Effect of dietary protein and lysine fluctuations in the absence and presence of ractopamine on performance and carcass quality of late-finishing pigs.

Two experiments with finishing pigs were conducted to evaluate the effects of fluctuating dietary CP levels and ractopamine on performance and carcass traits. In Exp. 1, a total of 408 finishing pigs (mixed sex) were assigned to 1 of 4 protein regimens. Average initial and final BW were 89 and 123 kg, respectively. Pigs on treatments 1 to 4 were fed 16, 11, 16, and 13% CP from wk 0 to 2, respectively. From wk 2 to 5, the pigs on regimens 1 to 4 were then fed 15, 18.33, 18, and 20% CP, respectively, with regimens 3 and 4 also containing supplemental ractopamine (9.9 mg/kg) from wk 2 to 5. Overall (wk 0 to 5), BW gain, G:F, loin depth, percentage of lean, and dressing percentage were improved (P < 0.05) in pigs on regimens 3 and 4 compared with those on regimens 1 and 2. No statistically significant overall (wk 0 to 5) protein sequence regimen differences occurred between the standard regimens (1 and 3) and the low-high CP regimens (2 and 4). Experiment 2 involved 172 finishing pigs (mixed sex) in 2 protein regimens. Average initial and final BW were 91 and 136 kg, respectively. The diets consisted of 1) a control (16% CP from d 0 to 14, 18% CP + 4.95 mg of ractopamine/kg from d 14 to 24, and 18% CP + 9.9 mg of ractopamine/kg from d 24 to 35; 2) a low-high CP regimen (12.5% CP from d 0 to 14, 20.33% CP + 4.95 mg of ractopamine/kg from d 14 to 24, and 20.33% CP + 9.9 mg of ractopamine/kg from d 24 to 35. From d 0 to 14, pigs fed the low CP diet (12.5% CP) had reduced (P < 0.05) BW gain and G:F compared with those fed the control diet (16% CP). In contrast, from d 14 to 35, pigs on the low-high regimen had improved (P < 0.08) BW gain and G:F compared with pigs on the control regimen. Despite the wide dietary CP fluctuations for pigs in Exp. 2, performance and carcass traits were similar for both regimens over the 35-d test period. These data indicate that pigs fed deficient levels of CP and Lys for 14 d, followed by increased levels of CP and Lys during a subsequent 21-d period can recover and achieve growth performance and carcass merit equal to that achieved with a conventional protein feeding regimen.

Effect of supplemental vitamins and trace minerals on performance and carcass quality in finishing pigs.

Two trials with finishing pigs (PIC line 355 x Camborough 22) were conducted to evaluate the effects of vitamin and trace mineral (VTM) supplement deletions on performance, carcass quality, and tissue nutrient levels. Trial 1, a 3 x 2 factorial arrangement of treatments involving three VTM supplement regimens and two stress regimens, was conducted for 12 wk with 252 pigs (mixed sex). Average initial weight of pigs was 54 kg. The VTM regimens consisted of control (adequate level of VTM throughout trial), VTM deleted for the final 6 wk, and VTM deleted for entire 12 wk of the trial. The stress regimens consisted of leaving half the treatments in their original location or moving the other half of the treatments to a new pen location every 3 wk. There were three replications (pens) per treatment with 14 pigs per pen (0.80 m2). Diets were medicated with bacitracin methylene disalicylate. Overall, there were no treatment differences (P > 0.05) for ADG, ADFI, gain:feed ratio, longissimus muscle area, or last-rib backfat. However, there was a greater than 75% decrease (P < 0.001) in vitamin E content of longissimus muscle from deleting VTM for 6 or 12 wk. Trial 2, a 3 x 2 factorial arrangement of treatments involving three VTM regimens and two genders, was conducted for 12 wk with 306 pigs. Average initial weight of pigs was 58 kg. The VTM regimens were identical to those used in Trial 1. Each treatment consisted of three gender replications of 17 pigs per pen (0.66 m2), and all diets were unmedicated. Overall, pigs fed diets without VTM for 12 wk had lower (P < 0.06) ADG than those fed the control diets. Vitamin E content of the ham muscle was reduced by greater than 50% (P < 0.001) when pigs were fed diets without VTM for 6 or 12 wk compared with those fed the control diet. Concentrations of copper in ham muscle were reduced (P < 0.05) in pigs fed diets without VTM. These data suggest that deleting VTM during the finishing stage markedly lowers the vitamin E content of pork muscle.

