Correlated responses in lines of chickens divergently selected for fifty-six-day body weight. 1. Growth, feed intake, and feed utilization

Genome-Wide Association Study of Feed Efficiency Related Traits in Ducks

Simple Summary

Good feed efficiency (FE) is an important trait to ensure the economic output of the livestock and poultry industries. Herein, a genome-wide association study was conducted to identify potential variants and genes associated with seven FE measures in ducks. Genomic DNA samples of 308 ducks were collected and sequenced. All animals were evaluated concerning body weight gain (BWG), feed intake (FI), residual feed intake (RFI), feed conversion ratio (FCR), and weight at 21 (BW21) and 42 days of age (BW42). Overall, 4 (FCR), 3 (FI), 36 (RFI), 6 (BWG), 8 (BW21), and 10 (BW42) single nucleotide polymorphisms (SNPs) were significantly associated with these FE traits, respectively. Moreover, candidate genes close to the identified variants were found to be mainly involved in key pathways and terms related to metabolism. In summary, these findings improve our understanding of poultry genetics and provide new foundations for breeding programs aimed at maximizing the economic potential of duck breeding and farming.

Abstract

Feed efficiency (FE) is the most important economic trait in the poultry and livestock industry. Thus, genetic improvement of FE may result in a considerable reduction of the cost and energy burdens. As genome-wide association studies (GWASs) can help identify candidate variants influencing FE, the present study aimed to analyze the phenotypic correlation and identify candidate variants of the seven FE traits in ducks. All traits were found to have significant positive correlations with varying degrees. In particular, residual feed intake presented correlation coefficients of 0.61, 0.54, and 0.13 with feed conversion ratio, and feed intake, respectively. Furthermore, data from seven FE-related GWAS revealed 4 (FCR), 3 (FI), 36 (RFI), 6 (BWG), 8 (BW21), and 10 (BW42) SNPs were significantly associated with body weight gain, feed intake, residual feed intake, feed conversion ratio, and weight at 21 and 42 days, respectively. Candidate SNPs of seven FE trait-related genes were involved in galactose metabolism, starch, propanoate metabolism, sucrose metabolism and etc. Taken together, these findings provide insight into the genetic mechanisms and genes involved in FE-related traits in ducks. However, further investigations are warranted to further validate these findings.

Comparison of Selection Signatures between Korean Native and Commercial Chickens Using 600K SNP Array Data

Korean native chickens (KNCs) comprise an indigenous chicken breed of South Korea that was restored through a government project in the 1990s. The KNC population has not been developed well and has mostly been used to maintain purebred populations in the government research institution. We investigated the genetic features of the KNC population in a selection signal study for the efficient improvement of this breed. We used 600K single nucleotide polymorphism data sampled from 191 KNCs (NG, 38; NL, 29; NR, 52; NW, 39; and NY, 33) and 54 commercial chickens (Hy-line Brown, 10; Lohmann Brown, 10; Arbor Acres, 10; Cobb, 12; and Ross, 12). Haplotype phasing was performed using EAGLE software as the initial step for the primary data analysis. Pre-processed data were analyzed to detect selection signals using the ‘rehh’ package in R software. A few common signatures of selection were identified in KNCs. Most quantitative trait locus regions identified as candidate regions were associated with traits related to reproductive organs, eggshell characteristics, immunity, and organ development. Block patterns with high linkage disequilibrium values were observed for LPP, IGF11, LMNB2, ERBB4, GABRB2, NTM, APOO, PLOA1, CNTN1, NTSR1, DEF3, CELF1, and MEF2D genes, among regions with confirmed selection signals. NL and NW lines contained a considerable number of selective sweep regions related to broilers and layers, respectively. We recommend focusing on improving the egg and meat traits of KNC NL and NW lines, respectively, while improving multiple traits for the other lines.

Feed conversion ratio, residual feed intake and cholecystokinin type A receptor gene polymorphisms are associated with feed intake and average daily gain in a Chinese local chicken population

Background

The feed conversion ratio (FCR) and residual feed intake (RFI) are common indexes in measuring feed efficiency for livestock. RFI is a feed intake adjusted for requirements for maintenance and production so these two traits are related. Similarly, FCR is related to feed intake and weight gain because it is their ratio. Cholecystokinin type A receptor (CCKAR) plays an important role in animal digestive process. We examined the interplay of these three parameters in a local Chinese chicken population.

