Effects of dietary amino acid supplementation on measures of whole‐body and muscle protein metabolism in aged horses

The objective of this study was to examine markers of whole‐body and muscle protein metabolism in aged horses fed a diet typical for North American aged horses, supplemented with amino acids. In a replicated Latin square design, six aged horses (20 ± 1.1 years) were studied while receiving each of three isocaloric, isonitrogenous diets, a control treatment concentrate (CON; 100 mg/kg^?1 BW day^?1 lysine, 84 mg kg^?1 day^?1 threonine, 51 mg kg^?1 day^?1 methionine), LYS/THR (134 mg kg^?1 BW day^?1 lysine, 110 mg kg^?1 BW day^?1 threonine, 52 mg kg^?1 BW day^?1 methionine) and LYS/THR/MET (132 mg kg^?1 BW day^?1 lysine, 112 mg kg^?1 BW day^?1 threonine, 62 mg kg^?1 BW day^?1 methionine). In each 15‐days period, urine and faeces were collected for assessment of nitrogen balance. Blood samples were collected before and after feeding for analysis of plasma urea nitrogen (PUN), glucose, insulin and plasma amino acid concentrations. Skeletal muscle samples were collected for measurement of proteins associated with muscle protein synthesis and degradation, and horses underwent stable isotope infusion procedures for comparison of differences in whole‐body rates of protein synthesis and degradation. There was no effect of treatment on relative abundance of proteins involved in protein synthesis, nitrogen retention or phenylalanine kinetics. PUN concentrations tended to be higher for LYS/THR (p = 0.054) and were higher for LYS/THR/MET (p = 0.0056) than for CON. Atrogin‐1 abundance tended to be higher in the post‐absorptive state for the CON treatment (p = 0.07), indicating that amino acid supplementation resulted in less muscle protein degradation when horses were in the post‐absorptive state. However, lack of differences in nitrogen retention and phenylalanine kinetics indicated that whole‐body protein metabolism was not improved, and higher PUN concentrations in the supplemented diets suggest that the supplemented amino acids may have been catabolized. Amino acid availability was not limiting protein synthesis in the sedentary aged horses in this study when fed the CON diet.     

Dietary levels of protein and free amino acids affect pancreatic proteases activities,amino acids transporters expression and serum amino acid concentrations in starter pigs

The dietary contents of crude protein and free amino acids (AA) may affect the protein digestion and AA absorption in pigs. Trypsin and chymotrypsin activities, AA serum concentrations and expression of AA transporters in the small intestine of pigs fed a low protein, AA‐supplemented (19.2%, LPAA) or a high protein (28.1%, HP), wheat‐soybean meal diet were measured in two 14‐d trials. The LPAA diet contained free L‐Lys, L‐Thr, DL‐Met, L‐Leu, L‐Ile, L‐Val, L‐His, L‐Trp and L‐Phe. All pigs were fed the same amount of feed (890 and 800 g/d for trial 1 and 2 respectively). In trial 1, samples of mucosa (duodenum, jejunum and ileum) and digesta (duodenum and jejunum) were collected from 14 pigs (17.2 ± 0.4 kg); in trial 2, blood samples were collected from 12 pigs (12.7 ± 0.3 kg). The trypsin and chymotrypsin activities in both intestinal segments were higher in pigs fed the HP diet (p < 0.01). Trypsin activity was higher in jejunum than in duodenum regardless the dietary treatment (p < 0.05). Pigs fed the LPAA diet expressed more b^0,+AT in duodenum, B⁰AT1 in ileum (p < 0.05), and tended to express more y⁺LAT1 in duodenum (p = 0.10). In pigs fed the LPAA diet, the expression of b^0,+AT was higher in duodenum than in jejunum and ileum (p < 0.01), but no difference was observed in pigs fed the HP diet. Ileum had the lowest b^0,+AT expression regardless the diet. The serum concentrations of Lys, Thr and Met were higher in LPAA pigs while serum Arg was higher in HP pigs (p < 0.05). Serum concentrations of AA appear to reflect the AA absorption. In conclusion, these data indicate that the dietary protein contents affect the extent of protein digestion and that supplemental free AA may influence the intestinal site of AA release and absorption, which may impact their availability for growth of young pigs.     

