Influence of supplemental lysine, isoleucine, threonine, tryptophan and total sulfur amino acids on egg weight of Hy-line W-36 hens.

Four experiments were conducted to determine whether synthetic lysine, isoleucine, threonine, and tryptophan (LITT) or TSAA supplementation to diets formulated based on lysine improved egg weight (EW) and hen performance. In Experiment 1, diets were formulated with three TSAA levels (0.65,0.72, and 0.81%). These diets were fed with and without adding lysine and isoleucine each at 0.055% and threonine and tryptophan each at 0.022%. Treatments were randomly assigned to 960 Hy-Line W-36 hens in eight replicates per treatment (20 birds/replicate). Inclusion of LITT improved (P < 0.05) EW within 2 wk with no TSAA x LITT interaction. Inclusion of LITT also increased average feed consumption (FC) by 1.4 g/d (P < 0.01). However, no effect (P > 0.05) of LITT was observed on egg production (EP), egg specific gravity (SG), or BW. The EW, EP, and FC increased linearly (P < 0.05) as dietary TSAA increased. The TSAA had no effect on SG or BW. In Experiment 2, supplemental LITT were removed to determine how rapidly hens lose the effect of LITT on performance. Within 2 wk, the effect of LITT on EW was lost. Average EW, EP, and FC of hens fed higher TSAA levels remained higher (P < 0.05) than hens fed 0.65% TSAA. In Experiment 3, all hens were fed a diet containing 0.65% TSAA to determine the time it takes to lose the effect of TSAA supplementation. The TSAA supplementation effect on EW, EP, and FC observed in the previous two experiments was lost within 1 wk. In Experiment 4, hens were again fed diets similar to Experiment 2 to confirm the time required for TSAA supplementation to improve EW. Within 1 wk, hens fed 0.72 or 0.81% TSAA improved (P < 0.05) EW over hens fed 0.65% TSAA. It was concluded that hens fed diets formulated based on lysine were deficient in LITT. Hens responded to the inclusion or removal of supplemental LITT and TSAA within 1 to 2 wk.

Influence of dietary phosphorus on performance of Hy-line W36 hens.

Two experiments were conducted to determine the effect of nonphytate phosphorus (NPP) on hen performance in an environmentally controlled house. In Experiment 1, 21-wk-old Hy-Line W36 hens (n = 1,248) were randomly assigned to 13 dietary treatments (0.1 to 0.7% NPP, at graded increments of 0.05%) for 17 wk. In Experiment 2, 45-wk-old Hy-Line W36 hens (n = 960) were randomly allocated to eight diets in a 2 x 4 factorial arrangement of treatments. Two levels of Ca (3 and 4%) and four levels of NPP (0.1, 0.2, 0.3, and 0.4%) were fed for 8 wk. Feed consumption (FC), egg production (EP), egg weight (EW), egg specific gravity (ESG), bone density (BD), bone mineral content (BMC), bone breaking strength (BBS), BW and mortality were evaluated to determine performance. Results of Experiment 1 indicated that FC, EP, and BW increased as NPP was increased from 0.1 to 0.7% (77 to 588 mg/hen/d). During Week 12, a sharp decrease in FC and EP was observed in hens fed the most deficient level of 0.1% NPP. Egg weight and ESG decreased linearly (P < 0.05) as dietary NPP was increased from 0.1 to 0.7%. However, after 14 wk, ESG decreased (P < 0.05) in hens fed 0.1% NPP. Bone breaking strength was higher (P < 0.05) in hens fed 0.3 to 0.4% NPP, indicating maximum bone quality. Mortality was higher (P < 0.05) in hens fed 0.01% NPP, followed by hens fed 0.15% NPP. In Experiment 2, a pronounced adverse effect of P deficiency was observed on FC and EP within 2 wk compared with 12 wk in Experiment 1. Reduction of NPP to 0.1% reduced BD, BMC, BBS and increased hen mortality (P < 0.05). Reducing dietary Ca from 4 to 3% decreased ESG (P < 0.05). A wide variation in response time to P deficiency indicated that P requirement varied for different performance criteria with age.

