Effects of nutrient density on growth and carcass traits in fast- and slow-feathering female turkeys

Effects of finisher diet nutrients density and slaughter age on energy and protein efficiency, productive and economic performance and meat quality of broilers

BACKGROUND

The current broilers have been greatly optimized for weight gain and breast yield, which necessitates the provision of nutrients-dense diets for maximum potential.

OBJECTIVES

The current study aimed to evaluate the effect of finisher diet nutrients density (ND) on energy and protein efficiency, productive and economic performance and breast meat quality of broilers raised until different slaughter age.

METHODS

A total of 600 23-day-old broiler male chicks (Cobb-500) were assigned to 10 treatments with six replicates and 10 birds each. Experimental treatments were included factorial arrangement of five increment (2.5%) levels of finisher diet ND (92.5%, 95%, 97.5%, 100% and 102.5% as strain recommendation) and slaughtered at 38 or 46 days of age. The relative difference in the energy level of experimental diets was used to increase ND levels at the same ratio.

RESULTS

Feed intake (FI) and breast meat quality traits exception water holding capacity (WHC) were not affected by finisher diet ND. In response to increasing finisher diet ND, energy and protein efficiency, productive traits, bio-economic index (BEI) and breast relative weight (BRW) linearly improved. However, residual feed intake and breast meat WHC improved with a quadratic trend. By using broken-line regression analysis, the optimum dietary ND was obtained at 97.5%-102% of strain recommendation. Energy and protein efficiency, feed conversion ratio and BEI deteriorated by prolonging rearing period. The BRW, meat lightness (L*), redness (a*), hue angle (h*) and WHC values for the birds slaughtered at 46 days of age were significantly higher, and cooking loss was lower than those slaughtered at 38 days old.

CONCLUSIONS

Broilers during the finisher period are not able to regulate their FIs with diet ND. The energy and protein efficiency, productive and economic performance were reduced when broilers were fed diluted diet or the rearing period was prolonged.

Early and late feathering in turkey and chicken: same gene but different mutations

BACKGROUND

Sex-linked slow (SF) and fast (FF) feathering rates at hatch have been widely used in poultry breeding for autosexing at hatch. In chicken, the sex-linked K (SF) and k+ (FF) alleles are responsible for the feathering rate phenotype. Allele K is dominant and a partial duplication of the prolactin receptor gene has been identified as the causal mutation. Interestingly, some domesticated turkey lines exhibit similar slow- and fast-feathering phenotypes, but the underlying genetic components and causal mutation have never been investigated. In this study, our aim was to investigate the molecular basis of feathering rate at hatch in domestic turkey.

RESULTS

We performed a sequence-based case-control association study and detected a genomic region on chromosome Z, which is statistically associated with rate of feathering at hatch in turkey. We identified a 5-bp frameshift deletion in the prolactin receptor (PRLR) gene that is responsible for slow feathering at hatch. All female cases (SF turkeys) were hemizygous for this deletion, while 188 controls (FF turkeys) were hemizygous or homozygous for the reference allele. This frameshift mutation introduces a premature stop codon and six novel amino acids (AA), which results in a truncated PRLR protein that lacks 98 C-terminal AA.

CONCLUSIONS

We present the causal mutation for feathering rate in turkey that causes a partial C-terminal loss of the prolactin receptor, and this truncated PRLR protein is strikingly similar to the protein encoded by the slow feathering K allele in chicken.

Effect of dietary nutrient density and vitamin premix withdrawal on performance and meat quality of broiler chickens

BACKGROUND

The objective of this study was to evaluate the effects of feeding high- and low nutrient density diets, and three different vitamin premix withdrawal regimes on broiler performance and meat quality. Male broiler chicks (480 days old) were reared on the floor in a 2 × 3 factorial arrangement for 42 days. Chickens were slaughtered at 42 days of age and meat samples kept at -20 ± 1°C and analysed after 1, 90 and 180 days of storage.

RESULTS

Broiler performance was significantly affected by dietary nutrient density. Vitamin premix withdrawal had no significant effect on body weight. The results showed no significant differences between nutrient density and vitamin premix withdrawal on lightness (L*), redness (a*) and yellowness (b*). Oxidative stability of thigh muscle lipids during frozen storage was significantly affected by nutrient density, while vitamin premix withdrawal had no significant impact on lipid oxidation. High nutrient density diet led to a significantly (P < 0.05) decreased pH compared with the low nutrient density diet.

CONCLUSION

Increasing dietary nutrient density improved broiler performance but impaired meat quality while vitamin premix withdrawal during finisher periods had no negative effect on broiler performance and meat quality.

The feathering gene is linked to degranulation and oxidative burst not cytokine/chemokine mRNA expression levels orSalmonella enteritidisorgan invasion in broilers

In the past, we showed differences in heterophil function between parental broilers (A [fast feathering] > B [slow feathering]) and their F1 reciprocal crosses (D [fast feathering] > C [slow feathering]). In the present study, we evaluated the linkage of the feathering gene to heterophil function, pro-inflammatory cytokine/chemokine mRNA expression levels, and resistance to Salmonella enteritidis organ invasion. Heterophils were isolated from 2-day-old chickens (C and D) separated into males and females - slow males and females (SM and SF), and fast males and females (FM and FF). Heterophil functions of degranulation and oxidative burst were measured. Heterophils from FF chickens (183+/-8.9) released more (P < 0.05) beta-d-glucuronidase (microM) than heterophils from SF chickens (149+/-3.7); FF heterophils (4.6 x 10(4)) generated a significantly (P < 0.05) greater oxidative burst (mean relative fluorescent units) compared with SF heterophils (4.2 x 10(4)). Interleukin-6, CXCLi2, and interferon-alpha mRNA expression levels were quantitated by real-time quantitative reverse transcriptase-polymerase chain reaction. No differences were observed between SM and FM or between SF and FF heterophils. Finally, 1-day-old chickens were administered S. enteritidis and liver/spleen organ invasion was quantitated. No differences were observed between the number of S. enteritidis-positive FF and SF chickens, but FM were significantly (P < 0.05) more resistant to S. enteritidis organ invasion than SM chickens. The data indicate degranulation and oxidative burst were linked with the feathering gene; however, interleukin-6, CXCLi2, and interferon-alpha mRNA expression levels were not. Furthermore, susceptibility to in vitro S. enteritidis organ invasion was not linked to the feathering gene.