Diet density during the first week of life: Effects on growth performance, digestive organ weight, and nutrient digestion of broiler chickens.

The current study aimed to investigate whether diet density affects growth performance and nutrient digestion during the first wk after hatch and digestive organ weight at 7 d of age. Effects were studied using a dose-response design consisting of 5 dietary fat levels (3.5, 7.0, 10.5, 14.0, and 17.5%). The dietary fat level was increased through soybean oil inclusion. Amino acids, minerals, and the premix were increased at the same ratio as dietary fat. Consequently, diets were kept neither isocaloric nor isonitrogenous. Broiler chickens were weighed on d 0 and d 7 after hatch, whereas feed intake was measured daily. Excreta produced from d 0 to d 7 was collected at d 7. Dietary dry matter and nitrogen metabolizability, as well as fat digestibility were calculated as an average over 7 days. Broiler chickens were sampled at d 7 to determine carcass yield, breast meat yield, and organ weights. Average daily gain (P = 0.047) and average daily feed intake (P < 0.001) decreased linearly as diet density increased, while gain to feed ratio increased linearly (P < 0.001). An increased diet density resulted in a linear decrease of crop, liver, and pancreas weight relative to body weight (BW; P < 0.05). Duodenum, jejunum, ileum, and cecum length (expressed as cm/kg of BW) and empty weight (as % of BW) increased linearly with increased diet density (P < 0.05). Dietary dry matter metabolizability decreased linearly as diet density increased (P < 0.001), whereas fat digestibility and nitrogen metabolizability were not affected (P > 0.05). In conclusion, one-week-old broiler chickens respond to increased diet densities by increasing intestinal weight and length, while decreasing liver and pancreas weight. This may be an adaptive response to cope with an increased nutrient concentration in the diet.

Diet density during the first week of life: Effects on energy and nitrogen balance characteristics of broiler chickens.

This study aimed to determine effects of diet density on growth performance, energy balance, and nitrogen (N) balance characteristics of broiler chickens during the first wk of life. Effects of diet density were studied using a dose-response design consisting of 5 dietary fat levels (3.5, 7.0, 10.5, 14.0, and 17.5%). The relative difference in dietary energy level was used to increase amino acid levels, mineral levels, and the premix inclusion level at the same ratio. Chickens were housed in open-circuit climate respiration chambers from d 0 to 7 after hatch. Body weight was measured on d 0 and 7, whereas feed intake was determined daily. For calculation of energy balances, O2 and CO2 exchange were measured continuously and all excreta from d 0 to 7 was collected and analyzed at d 7. Average daily gain (ADG) and average daily feed intake (ADFI) decreased linearly (P = 0.047 and P < 0.001, respectively), whereas gain to feed ratio increased (P < 0.001) with increasing diet density. Gross energy (GE) intake and metabolizable energy (ME) intake were not affected by diet density, but the ratio between ME and GE intake decreased linearly with increasing diet density (P = 0.006). Fat, N, and GE efficiencies (expressed as gain per unit of nutrient intake), heat production, and respiratory exchange ratio (CO2 to O2 ratio) decreased linearly (P < 0.001) as diet density increased. Energy retention, N intake, and N retention were not affected by diet density. We conclude that a higher diet density in the first wk of life of broiler chickens did not affect protein and fat retention, whereas the ME to GE ratio decreased linearly with increased diet density. This suggests that diet density appears to affect digestibility rather than utilization of nutrients.

Effects of feed access after hatch and inclusion of fish oil and medium chain fatty acids in a pre-starter diet on broiler chicken growth performance and humoral immunity.

Delayed feed and water access is known to impair growth performance of day old broiler chickens. Although effects of feed access on growth performance and immune function of broilers have been examined before, effects of dietary composition and its potential interaction with feed access are hardly investigated. This experiment aimed to determine whether moment of first feed and water access after hatch and pre-starter composition (0 to 7 days) affect growth rate and humoral immune function in broiler chickens. Direct fed chickens received feed and water directly after placement in the grow-out facility, whilst delayed fed chickens only after 48 h. Direct and delayed fed chickens received a control pre-starter diet, or a diet containing medium chain fatty acids (MCFA) or fish oil. At 21 days, chickens were immunized by injection of sheep red blood cells. The mortality rate depended on an interaction between feed access and pre-starter composition (P=0.014). Chickens with direct feed access fed the control pre-starter diet had a higher risk for mortality than chickens with delayed feed access fed the control pre-starter diet (16.4% v. 4.2%) whereas the other treatment groups were in-between. BW gain and feed intake till 25 days in direct fed chickens were higher compared with delayed fed chickens, whilst gain to feed ratio was lower. Within the direct fed chickens, the control pre-starter diet resulted in the highest BW at 28 days and the MCFA pre-starter diet the lowest (Δ=2.4%), whereas this was opposite for delayed fed chickens (Δ=3.0%; P=0.033). Provision of MCFA resulted in a 4.6% higher BW gain and a higher gain to feed ratio compared with other pre-starter diets, but only during the period it was provided (2 to 7 days). Minor treatment effects were found for humoral immune response by measuring immunoglobulins, agglutination titers, interferon gamma (IFN- γ ), and complement activity. Concluding, current inclusion levels of fish oil (5 g/kg) and MCFA (30 g/kg) in the pre-starter diet appear to have limited (carryover) effects on growth and development, as well as on humoral immune function.

