Beet pulp substituted for corn silage and barley grain in diets fed to dairy cows in the summer months: feed intake, total-tract digestibility, and milk production

The responses of dairy cows to the substitution of beet pulp (BP) for grain or forage are not consistent, and heat stress may affect the response of dairy cows to this substitution. The effects of substituted BP for corn silage and barley grain on feed intake, performance, and ruminal parameters were evaluated using eight multiparous Holstein cows in a duplicated 4 × 4 Latin square design with 21-day periods. Cows were in mid-lactation (45.4 ± 3.6 kg/day milk production and 116 ± 10 days in milk) with an average BW of 664 ± 41.2 kg. Dietary treatments were as follows: 1) 0% BP (0BP, control, 38.5% barley grain, and 20.3% corn silage); 2) 12% BP (12BP, 32.5% barley grain, and 14.3% corn silage); 3) 18% BP (18BP, 29.5% barley grain, and 11.3% corn silage); and 4) 24% BP (24BP, 26.5% barley grain, and 8.3% corn silage). Cows were under mild heat stress and the average temperature-humidity index was 70.5; increasing BP caused a linear decrease in respiration rate (P < 0.01). Higher BP in the diet caused a linear increase in DM intake (P = 0.01) and NDF digestibility (P = 0.03). Dry and organic matter (OM) digestibilities tended to increase linearly with higher BP (P < 0.10). Milk yield, energy-corrected milk, protein, lactose, and fat production and content were not affected by the treatments. Increasing BP in the diet caused a linear decrease in feed efficiency and rumen ammonia (P < 0.05) and a tendency to a linear decrease in milk urea nitrogen (P < 0.10). Rumen pH and acetate to propionate ratio were not affected by the replacement. Total volatile fatty acid concentration in the rumen increased linearly with increasing the BP inclusion (P = 0.04). Acetate and butyrate (P = 0.07) proportion tended to increase, whereas propionate (P = 0.06) and isovalerate (P = 0.08) proportion tended to decrease linearly as BP was substituted for corn silage and barley grain. The results indicated that under mild heat stress condition, BP can be successfully substituted for barley grain and corn silage up to 24% of the diet without any negative effect on production and ruminal pH.

Direct exposure to mild heat stress stimulates cell viability and heat shock protein expression in primary cultured broiler fibroblasts

Fibroblasts produce collagen which is mainly essential for repairing tissue damage and maintaining the structural integrity of tissues. However, studies have given scientific evidence about harmful effect of thermal manipulation in fibroblast. Therefore, the aim of this study was to determine the mild heat stress temperature which increased broiler fibroblast viability. The experiment was divided into two groups (37 °C and 41 °C), and each group was divided into five subgroups based on different incubation times (6 h, 12 h, 24 h, 48 h, and 72 h) with three replications. In experimental group (41 °C), fibroblast viability increased significantly in 12 h but decreased in 72 h compared with control (37 °C). At 41 °C, live cell increased significantly in 24 h and then declined in 48 h as well as 72 h than control. Moreover, the S phase lengthened in shorter incubation time of experimental group compared with control. Protein and mRNA (HSP70, HSP60, and HSP47) expressions were significantly higher at 41 °C compared with 37 °C, but at the end of the experiment, HSP expression level was higher in both groups. Finally, this study recommended 41 °C as a mild heat stress temperature for increasing broiler fibroblast viability.

Mild heat stress induces hormetic effects in protecting the primary culture of mouse prefrontal cerebrocortical neurons from neuropathological alterations

Hormesis is a dose response phenomenon of cells and organisms to various types of stressors. Mild stress stimulates prosurvival pathways and makes the cells adaptive to stressful conditions. It is a widely used fundamental dose-response phenomenon in many biomedical and toxicological sciences, radiation biology, health science etc. Mild heat stress is an easily applicable hormetic agent that exerts consistent results. In the present investigations mouse cerebrocortical prefrontal neurons from E17 mouse embryos were grown in the laboratory on poly-L-lysine coated glass cover slips. The cells from the mild heat stressed group were subjected to a hyperthermic stress of 38 °C for 30 min every alternate day (i.e. mild heat stress was repeated after 48 h) up to the sixth day. After completion of twenty four hours of the final i.e. third exposure of the mild heat stress, the neurons were fixed for the cytochemical studies of neurofibrillary tangles, senile plaques, lipofuscin granules and Nissl substance. There was highly significant decrease in the neuropathological alterations (viz. deposition of Neurofibrillary tangles, deposition of senile plaques, accumulation of Lipofuscin granules) in the neurons from the mild heat stressed group as compared to control. Moreover, the Nissl substance was significantly preserved in the mild heat stressed group as compared to control. The results indicate that the applied mild heat stress (38 °C for 30 min) exerts beneficial effects on the prefrontal cerebrocortical neurons by slowing down the neuropathological alterations, suggesting the hormetic effect of the mild heat stress.