Results

The feed intake (FI) and body weights (BW) of 1,841 individuals were monitored on a daily basis from 56 to 105 d of age. There was a strong correlation between RFI and average daily feed intake (ADFI) and a negative correlation between the FCR and daily gain (r_g = − 0.710). Furthermore, we identified 51 single nucleotide polymorphisms (SNPs) in the CCKAR and 4 of these resulted in amino acid mutations. The C334A mutation was specifically associated with FI and the expected feed intake (EFI) (P <  0.01) and significantly associated with the average daily gain (ADG) (P <  0.05). G1290A was significantly associated with FI and EFI (P < 0.05).

Conclusion

FCR is apply to weight selecting, and RFI is more appropriate if the breeding focus is feed intake. And C334A and G1290A of the CCKAR gene can be deemed as candidate markers for feed intake and weight gain.

Electronic supplementary material

The online version of this article (10.1186/s40104-018-0261-1) contains supplementary material, which is available to authorized users.

Posthatch development of intestinal morphology and digestive enzyme activities in domestic pigeons (Columba livia)

The gastrointestinal tract plays an important role in studies of avian ontogenies because of its key function in nutrient intake. The pattern of intestinal development during postnatal growth in domestic pigeons (Columba livia), as an altricial bird, would be different from the pattern observed in precocial poultry. In this study, the intestinal morphology, mucosal enzyme activities, and pancreatic enzyme activities were determined from hatch to 14 d of age in pigeons. Rapid morphological development was observed immediately after hatching. Villus area and crypt depth increased in parallel in the duodenum and jejunum and more slowly in the ileum. Mucosal enzyme activities per gram of duodenum, jejunum, and ileum varied significantly with segment and age. There were also intestinal segment × age interactions, in which enzyme activity increased most dramatically in the jejunum as compared with the duodenum and ileum for sucrase and maltase activity from day of hatch to 8 d, and for alkaline phosphatase activity through 14 d. However, aminopeptidase-N activity increased most dramatically from day of hatch to 3 d in the ileum as compared with the duodenum and jejunum. Changes in carbohydrate-digesting enzymes activity in duodenum, jejunum, ileum, and pancreas are more pronounced than for protein-digesting enzymes activity from 3 d after hatching. Intestinal total enzyme activities exhibited a steady increase, which was highly correlated with BW. Pancreatic enzymes indicated patterns somewhat similar to those for intestinal enzymes. It was concluded that development of the absorptive area and the capacity for hydrolysis in the duodenum, jejunum, and ileum was rapid immediately after hatching, although rates of development were different in the 3 segments. Young pigeons differ from poultry, in whom intestinal and pancreatic digestive enzyme activities per gram of tissue are generally constant or decline during postnatal development. Also, the data seem consistent with the idea that intestinal hydrolysis may be a determining step in digestion and hence growth.

Expression profiles of somatotropic axis genes in lines of chickens divergently selected for 56-day body weight

The objective of this study was to evaluate mRNA expression of somatotropic axis genes in chickens divergently selected for high (HWS) or low (LWS) body weight at 56 days of age. Gene expression was measured on days 16, 18, and 20 of incubation, day of hatch, and days 3, 7, 28, and 56 posthatch. Pituitary growth hormone mRNA raised from prehatch to posthatch, with a similar profile in both lines. Liver growth hormone receptor (GHR) mRNA was high during embryogenesis, declined to low levels at day 3 posthatch, and then increased to day 56. Expression of liver insulin-like growth factor 1 (IGF-1) mRNA increased sharply by day 28 in line HWS and day 56 in line LWS. Pectoralis major muscle GHR mRNA was greater in line LWS than HWS. Muscle IGF-1 mRNA declined during embryogenesis, increased posthatch, and declined after day 7. IGF-1 mRNA was 1,000-fold greater in embryonic muscle than embryonic liver. Muscle IGF-1 receptor mRNA was greater in line LWS than HWS posthatch. These results demonstrate that genetic selection for high or low body weight has altered the expression profiles of somatotropic axis genes in a line-, age-, and tissue-specific manner.

Limitations to wheat starch digestion in growing broiler chickens: a brief review

Starch digestibility may be suboptimal in broilers fed pelleted wheat-based diets. In the present review, the digestion and absorption process related to starch is presented, followed by a discussion of the effect of wheat characteristics and bird-related effects. Enzyme secretion or glucose absorption and metabolism have not been shown to be limiting factors. Suboptimal starch digestibility is primarily observed when a large proportion of wheat is included in the diet, and appears to be partly associated with characteristics of the wheat such as hardness and cell wall structure, which cause starch granules to remain entrapped in the protein matrix and the cell wall of the endosperm or aleurone layer. There are indications that low starch digestibility is negatively correlated with feed intake, and that such a feed over-consumption is linked to an under-developed gizzard.

