Search

Five experiments were conducted to evaluate the lysine (Lys) requirements of lactating sows. All diets were formulated to be isocaloric 3.46 Mcal ME/kg and met or exceeded National Research Council recommendations. In all studies, sow feed intake, body weight loss/gain, subsequent reproduction, and litter growth rate (LGR) were evaluated. The data were analyzed as randomized complete block design using generalized linear model in SAS with parity as a block. Two hundred and sixty-four primiparous sows (PIC Camborough 22) were randomly allotted to one of five lactation treatments (total Lys of 0.95%, 1.05%, 1.15%, 1.25%, and 1.35%) in Exp. 1 from August 2005 through October 2005. As daily total dietary Lys intake increased from 52.10 to 77.53 g, piglet ADG and daily litter gain linearly improved (P < 0.01). From February 2007 through April 2007, 336 multiparous sows (parity 4 and older, PIC Camborough 29) were randomly allotted to one of five lactation treatments (total Lys 0.85%, 0.95%, 1.05%, 1.15%, or 1.25%) in Exp. 2. As dietary total Lys increased from 0.85% to 1.25% of the diet, there were no significant differences in litter performance, such as ADG, daily litter gain, and the number of pigs weaned. Experiment 3 was conducted from October 2008 through January 2009. Two hundred and seventy-nine primiparous gilts (PIC Camborough 29) were randomly allotted to one of five lactation treatments (total Lys 1.14%, 1.25%, 1.35%, 1.46%, and 1.57%). Actual total Lys intakes increased from 56.74 to 77.12 g/d. Feeding total dietary Lys quadratically decreased (P < 0.01) weaning-to-estrus interval and increased percentage bred by 10 d (P = 0.02). In Exp. 4, 200 sows (parity 4 and older, PIC Camborough 29) were randomly allotted to one of five treatments (0.85%, 0.95%, 1.05%, 1.15%, or 1.25% total Lys) from January 2008 through March 2008. As dietary total Lys increased from 42.40 to 66.15 g/d, sow body weight and LGRs were not influenced by dietary total Lys intakes. In Exp. 5, 324 parity 3 sows (PIC Camborough 29) were randomly allotted to one of five treatments (0.77%, 0.92%, 1.08%, 1.23%, and 1.38% total Lys) from August 2009 through October 2009. As daily dietary total Lys intake increased from 39.44 to 67.32 g, the percentage of sows bred by 10 d increased (P = 0.02), as well as the LGR. A broken-line quadratic regression analysis demonstrated that the total Lys requirement for LGR for parity 1 females is calculated as 72.68 − [6.04 × (3.55 − LGR)] and for parity 3+ females as 92.03 − [11.9 × (4.24 − LGR)].

Background The use of feed grade amino acids can reduce the cost of lactation feed. With changing genetics, increasing feed costs, and higher number of pigs weaned with heavier wean weights further evaluation of higher inclusion levels of feed-grade amino acid in lactation diets than previously published is warranted. Two experiments (Exp.) were conducted to determine the optimal inclusion level of L-lysine HCl to be included in swine lactation diets while digestible lysine levels remain constant across dietary treatments and allowing feed grade amino acids to be added to the diet to maintain dietary ratios relative to lysine to maximize litter growth rate and sow reproductive performance. Furthermore, the studies were to evaluate minimal amino acid ratios relative to lysine that allows for optimal litter growth rate and sow reproductive performance. Results Exp. 1: Increasing L-lysine HCl resulted in similar gilt feed intake, litter, and reproductive performance. Average litter gain from birth to weaning was 2.51, 2.49, 2.59, 2.43, and 2.65 kg/d when gilts were fed 0.00, 0.075, 0.150, 0.225, and 0.30% L-lysine HCl, respectively. Exp. 2: The average litter gain from birth to weaning was 2.68, 2.73, 2.67, 2.70, and 2.64 kg/d (P

