Heat-stressed Cows Research Articles

EFFECT OF LONG CHAIN FATTYACIDS ON THE PRODUCTION AND REPRODUCTIVE IMMUNITY OF HOLSTEIN DAIRY COWS

Twenty two multiparous and primiparous Holstein cows were utilized in a completely randomized design to determine the effects of feeding diets containing health, immunity, reproductive responses of heat stressed cows during the transition period. Dietary treatments were initiated 20-35 d prior to estimate calving date and continued till confirmed pregnancy postpartum. Diets were formulated to be isocaloric and isonitrogenous and started feeding the pre calving diets at July for the precalving cows and the post calving diets were fed tell conception. Dry matter intake (DMI) was measured and recorded , the average 1 three months postpartum milk production were calculated. Total mixed ration (TMR) ration were collected monthly , and analyzed. Milk samples were collected for analysis and measuring beta hydroxy buterate (BHB), lysozy me and nitric oxide concentration .The obtained results showed no difference in the average DMI between the two group sin pre calving stage (12.5for G1;12.4 for G2,Kg/h/d),while, it was higher in theG1(20.55) than in G2 (18.45) in the 1st three month post calving. Milk production was increased in G1(36.42±0.14kg)than in G2 (34.57±0.20kg) but they are not significantly different. Also there was no significant difference between the two groups in milk analysis for protein, fat, SNF, and lactose at W2, W4 and at W7 postpartum. BHB concentration at W2 PP was significantly lower in G1 (25±9.45µg/mol.) than those in G2 (81.25±9.15µg/mol.) , lysozyme at w2, w4 and w7 PP was significantly decreased in G1(94.10±30.73,45.56±9.86,26.15±11.12µg/ml) than those in G2 (246.34±6.11, 217.21±9.56, 192.68±11.048µg/ml) respectively. Nitric oxide concentration was significantly decreased in G1 (47.38±18.21, 18.43±3.45, 14.27±2.72 µm/ml) than those in G2 (91.79±9.55, 64.73±7.40, 42.53±6.31µm/ml) at W2,W4 and W7, respectively. Uterine cytology (neutrophil concentration) at day40±3PP was higher in G2 than G1 but they were not significantly different. Days to1st estrus and days to1st insemination were significantly lower in group one (36.92±0.52, 75.0793±0.68) than those in G2 (86.18±0.64, 88.94±0.53) respectively. Days open and I.N. in G1 (172.89±3.13, 3.19±0.06) were lower than those in G2(195.42±2.78,4.07±0.07) but they were not significantly different. Conception rate(CR%) at1st, 2nd and 3rdinsemination was higher in G1 (10%,50%,20%) than those in G2(8.33%,25%,8.33%) and also repeat breeder (%) was much greater in G2(58.33%) than in G1 (30%). This study concluded that, using omega-3FA may enhance there productive performance of dairy cows during summer season because of its anti-inflammatory potency, leading to a higher chance of survival of the embryo when supplemented during the per conceptual period by reducing the oxidative stress.

Strong, sudden cooling alleviates the inflammatory responses in heat-stressed dairy cows based on iTRAQ proteomic analysis.

This study was designed to investigate the effects of sudden cooling on the physiological responses of 12 heat-stressed Holstein dairy cows using an isobaric tags for relative and absolute quantification (iTRAQ) labeling approach. Plasma samples were collected from these cows during heat stress (HS), and after strong, sudden cooling in the summer (16days later). We compared plasma proteomic data before and after sudden cooling to identify the differentially abundant proteins. The results showed that sudden cooling in summer effectively alleviated the negative consequences of HS on body temperature and production variables. Expressions of plasma hemoglobin alpha and hemoglobin beta were upregulated, whereas lipopolysaccharide-binding protein (LBP) and haptoglobin were downregulated in this process. The increase of hemoglobin after cooling may improve oxygen transport and alleviate the rise in respiration rates in heat-stressed dairy cows. The decrease of LBP and haptoglobin suggests that the inflammatory responses caused by HS are relieved after cooling. Our findings provide new insight into the physiological changes that occur when heat-stressed dairy cows experience strong, sudden cooling.

Cows exposed to heat stress during fetal life exhibit improved thermal tolerance.

