U. Bernabucci

Seasonal pattern of mortality and relationships between mortality and temperature-humidity index in dairy cows

The 2 studies described investigated seasonal variations of mortality and temperature-humidity index (THI)-mortality relationships in dairy cows. Mortality data were extracted from the Italian Bovine Spongiform Encephalopathy databases, which contain records on cows older than 24 mo that died on a farm from all causes (98% of total records), were slaughtered in an emergency state, or were sent for normal slaughter but were sick in the preslaughter inspection (2% of total records). Both studies evaluated mortality data during a 6-yr period (2002 to 2007). The seasonal pattern study was conducted throughout Italy and was based on 320,120 deaths. An association between season and deaths was found for all 6 yr. Summer and spring were the seasons with the highest and lowest frequency of deaths (15,773.3 +/- 2,861 and 11,619.3 +/- 792.3), respectively, and within summer months, the number of deaths in July and August (5,435 +/- 284 and 5,756 +/- 676.2, respectively) was higher than in June (4,839 +/- 344.8). The THI-mortality relationships study was carried out only for deaths (51,240) reported for the Lombardia and Emilia Romagna regions. For this study, the mortality databases were integrated with THI data, which were calculated by using data from 73 weather stations. Each farm where deaths were recorded was assigned the THI values (maximum and minimum) calculated at the closest weather station for each day the events (deaths) were reported. Analysis of data indicated that approximate THI values of 80 and 70 were the maximum and minimum THI, respectively, above which the number of deaths in dairy farms starts to increase. Maximum and minimum THI values of 87 and 77 were the upper critical THI above which the risk of death for dairy cows becomes maximum. This study defined quantitative relationships between mortality risk and THI in dairy cows and may help to provide emergency interventions and mitigation measures, which may ensure survival of dairy cows and reduce replacement costs associated with heat stress-related mortality.

Influence of heat stress or feed restriction on plasma progesterone, oestradiol-17β, LH, FSH, prolactin and cortisol in Holstein heifers

Abstract The aim of the study was to compare the effects of heat stress and feed restriction on hormonal secretion (progesterone, oestradiol-17β, luteinizing hormone, follicle-stimulating hormone, prolactin and cortisol) in Holstein heifers. Ten pubertal heifers were divided into two groups of five (A and B) and housed in climatic chambers. After a pre-experimental period, the heifers were synchronised for oestrus and monitored for three (group B) or four (group A) consecutive oestrus cycles (OC). In the first OC, both groups were maintained under thermal comfort (TC) and fed on an ad libitum basis. In the second OC, group A was maintained under TC whereas group B was exposed to high air temperatures (HAT); both groups were fed on an ad libitum basis. In the third OC and until day 17 of the fourth OC, group A was kept under TC and fed a restricted diet (the same ration ingested by group B under HAT). At the end of HAT exposure, group B was removed from the study. Exposure to HAT caused development of ovarian cysts in two heifers, an increase in plasma concentrations of prolactin, a decrease in concentrations of cortisol and progesterone, and a 23% reduction in dry matter intake. Feed restriction did not modify any of the parameters considered. Results of this study indicated that the effects of HAT on the above parameters are not altered by a reduction in feed intake.

