Effects of improved amino acid balance diet on lysine mammary utilization, whole body protein turnover and muscle protein breakdown on lactating sows.

BACKGROUND: The study objective was to test the hypothesis that low crude protein (CP) diet with crystalline amino acids (CAA) supplementation improves Lys utilization efficiency for milk production and reduces protein turnover and muscle protein breakdown. Eighteen lactating multiparous Yorkshire sows were allotted to 1 of 2 isocaloric diets (10.80 MJ/kg net energy): control (CON; 19.24% CP) and reduced CP with "optimal" AA profile (OPT; 14.00% CP). Sow body weight and backfat were recorded on d 1 and 21 of lactation and piglets were weighed on d 1, 14, 18, and 21 of lactation. Between d 14 and 18, a subset of 9 sows (CON = 4, OPT = 5) was infused with a mixed solution of 3-[methyl-2H3]histidine (bolus injection) and [13C]bicarbonate (priming dose) first, then a constant 2-h [13C]bicarbonate infusion followed by a 6-h primed constant [1-13C]lysine infusion. Serial blood and milk sampling were performed to determine plasma and milk Lys enrichment, Lys oxidation rate, whole body protein turnover, and muscle protein breakdown. RESULTS: Over the 21-d lactation period, compared to CON, sows fed OPT had greater litter growth rate (P < 0.05). Compared to CON, sows fed OPT had greater efficiency of Lys (P < 0.05), Lys mammary flux (P < 0.01) and whole-body protein turnover efficiency (P < 0.05). Compared to CON, sows fed OPT tended to have lower whole body protein breakdown rate (P = 0.069). Muscle protein breakdown rate did not differ between OPT and CON (P = 0.197). CONCLUSION: Feeding an improved AA balance diet increased efficiency of Lys and reduced whole-body protein turnover and protein breakdown. These results imply that the lower maternal N retention observed in lactating sows fed improved AA balance diets in previous studies may be a result of greater partitioning of AA towards milk rather than greater body protein breakdown.

Serum Cannabinoid 24 h and 1 Week Steady State Pharmacokinetic Assessment in Cats Using a CBD/CBDA Rich Hemp Paste.

Hemp based cannabinoids have gained popularity in veterinary medicine due to the potential to treat pain, seizure disorders and dermatological maladies in dogs. Cat owners are also using hemp-based products for arthritis, anxiety and neoplastic disorders with no studies assessing hemp cannabinoids, namely cannabidiol efficacy, for such disorders. Initial twenty-four pharmacokinetic and chronic dosing serum concentration in cats are sparse. The aim of our study was to assess 8 cats physiological and 24 h and 1-week steady state pharmacokinetic response to a cannabidiol (CBD) and cannabidiolic acid (CBDA) rich hemp in a palatable oral paste. Using a standard dose of paste (6.4 mg/CBD + CBDA 5.3 mg/gram) across 8 cats weighing between 4.2 and 5.4 kg showed an average maximal concentration of CBD at 282.0 ± 149.4 ng/mL with a half-life of ~2.1 ± 1.1 h, and CBDA concentrations of 1,011.3 ± 495.4 ng/mL with a half-life of ~2.7 ± 1.4 h, showing superior absorption of CBDA. After twice daily dosing for 1 week the serum concentrations 6 h after a morning dosing showed that the acidic forms of the cannabinoids were approximately double the concentration of the non-acidic forms like CBD and Δ9- tetrahydrocannabinol (THC). The results of this study compared to two other recent studies suggest that the absorption in this specific paste product may be superior to oil bases used previously, and show that the acidic forms of cannabinoids appear to be absorbed better than the non-acidic forms. More importantly, physical and behavioral examinations every morning after dosing showed no adverse events related to neurological function or behavioral alterations. In addition, bloodwork after 1 week of treatment showed no clinically significant serum biochemical alterations as a reflection of hepatic and renal function all remaining within the reference ranges set by the diagnostic laboratory suggesting that short-term treatment was safe.

