Food Consumption, Digestibility and Conversion Efficiency in Bivoltine Silkworm (Bombyx mori L.) Hybrids under Temperate Conditions of Kashmir

DOI: 10.22161/ijeab.115.25

Abstract:
Feed conversion efficiency is a key physiological criterion for judging silkworm hybrids, yet little is known about how newly introduced CSR hybrids and regional hybrids utilise mulberry leaf under temperate conditions. This study compared food consumption, faecal egestion, growth rate, approximate digestibility (A.D.) and the efficiencies of conversion of ingested (E.C.I.) and digested (E.C.D.) food into body matter in four bivoltine Bombyx mori L. hybrids, NB4D2 × SH6, SKAU-R-1 × SKAU-R-6, CSR2 × CSR4 and CSR2 × CSR5. The hybrids were reared in a randomised complete block design with five replications during spring 2002 at Mirgund, Kashmir, on a single mulberry variety, Ichinose, and utilisation indices for the 4th and 5th instars were computed by the method of Waldbauer (1968). CSR2 × CSR5 recorded the lowest ingesta (18.70 g per larva, against 20.21 g in NB4D2 × SH6; C.D. = 0.984) and faecal egestion (6.87 g against 8.39 g; C.D. = 0.475) and the highest A.D. (63.177% against 58.466%; C.D. = 3.671). Growth rate was highest in CSR2 × CSR4 (0.1682) and CSR2 × CSR5 (0.1680), both significantly above the two conventional hybrids (0.1640–0.1645; C.D. = 0.0009). E.C.I. was numerically highest in CSR2 × CSR5 (24.736%) and E.C.D. in NB4D2 × SH6 (40.668%), but neither differed significantly among hybrids. The CSR hybrids thus achieved comparable conversion efficiency with lower leaf intake, lower egestion and higher digestibility, suggesting a lower leaf requirement per larva in commercial rearing. These indices can complement cocoon yield in breed evaluation for temperate regions.

Keywords:
Bombyx mori, bivoltine hybrids, food consumption, approximate digestibility, efficiency of conversion of ingested food, efficiency of conversion of digested food, Kashmir

Article Info:
Received: 10 Sep 2026; Received in revised form: 19 Oct 2026; Accepted: 28 Oct 2026; Available online: 31 Oct 2026

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