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.

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.

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.

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.

Effect of copper, manganese, and zinc supplementation on the performance, clinical signs, and mineral status of calves following exposure to bovine viral diarrhea virus type 1b and subsequent infection.

Research has indicated that trace mineral (TM) supplementation may alter immune function and reduce morbidity associated with bovine respiratory disease. The objective of this experiment was to determine the influence of dietary Cu, Mn, and Zn supplementation on the performance, clinical signs, and TM balance of calves following a bovine viral diarrhea virus (BVDV) and (MH) combination respiratory pathogen challenge. Steers ( = 16; 225 ± 20 kg BW) from a single ranch were processed, weaned, and randomly pairwise assigned to either the TM-supplemented (MIN) or the control (CON) experimental treatments. The MIN calves received an additional 150 mg of Cu, 130 mg of Mn, and 320 mg of Zn daily and the CON calves received the basal diet with no additional Cu, Mn, or Zn supplementation. The basal diet contained sufficient Mn and Zn but inadequate Cu based on published nutrient requirements. After 46 d on the experimental treatments, all calves were naturally exposed to a heifer persistently infected with BVDV type 1b for 4 d and then subsequently intratracheally challenged with MH. Data were analyzed using the GLIMMIX procedure of SAS with sampling time serving as a repeated measure and calf serving as the experimental unit. The respiratory challenge was validated via increased BVDV type 1b antibody concentrations, MH whole cell and leukotoxin antibody concentrations, rectal temperatures (TEMP), and subjective clinical severity scores (CS). Calf performance ( ≥ 0.48) was not affected by TM supplementation. Mineral supplementation also did not impact the CS or TEMP of calves ( ≥ 0.53). There was a treatment × time ( < 0.001) interaction observed for liver Cu concentrations. The concentrations of Cu, Mn, Zn, and Fe within the liver; Cu, Mn, and Zn within the muscle; and Cu, Zn, and Fe within the serum were all impacted by time ( ≤ 0.03). Calves receiving the MIN treatment had greater ( < 0.01) liver Cu and Mn concentrations compared with CON calves. In contrast, serum Cu and Fe concentrations were increased ( ≤ 0.05) in CON calves compared with MIN calves. Mineral supplementation did not impact TM concentrations within the muscle ( ≥ 0.38). The supplementation of Cu, Mn, and Zn can improve the Cu and Mn status within the liver and serum of calves in response to a BVDV and MH challenge. When Cu is supplemented to calves receiving a marginally Cu-deficient diet, Cu status within the body is significantly improved.

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.

Multitrial analysis of the effects of copper level and source on performance in nursery pigs.

A multitrial analysis was conducted to evaluate the effect of different levels of Cu from either Cu(2-hydroxy-4-(methylthio)butanoic acid [HMTBa])2 or CuSO4 on growth performance in nursery pigs. Six nursery trials were conducted from 2007 to 2012 under the same commercial conditions with initial BW of 5.75 ± 0.41 kg at 21 ± 3 d of age; the trials lasted for 42 d with a 3-phase feeding program (7 d in Phase I, 14 d in Phase II, and 21 d in Phase III). Diets were medicated with antibiotics and supplemented with 3,000 mg/kg Zn as ZnO during phases I and/or II. Treatments included a basal diet without added Cu or according to the NRC (1998) and supplemental levels of Cu (50 to 250 mg Cu/kg diet) from either Cu(HMTBa)2 or CuSO4; HMTBa was supplemented to make diets isomethionine. Treatments from each trial included 6 or 9 replicate pens/treatment with 22 to 25 piglets/pen. Mixed model analysis was conducted in which trial was considered a random effect, Cu level was considered a continuous fixed effect, and Cu source was a fixed effect. The basal diet within trial and statistical tests of the intercept between sources were not different, resulting in fitting a common intercept mixed model to the overall responses across phases. Cumulative ADG and ADFI quadratically responded (P < 0.05) with increasing Cu supplementation; predicted optimal ADG and ADFI occurred at 174 and 119 mg/kg, respectively. Increasing Cu supplementation linearly improved G:F (P = 0.054). No differences between sources were observed in ADG or ADFI. Numerically, pigs fed Cu(HMTBa)2 had higher ADG and lower ADFI compared to pigs fed CuSO4, resulting in better G:F for pigs supplemented with Cu(HMTBa)2 compared to pigs supplemented with CuSO4 (P < 0.01). The linear slope for increasing Cu supplementation on G:F was 2.1-fold higher for Cu(HMTBa)2 than that of CuSO4, with larger differences occurring in Phase II. In conclusion, Cu supplementation in nursery diets resulted in improved performance and Cu(HMTBa)2 is more effective than CuSO4 in improving feed efficiency.

