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Biomedical subjects

B J Kerr

Publications and source records attributed to B J Kerr.

At least 37 records · Page 2Linked to original sources
PubMed2003

Isoleucine requirement of growing (25 to 45 kg) pigs.

Three pig bioassays and two digestibility trials were conducted to determine the true digestible Ile requirement for maximal weight gain and minimal plasma urea nitrogen (PUN) of growing (25 to 45 kg) pigs. In Exp. 1, an Ile-deficient basal diet was developed and confirmed to be markedly deficient in Ile, yet fully efficacious when fortified with surfeit Ile. This diet contained corn, red blood cells, and soybean meal as Ile sources, and was analyzed to contain 15.5% crude protein, 0.34% Ile, and 0.95% lysine; metabolizable energy was calculated to be 3,430 kcal/kg. True digestibility of Ile in the basal diet was 89% based on digestibility trials in ileal-cannulated pigs and cecectomized roosters. The first growth trial (Exp. 2) involved six dose levels of true digestible Ile (0.38 to 0.58%), which resulted in a quadratic (P < 0.02) response in weight gain by growing pigs over a 21-d period. The weight-gain data were fitted to both a single-slope broken line and a quadratic fit, and when the quadratic response curve was superimposed on the broken line, the point at which the quadratic curve first intersected the plateau of the broken line occurred at 0.50% true digestible Ile. This (objective) requirement estimate was similar to that determined by taking 90% of the upper asymptote of the quadratic fitted line. In Exp. 3, a replicated 5 x 5 Latin square, five barrows (square 1) and five gilts (square 2) together with five 4-d feeding periods and five levels of true digestible Ile were utilized. A linear (P < 0.01) decrease in PUN occurred as Ile was incremented, with an apparent plateau occurring at 0.50% true digestible Ile. The results of these experiments suggest that the true digestible Ile requirement of grower (25 to 45 kg) pigs is 0.50% of the diet, or 1.46 g/Mcal of metabolizable energy, somewhat higher than the 1.38 g/Mcal metabolizable energy estimated by the 1998 National Research Council Subcommittee on Swine Nutrition.

Animal Feed↗
PubMed2003

Influences of dietary protein level, amino acid supplementation and environmental temperature on performance, body composition, organ weights and total heat production of growing pigs.

The study was conducted to determine the effects of feeding a 16% CP diet, a 12% CP diet, or a 12% CP diet supplemented with crystalline Lys, Trp, and Thr (12% CP + AA diet) in a thermal-neutral (23 degrees C) or heat-stressed (33 degrees C) environment on various body and physiological measurements in growing pigs. Heat-stressed pigs were given a 15% lower daily feed allowance than thermal-neutral pigs to remove the confounding effect of feed intake caused by high temperature. No diet x temperature interaction was observed for any variables (P > 0.09) except for pig activity and pancreas weight. At 33 degrees C, pig activity and pancreas weight did not differ among dietary treatments (P > 0.05). In contrast, at 23 degrees C, pigs fed the 12% CP diet had greater activity than those fed the 16% CP diet or the 12% CP + AA diet (P < 0.05). Pancreas weight was greater for pigs fed the 12% CP + AA diet than those fed the 12% CP diet (P < 0.05) when maintained at 23 degrees C. Compared with 23 degrees C, the 33 degrees C temperature decreased pig activity, heat production, daily gain, feed efficiency, and affected the concentration and accretion of empty body protein and ash, as well as weights of heart, pancreas, stomach, and large intestine (P < 0.05). Pigs fed the 12% CP + AA diet attained similar levels of performance and rates of empty body water, protein, lipid, and ash deposition as pigs fed the 16% CP diet (P > 0.10). Pigs fed the 12% CP + AA diet had lower serum urea plus ammonia nitrogen concentrations (P < 0.01) and total heat production (P < 0.05) compared with those fed the 16% CP diet or the 12% CP diet. These results confirm that, with crystalline AA supplementation, growing pigs fed a 12% CP diet will perform similar to pigs fed a 16% CP diet. The data further indicate that lowering dietary CP and supplementing crystalline AA will decrease total heat production in growing pigs whether they are housed in a thermal-neutral or heat-stressed environment.

Amino Acids↗
PubMed2002

The tryptophan requirement of nursery pigs.

