Control Flock Research Articles

Matched concurrent case-control study of risk factors for feather pecking in hens on free-range commercial farms in the UK

1. The aim of the study was to compare the management and husbandry of free-range flocks in the UK where feather pecking was either present (case) or absent (control). 2. One hundred flocks were enrolled into a concurrent case-control study: 50 where birds had recently started feather pecking, and 50 matched control flocks where birds of the same age had not started feather pecking. 3. Information was obtained from a detailed interview with the flock manager, and by direct inspection of the flock, house and range. 4. Initial univariate analyses revealed that case flocks were more likely to comprise ISA Brown than Lohmann, were more likely to be restricted from litter areas to prevent floor eggs, and were less likely to use the outside range. 5. Cluster analysis indicated that feather pecking was not associated with any particular husbandry system. 6. The only influential risk factor significant in the multivariable conditional logistic regression analysis was use of the outdoor range. The risk of feather pecking was reduced 9-fold in flocks where more than 20% of birds used the range on sunny days (odds ratio = 0·12). Use of the range was positively associated with the presence of trees and/or hedges on the range.

Cannibalistic behaviour spread by social learning

We hypothesized that social learning is involved in the spread of cannibalism in domestic fowlGallus gallus domesticus . To investigate this hypothesis without harming birds, we used an inanimate chicken model as our cannibalism stimulus. We randomly assigned flocks of 12 White Leghorn pullets to one of two treatments: (1) flocks with two trained demonstrators (N=9) and (2) control flocks (N=8). Demonstrators were trained to pierce a membrane covering a dish of chicken blood and consume the blood. To assess the effect of access to the cannibalism stimulus during demonstrations, we randomly assigned observer pairs to one of two observer treatments: (1) observe stimulus through a wire mesh partition and (2) observe stimulus within the same enclosure. We conducted five 10-min demonstration sessions, each followed by a 10-min test of each observer pair in the absence of demonstrators, over a period of 15 days when the birds were 41–55 days of age, and two further tests at 63–64 and 91–92 days of age. Pairs that observed demonstrators piercing a membrane and consuming blood were more likely to perform this task when tested than control pairs. Learning of the task was enhanced by direct access to the cannibalism stimulus rather than observing it through a wire mesh partition. Blood consumption during tests was increased by direct access to the cannibalism stimulus during demonstration sessions. The birds made bigger holes in the membrane when tested after observing trained demonstrators and after having direct access to the stimulus. Our results provide the first experimental evidence that social learning can contribute to the spread of cannibalistic behaviour in domestic fowl. We suggest that stimulus enhancement and observational conditioning were the social-learning mechanisms involved. Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.

Hsp60 specific antibodies in egg yolks from laying hens naturally infected with Salmonella enterica subspecies enterica serovar Enteritidis

Heat shock protein (Hsp) 60 of Salmonella appears to be involved in pathogenesis of infectious processes and host immune responses. Eggs of laying hens from two Salmonella Enteritidis naturally infected flocks (I—acute outbreak of infection; II—occasional bacteria excretion) and one control flock (III) were tested for the presence of yolk antibodies (IgY) against Hsp60 by applying enzyme-linked immunosorbent assay (ELISA). The levels of specific immunoglobulins were related to those against lipopolysaccharide (LPS) and flagellin, the antigens of the established immunological importance in S. Enteritidis infections. Within flock III, the antibody concentrations were consistently low. Elevated levels were detected in eggs from two infected flocks. Levels of specific IgY measured for flock I were higher than those in flock II; the greatest difference was observed for anti-Hsp60. This report indicates a probable important role of Hsp60 as a target of the hens' immune response, especially during the acute phase of S. Enteritidis infection.

Risk factors associated with the introduction of acute clinical infectious bursal disease among Danish broiler chickens in 1998

The objective of the present study was to investigate risk factors associated with the introduction of acute clinical infectious bursal disease (IBD) among Danish broiler chickens in 1998. Data on 218 flocks were collected from hatcheries, abattoirs, farmers and veterinarians; 49 of the flocks had experienced acute clinical IBD (cases), 169 were unexposed (controls). The study was carried out using a case-control design. Cases were defined as the first flock on each premises to experience acute clinical IBD, and these were compared with non-diseased, non-IBD-vaccinated control flocks chosen randomly from each unaffected farm. The resulting numbers of cases and controls used for statistical analyses were 16 and 61, respectively. Statistically significant associations were seen between the initial 16 Danish cases of acute clinical IBD in 1998 and certain hatcheries, age of parent birds and a certain feed mill.