Influence of cage density and prior dietary phosphorus level on phosphorus requirement of commercial leghorns.

Two studies were conducted to determine whether cage density and prior dietary nonphytate P (NPP) level affect hens' P requirements. In Experiment 1, hens were housed at three cage densities (300, 400, and 600 cm2 or 46.5, 62.0, and 93.0 inches2/hen) and fed four levels of NPP (0.15, 0.25, 0.35, and 0.40%) for 6 wk to determine the effect of cage density on the P requirement. Egg production (EP), feed consumption (FC), egg weight (EW), and egg specific gravity (ESG) were measured to evaluate performance. Cage density influenced EP within Week 1 (P < 0.01), and during Weeks 5 and 6, there was a cage density x NPP-level interaction (P < 0.05). At 300 cm2, EP was more severely affected by 0.15 and 0.25% NPP than at 400 and 600 cm2. A linear decrease (P < 0.001) in FC was observed because of decreased NPP. Hens at 300 cm2 consumed 4 g less feed/hen per d than hens at 400 cm2. A linear decrease in EW was observed as the NPP level decreased (P < 0.01) from 0.25 to 0.15%, and there was no effect of cage density. Experiment 2 was conducted to determine the effect of prior dietary P levels on time required to create a P deficiency. Hens fed 0.4% NPP were divided into two groups and fed 0.25 and 0.4% NPP for 4 wk. At the end of 4 wk, hens fed 0.25% NPP were further divided into three groups and were fed diets containing 0.09, 0.25, and 0.30% NPP for an additional 6 wk. Hens fed 0.4% NPP were divided into three groups and fed diets containing 0.09, 0.4, and 0.45% NPP. Reduction of NPP from 0.4 and 0.25% to 0.09% reduced EP by 8.5 and 6.8%, respectively, within 3 wk. Prior NPP levels had no influence on time required to create a P deficiency in terms of EP. Reduction of NPP from 0.4 and 0.25% to 0.09% reduced (P < 0.05) FC. A decline in FC occurred 2 wk earlier in hens previously fed 0.4% than those fed 0.25% NPP. This result indicates that hens fed 0.4% NPP became P deficient more quickly than hens fed 0.25%. We concluded that cage density and prior NPP level affect the hen P requirements or time required to create a P deficiency.

Influence of supplemental phytase on performance of broilers four to six weeks of age.

The influence of dietary phytase on phytate P availability was investigated using Ross x Hubbard male broiler chicks. A randomized complete block design with a factorial arrangement of 2 x 3 was used with eight replicates (n = 2,400; 50 chicks per replicate) per treatment. Diets were formulated to contain two levels of nonphytate P (NPP; 0.225 and 0.325%) and three levels of phytase [0, 300, and 600 phytase units (FTU)/kg] with 0.75% Ca. An additional diet with 0.425% NPP and 0.85% Ca was used as a positive control (n = 400). Prior to assigning treatments, all chicks were fed a commercial starter mash adequate in all nutrients until 3 wk of age. Neither performance nor bone strength was significantly influenced by a reduction of NPP to 0.325% and Ca to 0.75% as compared to the positive control. However, when NPP was reduced to 0.225% and Ca to 0.75%, significant negative impacts on body weight, feed consumption, feed efficiency, and bone strength were observed. Phytase significantly increased BW at the lower NPP level but not at the higher NPP level. A significant NPP by phytase interaction occurred in bone criteria and livability. Phytase (300 FTU/kg) had greater influence on bone mineral content, bone density, bone breaking strength, and livability in broilers fed 0.225% NPP than in broilers fed 0.325% NPP. This study indicates that supplementing phytase in grower diets containing reduced levels of NPP and Ca significantly improved performance and bone strength of broilers. In diets containing marginal to deficient levels of either NPP or Ca or both, the addition of microbial phytase at 300 to 600 FTU/kg feed prevents P deficiency symptoms. Increasing phytase levels from 300 to 600 FTU/kg feed provided no additional benefit.