SUMMARY The objective of this study was to investigate the impact of long-term inclusion of the trace elements zinc, copper, and manganese chelated with the hydroxy analogue of methionine on layer performance, eggshell quality, tibia breaking strength, and immune response. A total of 216 Hy-Line W-36 laying hens were allocated to 6 treatments with 36 pens/treatment and 1 hen/cageusingarandomizedcompleteblockdesign.Therewere6treatmentswithsupplemental Zn-Cu-Mn, as follows: T1 0-0-0 ppm, T2 20-5-20 ppm as sulfates, T3 20-5-20 ppm as chelates, T4 40-10-40 ppm as sulfates, T5 40-10-40 ppm as chelates, and T6 80-10-80 as sulfates. The feeding of dietary treatments started at wk 24 pullet age and measurements of the key parameters were made from wk 44 to 80. Overall results (one-way ANOVA) indicated a significant treatment effect (P 0.05) response to T1 and T6 but different (P < 0.05) from T2. Factorial analysis of the data showed an improvement in shell breaking strength (P < 0.05 at wk 68), shell thickness (P = 0.08 at wk 68; P = 0.03 at wk 74), tibia breaking strength (P = 0.07) and antibody (Ab) titers to SRBCs (P < 0.05 at wk 63; 1 wk after secondary antigen challenge) in hens fed chelated trace mineral when compared to inorganic trace minerals. In summary, feeding laying hens’ diets containing supplemental chelated trace minerals showed improvements in eggshell thickness and immune response when compared to inorganic salts at specific time points measured during the latter part of the laying cycle.

The objective of this study was to compare the gain-response curve to dietary levels of 2-hydroxy-4(methylthio) butanoic acid (HMTBA) and DL-Met (DLM) across 4 floor pen trials in which different diets were used. Six replicates of 38 or 41 birds per pen (trials 1 to 2 and 3 to 4, respectively) were used in a 2 x 3 factorial arrangement. A control with 12 replicates was also included. The 2 Met sources were fed at 3 equimolar levels equally spaced, with the highest level added at requirements from 1 to 48, 49, 43, or 49 d for trials 1, 2, 3, and 4, respectively. Commercial-type TSAA-deficient control diets contained sorghum, wheat, corn, or corn plus meat and bone meal for trials 1, 2, 3, and 4, respectively. Performance improved at all times for most parameters after supplementing with HMTBA or DLM (P0.05). No differences were found in the birds fed HMTBA or DLM at any age and trial (P0.05), except for trial 1, in which 17-d-old birds performed better when fed HMTBA than DLM (P0.05). In each trial, linear, quadratic, and exponential regressions were conducted upon the gain response of birds fed HMTBA and DLM separately. Equations with better goodness of fit were used to compare the estimated gain responses to feeding HMTBA vs. DLM. In 3 trials, the shape of the gain-response curve differed when feeding HMTBA vs. DLM. In trials 3 and 4, feeding HMTBA at commercial levels resulted in greater gain responses than DLM (P0.05), whereas, in trials 2 and 4, at very deficient levels, DLM-fed birds outperformed those fed HMTBA (P0.05). When the 4 trials were combined, the dose-response curve with the best goodness of fit was linear for HMTBA and quadratic for DLM. It can be concluded that the 2 Met sources have a different dose-response form, HMTBA could outperform DLM at commercial levels, and DLM could outperform HMTBA at deficient levels.

Three experiments were conducted to determine the true ileal digestible (TID) Lys and sulfur AA (SAA) requirement and to compare the bioefficacy of 2-hydroxy-4-(methylthio)butanoic acid (HMTBA) and dl-MET as Met sources in nursery pigs. Experiment 1 included 2 studies: 1 was 662 nursery pigs (Triumph 4 x PIC C22; initial BW 12.2 +/- 0.18 kg) allotted to 1 of 5 dietary treatments with TID Lys concentrations ranging from 1.10 to 1.50%; and the second study was 665 nursery pigs (Triumph 4 x PIC C22; initial BW 12.3 +/- 0.18 kg) allotted to 1 of 5 dietary treatments with TID SAA concentration ranging from 0.63 to 0.90%. In Exp. 2, 638 nursery pigs (Triumph 4 x PIC C22; initial BW 13.0 +/- 0.16 kg) were allotted to the same 5 SAA dietary treatments as in Exp. 1. In Exp. 3, 1,232 pigs (Triumph 4 x PIC C22; initial BW 11.0 +/- 0.30 kg) were allotted to 1 of 7 dietary treatments. The basal diet (diet 1) was supplemented with high concentrations of synthetic AA but no Met; this resulted in a dietary concentration of TID Lys of 1.30% and TID SAA of 0.50%. Diets 2 to 7 were the basal diet supplemented with 3 equimolar levels of HMTBA or dl-MET to provide TID SAA concentrations of 0.56, 0.62, and 0.68%, respectively. In Exp. 1, increasing TID Lys from 1.10 to 1.50% increased ADG (quadratic; P < 0.05) and improved G:F (linear; P < 0.002). The pooled data of Exp. 1 (SAA study) and Exp. 2 indicated that increasing TID SAA from 0.63 to 0.90% increased ADG (quadratic; P < 0.01) and improved G:F (quadratic; P < 0.01). Various methods of analyzing the growth response surface indicated that the optimal TID Lys concentration ranged from 1.28 to 1.32% for ADG (Exp. 1), and the optimal TID SAA concentration ranged from 0.73 to 0.77% for ADG and 0.80 to 0.83% for G:F (pooled Exp. 1 and 2), respectively. In Exp. 3, increasing TID SAA concentrations from 0.50 to 0.68% resulted in a linear improvement of ADG (P < 0.001), ADFI (P < 0.05), and G:F (P < 0.001). The best fit comparison of HMTBA and dl-MET was determined by the Schwartz Bayesian Information Criteria index, which indicated the average relative efficacy of HMTBA vs. dl-MET was 111%, with 95% confidence interval of 83 to 138%, within the range of TID SAA tested. Thus, the TID Lys and SAA requirements of modern lean-genotype pigs from 11- to 26-kg were greater than the 1998 NRC recommendations, and both HMTBA and dl-MET as Met sources can supply equimolar amounts of Met activity.