Five experiments were conducted to determine the true digestible Trp (dTrp) requirement of nursery pigs. Treatments were replicated with four or five pens of five or six pigs each. Pigs were weaned at 21 (Exp. 1, 2, and 5) or 19 d (Exp. 3 and 4), and fed common diets for various times and then experimental diets for 8 (Exp. 1), 13 (Exp. 2 and 3), or 14 d (Exp. 4 and 5). Experiment 1 (160 pigs, initial and final BW of 8.4 and 11.4 kg) evaluated six protein sources low in Trp relative to a positive control diet to identify the protein source to be used in subsequent experiments. The results indicated that a diet with Canadian field peas (CFP) supplemented with Trp resulted in ADG, ADFI, and gain:feed (GF) equal to (P > 0.10) the positive control diet. In Exp. 2, 75 pigs (initial and final BW of 13.2 and 19.2 kg) were fed 1) Trp-deficient diet (0.13% dTrp) with CFP, 2) Diet 1 with added Trp (0.23% dTrp), or 3) positive control diet (0.22% dTrp). Daily gain, ADFI, and GF were decreased (P < 0.01) in pigs fed Diet 1 compared with pigs fed Diets 2 and 3, but ADG, ADFI, and GF were equal (P > 0.10) in pigs fed Diets 2 and 3. Experiments 3 (180 pigs, initial and final BW of 5.2 and 7.3 kg), 4 (120 pigs, initial and final BW of 6.3 and 10.2 kg), and 5 (144 pigs, initial and final BW of 10.3 and 15.7 kg) were conducted to estimate the dTrp requirement of nursery pigs with diets using CFP as a primary protein source. The diets used in Exp. 3, 4, and 5 contained 1.35, 1.19, or 1.01% dLys, respectively, and other amino acids were provided at 105% the ratio relative to Lys. Response variables were ADG, ADFI, GF, and plasma urea N concentrations, and data were analyzed using the broken-line model. The levels of dTrp in the diets for Exp. 3 (Phase I, 5.2 to 7.3 kg) were 0.14, 0.17, 0.20, 0.23, 0.26, and 0.29%. The average dTrp requirement was estimated to be 0.21% (0.24% total Trp). The levels of dTrp in the diets for Exp. 4 (Phase II, 6.3 to 10.2 kg) were 0.13, 0.16, 0.19, 0.22, 0.25, and 0.28%. The average dTrp requirement was estimated to be 0.20% (0.23% total Trp). The levels of dTrp in the diets for Exp. 5 (Phase III, 10.3 to 15.7 kg) were 0.130, 0.155, 0.180, 0.205, 0.230, and 0.255%. The average dTrp requirement was estimated to be 0.18% (0.22% total Trp). These results indicate that the true dTrp requirement is 0.21, 0.20, and 0.18% for Phase I (5.2 to 7.3 kg), II (6.3 to 10.2 kg), and III (10.3 to 15.7 kg) nursery pigs, respectively.

Amino Acids↗
PubMed2001

Endogenous galanin is required for the full expression of central sensitization following peripheral nerve injury.

The neuropeptide galanin is known to be involved in nociceptive sensory processing in the spinal cord. We have attempted to better characterise the function of endogenous galanin in nociceptive signalling by examining a mouse strain carrying a loss of function mutation in the galanin gene (gal-/-). Galanin expression is significantly up-regulated following damage to a peripheral nerve. To address what effect this up-regulation has on spinal cord excitability we have examined wild type (gal+/+) and gal-/- mice 3 days after complete transection of the sciatic nerve using an electrophysiological paradigm, the flexor withdrawal reflex. We demonstrate that the up-regulation of galanin has no direct effect on basal spinal excitability after nerve injury. However, galanin is shown to be a crucial neuromodulator involved in the development of the central sensitization as both windup and the facilitation of spinal reflexes following conditioning stimulation are significantly impaired in gal-/- mice following peripheral nerve injury.

Action Potentials↗
PubMed2001

A role for the TTX-resistant sodium channel Nav 1.8 in NGF-induced hyperalgesia, but not neuropathic pain.

The tetrodotoxin-resistant voltage-gated sodium channel Nav 1.8 is expressed only in nociceptive sensory neurons. This channel has been proposed to contribute significantly to the sensitization of primary sensory neurons after injury. We have studied the nociceptive behaviours of mice carrying a null mutation in the Nav 1.8 gene (Nav 1.8 -/-) in models of peripheral inflammation as well as a model of neuropathic pain. The results from the present studies reveal that Nav 1.8 is a necessary mediator of NGF-induced thermal hyperalgesia but is not essential for PGE2-evoked hypersensitivity. Neuropathic pain behaviours were unchanged in Nav 1.8 -/- mice indicating that this channel is not involved in the alteration of sensory thresholds following peripheral nerve injury.

