3.2. Growth
Average Daily Gain. Average daily gain was calculated over the following periods: d −3 to 7, d −3 to 14, d 7 to 14, d 14 to 21, d 21 to 28, d 28 to 35, d 35 to 42, and d −3 to 42. The mean growth over the periods is shown in
Table 2.
D −3 to 7. Controlling for the pen of origin as a random effect, the linear regression model showed that lambs in LLB gained more weight (+ 0.03 kg/d; 95% CI: −0.0002 to 0.07;
p = 0.049) compared to lambs in CON (
Table 2;
Figure 1). When evaluating for non-inferiority, the bottom 20th percentile for growth was 0.124 kg/d for lambs in CON, and 18.5% (
n = 22) lambs in LLB were below this threshold. This was not different using a chi-square test (
p = 0.77), indicating that the LLB is non-inferior to the CON.
D 7 to 14. In the linear regression model, controlling for the pen of origin as a random effect, no differences were noted between the treatment groups (LLB vs. CON: −0.01 kg/d; 95% CI: −0.04 to 0.02;
p = 0.71) (
Table 2). The bottom 20th percentile for growth was 0.171 kg/d for lambs in CON, and 24.6% (
n = 29) lambs in LLB were below this threshold. This was not different using a chi-square test (
p = 0.25), indicating that the treatment is non-inferior to the control.
D −3 to 14. No differences were found with respect to growth over this period (LLB vs. CON 0.01 kg/d; 95% CI: −0.005 to 0.03;
p = 0.17) (
Table 2;
Figure 2) using a linear regression model and controlling for the pen of origin. Furthermore, the bottom 20th percentile for growth was 0.145 kg/d for lambs in CON, and 14.4% (
n = 17) of lambs in LLB were below this threshold. This was not different using a chi-square test (
p = 0.28), indicating that the treatment is non-inferior to the control.
D 14 to 21. Lambs in LLB gained less than those in CON (LLB vs. CON: −0.03 kg/d; 95% CI: −0.05 to −0.003;
p = 0.02) (
Table 2;
Figure 3). The bottom 20th percentile for growth was 0.143 kg/d for lambs in CON, and 30.3% (
n = 36) lambs in LLB were below this threshold. This was not significantly different using a chi-square test (
p = 0.09), indicating that the treatment is non-inferior to the control.
D 21 to 28. In the linear regression model, controlling for the pen of origin as a random effect, no differences were found between groups (LLB vs. CON: 0.01 kg/d; 95% CI: −0.01 to 0.03;
p = 0.55) (
Table 2). The bottom 20th percentile for growth was 0.057 kg/d for lambs in CON, and 20.2% (
n = 24) lambs in LLB were below this threshold. This was not different using a chi-square test (
p = 0.95), indicating that the treatment is non-inferior to the control.
D 28 to 35. No differences were found between groups with respect to growth over this period (LLB vs. CON: 0.01 kg/d; 95% CI: −0.01 to 0.03;
p = 0.36) (
Table 2). The bottom 20th percentile for growth was 0.171 kg/d for lambs in CON, and 21.4% (
n = 25) lambs in LLB were below this threshold. This was not different using a chi-square test (
p = 0.46), indicating that the treatment is non-inferior to the control.
D 35 to 42. In the linear regression model, controlling for the pen of origin as a random effect, no differences were found between groups (LLB vs. CON: −0.002 kg/d; 95% CI: −0.03 to 0.02;
p = 0.87) (
Table 2). The bottom 20th percentile for growth was 0.086 kg/d for lambs in CON, and 23.3% (
n = 27) lambs in LLB were below this threshold. This was not different using a chi-square test (
p = 0.69), indicating that the treatment is non-inferior to the control.
D −3 to 42. No differences were found between groups (LLB vs. CON: 0.005 kg/d; 95% CI: −0.01 to 0.02;
p = 0.43) (
Table 2) using a linear regression model and controlling for the pen of origin as a random effect. The bottom 20th percentile for growth was 0.154 kg/d for lambs in CON, and 21.2% (
n = 25) lambs in LLB were below this threshold. This was not different using a chi-square test (
p = 0.80), indicating that the treatment is non-inferior to the control.
Body weight at different measurement timepoints. Body weights for each individual lamb were taken at d −3, 7, 14, 21, 28, 35, and 42 relative to enrollment. This was assessed using a repeated measures linear regression model with lamb ID as a random effect, pen and baseline weight included as fixed effects, and with the treatment by day interaction also included as a fixed effect. Treatment (p = 0.30) and the interaction term between treatment and day of weighing (p = 0.57) were not significant; however, the day of weighing was significant (p < 0.0001).
3.3. Scrotal Site Assessment
Erythema, swelling, site temperature score, and target appearance and feel. At d 7, no differences were noted with respect to the presence of erythema (1.7% in CON vs. 0.8% in LLB; p = 0.62) and swelling (0% in CON vs. 0.8% in LLB; p = 1.00) using a Fisher’s exact test. Beyond d 7, none of the enrolled lambs had erythema or swelling. Furthermore, none of the lambs had an elevated site temperature score, whereas all lambs that had tissue distal to the target area presented with tissue that was shriveled and/or cold at each of the timepoints evaluated.
Tissue temperature above the band.
Table 3 below highlights the tissue temperature that was above the band application site. On d 14, it was found that lambs in LLB had a lower temperature above the band application site; however, no other differences in temperature at the other timepoints were noted.
Presence of the band with tissue distal to castration site. The proportion of lambs in the different treatment groups with the presence of the band with tissue distal to the site of castration is presented in
Table 4. Differences were noted between groups with regard to timepoints in terms of casting success. Specifically, at d 21, the presence of the band with tissue distal to the target area tended to be different between groups (LLB vs. CON: Odds Ratio (OR): 1.82; 95% CI: 0.92 to 3.60;
p = 0.09) using a logistic regression model with the pen as a fixed effect. While a statistical tendency was found, using a
p-value of 0.05, these results would suggest the treatment is non-inferior to the control. Furthermore, at d 28, lambs in LLB had 2.06-times (95% CI: 1.22 to 3.47;
p = 0.007) greater odds of having tissue distal to the band compared to CON lambs at d 28 using a logistic regression model with the pen as a fixed effect, suggesting that this treatment is inferior at this timepoint when compared to the control at this timepoint. At d 35, lambs in LLB tended to have higher odds of having tissue distal to the band (OR: 1.95; 95% CI: 0.99 to 3.85;
p = 0.05) compared to CON; however, at d 42, no differences were noted between groups (
p = 0.37).
3.4. Tail Site Assessment
As all animals had successful casting of the tail by d 28, descriptive statistics are not presented from d 28 onwards for tail site assessment.
Erythema, swelling, site temperature score, and target appearance and feel. At d 7, no differences were noted between groups with respect to the presence of erythema (7.0% in CON vs. 10.1% in LLB; p = 0.49) and swelling (7.0% in CON vs. 4.2% in LLB; p = 0.36) using a chi-square or Fisher’s exact test. Beyond d 7, none of the enrolled lambs had erythema or swelling. Furthermore, none of the lambs had an elevated site temperature score, whereas all lambs that had tissue distal to the target area showed tissue that was shriveled and/or cold at each of the timepoints evaluated.
Tissue temperature above the band. No differences were noted with regard to the tissue temperature of the tail above the band at any of the measured timepoints (
Table 5).
Presence of the band with tissue distal to tail docking site. The proportion of lambs in the different treatment groups with the presence of the band with tissue distal to the site of castration is presented in
Table 6. No statistical differences were noted at any of the measured timepoints.