Relative availability of metabolizable methionine from 2 ruminally protected sources of methionine fed to lactating dairy cattle.

Our objective was to evaluate the lactational responses of dairy cows to methionine provided from 2 ruminally protected sources of methionine activity. Twenty-one Holstein dairy cows [11 primiparous (634 kg of body weight, 140 d in milk) and 10 second-parity (670 kg of body weight, 142 d in milk)] were assigned to a treatment sequence in 4 replicated 5 × 5 Latin squares plus 1 cow, with 14-d periods. Treatments were as follows: control; 7.5 or 15 g/d of a ruminally protected product of 2-hydoxy-4-methylthio-butyric acid (NTP-1401; Novus International Inc., St. Charles, MO); or 7.5 or 15 g/d of a ruminally protected dl-methionine product (Smartamine M; Adisseo, Alpharetta, GA). The diet was predicted to meet metabolizable protein and energy requirements. Diets contained 16.1% crude protein, and the control diet was predicted to be deficient in metabolizable methionine (1.85% of metabolizable protein) but sufficient in lysine (6.8% of metabolizable protein). Feed intake and milk yield were measured on d 11 to 14. Blood was collected on d 14. Dry matter intake, milk yield, energy-corrected milk, milk fat yield and percentage, and efficiencies of milk and energy-corrected milk yield were not affected by treatment. Milk protein percentage and milk protein yield increased linearly with supplementation, without differences between methionine sources or interactions between source and level. Linear regressions of milk protein percentage and milk protein yield against supplement amount within source led to slope ratios (NTP-1401:Smartamine M) of 95% for protein percentage and 84% for protein yield, with no differences between sources for increasing milk protein. Plasma methionine concentrations were increased linearly by methionine supplementation; the increase was greater for Smartamine M than for NTP-1401. Plasma d-methionine was increased only by Smartamine M. Plasma 2-hydoxy-4-methylthio-butyric acid was increased only by NTP-1401. Our data demonstrated that supplementation with these methionine sources can improve milk protein percentage and yield, and the 2 methionine sources did not differ in their effect on lactation performance or milk composition.

Effect of 2-hydroxy-4-methylthio-butanoic acid on ruminal fermentation, bacterial distribution, digestibility, and performance of lactating dairy cows.

The objective of this experiment was to test the effect of a Met analog, 2-hydroxy-4-methylthio-butanoic acid (HMTBa), on ruminal fermentation and microbial protein synthesis, nutrient digestibility, urinary N losses, and performance of dairy cows. Eight multiparous lactating Holstein dairy cows were assigned to 4 levels of HMTBa [0 (control), 0.05, 0.10, and 0.15% (dry matter basis)] in a replicated 4×4 Latin square trial. Experimental periods were 28 d, including 21 d for adaptation. Ruminal ammonia and microbial N were labeled through a 6-d intraruminal infusion of (15)NH4Cl, and microbial protein synthesis in the rumen was estimated using the reticular sampling technique. Treatment had no effect on dry matter intake (28.4 to 29.8kg/d), milk yield (44.1 to 45.3kg/d), feed efficiency, and milk composition. Total-tract apparent digestibility of nutrients was generally not affected by treatment, except digestibility of crude protein and starch decreased quadratically with HMTBa supplementation. Fecal, but not urinary, and total excreta N losses were increased quadratically by HMTBa. Ruminal pH, ammonia concentration, protozoal counts, and the major volatile fatty acids were not affected by treatment. Microbial N outflow from the rumen was linearly increased by HMTBa. 2-Hydroxy-4-methylthio-butanoic acid linearly increased the proportion of Fecalibacterium and quadratically decreased the proportion of Eubacterium in ruminal contents. Of the individual bacterial species, HMTBa increased or tended to increase Prevotella loescheii and Prevotella oralis. 2-Hydroxy-4-methylthio-butanoic acid linearly increased the concentration (and yield) of 15:0 in milk fat. In the conditions of this crossover experiment, HMTBa had no effect on feed intake and performance of dairy cows, decreased dietary crude protein digestibility, and increased microbial N outflow from the rumen.

Meta-analysis of lactation performance in dairy cows receiving supplemental dietary methionine sources or postruminal infusion of methionine.

