A study was conducted to evaluate Gly requirements in low-CP diets with different levels of digestible (dig) Thr, and their effects on performance, intestinal mucosal development, and nutrient utilization of broiler chickens from 21 to 35 d age. A total of 240 twenty-one-day-old Cobb-Vantress male broiler chickens were distributed in a completely randomized 4 × 2 factorial arrangement for a total of 8 treatments with 5 replicates of 6 birds each. The treatments consisted of 4 levels of Gly+Ser (1.47, 1.57, 1.67, or 1.77%) and 2 levels of dig Thr (0.70 or 0.77%, corresponding to 100 or 110% of Thr requirements, respectively). Common diets were fed to broilers until 20 d of age. At d 35, an interaction (P ≤ 0.01) was observed between the Gly+Ser and dig Thr levels for G:F. Glycine supplementation resulted in a linear increase (P < 0.05) in BW gain, G:F, intestinal mucin secretion, apparent digestibility of fat, and AME values of the experimental diets. Threonine levels greater than the levels required (0.77%) improved (P < 0.05) G:F and increased (P < 0.05) intestinal mucin secretion. However, intestinal morphometry and the number of goblet cells in the duodenum, jejunum, and ileum were not affected by the treatments. The dietary Gly+Ser level necessary to optimize G:F in low-CP diets containing 0.77% Thr for broiler chickens during growth was estimated to be 1.54%; however, this requirement may be greater than 1.77% in diets with 0.70% Thr. Supplemental Gly may be essential to support maximum performance for broiler chickens from 21 to 35 d of age when they are fed diets based exclusively on vegetable ingredients and with low protein levels. Glycine can directly or indirectly influence the proper function of the intestinal mucosa and improve dietary energy utilization.

1. Two experiments were performed to study the supplementation of valine, isoleucine, arginine and glycine (Val, Ile, Arg, Gly) in low-protein diets for broiler chickens in the starter (1-21 d; Exp. 1) and grower (22-42 d; Exp. 2) phases. 2. A low-crude protein (CP) diet was formulated to meet the requirements of all amino acids (AA) supplied by the control diet except for Val, Ile, Arg and Gly. The other experimental diets were obtained by the isolated or combined supplementation of the studied AA in the low-CP diet. 3. Growth, serum parameters and litter characteristics were taken in both of the experiments. Carcass measurements were taken in Experiment 2. 4. In the starter and grower phases, low-CP diets without supplementation resulted in birds with a poorer weight gain and feed conversion than those of the birds that received the control diet. 5. In the starter phase, individual supplementation with Val and Gly, but not Ile and Arg, restored the weight gain of the birds, while diets with the addition of Val + Gly, Val + Ile + Arg, Val + Ile + Gly and Val + Ile + Arg + Gly restored their feed conversion. 6. In the grower phase, weight gain was re-established at the same rate as the control diet for the diets supplemented with Val + Ile, Val + Ile + Arg, Val + Ile + Gly and Val + Ile + Arg + Gly. However, the feed conversion was restored only in birds that received the diet supplemented with all studied AA. 7. The supplementation of Val and Gly in low-CP diets was sufficient to avoid adverse effects in the performance and serum parameters of broilers in the starter phase. However, birds in the grower phase required the combined supplementation of Val, Ile, Arg and Gly, to prevent compromised performance.

The objective of this study was to determine the requirements and interactions between the standardized ileal digestible (SID) Leu and Val levels in low-protein diets, and their effects on performance, serum characteristics, carcass yield and diameter of muscle fibers of broiler chickens from d 21 to 42 posthatch. A total of 1,500 21-day-old Cobb 500 male broiler chickens were distributed in a completely randomized design in a 5 × 5 factorial arrangement for a total of 25 treatments with 3 replicates of 20 birds each. Treatments consisted of 5 SID Leu levels (1.0, 1.2, 1.4, 1.6, or 1.8%) and 5 SID Val levels (0.52, 0.67, 0.82, 0.97, or 1.12%). At 42 d of age, there was interaction (P < 0.05) between the SID levels of Leu and Val on feed intake and weight gain. There was a quadratic effect (P < 0.05) of Leu and Val levels on feed conversion, with minimal point estimated at the levels of 1.19 and 0.86%, respectively. Dietary Leu supplementation reduced linearly (P < 0.05) serum concentrations of triglycerides and β-hydroxybutyrate. Dietary Leu increased (P ≤ 0.05) the fiber diameters of the pectoralis major muscle and breast yield at the levels of 1.24 and 1.13%, respectively, while the thigh yield was improved with the level of 0.71% Val. Abdominal fat decreased linearly (P < 0.05) with increasing levels of dietary Leu and Val. The SID Leu and Val levels needed to optimize weight gain and feed conversion in low-CP diets for broiler chickens from d 21 to 42 posthatch were estimated at 1.15 and 0.86%, and 1.19 and 0.86%, respectively. The supplementation of Leu and Val can reduce the abdominal fat deposition in birds fed low-CP diets during the grower phase. Leu and Val interactions can influence the performance but not the serum characteristics, carcass yield and diameter of muscle fibers of broilers fed low-protein diets. Therefore, it is necessary to consider the dietary Leu content to estimate the ideal level of Val in low-CP diets for optimum broiler performance.