Effects of a multi-strain Bacillus subtilis-based direct-fed microbial on immunity markers and intestinal morphology in diets fed to weanling pigs.

The objective of this experiment was to evaluate the effects of a multi-strain Bacillus subtilis-based direct-fed microbial (DFM) on nursery pig health as indicated by intestinal mucosal and blood plasma immunological markers and intestinal morphology. Eighty pigs, of equal number of barrows and gilts (initial BW: 7.0 ±â€…0.60 kg), weaned at 21 ±â€…1 d of age were randomly allotted to sixteen pens, with five pigs per pen. Two dietary treatments were implemented, a basal control (CON) and a basal control plus DFM (CDFM). Both diets were corn, soybean meal, and distillers dried grains based and were formulated to meet or exceed all nutritional requirements (NRC, 2012) and manufactured on site. Diets were fed for 42 d. On d 21 and 42 of the experiment, one pig per pen was randomly selected and euthanized, with equal number of males and females represented. Blood samples were collected prior to euthanasia for assessment of plasma concentrations of immunoglobulin A (IgA) and intestinal fatty acid binding protein. Segments of the gastrointestinal tract including duodenum, jejunum, ileum, ascending and distal colon were removed for analysis of intestinal morphology, and levels of interleukin 6, interleukin 10 (IL-10), and tumor necrosis factor alpha. Jejunal villus height was greater in the CDFM pigs as compared with CON pigs (P = 0.02) and ascending colon crypt depth tended to be greater on d 21 (P = 0.10). Compared to CON, CDFM significantly increased overall plasma IgA (P = 0.03) (0.58 vs. 0.73 0.05 mg/mL, respectively), while it tended to increase plasma IgA (P = 0.06) on d 21 (0.34 vs. 0.54 ±â€…0.07 mg/mL, respectively) and tended to increase overall IL-10 (P = 0.10) in the jejunum (113 vs. 195 ±â€…35 pg/mL, respectively). Addition of a multi-strain Bacillus subtilis-based DFM may have an early benefit to nursery pig health status, observed through specific changes in morphology and both systemic and localized immunological markers.

Developmental alterations of intestinal SGLT1 and GLUT2 induced by early weaning coincides with persistent low-grade metabolic inflammation in female pigs.

Early-life adversity (ELA) is linked with the increased risk for inflammatory and metabolic diseases in later life, but the mechanisms remain poorly understood. Intestinal epithelial glucose transporters sodium-glucose-linked transporter 1 (SGLT1) and glucose transporter 2 (GLUT2) are the major route for intestinal glucose uptake but have also received increased attention as modulators of inflammatory and metabolic diseases. Here, we tested the hypothesis that early weaning (EW) in pigs, an established model of ELA, alters the development of epithelial glucose transporters and coincides with elevated markers of metabolic inflammation. The jejunum and ileum of 90-day-old pigs previously exposed to EW (16 days wean age), exhibited reduced SGLT1 activity (by ∼ 30%, P < 0.05) than late weaned (LW, 28 days wean age) controls. In contrast, GLUT2-mediated glucose transport was increased (P = 0.003) in EW pigs than in LW pigs. Reciprocal changes in SGLT1- and GLUT2-mediated transport coincided with transporter protein expression in the intestinal brush-border membranes (BBMs) that were observed at 90 days and 150 days of age. Ileal SGLT1-mediated glucose transport and BBM expression were inhibited by the ß-adrenergic receptor (ßAR) blocker propranolol in EW and LW pigs. In contrast, propranolol enhanced ileal GLUT2-mediated glucose transport (P = 0.015) and brush-border membrane vesicle (BBMV) abundance (P = 0.035) in LW pigs, but not in EW pigs. Early-weaned pigs exhibited chronically elevated blood glucose and C-reactive protein (CRP) levels, and adipocyte hypertrophy and upregulated adipogenesis-related gene expression in visceral adipose tissue. Altered development of intestinal glucose transporters by EW could underlie the increased risk for later life inflammatory and metabolic diseases.NEW & NOTEWORTHY These studies reveal that early-life adversity in the form of early weaning in pigs causes a developmental shift in intestinal glucose transport from SGLT1 toward GLUT2-mediated transport. Early weaning also induced markers of metabolic inflammation including persistent elevations in blood glucose and the inflammatory marker CRP, along with increased visceral adiposity. Altered intestinal glucose transport might contribute to increased risk for inflammatory and metabolic diseases associated with early-life adversity.

