Abstract Enteric methane (CH₄) is both an energy loss from ruminants and an important emission from livestock production. Direct-fed microbials (DFMs) can modify rumen fermentation, but their effects on methane are inconsistent. This narrative review evaluates administered microbial interventions rather than naturally occurring taxa associated with low-methane phenotypes. A focused literature update prioritized in vivo studies that directly measured methane production, yield, or intensity. Animal evidence remains mixed. Propionibacterium-based DFMs, lactic acid bacteria, and conventional Saccharomyces cerevisiae products often show no change in daily methane, although strain- and diet-specific responses occur. Bacillus studies report both modest reductions and null responses. Recent approaches are more encouraging: a methanotroph-methylotroph consortium reduced daily methane by 12.0-14.4% in Hanwoo steers, and a rumen-derived Pichia membranifaciens strain reduced methane production, yield, and intensity in dairy cows at the higher tested dose. These findings are promising but still require independent and longer-term confirmation. Mechanistically, DFMs should not be described as eliminating ruminal H₂ production. A more defensible target is redirection of reducing equivalents and H₂/formate flux toward competing pathways, together with rumen stabilization or specific microbial antagonism. We therefore propose a function-first, evidence-tiered framework for DFM development. Farm-scale claims should require persistent changes in methane production, yield, or intensity without loss of intake, digestibility, health, or productivity.
Abstract Bovine Respiratory Disease (BRD) is a substantial cause of morbidity in cattle feedlots. Antimicrobial metaphylaxis is widely used to prevent disease and improve cattle growth performance, but its effects on the isolation of BRD-associated bacteria are not well defined. The aim of this study was to quantify the effects of three common metaphylactic drugs on the isolation frequency of members of the Pasteurellaceae throughout the feeding period. Upon feedlot arrival, cattle at high risk of developing BRD (n = 246) were randomized into four treatment groups: control, florfenicol, ceftiofur, and tulathromycin. Deep nasal swabs were collected upon arrival, approximately 1 month on feed, and prior to harvest (∼245 days on feed). Bacteriological culture was performed on all swabs, and colonies with morphology consistent with BRD-associated bacteria were subjected to MALDI-TOF MS for final confirmation. Nasal shedding prevalence over time was modeled with GEE multinomial logistic regression. An overall metaphylaxis effect was observed (p < 0.01). Pasteurellaceae nasal shedding prevalence did not differ significantly between experimental groups at one month on feed. By contrast, florfenicol-treated cattle had a greater proportion of samples without isolation than ceftiofur-treated cattle (10% versus 2%, p < 0.05). At the end of the feeding period, tulathromycin- and florfenicol-treated cattle had the least proportion of Pasteurellaceae isolates (28% and 32%, respectively, p < 0.05). Taken together, our findings highlight the differing effects of metaphylactic drugs in decreasing the nasal prevalence of bacterial pathogens in high-risk feedlot cattle.
Abstract A total of 568 sows (Line 1050, PIC Genetics, Hendersonville, TN) and their litters (PIC 337 × 1050) were used to evaluate the effects of United States grain sorghum compared to corn in lactation diets on sow and litter performance. Sows, in four separate farrowing groups (approximately 142 ± 1 sows per group), were moved into farrowing rooms and blocked by parity on d 112 ± 1 of gestation. Sows were assigned to one of three dietary treatments, consisting of diets with corn, grain sorghum, or a 50:50 blend of both serving as the grain source. The grain sorghum used was tannin-free and sourced from the Texas and Oklahoma panhandles. Diets were formulated to be balanced for amino acids, minerals, and net energy. Corn and sorghum were given the same net energy value (2,672 kcal/kg). Sows were fed a wheat-based gestation diet, then hand-fed 0.90 kg of their treatment diet twice a day, starting 3 to 5 d pre-farrow, and were given ad libitum access from farrow until weaning (approximately d 19 of lactation). Particle size of grain and complete feed were analyzed. Grain sorghum was slightly finer than corn, reducing dietary particle size as sorghum inclusion increased; however, all diets remained within a 30 μm range. Replacing corn with grain sorghum in the diet did not affect sow weight, backfat, or caliper score change from entry to weaning. Feeding sows grain sorghum did not affect sow average daily feed intake, litter feed efficiency, or wean-to-estrus interval. There were no differences in total born or born alive. However, there was a decrease (linear P < 0.001; quadratic, P = 0.003) in the percentage of stillborn pigs with increasing grain sorghum in the diet. Also, the percentage of mummies increased and then decreased (quadratic, P = 0.001) as grain sorghum inclusion increased compared to corn. There were no differences in litter size or litter weight after cross-fostering (d 1) or at weaning. Preweaning mortality tended to decrease then increase (quadratic, P = 0.080) with increasing grain sorghum compared to corn in the diet. As grain sorghum increased, preweaning removals increased (linear, P = 0.046); however, no differences were observed in total removals and mortality. In conclusion, grain sorghum grown and harvested in the United States can replace corn in lactation diets with little impact on sow or litter performance.