This study was conducted to assess the effect of dietary supplementation of meat-type quail breeders with guanidinoacetic acid (GAA) on their reproductive parameters and progeny performance. Two hundred forty meat-type quails at 25 wk of age were distributed in a completely randomized design with 5 treatments and 8 replicates of 6 birds each. The treatments consisted of 5 dietary levels of GAA (0.00, 0.06, 0.12, 0.18, and 0.24%). The progenies from quail breeders were housed according to breeder treatments and fed a conventional diet based on corn and soybean meal without GAA supplementation. Dietary GAA levels did not affect (P > 0.05) the productivity of meat-type quail breeders, although the concentration of guanidinic compounds (creatine, GAA, and creatinine) in the eggs from the breeders increased linearly (P < 0.05) according to the increase in dietary GAA levels. The number of spermatozoa present in the vitelline membrane was not affected (P > 0.05) by the treatments, but there was a quadratic effect (P < 0.05) of the levels of GAA on fertility, embryonic mortality, and egg hatchability, with the best results estimated at 0.13, 0.15, and 0.14% GAA, respectively. The creatine levels of the pectoral muscle in newborn quails showed a quadratic effect (P ≤ 0.07), and the dietary GAA level of 0.11% was estimated to maximize the muscular creatine level in the progeny. There was a quadratic effect (P < 0.05) of GAA levels on weight gain and feed conversion of progeny at 35 d of age with an optimization point of 0.14% GAA for these variables. Dietary GAA supplementation of meat-type quail breeders increases the availability of creatine in eggs and muscle of progeny, which results in better reproductive parameters and better postnatal progeny performance.

This work studied the effect of supplementing commercially available amino acids in low-protein diets using different ratios of digestible (dig) glycine+serine:lysine (Gly+Ser:Lys) on performance, serum parameters, feathering, and litter characteristics of broiler chickens during the starter period. A total of one thousand fifty 1-d-old Cobb-Vantress male chicks were distributed in a completely randomized experimental design into 6 treatments with 5 replicates of 35 birds each. The treatments were as follows: T1, control diet based on corn and soybean meal formulated with 22% CP (dig Gly+Ser:Lys ratio of 147); T2, diet with a 2% CP reduction, supplemented with Val (dig Gly+Ser:Lys ratio of 137); T3, similar to T2 with the addition of Gly (dig Gly+Ser:Lys ratio of 147); T4, diet with a 3% CP reduction, supplemented with Val, Ile, and Arg (dig Gly+Ser:Lys ratio of 127); and T5 and T6, similar to T4 with the addition of Gly (dig Gly+Ser:Lys ratios of 137 and 147, respectively). At 7 and 21 d, broilers that had received diets with a 3% CP reduction (19% CP) and a Gly+Ser:Lys ratio that was equivalent to 127 had lower G:F (P < 0.05) and lower total protein and albumin serum concentrations (P < 0.05) than those broilers that received the control feed. However, these parameters were restored to the same level as the control diet with an increase in the dig Gly+Ser:Lys ratio from 127 to 137 and 147. Diets with a 3% CP reduction (19% CP) resulted in litter with reduced (P < 0.05) nitrogen content and lower ammonia emission than the litter of broilers receiving the control diet. The treatments did not influence (P > 0.05) the feather length or feathering scores at 21 or 28 d of age. The supplementation of essential amino acids while maintaining dig Gly+Ser:Lys ratios at and above 137 allowed for a reduction in the dietary CP of 3% without undermining the performance, feathering or serum parameters of early stage broilers.

