Dietary β-glucan influences the expression of testicular aquaporins, antioxidative defence genes and sperm quality traits in endangered golden mahseer, Tor putitora (Hamilton, 1822)

Higher intake of β-glucan impairs reproduction in a female teleost, Tor putitora (Hamilton, 1822)

Although the immuno-modulatory and stress-relieving properties of β-glucan is well elucidated in humans and other animal models, including fish, its role as a dietary supplement on reproduction is extremely scarce. Therefore, in this study, adult female fish were fed one of four test diets having 0 (control), 0.5, 1, and 1.5% β-D-glucan for 130 days and its effect on reproductive performance, ovarian and liver histology, sex hormones, and transcript abundance of selected reproduction-related genes was assessed. Low dietary intake of β-glucan improved fertilization and hatching rates (p<0.05). The relative fecundity and percentage of spawning females were higher (non-significant) in 0.5% β-glucan-fed groups. Surprisingly, even after 130 days, spawning did not occur in 1.5% β-glucan-fed individuals. Irrespective of β-glucan intake, all the brooders recorded similar plasma 17β-estradiol and maturation-inducing hormone (p>0.05). Higher intake of β-glucan (1.5%) upregulated aromatase genes without a parallel increase in 17β-estradiol. However, plasma vitellogenin increased with increasing β-glucan up to 1.0% then declined at 1.5% (p<0.05). The fish that received control, 0.5, and 1.5% β-glucan recorded similar vitellogenin levels in their plasma. Significantly higher plasma cortisol was evidenced in 1.5% β-glucan fed brooders (p<0.05). Histologically, higher follicular atresia and leaking of yolk material was evidenced in 1.5% β-glucan-fed group. Liver histology revealed the highest nutrient/lipid accumulation in fish that received 1.0% and 1.5% β-glucan. This study demonstrated the stimulatory effect of β-glucan intake at a lower dose (0.5%) on reproduction. However, higher intake (1.5%) could perturb normal reproductive function in a fish model and caused an increased number of atretic follicles leading to spawning/reproductive failure.

Transgenerational effects of β-glucan on thermal tolerance, growth performance, and immune gene expression of endangered cyprinid Tor putitora progeny

Nutritional programming signifies a process in which broodstock feeding approaches have long-term effects on the subsequent progeny. The present study aimed to elucidate whether supplementing golden mahseer, Tor putitora broodstock diets with β-glucan affects progeny growth performance, survival, thermal tolerance, and non-specific immunity. Initially, the growth performance of progeny produced from brooders fed with different levels of β-glucan was non-significant. However, on the 15th and 35th DPH, the maximum weight was observed in fry obtained from the brooders fed with 0.5% followed by 1.0% β-glucan. Furthermore, on 50th DPH, significantly higher weight was registered in the fry from the 0.5% β-glucan fed group while 1.0% β-glucan group had no transgenerational effect on growth. The condition factor of fry obtained from golden mahseer brooders fed with a 0.5% β-glucan diet was greater than the control and 1.0% β-glucan fed group. On the other hand, we did not find any significant transgenerational influence of β-glucan on the survival of the progeny. The thermal tolerance of fry produced from brooders fed with β-glucan was significantly modulated at both end-points (CT_max and CT_min). Expression of interleukin-1β was significantly up-regulated in fry obtained from β-glucan fed brooders. In contrast, the expression level of tumor necrosis factor-α was significantly higher only in fry produced from 1.0% β-glucan fed brooders. The expression of immunoglobulin light chain and serum amyloid A gene was significantly higher in fry produced from 0.5% β-glucan fed brooders. Overall results suggest that the dietary provisioning of β-glucan in golden mahseer brooders can be a strategy to produce healthy and robust fry in captivity for stock enhancement and conservation programs.