The objectives of our study were to evaluate the productive response to methionine supplementation in lactating dairy cows and to define a relationship between metabolizable Met (MP Met) intake and production. A database of 64 papers meeting the selection criteria was developed evaluating postruminally infused dl-methionine (9 papers with 18 control diets and 35 treatment comparisons), 2-hydroxy-4-methylthio butanoic acid (HMTBa) provided as either a liquid or Ca salt form (17 papers with 34 control diets and 46 treatment comparisons), Mepron (Evonik Industries, Essen, Germany; 18 papers with 35 control diets and 42 treatment comparisons), and Smartamine (Adisseo Inc., Antony, France; 20 papers with 30 control diets and 39 treatment comparisons). Dietary ingredients and their accompanying nutritional compositions as described in the reports were entered into the Cornell-Penn-Miner software to model the diets and to predict nutrients that were not reported in the original publication. Data were analyzed using a weighted analysis of response to supplementation compared with the intraexperiment control, as well as through a regression analysis to changing dietary MP Met. Data included in the analysis were from experiments published between 1970 and 2011 with cows supplemented with between 3.5 and 67.9 g of Met or its equivalent from HMTBa. Cows supplemented with Smartamine consumed more, whereas cows supplemented with Mepron consumed less DM compared with controls. Milk yield did not significantly respond to Met supplementation, although it tended to increase for cows supplemented with HMTBa and Mepron. Milk protein yield was increased due to supplementation from all sources or from infusion, and protein concentration was greater for all supplements or infusion of dl-Met, except for cows supplemented with HMTBa. Irrespective of Met source, milk protein yield increased 2.23 g of protein/g of MP Met until reaching the breakpoint. Milk fat yield was increased for Mepron and HMTBa, whereas milk fat concentration was increased for infused dl-Met and for cows supplemented with HMTBa. Based on regression analysis, response of milk fat yield to Met supplementation was not different for infused dl-Met, Mepron, and Smartamine (1.87 g of fat/g of MP Met), whereas the response to HMTBa was significantly greater at 5.38 g of fat/g of MP Met.

Effects of a chelated copper as growth promoter on performance and carcass traits in pigs.

Three studies were conducted to investigate whether a chelated Cu can replace CuSO4 as a growth promoter in pigs. In Exp. 1, a total of 240 piglets (Large White×Landrace, 7.36±0.10 kg) were randomly allocated to 1 of 3 treatments with 8 replicates and 10 piglets per pen. Treatments included a NRC control (CuSO4, 6 mg/kg), two Cu supplementations from either CuSO4 or Cu(HMTBa)2 at 170 mg/kg. Pigs fed Cu(HMTBa)2 were 6.0% heavier than pigs fed either the NRC control or 170 mg/kg CuSO4 (p = 0.03) at the end of the experiment. During the 42 days of experimental period, pigs fed Cu(HMTBa)2 gained 9.0% more (p = 0.01), tended to eat more feed (p = 0.09), and had better feed efficiency (p = 0.06) than those fed CuSO4. Compared with the 6 mg/kg CuSO4 NRC control, liver Cu was increased 2.7 times with 170 mg/kg CuSO4 supplementation, and was further increased with Cu(HMTBa)2 (4.5 times, p<0.05). In Exp. 2, a total of 616 crossbred piglets (PIC, 5.01±0.25 kg) were randomly allocated to 1 of 4 treatments with 7 replicates and 22 piglets per pen. Treatments included a NRC control (from CuSO4), and three pharmaceutical levels of Cu (150 mg/kg) supplemented either from CuSO4, tri-basic copper chloride (Cu2[OH]3Cl), or Cu(HMTBa)2. Pigs fed CuSO4 or Cu(HMTBa)2 had better feed efficiency (p = 0.01) and tended to gain more (p = 0.08) compared with those fed the NRC control. Pigs fed Cu2(OH)3Cl were intermediate. Pigs fed Cu(HMTBa)2 had the highest liver Cu, which was significantly higher than those fed (Cu2[OH]3Cl) or the negative control (p = 0.01). In Exp. 3, a total of 1,048 pigs (PIC, 32.36±0.29 kg) were allotted to 6 treatments with 8 replicates per treatment and 20 to 22 pigs per pen. The treatments included a NRC control with 4 mg/kg Cu from CuSO4, a positive control with 160 mg/kg Cu from CuSO4, and incremental levels of Cu(HMTBa)2 at 20, 40, 80, and 160 mg/kg. During the overall experimental period of 100 days, no benefit from 160 mg/kg CuSO4 was observed. Pigs fed Cu(HMTBa)2 had increased ADG (linear and quadratic, p≤0.05) and feed efficiency (linear and quadratic, p≤0.05) up to 80 mg/kg and no further improvement was observed at 160 mg/kg for the whole experimental period. Pigs fed 80 mg/kg Cu(HMTBa)2 weighed 1.8 kg more (p = 0.07) and were 2.3 kg heavier in carcass (p<0.01) compared with pigs fed 160 mg/kg CuSO4. In addition, loin depth was increased with increased Cu(HMTBa)2 supplementation with pigs fed 80 mg/kg Cu(HMTBa)2 had the greatest loin depth (p<0.05). In summary, Cu(HMTBa)2 can be used to replace high CuSO4 as a growth promoter in nursery and grower-finisher pigs.

Metabolism of 2-hydroxy-4-(methylthio)butanoate (HMTBA) in lactating dairy cows.