Animals↗
PubMed2001

Valine requirement of nursery pigs.

Six experiments were conducted to determine the true digestible valine requirement of 5- to 20-kg pigs. In Exp. 1, a valine-deficient diet for 5- to 10-kg pigs was developed and validated in terms of growth performance in response to supplemental L-valine. A different basal diet was validated for 10- to 20-kg pigs in Exp. 2. Both diets were demonstrated to be deficient in valine and to support performance equivalent to typical nursery diets when fortified with L-valine. In Exp. 3, true ileal digestibility of valine in the two basal diets was determined in eight pigs fitted with a simple T-cannula at the terminal ileum. Another four pigs received an enzymatically hydrolyzed casein-based diet to determine endogenous contributions to collected ileal digesta. The two diets were found to have true valine digestibilities of 82% (5- to 10-kg pigs) and 86% (10- to 20-kg pigs). In Exp. 4, 80 weaned pigs (5.8 kg) were offered the basal diet fortified with five incremental doses (0.08%) of L-valine. Weight gain increased quadratically (P < 0.05) with increasing levels of valine. Broken-line analysis revealed a true digestible valine requirement of 0.86 +/- 0.03%. In Exp. 5, the true digestible valine requirement of 10- to 20-kg pigs was estimated with 120 pigs (10.9 kg) using the second basal diet fortified with six incremental doses (0.05%) of L-valine. The data suggested a digestible valine requirement level of about 0.775%, which was reevaluated in Exp. 6, wherein pigs did not respond to levels of digestible valine higher than 0.775%. In conclusion, requirement estimates were 2.50 and 2.22 g of true digestible valine per megacalorie of ME for 5- to 10- and 10- to 20-kg pigs, respectively. These empirical estimates are in close agreement with recent estimates of the National Research Council Subcommittee on Swine Nutrition of 2.48 and 2.11 g of true digestible valine per megacalorie of ME, respectively.

Animal Nutritional Physiological Phenomena↗
PubMed2000

Galanin knockout mice reveal nociceptive deficits following peripheral nerve injury.

The neuropeptide galanin has been identified as a potential neurotransmitter/neuromodulator within the central nervous system. In the present study, the role of endogenous galanin in nociceptive processing in the nervous system has been analysed by using mice carrying a targeted mutation in the galanin gene. Supporting this, the effect of chronic administration of exogenous galanin on nociceptive sensory inputs has been assayed in adult rats. In the absence of peripheral nerve injury, the sensitivity to threshold noxious stimuli is significantly higher in galanin mutant mice than wild-type controls. Following peripheral nerve injury, in conditions under which endogenous galanin levels are elevated, spontaneous and evoked neuropathic pain behaviours are compromised in mutant mice. Conversely, chronic intrathecal delivery of exogenous galanin to nerve-intact adult rats is associated with persistent behavioural hypersensitivity, a significant increase in c-fos expression and an increase in PKCgamma immunoreactivity within the spinal cord dorsal horn. The present results demonstrate that a relationship exists between the degree of nerve injury-induced galanin expression and the degree of behavioural hypersensitivity, and show that galanin may play a role in nociceptive processing in the spinal cord, with interrelated inhibitory and excitatory effects.

Animals↗
PubMed1999

Brain-derived neurotrophic factor is an endogenous modulator of nociceptive responses in the spinal cord.

The primary sensory neurons that respond to noxious stimulation and project to the spinal cord are known to fall into two distinct groups: one sensitive to nerve growth factor and the other sensitive to glial cell-line-derived neurotrophic factor. There is currently considerable interest in the ways in which these factors may regulate nociceptor properties. Recently, however, it has emerged that another trophic factor-brain-derived neurotrophic factor (BDNF)-may play an important neuromodulatory role in the dorsal horn of the spinal cord. BDNF meets many of the criteria necessary to establish it as a neurotransmitter/neuromodulator in small-diameter nociceptive neurons. It is synthesized by these neurons and packaged in dense core vesicles in nociceptor terminals in the superficial dorsal horn. It is markedly up-regulated in inflammatory conditions in a nerve growth factor-dependent fashion. Postsynaptic cells in this region express receptors for BDNF. Spinal neurons show increased excitability to nociceptive inputs after treatment with exogenous BDNF. There are both electrophysiological and behavioral data showing that antagonism of BDNF at least partially prevents some aspects of central sensitization. Together, these findings suggest that BDNF may be released from primary sensory nociceptors with activity, particularly in some persistent pain states, and may then increase the excitability of rostrally projecting second-order systems. BDNF released from nociceptive terminals may thus contribute to the sensory abnormalities associated with some pathophysiological states, notably inflammatory conditions.

