Longitudinal health outcomes for enteric pathogens in preweaned calves on Ohio dairy farms

Effects of supplementing direct-fed microbials on health and growth of pre-weaning Gyr × Holstein dairy calves

This study aimed to evaluate the effects of direct-fed microbials (DFM) on health and growth responses of pre-weaning Bos indicus × B. taurus (Gyr × Holstein) crossbred calves. Ninety newborn heifer calves [initial body weight (BW) 35 ± 4.0 kg] were used. At birth, calves were ranked by initial BW and parity of the dam and assigned to: 1) whole milk without DFM supplementation (CON; n = 30), 2) whole milk with the addition of 1.0 g/calf per day of a Bacillus-based DFM (BAC; n = 30), or 3) whole milk with the addition of 1.0 g/calf per day of BAC and 1.2 g/calf per day of Enterococcus faecium 669 (MIX; n = 30). Milk was fed individually during the study (77 d) and the BAC and MIX treatments were offered daily throughout the 77-d pre-weaning period. All calves were offered a starter supplement and corn silage starting on d 1 and 60 of age, respectively. Milk and starter supplement intake were evaluated daily, and BW was recorded on d 0 and at weaning (d 77). Diarrhea and pneumonia were assessed daily, and fecal samples were collected on d 0, 7, 14, 21, and at weaning (d 77) for assessment of the presence of bacterial and protozoal pathogens via qPCR. All data were analyzed using SAS (v. 9.4) with calf as the experimental unit and using single-df orthogonal contrasts (BAC + MIX vs. CON; BAC vs. MIX). Daily feeding of DFM, regardless of type, improved weaning BW. Odds ratio for occurrence of pneumonia was lower for DFM-supplemented calves, but occurrence of both did not differ between BAC and MIX calves. No Salmonella spp. or E. coli F41 were detected in any of the calves. The proportion of calves positive for E. coli F17 was greater for DFM calves on d 7 (92 and 96% vs. 81% for BAC, MIX, and CON, respectively), 21 (13 and 26% vs. 7% for BAC, MIX, and CON, respectively), and at weaning (48 and 35% vs. 22% for BAC, MIX, and CON, respectively). For C. difficile, more DFM calves were positive on d 7 (65 and 30% vs. 35% for BAC, MIX, and CON, respectively) and 14 (20 and 28% vs. 7% for BAC, MIX, and CON, respectively), but also greater for BAC vs. MIX on d 7. More CON calves were positive for C. perfringens on d 14 (14% vs. 3 and 8% for CON, BAC, and MIX, respectively) compared with DFM-fed calves. Incidence of calves positive for C. perfringens was greater in BAC vs. MIX on d 7 (50 vs. 18%), and greater for MIX vs. BAC at weaning (9 vs. 0%). For protozoa occurrence, a lower proportion of DFM calves were positive for Cryptosporidium spp. on d 7 (58 and 48% vs. 76% for BAC, MIX, and CON, respectively), but opposite results were observed on d 21 for Cryptosporidium spp. (3 and 11% vs. 0% for BAC, MIX, and CON, respectively) and Eimeria spp. on d 14 (7 and 8% vs. 0% for BAC, MIX, and CON, respectively) and 21 (50 and 59% vs. 38% for BAC, MIX, and CON, respectively). In summary, DFM feeding alleviated the occurrence of pneumonia, improved growth rates, while also modulating the prevalence of bacteria and protozoa in pre-weaning Gyr × Holstein calves.

The roles of short-chain fatty acids derived from colonic bacteria fermentation of non-digestible carbohydrates and exogenous forms in ameliorating intestinal mucosal immunity of young ruminants

Short-chain fatty acids (SCFA) are a class of organic fatty acids that consist of 1 to 6 carbons in length. They are primary end-products which arise from non-digestible carbohydrates (NDC) fermentation of colonic bacteria. They are the fundamental energy sources for post-weaning ruminants. SCFA represent the major carbon flux of diet through the gut microbiota to the host. They also play a vital role in regulating cell expansion and gene expression of the gastrointestinal tract (GIT). Recently, remarkable progresses have been made in understanding the immunomodulatory effects of SCFA and their interactions with the host. The processes involved in this study encompassed inflammasome activation, proliferation of lymphocytes, and maturation of intestinal mucosal immunity maturation. It is important to note that the establishment and maturation of intestinal mucosal immune system are intricately connected to the barrier function of intestinal epithelial cells (IEC) and the homeostasis of gut microbiota. Thus, insights into the role of SCFA in enteric mucosal immunoreaction of calves will enhance our understanding of their various regulatory functions. This review aims to analyze recent evidence on the role of SCFA as essential signaling molecules between gut microbiota and animal health. Additionally, we provide a summary of current literature on SCFA in intestinal mucosal immune responses of dairy calves.