The objectives of the current study were to determine the fate and contribution to Met kinetics of 2-hydroxy-4-(methylthio)butanoate (HMTBA) at the whole-body, splanchnic, and mammary levels. Four multicatheterized cows (31.3 kg of milk/d; 17.7 kg of DMI/d) were used in a crossover design, with two 1-wk periods, to determine the metabolic fate of HMTBA and its effect on Met metabolism. Over the last 2 d of each period, cows were infused, via a jugular vein, with saline or HMTBA (Alimet, Novus International Inc., St. Louis, Mo) at the rate of 36 g/d. During the last 8h, the HMTBA infusion was substituted by equimolar [1-(13)C]HMTBA (8.79 mmol/h) and l[methyl-(2)H(3)]Met (1.31 mmol/h) was infused in all cows. During the last 5h, hourly samples (n=6) were collected to determine plasma flows plus the isotopic enrichments (IE) and concentrations of HMTBA ((13)C) and Met (both (13)C and (2)H(3)) in plasma from an artery plus portal, hepatic, and mammary veins. The IE of [(13)C] and [(2)H(3)]Met were also determined in milk protein taken over the last 1h of infusion in HMTBA-infused cows. The infused HMTBA increased whole-body plasma flux of Met by 6.5 mmol/h (from 17.9 to 24.4 mmol/h). Based on enrichments of (13)C-labeled Met, 3.8 mmol/h of Met flow through plasma was derived directly from HMTBA. These 2 estimates accounted for between 43 to 74% of the HMTBA dose infused, contributing to increased whole-body Met availability. Although the portal-drained viscera, liver, and mammary gland (MG) extracted 11, 37, and 3.4%, respectively, of the infused HMTBA, tissue net Met fluxes were either unchanged (portal-drained viscera, MG) or even reduced (liver: -7.9 vs. -2.4±0.6 mmol/h). Therefore, net postsplanchnic supply of Met decreased from 7.0 to 2.9 mmol/h between control and HMTBA-infused cows, compared with needs for milk protein secretion of 7.6 and 8.1 mmol/h, respectively. The HMTBA provided directly 15% of the Met required for milk protein secretion, with 0.2 mmol/h synthesized within the MG, whereas 1.1 mmol/h originated from Met produced in other tissues and transported to the MG through blood circulation. Most of the remainder needed by the MG arose from unlabeled Met released from protein breakdown in extra-splanchnic tissues and that was not reused to support intracellular protein synthesis, as this function was performed by Met synthesized from HMTBA in situ. Absorbed HMTBA, therefore, both produces and spares Met for use by the MG.

Effect of different rumen-inert fatty acids supplemented with a dietary antioxidant on performance and antioxidative status of early-lactation cows.

The objective of the study was to evaluate the effect of diets supplemented with fatty acids of different degrees of saturation, in the absence or presence of an antioxidant (AOX; Agrado Plus, Novus International Inc., St. Charles, MO), on dairy cow lactation performance. Calcium salts of long-chain fatty acids were supplemented as a source of lower saturation fatty acid, and a palm acid product was supplemented as the higher saturation fatty acid source. Sixty early-lactation Chinese Holstein cows (100+/-23 d in milk) were randomly allocated to 4 dietary treatments in a 2 x 2 factorial design: (1) lower saturation fatty acid (LS), (2) LS and AOX, (3) higher saturation fatty acid (HS), and (4) HS and AOX. The Ca salts of long-chain fatty acids and palm acid product were supplied at 1.8 and 1.5% on a dry matter basis, respectively, to form isoenergetic diets. The AOX was added at 0.025% in the ration. The experiment lasted 9 wk, including 1 wk for adaptation. Lactation performance was recorded and milk was sampled and analyzed weekly. Blood samples were taken from the coccygeal vein to determine metabolism parameters on d 16, 36, and 56 during the experiment. Neither fatty acid type nor AOX supplementation showed a significant effect on dry matter intake during the study. Milk yield was lower in the LS-fed cows compared with the cows fed HS. Milk fat and milk protein concentrations were not affected by fatty acid type or AOX supplementation. Adding AOX increased the yield of milk in the LS-fed cows, but did not affect those fed HS. Activity of plasma superoxide dismutase was significantly lower, plasma glucose tended to be lower, and plasma malondialdehyde was higher in the LS-fed animals compared with those fed HS. Addition of AOX decreased both plasma nonesterified fatty acids and hydrogen peroxide contents and increased total antioxidant capacity across the fatty acid types. Plasma beta-hydroxybutyrate was not affected by fatty acid type or AOX treatment. Cows fed LS had higher cis-9C(18:1) and trans-10, cis-12C(18:2) in milk at the expense of C(18:0), whereas AOX addition increased milk cis-9C(18:1) at the expense of milk C(12:0), C(16:0), and trans-10, cis-12C(18:2). It is inferred that feeding LS resulted in inferior lactation performance, whereas addition of antioxidant partially alleviated these negative effects.

Comparison of hydrated sodium calcium aluminosilicate and yeast cell wall on counteracting aflatoxicosis in broiler chicks.

The objective of this research was to determine the efficacy of 2 types of adsorbents [hydrated sodium calcium aluminosilicates (HSCAS) vs. a combination of clay and yeast cell wall] in preventing aflatoxicosis in broilers. A total of 275 one-day-old birds were randomly divided into 11 treatments, with 5 replicate pens per treatment and 5 chicks per pen. The 11 treatments included 3 diets without any adsorbent containing either 0, 1, or 2 mg/kg of aflatoxin B1 (AFB1) plus 8 additional treatments employing 2 dietary levels of AFB1 (1 or 2 mg/kg), 2 different adsorbents [Solis (SO) and MTB-100 (MTB)], and 2 different levels of each absorbent (0.1 and 0.2%) in a 2×2×2 factorial arrangement. Solis is a mixture of different HSCAS and MTB is a combination of clay and yeast cell wall. Feed and water were provided ad libitum throughout the 21-d study period. Body weight gain and feed intake were depressed and relative liver weight was increased in chicks fed AFB1 compared with the positive control (P<0.05). Severe liver damage was observed in chicks fed 2 mg/kg of AFB1 with lesions consistent with aflatoxicosis, including fatty liver and vacuolar degeneration. Serum glucose, albumin, total protein, Ca, P, and alkaline phosphatase concentrations were reduced by AFB1 (P<0.05). The addition of either SO or MTB ameliorated the negative effects of 1 mg/kg of AFB1 on growth performance and liver damage (P<0.05). However, supplemental MTB failed to diminish the negative effects of 2 mg/kg of AFB1, whereas SO was more effective compared with MTB at 2 mg/kg of AFB1 (P<0.05). These data indicate that the HSCAS product effectively ameliorated the negative effect of AFB1 on growth performance and liver damage, whereas the yeast cell wall product was less effective especially at the higher AFB1 concentration.

