Plasma concentrations of corticosterone and thyroid hormones in laying fowls from different housing systems

Plasma concentrations of corticosterone, thyroxine (T4) and triiodothyronine (T3) were measured in representative mature female domestic fowls from three housing systems: cages, covered strawyard and range. There were no between-system differences for T4 but T3 was lower in birds from range than in those from cages. Corticosterone concentrations were lower in birds from strawyards than in those from range and cages. In the strawyards there were no differences in corticosterone concentrations between normal and low-ranking hens. The latter were selected on the basis that they remained apart from the flock, were under-weight, poorly feathered and unable to feed at will. Low-ranking hens had significantly higher plasma concentrations of T3 and T4 than normal birds. This was attributed mainly to the poor feather covering of most low-ranking birds. It was concluded that, in the assessment of different housing systems, plasma corticosterone and thyroid hormones were not useful measures of long-term stress or welfare. Different factors relevant to welfare may have contrary effects on the plasma concentrations of these hormones.     

不同日粮条件下添加维生素E对蛋种鸡繁殖性能的影响

本试验选择220日龄健康的伊莎父母代种鸡6000羽,随机分为8组,每组8个重复.Ⅰ、Ⅱ、Ⅲ、Ⅳ组为常 规日粮组,分别添加维生素E0、40、180、300 mg/kg;V、Ⅵ、Ⅶ、Ⅷ组为非常规基础日粮,分别添加维生素E0、40、180、300 mg/kg.通过8周饲养试验,测定不同剂量的维生素E对蛋种鸡受精率、死胎率、...     

The performance of laying hens fed on rearing and laying diets containing urea

In an experiment using 2880 light hybrid pullets the effect of urea on laying performance has been assessed. Birds received one of three low‐protein rearing diets from 7–20 weeks of age. The control rearing diet, containing 11.5% crude protein, was compared with two diets containing 13.2% crude protein, one in which the protein was from conventional sources and the other containing 11.5% conventional protein and urea equivalent to 1.7% crude protein. At 20 weeks birds were allocated to one of two laying diets formulated to meet essential amino acid requirements. Half the birds from each rearing treatment received a low‐protein diet (14.7%) and the remaining birds received a 16.4% protein diet which included urea equivalent to 1.7% crude protein. Laying performance was recorded for the next 30 weeks.

Body weights of birds fed on the urea‐containing rearing diet were similar to those of birds fed on the control diet (1.22 kg) and less than those on the 13.2% protein diet (1.29 kg). Urea in the laying diet caused a 2% increase in egg production and tended to cause an improved food conversion efficiency. In contrast, a 3.5% less efficient food conversion was found during laying in birds which had received urea during rearing, compared with birds which had received the low‐protein rearing diet. Birds receiving the 13.2% protein diet, containing no urea, during rearing laid smaller eggs than birds fed on the 11.2% protein rearing diet. A high mortality rate occurred during laying due to lymphoid leucosis but no differences between treatments were found.     

Food intake and abdominal adipose tissue in White Leghorn hens fed diets of different protein and energy concentrations

1. Single Comb White Leghorn hens of 2 ages (44 and 80 weeks) were fed diets of different energy (10.88, 12.13 or 13.39 MJ ME and 140 g protein/kg) or protein (120, 140, 160 or 180 g and 12.13 MJ ME/kg) concentration over an 8-week period. 2. Food intake did not change with increasing concentrations of dietary protein. Protein intake was directly correlated with dietary protein concentration. 3. Energy intake increased with dietary energy concentration but, generally, failed to match the increases in dietary energy concentration. Energy, rather than protein, concentration was the major determinant of food intake. 4. Efficiency of energy utilisation decreased and mean adipocyte size increased with higher energy intake. 5. A bimodal adipocyte size distribution, consisting of a primary large size and a secondary small size population, was present in the abdominal fat pad of birds of both ages. There was no significant difference in the numbers of large adipocytes between the hens of the two ages. 6. The greater mean fat pad weight in the older hens was associated with increased mean cell volume in the population of large adipocytes.     

