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This study investigated the effect of 2 different dietary amino acid treatments and feed restriction in early life versus a control treatment on development of the small intestine segments (weights), mortality, and broiler performance. Each treatment was applied to 6 cages with Ross 308 male broilers and to 6 cages with Cobb 500 male broilers with 24 birds per cage. A control treatment (100% ideal protein) was compared with a treatment with 30% extra ideal protein, a treatment with daily adjustment of the dietary amino acid level and profile, and a feed restriction treatment. The protein treatments were applied from 0 to 14 d of age. The feed restriction was applied from 4 to 21 d of age. Restriction was 15% from d 4 to 14 of age and diminished with equal daily steps thereafter to 5% at 21 d of age. Birds were weighed and dissected for evaluation of small intestine weights at 6, 9, 14, and 36 d of age. Feed intake restriction reduced leg problems in Ross and Cobb broilers. Extra dietary protein reduced leg problems in Ross broilers only. The present experiment does not show that small intestinal weight development is related to mortality. Thirty percent extra dietary ideal protein increased duodenum weight between 6 and 9 d of age. This was not further increased by the daily optimization of the dietary amino acid level and profile. The increased duodenum weights coincided with an improved BW gain. This indicates that duodenum weight may be important in facilitating BW gain in young broilers. Thus, it may be worthwhile to pay more attention to the relation between nutrition and duodenum weight and duodenum function in further studies.

Effects of early life experience with climatic (heat) and hygienic [lipopolysaccharide (LPS)] stress on adaptability to the same stressors in later life were studied in laying hens. Chicks were exposed to 37°C for 24 h at d 5 of age (n = 12) or were i.v.-administered once with 1 mg/kg of BW of LPS at 6 wk of age (n = 12), whereas a control group was reared under standard conditions receiving a placebo treatment of PBS (n = 36). At 24 wk of age, hens treated in early life were reexposed to the same stressor. Early life control hens were exposed to heat stress (n = 12), i.v.-administered with LPS (n = 12), or not exposed (n = 12). To evaluate improvement of adaptability, effects of climatic and hygienic stress on performance, humoral immune competence, and endocrine responsiveness were investigated in hens with early life experience to the stressors and hens only exposed to the stressors in later life. Early life heat exposure did not affect performance, immune, and endocrine parameters. Treatment × time interactions were found for level of antibody (Ab) binding to LPS and keyhole limpet hemocyanin (KLH) after LPS administration, indicating that hens with early life LPS experience differed in response level (Ab binding to LPS) and response pattern (Ab binding to LPS and KLH) compared with hens administered with LPS only at adult age. Our data suggest that early life heat stress exposure did not affect adaptability of laying hens to heat stress in later life. However, early life LPS exposure affected kinetics and magnitude of Ab levels binding to LPS and KLH, indicating that early life LPS exposure can enhance the status of immune reactivity or induce a higher sensitivity to LPS.

Effects of long-term climatic stress (heat exposure), short-term hygienic stress [lipopolysaccharide (LPS)], or a combination of both challenges on performance of 4 layer lines were investigated. The lines were earlier characterized by natural humoral immune competence and survival rate. At 22 wk of age, 80 hens per line were randomly divided over 2 identical climate chambers and exposed to a constant high temperature (32 degrees C) or a control temperature (21 degrees C) for 23 d. Half of the hens housed in each chamber were i.v. injected with LPS at d 1 after the start of the heat stress period. The effect of heat, LPS, or a combined challenge on feed intake, BW, hen-day egg production, egg weight, and egg shell thickness were investigated. Feed intake, BW, hen-day egg production, egg weight, and egg shell thickness were significantly reduced by heat stress. Administration of LPS significantly reduced feed intake, BW (LPS x time interaction), hen-day egg production, and egg weight (LPS x time interaction). Hens were able to recover from LPS administration but did not completely adapt to heat stress. Hens still lost weight, had a lower feed intake and hen-day egg production after 23 d of continuous exposure to heat stress. These data suggest a different nature of short-term LPS exposure versus long-term heat exposure affecting performance parameters of laying hens, and different adaptation mechanisms of hens toward these stressors. Neither natural humoral immune competence nor survival rate, for which the lines had been earlier characterized, were indicative of the response to different stressors. However, significant line x heat interactions were found for feed intake and hen-day egg production, and a line x heat x time interaction for BW, whereas a line x LPS interaction was found for hen-day egg production and a line x LPS x time interaction for BW. The lines had similar response patterns, but differed in response levels, suggesting that some lines were better able to adapt to stressors than others.