In vitro digestibility of individual amino acids in rumen-undegraded protein: the modified three-step procedure and the immobilized digestive enzyme assay.

Three soybean meal, 3 SoyPlus (West Central Cooperative, Ralston, IA), 5 distillers dried grains with solubles, and 5 fish meal samples were used to evaluate the modified 3-step in vitro procedure (TSP) and the in vitro immobilized digestive enzyme assay (IDEA; Novus International Inc., St. Louis, MO) for estimating digestibility of AA in rumen-undegraded protein (RUP-AA). In a previous experiment, each sample was ruminally incubated in situ for 16 h, and in vivo digestibility of AA in the intact samples and in the rumen-undegraded residues (RUR) was obtained for all samples using the precision-fed cecectomized rooster assay. For the modified TSP, 5 g of RUR was weighed into polyester bags, which were then heat-sealed and placed into Daisy(II) incubator bottles. Samples were incubated in a pepsin/HCl solution followed by incubation in a pancreatin solution. After this incubation, residues remaining in the bags were analyzed for AA, and digestibility of RUP-AA was calculated based on disappearance from the bags. In vitro RUP-AA digestibility estimates obtained with this procedure were highly correlated to in vivo estimates. Corresponding intact feeds were also analyzed via the pepsin/pancreatin steps of the modified TSP. In vitro estimates of AA digestibility of the feeds were highly correlated to in vivo RUP-AA digestibility, which suggests that the feeds may not need to be ruminally incubated before determining RUP-AA digestibility in vitro. The RUR were also analyzed via the IDEA kits. The IDEA values of the RUR were good predictors of RUP-AA digestibility in soybean meal, SoyPlus, and distillers dried grains with solubles, but the IDEA values were not as good predictors of RUP-AA digestibility in fish meal. However, the IDEA values of intact feed samples were also determined and were highly correlated to in vivo RUP-AA digestibility for all feed types, suggesting that the IDEA value of intact feeds may be a better predictor of RUP-AA digestibility than the IDEA value of the RUR. In conclusion, the modified TSP and IDEA kits are good approaches for estimating RUP-AA digestibility in soybean meal products, distillers dried grains with solubles, and fish meal samples.

Efficacy of Solis, NovasilPlus, and MTB-100 to reduce aflatoxin M1 levels in milk of early to mid lactation dairy cows fed aflatoxin B1.

An experiment was conducted to determine the efficacy of 3 adsorbents, Solis (SO; Novus International Inc.), NovasilPlus (NOV; Engelhard Corp.), and MTB-100 (MTB; Alltech), in reducing aflatoxin (AF) M(1) concentrations in milk of dairy cows fed an AF-contaminated diet. Twelve early to mid lactation dairy cows averaging 163 d in milk were used in a 4 x 4 Latin square design with 3 replications. Cows were blocked by parity, body weight, and milk production and were provided ad libitum access to feed and water. Within each replicate, cows were randomly assigned to the 4 dietary treatments for 4 consecutive 7-d periods. Dietary treatments included AF [112 microg of AFB(1)/kg of diet dry matter (DM)]; AF + 0.56% SO; AF + 0.56% NOV; and AF + 0.56% MTB. Milk samples were collected on d 6 and 7 of each of the experimental periods. Feed intake, milk production, milk fat percentage, milk protein percentage, and linear somatic cell scores were not affected by dietary treatments and averaged 22.20 kg/d of DM, 33.87 kg/d, 3.78%, 2.95%, and 1.60, respectively, across all treatments. Transfer rates of AF from feed to milk averaged 2.65, 1.48, 1.42, and 2.52% for cows fed AF, AF + SO, AF + NOV, and AF + MTB, respectively. Daily AFM(1) excretion in milk averaged 66, 37, 35, and 63 microg/d for cows fed AF, AF + SO, AF + NOV, and AF + MTB, respectively. The addition of SO and NOV to the AF diet resulted in a significant reduction in milk AFM(1) concentrations (SO, 45%; NOV, 48%) and AFM(1) excretion (SO, 44%; NOV, 46%). In contrast, MTB was not effective in reducing milk AFM(1) concentrations (4%), AFM(1) excretion (5%), or AF transfer from feed to milk (2.52%). Results indicated that SO and NOV at 0.56% of the diet were effective in reducing milk AFM(1) concentrations in cows consuming a total mixed ration containing 112 microg of AFB(1)/kg of diet DM.