Effects of moment of hatch and feed access on chicken development.

The current study evaluated effects of hatch moment and immediate feed and water access within a 24-h hatch window on chicken growth and development. Five hundred four male chickens obtained from a 49-wk-old Ross 308 breeder flock were assigned to 72 cages based on hatching moment (early, midterm, or late; selected during periods of 475 to 481, 483 to 487, and 489 to 493 h after onset of incubation). At the end of each hatching period, chickens were moved to the grow-out facility and one-half of the chickens received feed and water ad libitum immediately. Remaining chickens received feed and water from 504 h after onset of incubation (d 0). Body weight gain and feed intake for each cage were recorded at d 0, 1, 4, 7, 11, and 18. Chickens were sampled at d 4 and 18 for organ and carcass development. Early hatchers had lower BW at placement compared with midterm and late hatchers but compensated for this afterward, resulting in a higher BW at d 4 (112.8, 107.1, and 103.3 g, respectively). From d 0 to 18, early hatchers tended to have higher BW gain than both other groups. Relative breast meat yield at d 18, expressed as percentage of carcass weight, was higher for early (30.4%) than midterm (28.5%) and late hatchers (27.8%). Up to d 7, direct feed access resulted in higher BW gain (6.1%) and feed intake (4.2%) compared with delayed feed access. No effect of moment of feed access on feed efficiency or organ weights was found. Direct feed access resulted in a higher weight:length ratio of the jejunum (12.5%) and ileum (7.5%) at d 4 compared with delayed feed access. These results suggest that early hatchers have a different developmental and growth pattern than midterm or late hatchers within a 24-h hatch window. A mild delay in feed access after hatch affects growth and development during the first week after hatch.

Lactulose as a marker of intestinal barrier function in pigs after weaning.

Intestinal barrier function in pigs after weaning is almost exclusively determined in terminal experiments with Ussing chambers. Alternatively, the recovery in urine of orally administered lactulose can be used to assess intestinal permeability in living animals. This experiment was designed to study the barrier function of the small intestine of pigs over time after weaning. The aim was to relate paracellular barrier function (measured by lactulose recovery in the urine) with macromolecular transport [measured by horseradish peroxidase (HRP) using Ussing chambers] and bacterial translocation to assess whether lactulose recovery is related to possible causes of infection and disease. Forty gonadectomized male pigs (6.7 ± 0.6 kg) were weaned (d 0) at a mean age of 19 d, fitted with urine collection bags, and individually housed. Pigs were dosed by oral gavage with a marker solution containing lactulose (disaccharide) and the monosaccharides l-rhamnose, 3-O-methylglucose, and d-xylose at 2 h and at 4, 8, and 12 d after weaning. The recovery of sugars in the urine was determined over 18 h after each oral gavage. The day after each permeability test, the intestines of 10 pigs were dissected to determine bacterial translocation to the mesenteric lymph nodes and jejunal permeability for HRP in Ussing chambers. Recovery of l-rhamnose in urine was affected by feed intake and by the time after weaning (P ≤ 0.05). Recovery of lactulose from the urine was greater (P ≤ 0.05) at 4, 8, and 12 d after weaning compared with the first day after weaning and was negatively correlated with feed intake (r = -0.63, P ≤ 0.001). The mean translocation of aerobic bacteria to the mesenteric lymph nodes was greater at 5 and 13 d after weaning compared with d 1 (P ≤ 0.05). Lactulose recovery showed no correlation with permeability for HRP nor with bacterial translocation (P > 0.05). Although both lactulose recovery and bacterial translocation increased over time after weaning, lactulose recovery did not correlate with the permeability for HRP nor bacterial translocation within a pig (P > 0.05). Therefore, we conclude that lactulose recovery in the urine of pigs after weaning is not associated with risk factors for infections. However, it appears to be possible to measure paracellular barrier function with orally administered lactulose in pigs shortly after weaning. Further studies will reveal whether this variable is relevant for the long-term performance or health of pigs after weaning.

Dietary amino acid levels and feed restriction affect small intestinal development, mortality, and weight gain of male broilers.

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 amino acids on egg number and egg mass of brown (heavy breed) and white (light breed) laying hens.