Tea polyphenols increase the antioxidant status of laying hens fed diets with different levels of ageing corn

This study was conducted to evaluate the effects of ageing corn levels (stored for 4 years) with or without the supplementation of tea polyphenols (TPP) on the performance, egg quality and antioxidant status of laying hens. A total of 288 Lohmann commercial laying hens (63-week-old) were used under a 2 × 4 factorial arrangement with 4 levels of dietary ageing corn (0%, 25%, 50%, or 100%) and 2 levels of TPP (0 and 600 mg/kg) for 8 wk. Dietary ageing corn linearly decreased (P < 0.05) the egg production, serum total antioxidant capacity (T-AOC), liver glutathione peroxidase (GSH-Px) of laying hens, yolk index, yolk colour, 1,1-diphenyl-2-picrylhydrazyl (DPPH) value and the reducing power value of egg yolk, but it linearly increased (P < 0.05) the feed conversion rate, ovary malondialdehyde (MDA) content of laying hens, and the protein carbonyl content of egg yolk. Tea polyphenol supplementation increased (P < 0.05) the serum T-AOC, serum superoxide dismutase (SOD), liver SOD, liver GSH-Px, ovary SOD, GSH-Px, the expression of antioxidant-related genes of laying hens, albumen height, Haugh unit, DPPH value and the majority free amino acids of egg yolk, but it decreased (P < 0.05) the serum MDA content of laying hens, MDA and protein carbonyl of egg yolk. In conclusion, the ageing corn significantly reduced the performance, egg quality, antioxidant status and egg antioxidant capacity of laying hens, while TPP supplementation partially counteracted the adverse effects, especially antioxidant status and egg antioxidant capacity of laying hens.     

Nutrient and energy retention in weaned Iberian piglets fed diets with different protein concentrations

Fifty-eight purebred castrated male Iberian (IB) piglets (initial BW 9.9 ± 0.1 kg) were used in an experiment to determine the effect of dietary protein content (PC) and feeding level (FL) on the rates of BW gain, whole body protein deposition (PD), and energy utilization between 10 and 25 kg of BW using the serial slaughter method. Treatments followed a 4 × 2 factorial arrangement with 4 PC (201, 176, 149, and 123 g of CP/kg of DM) and 2 FL (0.95 and 0.70 × ad libitum) and 6 or 7 piglets per combination of treatments. All diets were formulated to have an optimal AA pattern. Six piglets were slaughtered at the start of the trial to estimate initial body composition. The experimental pigs were individually housed in an environmentally controlled room (27 ± 2°C) until they reached 25 kg of BW, when they were slaughtered and analyzed for body composition. Positive linear effects of dietary PC on ADG, G:F, and gain:ME intake were observed (P < 0.001). Piglets fed at the highest FL showed greater ADG, G:F, and gain:ME intake (P < 0.001). An average increase was estimated to be 38.0 g of gain/MJ of ME intake. Protein deposition increased linearly from 35.6 to 50.9 g/d with increasing dietary PC (P < 0.001). A daily increase was estimated to be 0.35 g of PD/g of CP intake. Although the maximal genetic potential for PD of the IB piglet was not attained, a maximal value of 59.9 g/d for whole-body PD was achieved when the diet provided 201 g of CP/kg of DM and was fed at 0.95 × ad libitum. Piglets on the highest FL deposited on average 39% more body protein (P < 0.001) than restricted piglets. An average value of 4.39 g increase in PD/MJ of ME intake was obtained for diets containing 201 and 176 g of CP/kg of DM. Maintenance energy requirements and net efficiency of utilization of ME for growth, calculated by linear regression of ME intake on body retained energy, were 427 kJ/kg of BW(0.75)·d(-1) and 0.552, respectively. The corresponding partial efficiencies of utilization of ME for protein and fat deposition were 0.378 and 0.672, respectively, considerably less than the accepted values for conventional pig breeds. Practical diets of the young IB piglet should contain at least 201 g of ideal CP/kg of DM.     

