Impact of Clostridium butyricum on growth performance, ruminal fermentation, bacterial communities, and immune responses of goats fed milk replacer with varying fat levels

Abstract

The objective of this study was to evaluate the effect of Clostridium butyricum (CB) on growth performance, ruminal fermentation, immune response, and ruminal microbiota of goats fed milk replacer (MR) with varying dietary fat levels. Thirty-two male Saanen goats (initial body weight (BW) of 5.33 ± 1.03 kg, average age of 5 days) were used in a study with a 2 × 2 factorial arrangement. Four treatments were: 2 MR fat (MRF) contents (g/kg): 200 (low, LMRF) and 300 (high, HMRF) combined with 2 CB supplementation levels (0 vs. 0.5 g/d). The experiment was 55 days long, including 10 days for adaptation and 45 days for data and sample collection. The goats were individually housed in pens (1.0 × 1.0 m), with free access to water and fed ad libitum starter and alfalfa hay. The MR powder was mixed with water and fed three times daily at 0.65 %, 0.65 %, and 0.70 % of BW, respectively, in the first, second and third feeding, resulted in a total daily dose of 2 % of BW (dry matter basis). The CB product was dissolved in the MR and administered during the first feeding. Feeding HMRF versus LMRF to goats did not alter (P > 0.05) total feed intake but tended (P = 0.075) to increase final BW and increased (P = 0.025) average daily gain, thus decreased (P = 0.008) feed conversion ratio. The CB supplementation also decreased feed conversion ratio (P = 0.044) without interaction (P > 0.05) with MRF levels on BW, feed intake, average daily gain, and feed conversion ratio. Altering MRF did not affect (P > 0.05) blood metabolites such as blood urea nitrogen (BUN), glucose, cholesterol, and triglycerides, whereas the CB supplementation decreased BUN (interaction, P < 0.001), glucose (P = 0.007), and cholesterol (P = 0.030). In comparison with LMRF, HMRF reduced (P < 0.05) the concentrations of interleukin-1β and interleukin-6 in the absence of CB, whereas no differences (P > 0.05) were observed when CB was added. Moreover, the interleukin-10 concentration increased (P < 0.05) with CB supplementation in the LMRF diet; however, it did not differ (P > 0.05) when HMRF was fed. Supplementation of CB increased (P = 0.045) rumen concentration of total volatile fatty acids. Feeding higher levels of MRF increased the alpha diversity indices of amplicon sequence variants (P = 0.002) and Chao1 (P = 0.001), while CB addition increased (P = 0.034) Simpson index. At the phylum level, the HMRF vs. LMRF increased the abundances of Bacteroidetes (P = 0.012) and Campylobacterota (P = 0.037). Additionally, both MRF and CB supplementation influenced the genus abundances of Muribaculaceae_unclassified (P = 0.025), Christensenellaceae_R-7_group (P = 0.038), Prevotella (P = 0.001), and Firmicutes_unclassified (P = 0.001). These results indicated that increasing diet fat content via increasing milk replacer fat content or adding Clostridium butyricum can be an effective nutritional strategy to improve growth performance, immune response, and modulate the ruminal bacterial communities in pre-weaned goats. Whereas, further improvement of those measurements is limited by combining the supplementation of Clostridium butyricum with higher milk replacer fat.