Effect of fish oil and thyme on nutrient digestibility, chewing activity, and rumen metabolites of Mahabadi goat kids
This study was carried out to determine the effects of supplementing fish oil and thyme on nutrient digestibility, chewing activity and rumen metabolites in Mahabadi goat kids. Twenty-eight goat kids (BW = 17.8 ± 2.8 kg, 4 to 5 mo of age) were randomly assigned to 4 treatments: (1) basal diet (BD), (2) BD + 0.2% thyme essence, (3) BD +2% fish oil, and (4) BD + 2% fish oil and 0.2% thyme essence (DM basis of concentrate). Diets were formulated to meet the requirements recommended by NRC with forage (alfalfa and corn silage): concentrate ratio of 30:70 in TMR form. Animals were kept in individual pens with self-mangers for 94 d. Chewing activity in two 24-h periods was evaluated. During the last 7 d of the experiment, fecal samples were collected every morning around feeding time and acid insoluble ash (AIA) content was used as an internal marker to determine the apparent digestibility of nutrient digestibility. Ruminal fluid samples were taken from the rumen at 3 h after the morning meal the last day of the experiment to determine rumen concentration of ammonia nitrogen (NH3-N) and VFA. Rumen contents were sampled 5 times during the trial to measure ruminal protozoa and pH. Protozoa counts were determined using light microscopic numeration with a hemocytometer. Protozoa and pH data were analyzed by MIXED model procedure and rumen nutrient digestibility, chewing activity, NH3-N and VFA with GLM model procedure and adjusted Tukey-Kramer. Addition of fish oil decreased NDF digestibility, and increased ether extract digestibility versus the control (P < 0.05). Rumen liquor pH was not affected by treatments (6.11, 6.33, 6.20. and 6.23 respectively for treatments 1-4). Ruminal ammonia concentration decreased by 0.2% thyme essence (P < 0.05). Addition of thyme increased acetate concentration and acetate to propionate ratio (P < 0.1). It was also found that diets 2 and 3 significantly decreased protozoa count compared with diet 1 (P < 0.05). Time to eat (minutes per day) was not affected by treatments (P > 0.05), but chewing time significantly decreased by with diet 2 (P< 0.05). The results of this experiment indicate that supplementation of goat kid diet with fish oil and thyme changed nutrient digestibility and rumen metabolites.