Effects of a multi-strain Bacillus subtilis-based direct-fed microbial on weanling pig growth performance and nutrient digestibility.

A study was conducted to evaluate the effects of a multi-strain Bacillus subtilis-based direct-fed microbial (DFM) on growth performance and apparent nutrient digestibility of nursery pigs. Eighty pigs, of equal number of barrows and gilts (initial body weight: 7.0 ± 0.60 kg), were weaned at 21 ± 1 d and randomly allotted to 1 of the 16 pens, with 5 pigs per pen. Two dietary treatments were implemented, a basal control (CON) and a control plus DFM (CDFM). Both diets were corn, soybean meal, and distillers dried grains based. Diets were fed for 42 d and growth performance measures were recorded weekly. On days 21 and 42 of the experiment, one pig per pen, with equal number of males and females, was randomly selected and euthanized. Digestibility of nitrogen (N), amino acids (AA), and energy were evaluated within the duodenum, jejunum, ileum, and ascending and distal colon. Relative to CON, CDFM tended to increase ADG during week 2 (P = 0.08) and significantly increased ADFI during week 2 (P = 0.04) and week 3 (P = 0.02). In addition, CDFM decreased the gain to feed ratio (G:F) during week 6 relative to CON (P = 0.04). Within the jejunum, pigs fed the DFM had greater digestibility of tryptophan (P = 0.04) and cysteine (P = 0.04) and tended to have greater digestibility of lysine (P = 0.07), methionine (P = 0.06), and threonine (P = 0.08), relative to CON. The content pH in the ascending colon did not differ between CDFM and CON. Compared with CON, apparent total tract digestibility (ATTD) of energy did not differ from CDFM, whereas ATTD of nitrogen of CDFM was lower (P = 0.05). The addition of a multi-strain B. subtilis-based DFM appears to impact growth performance, AA, and N digestibility depending upon the location in the gastrointestinal tract, with primary AA differences occurring within the mid-jejunum.

Impact of arginine supplementation on serum prolactin and mRNA abundance of amino acid transporter genes in mammary tissue of lactating sows.

This study was conducted to test the hypothesis that supplemental dietary Arg to late-pregnant and lactating sows increases serum prolactin concentrations and mRNA abundance of SLC7A1, SLC7A2, and SLC6A14 in mammary parenchymal tissue. From day 108 of gestation and until day 21 of lactation, sows were fed a diet either supplemented with 0.10 g of l-Arg/kg body weight (BW) per day (n = 10, ARG) or 0.34 g of l-Glu/kg BW per day (n = 10, control). Litters were standardized to 10 piglets on day 1 of lactation and piglets were weighed on days 1, 7, 14, and 21 of lactation. Sow BW was recorded on day 108 of gestation and days 1, 10, and 21 of lactation. Lactation sow feed intake was recorded daily. Mammary parenchymal tissue was biopsied on day 5 of lactation to measure mRNA abundance SLC7A1, SLC7A2, and SLC6A14. On days 4 and 18 of lactation, blood samples were collected from sows at 2, 4, and 6 hr postfeeding to measure serum prolactin concentrations. Milk samples were collected on days 4, 10, and 18 of lactation to measure fat, lactose, urea N, and true protein concentrations. Sow BW, backfat, and feed intake over all sampling days did not differ between treatments. Piglet BW on d 1 tended to be greater for the ARG treatment than the control treatment (P = 0.12). Sow milk yield and composition (fat, protein, lactose, and urea N) and mammary mRNA abundance of candidate genes did not differ between the ARG and the control group. Compared to controls, serum prolactin concentrations tended to be greater (P = 0.08) in ARG sows on day 4 of lactation, and did not differ on day 18. Current findings show a potential beneficial effect of dietary supplementation with Arg to late-pregnant multiparous sows on BW of their piglets on day 1. Dietary Arg supplementation at a rate of 0.10 g/kg BW during late pregnancy and lactation tended to increase serum prolactin concentrations with no increase in mammary transcript abundance of SLC7A1, SLC7A2, and SLC6A14 in early lactation.

