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32 pages, 3613 KB

Open AccessFeature PaperArticle

Stress and Strain: Differentiating the Responses to High and Moderate Heat Loads and Subsequent Recovery in Grain-Fed Feedlot Steers—Plasma Biochemistry

by Gene Wijffels, Sally Stockwell, Suzie Briscoe, Yutao Li, Russell McCulloch and John B. Gaughan

Animals 2026, 16(9), 1379; https://doi.org/10.3390/ani16091379 - 30 Apr 2026

Viewed by 886

Abstract

The extent of, and limits of, the metabolic flexibility of feedlot cattle to cope with heat loads of varying intensity and duration is a research gap. Two cohorts of 12 Black Angus steers were housed in climate-controlled rooms (CCR) and subjected to three [...] Read more.

The extent of, and limits of, the metabolic flexibility of feedlot cattle to cope with heat loads of varying intensity and duration is a research gap. Two cohorts of 12 Black Angus steers were housed in climate-controlled rooms (CCR) and subjected to three thermal periods: PreChallenge (5 days), Challenge (7 days) and Recovery (5 days). PreChallenge and Recovery provided thermoneutral conditions. The Challenge simulated a strong heatwave. Finally, the steers were returned to outdoor pens for 20 days. The animals were bled on days 3, 5, 7, 8, 9, 10, 11, 12, 13, 15, 17, 24 and 38. A clinical plasma biochemistry panel was used to measure the concentrations of major metabolites and electrolytes. During Challenge, energy metabolites fell (except for β-hydroxybutyrate). Creatinine, urea and total bilirubin rose rapidly. In Recovery, the major liver enzymes were released into plasma, and total bilirubin remained high. Most analytes showed non-linear relationships with core temperatures during Challenge, suggesting threshold-dependent responses rather than gradual dose-dependent adjustments. The responses and relationships differed from those reported for moderate heat load challenge and recovery. We integrated the metabolic changes over the course of the experiment with previously reported metabolic hormone and physiological responses of these steers. Full article

(This article belongs to the Special Issue Effects of Heat Stress on Animal Reproduction and Production)

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22 pages, 1117 KB

Open AccessArticle

An Econometric Analysis of Climatic Effects on Total Factor Productivity Across U.S. Dairy Counties

by Kamil Bora Bolat, Merve Bolat and Boris E. Bravo-Ureta

Animals 2026, 16(1), 30; https://doi.org/10.3390/ani16010030 - 22 Dec 2025

Viewed by 1127

Abstract

High-yielding dairy cows are particularly vulnerable to heat stress, a challenge that climate change exacerbates. To quantify the impact of climatic variables on productivity, we applied a random parameter stochastic production frontier model to the United States Department of Agriculture (USDA) census data [...] Read more.

High-yielding dairy cows are particularly vulnerable to heat stress, a challenge that climate change exacerbates. To quantify the impact of climatic variables on productivity, we applied a random parameter stochastic production frontier model to the United States Department of Agriculture (USDA) census data from 1978 to 2022 for 179 dairy counties, allowing us to decompose total factor productivity growth (TFPG). Our analysis indicates that technological advancements were the primary driver of TFPG, amounting to 2.52% annually. While these gains are modestly constrained by heat stress, the average impact on the overall TFPG rate was only 0.008% per year. This minimal impact is consistent with the adoption of strategies such as cooling systems and improved management. Even in the most affected counties, the effect remained slight, with the largest reduction reaching 0.08%. This limited impact suggests that the sector’s adoption of technologies and management strategies appears to have mitigated potential productivity losses. This study highlights that future research is needed to quantify the direct impact of specific on-farm adaptation strategies on dairy productivity to inform well-targeted policy recommendations. Full article

(This article belongs to the Special Issue Effects of Heat Stress on Animal Reproduction and Production)