Climatic Effects on Productive Traits in Livestock

Each species, breed or animal category, correlated with its physiological state, has a comfort zone, in which the energy expenditure of the animal is minimal, constant and independent of environmental temperature. Outside of this zone, the animal experiences stress to maintain homeothermy. This requires extra energy to thermoregulate, so that less energy is available for production processes (Bianca, 1976). The animal modifies its behaviour, especially feeding, physiological and metabolic functions and the quantity and quality of its production. When an animal is for a medium/long period outside of its zone of thermoneutrality it activates mechanisms of acclimatization, whereas population of animals experiencing significant climatic changes can adopt, by genetic adaptation, modifying genetic and phenotypic features over generations. The more the impact of the climatic conditions on the animal varies in magnitude and length, the more difficulties the organism has to maintain homeothermy. Outside the extreme limits of this zone, the organism experiences hypothermy or hyperthermy until it dies from cold or heat. The difference between normal and lethal body temperature is in the order of 15–25◦C in the cold and of only around 3–6◦C in the heat. This explains why cold represents less of a problem than heat (Bianca, 1976; Collier et al., 1982) and why high selected productive animals, with high endogenous heat production, show high tolerance to cold and low tolerance to heat. Consistently, the limits of the thermal comfort zone for these selected animals becoming lower and the animals are becoming more and more sensitive to heat stress (HS). Animals have two means by which to exchange heat with the environment: via evaporative or latent (sweating and painting) or non-evaporative or sensible (conduction, convection, radiation) systems (Yousef, 1987). Because air temperature alone is an imperfect measure of the thermal environment, many attempts have been made to combine the effects of two or more thermal environmental factors to better represent the influence of sensible and latent heat exchange between an organism and its environment. The Temperature Humidity Index (THI) (Johnson, 1980) is the most extensively employed index for moderate to hot conditions, even though some limitations exist related to air speed and radiation heat loads (Hahn et al., 2003). Heat and draught

The effects of heat stress in Italian Holstein dairy cattle

The data set for this study comprised 1,488,474 test-day records for milk, fat, and protein yields and fat and protein percentages from 191,012 first-, second-, and third-parity Holstein cows from 484 farms. Data were collected from 2001 through 2007 and merged with meteorological data from 35 weather stations. A linear model (M1) was used to estimate the effects of the temperature-humidity index (THI) on production traits. Least squares means from M1 were used to detect the THI thresholds for milk production in all parities by using a 2-phase linear regression procedure (M2). A multiple-trait repeatability test-model (M3) was used to estimate variance components for all traits and a dummy regression variable (t) was defined to estimate the production decline caused by heat stress. Additionally, the estimated variance components and M3 were used to estimate traditional and heat-tolerance breeding values (estimated breeding values, EBV) for milk yield and protein percentages at parity 1. An analysis of data (M2) indicated that the daily THI at which milk production started to decline for the 3 parities and traits ranged from 65 to 76. These THI values can be achieved with different temperature/humidity combinations with a range of temperatures from 21 to 36°C and relative humidity values from 5 to 95%. The highest negative effect of THI was observed 4 d before test day over the 3 parities for all traits. The negative effect of THI on production traits indicates that first-parity cows are less sensitive to heat stress than multiparous cows. Over the parities, the general additive genetic variance decreased for protein content and increased for milk yield and fat and protein yield. Additive genetic variance for heat tolerance showed an increase from the first to third parity for milk, protein, and fat yield, and for protein percentage. Genetic correlations between general and heat stress effects were all unfavorable (from -0.24 to -0.56). Three EBV per trait were calculated for each cow and bull (traditional EBV, traditional EBV estimated with the inclusion of THI covariate effect, and heat tolerance EBV) and the rankings of EBV for 283 bulls born after 1985 with at least 50 daughters were compared. When THI was included in the model, the ranking for 17 and 32 bulls changed for milk yield and protein percentage, respectively. The heat tolerance genetic component is not negligible, suggesting that heat tolerance selection should be included in the selection objectives.

Chronic heat stress up-regulates leptin and adiponectin secretion and expression and improves leptin, adiponectin and insulin sensitivity in mice

Heat stress (HS) induces adaptive responses that are responsible for alterations of carbohydrate and lipid metabolism. This study aimed to evaluate the effects of chronic heat treatment on the expression and secretion of leptin and adiponectin, important regulators of energy homeostasis, food intake and insulin action. C57BL/6 mice were subdivided into three groups (24 mice each). The first group was kept under control conditions (C: 22±2 °C). The second group was exposed to HS (35±1 °C). The third group was kept under control conditions and was food restricted (FR). The HS group had higher rectal temperature than the C and FR groups and lower food intake than the C group. Hspa1 (Hspa1a) gene expression in adipose tissue, muscle and liver was higher under HS than FR and C. Heat treatment resulted in decreased blood glucose and non-esterified fatty acids; increased leptin, adiponectin and insulin secretion; and greater glucose disposal. Leptin, adiponectin, leptin and adiponectin receptors, insulin receptor substrate-1 and glucose transporter mRNAs were up-regulated in HS mice. This study provides evidence that HS improves leptin and adiponectin signalling in adipose tissue, muscle and liver. Heat stress was responsible for improving insulin sensitivity and glucose uptake in peripheral tissues, probably mediated by adipokines. Changes in the adipokine levels and sensitivity to them may be considered as an adaptive response to heat.