The effects of ambient temperature (T; 18 vs. 28 degrees C), dietary energy level [E; 90, 100, and 110% of NRC (1994) recommendations], and dietary lysine level [LYS; 105 vs. 120% of NRC (1994) recommendations], and their interactions on feed intake, BW gain, feed:gain ratio, and carcass yields of male turkeys were studied from 29 to 140 d of age. The experiment was designed as a split plot, including T as the main plot and E and LYS as the subplot, with 60 pens containing 10 male turkeys each. Overall, feed intake, BW gain, and feed:gain ratio were significantly lower at high compared with low T. Feed intake decreased linearly as E increased and was more pronounced at low compared with high T. Metabolizable energy intake increased more at high compared with low T as E increased. Turkeys that were fed the highest E gained less weight until 84 d of age than those fed the lowest E. Dietary lysine was not the limiting amino acid because birds showed no response to extra lysine. Feed:gain decreased linearly as E level increased. Until 84 d of age, feed:gain decreased more at low compared with high T as E level increased. Breast meat yields were lower, and thigh, drum, and wing yields were higher at high than at low T. The highest E resulted in lower cold carcass yields, and breast meat yields, and higher thigh and drum yields than the lowest E. Dietary lysine level did not affect carcass yield. The results imply that when dietary lysine levels are adequate, dietary energy may be increased above NRC (1994) to improve feed efficiency, but some of the limiting amino acids after lysine may be increased in high-density diets to optimize breast meat yield. Particularly at high temperature in the period after 16 wk of age, dietary energy contents may be increased to at least 110% of NRC (1994) because turkeys will need more energy to dissipate heat.

The current study investigated the effects of temperature manipulation (TM) during late embryogenesis on temperature preference, response to high environmental temperature, behavior, and performance in young layer chicks. Control (CC) embryos (n = 96) were incubated at 37.8 degrees C eggshell temperature throughout incubation. Thermally manipulated embryos (n = 96) were incubated at 37.8 degrees C eggshell temperature throughout incubation and were exposed to 40 degrees C for 4 h/d from embryonic d 14 to 18 (TM chicks). After hatch, chicks from each treatment were divided into 3 subgroups (n = 32 per group) and were subjected to a temperature preference test at d 1, 7, or 33. One day after the temperature preference test, each subgroup was exposed to 1 thermal challenge for 4 h (d 2, 40 degrees C; d 8, 40 degrees C; or d 34, 35 degrees C). Effects of TM on (fearfulness) behavior of chicks were investigated in a tonic immobility test and during home pen observations. Temperature manipulation decreased incubation time with 7 h (P0.0001) and body temperature at hatch with 0.2 degrees C (P = 0.002). The TM chicks preferred a lower ambient temperature in the temperature preference test (P0.05) and showed a higher body temperature response than CC chicks to the thermal challenge at d 2 and 8 (P0.05). No effects of TM on behavior and performance were observed. Because most TM studies are conducted in broilers, this study is the first attempt to unravel the effects of TM during late embryogenesis on posthatch environmental adaptation in layer chicks. The results demonstrated that effects of our TM on postnatal temperature preference and response to high environmental temperatures are only found until d 8 of age. This may suggest 1 of 3 options: a) the timing or the level, or both, of TM and duration were not at the sensitive period of embryogenesis or not sufficient, or both, respectively; b) the level of the postnatal thermal challenge was not strong enough to induce a hyperthermic response; and c) the postnatal effects of TM in layers are limited in time.