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14 pages, 468 KB

Open AccessArticle

Physiological Responses and Pregnancy Rate of Black and White Holstein Heifers During Hot and Cold Seasons in a Desert Region

by Leonel Avendaño-Reyes, Emiliano Corrales-Navarro, Ulises Macías-Cruz, María de los Ángeles López-Baca, José A. Roque-Jiménez, Peter H. Robinson, Miguel Mellado and Joaquín Hernández

Animals 2025, 15(23), 3458; https://doi.org/10.3390/ani15233458 - 30 Nov 2025

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Abstract

Our aim was to compare certain physiological traits and pregnancy rates in dairy heifers classified by coat color during summer and winter months in a Sonoran Desert region. Sixty Holstein heifers were randomly selected (age and weight of 13.1 ± 0.82 months and [...] Read more.

Our aim was to compare certain physiological traits and pregnancy rates in dairy heifers classified by coat color during summer and winter months in a Sonoran Desert region. Sixty Holstein heifers were randomly selected (age and weight of 13.1 ± 0.82 months and 382 ± 5.3 kg) and divided by season (i.e., winter and summer) and hair coat color (i.e., black and white). There were 28 summer heifers (13 black/15 white) and 32 in winter (18 black/14 white). Respiratory frequency (RF) was determined visually, and body surface temperatures (BSTs) of several anatomic regions were collected using thermography at 06:00 and 15:00 h every 3rd day. Furthermore, three blood samples were collected from each heifer in each season to determine hematological profiles and serum analytes (i.e., electrolytes, metabolites, hormones). Reproductive variables were pregnancy rate and services per pregnancy. Ambient temperatures ranged from 25 to 49 °C in summer and 3 to 28 °C in winter. In summer and winter, RF and most BST were higher (p < 0.05) in black heifers in the morning, while only head, right flank, and loin were higher (p < 0.05) in the afternoon. Cortisol and progesterone concentrations were higher (p < 0.01) in summer, while thyroid hormones were higher (p < 0.05) in winter. Glucose, triglycerides, cholesterol, urea, and sodium were higher (p < 0.05) in winter. Reproductive traits were unaffected by season or coat color. Although there were some differences in physiological variables and some biochemical parameters by season and coat color, these alterations were not enough to modify reproductive responses of Holstein heifers. Full article

(This article belongs to the Special Issue Effects of Heat Stress on Animal Reproduction and Production)

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18 pages, 1647 KB

Open AccessFeature PaperArticle

Thiamine Diphosphate Supplementation as a Heat-Stress Mitigation Strategy for Hair Male and Female Lambs in Feedlot: Physiological Responses, Growth Performance, and Carcass Traits

by Ulises Macías-Cruz, German Castillo Cristóbal, Leonel Avendaño-Reyes, María de los Ángeles López-Baca, José A. Roque-Jiménez, Miguel Mellado, César A. Meza-Herrera, Ricardo Vicente-Pérez, Marisol López-Romero and Nallely Rivero-Pérez

Animals 2025, 15(21), 3143; https://doi.org/10.3390/ani15213143 - 29 Oct 2025

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Abstract

Twenty Dorper × Katahdin lambs (10 males and 10 females) were distributed in a 2 × 2 factorial arrangement under a randomized complete block design to evaluate the effects of thiamine diphosphate (TD) supplementation (0 vs. 250 mg/kg feed) and gender (males vs. [...] Read more.