Four experiments were conducted to determine the ideal ratio of true ileal digestible (TID) sulfur AA to Lys (SAA:LYS) in nursery pigs at two different BW ranges using both DL-Met and 2-hydroxy-4-(methylthio)-butanoic acid (HMTBA) as Met sources. In Exp. 1, 1,549 nursery pigs (Triumph 4 x PIC Camborough 22; initial BW 8.3 +/- 0.08 kg) were allotted to one of nine dietary treatments. The basal diet (Diet 1) was a semicomplex corn-soybean meal-based diet (1.32% TID Lys) with no supplemental HMTBA or DL-Met (47.7% TID SAA:LYS). Diets 2 to 9 consisted of the basal diet supplemented with four equimolar levels of DL-Met or HMTBA (52.7, 57.7, 62.7, and 67.7% TID SAA:LYS). In Exp. 2, 330 nursery pigs (Triumph 4 x PIC Camborough 22; initial BW 11.4 +/- 0.10 kg) were allotted to one of nine dietary treatments. The basal diet (Diet 1) was a corn-soybean meal-based diet (1.15% TID Lys) with no supplemental HMTBA or DL-Met (49% TID SAA:LYS). Diets 2 to 9 consisted of the basal diet supplemented with four equimolar levels of DL-Met or HMTBA (54, 59, 64, and 69% TID SAA:LYS). In Exp. 3, 1,544 nursery pigs (Triumph 4 x PIC Camborough 22; initial BW 12.4 +/- 0.13 kg) were allotted to one of nine dietary treatments as in Exp. 2. In Exp. 4, 343 nursery pigs (Genetiporc; initial BW 12.8 +/- 0.56 kg) were allotted to one of six dietary treatments. The basal diet (Diet 1) was a corn-soybean meal-based diet (1.05% TID Lys) with no supplemental DL-Met (49% TID SAA:LYS). Diets 2 to 5 consisted of the basal diet supplemented with four levels of DL-Met (54, 59, 64, and 69% TID SAA:LYS), and Diet 6 was the basal diet supplemented with one equimolar level of HMTBA to satisfy 59% TID SAA:LYS ratio. In all experiments, increasing the TID SAA:LYS ratio resulted in quadratic improvements in ADG (P < or = 0.09) and G:F (P < or = 0.05). Three different methods were used to estimate the optimal TID SAA:LYS ratio for each experiment. The two-slope broken-line regression model, x-intercept value of the broken-line and quadratic curve, and 95% of upper asymptote across the four experiments indicated that the average optimal TID SAA:LYS ratios were 59.3, 60.1, and 57.7% for ADG and 60.6, 61.7, and 60.1% for G:F, respectively. Thus, the optimal TID SAA:LYS ratio for 8- to 26-kg pigs based on the average value of these three estimates was 59.0% for ADG and 60.8% for G:F.