Performance of laying hens fed on low sulphur amino acids diets supplemented with choline and methionine

1. Two experiments were carried out to examine the possibility of replacing a part of the methionine content with choline in a layers’ diet.

2. In the first a low methionine diet with 2.6 g methionine/kg was supplemented with 0.3, 0.6, 0.9 and 1.2 g DL‐methionine/kg. Choline at 1.12 g/kg was added to the diets, which contained 5.4, 6.0 and 6.6 g TSAA.

3. In the second diets with 3.02, 3.80, 4.53, 5.30, 6.04 and 6.51 g TSAA/kg were used and 0.94 g choline/kg was added to these diets.

4. Supplemental methionine increased egg production but not egg weight in the first experiment. When the low TSAA diet was supplemented with choline, egg output increased slightly but not significantly.

5. When supplemental methionine was added to the low protein and TSAA diets in experiment 2 it increased egg production and egg weight. Added choline did not increase egg production or egg weight, even with the diet very low in protein and TSAA. Body weight gain, food intake and feed conversion efficiency of food utilisation were improved by supplemental methionine but not choline.     

Productive and reproductive performance and egg quality of laying hens fed diets containing different levels of date pits with enzyme supplementations

Two experiments were conducted to investigate the effect of phytase and/or multienzymes (protease, amyloglucoidase, xylanase, B-glucanase, cellulose, and hemicellulase) on improving the utilization of date pit (DP) in laying hens. In the first one, DP completely replaced corn in four isocaloric and isonitrogenous diets: (1) DP50 without additives, (2) DP50?+?500 FTU phytase/kg, (3) DP50?+?0.1 % multienzymes, and (4) DP50?+?500 FTU phytase/kg?+?0.1 % multienzymes, in addition to the diet without DP. In the second experiment, DP was included at 0 %, 15 %, and 30 % in isocaloric and isonitrogenous diets. Meanwhile, diets containing 15 % and 30 % DP (DP15 and DP30) were fed without or with 500 FTU phytase/kg diet and/or 0.1 % multienzymes. In both experiments, each diet was fed to six groups of five hens housed individually (520 cm² per hen) during 30–42 and 28–42 weeks in the first and second experiment, respectively. In the first experiment, productive performance and shell quality of laying hens significantly decreased due to complete substitution of corn, but fertility and hatchability were not affected. Phytase, multienzymes supplementation did not restore laying performance to the control level. The results of experiment 2 indicated that DP could be included in laying hens diets up to 30 % when supplemented with multienzymes.     

The efficiency of energy retention of broiler chickens and turkeys fed on diets with different lysine concentrations

1.?An experiment determined the effect of 6 different lysine concentrations (40, 52, 58, 65, 90 and 130 g/kg CP) in two protein concentrations (210 and 260 g/kg) on the efficiency of energy utilisation of broiler chickens and turkeys. Ninety-six male Ross 308 broiler chicks and 96 male BUT Big 6 turkey poults were fed at 90% of ad libitum during a 12 d bioassay period. At the end of the bioassay, birds were slaughtered and carcase crude protein, fat and gross energy were measured and nutrient metabolisability determined.

2.?Broiler chickens had lower AME and AME_N than turkeys. AME was higher in the 260 g/kg than in the 210 g/kg protein diet; however, no difference was evident in AME_N between any of the diets in both species. A significant species × lysine interaction indicated that the decrease in AME and AME_N with increasing lysine was greater in turkeys than in broiler chickens.

3.?Turkeys had lower weight gains and efficiencies of energy retention than broiler chickens. The effects of different lysine concentrations on growth and the efficiency of energy retention were significant and growth responses were quadratic but there were negative linear responses in the efficiency of energy retention in both species at both crude protein concentrations. The efficiency of energy retention was increased with decreasing lysine concentrations throughout the wide range of concentrations used in the experiment.     

