The utilization of probiotics in livestock diets is increasing because it can result in improved productivity. Bacillus spp. are gram-positive spore-forming bacteria that are resistant to heat, cold, acid, and digestive enzymes (Carlin, 2011;Casula & Cutting, 2002). Although they cannot colonize the intestinal tracts of animals, they can have beneficial effects on productivity. Various studies have been conducted to clarify the effects of Bacillus spp. supplements. When supplied in pig feed, Bacillus subtilis LS 1-2 suppressed the levels of Clostridium spp. and Coliforms in the pigs' intestines and improved their growth performance (Lee et al. 2014). Broiler productivity was also improved by the addition of Bacillus subtilis UBT-MO 2 to their feed (Zhang et al. 2013). Sun et al. (2011) reported that the supplementation of Bacillus subtilis natto improved calf growth and development of the rumen. In lactating cows, supplementation with B. subtilis natto increased milk yields and the concentrations of propionic acid in the rumen (Sun et al. 2013). Supplementation with B. subtilis DSM15544 (B. subtilis C-3102) increased not only milk yields, but also milk protein levels, total solids, and milk energy secretion (Souza et al. 2017).These effects of B. subtilis supplementation in dairy cows were examined using Holstein-Friesians, which are farmed in cool temperate regions and are characterized as high-yielding and high feed intake cows. These characteristics lead to high heat production, accounting for 30% of the energy intake (Coppock, 1985). However, this high heat production makes the animals vulnerable to heat stress (Galán et al. 2018). On the other hand, in tropical regions such as Southeast Asia, crossbreeds between Holstein-Friesians and Bos indicus are mainly used in dairy production, even though they are less productive. These crossbreeds are suitable for tropical regions because B. indicus has a lower metabolic rate and is more resistant
The effect of the transition from a conventional milking (CM) system in a tie-stall barn to an automated milking (AM) system specialized for a tie-stall barn on milk yield, milk composition, teat-end score, body condition score (BCS), and lying time was evaluated. This study was conducted at a commercial dairy farm from À15 to 153 days after the installation of the AM system. Lactating cows milked with the CM system (average 85 heads) were gradually transitioned to the AM system, and finally, 57 heads were milked with the AM system. No obvious effects of the milking system on milk yield, milk components, BCS, and daily lying time were found based on comparisons between CM and AM cows in the same herd under the same situation of twice-daily milking. The linear mixed-effects model for teat-end scores showed higher scores for front than for rear teats, and small but negative estimates for independent variables of the day after AM, indicating worse teat-end condition for front than for rear teats and improvement of the condition with increased time since AM.
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