Effect of ractopamine hydrochloride and zilpaterol hydrochloride on growth,diet digestibility,intake and carcass characteristics of feedlot lambs

The effects of the β-adrenergic agonists ractopamine hydrochloride (RH; 0.35, 0.70 and 1.05 mg kg^− 1 of BW d^− 1) and zilpaterol hydrochloride (ZH; 0.10, 0.20 and 0.30 mg kg^− 1 of BW d^− 1) on growth performance and carcass characteristics were determined in 84 Dorper × Katahdin lambs (12 lambs per treatment), that were randomly assigned to a complete block design during a 42-day feeding trial. Lambs were fed a corn grain-based diet (18.71% CP and 12.9 MJ/kg ME). Nutrient digestibility of diets and blood serum metabolites were also determined. There were no significant (P > 0.05) differences in growth characteristics by effect of ZH or RH administration. However, lambs final weight, total weight gain and ADG increased linearly (P < 0.05) as levels of both β-adrenergic agonist increased. RH or ZH administration did not affect feed efficiency, diet digestibility or particular blood serum metabolites of lambs. Carcass characteristics of lambs consuming ZH were significantly better (P < 0.01) than RH or control lambs; RH produced significant linear response on carcass weight, dressing percentage, longissimus muscle area, carcass conformation and quality grade, and improved quadratically (P < 0.05) fat thickness and USDA yield grade of lamb carcasses. On the other hand, increasing levels of ZH decreased linearly (P > 0.01) fat thickness and improved (P > 0.05) USDA yield grade and carcass quality grade. Both β-adrenergic agonists improved carcass characteristics; although greater improvements were obtained with ZH than RH for most carcass characteristics.     

Omega-3 Fatty Acid Supplementation Affects Selected Phospholipids in Peripheral White Blood Cells and in Plasma of Full-Sized and Miniature Mares

Dietary omega-3 fatty acids (n-3 PUFA), notably eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), impart health benefits in humans and animals. In horses, dietary n-3 PUFAs elevate EPA and DHA and may promote anti-inflammatory effects. No reports document effects of dietary n-3 PUFA on fatty acyl components of circulating and cellular phospholipids in horses nor whether responses to dietary n-3 PUFA are similar among horse breeds. Ten Quarter Horse and 10 American Miniature Horse mares were assigned to n-3 PUFA (64.4 mg· kg body weight [BW]⁻¹·d⁻¹) or control diet for 56 days. Blood was sampled at 0, 28, and 56 days. Apparent phospholipid molecular species from several classes (phosphatidylcholine [PC]; “ether-linked” phosphatidylcholine [i.e., alk(en)yl, acyl glycerophosphocholine] [ePC]; phosphatidylethanolamine [PE]; phosphatidylinositol [PI]; and phosphatidylserine [PS]) were determined in plasma and peripheral blood mononuclear cells (PBMC) by mass spectrometry. Statistical analysis showed that six phospholipid species had diet × day interactions (P < .05) for both plasma and PBMC. Further evaluation of these species demonstrated that the mole percentage of PC(38:6), PC(40:7), PC(42:10), PE(38:5), PE(40:6), and PE(40:7) (where x:y represents total acyl carbon:total carbon-carbon double bonds) in both plasma and PBMC phospholipids was elevated in horses fed n-3 PUFA (P < .001 for all). Analysis of the acyl product ions revealed that these contained an acyl chain of mass consistent with an n-3 PUFA. Thus, supplementation increased n-3 PUFA in selected plasma and PBMC phospholipids. The absence of breed effects suggests that miniature and full-size horses responded similarly to dietary treatment.     

A Comparison of Three Conventional Horse Feeders with the Pre-Vent Feeder

This study compared a feeder with molded cups on the bottom (Pre-Vent feeder) with a commonly used rubber tub and hanging bucket feeder to determine differences in time spent eating and feed wastage. Nine Quarter Horse geldings were fed a 12% crude protein pellet diet at 0.75% body weight twice daily from one of the three feeders twice daily for 3 days, and then switched to the next feeder, following a 3 × 3 replicated Latin square design (n = 9). The horses spent more time eating from the cup feeders (31.15 ± 1.43 minutes) than from bucket (19.39 ± 0.42 minutes) and tub (18.87 ± 0.49 minutes, P < .0001) feeders. When fed from cup feeder, horses dropped significantly less feed (3.2 ± 0.52%) of their ration than when fed from bucket (10.2 ± 1.75%) and from tub (7.0 ± 1.32%, P = .001) feeders. When the most wasteful horse was fed from the cup feeder, he lost a mean of 8.7% of his ration, compared with 32.8% when fed from the bucket, and 26.2% when fed from the tub feeders. The cup design is useful for increasing time spent eating and reducing feed wastage.     