Comparative effects of individual amino acid excesses when added to a corn-soybean meal diet: effects on growth and dietary choice in the chick.

Six experiments were conducted with 8-d-old crossbred chicks to evaluate the effects of 4% excesses of DL-methionine (Met), L-phenylalanine (Phe), L-tryptophan (Trp), L-lysine (Lys), L-histidine (His), L-threonine (Thr), L-isoleucine (Ile), L-arginine (Arg), L-valine (Val) or L-leucine (Leu) on growth or dietary "choice" (i.e., self-selection) when added to 23% protein corn-soybean meal (C-SBM) diets. Arginine and His were supplied as the free base and Lys as Lys X acetate to avoid acid-base problems. In the growth studies, weight gain was reduced 92, 79, 53, 50, 47, 31, 29, 15, 9, 4 and 0% by additions of 4% Met, Phe, Trp, His, Lys, Tyr, Thr, Ile, Arg, Val and Leu, respectively. Improvements (P less than .05) in weight gain, feed intake and gain/feed occurred by addition of 1% Arg to the C-SBM diet supplemented with 4% excess Phe or Tyr. Addition of 1% Arg to the C-SBM diet supplemented with 4% excesses of most of the other amino acids also tended to improve performance, although diets imbalanced with Lys, Val or Leu did not respond to supplemental Arg. Self-selection studies revealed that chicks preferred the C-SBM diet containing 4% excess Lys over diets containing 4% excesses of Met, Thr, Arg or Trp. Moreover, chicks preferred diets with 4% excess Met, Thr or Arg over those containing an equal excess of Trp. When given a choice between the C-SBM diet and this diet supplemented with 4% Leu, chicks consumed similar quantities of both diets.

Urea cycle metabolism: effects of supplemental ornithine or citrulline on performance, tissue amino acid concentrations and enzymatic activity in young pigs fed arginine-deficient diets.

Two experiments were conducted with young pigs to determine the efficacy of ornithine (Orn) or citrulline (Cit) as precursors of arginine (Arg). In Exp. 1, pigs were individually fed an Arg-deficient, semipurified diet (.18% Arg) supplemented with .3% Arg or an equimolar quantity of Orn or Cit. Supplemental Arg or Cit increased rate and efficiency of weight gain, but Orn addition was without effect. Free Arg in plasma 3 h post-prandial was increased by addition of either Arg or Cit to the basal diet. Liver Arg was elevated by dietary addition of Arg, Orn or Cit; kidney Arg and Orn were elevated only in pigs receiving supplemental Cit. Arginine or Cit addition to the diet increased Arg concentration in muscle tissue, but muscle Orn was unresponsive to any of the supplements fed. In Exp. 2, pigs were again fed the Arg-deficient, semipurified diet supplemented with .3% Arg or four times an isomolar quantity of ornithine. Arginine addition to the diet increased weight gain and feed efficiency, while Orn supplementation was without effect. Plasma Orn was increased by excess Orn, while plasma Cit was unaffected by supplemental Arg or Orn. Moreover, excess Orn increased free Orn and proline (Pro) in liver, kidney and muscle. Free Cit, however, increased only in liver from feeding excess Orn. In addition, excess Orn decreased both plasma ammonia and free glutamine (Gln) concentration in brain. Arginase activity was roughly 10, 40 and 100 times greater in hepatic tissue than in renal cortex, renal medulla or intestinal mucosa, respectively, while hepatic ornithine transcarbamoylase (OTC) activity was about 15 times greater than the activity present in mucosa tissue. Renal OTC activity was too low to be accurately measured.

Failure of excess dietary lysine to antagonize arginine in young pigs.