Maternal heat stress during late gestation affects calf function during postnatal life. The objective of the present study was to evaluate whether calves that experience heat stress in utero have altered thermoregulatory responses to acute heat stress later in life. Specifically, the hypothesis was that heat stress in utero would improve the response to acute heat stress at maturity. Females were born to dams exposed to heat stress or cooled during late gestation preceding their birth. All animals were raised postnatally under identical management. Twelve lactating Holstein cows that were exposed to in utero heat stress (HT) and 12 that were exposed to in utero control (CON) were used. A heat stress challenge was conducted in 3 blocks using 4 HT and 4 CON cows matched according to milk yield, stage of lactation, and parity. Each challenge consisted of transfer from a barn with shade and evaporative cooling to one with shade but no additional cooling for 48 h. The challenge was replicated twice for each block. Sweating rate, respiration rate, rectal temperature (RT), and skin temperature were measured on each cow at 0900, 1100, 1300, 1500, and 1700 h for 2 consecutive days. Mean ambient temperature across 6 challenge days was 26.15 ± 4.75°C. Tendencies for differences at 1700 h were observed between treatments for RT (HT: 39.5 ± 0.1; CON: 39.6 ± 0.1°C; = 0.065), however, there was no difference in respiration rate (HT: 77.6 ± 1.6; CON: 79.5 ± 1.6 bpm; = 0.85). Sweating rate for shaved skin (HT: 29.4 ± 2.0; CON: 36.0 ± 2.0 g/mh; = 0.057) and for non-shaved skin (HT: 22.5 ± 1.5; CON: 29.2 ± 1.2 g/mh; = 0.01) differed between groups. However, there was no effect on skin temperature at the shaved location (HT: 36.2 ± 0.2; CON: 36.0 ± 0.2°C; = 0.81), but there was a tendency for differences for the non-shaved area (HT: 35.4 ± 0.2; CON: 34.9 ± 0.2°C; = 0.097). Cows that underwent in utero heat stress had greater skin temperature at 1700 h vs. in utero control cows, which may be because HT cows increased skin perfusion, and consequently greater cooling via conduction. In utero HT cows would then have higher heat loss and reduced core body temperature, which results in lower rectal temperature and lower sweating rate when exposed to heat stress. These results support the hypothesis that heat stress in utero in late gestation increases heat tolerance at maturity by increasing capacity to dissipate heat to maintain core body temperature.

Effect of nutritional immunomodulation and heat stress during the dry period on subsequent performance of cows.

Heat stress in dairy cows during the dry period impairs milk yield in the next lactation. Feeding OmniGen-AF (OG; Phibro Animal Health Corp., Teaneck, NJ) to lactating cows during heat stress may increase dry matter intake (DMI) and lowers respiration rate (RR) and rectal temperature (RT), but the effects in dry cows are not known. We hypothesized that OG supplementation before, during, and after the dry period (approximately 160 d total) would overcome the effects of heat stress and improve cow performance in the next lactation. Cows were randomly assigned to OG or control (placebo) treatments for the last 60 d in milk (DIM), based on mature-equivalent milk yield in the previous lactation. Cows were dried off 45 d before expected calving and randomly assigned to heat stress (HT) or cooling (CL) treatments. Thus, cows received dietary supplementation during late lactation before they were exposed to either CL or HT. After dry-off, treatment groups included heat stress with placebo (HT, only shade, 56 g/d of placebo, n = 17), HT with OG supplementation (HTOG, 56 g/d of OG, n = 19), cooling with placebo (CL, shade, fans, and soakers, 56 g/d of placebo, n = 16), and CL with OG supplementation (CLOG, 56 g/d of OG, n = 11). After parturition, all cows were kept under the same CL system and management, and all cows continued to receive OG or control treatment until 60 DIM. Cooling cows during the dry period reduced afternoon RT (CL vs. HT; 38.9 ± 0.05 vs. 39.3 ± 0.05°C) and RR (CL vs. HT; 45 ± 1.6 vs. 77 ± 1.6 breaths/min). Respiration rate was also decreased by OG supplementation under HT conditions (HTOG vs. HT; 69.7 ± 1.6 vs. 77.2 ± 1.6 breaths/min). An interaction was observed between OG supplementation and HT; HTOG cows tended to have lower morning RT compared with HT cows. During the dry period, OG reduced DMI relative to control cows. Birth weight was greater in calves from CL cows (CL vs. HT; 40.6 ± 1.09 vs. 38.7 ± 1.09 kg). No differences were detected among treatments in hematocrit, total protein, and body condition score. Cows offered CLOG, CL, and HTOG treatments had greater body weight during the dry period (794.9 ± 17.9, 746.8 ± 16.7, and 762.9 ± 14.9 kg, respectively) than HT cows (720 ± 16.2 kg). Gestation length was approximately 4 d longer for CL cows compared with HT cows. Cows offered CLOG, CL, and HTOG treatments produced more milk (41.3 ± 1.6, 40.7 ± 1.6, and 40.5 ± 1.6 kg/d, respectively) than HT treatment (35.9 ± 1.6 kg/d). Body weight after parturition and DMI were evaluated up to 60 DIM and averaged 661.5 ± 15.8 and 19.4 ± 0.7 kg/d, respectively, with no differences observed among treatments. These results confirm that exposure of dry cows to heat stress negatively affects milk yield in the subsequent lactation. Active cooling of dry cows and OG supplementation can reduce the negative effects of heat stress in the dry period on subsequent performance.

