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Encapsulation of bacteriophages ("phage") protects phage against environmental deactivation and provides a product that is easy to handle for storage and application with animal feed as an antibiotic alternative. The objective of this study was to evaluate an orally administered, encapsulated phage for efficient phage release in the gastrointestinal tract (GIT) of young chicks receiving feed. An optimized formulation that consisted of 0.8% low molecular weight (MW) alginate, 2% ultra-low molecular weight alginate and 3% whey protein completely released the encapsulated phage within 60 min under simulated intestinal conditions. This product was given to broiler chicks to determine passage time and distribution of the viable phage within the GIT. Following a single oral dose of 10 9 plaque-forming unit (PFU)/chick, the major portion (peak concentration) of the encapsulated phage passed through the chick's GIT and was detected in the feces within 4 h, with low levels being continuously excreted for up to 24 h. In comparison, the passage of free phage through the GIT occurred faster as indicated by a peak concentration in feces after 1.5 h. In assessing the temporal phage distribution, both encapsulated and free phage treatments showed no apparent difference, both having low levels of 10 2 to 10 6 PFU/g of contents along the entire GIT after 1, 2 and 4 h. These low concentrations recovered in vivo led us to examine various exposure conditions (with feed, fecal material, and buffer solutions) that were suspected to have affected phage viability/infectivity during oral delivery, sample recovery, and enumeration by plaque assay. Results showed that the exposure conditions examined did not significantly reduce phage viability and could not account for the observed low phage levels following oral administration in chicks that are on feed. In conclusion, an oral encapsulated phage dose can take more than 4 h to completely move through the GIT of young chicks. Thus, repeated or higher doses may be necessary to attain higher phage concentrations in the GIT., (© Crown copyright 2016.)

Genetic parameters for the ascites syndrome (AS) were estimated for meat-type chickens. Data had been collected over 11 generations of selection for body weight and other traits within two distinct breeds (Cornish and White Rock). Linear methods (LM) were used to estimate genetic parameters and also to analyze a binary measure of survival. Survival analyses (SA) were also conducted to estimate the effects of various factors influencing the incidence of AS by evaluating the number of days that the birds survived. The animal model was used exclusively with linear methods. Heritabilities (h2) on the liability scale were 0.12 +/- 0.02 and 0.22 +/- 0.01 in the White Rock and Cornish breeds, respectively; however, the genetic correlation (r(g)) with body weight was not possible to estimate due to the low prevalence of the defect trait studied (1.5% in the Cornish and 1.1% in the White Rock). Because males are more prone to AS, the h2 using the male records only were 0.22 +/- 0.017 and 0.41 +/- 0.009, and the r(g) were 0.35 +/- 0.007 and 0.22 +/- 0.009 in the dam and sire populations, respectively. In conclusion, the heart defect investigated was heritable and had a positive genetic correlation with body weight.

Restriction fragment length polymorphism analysis was conducted for a set of eight different meat chicken-derived endogenous viral genes (ev genes) of the avian leukosis viral (ALV) family. Each viral element was first isolated into a separate single-element line by selective breeding. Genomic DNA from the founder male for each semi-congenic, single-element line was digested with each of four restriction enzymes, and the resulting Southern blots were each hybridized with up to four probes representing different portions of the ALV retroviral genome. Among the eight elements, there was one that represents the broiler equivalent of locus ev3 of White Leghorn chickens. A second broiler element showed a SacI-specific junction fragment similar to that of ev8. The remainder appeared to be different from any of the 21 ev genes previously described for White Leghorn chickens. Four of the eight elements examined were essentially complete, but the rest have sustained internal deletions.

The molecular architecture of the sex-linked late-feathering region of the chicken genome is still poorly defined. Current evidence points to a strong association between the presence of the endogenous viral element ev21 and the late-feathering phenotype. However, analysis at the molecular level has demonstrated that this is not a simple case of insertional mutagenesis. Instead, the structure of the region of the chicken genome containing the feathering locus is complex and variable between and within lines of chickens. Significant clues to the molecular structure of this genomic region can be obtained by analyzing rare and revertant genotypes. However, searching for rare genotypes can only be carried out effectively using quick screen methodology. This paper describes a quick, polymerase chain reaction-based test for ev21 that facilities the search for rare genotypes.

