Effect of low-protein diets on growth performance and body composition of broiler chicks.

Three experiments were conducted to investigate effects of dietary manipulations to improve growth performance and whole-body composition of broiler chicks fed low-protein diets supplemented with crystalline amino acids. In all experiments, male chicks (1 d old) were fed a common corn-soybean meal diet (23% CP) for 7 d and subsequently allotted to treatment diets in a completely randomized design (10 chicks per floor pen, six replications). Chicks had free access to the isoenergetic diets (3,200 kcal MEn/kg) for 2 wk, after which chicks were weighed and then fasted for 24 h, and the whole-body DM, N, and ether extract contents of two chicks per pen (and six baseline chicks) were determined. In Experiment 1, Gln or Asn replaced 1% triammonium citrate in the low-protein diet (19% CP). In Experiments 2 and 3, dietary concentrations of crystalline essential and nonessential amino acids, respectively, were increased incrementally in the low-protein diets (19 to 20% CP). In all experiments, chicks fed low-protein diets grew slower, used feed less efficiently, and retained less N and more ether extract than chicks fed the control diets (P < or = 0.05), despite additions of crystalline Gln or Asn and despite increased dietary concentrations of crystalline essential and nonessential amino acids. Chicks fed low-protein diets excreted less N (P < 0.001) than did chicks fed the high-protein diets, and N excretion increased linearly (P < 0.001) with N intake. In summary, low-protein diets failed to support equal growth performance to that of high-protein control diets.

Long-term influence of lipid nutrition on the induction of CD8(+) responses to viral or bacterial antigens.

Porcine CD8(+) lymphocytes are critical for the development of cellular immune responses to bacterial (i.e. CD8alphaalpha(+)) and viral (i.e. CD8alphabeta(+) lymphocytes) pathogens. Vaccination and challenge modulate the kinetics of appearance of CD8(+) cells in peripheral blood. In addition to antigen-mediated modulation, nutritional modulation can also influence cell-mediated immunity. We had previously observed that diets supplemented with a mixture of conjugated linoleic acid (CLA) isomers expanded porcine CD8(+) peripheral blood mononuclear cells (PBMC). The present study aimed to investigate the influence of prior consumption of a nutraceutical, (i.e. dietary CLA) on phenotypes and effector functions of porcine PBMC following immunization with a bacterin or a modified-live viral vaccine. It was demonstrated that the effects of dietary CLA on immune cell phenotype (i.e. numbers of CD8alphabeta(+) cells) persisted after the compound was withdrawn from the diet (i.e. 67 days), whereas effector functions (i.e. antigen-stimulated proliferation and cytotoxicity) disappeared earlier (i.e. 25 days). Specifically, numbers of CD8alphabeta(+) PBMC in pigs that had been fed diets supplemented with CLA were greater than in pigs fed control (i.e. isoenergetic and unsupplemented) diets, regardless of the vaccination treatment. Furthermore, prior dietary CLA supplementation interacted with viral immunization (i.e. modified-live pseudorabies virus (PRV) vaccine) by enhancing both pseudorabies-specific proliferative responses of CD8alphabeta(+) PBMC and granzyme activities of PBMC.

Dietary conjugated linoleic acid modulates phenotype and effector functions of porcine CD8(+) lymphocytes.

