Effect of Energy Restriction on Growth, Slaughter Performance,Serum Biochemical Parameters and Lpin2/WDTC1/mRNA Expressionof Broilers in the Later Phase

A comparative study to determine the effects of breed and feed restriction on glucose metabolism of chickens

The glucose metabolism of poultry draws wide attention as they have nearly twice the fasting blood glucose than that of mammals. To define the relationship between glucose metabolism and breed of chicken, the outcomes from different growth rate chickens showed that Arbor Acres (AA) broilers, a well-known fast-growing breed, had a lower fasting blood glucose concentration and glucose clearance rate when compared to Silky chickens, a Chinese traditional medicinal chicken with black skin and a slow growth rate. Moreover, AA broilers had a relatively slow rise in blood glucose in response to oral glucose solution than the Silky chickens on 21 and 42 d (P < 0.05), which is probably attributed to downregulated expression of pancreatic insulin (INS), and upregulated transcription of phosphoenolpyruvate carboxy kinase 1 (PCK1) and glucose transporter 2 (GLUT2) in the liver of AA broilers (P < 0.05). In response to feeding restriction from 7 to 21 d, both the fasting blood glucose and the response speed of AA broilers to oral glucose were increased on d 21 (P < 0.05), and the serum glucose concentrations after 3 weeks compensatory growth were improved by early feed restriction in AA broilers. Feed restriction could also upregulate the mRNA level of pancreatic INS on d 21 and 42, as well as decrease the expressions of PCK1, glucose-6-phosphatase catalytic (G6PC), and GLUT2 in the liver on d 21 (P < 0.05) when compared to the free feeding group. These results revealed that Silky chickens have a stronger capability to regulate glucose homeostasis than AA broilers, and feed restriction could improve the fasting blood glucose and the response to oral glucose of AA broilers.

Feed Restriction Improves Lipid Metabolism by Changing the Structure of the Cecal Microbial Community and Enhances the Meat Quality and Flavor of Bearded Chickens

Excessive fat deposition in full-fed Bearded chickens does not only reduce carcass yield but also causes consumer rejection of meat. Feed restriction (FR) is an effective method to save on feed cost, reduce carcass fat deposition, and improve meat quality. A total of 560 150-d Bearded chickens were randomly divided into seven groups (each with eight replicates of ten birds) for 40 days. The control group was fed with the basal diet ad libitum (CON), and the other six groups were fed with 90% of the feed intake (90% FI), 80% FI, 70% FI, 90% metabolizable energy (90% ME), 80% ME, and 70% ME of the CON, respectively. Compared to the CON group, FR increased meat yield, but the total weight of the Bearded chickens was slighter; 80% FI and 70% ME improved the relative lipid metabolism indices of chickens, especially the levels of triglycerides and total cholesterol in the plasma and liver (p < 0.05), and decreased calpastatin activity in the breast muscle (p < 0.05). Additionally, 16S rRNA sequencing of cecal microbial community indicated that an increase in the abundance of Hydrogenoanaerobacterium and Bacteroides plebeius was observed in the 80% FI group (p < 0.05), and an enrichment in Olsenella, Catabacter, and Lachnospiraceae were observed in the 70% ME group (p < 0.05) compared to the CON group. Moreover, compared to the CON group, the L * value of the breast muscle significantly decreased, and a * value significantly increased in the 80% FI group (p < 0.05). Notably, the concentrations of threonine, lysine, aspartic acid, glutamic acid, proline, and arginine and the activity of calpain in breast muscle increased in the 80% FI group more than in the CON group (p < 0.05), while valine, isoleucine, leucine, phenylalanine, lysine, alanine, tyrosine and proline decreased in ME restriction groups (p < 0.05). Taken together, our results indicated that 80% FI could improve lipid metabolism by changing the structure of the cecal microbial community, and the meat quality and flavor of the Bearded chickens in 80% FI group was improved with a promoted meat color score, flavor substances, and the calproteinase system.