Feed consumption and feed efficiency data obtained over nine generations from three selected strains of broilers were adjusted for differences in either initial or initial and final test BW (at 28 and 42 d, respectively). Genetic and environmental variables were estimated for each strain using an animal model with restricted maximum likelihood procedures to avoid bias due to reduced genetic variation caused by selection. Variance component and heritability estimates before and after adjustment of these traits for differences in test weights were evaluated. Adjustments of feed consumption data for either initial test BW or both initial and final test BW reduced additive genetic and environmental variation. Reductions were relatively greater for additive genetic than for environmental variance, thereby reducing the heritability of the adjusted trait. Adjustment of feed efficiency for initial test BW altered additive genetic variation little and reduced environmental variation slightly; however, correction for both test BW reduced variation of both components. Heritability of adjusted feed efficiency was 40% larger (.33 to .35 vs .21 to .28) than for uncorrected feed efficiency, but phenotypic variation of the adjusted feed efficiency was reduced 42% (5.82 to 6.13 vs 10.30 to 11.35). Heritabilities of feed consumption and efficiency were essentially the same (.34 and .36) after adjustment for both test weights. Changes in genetic and environmental variation and heritability due to adjustments were similar for the three strains.

In vivo nuclear magnetic resonance (NMR) imaging and spectroscopy techniques were used to monitor changes in P- and H-containing molecules in embryos of two broiler strains (30 and 31) differing genetically in fat content and ranging in age from 0 to 20 days of incubation. Chemical analysis showed that Strain 30 has more carcass fat than Strain 31 at market age (7 wk). Proton (1H) and 31P spectra were obtained on four eggs per strain at Days 0, 2, 4, 6, 8, 11, 12, 14, 16, 17, 19, and 20 of incubation. Fat:water, phosphomonoester (PME):phosphodiester (PDE), and adenosine triphosphate (ATP):PDE ratios were calculated. Chicks were hatched, grown to market weight (2,000 g for females and 2,300 g for males at 7 wk), and the whole intact carcasses were analyzed for crude fat. Hydrogen-1 NMR spectroscopy studies of incubated eggs indicated no significant difference (P > .05) in the fat:water ratio between the two strains. The difference in the PME:PDE ratios between the two strains as obtained by 31P-NMR spectroscopy over all days of incubation analyzed was not significant (P > .05); however, there was a significant difference in this ratio between the two strains at Days 4, 6, and 11. Up to Day 16, Strain 30 had a slightly, but not significantly (P > .05), higher ATP:PDE ratio as shown on 31P-NMR spectra, whereas after Day 17 the ATP:PDE ratio was significantly higher (P < .01) for Strain 31. Strain 31 birds had a significantly lower (P < .05) crude fat content. There was a significant difference (P < .05) in 7-wk carcass fat content between sexes, males having significantly (P < .01) less fat than females, which was correlated with a significantly higher (P < .01) ATP:PDE ratio in male embryos. It might be possible to use ATP:PDE ratios obtained during embryonic development by 31P-NMR to select strains of birds for low fat content at market weight and to distinguish between sexes during late embryonic development.

The present study was designed to document the complexity of endogenous viral (ev) genes and seek evidence for their association with production traits in selected and control strains of meat-type chickens. Three populations were studied, each consisting of a control strain and one to three strains selected for various production traits. The ev genes were revealed by digesting genomic DNA with restriction enzymes and detecting DNA fragments on Southern blots using radioactive probes from nucleotide sequences of the avian leukosis virus genome. A total of 31 polymorphic ev loci were identified in these populations from a SacI digest, with an average of 7.3 ev genes per bird. There were no significant differences in ev genes per bird between strains within populations or between selected and control strains overall. Thirty of 62 comparisons in the three populations indicated ev gene frequency differences (P less than .05). Within populations, 13 of 93 comparisons of ev gene frequencies between control and selected strains and 8 of 62 between three selected strains of a sire population showed such differences (P less than .05). Selection for body weight and feed efficiency had been observed to reduce gene frequencies of the slow-feathering gene, which usually contains the ev21 locus; however, these effects were not detected (.05 less than P less than .06) between strains of the dam population in the current study. Such differences suggested possible associations between ev genes and production traits in meat-type chickens.

Genetic correlations based on sire variance and covariance components were estimated for broiler traits. Data were collected from various selected and control strains of sire and dam populations during five generations of selection. Results of analyses of variance for each of the strains within generations and populations were pooled across strains and generations. Correlations between body and carcass weights were all above .8. Weight gain (WG) had similar correlations with these traits with the exception of body weight at 28 days (.57 in site and .69 in dam populations). Body and carcass weights and WG had high correlations with feed consumption (FC) (greater than .7); however, values for feed efficiency (FE) varied: -.58, -.23 for 28-day body weight; -.17, .16 for 42-day body weight; .25, .43 for WG; and .53 in the dam population for carcass weight. Correlations of body and carcass weights and WG with abdominal fat weight (AFW) and percentage (AFP) were generally small to moderate with values being about half as large for AFP as for AFW. Feed consumption and FE were negatively correlated (-.51, -.22) in both populations. In the dam population, FC was positively correlated with AFW and AFP (.42, .55) but FE was negatively correlated with these traits (-.41, -.70). Abdominal fat weight and AFP were highly correlated (.99, .97). Values tended to be similar not only for these populations but also for this and other studies. Simultaneous genetic improvement of growth rate, FE and carcass leanness is feasible in broilers. Selection for WG, FE, and AFP should be effective.