Experiments were conducted with young pigs to evaluate the effects of excess lysine when added to diets marginal in arginine. The basal diet was formulated to contain 1.15% lysine and 0.53% arginine. Lysine levels above this were achieved by incremental additions of L-lysine.HCl (experiment 1) or L-lysine acetate (experiment 2). Neither weight gain nor gain-feed ratio was lowered in pigs fed twice the recommended level of lysine (i.e., 2.30%). Lysine levels three or four times the basal level, however, lowered both weight gain and feed intake with no commensurate reduction in feed efficiency. Therefore, lysine appeared to reduce growth via amino acid imbalance rather than antagonism. In pigs equally fed isonitrogenous diets, urea N excretion in the urine was lower in those fed 3.45% supplemental lysine (4.6% total lysine) than in those fed the basal diet. This was offset by a dramatic elevation in urinary excretion of basic amino acids. Urinary excretion of lysine accounted for 26.2% of the lysine consumed by pigs fed 3.45% supplemental lysine. Free lysine levels as well as alpha-aminoadipic acid levels were markedly higher in plasma, liver, kidney and muscle of pigs fed excess lysine than in those fed the basal diet. Tissue levels of arginase and ornithine transcarbamoylase were uninfluenced by the level of lysine ingested.

Amino acid excesses for young pigs: effects of excess methionine, tryptophan, threonine or leucine.

Five experiments involving 359 weanling (8 kg) pigs were conducted to evaluate the effects of dietary excesses of DL-methionine (Met), L-tryptophan (Trp), L-threonine (Thr) or L-leucine (Leu) when added to a 20% crude protein corn-soybean meal (C-SBM) diet. Experiments involved supplementing the basal diet with 0, .5, 1.0, 2.0 or 4.0% excesses of Met, Trp or Thr, or in the case of Leu, a 0, 1.0, 2.0, 4.0 or 6.0% excess. Levels of .5 and 1.0% excess Met did not depress feed intake (FI), weight gain (G) or gain/feed (G/F); 2.0 and 4.0% additions, however, depressed both FI and G but not G/F. Free Met in blood plasma increased linearly as dietary Met level increased, reaching over a 100-fold elevation at the highest Met level fed. Plasma Thr and serine (Ser) increased, and glycine (Gly) decreased, with each added increment of Met. With Trp, only the 4.0% addition depressed FI and G (but not G/F). None of the levels of excess Thr depressed performance. Excess Thr, in fact, tended to increase G/F. Free Thr, Ser and Gly in plasma increased linearly as graded increments of excess Thr were added to the diet. With Leu, a 6% addition depressed weight gain and food intake (but not G/F) but 1, 2 or 4% excesses were without effect. Plasma free Leu increased linearly while free isoleucine and valine decreased as graded increments of Leu were added to the diet. These results suggest that pigs can tolerate considerable excesses of Met, Trp, Thr and Leu without experiencing decreased voluntary feed intake or weight gain.(ABSTRACT TRUNCATED AT 250 WORDS)

Toxic effects of supplemental copper and roxarsone when fed alone or in combination to young pigs.

Three experiments were conducted to investigate the roxarsone (3-nitro-4-hydroxyphenylarsonic acid) X copper (Cu) interaction in weanling pigs. Supplemental roxarsone at 400 mg/kg diet decreased rate and efficiency of weight gain and caused visible neurological signs of toxicosis. Copper addition (CuSO4 X 5H2O) at a level of 650 mg Cu/kg diet likewise decreased weight gain and feed efficiency, and it also increased hepatic Cu deposition. The combination of these growth-depressing dosages of roxarsone and Cu resulted in a far greater reduction in gain and efficiency of feed utilization than was the case when either compound was fed alone. A growth-promoting dosage of Cu (250 mg/kg) increased weight gain by 32% in one experiment but showed no efficacy in alleviating the growth-depression resulting from feeding 400 mg/kg roxarsone. A roxarsone dosage of 100 mg/kg increased gain and feed efficiency. Surprisingly, the decreased weight gain in pigs fed 650 mg/kg Cu was ameliorated by feeding 100 mg/kg roxarsone concomitantly. This level of roxarsone also reduced liver Cu concentration substantially. It thus appears that the nature of the roxarsone X Cu interaction is dependent on the dose of each compound administered. Moreover, low-dose roxarsone administration appears to ameliorate Cu toxicity, but low-dose Cu feeding does not show efficacy against roxarsone toxicity.

Feed additive studies with newly weaned pigs: efficacy of supplemental copper, antibiotics and organic acids.