Plasma dispositions and concentrations of ivermectin in eggs following treatment of laying hens

AIMS: To determine the plasma disposition and concentrations of ivermectin (IVM) in eggs produced by laying hens following S/C, oral and I/V administration.

METHODS: Twenty-four laying hens, aged 37 weeks and weighing 1.73 (SD 0.12) kg were allocated to three groups of eight birds. The injectable formulation of IVM was administered either orally, S/C, or I/V, at a dose of 0.2?mg/kg liveweight, following dilution (1:5, v/v) with propylene glycol. Heparinised blood samples were collected at various times between 0.25 hours and 20 days after drug administration. Eggs produced by hens were also collected daily throughout the study period. Samples of plasma and homogenised egg were analysed using HPLC.

RESULTS: Maximum concentrations of IVM in plasma and mean residence time of IVM were lower after oral (10.2 (SD 7.2) ng/mL and 0.38 (SD 0.14) days, respectively) than after S/C (82.9 (SD 12.4) ng/mL and 1.05 (SD 0.24) days, respectively) administration (p<0.01). The time to maximum concentration and elimination half-life were shorter following oral (0.14 (SD 0.04) and 0.23 (SD 0.11) days, respectively) than S/C (0.25 (SD 0.00) and 1.45 (SD 0.45) days, respectively) administration (p<0.01). IVM was first detected in eggs 2 days after treatment in all groups and was detected until 8 days after oral and I/V administration, and until 15 days after S/C administration. Peak concentrations of IVM were 15.7, 23.3 and 1.9?µg/kg, observed 2, 5 and 4 days after I/V, S/C and oral administration, respectively.

CONCLUSIONS AND CLINICAL RELEVANCE: The low plasma bioavailability of IVM observed after oral administration in laying hens could result in lower efficacy or subtherapeutic plasma concentrations, which may promote the development of parasitic drug resistance. Due to high IVM residues in eggs compared to the maximum residue limits for other food-producing animal species, a withdrawal period should be necessary for eggs after IVM treatment in laying hens.     

Effects of milk thistle meal on performance,ileal bacterial enumeration,jejunal morphology and blood lipid peroxidation in laying hens fed diets with different levels of metabolizable energy

This study was conducted to evaluate the effects of different levels of milk thistle meal on performance, blood biochemical indices, ileal bacterial counts and intestinal histology in laying hens fed diets containing different levels of metabolizable energy. A total number of 200 Leghorn laying hens (Hy‐Line W‐36) were randomly assigned to eight experimental treatments with five cage replicates of five birds each. Dietary treatments consisted of four levels of milk thistle meal (0%, 15%, 30% and 60%) and two levels of AME_n (11.09 and 12.34 MJ/kg) fed over a period of 80 days. In vitro studies revealed that the total phenolic component of milk thistle meal was 470.64 mg gallic acid equivalent/g of the sample, and its antioxidant activity for inhibiting the 2‐2‐diphenyl‐1‐picrichydrazyl free radical and reducing ferric ions was about 21% higher than that of butylated hydroxyltoluene (p < .05). Diets containing high level of AME_n led to improved egg production (p < .05), egg weight (p < .05), egg mass (p < .01) and feed conversion ratio (p < .01). In addition, offering diets containing high energy significantly enhanced (p < .01) serum triglyceride and malondialdehyde (MDA) concentrations as well as jejunal villus height. Dietary supplementation of 3% milk thistle meal resulted in the best feed conversion ratio (p < .05), reduction of ileal Escherichia coli enumeration (p < .01) and an enhancement in the villus height‐to‐crypt depth ratio (p < .05). Furthermore, feeding incremental levels of this meal led to remarkable decrease in serum cholesterol, triglyceride and MDA (p < .01) concentrations while significant increase in blood high‐density lipoprotein content and goblet cell numbers (p < .05). The present findings indicate that milk thistle meal with high antioxidant and antibacterial properties in laying hen diets may improve health indices and productive performance.     