Male reproductive capacity evaluated as percent fertility, hatchability, and duration of fertility was assessed for cockerels of 13 commercial broiler lines at 39 and 59 weeks of age using White Leghorn females. For each age the eggs were collected for 21 days following a second insemination of females with .05 ml of undiluted semen. With the exception of duration of fertility the differences among strains were not significant, suggesting that the differences among males within a strain were greater than those among strains for fertility and hatchability. The average percent fertility for a 4-day and 7-day postinsemination interval was 92.1% and 89.9% for Age I and 87.7% and 84.3% for the respective fertilities for Age II. The differences due to age were not significant. However, age had a significant effect on hatchability of settable eggs during 4 days (85.5% vs. 78.2%) and 7 days (83.2% vs. 74.9%) following artificial insemination (AI). The percentage of hatched chicks decreased progressively after day 7 following AI due to the greater incidence of infertile eggs and gradual increase in early embryonic mortality. The duration of fertility among broiler lines ranged between 9.7 to 13.9 days. The significant interaction between strain and age for duration of fertility reflected the changes in ranking among various broiler strains.

Sire and dam populations of chickens were synthesized from commercial broiler parent stocks at the Animal Research Centre, Ottawa. The production of two-way and four-way crosses during synthesis permitted measurement of maternal and sex-linked genetic effects on body weight and conformation traits. Sex-influenced effects were also measured. Reciprocal cross differences were minimal. Consequently, there was no evidence among stocks within parental type of maternal effect differences and only minimal evidence of sex-linked genetic effects. As expected, sex-influenced effects were large. Hence, it appears that breeders must work within strains or stocks to improve maternal and sex-linked genetic effects for body weight and conformation.

Genetic variation for more than 40 traits was assessed in 26 stocks of mature chickens reared together and fed ad libitum from hatching to slaughter at 507 days of age. There was greater genetic variation among males than among females. The intraclass correlation, t, was high (greater than .75) for measures of size and weight and moderate (.20 to .60) for most other traits (P less than .05) including a measure of lean distribution (.37). Three main categories of stocks were studied, viz. outbred Leghorns, medium-sized stocks, and contemporary heavy meat chickens. Differences in lean distribution were not associated with category, but differences of 40 to 50 g/kg lean in the breast of some stocks may be caused by a single gene. Lean:bone ratios were similar in medium and heavy stocks but were greater (P less than .05) in heavy meat-types compared with outbred Leghorns. Bone density was higher (P less than .01) in females compared with males and in outbred Leghorns compared with heavier stocks (P less than .01). Heavy meat-type males were leaner (P less than .01) and had proportionately less fat in the abdominal cavity than outbred Leghorns. Carcass fatness was similar among stocks of females, but abdominal fat was lower in Leghorns selected for high egg production compared with unselected Leghorns (P less than .05) and heavy stocks (P less than .001). One resistant and two Marek's disease-susceptible stocks were replicated in a specific pathogen-free (SPF) environment. Spleen weight was larger (P less than .001) in the conventional environment. Females were relatively smaller (P less than .05) than males in the conventional environment. Body temperature (t = .25, P less than .05) and feed intake were assessed in males. Heavy meat birds had a lower (P less than .01) body temperature than outbred Leghorns and medium-sized stocks. Differences among stocks for feed intake (t = .77) were significant (P less than .05); however, they were greatly reduced when feed intake was expressed as g/kg liveweight (LW) (t = .49) or g/kg LW.75 (t = .25). Outbred Leghorns ate less in absolute terms but significantly more (P less than .01) as a proportion of LW or LW.75 than the medium and heavy lines.