Determination and prediction of the apparent and standardized ileal amino acid digestibility in cottonseed meals fed to growing pigs

This experiment was conducted to evaluate the chemical composition and apparent ileal digestibility (AID) and standardized ileal digestibility (SID) of amino acids (AA) in cottonseed meals (CSM) and to develop prediction equations for estimating AA digestibility for growing pigs based on the chemical composition and AA content of CSM. 10 CSM were collected from 10 provinces in China. 11 barrows (initial body weight: 34.4 ± 1.9 kg), fitted with an ileal T‐cannula, were allotted to 6 × 11 Youden square with 6 periods and 11 diets. The diets included one N‐free diet and 10 CSM test diets containing 40% CSM as the sole source of AA. The nitrogen‐free diet was used to measure the basal endogenous losses of CP and AA. The AID and SID for crude protein (CP), Lys, Met, Trp, and Thr among the 10 CSM differed (p < 0.05). With R² values exceeding 0.30, significant linear regression equations for CP, Lys, and Thr were obtained. The best fit equations for predicting the AID and SID of Lys were: AID of Lys = 82.94–0.65 neutral detergent fiber, with R² = 0.44, residual standard deviation (RSD) = 4.03 and p = 0.04; and SID of Lys = 135.34–1.01 neutral detergent fiber + 34.27 Thr – 58.06 Trp – 84.93 Met, with R² = 0.90, RSD = 1.42 and p = 0.01. In conclusion, the results of AID, SID and prediction equations could be used to evaluate the digestibility of CSM in growing pigs.     

Use of encapsulated L-lysine-HCl and DL-methionine improves postprandial amino acid balance in laying hens

The supplementation of dietary limiting amino acids (AA) with crystalline AA makes the use of low-protein diets an option in poultry production. The differing absorption rates of crystalline and protein-bound AA may lead to temporally imbalanced AA in the postabsorptive period. In this study, two experiments were conducted to evaluate the effect of encapsulated L-lysine-HCl (L-Lys-HCl) and DL-methionine (DL-Met) on the laying performance of hens. In exp. 1, a total of 135 forty-seven-wk-old Hy-Line Brown hens were subjected to three dietary treatments for 8 wk: basal diet supplemented with 0.14% L-Lys-HCl and 0.17% DL-Met to satisfy the NRC (1994) total Lys and Met recommendation (control) and basal diet supplemented with encapsulated L-Lys-HCl and DL-Met at the levels of 60% (60CLM, 0.084% L-Lys-HCl and 0.102% DL-Met) or 80% of control (80CLM, 0.112% L-Lys-HCl and 0.136% DL-Met), respectively. In exp. 2, 24 fifty-five-wk-old Hy-Line Brown hens were individually reared in cages and subjected to the same treatments as in exp. 1. The plasma concentrations of free AA and nitrogen metabolites were measured 2, 4, and 6 h after fed. The results showed that dietary AA treatment had no significant influence on body weight (BW), feed intake, laying rate, egg weight, egg mass, or feed efficiency. The expression levels of AA transporters CAT-1, y⁺LAT1, b^0,+AT, B⁰AT, rBAT, EAAT3, and PepT1 in the duodenum, jejunum, and ileum were not influenced (P > 0.05) by dietary treatment. There was an interaction of dietary AA treatment and time (P < 0.05) and the 80CLM hens exhibited higher concentrations of Lys (P < 0.05) than the controls at 2-h time point. In contrast, plasma Met concentration was not influenced (P > 0.05), while Cys was reduced in the 60CLM hens at every time point. The 80CLM hens had higher taurine concentrations than those receiving the control diet at every postprandial time point. In conclusion, these findings demonstrate that by using encapsulated form, the supplemental levels of synthetic L-Lys-HCl and DL-Met can be effectively reduced by approximately 20% with no negative effect on laying performance. The result suggests that encapsulated Lys and Met may ameliorate the postabsorptive AA balance and contribute to the reduced dietary AA supplemental levels.     