In vivo vaccination and challenge studies have demonstrated that CD8(+) lymphocytes are essential for the development of cell-mediated protection against intracellular pathogens and neoplastic cells. Depletion of peripheral blood CD8(+) cells interferes with clearance of viruses and intracellular fungi, induction of delayed type hypersensitivity responses and antitumoral activity. In contrast to humans or mice, porcine peripheral CD8(+) lymphocytes are characterized by a heterogeneous expression pattern (i.e., CD8alphabeta and CD8alphaalpha) that facilitates the study of distinctive traits among minor CD8(+) cell subsets. A factorial (2 x 2) arrangement within a split-plot design, with 16 blocks of two littermate pigs as the experimental units for immunization treatment (i.e., unvaccinated or vaccinated with a proteinase-digested Brachyspira hyodysenteriae bacterin) and pig within block as the experimental unit for dietary treatment (soybean oil or conjugated linoleic acid) were used to investigate the phenotypic and functional regulation of CD8(+) cells by dietary conjugated linoleic acid (CLA). Dietary CLA supplementation induced in vivo expansion of porcine CD8(+) cells involving T-cell receptor (TCR)gammadeltaCD8alphaalpha T lymphocytes, CD3(-)CD16(+)CD8alphaalpha (a porcine natural killer cell subset), TCRalphabetaCD8alphabeta T lymphocytes and enhanced specific CD8(+)-mediated effector functions (e.g., granzyme activity). Expansion of peripheral blood TCRalphabetaCD8alphabeta cells was positively correlated (r = 0.89, P < 0.01) with increased percentages of CD8alphabeta(+) thymocytes. Functionally, CLA enhanced the cytotoxic potential of peripheral blood lymphocytes and proliferation of TCRgammadeltaCD8alphaalpha cells. Collectively, these results indicate that dietary CLA enhances cellular immunity by modulating phenotype and effector functions of CD8(+) cells involved in both adaptive and innate immunity.

Effects of dietary conjugated linoleic acid in nursery pigs of dirty and clean environments on growth, empty body composition, and immune competence.

Early-weaned pigs (n = 64) averaging 5.3 +/- 0.3 kg and distributed into two environments (dirty and clean) were used to evaluate effects of conjugated linoleic acid (CLA) on growth performance, immune competence, and empty body composition. A factorial (2 x 4) arrangement within a split-plot design, with four littermate pigs as the experimental unit for the environment, pig within litter as the experimental unit for dietary treatment, and d-0 body weight used as covariate, were used in data analysis. Diets were formulated to contain CLA at 0, 0.67, 1.33, or 2% and to exceed the NRC (1988) nutrient needs of pigs. Animals were given ad libitum access to feed for 7 wk in three phases (I, 1 to 2; II, 3 to 5; and III, 6 to 7 wk). Within phases, diets were isocaloric and isonitrogenous. In Phase I, as dietary CLA concentration increased, ADG and ADFI decreased linearly (P < 0.05 and P < 0.02, respectively). In Phase II, upon adaptation to dietary CLA supplementation, ADG increased quadratically (603, 623, 622, and 548 g/d; P < 0.01), ADFI decreased linearly (873, 840, 867, and 717 g/d; P < 0.02) and gain:feed ratio tended to increase linearly (691, 742, 715, and 763; P < 0.07). In Phase III, no differences in growth performance were attributed to either dietary or environmental treatments. The poor health status associated with the dirty environment induced a growth suppression; pigs in the clean room had a greater cumulative ADG (P < 0.01) and ADFI (P < 0.01) than pigs in the dirty room. In Phase I, lower plasma urea nitrogen levels observed in pigs found in the dirty room (P < 0.03) indicated a lower protein intake caused by a lower ADFI. The effects of dietary CLA on peripheral phenotypic profiles of lymphoytes did not appear until d 42. However, as indicated by the growth suppression of pigs in the dirty room, the negative effects of the environmental challenge on pig health and growth had already appeared during phase I. On d 42, CLA induced a linear increase in percentages of CD8+ lymphocytes (21.7, 22.3, 28.0, and 32.7%; P < 0.001). These data suggest that a 42-d dietary CLA supplementation preceding a disease challenge could have prevented disease-associated growth suppression. Also, CLA-mediated amelioration of particular infectious diseases will depend on which CD8+ T cell subset (i.e., CD8alphaalpha-immunoregulatory or CD8alphabeta-cytotoxic) is most influenced by dietary CLA supplementation.

The effect of dietary active dry yeast supplement on performance of sows during gestation-lactation and their pigs.