Reduced protein diet with near ideal amino acid profile improves energy efficiency and mitigate heat production associated with lactation in sows.

BACKGROUND: The study objective was to test the hypothesis that 1) lowering dietary crude protein (CP) increases dietary energetic efficiency and reduces metabolic heat associated with lactation, and 2) excessive dietary leucine (Leu) supplementation in a low CP diet decreases dietary energetic efficiency and increases metabolic heat associated with lactation. METHODS: Fifty-four lactating multiparous Yorkshire sows were allotted to 1 of 3 isocaloric diets (10.80 MJ/kg net energy): 1) control (CON; 18.75% CP), 2) reduced CP with a near ideal or optimal AA profile (OPT; 13.75% CP) and 3) diet OPT with excessive Leu (OPTLEU; 14.25% CP). Sow body weight and backfat were recorded on day 1 and 21 of lactation and piglets were weighed on day 1, 4, 8, 14, 18, and 21 of lactation. Energy balance was measured on sows during early (day 4 to 8) and peak (day 14 to18) lactation, and milk was sampled on day 8 and 18. RESULTS: Over 21-day lactation, sows fed OPT lost body weight and body lipid (P < 0.05). In peak lactation, sows fed OPT had higher milk energy output (P < 0.05) than CON. Sows fed OPTLEU tended (P = 0.07) to have less milk energy output than OPT and did not differ from CON. Maternal energy retention was lower (P < 0.05) in OPT and OPTLEU compared to CON sows, and did not differ between OPTLEU and OPT sows. Sows fed OPT had higher (P < 0.05) apparent energy efficiency for milk production compared to CON. Heat production associated with lactation was lower (P < 0.05) or tended to be lower (P = 0.082), respectively, in OPT and OPTLEU compared to CON sows. CONCLUSION: The OPT diet, in peak lactation, improved dietary energy utilization for lactation due to less urinary energy and metabolic heat loss, and triggered dietary energy deposition into milk at the expense of maternal lipid mobilization. Leucine supplementation above requirement may reduce dietary energy utilization for lactation by decreasing the energy partitioning towards milk, partially explaining the effectiveness of OPT diet over CON diets.

Feeding a reduced protein diet with a near ideal amino acid profile improves amino acid efficiency and nitrogen utilization for milk production in sows1,2.