Hepatic thyroid signaling of heat-stressed late pregnant and early lactating cows.

During the transition between late gestation and early lactation, dairy cows experience severe metabolic stress due to the high energy and nutrient requirements of the fetus and the mammary gland. Additional thermal stress that occurs with rising temperatures during the ongoing climate change has further adverse implications on energy intake, metabolism and welfare. The thyroid hormone (TH)-mediated cellular signaling has a pivotal role in regulation of body temperature, energy intake and metabolic adaptation to heat. To distinguish between energy intake and heat stress-related effects, Holstein cows were first kept at thermoneutrality at 15°C followed by exposure to heat stress (HS) at 28°C or pair-feeding (PF) at 15°C for 6 days, in late pregnancy and again in early lactation. Herein, we focused on hepatic metabolic changes associated with alterations in the hypothalamic–pituitary–thyroid axis in HS and PF animals. T3 and T4 levels dropped with HS or PF; however, in HS animals, this decline was more pronounced. Thyroid-stimulating hormone (TSH) levels remain unaffected, while plasma cholesterol concentrations were lower in HS than PF animals. Hepatic marker genes for TH action (THRA, DIO1 and PPARGC1) decreased after HS and were lower compared to PF cows but only post-partum. Proteomics data revealed reduced hepatic amino acid catabolism ante-partum and a shift toward activated beta-oxidation and gluconeogenesis but declined oxidative stress defense post-partum. Thus, liver metabolism of HS and PF cows adapts differently to diminished energy intake both ante-partum and post-partum, and a different TH sensitivity is involved in the regulation of catabolic processes.

The effects of heat stress on protein metabolism in lactating Holstein cows

Heat stress (HS) decreases milk protein synthesis beyond what would be expected based on the concomitant reduction in feed intake. The aim of the present study was to evaluate the direct effects of HS on milk protein production. Four multiparous, lactating Holstein cows (101 ± 10 d in milk, 574 ± 36 kg of body weight, 38 ± 2 kg of milk/d) were individually housed in environmental chambers and randomly allocated to 1 of 2 groups in a crossover design. The study was divided into 2 periods with 2 identical experimental phases (control phase and trial phase) within each period. During phase 1 or control phase (9 d), all cows were housed in thermal neutral conditions (TN; 20°C, 55% humidity) and fed ad libitum. During phase 2 or treatment phase (9 d), group 1 was exposed to cyclical HS conditions (32 to 36°C, 40% humidity) and fed ad libitum, whereas group 2 remained in TN conditions but was pair-fed (PFTN) to their HS counterparts to eliminate the confounding effects of dissimilar feed intake. After a 30-d washout period in TN conditions, the study was repeated (period 2), inverting the environmental treatments of the groups relative to period 1: group 2 was exposed to HS and group 1 to PFTN conditions. Compared with PFTN conditions, HS decreased milk yield (17.0%), milk protein (4.1%), milk protein yield (19%), 4% fat-corrected milk (23%), and fat yield (19%). Apparent digestibility of dry matter, organic matter, neutral detergent fiber, acid detergent fiber, crude protein, and ether extract was increased (11.1-42.9%) in HS cows, as well as rumen liquor ammonia (before feeding 33.2%; after feeding 29.5%) and volatile fatty acid concentration (45.3%) before feeding. In addition, ruminal pH was reduced (9.5 and 6% before and after feeding, respectively) during HS. Heat stress decreased plasma free amino acids (AA; 17.1%) and tended to increase and increased blood, urine, and milk urea nitrogen (17.2, 243, and 24.5%, respectively). Further, HS cows had reduced plasma glucose (8%) and nonesterified fatty acid (39.8%) concentrations compared with PFTN controls. These data suggest that HS increases systemic AA utilization (e.g., decreased plasma AA and increased nitrogen excretion), a scenario that limits the AA supply to the mammary gland for milk protein synthesis. Furthermore, the increase in AA requirements during HS might represent the increased need for gluconeogenic precursors, as HS is thought to prioritize glucose utilization as a fuel at the expense of nonesterified fatty acids.

