Strains Of White Leghorn Hens Research Articles

Does age of hot-blade trimming impact the performance and welfare of 2 strains of White Leghorn hens?

The impact of mild hot-blade beak trimming on welfare and performance in 2 strains of White Leghorn pullets was examined. During the pullet phase, 960 pullets were designated to one of 4 trimming treatments: control (untrimmed, C), trimmed at a commercial hatchery (T0d), or trimmed on farm at 10 d (T10d) or 35 d (T35d) of age. During the hen phase, 720 of the original 960 hens were housed in conventional cages at 17 wk of age (6 replications per strain × treatment group) and data were analyzed as a 2 × 4 (performance and beak length data), 2 × 2 (behavior data, blocked by observer) factorial arrangement or a Chi-Squared analysis (beak healing). Total hen-day production tended to be lower for C birds, but hen-housed production did not differ. Feed intake was not affected by trimming treatments, but feed efficiency was poorer for C birds. Treatment did not statistically affect mortality. Cannibalism, although not significantly different among treatments, occurred in C birds only. The C pullets displayed more head/vent pecking, but no differences were noted in adult birds. There was no behavioral or histological evidence of chronic pain or neuroma formation, and healing occurred quicker when trimming occurred at zero or 10 d of age. To conclude, trimming mildly at zero, 10, or 35 d of age caused no long-term effect on welfare or performance, but trimming at younger ages resulted in faster healing.

Genetic variations alter production and behavioral responses following heat stress in 2 strains of laying hens

Genetic differences alter the type and degree of hens’ responses and their ability to adapt to a stressor. This study examined the effects of genotypic variations on the productivity and behavior of laying hens following heat stress (HS). Two strains of White Leghorn hens were used: DXL (Dekalb XL), a commercial strain individually selected for egg production and KGB (kind, gentle bird), a strain selected for high group productivity and survivability. Ninety hens (48 DXL and 42 KGB) at 28 wk of age were randomly assigned to either a hot (H: mean = 32.6°C) or control (C: mean = 24.3°C) treatment and housed in pairs by strain for 9 d. Egg production and quality, behavior, body and organ weights, and circulating hormone concentrations were measured. Heat-stressed hens had lower egg production [adjusted (adj) P < 0.001] than their respective controls. Among H-DXL hens, egg weight tended to be reduced at d 1 and was reduced at d 9 (adj P = 0.007), but was reduced only at d 9 among H-KGB hens (adj P = 0.007). Eggshell thickness was also reduced among H hens at d 9 (adj P = 0.007), especially among H-KGB hens (adj P = 0.01). Plasma triiodothyronine concentration was reduced among H-hens (adj P = 0.01), especially among H-DXL hens (adj P = 0.01). Neither temperature nor strain affected the plasma thyroxine and plasma and yolk corticosterone concentrations. Heat-stressed hens spent less time walking (adj P = 0.001) and more time drinking (adj P = 0.007) and resting (adj P = 0.001) than C-hens. The results indicate that although HS reduced production and caused behavioral changes among hens from both strains, the responses differed by genotype. The data provide evidence that genetic selection is a useful strategy for reducing HS response in laying hens. The results provide insights for conducting future studies to develop heat-resistant strains to improve hen well-being, especially under the current commercial conditions.

Effects of group size and repeated social disruption on the serotonergic and dopaminergic systems in two genetic lines of White Leghorn laying hens