Gene expression of nutrient transporters in the small intestine of chickens from lines divergently selected for high or low juvenile body weight

Nutrient transporters in the small intestine are responsible for dietary nutrient assimilation; therefore, the expression of these transporters can influence overall nutrient status as well as the growth and development of the animal. This study examined correlated responses to selection in the developmental gene expression of PepT1, EAAT3, SGLT1, and GLUT5 in the small intestine of chickens from lines divergently selected for 48 generations for high (HH) or low (LL) 56-d BW and their reciprocal crosses (HL and LH). Duodenum, jejunum, and ileum were collected from male and female chicks on embryonic d 20, day of hatch with no access to feed, and d 3, 7, and 14 posthatch. Total RNA was extracted, and nutrient transporter expression was assayed by real-time PCR using the relative quantification method. In comparing male and female HH and LL chicks, there was a mating combination x age x sex interaction for PepT1 expression (P < 0.001), a main effect of sex for EAAT3 (P < 0.05) and SGLT1 (P < 0.001) expression, and an age x sex interaction for SGLT1 expression (P < 0.001). These results demonstrate a sexual dimorphism in the capacity to absorb nutrients from the intestine, which has implications for the poultry industry with regard to diet formulations for straight-run and sex-separate grow-out operations. Results from comparing male LL, LH, HL, and HH chicks indicate that selection for high or low juvenile BW may have influenced the gene expression profiles of these nutrient transporters in the small intestine, which may contribute to the overall differences in the growth and development of these lines of chickens.

Expression analysis of growth and energy regulation-associated genes in two divergent chicken strains

We have studied differential expression of genes using cDNA arrays in the hypothalamic region of two divergent chicken lines, which differ in body weight and feeding behavior. Several transcripts from genes in metabolic networks as well as from retroviruses were differentially expressed.

Quantitative and qualitative feed restriction on growth characteristics of male broiler chickens

Four experiments were conducted to evaluate the quantitative and qualitative feed restriction on the performance of male broiler chickens. In the first experiment, broilers fed identical pelleted diets were feed-restricted from 5 to 42 d by giving 95, 90, or 85% of the feed consumed ad libitum by control birds the previous day. In a second experiment, broilers were fed pellet or mash diets from 1 to 7 wk. In Experiments 3 and 4, broilers were feed-restricted to 90% of the ad libitum intake of a control group during different intervals. Results from Experiment 1 indicated that live body weight at 42 d was significantly different between unrestricted and restricted broilers (P < 0.01). A reduction in mortality was noted when feed intake was reduced (P < 0.05). In the second experiment, broilers fed mash had lower body weights and breast meat yields at 42 and 49 d (P < 0.05). Cumulative mortality at 42 and 49 d was reduced in broilers fed mash (P < 0.05). Results from Experiment 3 indicated that body weight and mortality were not significantly different (P > 0.05) at 42 d across treatments. There was a significant (P < 0.01) linear improvement on feed conversion at 42 d due to duration of feed restriction. Breast meat yield at 42 d was less in broilers subjected to mild feed restriction (P > 0.05) (Experiments 3 and 4). Broilers appeared able to recover from mild feed restriction, and there was always an associated reduction in mortality.

Stunting syndrome in broilers: effect of stunting syndrome inoculum obtained from stunting syndrome affected broilers, on broilers, leghorns and turkey poults