Fifty-four lactating multiparous Yorkshire sows were used to test the hypothesis that feeding a reduced protein diet with a near ideal AA (NIAA) profile increases the biological utilization efficiency of N and essential AA (EAA) for milk production in part as a result of reduced dietary Leu concentration. Sows were fed 1 of 3 isocaloric diets containing the following concentration of CP (% as-fed, analyzed): 18.74 (Control: CON), 13.78 (Optimal: OPT), and 14.25 (Optimal + Leu: OPTLEU). The OPT and OPTLEU diets contained the same concentration of crystalline AA (CAA) to meet requirements of the limiting AA. Crystalline Leu was added to OPTLEU to contain the same SID Leu concentration as that of CON. Sows were weighed on days 1 and 21 of lactation and piglets on days 1, 4, 8, 14, 18, and 21 of lactation. Nitrogen retention was measured for 48 or 72 h between days 4 and 8 (early) and days 14 and 18 (peak) of lactation. Sow BW change and ADFI did not differ between diets. Litter growth rate (LGR) during early lactation did not differ between diets. At peak lactation, LGR was higher in sows fed OPT compared with CON (P < 0.05) and lower in sows fed OPTLEU compared with OPT (P < 0.05). In early and peak lactation, total N retention, and milk N output efficiency were greater in OPT (P < 0.01) and OPTLEU (P < 0.05) than CON. Compared with CON, overall biological efficiency of N, Arg, His, Ile, Leu, Phe, and Trp were greater (P < 0.05), whereas those of Lys, Met, Thr, and Val did not differ in sows fed OPT and OPTLEU, except for Leu which did not differ between OPTLEU and CON. Compared with OPT, only Leu and Met efficiency were lower (P < 0.01) and tended to be lower (P = 0.10), respectively, in sows fed OPTLEU. Reducing CP with a NIAA profile to attain the minimum Leu requirement maintained overall lactation performance, improved utilization efficiency of N, Arg, His, Ile, Leu, Phe + Tyr, and Trp for milk production, and maximized efficiency of Ile, Leu, Lys, Met + Cys, Phe + Tyr, Thr, Trp, and Val. Addition of Leu did not reduce N and EAA utilization efficiency. This study provides revised and novel maximum biological efficiency value (MBEV) for Ile (65.4), Leu (75.1), Lys (63.2), Met + Cys (78.2), Phe + Tyr (69.5), Thr (71.0), Trp (70.1), and Val (57.0). These MBEV can be used to more accurately predict the requirement for those AA during lactation.

Nitrogen utilization of lactating sows fed increasing dietary protein1.

The objectives of the study were 1) to quantify dietary N utilized for milk N and N loss in urine and feces, in sows fed increasing dietary CP with a constant amount of Lys, Met, Thr, and Trp to meet their standardized ileal digestible (SID) requirement and 2) to determine the optimal dietary CP concentration based on dietary N utilization for milk production. Seventy-two sows were fed 1 of 6 dietary treatments, formulated to increase the SID CP as followed: 11.8, 12.8, 13.4, 14.0, 14.7, and 15.6% and formulated to be isocaloric (9.8 MJ NE/kg). Diets were fed from day 2 after parturition until weaning at day 28 (± 3 d). Litters were equalized to 14 piglets and weighed within 48 h following parturition. Sows were weighed and back fat scanned, at day 18 (± 3 d) and day 28 (weaning; ± 3 d). Litter weight was recorded at day 11, 18 (± 3 d), and 28 (± 3 d). Nitrogen balances were conducted on approximately day 4, 11, and 18 (± 3 d). Daily milk yield was estimated from recorded litter gain and litter size. To calculate sows mobilization of fat and protein, body pools of fat and protein were estimated by D2O (deuterated water) enrichment on day 4 and 18 (± 3 d). No linear, quadratic, or cubic effects of increasing dietary CP was observed for sows total feed intake, sow BW, body pools of protein and fat, protein and fat mobilization, total milk yield, and piglet performance. The protein content in milk increased linearly with increasing dietary CP in week 1 (P < 0.05), week 2 (P < 0.05), and week 3 (P < 0.001). Urine production did not differ among treatments and N output in urine increased linearly with increasing dietary CP concentration in week 1 (P = 0.05), week 2 (P < 0.001), and week 3 (P < 0.001). Urine N excretion relative to N intake increased linearly with increasing dietary CP (P < 0.001). Milk N utilization relative to N intake decreased linearly from 77.8% to 63.1% from treatment 1 through 6 (P < 0.001). Corrected milk N utilization decreased from 68.6% to 64.2% from treatment 1 through 6 (P < 0.05). In conclusion, a low dietary CP concentration for lactating sows with supplemented crystalline AA improved the efficiency of dietary N utilization and reduced the N output in urine without affecting lactation performance.

Technical note: development of an indirect calorimetry system to determine heat production in individual lactating sows1.