Animals↗
PubMed1999

Brain-derived neurotrophic factor modulates nociceptive sensory inputs and NMDA-evoked responses in the rat spinal cord.

Central sensitization, the hyperexcitability of spinal processing that often accompanies peripheral injury, is a major component of many persistent pain states. Here we report that the neurotrophin, brain-derived neurotrophic factor (BDNF), is a modulator of excitability within the spinal cord and contributes to the mechanism of central sensitization. BDNF, localized in primary sensory neuron cell bodies and central terminals, potentiates nociceptive spinal reflex responses in an in vitro spinal cord preparation and induces c-fos expression in dorsal horn neurons. NMDA receptor-mediated responses, known as a major contributor to central sensitization, were significantly enhanced by exogenous BDNF. Systemic NGF treatment, a procedure that mimics peripheral inflammatory states, raises BDNF levels in sensory neurons and increases nociceptive spinal reflex excitability. This increased central excitability is reduced by trkB-IgG, a BDNF "antagonist." We also show directly that inflammatory pain-related behavior depends on BDNF release in vivo. Thus behavioral nociceptive responses induced by intraplantar formalin and by intraplantar carageenan are significantly attenuated by trkB-IgG. Hence BDNF is appropriately localized and regulated in inflammatory states and is sufficient and necessary for the expression of central sensitization in the spinal cord. We propose that BDNF may function as a modulator of central sensitization in pathological states, and our results suggest that pharmacological antagonism of BDNF may prove an effective and novel analgesic strategy for the treatment of persistent inflammatory pain states.

Animals↗
PubMed1999

The tetrodotoxin-resistant sodium channel SNS has a specialized function in pain pathways.

Many damage-sensing neurons express tetrodotoxin (TTX)-resistant voltage-gated sodium channels. Here we examined the role of the sensory-neuron-specific (SNS) TTX-resistant sodium channel alpha subunit in nociception and pain by constructing sns-null mutant mice. These mice expressed only TTX-sensitive sodium currents on step depolarizations from normal resting potentials, showing that all slow TTX-resistant currents are encoded by the sns gene. Null mutants were viable, fertile and apparently normal, although lowered thresholds of electrical activation of C-fibers and increased current densities of TTX-sensitive channels demonstrated compensatory upregulation of TTX-sensitive currents in sensory neurons. Behavioral studies demonstrated a pronounced analgesia to noxious mechanical stimuli, small deficits in noxious thermoreception and delayed development of inflammatory hyperalgesia. These data show that SNS is involved in pain pathways and suggest that blockade of SNS expression or function may produce analgesia without side effects.

Afferent Pathways↗
PubMed1998

Dietary arginine and lysine ratios in Large White toms. 2. Lack of interaction between arginine:lysine ratios and electrolyte balance.

The effect of dietary Arg:Lys ratios and dietary electrolyte balance (DEB) on growth and carcass parameters of Large White toms was evaluated in one experiment from 8 to 20 wk of age. Growth, feed conversion, and carcass composition were measured. All toms received a common basal diet from 0 to 8 wk of age. At 8 wk of age, 600 toms were randomly placed into 40 pens (15 toms per pen). The corn-soybean meal-based experimental diets were fed from 8 to 12, 12 to 16, and 16 to 20 wk of age and evaluated two Arg:Lys ratios (0.98 vs 1.22) and two DEB levels (148 vs 202 mEq/kg of diet) in a complete factorial arrangement. All experimental diets were pelleted. Composite samples of protein-contributing ingredients and complete experimental diets were analyzed for all amino acids, CP, DM, Cl, Na, and K. High and low average house temperature for the 8 to 20 wk period were 19 and 15 C, respectively. No interactions occurred between Arg:Lys ratios and DEB for any parameter measured except litter moisture. Increasing the Arg:Lys ratio improved 20-wk BW (P < or = 0.027) and 8 to 20 wk gain (P < or = 0.023). Feed:gain from 0 to 20 wk of age was decreased by increasing the Arg:Lys ratio (3.01 vs 2.94; P < or = 0.026) and by increasing the DEB (3.01 vs 2.95; P < or = 0.045). Dietary treatments did not affect mortality. Increasing DEB decreased cold carcass yield (P < or = 0.020). Total breast meat yield was increased (P < or = 0.076) by 1% in toms fed the diets containing the 1.22 Arg:Lys ratio vs toms fed diets containing the 0.98 Arg:Lys ratio. Toms responded favorably to increasing the Arg:Lys ratio for growth, feed conversion, and breast meat yield independent of DEB level.