Thermoregulatory responses of Holstein cows exposed to experimentally induced heat stress

Heat stress (HS) adversely influences productivity and welfare of dairy cattle. We hypothesized that the thermoregulatory mechanisms vary depending on the exposure time to HS, with a cumulative effect on the adaptive responses and thermal strain of the cow. To identify the effect of HS on adaptive thermoregulatory mechanisms and predictors of caloric balance, Holstein cows were housed in climate chambers and randomly distributed into thermoneutral (TN; n=12) or HS (n=12) treatments for 16 days. Vaginal temperature (VT), rectal temperature (Tre), respiratory rate (RR), heart rate (HR), and dry matter intake (DMI) were measured. The temperature and humidity under TN were 25.9±0.2°C and 73.0±0.8%, respectively, and under HS were 36.3±0.3°C and 60.9±0.9%, respectively. The RR of the HS cows increased immediately after exposure to heat and was higher (76.02±1.70bpm, p<0.001) than in the TN (39.70±0.71bpm). An increase in Tre (39.87±0.07°C in the HS vs. 38.56±0.03°C in the TN, p<0.001) and in VT (39.82±0.10°C in the HS vs. 38.26±0.03°C in the TN, p<0.001) followed the increase in RR. A decrease (p<0.05) in HR occurred in the HS (62.13±0.99bpm) compared with the TN (66.23±0.79bpm); however, the magnitude of the differences was not the same over time. The DMI was lower in HS cows from the third day (8.27±0.33kgd−1 in the HS vs. 14.03±0.29kgd−1 in the TN, p<0.001), and the reduction of DMI was strongly affected (r=−0.65) by changes in the temperature humidity index. The effect of environmental variables from the previous day on physiological parameters and DMI was more important than the immediate effect, and ambient temperature represented the most determinant factor for heat exchange. The difference in the responses to acute and chronic exposure to HS suggests an adaptive response. Thus, intense thermal stress strongly influence thermoregulatory mechanisms and the acclimation process depend critically on heat exposure time.

Jugular-infused methionine, lysine and branched-chain amino acids does not improve milk production in Holstein cows experiencing heat stress

Poor utilization of amino acids contributes to losses of milk protein yield in dairy cows exposed to heat stress (HS). Our objective was to test the effect of essential amino acids on milk production in lactating dairy cows exposed to short-term HS conditions. To achieve this objective, 12 multiparous, lactating Holstein cows were assigned to two environments (thermoneutral (THN) or HS) from days 1 to 14 in a split-plot type cross-over design. All cows received 0 g/day of essential amino acids from days 1 to 7 (negative control (NC)) followed by an intravenous infusion of l-methionine (12 g/day), l-lysine (21 g/day), l-leucine (35 g/day), l-isoleucine (15 g/day) and l-valine (15 g/day, methionine, lysine and branched-chain amino acids (ML+BCAA)) from days 8 to 14. The basal diet was composed of ryegrass silage and hay, and a concentrate mix. This diet supplied 44 g of methionine, 125 g of lysine, 167 g of leucine, 98 g of isoleucine and 109 g of valine per day to the small intestine of THN cows. Temperature–humidity index was maintained below 66 for the THN environment, whereas the index was maintained above 68, peaking at 76, for 14 continuous h/day for the HS environment. Heat stress conditioning increased the udder temperature from 37.0°C to 39.6°C. Cows that received the ML+BCAA treatment had greater p.m. rectal and vaginal temperatures (0.50°C and 0.40°C, respectively), and respiration rate (8 breaths/min) compared with those on the NC treatment and exposed to a HS environment. However, neither NC nor ML+BCAA affected rectal or vaginal temperatures and respiration rates in the THN environment. Compared with THN, the HS environment reduced dry matter intake (1.48 kg/day), milk yield (2.82 kg/day) and milk protein yield (0.11 kg/day). However, compared with NC, the ML+BCAA treatment increased milk protein percent by 0.07 points. For the THN environment, the ML+BCAA treatment increased concentrations of milk urea nitrogen. For the HS environment, the ML+BCAA treatment decreased plasma concentrations of arginine, ornithine and citrulline; however, differences were not observed for the THN environment. In summary, HS elicited expected changes in production; however, infusions of ML+BCAA failed to increase milk protein yield. Lower dry matter intake and greater heat load in response to ML+BCAA contributed to the lack of response in milk production in HS cows. The ML+BCAA treatment may have reduced the breakdown of muscle protein in heat-stressed cows.

1176 Effect of OmniGen-AF® supplementation to heat stressed cows during late gestation on blood parameters and immune cells of their calves

1176 Effect of OmniGen-AF® supplementation to heat stressed cows during late gestation on blood parameters and immune cells of their calves

Modification of embryonic resistance to heat shock in cattle by melatonin and genetic variation in HSPA1L.