Different types (light to heavy) of laying hens are used in practice. There are questions about the optimum level of balanced protein (BP) supply in feed for different types of hens. Therefore, a broad range of amino acids intake levels [550 to 800 mg of true fecal digestible (TFD) Lys/hen per d] was tested on heavy (Lohmann Brown Classic) and light (Lohmann LSL Classic) laying hens from 24 to 60 wk of age. The other indispensable amino acids were fed in fixed ratios to TFD Lys in all treatments. A total of 282 Lohmann Brown Classic and 282 Lohmann LSL Classic hens (24 wk of age) were divided into 12 experimental groups (individually housed) based on daily egg mass production and BW. Replicates of the heavy strain started with a similar average daily egg mass production (51.1 g/hen per d), laying percentage (95.9%), and hen weight (1,860 g). Replicates of the light strain started with a similar average daily egg mass production (52.0 g/hen per d), laying percentage (97.3%), and hen weight (1,478 g). Diets were fed restrictively with an aimed feed intake of 110 g/hen per day [308 kcal/hen per d of AME(n (layers))] and 100 g/hen per day [280 kcal/hen per d of AME(n (layers))] for heavy and light hens, respectively, to achieve the required BP intake levels. For light hens, a BP intake with 600 mg of TFD Lys was sufficient for optimal laying percentage, whereas maximum laying percentage was not achieved with the highest TFD Lys in heavy hens. For egg weight, daily egg mass production as well as feed conversion regression analysis revealed that asymptotes were not achieved with the highest amino acid levels in both layer strains.

Responses of male growing broilers to increasing levels of balanced protein offered as coarse mash or pellets of varying quality.

Two experiments with 14- to 35-d-old male broilers were performed to investigate the interactions between increasing levels of balanced protein (BP; 9.7, 10.7, 11.7, and 12.7 g of digestible Lys/kg of feed) and physical feed form. In Experiment 1 diets were offered as coarse mash and pellets of either good or poor quality. Good pellet quality was characterized by high durability. In Experiment 2 diets were offered as good quality pellets or coarse mash. However, for the latter particle size, distribution either was kept constant with increasing BP or changed with increasing proportion of soybean meal. Feed intake generally decreased with increasing BP; however, feed intake was highest in good pellets fed to broilers and lowest in mash fed to birds. Although there was only a small response on weight gain in mash-fed birds, feed conversion improved substantially for all feed forms with increasing BP. Particle size distribution did not affect this effect. Highest weight gain was achieved with good pellets; to achieve similar performance with poor pellet quality, higher levels of BP were needed. Carcass evaluation suggested increasing breast meat yield and particularly decreasing fat accretion with increasing BP. Results of both experiments indicate that optimum dietary amino acid levels for growing broilers may vary among different physical feed forms.

Effects of different dietary ideal protein levels on male and female broiler performance during different phases of life: single phase effects, carryover effects, and interactions between phases.

Several experiments in which the dietary ideal protein (IP) levels were increased indicate that with current IP recommendations the maximum performance of broilers will not be achieved. However, available data of this IP-increment approach is scarce and, for the starter phase, entirely lacking. The objective of the present study, therefore, was to generate data regarding the effects in the starter phase and to test the impact of adequate vs. high IP levels in preceding phases on the response to IP increment in the phase under study. To evaluate this, an IP dose response in the starter phase and factorial arrangements combining adequate or high IP levels in starter and grower diets with low, adequate, or high IP levels in finisher diets were carried out with male and female broilers. Enhanced dietary IP levels in the starter diet increased BW gain in the starter phase and in the consecutive grower phase. Moreover, it was shown that a delay in BW gain due to suboptimal IP levels in the starter diet could only be partly compensated for in later phases of life. These results demonstrate the need for a reevaluation of IP levels used in practical starter diets. Feed conversion efficiency and BW gain responses to increased IP levels in the grower and finisher diets were less pronounced when high compared with adequate IP levels were fed in the preceding phase. This difference in response could not be detected statistically but was consistent between experiments and phases. Therefore, this phenomenon should not simply be neglected.

Effect of different dietary ideal protein concentrations on broiler performance.

1. The aim of the study was to examine the response of male broilers of different age categories to different dietary ideal protein (IP) concentrations and to compare the effects to IP recommendations based on single lysine (Lys) requirement studies from the literature. 2. Two experiments were carried out, in which diets containing different IP concentrations (9.0 to 14.4g apparent faecal digestible (AFD) Lys/kg) were fed to male broilers from 14 to 34 (Exp. 1) and 28 to 41 d of age (Exp. 2). The diets (12.88MJ AMEN/kg) were prepared by the dilution technique. The effect of dietary IP concentrations on weight gain, feed intake, feed conversion efficiency (FCE) and slaughter characteristics were studied in both experiments. 3. In Exp. 1, weight gain and FCE increased linearly and fat concentration in the carcase decreased with increasing IP concentration. In Exp. 2, weight gain and FCE improved exponentially, whereas breast meat yield improved linearly with increasing dietary IP concentration. On the basis of these results, it was concluded that the weight gain and FCE of male broilers respond to higher dietary IP levels than would be expected from single lysine requirement studies in the literature.