A postbiotic from Aspergillus oryzae attenuates the impact of heat stress in ectothermic and endothermic organisms

Heat stress is detrimental to food-producing animals and animal productivity remains suboptimal despite the use of heat abatement strategies during summer. Global warming and the increase of frequency and intensity of heatwaves are likely to continue and, thus, exacerbate the problem of heat stress. Heat stress leads to the impairment of physiological and cellular functions of ectothermic and endothermic animals. Therefore, it is critical to conceive ways of protecting animals against the pathological effects of heat stress. In experiments with endothermic animals highly sensitive to heat (Bos taurus), we have previously reported that heat-induced systemic inflammation can be ameliorated in part by nutritional interventions. The experiments conducted in this report described molecular and physiological adaptations to heat stress using Drosophila melanogaster and dairy cow models. In this report, we expand previous work by first demonstrating that the addition of a postbiotic from Aspergillus oryzae (AO) into the culture medium of ectothermic animals (Drosophila melanogaster) improved survival to heat stress from 30 to 58%. This response was associated with downregulation of genes involved in the modulation of oxidative stress and immunity, most notably metallothionein B, C, and D. In line with these results, we subsequently showed that the supplementation with the AO postbiotic to lactating dairy cows experiencing heat stress decreased plasma concentrations of serum amyloid A and lipopolysaccharide-binding protein, and the expression of interleukin-6 in white blood cells. These alterations were paralleled by increased synthesis of energy-corrected milk and milk components, suggesting enhanced nutrient partitioning to lactogenesis and increased metabolic efficiency. In summary, this work provides evidence that a postbiotic from AO enhances thermal tolerance likely through a mechanism that entails reduced inflammation.

Optimizing fiber and protein levels in diet of lactating Murrah buffaloes to ameliorate heat stress: Effect on physiological status and production performance

The objective of study was to assess the outcome of feeding six total mixed rations (TMR), differing in NDF and protein content, for their synergistic effect on ameliorating heat load of lactating Murrah buffaloes evident through improved physiological and production performance. Thirty six lactating Murrah buffaloes (587 ± 12.3, MY 9 ± 2.2, Parity 2.5 ± 1.5) were arranged in a 3 × 2 factorial design with three levels of dietary NDF (30, 34.5 and 37% dietary NDF) and two levels of metabolizable protein (MP; 7.0% and 8.4%). Buffaloes were fed either of six dietary treatments: 30%NDF; 7.0% MP (CF1, as recommended), 34.5%NDF; 7.0% MP (MF1), 37%NDF; 7.0% MP (HF1), 30%NDF; 8.4% MP (CF2), 34.5%NDF; 8.4% MP (MF2) and 37%NDF; 8.4% MP (HF2). TMR offered with maize silage and respective concentrate for 90 days feeding trial. Fortnightly feed samples and weekly milk samples collection was done for analyses. Metabolic trial conducted in mid of experiment for estimating nutrient digestibility. Throughout the trial, THI level (79.7-83.8) denoted that buffaloes were exposed to stressful environment. Higher MP in diet reduced pulse rate in buffaloes as compared with lower MP diet. Rectal temperature was lower in Murrah buffaloes fed MF2 diet whereas; minimum breathing rate was recorded for high protein fed group. The MF2 diet increased dry matter intake (kg/d) by 2.7%, milk yield (kg/d) by 8.3% and feed efficiency (milk/DMI) by 7.2% as compared with CF1 group indicating reduced heat load. Increase in protein intake along with improved protein digestibility in MF2 group was recorded. Measured 6%FCM and ECM (kg/d), milk fat (%) and total solid (%) were higher in MF2 treatment group. Results revealed that 34.5% NDF and 8.4% MP have a positive influence on amelioration of heat stress in present experimental conditions.