Animal Feed↗
PubMed1998

Dietary arginine and lysine in Large White toms. 1. Increasing arginine:lysine ratios does not improve performance when lysine levels are adequate.

A study was conducted utilizing two strains of male Large White turkeys (BUT Big 6 and Nicholas 700) to determine the effects of increasing Arg:Lys ratios on live performance and carcass composition. Diets were formulated to provide 100, 110, and 120% of NRC (1994) Lys levels, adjusted for dietary energy level, with Arg:Lys ratios of 1.0:1, 1.1:1, 1.2:1, and 1.3:1 in a 3 x 4 factorial arrangement. Eight pens of 15 poults (four pens of each strain) were fed each of the 12 test diets for an 18-wk period. Diets were changed at 3-wk intervals rather than the 4-wk interval suggested by NRC. The results of this study suggest that the Arg and Lys levels suggested by the NRC (1994) are not sufficient when diets are fed on 3-wk intervals, rather than the 4-wk intervals suggested by NRC. This conclusion is in agreement with the studies of Waldroup et al. (1997b). Increasing Arg:Lys ratios improved performance of turkeys only when the diets contained insufficient amounts of Arg in association with low levels of Lys. Increasing Arg:Lys ratios when diets contained sufficient amounts of these two amino acids was without benefit, in contrast to the report of Brake et al. (1994). Turkeys of the BUT Big 6 strain appeared to be more sensitive to marginal deficiencies of Lys and Arg than did turkeys of Nicholas 700 strain.

Animals↗
PubMed1998

Effect of dietary fiber or fat in low-crude protein, crystalline amino acid-supplemented diets for finishing pigs.

Three experiments were conducted to determine the effect of reducing NE, by adding dietary fiber in Exp. 1 and 2 and decreasing dietary fat in Exp. 3, of low-CP, crystalline amino acid (CAA)-supplemented diets for finishing pigs on growth performance and carcass characteristics. In Exp. 1 and 2, 64 barrows (Exp. 1) or gilts (Exp. 2) were allotted to four treatments with four replicates of four pigs each. Average initial and final BW were 74 and 117 kg in Exp. 1 and 74 and 102 kg in Exp. 2. The following diets were fed in Exp. 1: 1) corn-soybean meal (C-SBM); 2) low-CP (-3.5%), supplemented with CAA; 3) CAA + rice hulls (CAA+RH; NE equal to Diet 1); and 4) CAA+RH+OIL (NE equal to Diet 2). Experiment 2 was similar to Exp. 1, except RH were replaced with wheat middlings (WM), oil was replaced with dry fat, and the CP was decreased by 3.1% in the low-CP diets. In both experiments, serum urea-N (SUN, corrected for initial SUN by covariance analysis) was higher (P<.10) for pigs fed C-SBM than for pigs fed any other diet. In Exp. 1, barrows fed CAA+RH had lower hot carcass weight, percentage muscle, fat-free lean (FFLEAN), lean gain per day, retained energy (RE) in FFLEAN, and lean:fat ratio than barrows fed C-SBM, along with less FFLEAN than barrows fed CAA+RH+OIL. Barrows fed CAA+RH had smaller longissimus muscle areas than barrows fed any other diet, and barrows fed C-SBM had higher dressing percentage and lower percentage total fat than barrows fed any other diet. Barrows fed C-SBM had higher lean:fat ratio and lower total fat than barrows fed CAA. In Exp. 2, gilts fed CAA+WM+FAT had heavier heart weights than gilts fed C-SBM or CAA (P<.10). In Exp. 3, 702 gilts were allotted to six treatments with nine replicates of 13 gilts each. Average initial and final BW were 70 and 110 kg. Gilts were fed two levels of CP (15.5 or 11.7% plus CAA added to meet an ideal amino acid ratio) and three levels of NE (2,650, 2,617, or 2,584 kcal/kg), resulting in a 2x3 factorial arrangement of treatments. Gilts fed 15.5% CP had higher gain:feed ratio than gilts fed 11.7% CP (P<.01). Longissimus depth was greater for gilts fed 15.5% CP than for gilts fed 11.7% CP and was decreased as NE decreased only in gilts fed 11.7% CP (CP effect, P<.09; NE linear effect, P<.04; CP x NE effect, P<.01). Gilts fed the diet with 2,617 kcal NE had lighter carcasses and less total fat, fat gain per day, RE, and RE as fat regardless of protein level than gilts fed 2,650 or 2,584 kcal NE/kg (NE quadratic, P<.09). Loin color score increased as NE decreased (linear, P<.06), but longissimus fat depth was increased by the lowest level of NE (NE quadratic effect, P<.09). Overall, the reduction of NE in low-CP, CAA-supplemented diets did not affect growth performance and was not an effective means of reducing fat in finishing pigs.