Effects of trace mineral amount and source on aspects of oxidative metabolism and responses to intramammary lipopolysaccharide challenge in midlactation dairy cows.

Trace minerals have important roles in immune function and oxidative metabolism; however, little is known about the relationships between supplementation level and source with outcomes in dairy cattle. Multiparous Holstein cows (n=48) beginning at 60 to 140 days in milk were utilized to determine the effects of trace mineral amount and source on aspects of oxidative metabolism and responses to intramammary lipopolysaccharide (LPS) challenge. Cows were fed a basal diet meeting National Research Council (NRC) requirements except for no added zinc (Zn), copper (Cu) or manganese (Mn). After a 4-week preliminary period, cows were assigned to one of four topdress treatments in a randomized complete block design with a 2×2 factorial arrangement of treatments: (1) NRC inorganic (NRC levels using inorganic (sulfate-based) trace mineral supplements only); (2) NRC organic (NRC levels using organic trace mineral supplements (metals chelated to 2-hydroxy-4-(methythio)-butanoic acid); (3) commercial inorganic (approximately 2×NRC levels using inorganic trace mineral supplements only; and (4) commercial organic (commercial levels using organic trace mineral supplements only). Cows were fed the respective mineral treatments for 6 weeks. Treatment effects were level, source and their interaction. Activities of super oxide dismutase and glutathione peroxidase in erythrocyte lysate and concentrations of thiobarbituric acid reactive substances (TBARS) and total antioxidant capacity (TAC) in plasma were measured as indices of oxidative metabolism. Effects of treatment on those indices were not significant when evaluated across the entire experimental period. Plasma immunoglobulin G level was higher in cows supplemented with organic trace minerals over the entire treatment period; responses assessed as differences of before and after Escherichia coli J5 bacterin vaccination at the end of week 2 of treatment period were not significant. Cows were administered an intramammary LPS challenge during week 5; during week 6 cows fed commercial levels of Zn, Cu and Mn tended to have higher plasma TAC and cows fed organic sources had decreased plasma TBARS. After the LPS challenge, the extent and pattern of response of plasma cortisol concentrations and clinical indices (rectal temperature and heart rate) were not affected by trace mineral level and source. Productive performance including dry matter intake and milk yield and composition were not affected by treatment. Overall, results suggest that the varying level and source of dietary trace minerals do not have significant short-term effects on oxidative metabolism indices and clinical responses to intramammary LPS challenge in midlactation cows.

Effects of feeding a dietary antioxidant in diets with oxidized fat on lactation performance and antioxidant status of the cow.

The objective of the study was to evaluate the effect of feeding the dietary antioxidant Agrado Plus (AOX; Novus International, St. Louis, MO) in diets that contained 2% fresh fat (FF) or oxidized fat (OF) on milk production and composition and antioxidant status of cows during mid to late lactation. Forty-four mid to late lactating primiparous cows housed in a tie-stall barn were fed a diet that contained 2% FF for 15 d as adaptation period and then randomly allocated to 1 of the 4 dietary treatments (FF, FF+AOX, OF, OF +AOX) for 6 wk. Feeding AOX increased dry matter intake, 3.5% fat-corrected milk, and milk fat yield, and decreased milk protein content but not yield. Feeding OF increased milk fat yield, but decreased dry matter intake and body weight gain. Milk fat composition changed with treatments: AOX increased cis 18:1 and decreased trans-11 18:1, whereas OF decreased trans-9 and trans-11 18:1 and cis-9, trans-11 18:2 in milk. Plasma antioxidant enzymes and status were affected by treatments. Feeding OF increased superoxidase dismutase activity but decreased plasma antioxidant status, whereas AOX supplementation increased glutathione peroxidase activity across fat types and increased the antioxidant status and superoxidase dismutase activity when feeding OF diets. It can be concluded that feeding AOX improved lactation performance and the antioxidant status of the cow across fat types, and feeding OF increased milk fat yield but decreased dry matter intake, body weight gain, and antioxidant status. The negative effects of feeding OF were partially alleviated by AOX.

Effects of feeding oxidized fat with or without dietary antioxidants on nutrient digestibility, microbial nitrogen, and fatty acid metabolism.

A dual-effluent continuous culture system was used to investigate, in a 2 x 2 factorial design, the effect of feeding a fresh (FF) or oxidized (OF) blend of unsaturated fats (33% fish oil, 33% corn oil, 26% soybean oil, and 7% inedible tallow) when supplemented with a blend of antioxidants (AO; Agrado Plus, Novus International Inc.; Agrado Plus is a trademark of Novus International Inc. and is registered in the United States and other countries) on nutrient digestibility, bacterial protein synthesis, and fatty acid metabolism. Twice a day for 10 d, 12 fermenters were fed a diet that consisted of 52% forage and 48% grain mixture that contained 3% (dry matter basis) FF or OF, with or without AO. The OF contained a higher concentration of peroxides (215 vs. 3.5 mEq/kg), and a lower concentration of unsaturated fatty acids than the FF. Feeding OF reduced nitrogen digestibility, microbial nitrogen yield, and efficiency (expressed as kilograms of dry matter digested) and increased the outflow of saturated fatty acids in the effluent when compared with feeding FF. Adding AO improved total carbohydrate, neutral, and acid detergent fiber digestibilities and the amount of digested feed nitrogen converted to microbial nitrogen across the types of fats. From this study, we concluded that feeding OF reduced microbial nitrogen and increased the outflow of saturated fatty acids. Feeding AO improved fiber digestibility by rumen microorganisms, regardless of the type of fat.