Effectiveness of an Undefined Mucosal Competitive Exclusion Treatment to Control Salmonella in Turkeys During Brooding

Mucosal competitive exclusion (MCE) cultures generated from the mucosal scrapings of healthy adult turkeys were administered to commercial turkey poults. MCE-treated poults were placed on tom and hen farms with paired untreated control poults in adjacent houses. After 6 wk in the brood house, cecal droppings from control and treated flocks were collected and analyzed for the presence of salmonellae. Salmonellae were detected in 14 of 30 cecal droppings (47%) from control flocks and from only 1 of 30 (3.3%) droppings from the treated poults. This study demonstrated that mucosal competitive exclusion could be used to effectively control salmonellae in a commercial field trial of young turkey flocks.

Reduction of horizontal transmission of avian leukosis virus subgroup J in broiler breeder chickens hatched and reared in small groups

Transmission of avian leukosis virus, subgroup J (ALV-J), from donor chickens inoculated as embryos to simulate congenital infection to uninfected hatchmates was studied in two strains of commercial broiler breeder chickens. Chicks of two commercial lines free of ALV-J became infected when hatched (1/2 lots positive) or reared (8/8 lots positive) in direct physical contact with ALV-J-infected donors. Infection also occurred when chicks were exposed in the hatchery to ALV-J-infected donors by cloacal swab transfer (2/2 lots positive), needle transfer during subcutaneous inoculation (2/2 lots positive), or ingestion of infected meconium (2/2 lots positive). However, transmission was delayed or prevented by wire partitions in the hatcher and rearing of small groups in cubicles, and rarely (1/10 lots positive) resulted from short-term direct or indirect contact. In a simulated field test, a flock of 503 broiler breeder chickens with an initial embryo infection rate of 4.6% was hatched and reared as 48 small groups to 4 weeks of age. Groups were tested at hatch and at 3 weeks, and 14 infected groups were eliminated. This flock tested negative for ALV-J infection from 4 to 32 weeks and did not transmit infection to progeny or develop tumours. A control group of 377 chickens with a similar initial infection rate was hatched and reared as a single group. This control flock transmitted virus to 5.7% of its progeny and about 5% of the hens developed tumours. The small-group hatching and rearing practices employed in these studies allowed for the accurate identification and removal of groups containing chickens infected prior to hatching and prevented horizontal transmission of ALV-J between uninfected and infected groups for at least 4 weeks. More importantly, application of these procedures successfully eradicated ALV-J in a single generation under laboratory conditions. This suggests that similar procedures could be a valuable adjunct to virus eradication programmes in the field.

Selection for ultrafine Merino sheep in New Zealand: heritability, phenotypic and genetic correlations of live weight, fleece weight and wool characteristics in yearlings

AbstractMerino yearling records from 1988 to 1992 birth years in ultrafine wool selection and random control flocks at Tara Hills High Country Station, New Zealand were analysed for live weight, fleece weight and wool characteristics. Estimates of heritability, genetic and phenotypic correlations among traits using REML methods are presented. Heritabilities (h2) of birth, weaning, autumn, spring and summer live weights and greasy and clean fleece weights were estimated as being 0·35, 0·34, 0·44, 0·43, 0·49, 0·24 and 0·28 respectively; while h2 of yield, fibre diameter, coefficient of variation in fibre diameter, staple crimp, staple length, staple strength, position of break, resistance to compression, bulk, CIE Y and CIE Y-Z were estimated to be 0·58, 0·59, 0·60, 0·45, 0·71, 0·13, 0·18, 0·46, 0·38, 0·38 and 0·42 respectively. Genetic correlations were found to be high among the live weights but low to moderate among fleece weight and wool characteristics. Heritability estimates of fibre diameter, fibre diameter variation and staple length were found to be higher in New Zealand fine wool Merinos than most of those reported in the literature. The results indicate that selection for reduced fibre diameter will have little effect on other major production traits such as live weight and fleece weight.