Seasonal variations in the composition of Holstein cow's milk and temperature-humidity index relationship

A retrospective study on seasonal variations in the characteristics of cows milk and temperature-humidity index (THI) relationship was conducted on bulk milk data collected from 2003 to 2009. The THI relationship study was carried out on 508 613 bulk milk data items recorded in 3328 dairy farms form the Lombardy region, Italy. Temperature and relative humidity data from 40 weather stations were used to calculate THI. Milk characteristics data referred to somatic cell count (SCC), total bacterial count (TBC), fat percentage (FA%) and protein percentage (PR%). Annual, seasonal and monthly variations in milk composition were evaluated on 656 064 data items recorded in 3727 dairy farms. The model highlighted a significant association between the year, season and month, and the parameters analysed (SCC, TBC, FA%, PR%). The summer season emerged as the most critical season. Of the summer months, July presented the most critical conditions for TBC, FA% and PR%, (52 054 ± 183 655, 3.73% ± 0.35% and 3.30% ± 0.15%, respectively), and August presented higher values of SCC (369 503 ± 228 377). Each milk record was linked to THI data calculated at the nearest weather station. The analysis demonstrated a positive correlation between THI and SCC and TBC, and indicated a significant change in the slope at 57.3 and 72.8 maximum THI, respectively. The model demonstrated a negative correlation between THI and FA% and PR% and provided breakpoints in the pattern at 50.2 and 65.2 maximum THI, respectively. The results of this study indicate the presence of critical climatic thresholds for bulk tank milk composition in dairy cows. Such indications could facilitate the adoption of heat management strategies, which may ensure the health and production of dairy cows and limit related economic losses.

Aflatoxin B1 and fumonisin B1 affect the oxidative status of bovine peripheral blood mononuclear cells

Mycotoxins are secondary metabolites having a high cytotoxic potential. They are produced by molds and released in food and feed. To date, the mechanisms underlying the mycotoxin-induced cytotoxicity have not been fully clarified. The induction of oxidative stress, as a possible mechanism, has been postulated. This in vitro study was focused on the effect of two widely occurring mycotoxins, aflatoxin B(1) (AFB(1)) and fumonisin B(1) (FB(1)), on the oxidative status of bovine peripheral blood mononuclear cells (PBMC) incubated for 2 and 7 days at different levels of AFB(1) (0, 5 and 20 μg/ml) and FB(1) (0, 35 and 70 μg/ml). Reactive oxygen metabolites (ROM), intracellular thiols (SH), malondialdehyde (MDA) and gene expression of cytoplasmic superoxide dismutase (SOD) and glutathione peroxidase (GSHPX-1) were measured on PBMC after incubation. The highest concentration of AFB(1) and all concentrations of FB(1) caused an increase (p<0.05) of intracellular ROM without any time dependent effect. Intracellular SH decreased with 20 μg AFB(1)/ml (p<0.05) and the effect was particularly marked after 7 days of exposure. Intracellular SH were not affected by FB(1) even though a lower (p<0.05) SH level after 2 days exposure than after 7 days was observed. MDA increased (p<0.05) in AFB(1) or FB(1) treated PBMC. The exposure to FB(1) for 7 days increased MDA (p<0.05) only in cells treated with 70 μg/ml. Exposure of PBMC to AFB(1) reduced SOD mRNA while FB(1) decreased both SOD and GSHPX-1 mRNA abundance. These results demonstrate that, even though by different mechanisms, AFB(1) and FB(1) may induce cytotoxicity through an impairment of the oxidative status of PBMC.