The objectives were to test whether (1) melatonin blocks inhibition of embryonic development caused by heat shock at the zygote stage, and (2) the frequency of a thermoprotective allele for HSPA1L is increased in blastocysts formed from heat-shocked zygotes as compared with blastocysts from control zygotes. It was hypothesized that melatonin prevents effects of heat shock on development by reducing accumulation of reactive oxygen species (ROS) and that embryos inheriting the thermoprotective allele of HSPA1L would be more likely to survive heat shock. Effects of 1 µM melatonin on ROS were determined in experiments 1 and 2. Zygotes were cultured at 38.5 or 40°C for 3 h in the presence of CellROX reagent (ThermoFisher Scientific, Waltham, MA). Culture was in a low [5% (vol/vol)] oxygen (experiment 1) or low or high [21% (vol/vol)] oxygen environment (experiment 2). Heat shock and high oxygen increased ROS; melatonin decreased ROS. Development was assessed in experiments 3 and 4. In experiment 3, zygotes were cultured in low oxygen ± 1 µM melatonin and exposed to 38.5 or 40°C for 12 h (experiment 1) beginning 8 h after fertilization. Melatonin did not protect the embryo from heat shock. Experiment 4 was performed similarly except that temperature treatments (38.5 or 40°C, 24 h) were performed in a low or high oxygen environment (2×2 × 2 factorial design with temperature, melatonin, and oxygen concentration as main effects), and blastocysts were genotyped for a deletion (D) mutation (C→D) in the promoter region of HSPA1L associated with thermotolerance. Heat shock decreased percent of zygotes developing to the blastocyst stage independent of melatonin or oxygen concentration. Frequency of genotypes for HSPA1L was affected by oxygen concentration and temperature, with an increase in the D allele for blastocysts that developed in high oxygen and following heat shock. It was concluded that (1) lack of effect of melatonin or oxygen concentration on embryonic development means that the negative effects of heat shock on the zygote are not mediated by ROS, (2) previously reported effect of melatonin on fertility of heat-stressed cows might involve actions independent of the antioxidant properties of melatonin, and (3) the deletion mutation in the promoter of HSPA1L confers protection to the zygote from heat shock and high oxygen. Perhaps, embryonic survival during heat stress could be improved by selecting for thermotolerant genotypes.

In utero heat stress decreases calf survival and performance through the first lactation.

Calves born to cows exposed to heat stress during late gestation (i.e., the dry period) have lower birth weight and weaning weight and compromised passive immune transfer compared with those born to dams that are cooled. However, it is unknown if heat stress in utero has carryover effects after weaning. The objective was to evaluate the effect of heat stress (HT) or cooling (CL) in late gestation dairy cows on the survival, growth, fertility, and milk production in the first lactation of their calves. Data of animals obtained from previous experiments conducted during 5 consecutive summers in Florida were pooled and analyzed. Cows were dried off 46d before expected calving and randomly assigned to 1 of 2 treatments, HT or CL. Cooled cows were housed with sprinklers, fans, and shade, whereas only shade was provided to HT cows. Within 4h of birth, 3.8 L of colostrum was fed to calves from both groups of cows. All calves were managed in the same manner and weaned at 49d of age. Birth weight and survival of 146 calves (HT=74; CL=72) were analyzed. Additionally, body weight, growth rate, fertility, and milk production in the first lactation from 72 heifers (HT=34; CL=38) were analyzed. As expected, HT calves were lighter (means ± SEM; 39.1±0.7 vs. 44.8±0.7kg) at birth than CL calves. Cooled heifers were heavier up to 1yr of age, but had similar total weight gain (means ± SEM; 305.8±6.3 vs. 299.1±6.3kg, respectively) compared with HT heifers. No effect of treatment was observed on age at first insemination (AI) and age at first parturition. Compared with CL heifers, HT heifers had a greater number of services per pregnancy confirmed at d 30 after AI, but no treatment effect was observed on number of services per pregnancy confirmed at d 50 after AI. A greater percentage of CL heifers reached first lactation compared with HT heifers (85.4 vs. 65.9%). Moreover, HT heifers produced less milk up to 35wk of the first lactation compared with CL heifers (means ± SEM; 26.8±1.7 vs. 31.9±1.7kg/d), and no difference in body weight during lactation was observed (means ± SEM; HT: 568.4±14.3kg; CL: 566.5±14.3kg). These data suggest that heat stress during the last 6wk of gestation induces a phenotype that negatively affects survival and milk production up to and through the first lactation of offspring.