Rough Agave Flowers as a Potential Feed Resource for Growing Goats

The objective of this study was to evaluate the effect of different levels of rough agave (Agave scabra Ortega) flowers on dry matter intake (DMI), average daily gain (ADG), volatile fatty acid (VFA) production in the rumen, and particular serum metabolites and minerals of native × dairy growing goats (Capra hircus L.). Forty female goats with an initial weight of 11.1 ±  kg (mean ± SD) were used in a completely randomized design experiment that lasted for 84 d. Goats were fed a completely mixed ration (30% roughage, 70% ground corn [Zea mays L.] and soybean [Glycine max {L.} Merr] meal). Treatments consisted of offering goats (4 pens · group⁻¹, 2 goats · pen⁻¹) air-dry rough agave flowers, which replaced alfalfa (Medicago sativa L.) hay at 0% (control; T0), 25% (T25), 50% (T50), 75% (T75), and 100% (T100) of the of the roughage portion of the diet. Values of nutritional parameters for rough agave flowers were in vitro organic matter digestibility, 493 g · kg⁻¹; crude protein, 115 g · kg⁻¹; and metabolizable energy, 6.29 MJ · kg⁻¹ DMI. There were differences (P < 0.05) in ADG (range, 108–155 g · d⁻¹) between diets. Goats fed T0 had higher (P < 0.05) gains than goats fed T50 and T100. DMI was not affected by dietary treatments (range, 3.4% to 3.6% of body weight). Feed conversion ratio (FCR, defined as DMI/ADG) increased (P < 0.05) 27% with total substitution of alfalfa by rough agave flowers, in comparison with T0. Lower (P < 0.05) values of total VFA were obtained with T100, in comparison with all other dietary treatments. These results demonstrated that totally replacing alfalfa with rough agave flowers in diets did not affect DMI but decreased AGD and compromised FCR. Thus, rough agave flowers have the potential to partially replace alfalfa in diets for growing goats.     

Postprandial Blood Glucose and Insulin Responses of Horses to Feeds Differing in Soluble Fiber Concentration

In humans, the consumption of soluble fibers reduces glycemic response after a meal. We hypothesized high soluble fiber diets would reduce and delay postprandial glucose and insulin responses in horses. In a 4 × 4 Latin square design experiment, four Quarter Horse geldings were adapted to diets containing orchardgrass hay (ORCH) or ORCH with 1 of 3 treatment ingredients: molassed sugar beet pulp (BEET), almond hulls (HULL), or steam-crimped oats (OATS). Blood was serially sampled for 6 hours after feeding 0.15% body weight (BW) of the treatment ingredient (meal test) or 1.1 g starch/kg BW from oats plus the treatment ingredient (starch test) to evaluate glycemic and insulinemic responses. Glycemic response during the meal test peaked between 60 and 90 min after feeding (P < .05) and tended to be altered by diet (P = .071) and diet × time (P = .076). Serum insulin was affected by diet (P = .008), time (P < .001), and diet × time (P < .001) during the meal test, with concentrations lower in ORCH compared with BEET and OATS (P < .05). In the starch test, glucose was lower (P < .05) in ORCH and HULL compared with BEET and insulin was lower (P = .046) in ORCH compared with BEET. In both tests, horses took longer (P < .05) to consume HULL, likely influencing postprandial responses. Future research integrating the functional properties of feeds with physiological responses will be necessary to elucidate how soluble fiber affects postprandial glucose metabolism in horses.     

Effect of L‐lysine on expression of selected genes,serum concentration of amino acids,muscle growth and performance of growing pigs

Lysine (Lys) is the first limiting amino acid (AA) in most feed formulations for pigs and most abundant, along with leucine, in muscle proteins. An experiment was conducted with 17 pigs (17.7 ± 0.05 kg initial BW) to identify a role of dietary Lys in the control of protein synthesis in pigs. Fourteen pigs were randomly assigned to one of the two wheat‐based dietary treatments: Lys‐deficient, 3.0 g/kg (DEF) and Lys‐adequate, 10.8 g/kg (ADE). Samples from jejunum mucosa, liver, Longissumus and Semitendinosus muscles, and blood were collected. The other three pigs were sacrificed at the beginning of the trial to measure basal carcass composition. Weight gain, gain:feed ratio, Lys intake and loin eye area were greater in ADE than in DEF pigs (p < 0.01). Muscle‐related carcass characteristics were better, and myosin heavy chain IIb expression (MyHC IIb) in Semitendinosus was higher in ADE than in DEF pigs. Expression of AA transporters CAT‐1 was lower (p < 0.05), serum Lys was higher and serum Val was lower in pigs fed the ADE diet. The higher muscularity, MyHC IIb expression in Semitendinosus muscle and Lys serum of pigs fed the ADE diet suggest that Lys increases growth rate not only by functioning as protein construction unit but also as potential control of the protein synthesis process.     