Six experiments involving 706 newly weaned 28- to 32-d-old pigs were conducted to evaluate the efficacy of copper (Cu) sulfate (to provide 250 mg/kg Cu), antibiotic-sulfa combinations [chlortetracycline, 110 mg/kg + penicillin, 55 mg/kg + sulfamethazine, 110 mg/kg; i.e., Aureo-Sulfa-Penicillin (ASP) or tylosin, 110 mg/kg + sulfamethazine, 110 mg/kg; i.e., Tylosin-Sulfa (TS)] and anhydrous citric or fumaric acid (.75 to 1.5% of the diet). The basal experimental diet was a 19% crude protein (CP)-fortified corn-soybean meal diet (1.08% lysine) containing 7% dried whey and 3% fish meal. Marked and consistent gain and gain/feed responses occurred from the Cu supplement, particularly during the first week postweaning. The antibiotic-sulfa combinations were less efficacious than Cu during the 1-wk postweaning stress period. During either the 1- or 3-wk growth periods, ASP and TS showed additivity with Cu in promoting rate and efficiency of weight gain. Liver Cu was increased by Cu addition to the diet, but neither ASP nor TS affected Cu deposition in the liver. In a factorial experiment involving 17% (1.01% lysine) or 20% CP (1.23% lysine) corn-soybean meal diets containing either no dried whey or an addition of 25% whey, Cu supplementation elicited marked improvements in rate and efficiency of weight gain, particularly in diets without added whey. Likewise, whey addition improved pig performance, especially when added to the diets containing no supplemental Cu.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of dietary electrolyte balance, energy, and amino acid supplementation on the monensin response in chicks fed diets varying in protein content.

The effects of several dietary factors on the anorexigenic response to monensin in chicks fed corn-soybean meal diets varying in crude protein (CP) were investigated. In Trial 1, crossbred chicks (New Hampshire X Columbia) were fed a 16% CP diet with or without 160 mg/kg monensin and/or .53% potassium carbonate in a 2 X 2 factorial design. Monensin supplementation caused a 24.5% growth depression, and potassium carbonate had no effect on the monensin-induced depression. Trials 2 and 3 were designed to evaluate the effects of dietary energy level on the monensin response in commercial broiler chicks fed diets containing 24, 20, or 16% CP. As CP level was decreased, the depression in performance from 121 mg/kg monensin increased. Increasing the energy concentration of the 24 and 20% CP diets to that of the 16% CP diet had no consistent effect on the response of chicks to monensin. Trial 4 was conducted to determine the influence of amino acid (AA) supplementation on the monensin response in broiler chicks fed a low-protein diet. Supplementation of a 16% CP diet with an AA mixture (3% glutamic acid plus essential AA equal to the 24% CP diet) improved growth performance markedly. Deletion of methionine, arginine, and lysine from the AA mixture yielded performance well below that of chicks fed the unsupplemented 16% CP diet, indicating a severe AA imbalance. Monensin supplementation at 121 mg/kg caused a much greater growth depression in chicks fed 16% CP or 16% CP plus the complete AA mixture than in those fed 24% CP or the AA-imbalanced 16% protein diet.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of 3-nitro-4-hydroxyphenylarsonic acid on copper utilization by the pig, rat and chick.

Experiments were conducted to examine the effect of dietary roxarsone (3-nitro-4-hydroxyphenylarsonic acid) on Cu utilization by the pig, chick and rat. A fortified corn-soybean meal diet was fed in each experiment. Roxarsone dramatically reduced liver Cu concentration at all levels of supplemental Cu fed. The level of roxarsone commonly fed, 50 mg/kg diet, resulted in a two- to fourfold depression in liver Cu concentration in all species studied. The effects of roxarsone on weight gain were more perplexing. In the chick, the diets containing 100 and 250 mg Cu/kg depressed growth in the presence, but not in the absence, of 50 mg/kg dietary roxarsone. In contrast, at toxic levels of Cu, roxarsone had no effect on (500 or 750 mg Cu/kg diet) or slightly alleviated (1,000 mg Cu/kg diet) the growth-depressing effects of Cu. In the rat, a roxarsone level of 50 mg/kg diet exacerbated the growth-depressing effect of 1,000 mg Cu/kg diet. However, Cu had no effect on the growth depression that resulted from feeding a toxic level of roxarsone (250 mg/kg diet). The antagonizing effects of roxarsone and Cu on weight gain were not evident in the pig. Supplemental Cu (250 mg/kg diet) improved weight gain, but not feed efficiency, in starter pigs. Roxarsone (50 mg/kg diet) had no effect on the growth-promoting effects of Cu.