Plasma-based proteomics reveals immune response, complement and coagulation cascades pathway shifts in heat-stressed lactating dairy cows

Heat stress (HS) has an enormous economic impact on the dairy industry. In recent years, many researchers have investigated changes in the gene expression and metabolomics profiles in dairy cows caused by HS. However, the proteomics profiles of heat-stressed dairy cows have not yet been completely elucidated. We compared plasma proteomics from HS-free and heat-stressed dairy cows using an iTRAQ labeling approach. After the depletion of high abundant proteins in the plasma, 1472 proteins were identified. Of these, 85 proteins were differentially abundant in cows exposed to HS relative to HS-free. Database searches combined with GO and KEGG pathway enrichment analyses revealed that many components of the complement and coagulation cascades were altered in heat-stressed cows compared with HS-free cows. Of these, many factors in the complement system (including complement components C1, C3, C5, C6, C7, C8, and C9, complement factor B, and factor H) were down-regulated by HS, while components of the coagulation system (including coagulation factors, vitamin K-dependent proteins, and fibrinogens) were up-regulated by HS. In conclusion, our results indicate that HS decreases plasma levels of complement system proteins, suggesting that immune function is impaired in dairy cows exposed to HS. Biological significanceThough many aspects of heat stress (HS) have been extensively researched, relatively little is known about the proteomics profile changes that occur during heat exposure. In this work, we employed a proteomics approach to investigate differential abundance of plasma proteins in HS-free and heat-stressed dairy cows. Database searches combined with GO and KEGG pathway enrichment analyses revealed that HS resulted in a decrease in complement components, suggesting that heat-stressed dairy cows have impaired immune function. In addition, through integrative analyses of proteomics and previous metabolomics, we showed enhanced glycolysis, lipid metabolic pathway shifts, and nitrogen repartitioning in dairy cows exposed to HS. Our findings expand our current knowledge on the effects of HS on plasma proteomics in dairy cows and offer a new perspective for future research.

Climatic conditions, twining and frequency of milking as factors affecting the risk of fetal losses in high-yielding Holstein cows in a hot environment.

An epidemiological study of risk factors for fetal losses was carried out on 62,403 high-yielding Holstein cows in 29 large highly technified dairy herds in northern Mexico (25° N; 23.5°C mean annual temperature). Multivariate multiple-group response model indicated that fetal losses between 43 and 260days of pregnancy were 23%. Heat-stressed cows at conception (temperature-humidity index, THI >82) were 14 times more likely (P < 0.01) to present fetal losses than not heat-stressed cows (27 vs. 18%). Heat-stressed cows at 60days of pregnancy (THI >82) were 4.5 times more likely (P < 0.01) to present fetal losses than cows suffering heat stress in early gestation (29.1 vs. 17.7%). The proportion of cows experiencing fetal loss was lower for multiparous than primiparous cows (odds ratio; OR = 0.7). Cows with twin pregnancies had significantly increased chances of losing their fetuses than cows with a single fetus (33.6 vs. 20.7%; P < 0.01). Cows with three milkings per day were 30% more likely (P < 0.01) to lose their fetuses than cows milked twice daily. Cows calving in winter and spring had significantly increased chances of losing their fetuses than cows calving in summer and fall (30-35 vs. 4-5%; P < 0.01). It was concluded that, in this particular environment, heat stress exert a great influence on fetal losses in high producing Holstein cows.

Short communication: Effect of heat stress on markers of autophagy in the mammary gland during the dry period

Heat stress (HT) during the dry period compromises mammary gland (MG) growth, thus negatively affecting subsequent milk yield. Cooling during the late dry period, when mammary tissue proliferates, is a common management practice. However, it neglects MG involution during the early dry period, a process that is accomplished by both apoptosis and autophagy. Our objective was to evaluate the effect of HT on MG autophagy during the early dry period. Holstein cows were dried off ~45d before expected calving and randomly assigned to 1 of 2 treatments: HT or cooling (CL). All cows were housed in the same free stall barn during the dry period, but only the stall area for CL cows was equipped with soakers and fans. Rectal temperature and respiration rate were measured daily during the dry period. Mammary gland biopsies were collected from each cow 3d before dry-off and on d 3, 7, 14, and 22±2 after dry-off. Autophagy in the MG was determined by measuring protein expression of 2 autophagic markers, autophagy-related protein 7 and microtubule-associated protein light chain 3 (LC3). The average temperature-humidity index during the dry period was 77.7, which indicated that HT and CL cows were exposed to significant heat stress. However, the cooling system effectively alleviated heat strain in CL cows by decreasing the rectal temperature (39.0 vs. 39.4°C) and respiration rate (47.3 vs. 71.2 breaths per minute) relative to HT cows. Protein expression of autophagy-related protein 7, a marker for early autophagosome formation, did not change within or between groups. In contrast, protein expression of LC3-II, a marker of autophagosomes, and its precursor LC3-I showed a dynamic expression pattern in MG from CL cows during the early dry period. Relative to HT cows, MG from CL cows displayed higher expression of LC3-I and LC3-II on d 7 and lower expression of LC3-II on d 14 and 22 after dry-off. Collectively, our data provide a possible mechanistic explanation for the impairment of MG capacity in HT dairy cows. Heat stress–related perturbations of autophagic activity may compromise the regenerative MG involution that is necessary for optimal cell proliferation.

