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The study was conducted to determine the optimum dietary concentration of arginine relative to lysine on the basis of the performance, carcass traits and blood characteristics of 1–35-day-old broilers using a randomised complete block design. One-day-old broilers (n = 1200) were allocated to five dietary treatment groups receiving different arginine:lysine (Arg:Lys) ratios, where the proportion of Arg was progressively increased by increments of 10%, and the concentration of lysine was kept constant; the final ratios were 0.85, 0.95, 1.05, 1.16 and 1.26. Each diet treatment was composed of eight replicates (4 males and 4 females), with 30 chickens each replicate. All broilers were fed in three phases, namely starter, grower and finisher, at 1–10, 11–24 and 25–35 days of age respectively. An increase in the Arg:Lys ratio in the diet from 0.85 to 1.26 linearly (P < 0.001) increased bodyweight gain by 7% and improved feed conversion ratio by 6%. Feed intake and mortality were not significantly (P > 0.05) different among the treatments. Increasing the Arg:Lys ratio in the diet linearly (P < 0.0001) and quadratically (P < 0.05) improved the carcass yield and relative chilled carcass weight respectively. The percentages of breast meat and creatinine and insulin-like growth factor-1 concentrations also linearly (P < 0.0001) increased by 5.5%, 23.0% and 18.0% respectively, with an increasing dietary Arg:Lys ratio. The results of the present study indicated that the highest dietary Arg:Lys ratio (1.26) improved bodyweight gain, feed conversion ratio, breast meat, creatinine and insulin-like growth factor-1. However, the optimum dietary Arg:Lys ratio to improve carcass yield and weight gain in the grower phase (Days 11–24 of age) was at 1.05.

The effect of Arg:Lys, Met source, and time of exposure to heat stress on growth and body protein accretion was tested in acutely heat-stressed (AHS) or chronically heat-stressed (CHS) broilers. Ross 308 1-day-old chickens were raised under normal brooding conditions from 1 to 25 d of age and were then suddenly moved to 32 degrees C (AHS), whereas another group was kept at constant high temperatures throughout the grow-out period (32 degrees C; CHS). From 26 to 33 d of age, both groups were therefore at 32.8 +/- 1.0 degree C. Two rooms were used per environmental treatment. A basal diet deficient in TSAA was supplemented with L-Arg monohydrochloride to achieve Arg:Lys ratios of 0.95 and 1.40. Diets were supplemented with either L-Met, 2-hydroxy-4-(methylthio) butanoic acid (HMB), or DL-Met (DLM) to a level of TSAA 5% lower than requirements. Each Arg:Lys and Met source combination was diluted with a N-free diet to achieve graded levels of CP (0.0, 3.5, 7.0, 10.5, 14.0, and 17.5% CP) and fed to 18 replicates of 3 chickens (3 replicates per level). Treatment effects were obtained by the slope-ratio technique using average daily BW gain and body CP deposition as dependent variables and protein intake as the independent variable. Protein utilization remained unaffected by Met source when fed at high Arg:Lys for birds under AHS and CHS (P0.05). However, lower protein utilization was observed in birds fed L-Met in low Arg:Lys compared with those fed DLM (P0.05). Birds fed HMB at low Arg:Lys utilized dietary protein better than those fed L-Met only under CHS conditions (P0.05). Protein utilization for birds fed HMB was similar to that of birds fed DLM in all instances. It was concluded that Arg:Lys, Met source, and time of exposure to heat stress affected protein utilization in hyperthermic birds.

In two experiments, the effects of arginine:lysine, NaHCO3 and methionine source on performance and amino acid digestion of heat-stressed broilers were studied. In exp. 1, corn/soy diets with argine:lysine (Arg:Lys) of 1.10, 1.25 and 1.40 were fed from 21 to 42 d. Diets were supplemented with 2-hydroxy-4-(methylthio)-butanoic acid (HMB) or DL-Methionine (DLM) with NaHCO3 at 0 or 1.04%. Ten replicates per treatment of four birds per cage were maintained at 31.7 ± 0.9°C. From 21 to 28 d weight gain (BWG), feed consumption and feed-to-gain (FCR) were unaffected by diet treatment. Methionine source did not influence bird performance (P > 0.05). However, from 35 to 42 d, when diets were supplemented with NaHCO3, BWG and FCR of birds fed DLM were compromised when offered diets with Arg:Lys at 1.40. In diets devoid of NaHCO3, increasing Arg:Lys to 1.25 impaired BWG and FCR for broilers fed DLM, although effects disappeared when more Arg was used. Performance of birds on HMB was mostly unaffected by Arg:Lys or NaHCO3 except when fed diets void of NaHCO3 with Arg:Lys of 1.40, when FCR was impaired. In exp. 2, broilers were maintained at thermoneutrality (TN) reaching 20°C at 33 d. Other birds were at 31°C throughout, representing chronic heat stress (CHS), while a third group changed suddenly from 20 to 31°C at 25 d representing acute heat stress (AHS). Birds within each environment were housed in one of two rooms with eight replicates of four birds per treatment. At 25 d, birds were fed Arg:Lys of 0.95 or 1.40 with DLM supplemented at requirement. Birds fed Arg:Lys of 1.40 were also offered diets with synthetic L-methionine (L-Met). Adding L-Met to high Arg diets during CHS significantly depressed ileal digestibility of all amino acids (P < 0.05). It is concluded that chronic heat stress can affect the digestibility of amino acids, and that this effect may impact performance. Key words: Broilers, methionine, arginine, heat stress, digestibility, sodium bicarbonate

The nutritional antagonism of arginine (Arg) and lysine (Lys) was first identified and investigated in the 1950′s and 1960′s. The results of this early research suggest the optimum Arg:Lys ratio to...