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.

Digestibility and retention of zinc, copper, manganese, iron, calcium, and phosphorus in pigs fed diets containing inorganic or organic minerals.

The objective of this experiment was to measure the apparent total tract digestibility (ATTD) and the retention rate of Zn, Cu, Mn, and Fe in pigs fed either inorganic or organic sources of Zn, Cu, Mn, and Fe. The experimental design was a randomized complete block design with a 2 × 3 factorial arrangement of treatments. There were 2 types of diets (corn grits-based or corn-soybean meal [SBM]-based diets) and 3 micromineral treatments (basal micromineral premix [BMM], inorganic micromineral premix [IMM], and organic micromineral premix [OMM]). The BMM contained no added Zn, Cu, Mn, or Fe; the IMM microminerals were provided as sulfates of Zn, Cu, Mn, and Fe at 40, 50, 20, and 100 mg/kg, respectively. The OMM contained the same levels of the 4 microminerals as IMM, but Zn, Cu, Mn, and Fe in this premix were provided by Zn(2-hydroxy-4-methylthio butanoic acid [HMTBa])2, Cu(HMTBa)2, Mn(HMTBa)2, and FeGly, respectively. Forty-eight barrows (initial BW: 31.1 ± 4.2 kg) were housed individually and allowed ad libitum access to the corn grits diet with BMM for 2 wk. All pigs were then moved to metabolism cages and randomly assigned to 1 of the 6 treatment diets with 8 replicates per diet. Fecal and urine samples were collected for 5 d following a 5-d adaptation period. Compared with corn grits diets, pigs fed corn-SBM diets had greater (P < 0.05) absorption and retention of Zn, Cu, and Mn but less (P < 0.05) ATTD of Zn and Cu. Compared with BMM, supplementation of IMM or OMM increased (P < 0.05) absorption, retention, ATTD, and retention rate of Zn, Cu, Mn, and Fe. Compared with IMM, adding OMM to the corn-SBM diet improved (P < 0.05) the absorption and retention of Cu and Mn and the ATTD of Cu, but these differences were not observed in the corn grits diets (interaction, P < 0.05). In addition, adding OMM to the corn-SBM diet increased (P < 0.05) absorption and retention of Zn and Fe and ATTD of Zn, Mn, and Fe compared with adding IMM to the corn-SBM diet. Supplementation of OMM also increased (P < 0.05) the ATTD and retention rate of P in corn-SBM diets. Results indicate that Zn(HMTBa)2 has greater digestibility and Cu(HMTBa)2 and Mn(HMTBa)2 have greater digestibility and retention rates compared with their inorganic sulfates, if included in a corn-SBM diet. Supplementation of organic microminerals also improves the digestibility of P in a corn-SBM diet.

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.

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.

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 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.

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.

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.

A multiple regression model approach to contrast the performance of 2-hydroxy-4-methylthio butanoic acid and DL-methionine supplementation tested in broiler experiments and reported in the literature.

The purpose of this paper was to compile all available literature comparing the relative performance of 2-hydroxy-4-methylthio butanoic acid (HMTBA) with DL-methionine (DLM) in broiler chickens and using multiple regression techniques, to estimate the predicted dose responses and relative performance of the 2 Met compounds for gain and feed conversion (FC). A database was developed that contained all available broiler studies in which HMTBA and DLM were both present in the same study; weight gain was recorded; Met addition, age of birds, and duration of study were defined; and an unsupplemented control treatment was present. Sixty-two references complied with these criteria and included 100 experiments with 427 observations for HMTBA and 411 for DLM. Multiple regression analysis of the database was used to identify the experimental and dietary conditions that contributed to the gain and FC responses of each source of Met activity. All identified variables contributed similarly to each Met source prediction model and both gain and FC models described a quadratic dose response. Under the average conditions of the database, the predicted responses for gain and FC models did not significantly differ between HMTBA and DLM. However, a trend was observed (P < or = 0.1) for the peak gain response for HMTBA to be numerically greater than DLM, suggesting benefits of HMTBA over DLM in the region of supplementation that is commercially relevant. The experimental and nutritional conditions that contribute to the response to HTMBA and DLM were identified and are discussed in the paper. This statistical approach provided a means to summarize the results obtained from a multitude of studies conducted over the last 5 decades and has provided a meaningful estimate of the relative performance of the 2 sources of Met activity. The lack of differences between the 2 predicted models under experimental and commercial conditions supports an overall conclusion of equal performance of DLM and HTMBA when compared on an equal molar basis.