A supplement containing multiple types of gluconeogenic substrates alters intake but not productivity of heat-stressed Afshari lambs

Thirty-two Afshari lambs were used in a completely randomized design with a 2 × 2 factorial arrangement of treatments to evaluate a nutritional supplement designed to provide multiple gluconeogenic precursors during heat stress (HS). Lambs were housed in thermal neutral (TN) conditions and fed ad libitum for 8 d to obtain covariate data (period 1 [P1]) for the subsequent experimental period (period 2 [P2]). During P2, which lasted 9 d, half of the lambs were subjected to HS and the other 16 lambs were maintained in TN conditions but pair fed (PFTN) to the HS lambs. Half of the lambs in each thermal regime were fed (top-dressed) 100 g/d of a feed supplement designed to provide gluconeogenic precursors (8 lambs in HS [heat stress with Glukosa {HSG}] and 8 lambs in PFTN [pair-fed thermal neutral with Glukosa]) and the other lambs in both thermal regimes were fed only the basal control diet (HS without Glukosa [HSC] and pair-fed thermal neutral without Glukosa). Heat stress decreased DMI (14%) and by design there were no differences between the thermal treatments, but HSG lambs had increased DMI (7.5%; < 0.05) compared with the HSC lambs. Compared with PFTN lambs, rectal temperature and skin temperature at the rump, shoulder, and legs of HS lambs were increased ( < 0.05) at 0700 and 1400 h. Rectal temperature at 1400 h decreased for HSG lambs (0.15 ± 0.03°C; < 0.05) compared with HSC lambs. Despite similar DMI between thermal treatments, ADG for HS and PFTN lambs in P2 was decreased 55 and 85%, respectively, compared with lambs in P1 ( < 0.01). Although the prefeeding glucose concentration was not affected by thermal treatment or diet, HSG lambs had increased postfeeding glucose concentration compared with HSC lambs ( < 0.05). In contrast to the glucose responses, circulating insulin was influenced only by thermal treatment; HS lambs had increased insulin concentration ( < 0.01) before feeding and decreased concentration ( < 0.05) after feeding compared with PFTN lambs. Heat-stressed lambs had decreased NEFA concentration before feeding ( < 0.01) but not after feeding relative to PFTN lambs. Although this nutritional strategy did not affect ADG, the lower rectal temperature in HSG lambs indicates that dietary inclusion of a mixture of glucogenic precursors can potentially benefit animal health during HS.

Nutritional strategies for managing the heat-stressed dairy cow

Heat stress results from the animal's inability to dissipate sufficient heat to maintain homeothermy. Environmental factors, including ambient temperature, radiant energy, relative humidity, and metabolic heat associated with maintenance and productive processes, contribute to heat stress. The focus of this article is to identify environmental and metabolic factors that contribute to excessive heat load, describe how disruption of homeothermy alters physiologic systems of the cow, and discuss nutritional modifications that help to maintain homeostasis or prevent nutrient deficiencies that result from heat stress. Changes in diet are needed during hot weather to maintain nutrient intake, increase dietary nutrient density, or to reestablish homeostasis. Formulation for adequate nutrient intake is challenging because of the competition between nutrient density and other needs for the cow, including energy density and adequate dietary fiber. Lower DMI during hot weather reduces nutrients available for absorption, and absorbed nutrients are used less efficiently. An excess of degradable dietary protein is undesirable because of energy costs to metabolize and excrete excess N as urea. Optimizing ruminally undegraded protein improves milk yield in hot climates. Mineral losses via sweating (primarily K) and changes in blood acid-base chemistry resulting from hyperventilation reduce blood bicarbonate and blood buffering capacity and increase urinary excretion of electrolytes. Theoretical heat production favors feed ingredients with a lower heat increment, such as concentrates and fats, whereas forages have a greater heat increment. Improved dietary energy density and the lower heat increment associated with the inclusion of dietary fat must be coupled with limitations to fat feeding to avoid ruminal and metabolic disorders. Numerous nutritional modifications are used for hot weather feeding; however, many need further investigation to achieve specific recommendations.