There has been much controversy concerning the relative efficacies of equimolar quantities of DL-methionine (DLM) and 2-hydroxy-4-(methylthio) butanoic acid (HMB). Inspection of published literature suggests that the dietary Arginine:Lysine (Arg:Lys) ratio could be involved, especially during heat stress. In Experiment 1, conducted at 32°C, increasing supplemental HMB from 0.16 to .32% in a diet with an Arg:Lys ratio of 1.36 produced a significant increase in body weight gain (BWG) from 21 to 38 days. However, increasing DLM in an equimolar manner did not. Feed intake (FI) was better for the HMB birds. In Experiment 2, where diets with an Arg:Lys ratio of 1.03, 1.20, or 1.34 were fed at 32°C, birds fed HMB gave significantly improved BWG and FCR at a higher FI between 42 and 48 days compared to birds fed DLM. The FI of birds fed DLM decreased more rapidly than the FI birds fed HMB as dietary Arg:Lys ration increased. Therefore, a knowledge of Arg:Lys ratio appears to be required to optimize the methionine activity source.

The objective of this study was to evaluate the influence of methionine sources (DL-methionine 99% powder (DLM) or methionine hydroxy analog liquid 88% (HMTBA)), arginine:lysine (Arg:Lys) ratio and sodium chloride (NaCl) content in the diet of broilers on their performance, carcass yield, serum biochemistry, duodenal mucosal morphology, and immune response. Birds were kept under high temperature conditions during the grower phase and were inoculated or not with an antigen. The use of HMTBA promoted better live performance and carcass yield than the use of DLM. Diets with 1.05 Arg:Lys ratio resulted in better live performance, higher carcass and breast meat yields, longer villi, shallower crypts, and stronger immune response when broilers were challenged than the 1.40 ratio. The dietary supplementation of 6.0 g NaCl/kg promoted better growth performance and carcass weight than 2.0 g NaCl/kg. There was no influence of the different methionine sources or NaCl concentrations on any evaluated intestinal morphology parameter or immune response, nor of any interactions between these sources of variation.

Synopsis Pullets were fed on diets containing various concentrations of lysine and arginine from 7 to 18 or 20 weeks. Thereafter a conventional layers' diet was fed and egg productivity measured—in the first two experiments for ten, and the third for six 28‐d periods. Pullets were also fed on a standard growers' type diet on a “skip‐a‐day” or on a 20% restriction basis in the third study. Growth and age at sexual maturation were directly related to the lysine content of the diet and to a lesser extent to the arginine content. Pullets fed on diets with the lower concentrations of lysine and arginine required less food during the growing period and matured later than those fed on a complete diet ad libitum. They also laid more eggs and required less food to produce a dozen eggs. Higher egg production was obtained in the third experiment with low concentrations of lysine and arginine than with the “skip‐a‐day” or the restricted feeding programmes. Pullets fed on the normal grower diet ad libitum produced the...

Crossbred growing-finishing pigs (112 barrows, 48 gilts) were used to determine the effect of reducing excess dietary arginine, through feedstuff variation, on performance, carcass composition and plasma amino acid concentrations. Diets contained five, four, three or two times the NRC requirement for arginine. Lysine in all diets was formulated to be equal to NRC requirements, and all diets contained at least 100% of the NRC recommendations for all other essential amino acids. Initial weight, final weight and days on test for the grower phase were 26.7 kg, 44.2 kg and 28 d, respectively. Weight gain and gain/feed were not different among treatments but feed intake showed a quadratic response during the grower phase, being highest at four times the NRC requirement for arginine. Initial weight, final weight and days on test for the finisher phase were 44.2 kg, 96.9 kg and 67 d, respectively. Weight gain during the finisher phase and for the total experiment exhibited a quadratic response, being highest for the pigs fed the intermediate arginine levels. Gain/feed for the finisher phase followed the same trend as weight gain. Feed intakes for the finisher phase and total experiment were not different among treatments. Carcass data were collected on all barrows. There were no differences in hot carcass weight or adjusted average backfat among treatments. Loin eye area and percentage of lean decreased linearly as arginine level decreased in the diet. Plasma urea, arginine and orthinine concentrations decreased linearly with decreasing dietary arginine. Plasma lysine exhibited both a quadratic and a cubic response. The data indicate that reducing excess dietary arginine had little effect on performance or carcass composition and no consistent effect on plasma lysine of growing-finishing swine.