Four experiments were conducted to estimate the optimal standardized ileal digestible ( SID ) level of branched-chain amino acids in low-protein diets during the starter, grower, and finisher periods, using the response surface methodology, and to study their effects on performance and mRNA expression of genes involved in the mechanistic target of rapamycin ( mTOR ) pathway of broiler chickens from 8 to 21 D of age. In experiments 1, 2, and 3, a total of 1,500 Cobb male broiler chickens were assigned to 15 diets of a central composite rotatable design ( CCD ) of response surface methodology containing 5 levels of SID Leu, Val, and Ile with 5 replicate pens of 20 birds each. A 3-factor, 5-level CCD platform was used to fit the second-order polynomial equation of broiler performance. In experiment 4, a total of 540 8-day-old Cobb male broiler chickens were distributed in a completely randomized 2 x 3 x 3 factorial arrangement with 2 SID Leu levels (1.28 or 1.83%), 3 SID Val levels (0.65, 0.90, or 1.20%), and 3 SID Ile levels (0.54, 0.79, or 1.09%) for a total of 18 treatments with 5 replicate cages of 6 birds each. High Leu levels impaired (P < 0.05) gain:feed when birds were fed marginal Val or Ile diets. However, gain:feed was restored when both Val and Ile were supplemented to reach adequate or high levels. High Leu levels increased ( P < 0.05) mRNA expression of S6K1 and eEF2 genes only in birds fed high Ile levels. Dietary SID Leu, Val, and Ile levels required for gain:feed optimization in low-protein diets were estimated at 1.37, 0.94, and 0.87% during the starter period; 1.23, 0.82, and 0.75% during the grower period; and 1.15, 0.77, and 0.70% during the finisher phase, respectively. Higher Val and Ile levels are required to optimize the effect of Leu supplementation on mRNA expression of mTOR pathway genes in the pectoralis major muscle of broilers from day 1 to 21 after hatch.

1. The objective of this study was to determine the optimum glycine+serine (Gly+Ser) concentration in low-crude protein (CP) diets that have adequate or high concentrations of dietary threonine (Thr) for broiler chickens in the initial growth phase. 2. Treatments consisted of four concentrations of dietary Gly+Ser (18.4; 19.8; 21.2 and 22.6 g/kg) and two concentrations of dietary Thr (9.3 and 10.7 g/kg, corresponding to 100 and 115% of the required Thr, respectively). 3. At 21d, interactions were observed between dietary Gly+Ser and Thr concentrations for the feed conversion ratio, creatine content in the pectoral muscles and serum concentrations of uric acid. There was a quadratic effect of the concentrations of Gly+Ser in the diets with 9.3 g Thr/kg on the feed conversion ratio and creatine content in the pectoral muscles, with an optimisation concentration of 20.8 and 21.1 g Gly+Ser/kg, respectively. 4. Diets containing 10.7 g Thr/kg negatively affected the feed conversion ratio, relative breast weight, creatine content in the pectoral muscles, serum concentrations of uric acid and ammonia in poultry compared to diets containing 9.3 g Thr/kg. 5. The need for Gly+Ser in diets with low-protein concentration (190 g CP/kg) and adequate concentration of Thr (9.3 g/kg) is 20.8 g/kg for broilers in the 1- to 21-d phase.

The aim of this study was to evaluate the hepatoprotective effect of silymarin in diets contaminated or not with aflatoxin B1 (AFB1) on the productive performance and serum biochemical profile of Japanese quail (Coturnix coturnix japonica) in the laying phase. A total of 240 12-week-old Japanese quail was used in a completely randomized design in a 3 × 2 factorial scheme (additives x contaminated or not with AFB1 - 1,500 μg/kg), totaling 6 treatments and 5 replicates of 8 birds each. The additives used were silymarin (500 g/ton), adsorbent (1 kg/ton), and a control diet (without additive). Of the total aflatoxin content, 84.64% was AFB1; 4.28% was AFB2; 11.07% was AFG1; and AFG2 was not detected. The data were submitted to ANOVA, and means were compared by Tukey's test. There was no interaction (P > 0.05) between the additive and AFB1 on performance parameters. However, the inclusion of AF in diets reduced (P < 0.05) egg weight and feed intake, impairing feed conversion compared to the unchallenged groups. There was an increase (P < 0.05) in blood concentrations of aspartate aminotransferase (AST), gamma-glutamyltransferase (GGT), and creatine kinase (CK) in birds challenged with AFB1, regardless of the additive used, characterizing a possible alteration in hepatic metabolism. Serum total protein and globulin levels were reduced (P < 0.05) in birds challenged with toxins. The consumption of diets contaminated with 1,500 μg AFB1/kg altered hepatic function in quail, impairing productive performance and egg weight. The concentrations of silymarin and adsorbent evaluated in this study were not able to mitigate the negative effect of toxins on the metabolism and performance of laying quail.