The ability to determine total heat production (THP) in individual sows and litters can be logistically difficult and often requires the use of multiple animals to generate data on a per room basis. Furthermore, these systems may be costly to construct, precluding their use by many researchers. Therefore, the objective was to develop a low-cost indirect calorimetry system to determine THP in individual lactating sows and litters. Six indirect calorimeters were constructed to house 1 sow and litter in a crate throughout farrowing and a 21-d lactation period. Farrowing crates were placed within a high-density polyethylene pan filled with water and then a polyvinyl chloride frame was constructed around the crate. The frame provided a structure to hold the inlet and outlet air pipes, feed and water inlets, air circulation fans, and a polyethylene plastic sheet that was secured at the bottom of the frame and submerged under water to maintain an air tight seal. Chamber accuracies for O2 and CO2 were evaluated by ethanol combustion. One week pre-farrowing, 6 pregnant multiparous sows (parity 2.9 ± 0.9; 218.3 ± 38.6 kg BW) were housed individually in each farrowing crate and the calorimeters were maintained at thermoneutral conditions (20.9 ± 2.6°C and 43.7 ± 18.6% relative humidity) throughout lactation. On lactation day 4, 8, 14, and 18, indirect calorimetry was performed on all sows and their litters, as well as 2 piglets from a sentinel litter to determine THP and the respiratory quotient (RQ). Sentinel piglet data were used to estimate THP and RQ for the sows independent of the litter. Sow + litter THP (kcal/h) increased (P = 0.01; 16.6%) on day 8 compared to day 4 and was greater (27.3%) on day 14 and day 18 compared to day 4 and day 8. Sow THP was greater (P = 0.01) on day 8 (401.19 ± 17.15 kcal/h) and day 14 (430.79 ± 12.42 kcal/h) compared to day 4 (346.16 ± 16.62 kcal/h), and was greater on day 14 compared to day 8, and on day 18 (386.16 ± 20.02 kcal/h) compared to day 14. No sow + litter RQ differences (P = 0.21; 1.02 ± 0.04) were detected by day of lactation. However, sow RQ was reduced (P = 0.01) on day 14 (0.98 ± 0.02) compared to day 4 (1.03 ± 0.03), day 8 (1.02 ± 0.02), and day 18 (1.04 ± 0.03). In summary, this cost-effective system (total cost: $1,892 USD) can allow researchers to accurately evaluate THP in individual lactating sows and their litters.

Effect of dietary protein intake on energy utilization and feed efficiency of lactating sows.

The objective of the current study was to quantify loss of energy in feces, urine, heat, and milk, to evaluate feed efficiency and to evaluate optimal ratio of dietary CP to energy for lactating sows fed increasing dietary CP. A total of 72 sows were included in the experiment from day 2 after parturition until weaning at day 28. Sows were allocated to 6 dietary treatments formulated to be isocaloric (9.8 MJ NE/kg) and increasing standardized ileal digestible (SID) CP (11.8, 12.8, 13.4, 14.0, 14.7, and 15.6% SID CP). Sows were weighed and back fat scanned within 2 d after farrowing, at days 18 ± 3 and 28 ± 3. Litters were standardized to 14 piglets within 2 d after farrowing and weighed at day 1 or 2 and at days 11, 18, and 28 (within ± 3 d). Feed intake (feed supply minus residue) was registered, and milk, urine, and fecal samples were collected at days 4, 11, and 18 (within ± 3 d). Sow milk yield was estimated from litter gain and litter size, and sow heat production was calculated factorially. On days 4 and 18 (±3 d), sows were enriched with D2O (deuterated water) to estimate body protein and fat pool size. Overall, sow BW loss, back fat loss, fat and protein mobilization, litter size, and piglet performance were not affected by diets, except for sows fed treatment 5, which had lower ADFI and lower milk production, and a tendency to lower piglet ADG compared with the remaining treatment groups (P < 0.01, P = 0.03, P =0.08, respectively). Relative to GE intake, the energy excreted in urine increased from 3.3% to 5.3% (P < 0.001), whereas energy lost as heat increased numerically from 54.5% to 59.0% with increasing dietary CP. The feed efficiency as evaluated by NE corrected for body mobilization peaked when sows were fed at their requirement (treatment 2; 12.8% SID CP; P = 0.01), whereas the feed efficiency was 1% lower for treatment 1, whereas it was 3% to 6% lower for treatments 3 through 6. In conclusion, energy loss in urine and likely also energy lost as heat increase if the dietary protein to energy ratio is unbalanced, and evaluating feed efficiency of lactating sows by correcting for body mobilization seems to be a promising approach to improve sow feeding in the future.