Are adult life history traits in oriental fruit moth affected by a mild pupal heat stress?

Thermal stress at one life stage can affect fitness at a later stage in ectotherms with complex life cycles. Most relevant studies have focused on extreme stress levels, but here we also show substantial fitness effects in a moth when pupae are exposed to a relatively mild and sublethal heat stress. We consider the impact of a 35°C heat stress of 2h in three geographically separate populations of the oriental fruit moth (OFM, Grapholita molesta) from northern, middle and southern China. Heat stress negatively affected fecundity but increased adult heat resistance and adult longevity. Fitness effects were mostly consistent across populations but there were also some population differences. In the Shenyang population from northern China, there was a hormetic effect of heat on female longevity not evident in the other populations. Adults from all populations had higher LT₅₀s due to heat stress after pupal exposure to the sublethal stress. These results highlight that the pupal stage is a particularly sensitive window for development and they have implications for seasonal adaptation in uncertain environments as well as changes in pest dynamics under climate warming.

The long-term effects of a life-prolonging heat treatment on the Drosophila melanogaster transcriptome suggest that heat shock proteins extend lifespan

Heat-induced hormesis, i.e. the beneficial effect of mild heat-induced stress, increases the average lifespan of many organisms. This effect, which depends on the heat shock factor, decreases the log mortality rate weeks after the stress has ceased. To identify candidate genes that mediate this lifespan-prolonging effect late in life, we treated flies with mild heat stress (34 °C for 2 h) 3 times early in life and compared the transcriptomic response in these flies versus non-heat-treated controls 10-51 days after the last heat treatment. We found significant transcriptomic changes in the heat-treated flies. Several hsp70 probe sets were up-regulated 1.7-2-fold in the mildly stressed flies weeks after the last heat treatment (P<0.01). This result was unexpected as the major Drosophila heat shock protein, Hsp70, is reported to return to normal levels of expression shortly after heat stress. We conclude that the heat shock response, and Hsp70 in particular, may be central to the heat-induced increase in the average lifespan in flies that are exposed to mild heat stress early in life.

Effect of p38MAPK on immunofunction of spleen macrophages from heat stressed rats

AIM: To investigate the role of p38MAPK in Bip protein-mediated functional changes of mild heat stressed rat splenic macrophages in vitro.

METHODS: Rat splenic macrophages were pretreated with p38MAPK inhibitor and placed into 41 ℃ incubator for mild heat stress. One hour later, temperature was restored to 37 ℃ in inhibition group. Non stressed rat spleen macrophages were assigned to the control group, and macrophages which was heat stressed at 41 ℃ for 1 h (stress group) were used as controls, too. Three groups were detected for macrophage phagocytosis, cytotoxicity and chemotaxis. At the same time p38MAPK protein and Bip protein expressions were detected.

RESULTS: p38MAPK inhibitor pretreated rat splenic macrophages, when compared with the stress group, their phagocytosis, cytotoxicity and chemotaxis were significantly lowered after mild heat stress (0.17 ± 0.01 vs 0.74 ± 0.03, 33.32 ± 3.55 vs 82.07 ± 5.17, 24.20% ± 2.39% vs 60.80% ± 4.02%, all P < 0.01). In stress group p38MAPK protein expressions were significantly increased; compared with the stress group, p38MAPK protein expressions were significantly inhibited after p38MAPK inhibitor pretreatment in inhibition group (p38/β-actin: 2.863 ± 0.794 vs 4.752 ± 1.386, P < 0.01). p38MAPK inhibitor pretreatment also caused changes in Bip protein expressions (Bip/β-actin) in the stress group from 1.2702 ± 0.5345 dropped to 1.0281 ± 1.0614 in inhibition group (P < 0.05).

CONCLUSION: p38 inhibitors can significantly inhibit mild heat stressed rat splenic macrophage phagocytosis, cytotoxicity and chemotaxis, which inhibit p38MAPK and Bip protein expressions.