Chicken CDS2 isoforms presented distinct spatio-temporal expression pattern and regulated by insulin in a breed-specific manner

The cytidine diphosphate diacylglycerol synthases (CDSs) gene encodes the cytidine diphosphate-diacylglycerol (CDP-DAG) synthase enzyme that catalyzes the formation of CDP-diacylglycerol from phosphatidic acid. At present, there are no reports of CDS2 in birds. Here, we identified chicken CDS2 transcripts by combining conventional RT-PCR amplification, 5′ rapid amplification of cDNA ends (RACE), and 3′ RACE, explored the spatio-temporal expression profiles of total CDS2 and the longest transcript variant CDS2-4, and investigated the effect of exogenous insulin on the mRNA level of total CDS2 via quantitative RT-PCR. Four transcripts of chicken CDS2 (CDS2-1, -2, -3, and -4) were identified, which were alternatively spliced at the 3′-untranslated region (UTR). Both total CDS2 and CDS2-4 were prominently expressed in adipose tissue, and exhibited low expression in liver and pectoralis of 49-day-old chickens. Regarding the spatio-temporal expression patterns of CDS2 in chicken, total CDS2 exhibited a similar temporal expression tendency with a high level in the later period of incubation (embryonic day 19 [E19] or 1-day-old) in the brain, liver, and pectoralis. While CDS2-4 presented a distinct temporal expression pattern in these tissues, CDS2-4 levels peaked at 21 d in the brain and pectoralis, while liver CDS2-4 mRNA levels were highest at the early stage of hatching (E10). Total CDS2 (P < 0.001) and CDS2-4 (P = 0.0090) mRNA levels in the liver were differentially regulated throughout the development of the chicken. Total CDS2 levels in the liver of Silky chickens were higher than that of the broiler in the basal state and after insulin stimulation. Exogenous insulin significantly down-regulated the level of total CDS2 at 240 min in the pectoralis of Silky chickens (P < 0.01). In conclusion, chicken CDS2 isoforms with variation at the 3′-UTR were identified, which was prominently expressed in adipose tissue. Total CDS2 and CDS2-4 presented distinct spatio-temporal expression patterns, that is they were differentially regulated with age in brain, liver, and pectoralis. Insulin could regulate chicken CDS2 levels in a breed- and tissue-specific manner.

Effects of Restricted Feeding on Growth Performance, Intestinal Immunity, and Skeletal Muscle Development in New Zealand Rabbits

Simple Summary

The high prevalence of gastrointestinal diseases in young rabbits is the major cause of impediment in the development of the rabbit industry. Presently, few companies have adopted methods of restricting feeding to improve the survival rate independent of the effect on their growth and development. To explore the effects of different feeding-restriction levels on the growth performance, intestinal immunity, and skeletal muscle development of meat rabbits, 198 New Zealand meat rabbits of 35 days old were selected and randomly divided into three groups: (1) a control group, (2) a 15% feeding restriction group, and (3) a 30% feeding restriction group, with 66 in each group with an equal number of males and females. The growth performance measurement and health-risk assessment indicators, measurement of digestive enzyme activity, immune and antioxidant indexes, and regulation mechanism were evaluated and explored. Finally, we found that a 30% feeding limit affected the growth and development of skeletal muscle in growing rabbits by regulating the PI3K/Akt signaling pathway.

Abstract

This study aimed to explore the effects of different feeding restriction levels on the growth performance, intestinal immunity, and skeletal muscle development of meat rabbits. Additionally, we studied whether complete compensatory growth could be obtained post 2 weeks of restricted feeding, in order to seek a scientific mode of feeding restriction. Each of three groups was exposed to 3 weeks of feeding restriction and 2 weeks of compensatory growth. The 15% feeding restriction showed a negligible effect on the final body-weight of the rabbits (p > 0.05), but significantly reduced the feed-to-weight ratio (p < 0.05); reduced diarrhea and mortality; and increased digestive enzyme activity and antioxidant capacity. However, a 30% feeding-restriction level substantially reduced the growth rate of the rabbits (p < 0.05), impaired skeletal muscle development, and showed no compensatory growth after 2 weeks of nutritional recovery. Additionally, immunoglobulin and antioxidant enzyme synthesis were impaired due to reduced nutritional levels, and levels of pro-inflammatory factors were increased during the compensation period. The IGF1 mRNA expression decreased significantly (p < 0.05), whereas MSTN and FOXO1 expression increased noticeably (p < 0.05). Moreover, protein levels of p-Akt and p-p70 decreased significantly in the 15% feeding restriction group. Overall, the 15% feeding limit unaffected the weight and skeletal muscle development of rabbits, whereas the 30% feeding limit affected the growth and development of skeletal muscle in growing rabbits. The PI3K/Akt signaling pathway is plausibly a mediator of this process.