Sainfoin (Onobrychis viciifolia) silage in dairy cow rations reduces ruminal biohydrogenation and increases transfer efficiencies of unsaturated fatty acids from feed to milk

The effects of replacing grass silage by sainfoin silage in a total mixed ration (TMR) based diet on fatty acid (FA) reticular inflow and milk FA profile of dairy cows was investigated. The experiment followed a crossover design with 2 dietary treatments. The control diet consisted of grass silage, corn silage, concentrate and linseed. In the sainfoin diet, half of the grass silage was replaced by a sainfoin silage. Six rumen cannulated lactating multiparous dairy cows with a metabolic body weight of 132.5 ± 3.6 kg BW^0.75, 214 ± 72 d in milk and an average milk production of 23.1 ± 2.8 kg/d were used in the experiment. Cows were paired based on parity and milk production. Within pairs, cows were randomly assigned to either the control diet or the sainfoin diet for 2 experimental periods (29 d per period). In each period, the first 21 d, cows were housed individually in tie-stalls for adaptation, then next 4 d cows were housed individually in climate-controlled respiration chambers to measure CH₄. During the last 4 d, cows were housed individually in tie stalls to measure milk FA profile and determine FA reticular inflow using the reticular sampling technique with Cr-ethylenediaminetetraacetic acid disodium salt dihydrate (EDTA) and Yb-acetate used as digesta flow markers. Although the dietary C18:3n-3 intake was lower (P = 0.025) in the sainfoin diet group, the mono-unsaturated FA reticular inflow was greater (P = 0.042) in cows fed the sainfoin diet. The reticular inflow of trans-9, trans-12-C18:2 and cis-12, trans-10 C18:2 was greater (P ≤ 0.024) in the sainfoin diet group. The cows fed sainfoin diet had a lower (P ≤ 0.038) apparent ruminal biohydrogenation of cis-9-C18:1 and C18:3n-3, compared to the cows fed the control diet. The sainfoin diet group had greater (P ≤ 0.018) C18:3n-3 and cis-9, cis-12-C18:2 proportions in the milk FA profile compared to the control diet group. Transfer efficiencies from feed to milk of C18:2, C18:3n-3 and unsaturated FA were greater (P ≤ 0.0179) for the sainfoin diet. Based on the results, it could be concluded that replacing grass silage by sainfoin silage in dairy cow rations reduces ruminal C18:3n-3 biohydrogenation and improves milk FA profile.     

Effect of Feed Processing Method on Average Daily Gain and Gastric Ulcer Development in Weanling Horses

The present study evaluated the effects of two different methods of feed processing on growth and gastric ulceration in 16 weanling Standardbred horses. The two diets were composed of identical ingredients that were processed differently and fed at a rate of 3% body weight per day. The hay and grain diet (diet HG) consisted of 50% alfalfa hay cubes and 50% commercial texturized grain mix fed as is, without any further processing, with the cubes and grain fed in separate containers. The complete pelleted diet (diet CP) consisted of the same proportion of hay cubes and grain mix, which was ground, pelleted, and fed in a single container. The horses were divided into two groups and the study was divided into three periods of 30 days each. During period 1, all 16 horses consumed only free choice alfalfa hay (diet H). Group 1 was given diet CP during period 2 and diet HG during period 3. Group 2 was given diet HG during period 2 and diet CP during period 3. The horses were endoscopically examined for the baseline number and severity of stomach ulcers at the end of period 1, then again at the end of each treatment diet feeding period. Horses on diet CP in periods 2 and 3 had greater ulcer numbers (P = .0135) than diet HG. However, there was no significant difference (P = .30) in ulcer numbers when making a direct comparison between diets CP and HG. Despite the gastric ulceration found in horses on diet CP, the average daily gain was significantly greater (P = .016) for diet CP than for diet HG. Both diets containing grain were observed to cause gastric ulceration.     