Farm practices such as increasing group size (GS) and mixing unfamiliar chickens may result in repeated social disruption (RSD) and affect the well-being of hens. To examine whether there are genetic differences in response to social stress, 2 genetic strains of White Leghorn hens were used [i.e., high group production and survivability (HGPS) and DeKalb XL commercial strain (DXL). At 50 wk of age, social stress was created by increasing GS from 4 hens (control) to 8 hens (experimental) per cage and removing hens within the stressed groups to create 4 treatments (control-HGPS, control-DXL, GS/RSD-HGPS, and GS/RSD-DXL). For RSD, 2 hens per cage were moved weekly among the experimental cages within the same treatment. At 58 wk of age, blood sample and brain were collected from 1 hen per cage (n = 10 per treatment). Whole-blood tryptophan and serotonin (5-HT) and plasma norepinephrine (NE), epinephrine (EP), and dopamine (DA) were analyzed by HPLC. The raphe nuclei and the hypothalamus (HYP) were dissected and analyzed by HPLC for the central NE, EP, DA, dihydroxyphenylacetic acid (DOPAC), homovanillic acid, 5-hydroxyindoleacetic acid (5-HIAA), 5-HT, and the ratios of DOPAC:DA and 5-HIAA:5-HT. There were no line differences in the concentrations of peripheral tryptophan, 5-HT, EP, NE, and DA in response to GS-RSD (P > 0.10). However, neuronal transmitters were regulated differently in the different central nuclei between the lines. In the raphe nuclei, control-HGPS tended to have a higher 5-HIAA:5-HT ratio than the control-DXL (P = 0.09). Concentrations of EP were increased in the DXL hens (P < 0.01), whereas the HGPS hens had decreased levels of DOPAC (P < 0.05) and DA turnover (DOPAC:DA, P < 0.01) post GS-RSD. In the HYP, compared with relative controls, there were no significant differences in the concentrations of 5-HT, whereas the levels of 5-HIAA were reduced (P < 0.01) after GS-RSD, suggesting that GS-RSD led to a lower 5-HT turnover in the HYP. The results indicate that selection for docility and productivity alters serotonergic and catecholamine homeostasis in hens in response to social stress, GS-RSD.

Group Size and Density Effects on Physical Indices and Cell-Mediated Immunity in Two Genetic Lines of White Leghorn Layers

Social stress resulting from varied group sizes with density in caging systems is a common problem that affects bird welfare in the poultry industry in the United States. To examine whether there is a genetic basis for variations in response to group size and density, 2 genetic strains of White Leghorn hens were used in this study: HGPS, a line selected for high group productivity and survivability in multiple-bird cages and DXL (Dekalb XL), a commercial line individually selected for production. Birds from each line were housed in either 4-bird cages (542 cm(2)/bird) or 10-bird cages (434 cm(2)/bird) from 17 to 60 wk of age. Blood samples, BW, and adrenal weight were collected from the birds at 30, 45, and 60 wk of age (n = 12, respectively) after euthanasia. Subsets of T cells (CD4(+) and CD8(+)) were measured by flow cytometry. Hematological parameters were collected from blood smears. Results showed that there were no significant differences for BW, the relative adrenal glands, and the heterophil:lymphocyte ratio between and across lines after the treatments (P > 0.05, respectively). Compared with DXL birds, the HGPS birds had a greater ratio of CD4(+):CD8(+) at 30 and 45 wk of age. There was an age-associated decrease in CD4(+) cells in all groups from 45 to 60 wk of age. However, an age-related decrease in CD8(+) cells from 45 to 60 wk was found in the DXL birds only. The unique changes in T-cell subpopulations and the ratio of CD4(+):CD8(+) may suggest that HGPS birds had a greater cell-mediated immunity than DXL birds. The genetic basis of variations in immunity may correlate with the line-unique ability of birds to cope in social environments and their survivability.

Effects of Social Disruption on Physical Parameters, Corticosterone Concentrations, and Immune System in Two Genetic Lines of White Leghorn Layers

Farm management practices such as increasing group size and mixing of unfamiliar chickens may cause social disruption and affect bird well-being. To examine genetic-associated physical and physiological differences in response to social disruption, 2 strains of White Leghorn hens were used in the study [i.e., HGPS (line selected for high group production and survivability) and DXL (DeKalb XL commercial line)]. Social disruption was created when hens were 50 wk of age by increasing group size from 4 hens (control) to 8 hens (experimental) per cage and providing an unstable social environment by moving 2 hens weekly between cages within the same line (experimental hens only). At 58 wk of age, hens were feather-scored. After euthanization, BW and the right adrenal gland weight were collected (n = 10 per treatment). Adrenal gland weight was adjusted for BW, and adjusted adrenal weight was used for analysis. Plasma corticosterone was quantified using RIA. The T-lymphocytes (CD4+ and CD8+) were measured using flow cytometry. Results showed that average feather cover score was greater for DXL hens than HGPS hens in both the unstressed (P < 0.05) and stressed treatment (P < 0.01). There was no difference in BW in DXL and HGPS hens between the control and the social disruption treatments. However, the relative adrenal weight of HGPS hens tended to be lower than control hens after social disruption (0.05 >P < 0.10). Plasma corticosterone was significantly lower in both strains following social disruption (P < 0.01). The T-lymphocyte ratio (CD4+:CD8+) was greater in HGPS hens than DXL hens post social disruption (P < 0.05). The data indicate that the 2 strains of hens reacted differently in terms of the adrenal system and immunity in response to social disruption. Hens selected for longevity with docile behaviors and high productivity, such as HGPS hens, provide a useful tool for improving animal well-being.