Amino Acids↗
PubMed1997

Performance and carcass composition of large white toms as affected by dietary crude protein and threonine supplements.

This experiment evaluates the effect of decreasing dietary CP, in addition to the effects of dietary supplements of L-Thr to low CP diets, in Large White Nicholas toms from 0 to 18 wk of age. Toms were fed dietary treatments consisting of four levels of dietary CP as a percentage of NRC (1994) recommendations (100, 92, 84, and 76% of NRC recommendations). Additional treatments consisted of supplements of L-Thr (0.1 and 0.2% of diet) added to the 92 and 84% NRC CP treatments. All eight dietary treatments were formulated to meet a minimum of 105% of NRC (1994) recommendations for Met, TSAA, Lys, Thr, and Trp. Body weight, feed conversion, mortality, and carcass composition responses were measured. Decreasing CP to 84% of NRC resulted in 18-wk BW lower than that (P < or = 0.001) of toms fed diets containing 100 or 92% of NRC CP; however, toms fed 84% of NRC CP diet supplemented with 0.1% L-Thr had 18-wk BW equal to (P < or = 0.001) that of the 100 and 92% NRC CP treatments. Toms fed diets containing 76% of NRC CP had depressed BW and feed:gain in comparison to all other treatments. No adverse effects in cumulative feed:gain (0 to 18 wk) were noted by decreasing CP from 100 to 84% of the NRC recommendations. Mortality did not differ among treatments. Treatments had no effect on carcass fat expressed as a percentage of hot carcass weight. Breast meat yield (deboned Pectoralis major and Pectoralis minor) was highest (P < or = 0.001) in toms fed the 100 and 92% NRC CP treatments. The 84 and 76% NRC CP treatments resulted in decreased breast meat yield regardless of L-Thr supplements. These results indicate that diets containing Met, TSAA, Lys, Thr, and Trp at a minimum of 105% NRC recommendations may support favorable breast meat yield when CP is decreased to 92% of the NRC (1994) recommendation. If growth and feed conversion are the desirable traits, rather than breast meat yield, CP levels below 92% of the NRC (1994) recommendation may support favorable responses.

Animals↗
PubMed1997

Dietary interactions between lysine and threonine in broilers.

