Application of a bacillus subtilis product as probiotic supplementation for health promotion and enhancement of production efficiency in dairy cattle

Abstract

In tropical smallholder dairy farms, where the Temperature Humidity Index (THI) is always > 72, the THI threshold for environmental heat stress and nutrition in terms of low quantity and quality of roughages have been highlighted as significant constraints to enhance reproductive performance and milk production. These cause an economically relevant problem in the dairy industry globally, not only in tropical countries.Factors involving environmental management to minimize heat stress and B. subtilis probiotic supplementation in feeding management to improve nutrient utilization are needed to study to promote health and enhance production efficiency in smallholder dairy systems. Therefore, the studies were conducted on smallholder dairy farms membered with dairy cooperatives in Chiang Mai, Thailand. In the first study, the impacts of environmental factors, barn structure characteristics, and farm management factors on reproductive performance were evaluated. A retrospective cohort study using data of cows from 125 farms collected from May to August 2014. The THI values ranged from 80.6 (temperature = 30°C, relative humidity = 64%) to 88.8 (temperature = 38.2°C, relative humidity = 48%). All temperatures measured outside were higher than the temperatures measured inside, ranging from 0.1 to 7.9°C. Both days to first insemination and days open were significantly related to calving season, roof materials, and some farm management factors, but only days open were related to differences in temperature between the inside and outside of barns. A decrease in pregnancy rate is more influenced by heat stress, especially a decrease in barns' temperature than estrus expression. In the second study, the effects of supplementation of B. subtilis on milk production were evaluated. Twenty-eight lactating crossbred Holstein-Friesian cows ( 89 ± 50 days in milk) on four farms were randomly assigned to treatment sequences in a replicated 4 × 4 Latin square design (from May to August 2016). Cows were individually fed 0 (CON), 0. 5 × 1011 (BS0. 5), 1 × 1011 (BS1) or 2 × 1011(BS2) colony-forming units (CFU) of B. subtilis/ day. Each 21 days experimental period included 13 days of adaptation followed by data collection from days 14 through 2 1 . Throughout the study, microclimatic conditions inside the barns were recorded to monitor THI. Milk weights were measured on days 14 and 21, and milk samples were collected on day 21. Whole blood samples were collected for hematological and biochemical analyses only during the first period of the study. The overall THI was higher than 80. THI was negatively related to milk yield (r = −0.52, P < 0.01), protein (r = −0.51, P < 0.01) and lactose (r = −0.49, P < 0.01). Milk yield increased (P < 0. 01) linearly as the level of B. subtilis increased. Cows fed B. subtilis at the level of 2 × 1011 CFU/ day produced 1. 7 kg/ day more milk, and the supplementation did not exert any negative effect on hematological and biochemical parameters. In the third study, the effects of supplementation of B. subtilis, vitamin E and selenium, or both on blood hematological, metabolic, and oxidative status parameters, the incidence of retained fetal membranes (RFM), and reproductive performance of transition cows were performed during July 2016 to January 2018. Thirty-two crossbred HolsteinFriesian cows in the transition period were used in a randomized design trial with a 2 × 2 factorial arrangement of treatments. Cows were randomly assigned to one of four treatments, including no supplementation (CON), single intramuscular injection of 1,000 mg of vitamin E (α-tocopherol acetate) in combination with 10 mg of selenium (sodium selenite) on day 21 before the expected calving date (ES), supplementing 0.5 × 1011 CFU of oral probiotic B. subtilis/cow per day between day −21 and day 21 relatives to calving (BS), or both ES and BS (ESBS). During the study, environmental conditions within the barn were measured. Body condition score (BCS) was determined, and blood samples were collected on day –28, –14, 0, 14, and 28 relatives to calving. The occurrence of RFM and reproductive performance, including days to the first insemination and days open, were collected for all cows. Most of the daily average THI ≥ 72. Approximately 38% of the time would be classified as mild heat stress (THI 72−79) and 51% moderate heat stress (THI 80−90). Cows fed BS tended to have higher glucose and lower βhydroxybutyrate (BHBA), creatinine, aspartate aminotransferase (AST), white blood cell (WBC), and monocytes than cows without BS. No differences in BCS, the incidence of RFM, and reproductive performance were observed. Summarizing, supplemental B. subtilis could reduce negative energy balance indicators by increasing glucose and lowering β-hydroxybutyrate and improving health parameters by keeping WBC and monocytes in a healthy status during the transition period. In the fourth study, the ability of B. subtilis to survive gastrointestinal transit after oral supplementation assessed in fecal samples is considered an inherent property of potential probiotics. Six rumen-fistulated goats were assigned to two treatments: basal rations (CON) and basal rations supplemented with B. subtilis probiotic product (BS) in a cross-over design. Each experimental period lasted 21 days. Body weights were recorded weekly throughout the experiment. On the last day of each experimental period, rumen fluid and fecal samples were collected. Bodyweight and rumen pH were found to be similar between dietary treatments. The goats that received BS had higher numbers of B. subtilis in fecal samples than CON. Therefore, it was concluded that B. subtilis met a prerequisite of probiotics to survive the passage through the gastrointestinal tract. The current result also provides a factual basis for future research involving any effects after supplementing probiotic B. subtilis in small ruminants.