Rumen degradation and availability of various amounts of liquid methionine hydroxy analog in lactating dairy cows.

Ruminal escape of various amounts of methionine hydroxy analog [D,L-2-hydroxy-4-(methylthio)-butanoic acid (HMB)] was measured in an experiment designed as a 4 x 4 Latin square using four lactating dairy cows with cannula in the rumen and duodenum. The cows were fed a diet composed of corn silage, alfalfa haylage, rolled barley grain, canola meal, and blood meal, three times per day. The cows were fed the liquid analog each day for 1 wk before the experiment was started. On the day of the experiment, each cow received an intraruminal bolus dose of 0, 25, or 50 g of the liquid analog (Alimet feed supplement, 88% HMB) or 51.2 g of a dry calcium salt of the analog (86% HMB; MHA) mixed with 0.5 kg of ground barley grain. A liquid phase marker (Co-EDTA) was administered as a bolus dose into the rumen at the time of administration of the methionine hydroxy analogs. Rumen and duodenal contents, and blood serum were collected at 0, 1, 3, 6, 9, 12, and 24 h relative to the time of dosing. Rumen and duodenal samples were analyzed for Co and HMB, and serum was analyzed for free methionine. Fractional rate constants for the passage of the liquid marker (k(p)) and the decline of HMB concentration in the rumen (k(rHMB)) were determined by nonlinear regression. Liquid passage from the rumen was similar among the four analog treatments (0.136 +/- 0.012/h; mean +/- SEM). Ruminal escape of HMB as a percentage of the dose (100% x k(p)/k(rHMB)) did not differ between cows receiving 25, 50, and 51.2 g of the methionine analogs (42.5, 41.0, and 34.9 +/- 9.0%, respectively) and averaged 39.5%. Duodenal appearance of HMB as a percentage also did not differ between cows receiving 25, 50, and 51.2 g of the methionine analogs (16.2, 26.8, and 22.7%, respectively) and averaged 22%. Omasal absorption of HMB was variable ranging from 12.3 to 26.3% and averaged 17.6%. Serum methionine concentration peaked at 3 and 6 h after dosing and increased in proportion to the amount of the analog administered. It was concluded that 39.5% of the methionine hydroxy analog escaped rumen degradation, the percentage of the dose that escaped the rumen was not affected by the amount or form of the methionine analog fed, and the analog that escaped ruminal degradation was likely absorbed and metabolized to methionine.

The effect of dietary energy source during mid to late lactation on liver triglyceride and lactation performance of dairy cows.

Control [1.61 Mcal of net energy for lactation (NEL)/kg of dry matter (DM)], high grain (1.70 Mcal of NEL)/kg of DM), or high fat [1.70 Mcal of NEL/kg of DM with 2.3% tallow (DM basis)] diets were fed to 43 cows (150 +/- 3.1 d in milk) during mid to late lactation to determine effects on performance characteristics, metabolic parameters, or both during mid to late lactation, the dry period, and the first 100 d of the next lactation. All cows received identical diets during the dry period and during early lactation. Increasing the energy density of the diets during mid to late lactation increased DM intake (DMI), plasma nonesterified fatty acid concentration, milk production, and milk protein yield. Compared with the high grain diets, fat supplementation decreased DMI and the percentage of milk protein but increased plasma nonesterified fatty acid concentration without causing elevation of liver triglyceride at the end of mid to late lactation. Increased energy density of the diets did not affect body condition score during mid to late lactation. There were no residual effects for any of the treatments on DMI, lactation performance, or body weight in the subsequent lactation. However, energy supplementation during mid to late lactation increased liver triglyceride content after calving. Compared with high fat diets, high grain diets fed during mid to late lactation increased plasma beta-hydroxy-butyrate concentration in the subsequent lactation. High energy diets fed during mid to late lactation may influence lipid metabolism during the following lactation.