Simple Summary: Providing high-quality feeds is required to maintain goat kids' health and improve their growth performance during their early growth phase, such as milk protein, fish meal, or extruded feed. The present study demonstrates that supplementation with 2% fermented feather meal–soybean meal product in the diet can promote the growth of goat kids by improving crude protein digestibility, diarrhea status, and immunity: therefore, it can completely replace the fish meal as a starter. These findings provide potential for practices of nutrition and immunity in goat kids, benefiting the livestock industry. This study investigates the effects of replacing fish meal with fermented feather meal–soybean meal product (FFSMP) from Bacillus amyloliquefaciens CU33 in the starter on growth performance, relative health performance, and digestibility of Alpine goat kids. In trial 1, thirty-two Alpine goat kids (male) were randomly assigned to dietary supplementation of 2% feather meal–soybean meal mix (FSM), 2% fish meal, or replacing fish meal with 50% or 100% FFSMP (FFSMP-50 or FFSMP-100) in starter (n = 8). In trial 2, sixteen goat kids were selected after trial 1 and used in this digestion trial which began from 12 weeks old. The treatments were the same as in trial 1 (n = 4). In trial 1, the growth performance of the FFSMP groups was better than the FSM group at 0 to 10 weeks (p < 0.05). The fecal consistency index of the FFSMP-100 group was better than the FSM group at 0 to 5 weeks and 5 to 10 weeks. In trial 2, the crude protein (CP) digestibility of the FSM group decreased (p < 0.05). In conclusion, dietary supplementation with 2% FFSMP in goat kids' diets can improve the growth performance, the CP digestibility, and diarrhea status, and it can completely replace the fish meal in starter diets. [ABSTRACT FROM AUTHOR]