Dynamics of the temperature-humidity index in the Mediterranean basin

The study was aimed at describing the temperature humidity index (THI) dynamics over the Mediterranean basin for the period 1951–2007. The THI combines temperature and humidity into a single value, and may help to predict the effects of environmental warmth in farm animals. In particular, on the basis of THI values, numerous studies have been performed to establish thresholds for heat stress in dairy cows. The THI was calculated by using monthly mean values of temperature and humidity obtained from the National Center for Environmental Prediction/National Center for Atmospheric Research reanalysis project. The analysis demonstrated a high degree of heterogeneity of THI patterns over the Mediterranean basin, a strong north–south gradient, and an overall warming during the study period, which was particularly marked during summer seasons. Results indicated that several areas of the basin present summer THI values which were unfavorable to cow welfare and productivity, and that risk of heat stress for cows is generally greater in the countries of the south coast of the basin. Furthermore, THI data from the summer 2003 revealed that severe positive anomalies may impact areas normally characterized by a favorable climate for animal production. In conclusion, THI dynamics should be taken into careful consideration by farmers and policy makers operating in Mediterranean countries when planning investments in the sector of animal production. The investments should at least partially be directed towards implementation of adaptation measures, which may help to alleviate the impact of hot on farm animals welfare, performance and health.

Heat shock modulates adipokines expression in 3T3-L1 adipocytes

Studies have demonstrated that heat shock is associated with alteration in energy metabolism. In this study, we investigated the effect of heat shock on gene expression and secretion of adiponectin and leptin, and gene expression of Hspa2 and Ppargamma in 3T3-L1 adipocytes. Compared with 37 degrees C, adiponectin mRNA was higher at 39 degrees C, and lower at 41 degrees C. Leptin mRNA was higher when adipocytes were exposed to 41 degrees C compared with 37 and 39 degrees C. Secretion of adiponectin increased at 39 degrees C, and when cells were exposed to 41 degrees C it was not detectable. Leptin secretion increased significantly at 41 degrees C, compared with 37 and 39 degrees C. Hspa2 mRNA was increased at 39 degrees C, and the highest level was reached at 41 degrees C. Ppargamma mRNA exhibited a substantial increase in a temperature-dependent manner. The study provides the first evidence of a possible direct effect of heat shock on adiponectin and leptin gene expression and secretion, and demonstrates that the expression of the two adipokines is differentially regulated at the temperatures tested.

Effect of summer season on milk protein fractions in Holstein cows

Milk characteristics are affected by heat stress, but very little information is available on changes of milk protein fractions and their relationship with cheesemaking properties of milk. The main objective of the study was to evaluate the effect of hot season on milk protein fractions and cheesemaking properties of milk for Grana Padano cheese production. The study was carried out in a dairy farm with a cheese factory for transforming the milk to Grana Padano cheese. The study was carried out from June 2012 to May 2013. Temperature and relative humidity of the inside barn were recorded daily during the study period using 8 electronic data loggers programmed to record every 30 min. Constant managerial conditions were maintained during the experimental periods. During the experimental period, feed and diet characteristics, milk yield, and milk characteristics were recorded in summer (from June 29 to July 27, 2012), winter (from January 25 to March 8, 2013), and spring (from May 17 to May 31, 2013). Milk yield was recorded and individual milk samples were taken from 25 cows selected in each season during the p.m. milking. Content of fat, proteins, caseins (CN), lactose and somatic cell count (SCC), titratable acidity, and milk rennet coagulation properties were determined on fresh samples. Milk protein fraction concentrations were determined by the sodium dodecyl sulfate-PAGE. Data were tested for nonnormality by the Shapiro-Wilk test. In case of nonnormality, parameters were normalized by log or exponential transformation. The data were analyzed with repeated measures ANOVA using a mixed model procedure. For all the main milk components (fat, protein, total solids, and solids-not-fat), the lowest values were observed in the summer and the greatest values were observed in the winter. Casein fractions, with the exception of γ-CN, showed the lowest values in the summer and the greatest values in the winter. The content of IgG and serum albumin was greater in summer than in the winter and spring. A mild effect of season was observed for milk SCC, with greater values in summer than in the winter and spring. A worsening of milk coagulation properties was observed in summer season. The alteration of cheesemaking properties during hot season seems strictly linked with changes of milk protein fractions mainly with the decrease of αS-CN and β-CN and the increase of undefined proteins.