FC Line Research Articles

Response to selection and genotype-environment interaction in mink (Neovison vison) selected on ad libitum and restricted feeding

Nielsen, V. H., Moller, S. H., Hansen, B. K. and Berg, P. 2011. Response to selection and genotype-environment interaction in mink (Neovison vison) selected on ad libitum and restricted feeding. Can. J. Anim. Sci. 91: 231-237. Mink were selected for high November weight (AL line) and low feed conversion ratio (FC line) on ad libitum feeding and for high November weight on restricted feeding (RF line). After three generations of selection, the average estimated breeding value for November weight was 533, 326, and 150 g in males and 168, 82, and -85 g in females in the AL, RF, and FC lines. The breeding value for feed conversion ratio was -1.39, -0.84 and -0.68 kg feed kg-1 gain in males and -0.39, -0.31 and -0.23 kg feed kg-1 gain in females in the selection lines. In generation 4, the AL, RF and FC lines were tested on both ad libitum and restricted feeding. The estimated breeding value for November weight in males in the AL line (533 g) was significantly greater than that in the RF line (384 g) on ad lib...

Response to selection and genotype–environment interaction in mink (Neovison vison) selected on ad libitum and restricted feeding

Nielsen, V. H., Møller, S. H., Hansen, B. K. and Berg, P. 2011. Response to selection and genotype-environment interaction in mink (Neovison vison) selected on ad libitum and restricted feeding. Can. J. Anim. Sci. 91: 231–237. Mink were selected for high November weight (AL line) and low feed conversion ratio (FC line) on ad libitum feeding and for high November weight on restricted feeding (RF line). After three generations of selection, the average estimated breeding value for November weight was 533, 326, and 150 g in males and 168, 82, and −85 g in females in the AL, RF, and FC lines. The breeding value for feed conversion ratio was −1.39, −0.84 and −0.68 kg feed kg−1 gain in males and −0.39, −0.31 and −0.23 kg feed kg−1 gain in females in the selection lines. In generation 4, the AL, RF and FC lines were tested on both ad libitum and restricted feeding. The estimated breeding value for November weight in males in the AL line (533 g) was significantly greater than that in the RF line (384 g) on ad libitum feeding. The corresponding values on restricted feeding were 297 and 326 g, respectively, which were not significantly different. This indicates genotype×environment interaction. In the AL line, selection improved feed conversion ratio by increased appetite. In the RF line, it was improved by increased feed utilization. Environmental sensitivity in males, estimated from breeding values for November weight was 236 g in the AL line and 58 g in the RF line suggesting that the RF line was more robust to changes in feeding conditions. A smaller litter size in the AL line (4.1) than in the RF line (5.6) indicates that selection for large weight affects reproduction.

Characterization of GH, GHR and IGF-I in Broiler Lines Selected for Rapid Growth or Improved Feed Efficiency

The aim of this study was to figure out the response of the GH axis to selection criteria in broiler chickens. Plasma profiles of GH, IGF-I along with membrane GHR binding activity were examined during rapid growth phase in experimental lines of broiler chickens. The selection criteria applied influenced the plasma GH levels and the number of hepatic GHR. There was a higher plasma GH level in FC chickens compared to GL chickens while the opposite pattern was observed for GHR. The negative correlation between plasma GH levels and hepatic GHR suggest a down regulatory mechanism for GHR in broile r chickens. The absence of line differences in plasma IGF-I levels between GL and FC lines in spite of clear difference in growth rate and in plasma GH concentrations may support the concept that plasma IGF-I does not appear to be GH-dependent, implying the importance of other factors besides GH in the regulation of IGF- I in chickens. The slower growth rate as function of time in the FC line during rapid growth phase was followed by a phase of compensatory growth. On the basis of this growth curve pattern it can be hypothesized that the dynamics of GH action are shifted or extended to the phase of compensatory growth as an effect of the selection on feed conversion. This may be a causal mechanism for the different growth curve pattern in GL and FC lines. Assuming that the metabolic basis for these differences is better understood it may be possible to device other procedures for improving meat quality in poultry industry.

Thyroid Hormones Characteristics and Hepatic Deiodinase Enzyme Activity in Broiler Lines Selected for Growth and Feed Conversion

The present study was carried out to investigate the influence of genotypes on endocrin e parameters in broiler chickens selected for fast growth or better feed conversion rate during the early growth phase. The thyroid hormones levels, hepatic deiodinase enzymes and thyroid hormone receptor activity were analyzed in plasma and hepatic cells of broiler chickens. Age-related changes in plasma T and T levels 4 3 were observed. The decrease of plasma T levels as a function of age was correlated with relative growth 3 rate. The positive relation between T levels and relative growth rate supports the idea that the greater 3 synthesis of this anabolic hormone may be required for the increase in efficiency of protein deposition in chickens at younger ages. In contrast to plasma T concentrations, plasma T levels increased gradually with 3 4 age. Analysis of the T concentration showed a tendency for higher plasma T levels at week 4 and 3 3 significantly higher at week 7 on the GL compared to the FC line. The plasma T concentration in growth 4 selected line was higher in general, and statistically significant at week 4 and 7 of age. The present data show that the decrease of T as a function of age is associated with a decrease in type I deiodinase activity. 3 Analysis of deiodinase enzymes showed a non-significan tly higher type I deiodinase activity in the fast growing than in the slow growing line at week 4 and 7 of age. A significant age differences were found in type I deiodinase activity within the GL line with lower hepatic type I deiodnase activity at week 7 compared to week 4. No line differences were found in specific binding activity, binding capacity and binding affinity constant between lines, which may indicate that the receptor configuration does not differ among the lines. With this finding, it may be concluded that the hepatic T-receptor characteristics have not been influenced by th e 3