Seroprevalence of Histomonas meleagridis in pullets and laying hens determined by ELISA

Serum samples from 1120 layers from 56 flocks and 400 pullets from 20 flocks were tested by an indirect sandwich ELISA to investigate the prevalence of antibodies to Histomonas meleagridis in chickens kept in alternative husbandry systems. The overall prevalence of antibodies to H meleagridis in layers was 37.3 per cent, and positive birds were identified in 50 flocks. This was significantly higher than in pullets, where only 8.3 per cent of the birds tested positive. Optical density (OD) values obtained from pullet sera were much lower than the OD values from layers; however, positive birds were detected in half of the pullet flocks. In particular, all birds from an organic pullet flock were found to be positive, with high OD values. Overall, the highest prevalence of positive sera was obtained from birds kept in free-range flocks. Attempts to reisolate live histomonads from birds in 18 layer flocks were unsuccessful.     

Plasma aldosterone and electrolyte concentrations in exercising thoroughbred horses fed two diets in summer and winter

In a replicated 4 × 4 Latin square experiment conducted in summer, eight mature Thoroughbred horses received two diets, control and fat-supplemented, and were exercised at two fitness levels designed to increase daily digestible energy (DE) requirements to approximately 150% (fitness level I) and 200% (fitness level II) of maintenance. In a second experiment during the winter, horses received the two diets in a switchback design and exercised at fitness level II. After 3 wk adaptation to treatments, feed and fecal samples were collected and horses galloped a standardized exercise test (SET) designed to increase the heart rate above 185 bpm for 1200 m. Vital signs were monitored and blood samples were obtained. Feed intake increased as fitness level increased (P < .05). Horses on the fat-supplemented diet required less feed (P < .05) to meet the energy requirements at a given fitness level. Daily DE intake was higher (P < .05) for the horses exercised at fitness level II to meet the increased metabolic demands. Heart rate, respiration rate and rectal temperature all increased (P < .05) with exercise. No treatment effects were found for heart rate (P >. 10) or rectal temperature (P > .30). Horses exercised in the winter had lower (P < .05) respiration rates, indicative of less problems dissipating excess body heat. Plasma aldosterone concentrations increased (P < .05) with exercise, corresponding to an increase in plasma K concentrations. Horses exercised in the summer exhibited higher (P < .05) plasma aldosterone concentrations than horses worked in the winter. Plasma CI and Na concentrations did not change (P > .30) with any treatment or exercise, indicating that the horses were not sufficiently stressed to induce any significant dehydration.     

Nitrogen retention and performance of brown laying hens on diets with different protein content and constant concentration of amino acids and energy.

1. The aim of this study was to determine the nitrogen balance and the performance of laying hens fed on diets with a protein content lower than the diets currently used in commercial practice but with adequate concentrations of lysine, sulphur amino acids, tryptophan and threonine. 2. Ninety-six Hy-Line Brown hens, 24 weeks old, were divided into 3 groups of 8 replicates and received, for 16 weeks, diets formulated to have 3 different protein concentrations: 170 (control), 150 and 130 g/kg CP and the same energy content. For each protein concentration, the contents of lysine, methionine, methionine+cystine, tryptophan and threonine were maintained at minimum requirement concentrations by supplying synthetic amino acids. 3. In the first half of the trial, egg production and egg weight were similar in all groups. From the 9th week onwards group 150 CP laid heavier eggs and had a slightly lower egg deposition and total mass. Food conversion ratio was best in the control group. 4. Nitrogen intake was related to the protein concentration of the diet, the food intake being almost the same in the 3 experimental groups. Faecal nitrogen content significantly and linearly decreased with reduction in dietary protein content and was about 50% of the intake. Considering the nitrogen faecal/intake ratio, the 150 CP group showed better nitrogen utilisation at each sampling time.