Striped bass (Morone saxatilis ) is an emerging new cultivar in the U.S. due to its ability to grow rapidly up to 1.3 - 2.3 kg (3 - 5 pounds) within a 24-month production cycle. The feasibility of cultivating this species has increased with successful domestication and many years of selective breeding for improved growth characteristics . Our previous research suggests that feeding striped bass every other day (3x/week) instead of daily (5x/week) to satiation may improve feed efficiency while having little impact on growth performance, particularly at larger body sizes of around 475 g. Here, we tested if feeding fish on alternate day at a reduced feeding rate could improve feed conversion efficiency and the amount of feed required to grow fish to market size relative to daily fed fish. We investigated the effects of feeding daily (7x/week) vs. alternate day (3-4x/week) on striped bass growout. Fish (500 g) were fed daily (2% BW/day) throughout 253 days. Fish on the alternate day feeding regime were fed at the following rates relative to daily fed fish: 50% for 0-89 days and 75 % for 90-253 days. A lternate day fish were subsequently shifted to daily feeding at 100% rate to that of the daily fed group until reaching 2 kg body size.
The mean weight (0.95 ± 0.008 kg) and length (41.26 ± 0.10 cm) of the daily fed fish were significantly higher than that of alternate day fed fish weight (0.72 ± 0.006 kg) and length (39.55 ± 0.09 cm) by day 89 . This significant difference in growth continued throughout the course of the study. After 253 days , the daily fed fish (1.97 ± 0.01 kg) were 22.8% larger than alternate day fed fish (1.52 ± 0.02 kg; p< 0.001). The alternate day fed fish caught up (compensatory growth) to daily fed fish sizes within 2.5 months (1.91 ± 0.03 kg) after being shifted to daily feeding. The overall feed conversion ratio (FCR) did not differ between feeding regimes (FCR 1.61). However, similar to our previous study, the FCR changed with fish age although at greater body size. FCR was 9.1% better in daily fed fish after the first 89 days (FCR 1.49 fed vs. 1.64 alt) and 5.8% after 187 days (FCR 1.47 fed vs. 1.56 alt). Interestingly, a t 253 days the FCR shifted and was 17% better in alternate day fed fish (FCR 2.0 fed vs. 1.66 alt). The FCR during the compensatory growth phase of alternate day fed fish was 2.4, making the overall plus the catchup period FCR 1.79. These data show that overall feed conversion does not differ between daily and alternate day fed striped bass but there is a negative e ffect on growth performance in alternate day fed fish. However, a shift to daily feeding can ameliorate the delayed growth response of alternate day feeding with extended growout time . The FCR of alternate day fed fish at 1.5 kg was notably better than daily fed fish when approaching sizes of 2 kg. More work is needed to fully understand the age effects on FCR in striped bass. These results show that 0.5 kg BW striped bass fed daily grew very rapidly to 2 kg (6 g/day) while fish fed under the current alternated day regime grew 4.6 g/day. Increasing the initial rate of feed on alternate days , where fish growth rates declined the most (0-89 days), is likely required to produce fish of comparable size as daily fed fish while providing potential for improved feed conversion.