Resistance of broiler outbred lines to infection with Salmonella enteritidis

Salmonella infections originating from poultry are one of the major causes of food-borne disease. For the control of salmonella in poultry a multifactorial approach is more likely to be effective, and the genetic resistance of poultry breeds to salmonella infections may be a valuable contribution. Experimental Salmonella enteritidis infections were examined in three different broiler outbred lines: the FC line, which had been selected for feed conversion efficiency; the R line, which had been selected for growth rate; and the C line, a commercially available line. The FC line had the highest mortality rate after intramuscular inoculation with 5 × 10 6 colony forming units (CFU) of S. enteritidis at 2 weeks of age (40% versus 21 and 20% in the other lines). However, at slaughter age, the number of birds carrying salmonella in caecal contents, and the concentration of salmonella in the caecal contents, was lowest in the FC line. The FC and R lines were compared by inoculation with doses ranging from 10 2 to 10 7 CFU S. enteritidis . At sublethal doses (10 5 CFU or less), the FC line carried significantly less salmonella in caecal contents and the rate of systemic infection was lower. The start of shedding was also delayed compared with the R line. At doses of 10 6 CFU S. enteritidis or higher, there were no differences in salmonella carriage between the lines, and the FC line showed higher mortality. In conclusion, resistance to mortality and resistance to the carriage of S. enteritidis do not necessarily coincide within lines, as the FC line showed high mortality but low carriage, both in survivors of high infection doses and in all birds at lower infection doses.

Association of Endogenous Avian Viral and Endogenous Viral Genes with Feed Conversion and Six-Week Body Weight in Broilers

The consistency of the effect of selection on the frequencies of endogenous avian viral (eav) and endogenous viral (ev) specific restriction fragment length polymorphism (RFLP) bands was studied in two broiler lines selected from a single base population and in an F2 population derived from a reciprocal cross of both lines. One broiler line (FC line) was selected for low feed conversion ratio and the other line (GL line) was selected for high 6-wk body weight. In the F2 population, the band frequencies were determined in groups representing separate tails of the distribution of two production traits, namely, low feed conversion ratio between 29 and 42 d of age and body weight at 42 d of age. The F2 population consisted of 288 females belonging to 24 full-sib families. To rule out family effects, the tails for these production traits were composed by either the best or by the worst female performer for each trait in each full-sib family. In total, 29 Hind III-eav, 34 Msp I-eav, and 21 Bam HI-ev bands could be distinguished by RFLP analysis. This report describes the influence of selection on 11 potentially interesting bands. Two bands, the 9.5-kb Hind III-eav and the 15-kb Msp I-eav band, which were found both in higher frequencies in the parental FC line, were also found in higher (P ≤ .05) frequencies in the F2 tail with a favorable feed conversion ratio. A third band, the 6.5-kb Hind III-eav band, present in lower frequencies in the parental GL line, was also present in lower (P ≤ .05) frequencies in the F2 tail of birds with heavy body weight.

The Effect of Environmental Temperature on Episodic Growth Hormone Release of Meat-Type Chickens Selected for 6 Week Body Weight or for Improved Feed Efficiency between 3 and 6 Weeks of Age

The effect of a high (33°C) compared to a normal (23°C) ambient temperature on the pulsatile release of growth hormone (GH) has been studied in 4-week-old, cannulated male meat-type chickens selected for high body weight (GL line) or for improved feed efficiency (FC line). When reared in the normal temperature environment, overall circulating mean and amplitude GH values of FC chickens were significantly higher than those of GL chickens. There were no differences in GH pulse length or frequency between genotypes. The high rearing temperature completely abolished the pulsatility of GH in the plasma in both lines, but without affecting overall mean GH levels.

Effects of genotype and cryopreservation of avian semen on fertility and number of perivitelline spermatozoa.

1. The fertility of freshly diluted and cryopreserved samples of semen obtained from a population of chickens selected for duration of fertility of cryopreserved spermatozoa (FS line) and its unselected control (FC line) were compared over a range of spermatozoa concentrations (10, 40, 80, and 160 x 10(6) sperm/50 microliters insemination). 2. The spermatozoa of the FS line had greater fertility than spermatozoa of the FC line, whether freshly diluted or cryopreserved. Cryopreservation resulted in a reduction in fertility, regardless of line. There were no significant line by genotype interactions. 3. There were fewer spermatozoa from the FC line than the FS line found in the perivitelline membrane (perivitelline spermatozoa). The increase in number of perivitelline spermatozoa with increasing sperm concentration was greater in the FS than FC line. However, the slope of the increase in sperm number in the perivitelline membrane with increasing concentrations of cryopreserved spermatozoa was zero. 4. A minimum of 10(3) perivitelline spermatozoa must be found on day 2 post-insemination for duration of fertility to exceed three days. The ability to produce spermatozoa capable of reaching the forming perivitelline membrane appears to be a quantitative, rather than a qualitative, trait and may be subject to genetic manipulation.