Assessing the efficiency of mating in broiler breeder flocks by enumerating the spermatozoa which penetrate the inner perivitelline layer over the germinal disc

1. The frequency distribution of points of hydrolysis produced by spermatozoa in the perivitelline layer from directly over the germinal disc was examined in 60 samples of 60 eggs from commercial broiler breeder flocks. 2. Typically, these distributions were positively skewed, although log transformation of the data revealed 2 populations: one representing eggs which contained no evidence of spermatozoa and another in which the data were, generally, normally distributed. 3. Problem flocks with low fertility had more eggs without evidence of spermatozoa and, compared to control flocks with acceptable fertility, a lower median and mean before and after log transformation, respectively. 4. In 4 flocks studied between 30 to 55 weeks of age, the median number of points-of-hydrolysis in samples of eggs fell from around 200 at peak to less that 20 at 55 weeks, whilst the mean proportion of fertile eggs laid by the whole flocks fell from 94% at peak to around 79% at 55 weeks. 5. A log-linear relationship was demonstrated between flock fertility and the median points-of-hydrolysis from the inner perivitelline layer over the germinal disc in samples of 60 eggs (R 2=0·79). 6. The main advantages of this system for measuring sperm-in-eggs are that it is technically simple and presents a more expanded scale than fertility, so that an estimation of whole flock fertility can be derived from a sample of 60 eggs.

Economics of prophylaxis against peste des petits ruminants and gastrointestinal helminthosis in small ruminants in north Cameroon.

Data on reproduction and mortality were collected over one year from 5100 sheep and 13,300 goats in treated and control flocks. The treated animals received vaccination against peste des petits ruminants (PPR) and anthelmintics twice a year. Productivity parameters (fecundity and mortality rates) obtained with and without prophylaxis were fitted into a benefit-cost economic analysis model and run for project lifespans varying from one to five years. At a 7% discount rate, the overall benefits for a project lifespan of five years were estimated as over 15 million FCFA and 11 million FCFA for sheep and goats, respectively. The benefit-cost ratio ranged from 2.26 to 3.27 in goats and 3.01 to 4.23 in sheep, depending on the project lifespan. It was concluded that PPR and gastrointestinal helminthosis are important causes of economic losses in small ruminants in Cameroon. A national or even a regional vaccination campaign against PPR and strategic anthelmintic treatment of small ruminants are recommended.

Correlated responses to selection for or against facial eczema susceptibility in Romney sheep in New Zealand

Genetic selection for or against susceptibility to facial eczema (FE) in Romney sheep began in 1975, with the establishment of a resistant (R) selection flock, a susceptible (S) selection flock, and later (in 1982) a control (C) flock. For all but the initial years, rams were identified by performance testing with a sporidesmin challenge, then ranked on relative elevation of the liver enzyme, gamma glutamyltransferase (GGT), measured in serum. A different dose rate of sporidesmin was used for performance testing in the R and the S flocks, with a balanced half of the C‐flock animals being tested at each dose rate. Results are reported here up to the 1997‐born lamb crop. Mixed‐model animal‐model methods were used to determine the direct responses to selection, expressing results as breeding values for loge GGT. Correlated responses were monitored in lambs for weights, fleece weight, and survival, and in ewes for reproductive traits. Up to 1997, a 9‐fold difference in GGT concentration, 3 weeks after challenge, was achieved between the R and S lines. Selection line differences in correlated traits were significant (P < 0.01) for weaning and January weights (with the R line 5–6% lighter than the S line), whilst the R line yearlings produced 8% heavier fleeces (P < 0.05). Ewe reproductive differences among lines were small, and nonsignificant for the overall trait (numbers of lambs weaned per ewe mated), but there were significant ram differences in fertility among lines, with highest fertility in the R line. Using a multi‐variate restricted maximum likelihood analysis, genetic correlations of lamb production traits with loge GGT were consistent in sign with the selection‐line responses, i.e., for animals which were more resistant (with lower GGT), both weaning and autumn weights decreased slightly, and both yearling weight and fleece weight increased slightly.

