255 Effect of Altosid-infused supplement on fly emergence and supplement intake in grazing cattle in Western Canada.

Abstract This study evaluated the effect of Altosid®-infused supplement on cattle at Vermilion, AB (VAB) and Brandon, MB (BMB), over 52-d and 74-d, respectively. The study focused on supplement intake, body performance, fly emergence from dung pats, and S-Methoprene (SMP) residual concentrations in feces. Each site had a group of females assigned to either a conventional supplement (Control) or an Altosid-infused supplement (Treated). Cow-calf pairs at VAB (n=50; 25/treatment) and replacement heifers at BMB (n=30; 15/treatment) were randomly assigned to treatment groups. The subjects at each site were weighed on two consecutive days at the start and end of the trials. Ultrasound measures of backfat and rumpfat thickness were collected at the beginning and end of the trial. Each group was assigned an automatic feeding unit to collect supplement intake, which was available ad libitum. At the Vermilion site, 20 random dung samples were collected per group at the start and end of the trial. Fecal samples were collected directly from rectum of each animal at the end of the trial. The residual fecal S-Methoprene concentrations in the dung pats were analyzed from 10 subjects with the greatest average supplement intake. Data was analyzed using PROC MIXED model in SAS, which accounted for treatment effects and treatment × site interaction, with initial BW as covariate. The relationship between supplement intake and fecal SMP residue was assessed using PROC CORR in SAS. Average daily gain and ultrasound measures of body composition did not differ (P > 0.05) between treatments at both sites. The average supplement intake in the Control (0.11 ± 0.05 kg/day) and the Treated (0.22 ± 0.05 kg/day) groups did not differ (P = 0.07) at BMB but were different at VAB where the treated group (0.38 ± 0.03 kg/day) had greater (P < 0.01) average intake compared to the control group (0.11 ± 0.03 kg/day). The average SMP concentrations in the feces were 0.16 ± 0.04 and 0.19 ± 0.05 ppm at VAB and BMB, respectively. The correlation between supplement intake and fecal SMP concentrations was positive but weak in BMB (r = 0.23;p = 0.52) but was moderate (r = 0.50; p = 0.14) for VAB. Before administering SMP treatment, more flies (P = 0.03) emerged from the dung pats sampled from the Treated group (68 ± 11 flies) compared to flies that emerged from the Control group’s (32 ± 11 flies) dung pats. However, after SMP treatment, fewer (p = 0.0007) flies emerged from the Treated group (64 ± 30) compared to the Control group (243 ± 30). The study results show that the Altosid-infused supplements effectively disrupt the lifecycle of flies by reducing the number of emerging flies in manure without adversely affecting cattle performance.