Abstract The nursery phase is a challenging period in swine production, and automated monitoring of feeder use may provide additional information about piglet activity during early post-weaning. A YOLOv8n detector trained using whole-frame bounding boxes was used to classify video frames as at_feeder or not_at_feeder. These classifications were used to quantify pen-level feeder occupancy, defined as the percentage of analyzed frames in which at least one piglet had its head inserted into the feeder. Eighty PIC piglets weaned at 21 d were housed in 16 single-sex pens. Eight pens contained four piglets (0.39 m²/pig; 18.75 cm feeder length/pig) and eight contained six piglets (0.26 m²/pig; 12.5 cm feeder length/pig), resulting in two pen configurations that differed simultaneously in group size, floor-space allowance, and feeder-space allowance. Sex and pen configuration formed a 2 × 2 factorial arrangement with four pens per cell, and the 16 pens were distributed across four spatial blocks. Video was analyzed during three 24-h windows beginning at 0900 h on Day 1, the day of weaning, and on Days 4 and 7. On a balanced 2,000-frame within-recording validation set, the model achieved mAP@0.5 = 0.995 and an F1-score of 0.993 for both classes. A mixed model with spatial block as a fixed effect and pen as a random intercept identified an observation-window effect (P < 0.001) and a pen configuration × window interaction (P = 0.014). Sex and interactions involving sex were not significant. Occupancy was higher in six-piglet pens during the later observation windows. An illustrative sensitivity analysis showed that the later differences between pen configurations were compatible with the expected mathematical effect of group size on a presence-based occupancy measure. Average daily gain and feed disappearance did not differ by sex, pen configuration, or their interaction. Feed conversion ratio showed a sex × pen-configuration interaction (P = 0.010). In a secondary within-pen analysis, each additional hour of feeder occupancy was associated with 0.023 kg/pig greater feed disappearance over the temporally matched 24-h interval (95% confidence interval, 0.010 to 0.037 kg/pig; P = 0.003). Automated video analysis provided a high-throughput measure of pen-level feeder occupancy across the early post-weaning period, establishing a foundation for subsequent development of individual-level feeding measures.
Abstract Four thousand three hundred and forty-six gilts from 10 gilt developer rooms (DNA Line 241, DNA Genetics, Columbus, NE) were weaned at ∼21 days and assigned to either a control (CON) diet based on corn and soybean meal or a slow growth (SG) diet containing increasing levels of soybean hulls (up to 50% soybean hulls) starting at approximately 25 kg of body weight to evaluate if feeding increasing levels of soybean hulls (dietary fiber) would reduce gilt growth rate and improve first parity performance. Each room was an experimental unit. Feed and water were provided ad libitum. Growth, puberty indicators, and reproductive traits were assessed through first parity. Subsets of gilts were vulva scored (day 111 of age; 150 gilts per treatment), blood was sampled for hormone analysis (days 150 and 164 of age; 40 gilts per treatment), and evaluated by ultrasound for back fat (BF) and loin depth (LD). Data were analyzed in SAS 9.4 using the GLIMMIX procedure, with cohorts as the experimental unit. Gilts fed the CON diet were heavier (102.2 vs. 94.8 ± 2.26 kg; P < 0.01), had wider vulvas, and greater back fat (15.1 vs. 12.5 mm ± 0.28; P < 0.01) compared to SG gilts. Loin depth did not differ between treatments. Age at first breeding was slightly younger for CON (227.7 vs. 231.8 ± 4.09 days; P = 0.44), though not significant. Total pigs born (15.0 and 14.8± 0.21 pigs/sow, respectively) and weaned (13.0 and 12.9 ± 0.24 pigs per sow, respectively) at first parity were unaffected by diet. Feeding soybean hulls to growing gilts reduced growth rates and back fat delaying puberty onset without impacting first-parity total born and pigs weaned performance. These findings suggest soybean hulls can be a tool for managing gilt growth rates without compromising productivity.