Dietary supplementation of yeast cell wall improves the gastrointestinal development of weaned calves

The purpose of this study was to investigate the potential benefits of yeast cell wall (YCW) on the gastrointestinal development of weaned calves. Twenty healthy Holstein male calves (BW = 92 ± 8.29 kg and 60 ± 5 d of age) were randomly allocated into 2 groups: CON with no YCW, and YCW (accounted for 0.16% of the basal diet). The dietary concentrate-to-roughage ratio was 40:60. All the calves were fed regularly twice a day at 09:00 and 16:00 and had free access to water. The experiment lasted for 60 d. The results showed that calves fed YCW showed higher (P < 0.05) length, width, and surface area of papillae in the ventral sac of the rumen as compared to CON. For the dorsal sac of the rumen, the muscularis thickness was thicker (P < 0.05) in the YCW group when compared with CON group. The villus height of YCW calves was higher (P < 0.05) than that of CON in the ileum. Calves supplemented with YCW also showed a higher (P < 0.05) villus height-to-crypt depth ratio in the ileum. The YCW calves exhibited a greater (P < 0.05) thickness of the wall in the duodenum and jejunum. Calves supplemented with YCW improved (P < 0.05) the claudin 1 mRNA expression in the ileum and occludin mRNA expression in the jejunum and ileum. The YCW increased (P < 0.05) the contents of secretory immunoglobulin A in the jejunum and ileum of calves. In conclusion, dietary supplementation with YCW could improve the gastrointestinal development of weaned calves.     

Tannic acid extracted from gallnut prevents post-weaning diarrhea and improves intestinal health of weaned piglets

This experiment was conducted to evaluate the effects of different levels of tannic acid (TA) on growth performance, diarrhea rate, nutrient digestibility and intestinal health in weaned piglets. A total of 180 weaned piglets (Duroc × Landrace × Yorkshire, 24 d of age, initial average BW = 7.77 ± 0.17 kg) were allotted to 5 groups (6 pigs/pen and 6 replicates/group) in a randomized complete block design according to their gender and body weight. Piglets were fed a basal diet, or the basal diet supplemented with 0.05%, 0.1%, 0.2% or 0.4% TA for 28 d. The supplementary levels of TA in the diets were obtained by adding tannalbin containing 51% TA and 40.17% protein. The results showed that, compared with the CON group, dietary TA did not affect ADFI, ADG or F:G, and linearly reduced (P < 0.01) the diarrhea rate and diarrhea index of piglets. There were no significant effects on apparent total tract digestibility (ATTD) in the 0.05%, 0.1% and 0.2% TA groups, while negative effects (P < 0.05) on apparent digestibility of crude protein and gross energy were observed in the 0.4% TA group. In addition, the nutrient digestibility of dry matter, crude protein and gross energy linearly decreased (P < 0.01) with the increase of TA dosage. Supplementation of TA increased (P < 0.05) the villus height of the duodenum and jejunum, as well as increased (P < 0.05) catalase (CAT) activity in serum. Dietary TA improved (P < 0.05) the Bacillus counts in cecal digesta. Further, TA significantly improved (P < 0.05) Bacillus counts and reduced (P < 0.05) the Escherichia coli counts in colonic digesta. The concentration of acetic acid, propionic acid, butyric acid and isovaleric acid in cecal digesta were significantly increased (P < 0.05). The mRNA expression level of zonula occludens-1 (ZO-1), zonula occludens-2 (ZO-2), and claudin-2 (CLDN-2) in the jejunum were greater (P < 0.05) in TA supplemented groups. The study showed that, compared to the control, TA prevented post-weaning diarrhea and improved intestinal health of weaned piglets, and the appropriate level of TA supplementation would be from 0.1% to 0.2%.     

Serum Protein Fraction in Mature Horses and Relationship With Metabolic and Hematological Parameters