The objective of this research was to evaluate the effect of early feeding on the development of the immune system in broiler chicks. A hydrated nutritional supplement formulated specifically for the first 2 to 3 days of post-hatch life was provided to the chicks on the day of hatch and the 2 subsequent days. The nutritional content of this supplement was optimized to achieve maximum performance at 6 wk following ad libitum consumption of starter feed and water. Control hatchlings received neither feed nor water. After the initial treatment, all birds were fed the same corn-soy diet ad libitum. Immune development was assessed by measuring bursa weight, biliary immunoglobulin A (IgA) levels, appearance of germinal centers in the cecal tonsils, and resistance to an oral challenge with coccidial oocysts. Data indicate that provision of the optimum balance of nutrients immediately after hatch result in heavier bursa weights, earlier appearance of biliary IgA and germinal centers, and an improved resistance to disease challenge.

Two experiments were conducted to assess the ability for recombinant porcine somatotropin (rpST)-treated pigs to perform and cope with the demands of hot and cold environments. In the first experiment, finishing pigs were exposed to either a thermoneutral (TN; 18 to 21 degrees C) or a hot environment (H; 27 to 35 degrees C) for 35 d. In the second experiment, pigs were exposed to a TN or cold environment (C; 5 to 15 degrees C). The rpST delivered by a 6-wk prolonged-release system had no effect on ADG, whereas both H and C reduced ADG by 29.4 and 11.8%, respectively. In the first experiment, rpST-treated pigs consumed 17.6% less feed than control pigs, whereas rpST-treated pigs in H consumed 24.4% less feed than rpST-treated pigs in TN. Overall feed/gain ratios through the first 4 wk of both studies were improved by 21.8 and 14%, respectively, by rpST (P < .05) and were 24.3% poorer in C (P < .05) than in H. The changes in blood concentrations of pST, IGF-I, and IGF-II associated with rpST were not influenced by the different environments. Total body composition of rpST-treated pigs had increased amounts of protein (P < .05) and decreased amounts of fat (P < .05); H further reduced fat (P < .05). The C resulted in reduced protein content (P < .05). No evidence of thermal imbalance due to rpST was found as assessed by rectal temperature, respiration rate, and heat production estimated by indirect calorimetry and chemical analysis.

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

A study was conducted to compare the effects of a single 100-mg recombinant porcine somatotropin (rpST) implant on performance, carcass characteristics, and blood hormones and metabolites of 40 finishing pigs exposed to either a thermoneutral (TN; 18 to 21 degrees C) or hot environment (H; 27 to 35 degrees C) for 28 or 35 d. Pigs in H gained at a slower rate (P less than .01) than pigs in TN. Control and rpST-treated pigs gained at similar rates in respective environments. The rpST-treated pigs consumed 13% less feed (P less than .01) than the control pigs in both environments, and pigs in H consumed 19% less feed (P less than .01) than pigs in TN. Feed efficiency for rpST-treated pigs was 15% better (P less than .01) than that for control pigs; environment had no effect on feed efficiency. When slaughtered, pigs treated with rpST had less (P less than .01) leaf fat and less (P less than .01) 10th rib backfat than control pigs. Pigs in H had a lower (P less than .01) final BW and less leaf fat and backfat than pigs in TN. The rpST and H had various effects on blood hormones and metabolites. The results demonstrated that the benefits of this form of rpST treatment achieved under TN were also achieved in H with no interactions between the hormone and environment.

Four experiments using 580 barrows and 580 gilts (Study 1) and seven experiments using 500 barrows and 500 gilts (Study 2) were conducted at various geographical locations in the United States to determine the dose response of a pelleted form of porcine somatotropin (pST) relative to ADG, feed/gain (F/G), and percentage of carcass protein. Average initial weights for Studies 1 and 2 were 67.6 and 72.6 kg, respectively, and four pigs/pen were slaughtered when they achieved weights of 106.5 to 111.0 kg. In Study 1, pigs were implanted subcutaneously with pelleted pST doses of 0, 12, 24, 36, or 48 mg/wk and self-fed a corn-soybean meal diet containing 13.75% CP. Study 2 included two control groups self-fed a diet containing either 13.75 or 17% CP with added lysine. The pST-treated pigs were administered 12, 24, or 36 mg/wk, and all were offered the 17% CP diet. The pST treatments in Study 1 resulted in a linear reduction (P less than .05) in average daily feed intake (ADFI) and a quadratic (P less than .05) improvement in F/G and percentage of carcass protein. The pST treatments in Study 2 resulted in a linear reduction in ADFI (P less than .05), a linear improvement in F/G, and a quadratic increase in the percentage of carcass protein (P less than .05). Average daily gain was not affected in either study with this form of pST. The greatest increase in efficiency of lean gain was observed with the 36-mg dose for both Study 1 (9.4%) and Study 2 (10.8%). In Study 1, the force required to shear cores of the longissimus muscle was increased linearly with pST treatment (P less than .05). There was a similar linear increase in Study 2 with pST treatment (P less than .05); however, there was also an effect of sex (P less than .05) on shear force (gilts greater than barrows) that was similar in magnitude to that observed for pST treatment. Differences in sensory evaluation because of pST were minor and of the same magnitude as those observed between barrows and gilts. It was therefore concluded that weekly administration of pST improved F/G and percentage of carcass protein with no detrimental effects on palatability of cooked lean pork.