Thirty crossbred sows and their pigs were evaluated through two parities to determine any reproductive or growth performance effects of an active dry yeast supplement added to corn-soybean meal diets. Sow reproductive performance from d 93 of gestation through d 21 of lactation and sow milk composition were evaluated. Pig growth performance was measured from birth to 28 d after weaning. Active dry yeast was added at 0, 1, or .2% of the sow gestation diet, 0, .15, or .3% of the sow lactation diet, 0, .2, or .4% of the pig prestarter diet, 1 wk before and 1 wk after weaning, and 0, .125, or .25% during the last 3 wk in the nursery. The yeast source consisted of a concentrate of live yeast cells of the Saccharomyces cerevisiae strain containing more than 15 x 10(9) live cells/g. Sow body weight at d 93 of gestation, at farrowing, and at d 21 of lactation did not differ (P > .10) among treatment groups. Milk from sows fed active dry yeast contained higher amounts of total solids (P < .05), crude protein (P < .10), and gamma globulin (P < .06) than milk from sows fed the control diet. Sow feed intake during lactation was not affected (P > .10) by treatment, nor were there differences in litter size at birth, litter birth weight, or litter weight at d 21 after farrowing. Active dry yeast supplementation to the sow and pig diets resulted in improved postweaning pig daily gain (P < .05) and gain-to-feed ratio (P < .05) but did not affect (P > .10) feed intake. Based on these data, active dry yeast supplement during late gestation, lactation, and before and after weaning does not alter litter weight at birth or weaning but does increase gamma globulin content of sow's milk and improves postweaning rate and efficiency of weight gain of pigs.

Use of plasma urea nitrogen as a rapid response criterion to determine the lysine requirement of pigs.

Five experiments were conducted to evaluate the potential use of plasma urea N (PUN) concentrations as a rapid response criterion to determine amino acid requirements. A preliminary experiment (Exp. 1) indicated that a 3-d feeding time was required to re-equilibrate PUN concentrations after a change in the dietary concentration of lysine. In Exp. 2, 3, and 4, PUN was used to estimate the lysine requirement of growing pigs at different specific BW. Thirty individually penned crossbred pigs weighing 32 and 44 kg in Exp. 2 and 3, respectively, were assigned to five dietary treatments (.60, .70, .80, .90, and 1.00% lysine) for 5 d. The PUN decreased quadratically (P < .05) to increasing dietary lysine. A two-slope, broken-line regression model estimated the requirement at .85% in Exp. 2 and at .76% in Exp. 3. In Exp. 4, 60 crossbred pigs (30 barrows and 30 gilts) weighing 70 kg were assigned to five dietary lysine concentrations: .50, .60, .70, .80, and .90% for 4 d. Increasing lysine caused PUN to decrease quadratically (P < .01). The estimated requirements were different (P < .05) between sexes: .69% for barrows and .75% for gilts. In Exp. 5, the validity of using PUN as a rapid response criterion was verified by comparing the estimated lysine requirement based on PUN with the requirement determined in a 7-d N balance. Twenty crossbred barrows averaging 19 kg were used. Dietary lysine concentrations were .60, .75, .90, 1.05, and 1.20%. A quadratic response was observed in PUN (P < .05) and N retention (NR) (P < .01) with increasing lysine. The estimated lysine concentrations that maximized rates of NR and minimized PUN (1.03 vs. 1.05) were not different (P > .10). Therefore, PUN concentrations can be used in short-term trials to accurately estimate the dietary lysine required to maximize total N utilization in pigs at a specific BW. In addition, the two-slope broken-line regression model had the highest R2 and the lowest mean square error compared with three other models as means for estimating lysine requirement from PUN concentrations.

Effects of excess dietary leucine and leucine catabolites on growth and immune responses in weanling pigs.