Response to selection for ultrafine Merino sheep in New Zealand: I. Wool production and wool characteristics of ultrafine fibre diameter selected and control Merino yearlings

Merino ewes were screened for low fibre diameter from 15 000 yearlings within 12 flocks to establish a foundation flock in 1987, which was expanded to 500 ewes over the subsequent two years. Ewes were selected on fibre diameter BLUP breeding values. For comparison, a control flock of 100 ewes was randomly selected from the same sources. Data from approximately 2000 progeny over five birth years within 70 sire groups were analysed. Traits measured were live weight, greasy and clean fleece weight, yield, mean fibre diameter (FD), staple length, staple strength, staple crimp frequency, resistance to compression, Commission International de l'Eclairange (CIE) tristimulus value for scoured wool and coefficient of variation in fibre diameter. The ultrafine progeny had 2-μm finer FD, 0.6 units less yellow and had 0.6 more crimps/cm (all P<0.001) than their control counterparts. This experiment suggests that formation of an open nucleus breeding population by intensive screening for fibre diameter from a commercial population will improve selection response relative to traditional within flock selection without screening or to screening rams only.

The use of competitive exclusion in broilers to reduce the level of Salmonella contamination on the farm and at the processing plant

The effect of a competitive exclusion (CE) product, Broilact, on Salmonella contamination of broiler chickens was studied on the farm and at the processing plant. In the first part of the study, two flocks per week, a CE-treated and an untreated control flock, were placed in similar broiler houses. The CE treatment was administered in the hatchery using a modified spray vaccination cabinet. Salmonella was analyzed from the paper pads of the transport boxes on arrival at the farm and from fecal samples taken 2 wk before slaughter. The results of Salmonella sampling were received for 67 flocks. The other 141 flocks of the company that were reared during the trial period were also sampled for Salmonella and the results were compared to those of treatment and control groups. Broiler performance, including mortality, weight, and feed conversion, was recorded for the trial flocks. In the second part of the study, Salmonella contamination of neck skin samples taken at the processing plant from 18 CE-treated and 28 control flocks was compared. The Broilact-treatment significantly reduced Salmonella contamination both on the farm and at the processing plant. At the level of the farm, the percentage of Salmonella-positive flocks was essentially the same in the control flocks and in other flocks reared during the trial period. An improvement in broiler performance was indicated, although the difference was not significant.

Selection for high or low backfat depth in Coopworth sheep: juvenile traits

AbstractA selection experiment was established in Coopworth sheep in 1981 to breed for increased or reduced ultrasonic backfat depth (scan C). Foundation females came from four flocks recorded for scan C and live weight, with weight-adjusted scan C data within flock being used for initial screening and subsequent selection. Three groups of animals per source flock, comprising proportionally the fattest 0·12, a random sample, and the leanest 0·12, were used to establish the F, control and L lines, respectively. Ewe flock numbers from 1981 to 1992 averaged 51 per line. Foundation rams were selected in the same manner from four different farms (two sources each in 1981 and 1982) to provide F line (proportionally the fattest 0·04), control line and L line (leanest 0·04) rams for use in 1981 and 1982, with four mated per line per year. Thereafter homebred rams were selected, with 41 or 42 homebred rams being used per line until 1992. Average generation intervals were 2·13 years and annual inbreeding rates per line 0·004. Bivariate heritability estimates for log scan C and log live weight, and a univariate estimate for log scan C using restricted maximum likelihood with an animal model, were 0·28, 0·22 and 0·38, respectively (all with s.e. 0·03). There was a suggestion of lower heritabilities in the L line for log scan C after adjustment for live weight. Realized heritabilities in the F and L lines were 0·34 (s.e. 0·07) and 0·26 (s.e. 0·03), respectively. Deviations of back-transformed weight-adjusted scan C in the last 2 years ofF and L data analysed (1991 and 1992 birth years) from the control flocks were 2·08 and −0·85 mm, which corresponded to responses of +2·50 and −1·03 phenotypic standard deviations, respectively. In addition there were relatively large responses in live weight taken at scanning, with F and L lines averaging 34·0 and 40·2 kg, compared with 38·0 kg for controls in the 1991 and 1992 birth years. The genetic and phenotypic correlations between log scan C and log live weight at scanning were 0·16 (s.e. 0·07) and 0·46 (s.e. 0·01) respectively.