Evaluation of Resistance of Four Strains of Commercial Laying Hens to Experimental Infection with Salmonella enteritidis Phage Type Eight

Four different strains of White Leghorn hens were orally infected with 1 × 108 cfu of Salmonella enteritidis phage Type 8 per bird. The birds were monitored for 10 wk postinfection for colonization of internal organs, fecal shedding of S. enteritidis, and the production of S. enteritidis- contaminated eggs. There was no difference among the four hen strains in regards to the probability of S. enteritidis isolation from liver and spleen, ovary, and cecal tissue within the first 30 d postinfection. However, during the first 14 d postinfection, S. enteritidis organisms were isolated in significantly higher rates from eggs and fecal samples of Strain A than from samples obtained from the other three hen strains. Results suggest that there may be inherent differences between strains of laying hens with regard to their response to infection with S. enteritidis.

Effect of beta-naphthoflavone on o-tolyl saligenin phosphate-induced delayed neuropathy in two lines of chickens.

The effect of the microsomal enzyme inducer beta-naphthoflavone (beta NF) on the development of organophosphorus-induced delayed neuropathy (OPIDN) was examined in two laboratories (VPI and MSU), utilizing two strains of White Leghorn hens. A single intraperitoneal injection of beta NF at 80 mg/kg body weight 48 h prior to administration of o-tolyl saligenin phosphate (TSP), the neuroactive metabolite of tri-o-tolyl phosphate (TOTP), caused a significant increase in hepatic microsomal cytochrome P-450 concentrations and aniline hydroxylase activities after 72 h in both strains. Hepatic carboxylesterase and cholinesterase activities were not affected by beta NF treatment in either strain. Administration of TSP in single subcutaneous doses of 20 and 25 mg/kg body weight (VPI) or 30 and 60 mg/kg body weight (MSU) caused significant inhibition of whole-brain neuropathy target esterase (NTE) activity 24 h postdosing, and hens subsequently developed clinical signs characteristics of OPIDN. beta NF had no significant effect on NTE inhibition or on initiation or severity of OPIDN clinical signs. However, OPIDN clinical signs were less severe in the strain of bird (MSU) with the higher intrinsic hepatic carboxylesterase activity and the higher beta NF-induced cytochrome P-450 concentration. The study indicates that microsomal enzyme induction, which has been shown to alleviate TOTP-induced delayed neuropathy, could not alleviate OPIDN resulting from exposure to TSP. This study also suggests that strain may affect susceptibility to TSP-induced delayed neuropathy.

Research Note: Effect of Preincubation Storage of Hatching Eggs on Subsequent Performance of White Leghorn Hens

Eggs from three strains of White Leghorn hens were stored up to 21 days prior to incubation in 1964 and 1965. Eggs stored longer than 7 days were packaged in Cryovac2 bags with the air evacuated (1964) or flushed with nitrogen (1965) and held at about 12 C and 80% relative humidity. Each year, all eggs were set together and incubated at 37.5 C (29.5 C wet bulb). At 18 days of incubation, eggs were candled, apparently infertile eggs removed, and incubation continued at 37.0 C (32.5 C wet bulb). Hens were housed at 147 days in floor pens in 1964 and in individual cages (20 × 41 cm) in 1965.Preincubation storage reduced hatchability of apparently fertile eggs. Preincubation storage affected only housing body weight (1964), egg weight (1964, 1965), Haugh units (1964, 1965), and blood spots (1965). Effects of preincubation storage of hatching eggs on hens’ subsequent performance do not appear important enough to offset the advantage of storing hatching eggs for up to 3 weeks in experiments and breeding programs where it is advantageous to reduce hatch effects or to offset the management advantages of fewer hatches.