Nutrition, Metabolic Status and Reproductive Efficiency in Dairy Herds

Nutrition of transition period in dairy cows dramatically increases requirements for energy, glucose, amino acids and other nutrients in dairy cows and, parallel to that, feed intake is depressed. An insufficient or imbalanced nutrient intake might lead to the malfunction of organs, causing reproductive failure. To minimize the metabolic/reproductive damage caused by negative energy balance (NEBAL), feeding of a glucogenic and lipogenic diet containing fat-enriched supplements is recommended. In heat-stressed dairy cows, the reduction of dry matter intake causes an energy deficit, thereby accentuating NEBAL. Heat stress may also have a direct impact on oocyte quality due to the high ovarian temperatures. The intrauterine environment is also compromised in heat-stressed cows, with reduced blood flow to the uterus and increased uterine temperature; this may impair embryonic development, increase early embryonic loss and reduce the proportion of successful inseminations. Postpartum NEBAL suppresses immune function and promotes metabolic disorders, potentially explaining relationships between infectious and noninfectious transition disorders. In postpartum dairy cows, pathologic ovarian phenomena including ovulatory (cystic corpora lutea) and non-ovulatory (follicular and luteal cysts) forms frequently occur causing decreased fertility. The main objective of this review was summarizing the most relevant information regarding nutrition and reproduction in dairy cows.

Acute brief heat stress in late gestation alters neonatal calf innate immune functions

Heat stress, as one of the environmental stressors affecting the dairy industry, compromises the cow milk production, immune function, and reproductive system. However, few studies have looked at how prenatal heat stress (HS) affects the offspring. The objective of this study was to evaluate the effect of HS during late gestation on calf immunity. Calves were born to cows exposed to evaporative cooling (CT) or HS (cyclic 23–35°C) for 1 wk at 3 wk before calving. Both bull and heifer calves (CT, n=10; HS, n=10) were housed in similar environmental temperatures after birth. Both CT and HS calves received 3.78 L of pooled colostrum within 12 h after birth and were fed the same diet throughout the study. In addition to tumor necrosis factor α, IL-1β, IL-1 receptor antagonist (IL-1RA), and toll-like receptor (TLR)2, and TLR4 mRNA expression, the expression of CD14+ and CD18+ cells, and DEC205+ dendritic cells were determined in whole blood samples at d 0, 3, 7, 14, 21, and 28. The neutrophil to lymphocyte ratio, differential cell counts, and the hematocrit were also determined. During late gestation, the HS cows had greater respiration rates, rectal temperatures, and tended to spend more time standing compared with the CT cows. The HS calves had less expression of tumor necrosis factor-α and TLR2 and greater levels of IL-1β, IL-1RA, and TLR4 compared with CT calves. The HS calves also had a greater percentage of CD18+ cells compared with the CT calves. Additionally, a greater percentage of neutrophils and lesser percentage of lymphocytes were in the HS calves compared with the CT calves. The results indicate that biomarkers of calves’ immunity are affected in the first several weeks after birth by HS in the dam during late gestation.

Late-gestation heat stress abatement on performance and behavior of Holstein dairy cows

The objective of this study was to evaluate cooling to lessen the effects of heat stress during the last 3 wk of gestation on performance and behavior of multiparous Holstein cows. Twenty nonlactating cows were randomly assigned to treatments approximately 21 d before their expected calving date based on mature equivalent milk production and parity. Treatments were only imposed during the last 3 wk of gestation and included heat stress (HT; n=10) and cooling (CL; n=10), both under a similar photoperiod (14 h of light and 10 h of dark). Dry cows were housed in a sand-bedded stall with the stall areas for CL cows equipped with sprinklers and fans that were on from 0700 to 1900 h, whereas those for the HT cows were not. After parturition, all cows were housed in a barn with cooling devices. Rectal temperatures were measured daily at 1400 h and respiration rates were recorded by counting the flank movements for 1 min at 1500 h on odd days over the last 3 wk of gestation to calving. Daily dry matter intake was measured from –21 d relative to expected calving to 21 d after calving and milk production was recorded daily up to 180 d in milk. Behavioral changes of dry cows were studied continuously for 24 h at –10 d relative to expected calving. The average temperature-humidity index during the last 3 wk of gestation was 69.7 and was not significantly different between treatments. Heat-stressed cows exhibited greater rectal temperatures (39.5 vs. 39.2°C), greater respiration rates (70.4 vs. 63.3 breaths/min), and decreased dry matter intake (13.7 vs. 15.5kg/d) compared with CL cows. Compared with HT cows, CL cows produced more milk during 180 d in milk (40.5 vs. 44.6kg/d). Heat stress decreased ruminating (243.2 vs. 282.5 min/d) and chewing times (390.6 vs. 448.7 min/d) at –10 d before calving. The CL cows had shorter standing times than their HT counterparts (390.4 vs. 474.0 min/d). These results confirm that heat stress abatement in the late gestation period improves performance of dairy cows in subsequent lactation.