Response to selection for fertility in a fall-lambing sheep flock.

Selection for fertility in a fall lambing system was applied for 5 yr (1.45 generations) in a crossbred sheep population. Three flocks were involved: a fall-lambing selected (S) flock of 125 ewes and 10 rams, a fall-lambing environmental control (EC) flock of 55 ewes and five rams, and a spring-lambing genetic control flock of 45 ewes and five rams used to produce replacements for EC. Estimated breeding values for fertility (ewes lambing per ewe exposed) were calculated for animals mated in each year of the study using a single-trait animal model and increased more rapidly in S (.0138/yr) than in EC (.0067/yr). After accounting for genetic drift, EBV of ewes mated in S in the final year of the study averaged .070 +/- .032 (P = .08). A correlated response of .0087 lambs/yr was observed in S for fall litter size Genetic trends in all body weights were positive in EC, likely because of supplemental selection on body size in ram lambs used in EC. Ninety-day weight, maternal effects on weaning weight, and 90-d scrotal circumference increased in S, but direct effects on birth and weaning weights declined. In order to focus on realized selection response in fertility, EBV for fertility of 330 replacement ewe lambs from S and EC were calculated using only data collected after their birth. These realized EBV were then regressed on pedigree EBV calculated at the time the ewe lambs were born. The regression was significant when all relationships were used to calculate both EBV (.20 +/- .08) but only approached significance (.13 +/- .07) when only records of the ewe lambs themselves, their descendants, and their paternal half-sibs were used to calculate realized EBV. Also, EBV for all ewes were calculated at the start of each breeding season and were higher (P < .01) for ewes that subsequently lambed than for open ewes. These results suggest that selection can be used to improve fertility in fall-lambing sheep flocks.

The Effect of Lactobacillus acidophilus on the Production and Chemical Composition of Hen's Eggs

Laying hens were fed for a 48-wk period with a basal diet supplemented with a selected strain of Lactobacillus acidophilus at levels up to four million viable cells per gram of feed. Levels of egg production and feed conversion were significantly higher (8 and 14.8%, respectively) than in the control flock, and cholesterol values in yolks were decreased by 18.8%. It is suggested that the latter effect was a reflection of lower serum cholesterol concentrations in treated birds; a maximum reduction of over 55% followed incorporation of the culture into the feed. The level of viable cells in the feed was confirmed as being critical to register the above effects.

Breeding for a sheep with bulky wool by crossbreeding Texel sires with fleece‐weight‐selected Romney ewes

Abstract This investigation examined an alternative option to selection within breed for improving wool bulk by crossbreeding traditional long‐wooled sheep with introduced Texels. A flock of bulky high‐fleece‐weight sheep was established by crossbreeding high‐fleece‐weight‐selected (HF) Romney ewes with bulky‐wooled Texel rams. A local Romney control flock (LC) was formed at the same time. These two flocks were grazed together at the Gore Research Station. The HF flock established earlier and its random control (RC) flock were both located at another site (Woodlands Research Station), and were also included in the comparison through common RC‐LC sire linkages. The Texel x Romney (TR) flock had significantly (P < 0.01) higher liveweights and fleece weights than its LC. The TR flock was 7 and 5% heavier than the HF flock for birth and weaning weight, and significantly (P < 0.01) heavier for spring liveweight and 16‐month liveweight at 11 and 9% respectively. Wool return per head predicted for the TR flock w...