Whole-body nitrogen utilization and tissue protein and casein synthesis in lactating primiparous sows fed low- and high-protein diets.

Twenty-eight lactating Yorkshire and Yorkshire × Landrace primiparous sows were used to test the hypothesis that feeding a diet with reduced CP concentration and supplemented with crystalline AA (CAA) does not decrease milk protein yield and litter growth but improves apparent N utilization for milk protein production. Sows were assigned to 1 of 2 dietary treatments: 1) control (CON; 16.2% CP; analyzed content) or 2) low CP with CAA to meet estimated requirements of limiting AA (LCP; 12.7% CP) over a 17-d lactation period. A N balance was conducted for each sow between days 13 and 17 of lactation. On day 17, a 12-h primed continuous infusion of l-[ring-2H5]-Phe was conducted on 12 sows (n = 6) with serial blood and milk sampling to determine plasma AA concentrations and Phe enrichment, and milk casein synthesis, respectively. Thereafter, sows were sacrificed and tissues were collected to determine tissue protein fractional synthesis rates (FSR). Litter growth rate and milk composition did not differ. Sows fed the LCP diet had reduced N intake (122.7 vs. 153.2 g/d; P < 0.001) and maternal N retention (13.5 vs. 24.6 g/d; P < 0.05) and greater apparent efficiency of using dietary N intake for milk production (85.1% vs. 67.5%; P < 0.001). On day 17 of lactation, all plasma essential AA concentrations exhibited a quartic relationship over time relative to consumption of a meal, where peaks occurred at approximately 1- and 4-h postprandial (P < 0.05). Protein FSR in liver, LM, gastrocnemius muscle, mammary gland, and in milk caseins did not differ between treatments. Feeding primiparous sows with a diet containing 12.7% CP and supplemented with CAA to meet the limiting AA requirements did not reduce milk protein yield or piglet growth rate and increased the apparent utilization of dietary N, Arg, Leu, Phe+Tyr, and Trp for milk protein production. The improved apparent utilization of N and AA appears to be related exclusively to a reduction in N and AA intake.

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.

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.

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.

Mammary arteriovenous differences of glucose, insulin, prolactin and IGF-I in lactating sows under different protein intake levels.

Mammary uptake of nutrients is dependent on their availability in the circulation but the role of hormones in that process is not known. Arteriovenous differences (AVD) of glucose and key hormones across the mammary glands were therefore determined in sows fed varying levels of protein. Sixteen lactating sows (four/dietary treatment) were fed a 7.8, 13.0, 18.2 or 23.5% crude protein (CP) isocaloric diet throughout lactation and their litters were standardized to 11 pigs within 48 h of birth. The anterior main mammary vein and a carotid artery were cannulated on day 4+/-1 of lactation and blood samples were collected every 30 min over 6h on days 10, 14, 18 and 22 of lactation to measure glucose, insulin, IGF-I, and prolactin (PRL) concentrations. Amino acid data from these sows were previously published and used here to determine residual correlations. Dietary treatments had no effect on any of the insulin or PRL variables measured (P>0.1) and, on day 18 only, IGF-I AVD was greater (P=0.05) for sows on the 23.5% compared to the 18.2% diet. On days 18 and 22, sows fed the 13% CP diet had greater arterial, venous and AVD glucose concentrations than sows fed other diets (P<0.05). Total arterial amino acid concentrations were correlated to arterial insulin (P<0.001) and PRL (P<0.05) concentrations, but not to those of IGF-I (P>0.1). Mammary AVD for total (P<0.001) and essential amino acids (P<0.05) were correlated to arterial concentrations of insulin, but not to those of IGF-I (P>0.1) or PRL (P>0.1). Mammary AVD of both total (P<0.01) and essential (P<0.05) amino acids were also correlated to mammary PRL AVD. In conclusion, dietary protein level did not affect mammary AVD and circulating lactogenic hormone concentrations. Yet, amino acid utilization by the sow mammary gland seems to be regulated via both circulating insulin concentrations and PRL binding to and uptake by porcine mammary cells.