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 less than or equal to 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.

Seven hundred and twenty hatchling broilers were allotted to 12 treatment groups. Groups 1 and 2 were fasted for 48 h posthatch; groups 3 and 4 were fasted for 48 h followed by ad libitum access to a 1% glutamine (Gln) diet; groups 5 and 6 had ad libitum access to a common diet; groups 7 and 8 had access to a 1% Gln diet posthatch; groups 9 and 10 were fed regular Oasis hatchling supplement; and groups 11 and 12 were fed Oasis sprayed with 1% Gln for the first 48 h posthatch. The birds in treatment groups 2, 4, 6, 8, 10, 11, and 12 were vaccinated with Eimeria maxima posthatch, and all birds were orally challenged with high dose E. maxima on d 22. During the first 2 wk, birds in group 7 had the highest gain and feed efficiency among treatments (P0.01). Compared with birds in the nonGln groups, birds in the Gln group had higher gain, feed efficiency, and livability (P0.05). Among the Fast (groups 1 to 4), Feed (groups 5 to 8), and Oasis (groups 9 to 12) groups, birds in the Feed groups had the highest gain during d 0 to 21 (P0.01). During d 22 to 28, birds in the Fast groups had the lowest BW and livability (P0.01), and the nonvaccinated birds had lower gain and feed efficiency relative to vaccinated birds (P0.01). Birds in the Feed and Oasis groups had higher villus height (VH) of mid small intestine than Fast groups at d 2 and 7 (P0.05), and nonvaccinated birds had higher VH than vaccinated birds (P0.01) at d 7 after hatch. On d 14, there were differences in serum interferon-gamma (P0.05) levels among treatments. During d 22 to 28, vaccinated birds had lower lesion scores in the mid small intestine than nonvaccinated birds (P0.01), and birds in the Feed or Oasis groups had lower lesion scores compared with the Fast groups (P0.02). These results indicated the importance of immediate access to feed posthatch, the beneficial effects of feeding Oasis hatching supplement and Gln after hatch, as well as the necessity of the vaccination program against coccidiosis challenge.

Animal feeding studies were conducted with rats, broiler chickens, catfish and dairy cows as part of a safety assessment program for a soybean variety genetically modified to tolerate in-season application of glyphosate. These studies were designed to compare the feeding value (wholesomeness) of two lines of glyphosate-tolerant soybeans (GTS) to the feeding value of the parental cultivar from which they were derived. Processed GTS meal was incorporated into the diets at the same concentrations as used commercially; diary cows were fed 10 g/100 g cracked soybeans in the diet, a level that is on the high end of what is normally fed commercially. In a separate study, laboratory rats were fed 5 and 10 g unprocessed soybean meal 100 g diet. The study durations were 4 wk (rats and dairy cows), 6 wk (broilers) and 10 wk (catfish). Growth, feed conversion (rats, catfish, broilers), fillet composition (catfish), and breast muscle and fat pad weights (broilers) were compared for animals fed the parental and GTS lines. Milk production, milk composition, rumen fermentation and nitrogen digestibility were also compared for dairy cows. In all studies, measured variables were similar for animals fed both GTS lines and the parental line, indicating that the feeding value of the two GTS lines is comparable to that of the parental line. These studies support detailed compositional analysis of the GTS seeds, which showed no meaningful differences between the parental and GTS lines in the concentrations of important nutrients and antinutrients. They also confirmed the results of other studies that demonstrated the safety of the introduced protein, a bacterial 5-enolpyruvyl-shikimate-3-phosphate synthase from Agrobacterium sp. strain CP4.