Short communication: Absorption of 2-hydroxy-4-methylthiobutanoate in dairy cows.

The objective of this study was to measure net portal absorption of 2-hydroxy-4-methylthiobutanoate (HMTBA) in dairy cows. Four multicatheterized lactating cows were used in a cross-over design with 7-d experimental periods. They were fed every other hour a total mixed ration and received, in addition, twice a day, 12.5 or 25 g/meal of HMTBA. On the last day of treatment, net portal absorption of HMTBA was numerically greater after the 25-g compared with the 12.5-g bolus meal of HMTBA, and the amount absorbed relative to the dose ingested was unchanged between treatments averaging 11.2 +/- 4.7% of the dose. This represents a minimum value of HMTBA availability because it does not take into account any HMTBA metabolized to Met by gut tissues (in sheep this amounted to another 5% of the dose). A rapid method to estimate net portal absorption based on temporal variations of the peripheral plasma HMTBA concentrations following the HMTBA meal is also presented. Based on the good relationship (concordance correlation coefficient = 0.97) observed between direct measurements and estimations, this simplified approach offers a reasonable approach to assess HMTBA absorption under different feeding situations.

Effects of rumen-undegradable protein sources and supplemental 2-hydroxy-4-(methylthio)-butanoic acid and lysine-HCl on lactation performance in dairy cows.

One hundred primiparous and multiparous Holstein cows were used in an experiment to evaluate the effect of supplementing diets with either a plant- or an animal-based source of rumen-undegradable protein (RUP), with or without AA supplementation, during the transition period and early lactation on milk production response. The experimental design was a randomized block design with approximately one-third of the cows being primiparous. Cows were assigned to 1 of 4 prepartum diets introduced 3 wk before the expected calving date and switched to the corresponding postpartum diet at calving. Diets 1 (AMI) and 2 (AMI+) included a vegetable RUP source (heat- and lignosulfonate-treated canola meal), with diet 2 containing supplemental Lys x HCl and Met hydroxy analog sources [D,L-2 hydroxy-4-(methylthio)-butanoic acid; Alimet feed supplement]. Diets 3 (PRO) and 4 (PRO+) consisted of a blend of animal RUP sources (blood meal, fish meal, feather meal, and porcine meat and bone meal), with diet 4 containing supplemental Lys x HCl and Met hydroxy analog sources [D,L-2 hydroxy-4-(methylthio)-butanoic acid; Alimet]. During the first 4 wk of lactation, dry matter intake was less when synthetic Lys x HCl and Alimet were supplemented, but this effect was no longer evident in wk 5 to 9 of the experiment. Interestingly, despite the initial decrease in dry matter intake in the cows fed AA-supplemented diets, there was no effect of treatment on milk production or the ratio of fat-corrected milk to dry matter intake throughout the 17 wk of the study. Undegradable protein source (vegetable vs. animal) did not affect dry matter intake, milk production, or 3.5% fat-corrected milk production for the first 17 wk of lactation. The results of this study indicate that heat- and lignosulfonate-treated canola meal can be used as a source of undegradable protein in place of high-quality rumen-undegradable animal protein sources without negative effects on milk production when diets are equivalent in rumen degradable protein, RUP, and metabolizable Met and Lys. Despite other reports citing clear benefits to feeding supplemental synthetic Lys or Met in diets fed to high-producing lactating dairy cows, we were unable to provide additional evidence to support these findings. Additionally, there was a trend for whole-blood Lys concentrations to be greater for diets supplemented with Lys x HCl.

Evidence of a different dose response in turkeys when fed 2-hydroxy-4(methylthio) butanoic acid versus DL-methionine.

In broilers, 2-hydroxy-4(methylthio) butanoic acid (HMTBA) can elicit a different dose response relative to dl-Met (DLM) such that birds could have lower gain responses at deficient TSAA concentrations but greater gain responses at maximum response concentrations. Two experiments tested if the 2 Met sources have a different dose response in 1-d-old turkeys using a 2 x 4 factorial plus a control design with 8 replicates of 12 toms per treatment. 2-Hydroxy-4(methylthio) butanoic acid and DLM were supplemented at equimolar concentrations of 0.05, 0.10, 0.15, and 0.20% or 0.04, 0.08, 0.16, and 0.32% for experiments 1 and 2, respectively, in commercial-type TSAA-deficient (0.99 to 1.02%) diets for 21 d. No differences in any performance parameter tested were found between HMTBA and DLM in either trial by ANOVA. Linear (LIN), quadratic (QUAD), and exponential regressions were fitted to the gain response of birds fed HMTBA or DLM. Equations with better goodness of fit as determined by Schwarz's Bayesian information criteria index were used for further calculations of predicted differences between HMTBA and DLM. In both trials, the shape of the dose response differed according to the Met source used, and best-fit equations were obtained when using Met intake over control rather than dietary Met concentration as the dependent variable. In experiment 1, the best-fit equations were an inverse QUAD for HMTBA and a LIN for DLM, and in experiment 2 with higher Met concentrations, the best-fit equations were a QUAD for DLM and a LIN for HMTBA. Feeding HMTBA at deficient TSAA resulted in lower (P <0.05) gains in experiment 1 but greater gains at maximum response concentrations (P <0.05) in both experiments. Plasma-free Met increased at 3 times the rate for DLM than HMTBA (P <0.01) with increasing Met concentration, which may play a role in the evolution of different dose responses at the extremes of the Met dose response. These results demonstrate that Met sources elicit a differential dose response in turkeys such that feeding HMTBA at deficient TSAA concentrations can be lower than DLM and can reach a higher maximum performance than with DLM.