Energy utilisation of broiler chickens in response to guanidinoacetic acid supplementation in diets with various energy contents

This experiment was conducted to investigate the effects of guanidinoacetic acid (GAA) on productive performance, intestinal morphometric features, blood parameters and energy utilisation in broiler chickens. A total of 390 male broiler chicks (Ross 308) were assigned to six dietary treatments based on a factorial arrangement (2×3) across 1–15 and 15–35-d periods. Experimental treatments consisted of two basal diets with standard (STD; starter: 12·56 MJ/kg and grower: 12·97 MJ/kg) and reduction (LME; starter: 11·93 MJ/kg and grower: 12·33 MJ/kg) of apparent metabolisable energy (AME) requirement of broiler chickens each supplemented with 0, 0·6 and 1·2 g/kg GAA. Supplemental 1·2 g/kg GAA decreased the negative effects of feed energy reduction on weight gain across starter, growing and the entire production phases (P<0·05). Energy retention as fat and total energy retention were increased when birds received LME diets supplemented with 1·2 g/kg GAA (P<0·05). Net energy for production (NEp) and total heat production increased in birds fed LME diets containing 1·2 g/kg GAA (P<0·05). A significant correlation was observed between dietary NEp and weight gain of broilers (r 0·493; P=0·0055), whereas this relationship was not seen with AME. Jejunal villus height and crypt depth were lower in birds fed LME diets (P<0·05). Serum concentration of creatinine increased in broilers fed LME diets either supplemented with 1·2 g/kg GAA or without GAA supplementation (P<0·05). Supplemental GAA improved performance of chickens fed LME diet possibly through enhanced dietary NEp. The NEp could be preferred over the AME to assess response of broiler chickens to dietary GAA supplementation.

Effect of early dietary energy restriction and phosphorus level on subsequent growth performance, intestinal phosphate transport, and AMPK activity in young broilers

We aimed to determine the effect of low dietary energy on intestinal phosphate transport and the possible underlying mechanism to explain the long-term effects of early dietary energy restriction and non-phytate phosphorus (NPP). A 2 × 3 factorial experiment, consisting of 2 energy levels and 3 NPP levels, was conducted. Broiler growth performance, intestinal morphology in 0–21 days and 22–35 days, type IIb sodium-phosphate co-transporter (NaP_i-IIb) mRNA expression, adenylate purine concentrations in the duodenum, and phosphorylated adenosine monophosphate-activated protein kinase (AMPK-α) activity in 0–21 days were determined. The following results were obtained. (1) Low dietary energy (LE) induced a high feed conversion ratio (FCR) and significantly decreased body weight gain in young broilers, but LE induced significantly higher compensatory growth in low NPP (LP) groups than in the high or medium NPP groups (HP and MP). (2) LE decreased the villus height (VH) in the intestine, and LE-HP resulted in the lowest crypt depth (CD) and the highest VH:CD ratio in the initial phase. However, in the later period, the LE-LP group showed an increased VH:CD ratio and decreased CD in the intestine. (3) LE increased ATP synthesis and decreased AMP:ATP ratio in the duodenal mucosa of chickens in 0–21 days, and LP diet increased ATP synthesis and adenylate energy charges but decreased AMP production and AMP:ATP ratio. (4) LE led to weaker AMPK phosphorylation, higher mTOR phosphorylation, and higher NaP_i-IIb mRNA expression. Thus, LE and LP in the early growth phase had significant compensatory and interactive effect on later growth and intestinal development in broilers. The effect might be relevant to energy status that LE leads to weaker AMPK phosphorylation, causing a lower inhibitory action toward mTOR phosphorylation. This series of events stimulates NaP_i-IIb mRNA expression. Our findings provide a theoretical basis and a new perspective on intestinal phosphate transport regulation, with potential applications in broiler production.