Experimental control Strains 30, representative of commercial broiler dam stocks in the late 1970's, and K, representative of commercial broiler stocks of 20 years earlier, were compared. Development of carcass fatness and related traits and physiological traits from 3 to 17 weeks of age were studied. About 12 chickens of mixed sex of each strain were bled and killed at 2-week intervals beginning at 3 weeks of age for measurement of traits. From 3 to 17 weeks of age, percentage abdominal fat of carcass, carcass fat (ether extract) and plasma very low density lipoproteins (VLDL) increased with age. Percentage carcass nitrogen, ash, and water, lipase activity of abdominal fat expressed per mg protein or per g of fat (LIP/g F), and protein concentration of the abdominal fat enzyme preparation (P/ml EPrep) decreased with age. Strain 30 had a higher percentage of abdominal fat and carcass fat, but less carcass nitrogen, ash, and water than Strain K, although there were interactions with sex and age. For physiological traits, Strain 30 had more LIP/g F and less P/ml EPrep than Strain K. Males had lower percentages of abdominal fat, carcass fat, and plasma VLDL, and higher percentages of carcass nitrogen, ash, and water than females. There were no significant differences between sexes for the other physiological traits. There were significant (P less than .01) partial correlations between plasma VLDL and percentage abdominal fat (.22), and between P/ml EPrep and percentages of abdominal fat (-.25), carcass fat (-.29), carcass nitrogen (.30), and carcass water (.30). These observations in conjunction with multiple regression analyses indicated that, in addition to plasma VLDL, protein concentration of adipose tissue expressed as P/ml EPrep might be a useful predictor of fatness in chickens.

Genetic parameters of physiological, growth, and fatness traits were investigated in one control and two selected dam strains of broiler chickens. Feed consumption and efficiency were measured between 28 and 42 days of age but were adjusted to estimate values of population average body weights at these ages. Birds were bled at 45 days of age for assay of plasma very low density lipoproteins (VLDL) and killed at 47 days of age for carcass and fat measurements. Abdominal fat was assayed for lipase activity expressed per milligram of protein (LIP/mgP) or per gram of fat (LIP/gF) and protein content of the enzyme preparation expressed as microgram protein/mL (P/mLEPrep). Absolute values of partial correlations corrected for sex and strain were low between production and physiological traits and between fatness and LIP/mgP but were moderate at .3 between fatness and plasma VLDL, LIP/gF, and P/mLEPrep. Heritabilities were moderate to high (greater than or equal to .32) for growth and fatness traits, moderate (.25) for plasma VLDL, and low (less than or equal to .16) for P/LEPrep, LIP/mgP, and LIP/gF. Genetic correlations involving plasma VLDL were as follows: .49 with body weight at 42 days, -.74 with feed consumption, .64 with feed efficiency, .24 with carcass weight at 47 days, 1.07 with abdominal fat weight, and .97 with abdominal fat percentage. Similarly, absolute values of genetic correlations involving P/mLEPrep tended to be as high or higher but genetic correlations involving LIP/mgP and LIP/gF tended to be lower than those involving plasma VLDL.(ABSTRACT TRUNCATED AT 250 WORDS)

Weekly body weights, feed consumption (FC), and feed efficiencies (FE = gain:feed) of 148 male and 125 female broilers were measured individually between 2 and 7 wk of age. Multiple regression analyses of these traits were performed to examine the influence of body weight, weight gain or feed consumption, age, and individual broiler differences. Four different measures of FC and FE from 4 to 6 wk of age were compared within sex: age-constant FC and FE; weight-constant FC and FE; age-constant-weight-corrected FC and FE; and weight-corrected FC and FE, which estimate weight-constant measures. Much of the variation (85 to 90%) among broilers in FC and FE was due to age and body weight differences. Partial regression coefficients indicated that increased body weight at commencement of testing was associated with increased FC and reduced weight gain and FE. Correlations between age-constant and weight-constant FC were zero. This indicates the two forms have little in common. Correlations of body weights and weight gain with FC were negative (-.5 to -.8) for weight-constant values but positive (.5 to .8) for age-constant values. Hence, correlations of the correct (weight-constant) measure of FC with body weights indicate that faster growth gives rise to lower broiler feed consumption. Age-constant and weight-constant FE values were positively correlated (.8 to .9); however, the latter values had larger correlations with body weights and weight gain. These results emphasize the need to correct age-constant FC and FE for body weight differences in order to evaluate differences in efficiency among broilers more accurately.

The incidence of degenerative myopathy of the Musculus supracoracoideus (DMS) was calculated in 23 strains comprising 1868 meat-type chickens. Twenty strains were commercial parent stocks and three strains were experimental strains from Ottawa similar to commercial broiler stocks of some 15 to 20 years ago. In the commercial strains DMS incidence ranged from 0 to 43% in males and 0 to 22% in females at ages ranging from 49 to 68 weeks. The three experimental strains did not have DMS. Data from strains with DMS were analyzed for associations between DMS and each of a number of body size and egg production traits. The DMS-positive birds had a larger breast angle (P less than .05) measured at 6 weeks of age (93 vs. 89 degrees) and a larger body weight (P less than .01) at 52 weeks (3748 vs 3594 g) than DMS-free birds. No significant relationships with other body size or egg production traits were detected.