Effect of carbohydrase and protease on growth performance and gut health of young broilers fed diets containing rye, wheat, and feather meal.

An experiment was conducted to characterize a gut health challenge model consisting of a diet containing rye, wheat, and feather meal and a mild mixed-species Eimeria challenge, and to evaluate the effect of carbohydrase and protease on growth performance and gut health of young broilers. The study included 4 treatments: negative control, carbohydrase alone, protease alone, and combination of carbohydrase and protease. Each test diet was fed to 18 battery pens of broilers with 8 male birds per pen from 0 to 22 d of age. Carbohydrase improved body weight, feed intake, and feed conversion ratio (FCR) on d 7, 14, and 21(P < 0.01). Protease increased body weight on d 7 and 21 and improved 0 to 7 d FCR (P < 0.05). More lymphocyte infiltration was observed in small intestine mucosa of negative control birds on d 8, carbohydrase supplementation lessened this. Both carbohydrase and protease reduced digesta viscosity on d 22 with the carbohydrase effect being the greater of the two, and the combination effect was not different from the carbohydrase effect alone (P < 0.01). Ileal Clostridium perfringens of 15-day-old broilers was decreased by carbohydrase, a further reduction was achieved by combining carbohydrase with protease (P = 0.01). Liver vitamin E concentration on d 15 (P < 0.01) and 22 (P = 0.02) was increased by carbohydrase, and the carbohydrase effect was greater in the presence of protease on d 22 (P = 0.04). Plasma α-1-acid glycoprotein level and liver Zn and Cu concentrations of broilers were reduced by carbohydrase on d 15 (P < 0.01). Broilers fed carbohydrase had higher levels of plasma zeaxanthin on d 22 and higher levels of plasma lutein on d 15 and 22 (P < 0.01). In summary, a rye wheat based diet containing feather meal when fed to broilers in addition to a mild Eimeria challenge induced subclinical enteritis characterized by digestion inefficiency, dysbacteriosis, inflammation, and gut barrier failure; carbohydrase and protease could be effective tools to improve growth performance and gut health of broilers suffering from this type of subclinical enteritis.

Incidence of broiler breast myopathies at 2 different ages and its impact on selected raw meat quality parameters.

White striping (WS) and woody breast (WB) are 2 poultry meat quality defects that affect the acceptance of raw breast fillets as well as properties of cooked and further processed products. The present study was intended to evaluate the incidence of these conditions in broilers at different ages and to compare the properties of fillets with different degrees of WS and WB. For this study, 1,920 birds were processed, at 6 and 9 wk of age, in a standard commercial inline processing system. After chilling, carcasses were deboned and butterfly fillets were collected and weighed. Individual fillets were scored for normal, moderate, severe, and very severe degrees of WS and WB, and for petechial hemorrhagic lesions (PHEM, 0 - no lesion to 2 - severe lesion). Representative fillets with NORM-WS/WB, SEV-WS, SEV-WB, and SEV-WS/WB were selected and stored at 4°C. After 24 h, fillet length, width, cranial height, and caudal height, as well as pH, color, and drip loss were recorded. There was an increase in incidence of severe and very severe WS and WB conditions at 9 wk compared to 6 wk of age. The relationship between fillet weight and the myopathies plateaued at 9 wk of age with more fillets showing a higher score. Mean PHEM scores were higher (P < 0.05) in SEV-WS, SEV-WB, and SEV-WS/WB compared to NORM-WS/WB birds, both at 6 and 9 weeks. NORM-WS/WB birds had lower (P < 0.05) live and breast weight, breast yield, and cranial and caudal heights, as well as b* value (yellowness) compared to SEV-WS/WB. NORM-WS/WB had lower (P < 0.05) pH while NORM-WS/WB and SEV-WS samples showed lower (P < 0.05) drip loss when compared to SEV-WB and SEV-WS/WB. The results from this study showed that the severe degrees of WS and WB are associated with heavier and older birds, and thicker breast fillets. Occurrence of severe degrees of WS and/or WB can affect various raw meat quality factors, mainly color and water holding capacity.

Evaluation of increasing levels of a microbial phytase in phosphorus deficient broiler diets via live broiler performance, tibia bone ash, apparent metabolizable energy, and amino acid digestibility.

