Abstract
Simple SummaryHigh egg production in laying hens can negatively affect their skeletal system, which serves as a reservoir of minerals. Intense bone metabolism due to eggshell production in laying hens can lead to bone loss and subsequent fractures. Spent laying hens’ meat can be also used as raw material for the manufacture of processed products. Alpha-ketoglutarate (AKG), a precursor of amino-acid glutamine, effectively improves growth performance, bone metabolism, immunity, and alleviate intestinal mucosal damage. The aim of this experiment was to assess the effect of dietary AKG supplementation on performance, serum hormonal parameters, intestine structure, bone parameters, articular cartilage degradation and characteristics of meat quality of laying hens with a mature skeletal system. The results of our study showed that dietary AKG supplementation did not influence feed intake, weight gain, or laying performance, but improved bone metabolism, increased bone collagen synthesis. Moreover, dietary AKG significantly decreased the cholesterol content of breast muscle. The results showed that AKG can be a valuable feed supplement, positively influencing the bone health status and welfare of laying hens.The aim of the experiment was to assess the effect of dietary alpha-ketoglutarate (AKG) supplementation on performance, serum hormonal indices, duodenum and jejunum histomorphometry, meat quality characteristics, bone quality traits and cartilage degradation in laying hens with a mature skeletal system. Forty-eight 30 week-old Bovans Brown laying hens were randomly assigned to a control group or the group fed the basal diet plus 1.0% AKG. The experimental trial lasted 30 weeks. The supplementation of AKG increases blood serum content of leptin, ghrelin, bone alkaline phosphatate and receptor activator of nuclear factor kappa-Β ligand, while osteoprotegerin and osteocalcin decrease. While dietary AKG was given to laying hens negatively influenced villus length, crypt depth, villus/crypt ratio and absorptive surface area in duodenum and jejunum, these changes have no effect on feed intake, weight gain, nor laying performance. In breast muscles, no significant changes in skeletal muscle fatty acid composition were observed, however, a higher shear force and decreased cholesterol content following AKG supplementation were noted, showing the improvement of muscle quality. While dietary AKG supplementation did not affect the general geometric and mechanical properties of the tibia, it increased collagen synthesis and enhanced immature collagen content. In medullary bone, an increase of bone volume fraction, trabecular thickness, fractal dimension and decrease of trabecular space were observed in AKG supplemented group. The trabeculae in bone metaphysis were also significantly thicker after AKG supplementation. AKG promoted fibrillogenesis in articular cartilage, as indicated by increased cartilage oligomeric matrix protein immunoexpression. By improving the structure and maintaining the proper bone turnover rate of highly reactive and metabolically active medullar and trabecular bones AKG showed its anti-osteoporotic action in laying hens.
Highlights
About 30% of laying hens, artificially selected for increased egg output, suffer excessive bone loss and fracture, which are mainly detected after slaughter [1]
Even though our experiment lasted for 30 weeks, similar results were obtained in a previous study in which hens were supplemented with 1% glutamine for a period of 56 days and feed intake was unaffected [35]
One previous study showed that broiler chickens fed a diet supplemented with 1% glutamine weighed significantly more compared to those in the control group and those in groups fed diets supplemented with 0.5, 1.5 or 2% glutamine
Summary
About 30% of laying hens, artificially selected for increased egg output, suffer excessive bone loss and fracture, which are mainly detected after slaughter [1]. The incidence of bone loss and fractures is determined by genetics and strain of hen, the housing system, methods of depopulation and nutrition [5,6,7]. Bone breakage due to osteoporosis during processing reduces the marketability of spent laying hens and increases the need to develop humane on-farm killing methods to support alternative ways of disposing of the spent hens [8]. Proper bone metabolism is an important aspect of the welfare of laying hens [9,10]
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