Egg Quality. 2. Albumen Quality of Eggs from Five Commercial Strains of White Leghorn Hens During One Year of Lay

Egg weight and albumen height of a sample of 160 eggs from each of five commercial strains of White Leghorn hens were measured at each of 18 sampling times between 197 and 484 days of age for a total of 14,400 eggs. Age (P<.01) and strain (P<.05) were the main factors affecting interior egg quality. Both albumen height and Haugh units decreased at an approximately constant rate over time. An electronic albumen meter was used to measure albumen height. The tip of the measuring rod had to be kept free of dried albumen to prevent measurement errors.

Egg Quality. 1. Shell Strength of Eggs from Five Commercial Strains of White Leghorn Hens During Their First Laying Cycle

Eggs were collected 18 times from five strains of commercial White Leghorn hens between 197 and 484 days of age. Egg weight, specific gravity, nondestructive deformation, and quasistatic compression breaking strength were measured on all eggs. Shell weight, percent shell, and shell weight per unit surface area were available for eggs collected between 372 and 484 days of age. Shell thickness was measured at 421, 449, and 477 days of age. Age and strain (P<.01) influenced all the variables except shell thickness, which was affected only by strain (P<.05). Egg weight and deformation increased and specific gravity and compression breaking strength decreased over the experimental period. Shell weight, percent shell, and shell weight per unit surface area decreased slightly between 372 and 484 days. The variability, expressed as the standard deviation of an observation, remained relatively constant for specific gravity, egg weight, shell weight, percent shell, and shell weight per unit surface area. It increased for deformation between 197 and 484 days. The variability of compression breaking strength was not constant over the experimental period, but neither did it exhibit any simple trend. There were few interactions: strains of hens which had the highest shell quality at 197 days also had the highest at 484 days.

The Performance of Laying Hens as Affected by Copper Sulfate and Methionine Level

Two strains of White Leghorn hens were subjected to seven copper treatments that included a negative control for the first week of each of five 28-day periods. The hens were approximately 500 days of age when the experiment began. Copper treatments were assigned to simulate the different levels of copper intake that might result from differences in daily feed intake similar to the practice followed with commercial industry. In order to simulate daily dietary intake ranging from a low of 73 to a high of 136 g per bird, levels of 76, 91, 100, 114, 129, and 143 mg of copper sulfate per kilogram were added to each of the basal diets. Treatments were administered across two methionine levels in a corn-soy basal diet.Hen-day egg production, egg weight, daily feed intake, and feed efficiency values were not affected by dietary levels of copper or methionine. Hens fed diets containing low methionine laid eggs with significantly poorer specific gravity.

Observation of Spurs in Four Strains of White Leghorn Hens as Affected by Season of Maturity and Dietary Nutrient Level

Four strains of White Leghorn hens were observed for the incidence of spurs at two intervals during two laying trials. One trial began in the fall and the other in the spring. The hens in both trials were subjected to six dietary nutrient density treatments.Little seasonal or dietary effect was noted, even though the incidence of spurs increased with age in all strains. There was a highly significant difference in spur numbers due to strain. Shorter spurs were much more numerous than longer spurs at all sample times. The incidence of longer spurs increased with the age of hen at time of measurement.

The Effects of Phased Feeding Protein and Calcium on Egg Weight and Shell Quality with Four Strains of White Leghorn Hens

The effects of phasing dietary protein and calcium levels on egg weight and shell quality were studied using 1200 White Leghorn hens of four strains housed in group cages. Hens fed diets decreasing in protein by 1% while increasing in calcium by .5% at 12-week intervals had a greater early egg weight combined with a significantly slower rate of increase in egg weight with age than those from the control hens fed a diet with the average protein and calcium contents of the phased diets. Average egg weights for the 48-week trial were identical for both treatments. Shell quality, as measured by shell weight per unit of surface area of the egg (SWUSA), was significantly affected by the calcium level fed. When the dietary calcium level was phased upward, the rate of decline in shell quality, with increasing age of the hen, was significantly slower than with the control diet.Egg production, mortality, and the percentage of uncollectible eggs were not affected by dietary treatment Feed efficiency, as measured by the metabolizable calories required per unit of egg mass, was significantly poorer for the hens fed the phased protein diets than for those fed the diets phased in both protein and calcium.The strain of hen had significant effects on egg production, feed efficiency, egg weight, shell quality, and mortality but not on uncollectible eggs. One of the two midget strains, although housed at 14% greater bird density, had 5 and 10% improved feed efficiency, 2% lower and 1% greater egg weight, and shell quality 6% higher and equal to the two standard-sized strains, respectively, while matching them in egg production. Performance of one midget strain was not up to the overall standard exhibited by the standard-sized birds nor the other midget strain.