Two experiments with weanling pigs were conducted to study the effects on growth and immune responses of excess dietary L-leucine (LEU) and dietary supplementation with the LEU catabolites, alpha-ketoisocaproic acid (KIC) and beta-hydroxymethyl butyrate (HMB). In Exp. 1, 80 pigs were randomly allocated according to initial BW and ancestry to five replications of four dietary treatments (four pigs/pen). The control diet contained wheat, oat groats, menhaden fish meal, and dried whey and provided 1.12% LEU. Treatment diets were the control plus 1.12% LEU, 1.12% KIC, or .4% HMB. The experiment lasted 6 wk. In Exp. 2, 36 pigs were randomly allocated to nine replications of four dietary treatments in a 2 x 2 factorial arrangement. Treatments consisted of two concentrations of dietary LEU and a daily i.m. injection of dexamethasone (DEX) or saline. Pigs were fed a control corn-soybean meal and dried whey diet (1.56% LEU) or the control diet plus 1.56% of crystalline LEU. Pigs were individually penned and the experiment lasted 4 wk. Growth performance, plasma free amino acids, plasma urea nitrogen, and humoral and cellular immune responses were measured. Results indicated that LEU concentrations in practical diets and supplementation with KIC and HMB (Exp. 1) did not detrimentally affect growth and immune response. The high LEU concentration and DEX injection used in Exp. 2, however, were detrimental to both growth and immune response.

Colostral milk fat percentage and pig performance are enhanced by feeding the leucine metabolite beta-hydroxy-beta-methyl butyrate to sows.

Three trials were conducted to test whether feeding the leucine metabolite beta-hydroxy-beta-methyl butyrate (HMB) would increase fat content of sows' milk and pig weight gain. All sows received a basal diet and were assigned at random to receive either 2 g of CaCO3/d (control) or 2 g of Ca(HMB)2/d (HMB), which was top-dressed to the basal diet. Treatment began 3 to 4 d before farrowing. In Trials 1, 2, and 3 there were 4, 19, and 11 pairs of sows, respectively. In a combined analysis that included all three trials, milk fat at d 1 was increased by 41% (P = .01) and pig weight at d 21 was increased by 7% (P = .01) for sows fed diets containing HMB compared with sows fed control diets. Sows fed HMB lost more backfat (P = .03); however, sows receiving HMB had more (P < .05) backfat depth at farrowing than control sows. At weaning there was no difference in backfat depth between the treatment groups. Sows fed HMB tended to consume less feed (P = .07) than control sows. In Trials 2 and 3, data were collected on the subsequent reproductive cycles of the sows. A combined analysis of the data revealed no differences in sow performance when sows previously fed the diet containing HMB were compared with sows previously fed the control diet. In conclusion, beta-hydroxy-beta-methyl butyrate, when fed to sows at 2 g/d, resulted in an increase in fat percentage of sow's milk and pig performance.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of graded levels of lysine and excess arginine and threonine on young pigs fed practical diets.

Three experiments were conducted to estimate the lysine requirement of the weanling pig and the effects of excess arginine and threonine on that estimate. Feeding 1.15% dietary lysine in Exp. 1 and 1.20% in Exp. 2 maximized feed efficiency and resulted in the lowest plasma urea N values. Adding .15% threonine to the diets in Exp. 2 did not affect (P greater than .10) performance of the pigs, but increased (P less than .01) plasma urea N and decreased (P less than .01) plasma lysine concentrations. Supplemental arginine (.22%) did not affect performance of the growing pigs in Exp. 3, but it increased (P less than .01) plasma urea N. Pigs fed a corn-soybean meal diet utilized feed more efficiently (P less than .05) than those fed a corn-fish meal-dried whey diet. The most likely cause for this response was that the corn-soybean diet contained more lysine (.82%) than expected, whereas the corn-fish meal-dried whey diet had close to the expected content of lysine (.72%). From these results, it was concluded that the lysine requirement of the weanling pig fed practical diets is at least 1.15 or 1.20% of the diet. Also, added arginine or threonine did not adversely affect the performance of pigs.