Treatment of Commercial Broiler Chickens with a Characterized Culture of Cecal Bacteria to Reduce Salmonellae Colonization

The effect of treatment with a newly developed characterized continuous-flow (CCF) culture composed of 29 strains of cecal bacteria on salmonellae colonization was evaluated in commercially reared broiler chickens. Newly hatched chicks in three flocks were sprayed with CCF culture as they were placed in rearing houses and compared with untreated flocks on the same farm. Hatchery transport tray liners and rearing house feed, water, and litter samples were cultured for the presence of salmonellae. Cecal samples were cultured after 3- and 6-wk growout. Skin-feather samples were cultured at 6-wk growout. Fifty-five percent of the transport tray liners were contaminated with salmonellae on the day of chick placement. At 3 wk, salmonellae serotypes present on the tray liners were widely distributed in the litter of the rearing houses. The results indicated that exposure to salmonellae occurred before culture treatment and continued in the rearing houses during the 6-wk growout period. Salmonellae cecal colonization was decreased (P < .05) in two of the treated flocks at 3 wk and diminished (P < .07) in the third treated flock compared with control flocks. At 6 wk, skin-feather contamination and cecal colonization were decreased (P < .05) in one of the treated flocks whereas no treatment effect occurred in two of the treated flocks compared with controls. The results clearly indicate the necessity of implementing integrated programs to control salmonellae in both the hatchery and rearing house environments. The CCF culture served to enhance salmonellae colonization resistance and may serve as a useful component of an integrated control program.

Selection for or against facial eczema susceptibility in Romney sheep, as monitored by serum concentrations of a liver enzyme

Abstract Genetic selection for or against susceptibility to facial eczema (FE) was begun in Romney sheep in 1975, with the establishment of a resistant (R) selection flock, a susceptible (S) selection flock, and later a control (C) flock. For all but the initial years, rams were identified by performance testing with a sporidesmin challenge, ranking them on relative elevation of the liver enzyme, gamma glutamyltransferase (GGT) measured in serum. A different dose rate of sporidesmin was used for performance testing in the R and the S flocks, with a balanced half of the C‐flock animals being tested at each dose rate; in some years R‐flock animals showing no elevation of GGT were re‐dosed later at an even higher rate. Mixed‐model methodology was used to determine responses to selection, expressing results as a breeding value for logeGGT. Analyses took account of one dose rate used in the R flock and in half of the C flock, and a second (lower) dose rate used in the remainder of the C flock and in the S floc...

Genetic Progress in the Camda Group Breeding Scheme Nucleus

A group breeding scheme was set up in 1976 by 10 Welsh Mountain breeders. The objective of the scheme was to improve lamb growth rate, mature size, mothering ability and litter size by selection in a nucleus flock. The original design of the scheme involved two control flocks. The Genetic Control flock was set up from the original base population and was used to monitor environmental changes in the nucleus flock. A Commercial Control flock comprised of a random selection of ewes mated to rams, which were purchased annually and represented the average animal available in the breed. An analysis of genetic progress in lamb growth in the first 9 years of the scheme was reported by Guy et al (1986). This paper presents genetic parameters and genetic trends for three traits recorded between 1977 and 1992.

Wool follicle morphology and cell proliferation in New Zealand Romney sheep: a seasonal comparison of fleeceweight-selected and control rams

Effects of selection for high fleeceweight in the New Zealand Romney sheep were investigated in relation to the morphology of individual follicles and changes in the germinative cell population of the follicle bulb. Two-year-old Romney rams, 10 from each of two selection lines (Massey University fleeceweight-selected (FWT) and control (CLT) flock), were run together on pasture for a period from June to early December. At three times during this observation period (June, August and November) skin samples were taken from their midside flanks after local injection of bromodeoxyuridine (BrdU), to assess proliferation of bulb cells and several dimensional measurements of the follicle bulb and dermal papilla. FWT sheep had larger follicle dimensions than CLT sheep during winter and summer, with a greater number of proliferating bulb cells. Both flocks showed a seasonal change in follicle size, with a decline during winter, but the size of the dermal papilla was less affected than the germinative tissue area. Measurements of proliferation density (number of proliferating cells per area/volume of bulb tissue) suggest that changes in proliferation density do not contribute to flock differences in fleece production. However, during summer, FWT showed a 40% advantage over CLT sheep in hourly cell production based on data from three dimensional follicle bulb extrapolation. The different genotypes showed variations in width, as well as area of cortex and inner root sheath (IRS), measured across the top of the dermal papilla. The expression of these differences was further enhanced through seasonal influences, suggesting that there is an interaction between genetic/flock influences and seasonal influences on cell distribution to cortex and inner root sheath.