This study was conducted to determine the effect of age on serum protein fractions and their relationship with metabolic and hematological profiles in mature horses. Twenty-five mature Italian Saddle horses (mean age 13.6 ± 4.8 years) fed the same diet (grass hay and concentrate) were stratified according to age as first maturity, M1 (≤10 years old); second maturity, M2 (>10 and <15 years old); and old, O (>15 years), to be monitored every 28 days for a continuous period of 140 days. Horses in group O had higher plasma protein and thiol concentrations and white blood cell and neutrophil counts than the other two groups. Serum α₂-globulin concentrations were positively correlated with total plasma cholesterol (r = 0.514; P < .001), alkaline phosphatase (r = 0.430; P < .001), aspartate aminotransferase (r = 0.339; P < .001), ceruloplasmin (r = 0.321; P < .001), glutamic pyruvate transaminase (r = 0.444; P < .001), reactive oxygen metabolites (r = 0.426; P < .001), and blood neutrophil counts (r = 0.344; P < .01), and negatively with plasma bilirubin (r = −0.522; P < .001) and creatinine (r = −0.400; P < .001). These results suggest differences in hematological and metabolic profile in Italian Saddle horses after 15 years of age, resulting mainly from changes in plasma proteins and inflammatory mediators. The α₂-globulins fraction seems a quick but reliable marker of an inflammatory situation that, successively, should be better investigated with specific metabolites or enzymes.     

Effect of Live Yeast Culture Supplementation on Fibrolytic and Saccharolytic Bacterial Populations in the Feces of Horses Fed a High-Fiber or High-Starch Diet

The objective of this study was to assess the effect of live yeast (Saccharomyces cerevisiae) supplementation on the populations of specific cellulolytic (Fibrobacter succinogenes and Ruminococcus flavefaciens) and saccharolytic (Streptococcus equinus and Streptococcus bovis) bacteria in the feces of horses fed high-starch and high-fiber diets. Four horses were each fed diets consisting of high fiber with no yeast (HF), high fiber with yeast (HFY), high starch with no yeast (HS), and high starch with yeast (HSY) in a 4 × 4 Latin-square design study. Fresh fecal samples were collected on the last 3 days of each 31-day experimental period and were then assessed, using semiquantitative real-time PCR, for total bacterial load and levels of target bacterial species, relative to the total bacterial load. The most abundant of the target species was F. succinogenes, and the HSY diet resulted in a significant (P = .045) reduction in relative levels of this bacterium. No significant effect (P = .224) of diet was observed in relation to abundance of R. flavefaciens. Results show that diet did not have a significant (P = .068) effect on relative quantities of S. equinus, although there appeared to be a trend for increased levels of this bacterium during feeding of high-starch diets. Numbers of S. bovis were higher (P < .001) when horses were fed HS and HSY diets than when fed the HF and HFY diets. Significant variation in levels of S. equinus (P = .024) and S. bovis (P = .049) was observed between individual horses.     

Insulin Sensitivity in Thoroughbred Geldings: Effect of Weight Gain,Diet, and Exercise on Insulin Sensitivity in Thoroughbred Geldings

The effects of dietary energy source, controlled weight gain, and exercise restriction on insulin sensitivity (SI) were studied in mature Thoroughbred geldings with body condition scores (BCS) of 4.3 ± 0.1. Two dietary energy sources were used, one high in starch and sugar (HS; n = 9) and one high in fat and fiber (HF; n = 7), and horses were fed 20 Mcal digestible energy (DE)/day above maintenance requirements to encourage weight gain. Using the minimal model of glucose and insulin dynamics, no differences in SI between groups were noted before initiation of treatment concentrate feeding. After dietary acclimation, SI was decreased in HS (P < 0.01) as compared with HF. After 32 weeks of controlled weight gain (90.8 kg; final BCS, 7.0 ± 0.1), SI remained lower in HS (P = 0.07) but did not change from the preweight gain value. SI in HF did not change between the start and end of weight gain. After completion of weight gain, exercise was restricted for 2 weeks, resulting in a reduction in SI in HF (P = 0.03) but no change in HS. It was concluded that dietary energy source may be more influential than weight gain on SI in the mature Thoroughbred gelding between BCS 4 and 7. The higher SI found in horses consuming the HF diet appeared to be partially dependent on some level of physical activity.     