The objective was to investigate increasing concentrations of an evolved microbial phytase on male broiler performance, tibia bone ash, AME, and amino acid digestibility when fed diets deficient in available phosphorus (aP). Experiment 1 evaluated the effects of phytase during a 21 d battery cage study and Experiment 2 was a 42 d grow-out. Experiment 1 included six treatments; negative control (NC) with an aP level of 0.23% (starter) and 0.19% (grower), two positive controls (PC) consisting of an additional 0.12% and 0.22% aP (PC 1 and PC 2), and the NC supplemented with three levels of phytase (250, 500, and 2,000 U/kg). The NC diet reduced (P < 0.05) FC, BW, and bone ash. Phytase increased (P < 0.05) BW with 2,000 U/kg phytase yielding similar results to the PC2, and improved FCR and increased bone ash was observed at all phytase levels. Amino acid digestibility coefficients were increased (P < 0.05) with phytase at 250 U/kg. Phytase at all rates increased (P < 0.05) AME to levels similar level as PC diets. Linear regression analysis indicated average P equivalency values for BW and bone ash of 0.137, 0.147, and 0.226 for phytase inclusion of 250, 500, and 2000 U/kg, respectively. Experiment 2 included a PC consisting of 0.45%, 0.41%, and 0.38% aP for the starter, grower, and finisher, respectively; NC with reduced aP of 0.17%; and phytase at 500 and 2,000 U/kg. Phytase increased BW (P < 0.05) compared to the NC as 2,000 U/kg phytase resulted in further BW increases compared to the PC (starter and grower). Phytase improved FCR to levels comparable to the PC, with supplementation at 2,000 U/kg resulting in improvements beyond the PC in the starter phase. Amino acid digestibility coefficients were increased with phytase at 2,000 U/kg to levels comparable to that of the PC. These data confirm that the inclusion of phytase improves broiler performance and bone mineralization in aP reduced diets and levels beyond the traditional 500 U/kg can result in further improvements.

Absorption and digestive tract metabolism of 2-hydroxy-4-methylthiobutanoic acid in lambs.

Anabolic availability of the hydroxyl methionine analog, 2-hydroxy-4-methylthiobutanoic acid (HMTBA), given as oral doses to lambs, was quantified both directly as appearance in the portal vein and as synthesis to Met by digestive tract tissues. Eight lambs, prepared with vascular catheters in the mesenteric and portal veins plus the aorta, received twice daily for 7 d either 0.46 g or 2 g of HMTBA. On d 7, [1-13C]HMTBA was supplied as 1 oral dose while [methyl-2H3]Met was infused into the jugular vein. Peak absorption as HMTBA occurred 70 to 90 min after the oral dose. All digestive tract tissues converted HMTBA to Met, equivalent to 24% of the Met provided by the diet for the larger HMTBA dose. Overall, total availability of HMBTA averaged 17.9% of the dose (range 10.6 to 27.9%), with 12.5% (range 7 to 22%) as absorbed HMBTA and the remainder as Met synthesized by digestive tract tissues. Release of 13CO2 into the portal vein accounted for another 23% of the dose. In all digestive tract tissues, the d-isomer was present in a smaller proportion than in the dose. In terms of whole-body kinetics, HMTBA loss from the plasma followed first-order kinetics, with a mean biological half-life of 76 min. Using this value, a simple model was devised to estimate HMTBA absorption based on peripheral plasma samples. When compared with direct measures of absorption, the model gave a slope of 0.81 (R2 = 0.68) and offers a practical means to test HMTBA availability to animals.

Hepatic metabolism of 2-hydroxy-4-methylthiobutyrate in growing lambs.

This study was undertaken to determine how, and where, 2-hydroxy-4-methylthiobutyrate (HMTBA) can augment Met metabolism in lambs. Four lambs (initial body weight of 50 kg, SE = 2, and 6 mo of age) prepared with catheters in the mesenteric, portal, hepatic, and jugular veins plus the aorta, were fed at 1.5x maintenance on a grass hay, barley, fish meal, molasses/pre-mix (5:3:1:1, as fed) diet, supplied as hourly meals. Lambs were infused for 10 h with [methyl-2H3]Met (0.11 mmol/h) in a jugular vein and p-aminohippurate into the mesenteric vein. From 1 h onwards, successive 3-h infusions of saline (control), 0.55 mg/min (3.67 micromol/min), and 4.44 mg/min (29.6 micromol/min) of HMTBA were also infused into the mesenteric vein. Plasma, sampled continuously, was collected every 20 min during the last 60 min of each infusion. All infused HMTBA was recovered at the portal vein with 25% extracted subsequently by the liver. Portal appearance of total Cys and Met was unaltered by HMTBA infusion, but net splanchnic appearance of Cys increased (0.04, 0.08, 0.23 mmol/h, SEM = 0.05), whereas Met decreased (0.14, -0.01, -0.21 mmol/h, SED = 0.05). Despite this, arterial Met increased (27.0, 30.7, 51.5 microM, SEM = 2.1) as did Met irreversible loss rate (27.6, 28.7, 40.1 micromol/h, SEM = 0.51), equivalent to 40% of the HMTBA reentering the plasma after conversion to Met. These data indicate that, in ruminants, HMTBA is probably converted to Met within peripheral tissues; that is, where the metabolic need for Met exists.