Three indel variants in chicken LPIN1 exon 6/flanking region are associated with performance and carcass traits

LPIN1 is a Mg(2+)-dependent phosphatidic acid phosphatase. Variation in chicken LPIN1 exon 6 and its flanking regions were identified and three indel variants in 6 breeds and their associations with performance traits were studied. Seven variants were detected from 6 breeds, which contained a synonymous tri-allelic variant (c.924A/T/C) and three indels. The exon 6 variants detected from chicken breeds were conserved among bird species. The indel variation frequency presented clear differences among breeds. Two coding indels (c.1014-1018del3 and c.1125-1138del12) were multiples of three nucleotides and maintained the open reading frames of LPIN1 proteins. However, they were predicted to result in the clear change of the RNA secondary structure of chicken LPIN1 exon 6 and LPIN1 protein conformation. The association analysis showed that c.871-15-22del6 variation had a significant effect on body weight at hatch (BW0) and 2 weeks (BW2); c. 1014-1018del3 variation had a significant effect on BW4, BW6, caecum length and gizzard weight (GW) traits; c.1125-1138del12 variation had a significant effect on BW12, shank length at 4 weeks (SL4), carcass weight, lactate dehydrogenase traits (LDH), glucose (GLU) and albumin (ALB) traits. The genotype combination for c.1014-1018del3 and c.1125-1138del12 also presented significant effects on SL4, SL8, GW, leg muscle weight, ALB, GLU and LDH. The study demonstrated that chicken LPIN1 has an important effect on body, carcass and organ weight, serum LDH, GLU and ALB level.

The expression characteristics of mt-ND2 gene in chicken

Subunit 2 of NADH dehydrogenase (ND2) is encoded by the mt-ND2 gene and plays a critical role in controlling the production of the mitochondrial reactive oxygen species. Our study focused on exploring the mt-ND2 tissue expression patterns and the effects of energy restriction and dietary fat (linseed oil, corn oil, sesame oil or lard) level (2.5% and 5%) on its expression in chicken. The results showed that mt-ND2 gene was expressed in the 15 tissues of hybrid chickens with the highest level in heart and lowest level in pancreas tissue; 30% energy restriction did not significantly affect mt-ND2 mRNA level in chicken liver tissue. Both the mt-ND2 mRNA levels in chicken pectoralis (p < 0.05) and hepatic tissues (p < 0.05) at 42 d-old were affected by the type of dietary fats in 5% level, while not in abdominal fat tissues. The expression of mt-ND2 in hepatic tissues was down-regulated with chicken age (p < 0.01). The interactive effect of dietary fat types with chicken age (p < 0.05) was significant on mt-ND2 mRNA level. The study demonstrated that mt-ND2 gene was extensively expressed in tissues, and the expression was affected by dietary fat types and chicken age.

Nutritional factors affecting abdominal fat deposition in poultry: a review

The major goals of the poultry industry are to increase the carcass yield and to reduce carcass fatness, mainly the abdominal fat pad. The increase in poultry meat consumption has guided the selection process toward fast-growing broilers with a reduced feed conversion ratio. Intensive selection has led to great improvements in economic traits such as body weight gain, feed efficiency, and breast yield to meet the demands of consumers, but modern commercial chickens exhibit excessive fat accumulation in the abdomen area. However, dietary composition and feeding strategies may offer practical and efficient solutions for reducing body fat deposition in modern poultry strains. Thus, the regulation of lipid metabolism to reduce the abdominal fat content based on dietary composition and feeding strategy, as well as elucidating their effects on the key enzymes associated with lipid metabolism, could facilitate the production of lean meat and help to understand the fat-lowering effects of diet and different feeding strategies.