Two experiments were conducted to evaluate the effects of two dietary levels of lysine and four dietary levels of threonine in a factorial arrangement on broiler growth, carcass traits, and immunity. In both experiments, 120 broilers were allocated to each of 56 floor pens (6,720 total broilers). In Experiment 1, two levels of lysine (1.10 and 1.20% of diet) and four levels of threonine (0.68, 0.74, 0.80, and 0.86% of diet) were fed to broilers from 1 to 18 d of age in a sorghum-peanut meal diet. Body weight gain, feed:gain, mortality, and cellular and humoral immunity were measured. In Experiment 2, all broilers received a common basal diet up to 18 d of age. Experimental diets were fed from 18 to 34, 34 to 44, and 44 to 54 d of age. Two levels of lysine [100 and 105% of NRC (1994) recommendations] and four levels of threonine [83, 92, 100, and 108% of NRC (1994) recommendations] were included in the experimental diets for each age group (seven replications per treatment). The diets consisted of wheat (soft), corn gluten meal, soybean meal, and meat and bone meal Weight gain, feed:gain, mortality, and carcass traits were measured at 54 d of age. In Experiment 1, increasing dietary lysine from 1.10 to 1.20% from 1 to 18 d in broilers improved (P < 0.001) BW gain (453 vs 488 g) and feed:gain (1.39 vs 1.33). No interactions between lysine and threonine were observed in Experiment 1. Differences in immune parameters or mortality were not observed. In Experiment 2, an interaction in 18 to 54 d weight gain occurred with the highest gain in broilers receiving dietary lysine and threonine levels equivalent to 100 and 83%, respectively, of NRC (1994) or lysine and threonine at levels of 105% and 100% of NRC (1994), respectively (P < or = 0.05). Supplemental lysine (105% of the 1994 NRC) improved (P < or = 0.01) 18 to 54 d feed:gain (2.30 vs 2.26). No differences in mortality occurred. Supplemental lysine increased preslaughter weight (P < or = 0.05), but differences in carcass yield were not observed. Breast fillet yields were the highest (P < or = 0.03) in broilers receiving 100% of NRC lysine and 83 or 92% of NRC threonine or 105% of NRC lysine and 100 or 108% of NRC threonine. In conclusion, additional lysine improved feed:gain independent of threonine from 1 to 54 d of age. However, lysine and threonine interact to increase weight gain and breast fillet yields.

Aging↗
PubMed1997

The effect of reducing excess dietary amino acids on growing-finishing pig performance: an elevation of the ideal protein concept.

Seventy-two gilts were used to determine the effect of reducing excess amino acid intake on growing-finishing pig performance. Separate diets were formulated for the growing (20 to 55 kg BW) and finishing (55 to 100 kg BW) periods. For each period, three diets were formulated that varied in total crude protein level and contained similar levels of digestible ideal protein. Crystalline amino acids were added to the low protein diets to overcome potential deficiencies. The grower diets contained .66% apparent ileal digestible lysine and contained 16.6, 15.0, and 13.0% CP, respectively; for the finisher diets, these values were .55% digestible lysine and 14.2, 12.8, and 11.0% CP, respectively. Amino acid analyses and a separate digestibility trial were conducted to confirm digestible amino acid levels in the dietary ingredients. During the growing and the overall growing-finishing period, daily gain, feed intake, and gain:feed were not affected (P > .10) by dietary treatment. Daily gain tended to be lower (P = .06) and gain:feed was poorer (P < .05) for pigs fed the 11.0% CP diet during the finishing phase. Although backfat thickness tended to be greater (P = .07) for pigs fed the lower-CP diet, estimated carcass lean yield was not affected (P > .10) by dietary treatment. Results of this study show that dietary CP can be reduced to 13% in the growing and 12.8% in the finishing diets of pigs as long as crystalline amino acids are added to match the apparent ileal digestible amino acid ratios in an assumed ideal protein.

Amino Acids↗
PubMed1997

Body composition and protein and fat accretion in various body components in growing gilts fed diets with different protein levels but estimated to contain similar levels of ideal protein.

A comparative slaughter technique was used to determine the effect of dietary protein levels on body composition and protein and fat accretion in various body components in Yorkshire gilts. Diets were formulated to contain similar levels of idea protein. Eight gilts were slaughtered at 20 kg BW to determine initial body composition. Twenty-four gilts were assigned to each of three dietary treatments (16.6, 15.0 and 13.0% CP) during the growing period (20 to 55 kg BW). During the finishing period (55 to 100 kg BW), dietary CP levels were reduced by approximately two percentage units. Eight gilts per treatment were slaughtered at 55 kg BW, and the remaining pigs were slaughtered at 100 kg BW. At slaughter, the pits were divided into three components: carcass, empty gastrointestinal tract, and other non-carcass parts. Half of the carcass was further dissected into retail cuts. None of the carcass retail cuts was affected (P > .10) by the dietary CP levels, except trimmed ham was smaller (P < .05) in gilts fed the 13% CP growing and 11% CP finishing diets. Far content in the empty body (P = .12) and in the carcass (P = .06) was highest and the empty body water accretion rate was lowest (P = .05) in gilts fed the 13% CP growing and 11% CP finishing diets. Other aspects of chemical body composition, protein and fat accretion rates, and estimated lean yields were not affected by dietary CP level (P > .10).

Animals↗