Growth hormone response to TRH in male broiler chickens selected for body weight gain or food conversion and reared at either a moderate or a high ambient temperature.

The aim of the present experiment was to study the growth hormone (GH) response upon thyrotropin releasing hormone (TRH) challenge (2 micrograms/kg body weight) in broiler chickens selected for body weight gain (GL line: fat line) or for feed efficiency (FC line: lean line) reared at either a moderate (33-23 degrees C) or high (33 degrees C) ambient temperature. A higher plasma GH level at 5 min after TRH administration was observed in the high temperature conditioned chickens of both lines. Also at high ambient temperature, an enhanced GH decrease between 15 min and 30 min post-injection and a higher acute elimination rate was calculated compared to moderate ambient temperature. A significantly higher GH secretory response was observed in the leaner FC line chickens, which was probably related to the more pronounced pulsatory GH secretion rate in these chickens. There was no difference in GH acute elimination rate between both lines in both environments. No interactions between line and rearing temperature for these parameters of GH dynamics were observed.

Temporal secretory patterns of growth hormone in male meat‐type chickens of lines selected for body weight gain or food conversion

1. The pronounced episodic release of chicken growth hormone (cGH) in male broiler chicks, as well as its peak interval of about 90 min was confirmed in this study. 2. Lines selected for 6-week body weight (GL line) or for food conversion between 3 and 6 weeks of age (FC line) not only differ in the selection criteria but also in percentage abdominal fat. 3. The overall mean plasma GH concentration was higher in the FC line in both experiments, and this was only caused by peak amplitudes which were almost twice as high as in the FC line. Peak intervals were identical in both selected lines. 4. These observations suggest that decreased abdominal fat and increased protein efficiency may be genetically linked to increased plasma GH peak amplitude. This, and earlier observations on the effectiveness of pulsatile administration of cGH on the growth of broilers suggest that the biological function of GH may depend on its secretory pattern rather than its mean concentration in plasma.

Fat Deposition in a Broiler Sire Strain.: 4. Performance of Broiler Progeny of Four Differently Selected Sire Lines

Cocks from four lines selected for a low amount of abdominal fat (AF), a favorable feed conversion ratio (FC), and high body weight after restricted (GR) or ad libitum (GL) feeding were mated to commercial broiler breeder hens. A total of 3,600 broiler progeny in three hatches from these matings was reared by line in litter pens.At 41 days of age GR and GL line progeny had significantly heavier body weights, poorer feed conversion ratio, and higher percentages of abdominal fat than AF and FC line progeny. At comparable body weights (AF, 1,893; FC 1,918; GR, 1,848; and GL, 1,897 g) feed conversion was most favorable for FC line progeny (1.72), AF and GL line progeny did not differ (1.77), and GR line progeny had the poorest feed conversion ratios (1.79). The AF line progeny had the lowest percentage abdominal fat (1.88%), followed by FC line progeny (2.20%), GL line progeny (2.91%), and GR line progeny (3.10%). As in the pure lines, selection for body weight after restricted feeding was not effective in obtaining leaner and more efficient chickens. When compared with differences between pure lines, results of the broiler progeny matings indicate that body weight, feed conversion, and percentage abdominal fat are inherited largely in an additive manner.

Fat Deposition in a Broiler Sire Strain: 2. Comparisons Among Lines Selected for Less Abdominal Fat, Lower Feed Conversion Ratio, and Higher Body Weight after Restricted and Ad Libitum Feeding

Four lines were selected from a broiler sire strain. Selection criteria were sib selection for a low amount of abdominal fat relative to body weight (AF line), individual selection for feed conversion (feed consumed/weight gain) from 21 to 42 days of age (FC line), individual selection for body weight after restricted feeding (GR line), and individual selection for body weight after ad libitum feeding (GL line). In the fifth generation lines were compared at 6 weeks of age for body weight, percent abdominal fat, feed conversion, slaughter yield, and chemical composition. Rankings of lines reared in groups on litter and in individual cages were the same for all traits examined. Lines GR and GL hardly differed, whereas lines AF and FC, compared with line GL, had, respectively, significantly lower body weights (−293 g and −228 g),less abdominal fat (−1.45% and −1.00%), better feed conversions (−.11 and −.17), and higher griller yields (.50% and .70%).Selection for body weight after restricted feeding was not effective in reducing fat deposition. When compared at the same age with the line selected for body weight after ad libitum feeding, sib selection against abdominal fat and selection for a better feed conversion reduced abdominal fat, improved feed conversion, and increased slaughter yields.