Comparative Study of the Productive Parameters of Two Breeds of the Bombyx mori Silkworm Fed Rhodotorula glutinis Yeast

In this study, a comparative approach was used with the aim of filling the knowledge gap regarding the productive and economic parameters of two native <i>B. mori</i> silkworm breeds (<i>Lines C</i> and <i>Z</i>) fed with different diets, namely mulberry leaves alone and mulberry leaves with <i>R. glutinis</i> yeast at two different concentrations (1 × 10⁹ and 1 × 10⁷ CFU/mL). The trifactorial experiment was carried out with 600 silkworms during the fifth instar, with 300 for each breed and 50 larvae per rearing tray. The larvae were randomly assigned into three feeding groups, with two replicates: in the control group (C), the larvae received ordinary mulberry leaves; in the first experimental group (RG-1), the larvae were given mulberry leaves supplemented with <i>R. glutinis</i> yeast at a 1 × 10⁷ concentration; and in the second experimental group (RG-2), the larvae received the same quantity of mulberry leaves as the C and RG-1 groups, but with <i>R. glutinis</i> yeast at a 1 × 10⁹ concentration. <i>Line C</i> larvae in the RG-1 group revealed higher values for most of the productive traits assessed. There was a positive and significant correlation between the weights and lengths of the larvae and the silk gland, the silk gland and the shell, the cocoon and the pupae and the shell, and the shell and the pupa size (<i>p</i> < 0.001). The steady decline in the parameters at a higher concentration suggests that <i>R. glutinis</i> positively influences a number of silkworm growth features at a recommended dosage of 1 × 10⁷; however, further research is required to more precisely identify the mechanisms involved.