Lactiplantibacillus plantarum A1, C1 and C10 Are Potential Probiotics Isolated from Pineapple Residual Silage

The production and consumption of pineapple creates large quantities of residues. Ensiling these residues might help to minimize the waste burden and meet the intensive feed demand for ruminants. Proper lactic acid bacteria (LAB) are not only responsible for pineapple residual silage fermentation, but might also deliver probiotics. The aim of this study was to isolate LAB strains with probiotic functions, and to enhance intestinal antioxidant capacity from naturally fermented pineapple residues. A total of 47 LAB isolates with gram-positive, catalase-negative, nonhemolytic properties were used for probiotic screening. Lactiplantibacillus plantarum (L. plantarum) A1, C1 and C10 were susceptible to rifampicin, gentamicin and erythromycin, did not contain virulence factor-coding genes and showed good tolerance to acid (pH 3.0), 0.5% bile salt and simulated gastric and intestinal fluid. Their hydrophobicity indices were 71.92%, 45.50% and 66.90%, respectively. All of them were able to adhere to bovine jejunum epithelial cells (BJECs) and to antagonize Escherichia coli F5 and Salmonella Dublin. These three LAB strains tolerated hydrogen peroxide and significantly decreased (p < 0.05) reactive oxygen species levels in BJECs. In addition, L. plantarum C1 and C10 significantly increased (p < 0.05) the total antioxidant capacity in BJECs in the presence of 200 μmol/L hydrogen peroxide condition. L. plantarum A1, C1 and C10 are potential probiotics isolated from pineapple residual silage. This study aims to promote pineapple residue’s utilization in the feed industry.

Molecular surveillance of rotavirus A associated with diarrheic calves from the Republic of Korea and full genomic characterization of bovine-porcine reassortant G5P[7] strain

Group A rotavirus (RVA) is the most common diarrhea-causing pathogen among humans and animals worldwide. Rotavirus infection in neonatal calves causes major problems in the livestock industry. This study aimed to determine the prevalence and genetic diversity of bovine rotavirus (BoRVA) infections in calves with diarrhea and to perform whole genome analysis of an unusual strain, designated as RVA/Calf-wt/KOR/KNU-GJ2/2020/G5P[7], that was detected in a 2-day-old diarrheic calf. From 459 diarrheic calves aged 1-40 days, fecal samples were collected and BoRVA infections were screened using real-time RT-PCR targeting VP6 gene. BoRVA was detected in 195 (42.4%) samples and was most prevalent in calves aged 1-10 days (47.2%). No significant difference in the BoRVA infection rate was observed between calves born in herds that were (42.1%) and were not (42.6%) vaccinated against BoRVA. A binomial regression analysis revealed that calves aged 1-10 days (95% confidence intervals [CI]:1.18-24.34; P = 0.000) and 11-20 days (95% CI: 0.76-16.83, P = 0.000) had a 5.37- and 3.58-fold higher BoRVA prevalence in comparison to those aged 31-40 days, respectively. The RVA-positive samples were subsequently subjected to amplification of the VP7 and VP4 genes for determining G and P genotypes. Overall, 45 (23.1%, 45/195) and 63 (32.3, 63/195) sequences for VP7 and VP4 were obtained. In this study, four G and three P genotypes were identified. G6 (86.7%) was the most prevalent genotype, followed by G8 (8.9%), G10 (2.2%), and G5 (2.2%). P[5] (92.1%) was the most frequently detected, followed by P[11] (6.3%), and P[7] (1.6%). The G6P[5] (82.2%) is the most common combination found in Korean native calves with diarrhea, whereas G6P[11] (4.4%) and G10P[11] (2.2%) had relatively low prevalence. G8P[5] (8.9%) was identified for the first time in diarrheic calves in the KOR. The uncommon strain KNU-GJ2 exhibited a G5-P[7]-I5-R1-C1-M2-A1-N1-T1-E1-H1 genotype constellation possessing a typical porcine RVA backbone, with the exception of the VP3 gene, which is derived from bovine. Phylogenetically, except for VP3, ten gene segments of KNU-GJ2 were closely related to porcine, porcine-like, and reassortant bovine strains. Interestingly, the VP3-M2 gene of KNU-GJ2 clustered with bovine-like strains as well as reassortant porcine and bovine strains. Comparison of the NSP4s within a species-specific region of amino acids 131-141 demonstrated that KNU-GJ2 belonged to genotype B with porcine RVAs; however, it differed from porcine RVAs by one to three amino acids. The present study is fundamental to understanding the epidemiology and genotypes of circulating RVAs throughout the KOR and underscoring the importance of continuous monitoring and molecular characterization of RVAs circulating within animal populations for future vaccine development.

