ARTICLE FEED & ADDITIVE MAGAZINE November 2023 77 4.1. Animal Ethics Code Number All the procedures involved in this study involved the treatment of animals, including handling. Polygain™ feeding and data collection were approved by the La Trobe University Ethics Committee (Approval No. AEC20028) 4.2. Statistical Analysis Details The results were analyzed using IBM SPSS Statistics software Version 28.0, applying general linear model with milk yield, milk composition and methane concentrations as dependent variables and baseline period and intervention periods as fixed factors. Statistical significance was set at p < 0.05. RESULTS 1. Milk Yield Milk yield during the baseline collection period was observed to average 26.43 litres, per cow, per day (Figure 1). This increased significantly in the intervention phase of the trial to 28.54 litres per cow per day (p < 0.05). This increase represents an increased milk yield of 7.4% on average per cow per day during the intervention phase. 2. Methane Emissions The methane concentration detected in the baseline phase of the trial was a mean of 246.59 ppm (±4.15 SEM) (Figure 2a) and a median concentration of 202.96 ppm (±3.70 SEM) (Figure 2b). This concentration reduced significantly in the intervention phase of the trial to a methane concentration of 161.09 ppm (±4.34 SEM) and a median concentration of 140.51 (±3.86 SEM) (Figure 2a,b). This reduction represents a decreased methane concentration detected during the intervention phase of the trial of 30.8% change in the median methane concentration and 34.7% in the mean methane concentration. 3. Milk Composition There was no significant difference in protein Figure 1. Weekly milk yield during the baseline collection phase (week 1–3, Before Polygain™) and during the following 3-week intervention period (week 4–6, After Polygain™). * indicates statistical significance (p < 0.05). Figure 2. (a) Mean daily methane concentration during the baseline collection phase (week 1–3, before Polygain™) and during the following 3-week intervention period (week 4–6, After Polygain™). (b) Median daily methane concentration during the baseline collection phase (week 1–3, before Polygain™) and during the following 3iweek intervention period (week 4–6, After Polygain™). * Indicates statistical significance (p < 0.05).
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