Responses to stunting syndrome (SS) infective material obtained from affected broilers and administered per os were monitored for 3 wk in a fast-growing commercial broiler population, in slow-growing Leghorn chicks, and in turkey poults. At 2 and 3 wk, the size of the gastrointestinal tract (GIT) segments, the pH of the GIT contents, and the activities of digestive enzymes in the intestinal contents and of disaccharidases on the jejunum mucosae were determined. Inoculation affected the genetic stocks differently. In broiler chicks, growth and feed utilization were markedly reduced. In contrast, inoculation of Leghorns was accompanied by improved feed intake and growth rate. Performance of poults was affected only slightly, albeit significantly. The effect of inoculation on the pH of crop and intestinal contents in Leghorn chicks was opposite to that found in broiler chicks, i.e., a significant increase in the crop and small intestinal pH in the former vs a significant decrease in inoculated broilers. Although inoculation of the broiler chicks did not affect the pH in the proventriculus, in Leghorn chicks it was reduced by 25%. In poults, inoculation did not significantly affect GIT contents pH. The GIT segments were markedly enlarged in broiler chicks, whereas in Leghorn chicks the opposite trend was observed; namely, intestinal segment weights were significantly reduced. In poults, inoculation caused a reduction in the intestinal segments and gizzard weight at 3 wk. During this same period, the liver and pancreas relative weights were dramatically increased in broiler chicks. A higher relative heart weight at 2 wk was observed in broilers and poults; this trend persisted to Week 3 in poults but not in broiler chicks. In broiler chicks, a nonsignificant reduction was observed for all enzymes assayed at 3 wk and for chymotrypsin at 2 wk. In Leghorn chicks, inoculation was accompanied by a marked and significant increase in the activity of chymotrypsin during both periods. In poults, inoculation caused a marked increase in the activities of amylase during Week 2 and 3, and trypsin at 3 wk. Maltase and saccharase activities in the jejunum of broiler chicks were slightly depressed a t 2 and 3 wk, the depression being significant at 2 wk for maltase and at 3 wk for saccharase. In the Leghorn chicks, inoculation caused a twofold increase in the activities of both enzymes. As in Leghorns, inoculation of poults with SS infective material caused a marked increase in the activities of the disaccharidases. The different responses to SS inoculation in the different genetic stocks are discussed.

Long-term divergent selection for eight-week body weight in white Plymouth rock chickens

This paper provides an overview of results from a long-term (38 generations) selection experiment. Lines were developed from individual phenotypic selection for high or low body weight at 8 wk of age. Included are data for the selected lines, sublines in which selection was relaxed, crosses of the selected lines, and sublines in which the sex-linked dw gene was introduced. Periodically (and in some cases every generation) data were obtained for unselected traits. These unselected traits included feed consumption and intake behavior, reproduction, allomorphic relationships, and metabolic, immunological, endocrine, and molecular factors. These responses have been integrated into a resource allocation paradigm.

Immunoresponsiveness of fast-growing chickens as influenced by feeding regimen

1. Immunoresponsiveness and disease resistance were measured in broiler males maintained on ad libitum feeding throughout or on alternate-day feeding. Alternate-day restrictions were started 1 and 2 d after hatch so that on any one day there were chicks fed and fasted. 2. Severity of response to E. coli challenge as measured by lesion scores, and mortality was greater for chicks fed ad libitum than those fed on alternate days. For chicks fed on alternate days, lesion scores were lower for those without access to feed for the 24-h period immediately after challenge. 3. Spleen weights, the indicator of response to marble spleen disease virus challenge, were higher for chicks fed ad libitum than those fed on alternate days. 4. Antibody response to sheep red blood cell antigen was not affected by feeding regimen. 5. Ratios of heterophils to lymphocytes were higher for chicks given access to feed for the previous 24-h period than for those fasted during the previous 24-h or those that had been fed ad libitum. 6. Results of this experiment suggest that for alternate-day feeding programs, vaccination be administered on the day that chicks are not fed.

Growth related traits in body weight selected lines and their crosses reared under different nutritional regimens

1. Four populations--two that had undergone 37 generations of selection for high (HH) and low (LL) body weight, and reciprocal crosses between them (HL and LH) were fed two diets differing in protein and energy. Diet A, under which selection had been made, contained 200 g protein and 11.23 MJ/kg. Diet E contained 240 g protein and 13.16 MJ/kg. 2. Body weight and feed efficiency were measured weekly from hatch to 56 d of age at which time oesophagus, abdominal fat pad, heart, liver and lungs were removed and weighed. At 35 d of age chicks were inoculated with sheep erythrocytes (SRBC) and antibody titre was measured 6 d later. 3. Chicks fed diet E were heavier than those fed diet A. HH chicks were heavier than LL chicks with HL and LH chicks intermediate to the parental lines. LH chicks were heavier than HL ones reflecting large maternal effects. 4. Food efficiencies among stocks and diets were consistent with those for body weight, with HH > LH > HL > LL and E > A. Relative differences between diets were similar across ages and heterosis for food efficiency was about 15%. 5. Relative to body weight, oesophagus and liver weights were heavier in chickens fed diet A than fed diet E. The pattern reversed for abdominal fat pad. 6. Antibody to SRBC antigen was greater in the crosses than in line HH and in cross HL than line LL, with heterosis of 70%.