The objective of these experiments was to study the effect of intermittent high temperature (IHT) on performance of broilers fed different sources of methionine activity. Two 20-d experiments were conducted in which individually caged 28-d-old cockerels were exposed to a 5-d period of constant high temperature (HT, 30 to 32 C) followed by an equal period of thermoneutral (TN) temperatures (22 C) with the 10-d temperature cycle repeated twice. Birds held at 22 C were TN controls. Grower diets contained 3,275 kcal/kg ME and 20% CP and were supplemented with either 2-hydroxy-4-(methylthio)butanoic acid (HMB, Alimet Feed Supplement) or DL-Met up to a maximum of .88 to .90% total sulfur amino acids (TSAA). In Experiment 1, gain:feed but not average daily gain was greater (P < .05) for HMB than DL-Met birds subjected to IHT (.451 vs .413, respectively), but no treatment differences were observed for TN birds. Results of Experiment 2 demonstrated a linear response to HMB and DL-Met dose in TN (P < .01); however, only HMB-supplemented birds responded similarly in IHT (P < .01). These results are consistent with lower availability of DL-Met as a result of IHT. In vitro experiments indicated that capacity for uptake of DL-Met into intestinal epithelial cells was reduced in heat-stressed birds. Uptake of D-Met was more severely affected than was L-Met. Consequently, a third performance experiment compared the ability of D-Met and L-Met to support growth under conditions of HT. The results indicated that the effect of HT on broiler performance was mediated through reduced utilization of D-Met.

An experiment was conducted with 24 crossbred (Landrace x Yorkshire x Duroc) finishing pigs (mean BW 85 kg) to study the effects of a single 100-mg recombinant porcine somatotropin (rpST) implant on the tissue mineral status of pigs exposed to either a thermoneutral (TN; 18 to 21 degrees C, 50 to 55% RH) or cold (C; 5 to 15 degrees C, 50 to 70% RH) environment until BW averaged 110 kg. The implants used in this study delivered an average 2.4 to 2.5 mg of rpST/d during the course of the study. Control pigs were implanted with a placebo. All diets were supplemented with minerals at levels that either met or exceeded the requirements of an 85-kg pig. At slaughter (mean BW 110 kg), tissues were collected and analyzed for selected macro- and microminerals. Pigs treated with rpST had higher (P < .05) Ca concentrations and total Ca in liver and kidney and higher (P < .05) Ca concentrations in muscle. Total P, Mg, Na, and K were all higher (P < .05) in the liver and kidneys of rpST-treated pigs. In general, rpST had little influence on Cu, Zn, and Fe in tissues. No consistent trend was evident in the response of tissue minerals to environmental temperature. Results indicated that pigs treated with rpST and supplemented with adequate minerals accumulated more minerals in certain tissues than did pigs not given rpST.

We compared the effectiveness of 2-hydroxy-4-(methylthio) butanoic acid (HMB) and DL-methionine (DLM) as sources of L-methionine activity in methionine-deficient primary cultures of pig liver cells and methionine-deficient early-weaned pigs. Viable hepatocytes were obtained from minced pig liver and maintained in a high density, differen- tiated, nonproliferation cell culture system. Culture medium was supplemented with HMB, DLM, or L- methionine, and cells were pulse-dosed with L- ( 14 C(U))leucine for 24 h to determine the level of protein synthesis. Leucine incorporation per milligram of protein indicated a six-to eightfold increase in protein synthesis ( P < .01) with methionine levels between 5 and 10 mM, regardless of source of methionine activity. Two 24-pen replicate methionine dose titrations were conducted with 95 early-weaned commercial crossbred pigs. The pelleted corn, dried whey, and porcine plasma basal diet contained 1.5% lysine, .23% methionine, and .48% cystine and was supplemented with 0, .05, or .10% methionine activity as DLM or HMB for 21 d. There was a 134, 104, and 61% increase ( P < .01) in cumulative ADG for each successive week on study with a 30 and 19% improvement in feed/gain ( P < .01) after 7 and 14 d. Performance responses due to source of methionine activity did not differ and slope ratio potency determi- nations (gain vs intake of methionine source) of HMB vs DLM indicated a 119, 111, and 95% relative activity for cumulative weekly performance. These results support the hypothesis that HMB and DLM provide equimolar levels of methionine activity in swine.