Leucine alone or in combination with glutamic acid,but not with arginine,increases biceps femoris muscle and alters muscle AA transport and concentrations in fattening pigs

Forty‐eight Duroc × Large White × Landrace pigs with an average initial body weight of 77.09 ± 1.37 kg were used to investigate the effects of combination of leucine (Leu) with arginine (Arg) or glutamic acid (Glu) on muscle growth, free amino acid profiles, expression levels of amino acid transporters and growth‐related genes in skeletal muscle. The animals were randomly assigned to one of the four treatment groups (12 pigs/group, castrated male:female = 1:1). The pigs in the control group were fed a basal diet (13% Crude Protein), and those in the experimental groups were fed the basal diet supplemented with 1.00% Leu (L group), 1.00% Leu + 1.00% Arg (LA group) or 1.00% Leu + 1.00% Glu (LG group). The experiment lasted for 60 days. Results showed an increase (p < 0.05) in biceps femoris (BF) muscle weight in the L group and LG group relative to the basal diet group. In longissimus dorsi (LD) muscle, Lys, taurine and total essential amino acid concentration increased in the LG group relative to the basal diet group (p < 0.05). In LG group, Glu and carnosine concentrations increased (p < 0.05) in the BF muscle, when compared to the basal diet group. The Leu and Lys concentrations of BF muscle were lower in the LA group than that in the L group (p < 0.05). A positive association was found between BF muscle weight and Leu concentration (p < 0.05). The LG group presented higher (p < 0.05) mRNA levels of ASCT2, LAT1, PAT2, SANT2 and TAT1 in LD muscle than those in the basal diet group. The mRNA levels of PAT2 and MyoD in BF muscle were upregulated (p < 0.05) in the LG group, compared with those in the basal diet group. In conclusion, Leu alone or in combination with Glu is benefit for biceps femoris muscle growth in fattening pig.     

Reduced dietary nitrogen with a high Lys:CP ratio restricted dietary N excretion without negatively affecting weaned piglets

We hypothesized that balancing the content of exogenous amino acids, especially lysine, to reduce protein content in swine diets could reduce nitrogen (N) pollution associated with animal husbandry. Two experiments (45 d each experiment) were performed on weaned piglets (Duroc × Landrace × Yorkshire, 28 d of age) to test this and to determine the optimal lysine to crude protein (Lys:CP) ratio in diet. In Exp. 1, 12 piglets (6 replicates [n = 6]) were fed diets containing different levels of CP (17% and 20%) but the same level of Lys. Increased CP content resulted in significant increases (P < 0.05) of average daily gain (ADG), average daily feed intake (ADFI), and body weight (BW), but did not affect the feed to gain ratio. In Exp. 2, 24 piglets (8 replicates [n = 8]) were fed 1 of 3 diets as follows: 1) 20% CP with a regular Lys:CP ratio (6.23%, control); 2) 17% CP with a reduced Lys:CP ratio (6.14%, LL); or 3) 17% CP with a standard Lys:CP ratio (7.32%, SL). The ADG, final BW, serum concentrations of growth hormone and insulin-like growth factor-1, villus height in the jejunum, and villus height to crypt depth ratio were the lowest in piglets fed LL diet, whereas blood urea N concentration was the lowest and the value of lipase activity was the highest in the piglets fed SL diet. The SL diet did not affect growth performance, intestinal morphology, or serum hormone concentrations, indicating that reduced dietary N with a high Lys:CP ratio can efficiently reduce dietary N excretion without negatively affecting weaned piglets.     

Growth Hormone and Prolactin Secretion in Horses: Effects of Multiple and Extended Exercise Bouts, β-Hydroxy-β-Methyl Butyrate Feeding,and Arginine and Thyrotropin-Releasing Hormone Pretreatment

Five experiments were performed to test the overall hypothesis that exercise might be a useful indicator of growth hormone (GH) and prolactin status in horses. In experiment 1, geldings were exercised for 5 minutes four times at hourly intervals. The prolactin response (P < .05) to the first two exercise bouts was small and increased with successive bouts. There was a consistent GH response (P < .05) for only the first two bouts. In experiment 2, geldings were exercised for 29 to 39 minutes on a treadmill. After the initial bout, half the geldings were supplemented daily with Ca-β-hydroxy-β-methyl butyrate, and all geldings were conditioned for 12 weeks. Exercise bouts at 7 and 12 weeks indicated no effect (P > .1) of supplementation. In experiment 3, treatment of geldings with arginine before exercise increased (P < .001) prolactin concentrations but had no effect (P > .1) on the GH response to exercise. In experiment 4, the repeatability of the GH response to 5 minutes of exercise was determined by exercising eight stallions on six separate occasions. In addition to a large variation in GH response among stallions, there was a large variation within each stallion. In experiment 5, pretreatment with thyrotropin-releasing hormone 2 hours before exercise did not normalize the GH response to exercise. In conclusion, factors affecting the GH response to exercise likely preclude its usefulness as an indicator of GH status in horses.