum or peak lactation to early lactation. Compared with peak lactation, postweaning mRNA abundance of CAT-1, ATB(0,+), α-LA, and β-CN decreased, y(+)LAT2, CAT-2b, and b(0,+)AT remained unchanged, and y(+)LAT1 increased. The mRNA abundance of y(+)LAT2 increased from early postpartum to early lactation, and remained unchanged for CAT-1, ATB(0,+), α-LA, and β-CN. From prepartum to peak lactation, the mRNA abundance of CAT-1, y(+)LAT2, and ATB(0,+) was positively correlated with that of β-CN and α-LA. In conclusion, the expression of genes encoding for y(+)LAT1, CAT-2b, and b(0,+)AT remained unchanged in porcine mammary glands over prepartum to peak lactation period, whereas expression of genes encoding for CAT-1, ATB(0,+), and y(+)LAT2 was upregulated and positively correlated to expression of genes encoding for the mammary synthesized milk proteins β-CN and α-LA.

Effect of amino acids supply in reduced crude protein diets on performance, efficiency of mammary uptake, and transporter gene expression in lactating sows

To test the hypothesis that reduction in dietary CP concentration coupled with crystalline AA inclusion increases the efficiency of AA use for milk production, mammary AA arteriovenous concentration differences (A-V), AA transport efficiency (A-V/A × 100), and transcript abundance of AA transporters and milk protein genes were determined in lactating sows fed 1 of 3 diets containing 9.5% (Deficient), 13.5% (Ideal), or 17.5% (Standard) CP, with a similar profile of indispensable and dispensable AA. On d 7 and 18, arterial and mammary venous blood and mammary tissue were sampled postfeeding. Transcript abundance of AA transporters b(0,+)AT (SLC7A9), y(+)LAT2 (SLC7A6), ATB(0,+) (SLC6A14), CAT-1 (SLC7A1), and CAT-2b (SLC7A2) and milk protein β-casein (CSN2) and LALBA (α-lactalbumin) were determined using reverse transcription quantitative PCR. Piglet ADG increased curvilinearly (linear and quadratic, P < 0.03) with increasing percent CP from Deficient to Standard. On d 7, Lys and Arg A-V and transport efficiency increased quadratically (P < 0.05) with increasing percent CP. On d 18, Lys A-V tended to increase (linear, P = 0.08) with increasing percent CP. Increasing CP increased Ile and Val A-V on d 7 (linear, P = 0.05 and P = 0.08, respectively) and Leu and Val on d 18 (linear, P = 0.07 and P = 0.04, respectively). On d 7, plasma concentrations of branched chain AA (BCAA):Lys decreased quadratically (P < 0.05). Expression of genes SLC7A9, SLC7A6, SLC6A14, SLC7A1, SLC7A2, CSN2, and LALBA was unaffected by diet. In conclusion, decreasing the dietary CP from 17.5% to 13.5% with inclusion of crystalline AA did not affect piglet ADG, AA transporter, or milk protein gene expression but increased mammary transport efficiency and A-V of Lys and Arg on d 7 of lactation. This increase was associated with a decrease in plasma concentration of BCAA:Lys, suggesting a competitive mechanism between cationic and BCAA for transport of AA across mammary cells.

Linking our understanding of mammary gland metabolism to amino acid nutrition

Amino acids (AA) are not only building blocks of protein but are also key regulators of metabolic pathways in animals. Understanding the fate of AA is crucial to optimize utilization of AA for milk protein synthesis and, therefore, to reduce inefficiencies of nutrient utilization during lactation. By understanding the functional role of AA metabolism in mammary tissue, we can uncover pathways and molecular targets to improve AA utilization by mothers and neonates during the lactation period. The major objective of this article is to highlight recent advances in mammary AA transport, metabolism and utilization. Such knowledge will aid in refining dietary requirements of AA for lactating mammals, including women, sows and cows.

Protein quality and utilization of timothy, oat-supplemented timothy, and alfalfa at differing harvest maturities in exercised Arabian horses

To evaluate the protein quality and postgut N utilization of full-bloom timothy hay, oat-supplemented timothy-hay diets, and alfalfa hay harvested at different maturities, apparent whole tract N digestibility, urinary N excretion, and serum AA profiles were determined in light to moderately exercised Arabian horses. Six Arabian geldings (16.0 ± 0.3 yr; 467 ± 11 kg of BW) were randomly allocated to a 6 × 6 Latin square design. Diets included full-bloom timothy grass hay (G), G + 0.2% BW oat (G1), G + 0.4% BW oat (G2), mid-bloom alfalfa (A1), early-bloom alfalfa (A2), and early-bud alfalfa hay (A3). Forages were fed at 1.6% of the BW of the horse (as-fed). Each period consisted of an 11-d adaptation period followed by total collection of feces and urine for 3 d. Blood samples were taken on d 11 for analysis of serum AA concentrations. During the 3-d collection period, urine and feces were collected every 8 h and measured and weighed, respectively. Approximately 10% of the total urine volume and fecal weight per period was retained for N analyses. Fecal DM output was less (P < 0.05) in A1, A2, or A3 compared with G, G1, or G2. Apparent whole tract N digestibility was greater (P < 0.01) in A1, A2, and A3 compared with G, G1, or G2, and was greater (P < 0.05) in G1 and G2 compared with G. Nitrogen retention was not different from zero, and there were no differences (P > 0.05) in N retention among diets. Urinary N excretion and total N excretion were greater (P < 0.05) in A1, A2, and A3 compared with G, G1, or G2. Plasma concentrations for the majority of AA increased curvilinearly in response to feeding G, A1, A2, and A3 (quadratic, P < 0.05), with values appearing to maximize 2-h postfeeding. Although alfalfa N digestibility increased with decreasing harvest maturity, N retention did not differ and urinary volume and N excretion increased, indicating that postabsorptive N utilization decreased. In contrast, inclusion of oats at either 0.2 or 0.4% of the BW of the horse to timothy hay markedly enhanced N digestibility without increasing N excretion, indicating improvement in postgut N utilization. These findings indicate that feeding oat-supplemented timothy hay is more environmentally sustainable than feeding alfalfa to the horse at maintenance or under light to moderate exercise.