Prevalence and genetic characterization of bovine coronavirus identified from diarrheic pre-weaned native Korean calves from 2019 to 2021

Bovine coronavirus (BCoV) is associated with severe diarrhea in calves, winter dysentery in adult cattle, and respiratory diseases in cattle. However, there is currently limited information regarding its molecular characterization in the Republic of Korea (KOR). Therefore, this study investigated the prevalence of BCoV in diarrheic pre-weaned calves (aged ≤60 days) and compared BCoV genome sequences identified globally. A total of 846 fecal samples were collected from calves with diarrhea across 100 beef farms in the KOR. The samples were divided into three groups based on age as follows: 1-10 days (n = 490), 11-30 days (n = 277), and 31-60 days (n = 79). BCoV infection was detected in 50 calves by real-time RT-PCR analysis. The results showed that the prevalence of BCoV was associated with calf age (P = 0.028) and was significantly higher in calves aged 31-60 days (odds ratio: 2.69, 95% confidence interval: 1.24-5.85; P = 0.012) than in those aged 1-10 days. Our findings show that BCoV is an important etiological agent of diarrhea in calves aged 31-60 days. Fifteen full genome sequences (2019-2021 variants) of the spike, hemagglutinin/esterase, and nucleocapsid were obtained from the 50 BCoV-positive samples. Phylogenetic analysis of each gene revealed that BCoVs circulating worldwide might have no boundary between enteric and respiratory tropisms, demonstrating the presence of three BCoVs groups: the classical, Asia/USA, and European. Initially, Korean BCoVs were originated from the USA, but diverged since the 1980s and rapidly evolved independently, unlike in other Asian countries. In this study, Korean BCoVs are more recent BCoVs and present relatively high nucleotide substitution rates in all genes compared with other BCoVs. Our results showed that the 2019-2021 variants undergo continuous genetic evolution and that there are genetic differences among globally distributed BCoVs.

Cryptosporidiosis

Cryptosporidiosis is a common cause of diarrhea among preweaned dairy calves. In the United States, the most common species of Cryptosporidium found in dairy calves is Cryptosporidium parvum, an important zoonotic species. Cryptosporidiosis is spread by fecal-oral transmission. Calves begin shedding the oocysts as early as 2 days of age, with peak shedding occurring at 14 days of age. Diarrhea generally starts 3 to 4 days after ingestion of the oocysts. Risk factors for the disease include large dairy farms, summer months, feeding of milk replacer, and early feeding of starter grain. Concrete flooring and appropriate cleaning of feeding utensils decreases the risk of disease.

Diarrhoea outbreak caused by coinfections of Cryptosporidium parvum subtype IIdA20G1 and rotavirus in pre-weaned dairy calves

Diarrhoea is one of the most important syndromes in neonatal calves. In industrialized nations with intensive animal farming, Cryptosporidium spp. and rotavirus are primary causes of calf diarrhoea, but the role of these and other enteric pathogens is not clear in China. In November and December 2018, a diarrhoea outbreak was identified in over 150 pre-weaned calves on a dairy farm in Heilongjiang Province, northeast China and approximately 60 calves died. To determine the cause of the outbreak, we analyzed 131 faecal samples collected from pre-weaned calves (0-2 months) during (n = 114) and after the outbreak (n = 17). Initially, 10 diarrheic samples during the outbreak and 10 non-diarrheic samples after the outbreak were screened for rotavirus, coronavirus, Escherichia coli K99 and Cryptosporidium parvum by using an enzymatic immunoassay (EIA). In addition, 81 other samples were tested specifically for rotavirus by EIA, and all 131 samples were analyzed for Cryptosporidium spp., Giardia duodenalis and Enterocytozoon bieneusi by PCR. The initial EIA analysis identified C. parvum (8/10) and rotavirus (5/10) as the dominant pathogens in calves during the outbreak, while both pathogens were detected at lower frequency after the outbreak (2/10 and 1/10, respectively). Further PCR analyses indicated that the occurrence of C. parvum infections in calves was significantly higher during the outbreak (75.4%, 86/114) than after the outbreak (11.8%, 2/17; odds ratio [OR] = 23.0), and was significantly associated with the occurrence of watery diarrhoea (OR = 15.7) and high oocyst shedding intensity. All C. parvum isolates were identified as subtype IIdA20G1. Among other pathogens analyzed, the overall prevalence of rotavirus, G. duodenalis and E. bieneusi was 19.8% (20/101), 38.9% (51/131) and 42.0% (55/131) in calves, respectively, without significant differences during and after the outbreak. Among the three pathogens, only the rotavirus infection was associated with diarrhoea in calves. More importantly, coinfections of C. parvum and rotavirus were significantly associated with the occurrence of watery diarrhoea in calves and were seen only during the outbreak. Thus, C. parvum subtype IIdA20G1 and rotavirus appeared to be responsible for this diarrhoea outbreak. Control measures should be implemented to effectively prevent the concurrent transmission of these enteric pathogens in pre-weaned dairy calves in China.