The amino acid need for milk synthesis is defined by the maximal uptake of plasma amino acids by porcine mammary glands.

To define dietary indispensable amino acid (IAA) needs for milk synthesis by the mammary glands (MG), 16 lactating sows were fed 1 of 4 isocaloric diets varying in protein concentrations (from 78 to 235 g/kg) with an ideal amino acid (AA) pattern. On d 9, 13, 17, and 21 of lactation, blood samples were obtained simultaneously from a carotid artery and the main mammary vein every 30 min over 6 h. A quadratic regression model of the log mammary arteriovenous difference (AVD) of plasma IAA (y) against daily intake of dietary IAA (X) was established. First, the reverse log intercept, defined as the mammary AVD at zero dietary AA supply, was used to quantify the contribution of endogenous IAA. The quantification was validated by body N balance coupled with AA composition analysis. Then, the estimated vertex (y(max), X(i)) was used in 2 aspects: 1) The maximal mammary uptake of plasma IAA, quantified by multiplying the maximal mammary AVD and plasma flow rate, was considered the physiological IAA need for milk synthesis. 2) Corresponding to the y(max), dietary IAA intake (X(i)) would represent the total dietary IAA requirement, i.e., the sum of maintenance need and milk synthesis need after adjustment for body weight loss. Thus, dietary IAA needs for milk synthesis were derived. Moreover, the estimate of lysine need for milk synthesis in this study was identical to an estimate obtained from multiple regression analysis of feeding trial data. We conclude that dietary IAA needs for milk synthesis can be quantified by the maximal uptakes of plasma IAA by porcine MG.

Amino acid availability affects amino acid flux and protein metabolism in the porcine mammary gland.

A kinetic model was used to examine transmembrane flux kinetics of lysine, methionine and valine across the porcine mammary gland (MG) under dietary amino acid (AA) limiting, adequate and excess conditions. Lactating sows (3 per treatment) were offered three diets: lysine-deficient [LD, 4.9 lysine and 9.9 valine (g/kg diet)], adequate (Control, 9.7 and 10.2) and valine-excess (VE, 9.8 and 13.4). On d 18 of lactation, 2-(15)N-lysine, 5-methyl-(2)H(3)-methionine and 1-(13)C-valine were infused into a jugular vein for 20.5 h. Milk and arterial and mammary venous blood samples were collected at 2- and 1-h intervals, respectively. Compared with Control, milk yield and litter growth rate decreased (P < 0.05) in sows fed the LD diet. Model estimates of mammary protein synthesis (PS), breakdown (PB) and net PS decreased (P < 0.05) in sows fed the LD diet. Net uptake of lysine decreased (P < 0.05) in sows fed the LD diet as a result of decreases in inward and outward transport of lysine. Inward transport of methionine tended to be reduced (P < 0.10) in sows fed the LD diet, resulting in a decrease in net methionine uptake. In sows fed the VE diet, PB was reduced (P < 0.05) and PS unchanged compared with Control. Outward transport of valine and net lysine uptake were reduced (P < 0.05), but net valine uptake was unchanged in sows fed the VE diet compared with Control. In conclusion, the kinetic model provided estimates of PS that were similar to empirical measurements of milk protein output and mammary protein accretion. Transport of lysine and methionine by the porcine MG is closely linked to regulation of mammary PS. Lysine availability has little effect on the transmembrane flux of valine.