Lack of a relationship between concentrations of plasma Luteinising hormone, Thyroxine and Prolactin at nine weeks of age and subsequent egg production in the domestic hen

1. The concentrations of plasma luteinising hormone (LH), thyroxine and prolactin were measured in about 200 birds from each of two homogenous strains of White Leghorn hens at 9 weeks of age and related to subsequent egg production. 2. Within each strain, no relationships were found in individual birds between the concentrations of the plasma hormones and subsequent egg production after 90, 180 and 270 d of laying. 3. Single measurements of plasma LH, thyroxine or prolactin before the onset of lay do not appear to be useful criteria for the selection of egg-laying strains.

Effects of Sodium Plus Potassium to Chloride Ratio in Practical-Type Diets on Blood Gas Levels in Three Strains of White Leghorn Hens and the Relationship Between Acid-Base Balance and Egg Shell Strength ,

A 3 × 6 factorial experiment involving three strains of Single Comb White Leghorn hens and six dietary ratios of sodium plus potassium to chloride ((Na + K)/C1) of .40, .91, 1.92, 2.83, 4.04, and 7.69 was done with 108 individually caged hens. The six corn-soybean meal-brewers’ dried grains diets included comparisons among low and high levels of sodium and chloride. Feed and distilled water were provided ad libitum from 403 to 487 days of age. Egg and shell measurements were taken on eggs laid between 479 and 483 days. At the completion of the experiment, blood pH and gases (pCO2, pO2) and plasma Na, K, Cl, Ca, P, and Mg were measured for each hen. Blood bicarbonate was calculated from the pH and pCO2 values. Much of the variation in blood gas levels and 485-day body weight could be attributed to the effects of the .40 diet. The effects of dietary sodium and chloride levels appeared independent of each other with decreasing levels of sodium and increasing levels of chloride reducing blood pH, pCO2, and bicarbonate; these ions had the reverse effect on plasma K. Significant differences in feed intake, feed efficiency, and egg production were apparently due to extremely poor performance of birds fed the .40 diet. Differences among strains were significant for feed intake, productivity, egg and shell weight, percent shell, shell weight per unit surface area, and egg specific gravity but were not significant for blood gas and plasma inorganic ion levels, nondestructive deformation, compression fracture force, and interior quality. Increasing dietary chloride levels significantly reduced deformation and fracture force. There were few dietary (Na + K)/Cl ratio × strain interactions. Partial correlation coefficients indicated very weak relationships (r = −.19 to .14) between blood pH or bicarbonate and specific gravity, deformation, or fracture force. The results of this experiment indicate that although the acid-base balance of laying hens was influenced by the (Na + K)/Cl ratio of the diet, there was no relationship between acid-base balance and egg shell strength.

The Effects of Dietary Protein Level on Productive Performance and Egg Quality of Four Strains of White Leghorn Hens

The effects of a mid-laying period reduction in dietary protein level on productive performance was studied with 576 individually caged Single Comb White Leghorn hens from four strains. The hens on treatments 1 and 2 received diets that contained by calculation 17 and 15% protein, respectively, between 143 and 507 days of age, while those on treatment 3 received 17 and 13% protein diets from 143 to 325 and 326 and 507 days, respectively. For treatment 4, diets containing 15 and 13% protein were given during the same periods as for treatment 3. Egg quality measurements were taken on eggs laid over 5-day intervals when the birds were 182, 252, 316, 380, 436, and 485 days of age. Dietary protein level had no significant effects on feed intake, mortality, body weight, egg production, egg grade, specific gravity, egg weight, Haugh units, or blood spots. Protein intake had no effect on the 507-day body weights and on hen-day egg production, except for a small decrease for treatment 4, although the intakes of protein, leucine, and lysine were lower for treatments 3 and 4 between 326 and 507 days of age than the NRC requirements. Level of dietary protein had no effect on kg feed/dozen eggs but had a significant (P<.01) effect on kg feed/kg eggs. Strain of bird had a significant effect on body weight, egg production, specific gravity, egg weight, Haugh units, and blood spots at 485 days. There were no significant protein level × strain interactions.