Data from identification of diagnostic biomarkers and metabolic pathway shifts of heat-stressed lactating dairy cows.

Controlling heat stress (HS) is a global challenge for the dairy industry. In this work, an integrated metabolomics and lipidomics approach using 1H nuclear magnetic resonance (NMR) and ultra-fast LC–MS in combination with multivariate analyses was employed to investigate the discrimination of plasma metabolic profiles between HS-free and HS lactating dairy cows. Here we provide the information about the acquiring and processing of raw data obtained by 1H NMR and LC–MS techniques. The data of present study are related to the research article “Identification of diagnostic biomarkers and metabolic pathway shifts of heat-stressed lactating dairy cows” in the Journal of Proteomics (Tian et al., J. Proteomics, (2015), doi:10.1016/j.jprot.2015.04.014).

Metabolic Heat Stress Adaption in Transition Cows: Differences in Macronutrient Oxidation between Late-Gestating and Early-Lactating German Holstein Dairy Cows.

High ambient temperatures have severe adverse effects on biological functions of high-yielding dairy cows. The metabolic adaption to heat stress was examined in 14 German Holsteins transition cows assigned to two groups, one heat-stressed (HS) and one pair-fed (PF) at the level of HS. After 6 days of thermoneutrality and ad libitum feeding (P1), cows were challenged for 6 days (P2) by heat stress (temperature humidity index (THI) = 76) or thermoneutral pair-feeding in climatic chambers 3 weeks ante partum and again 3 weeks post-partum. On the sixth day of each period P1 or P2, oxidative metabolism was analyzed for 24 hours in open circuit respiration chambers. Water and feed intake, vital parameters and milk yield were recorded. Daily blood samples were analyzed for glucose, β-hydroxybutyric acid, non-esterified fatty acids, urea, creatinine, methyl histidine, adrenaline and noradrenaline. In general, heat stress caused marked effects on water homeorhesis with impairments of renal function and a strong adrenergic response accompanied with a prevalence of carbohydrate oxidation over fat catabolism. Heat-stressed cows extensively degraded tissue protein as reflected by the increase of plasma urea, creatinine and methyl histidine concentrations. However, the acute metabolic heat stress response in dry cows differed from early-lactating cows as the prepartal adipose tissue was not refractory to lipolytic, adrenergic stimuli, and the rate of amino acid oxidation was lower than in the postpartal stage. Together with the lower endogenous metabolic heat load, metabolic adaption in dry cows is indicative for a higher heat tolerance and the prioritization of the nutritional requirements of the fast-growing near-term fetus. These findings indicate that the development of future nutritional strategies for attenuating impairments of health and performance due to ambient heat requires the consideration of the physiological stage of dairy cows.

Relationships between heat stress and metabolic and milk parameters in dairy cows in Southern Brazil.

This study approached the relationships between heat stress and metabolic and milk parameters in a commercial herd of Holstein cows located in southern Brazil. A total of 50 multiparous cows at different lactations and lactation stages were selected in order to obtain 450 samples during two consecutive years (2011 and 2012). The animals were fed a partial mixed ration along with ryegrass pasture in a semi-confinement system. Blood, milk, and urine samples were taken during the summer and winter for a total of eight samples. Three intervals of temperature-humidity index (THI) were established during the summer months (January and February) as follows: low group (LOW), THI between 75 and 81 (N = 100); moderate group (MOD), THI between 81 and 82 (N = 150); and severe group (SEV), THI between 83 and 90 (N = 150). The group of cows sampled during winter (July) constituted the control group (CON; THI = 59, N = 50). Increased total protein, albumin, glucose, and cholesterol occurred in heat-stressed cows. Increased AST activity was also observed in heat-stressed cows, but triglycerides and beta-OH-butyrate did not show any difference among groups. Lower lactate and higher pO2 were seen in cows with heat stress than CON. Cows in SEV had a 21% milk yield decrease, while lactose and protein decreased with fat not being affected. Heat stress had strong effects on metabolic, clinical, and performance parameters in Holstein cows.