Twenty Dorper × Katahdin lambs (10 males and 10 females) were distributed in a 2 × 2 factorial arrangement under a randomized complete block design to evaluate the effects of thiamine diphosphate (TD) supplementation (0 vs. 250 mg/kg feed) and gender (males vs. females) on physiological responses, feedlot performance, carcass characteristics, and meat quality in a hot desert environment. The average temperature and temperature–humidity index recorded during the study were 33.60 °C and 35.89 units, respectively, indicating an extremely severe heat stress environment for lambs. Study variables were not affected (p ≥ 0.12) by the TD × gender interaction, except for dry matter intake (DMI; p = 0.02) and some head temperatures (p ≤ 0.05) and carcass zoometric measurements (p ≤ 0.05). In females, but not in males, TD decreased DMI and increased thorax depth, as well as eye, ear, and forehead temperatures. Overall, TD increased (p ≤ 0.05) surface temperatures of neck, shoulder, loin, rump, forelimb, testicles, vulva, anus, and perineum without affecting (p ≥ 0.58) rectal temperature and respiratory rate. Supplemental TD did not affect (p ≥ 0.16) growth rate, feed efficiency, carcass weight and yield, Longissimus thoracic muscle area, backfat thickness, internal fat deposition, wholesale cut yields, and meat quality traits. In conclusion, in hair ewe lambs but not in male lambs, TD supplementation at a dose of 250 mg/kg of feed in the fattening diet is an HS mitigation strategy that improves dietary energy efficiency for growth and carcass mass deposition. Furthermore, thiamine increases heat losses through the body surface, regardless of gender. Full article

(This article belongs to the Special Issue Effects of Heat Stress on Animal Reproduction and Production)

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18 pages, 2525 KB

Open AccessFeature PaperArticle

Seasonal Heat Stress and the Postpartum Stage Interactively Influence Milk Fatty Acid Composition in Holstein Dairy Cows in Spain

by Elena Niceas Martínez Diez, Rodrigo Muiño Otero, Cristina Castillo Rodríguez and Joaquín Hernández Bermúdez

Animals 2025, 15(21), 3119; https://doi.org/10.3390/ani15213119 - 27 Oct 2025

Cited by 3 | Viewed by 1002

Abstract

Climate change is intensifying heat stress conditions in livestock systems, posing significant challenges to animal welfare, productivity, and food quality. This study aims to investigate the combined effects of seasonal heat stress and postpartum physiology on the milk fatty acid (FA) profile of [...] Read more.

Climate change is intensifying heat stress conditions in livestock systems, posing significant challenges to animal welfare, productivity, and food quality. This study aims to investigate the combined effects of seasonal heat stress and postpartum physiology on the milk fatty acid (FA) profile of Holstein dairy cows in Galicia, Spain. Forty milk samples were collected during winter and summer and at 1 week and 1 month postpartum. Fatty acid composition was analyzed via gas chromatography (GC-FID), and heat stress exposure was quantified using the temperature–humidity index (THI). Results revealed that heat stress significantly altered the milk lipid profile, with increased concentrations of short- and medium-chain fatty acids (SMCFA) such as C10:0 and C14:1 (n-5), and conjugated linoleic acids (CLAs), suggesting enhanced de novo lipogenesis and shifts in rumen fermentation. Conversely, unsaturated long-chain fatty acids (LCFAs), including cis-11 C18:1 and cis-13 C18:1, decreased with lactation progression and thermal exposure. Notably, certain LCFAs remained stable under combined seasonal and physiological stress, indicating potential metabolic regulation. These results show how milk composition is sensitive to environmental stress and emphasize the need for climate-resilient management to protect milk quality under global warming. Full article

(This article belongs to the Special Issue Effects of Heat Stress on Animal Reproduction and Production)

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16 pages, 2062 KB

Open AccessFeature PaperArticle

Effects of an Immunomodulatory Supplement and Evaporative Cooling on Immune Status, Mammary Gland Microstructure, and Gene Expression of Cows Exposed to Heat Stress During the Dry Period

by Thiago F. Fabris, Jimena Laporta, Fabiana N. Corra, Yazielis M. Torres, David J. Kirk, James D. Chapman and Geoffrey E. Dahl

Animals 2025, 15(21), 3113; https://doi.org/10.3390/ani15213113 - 27 Oct 2025

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Abstract

Nutritional and cooling strategies to abate the negative effects of heat stress during the dry period have been used to improve the performance of dairy cattle. The objective of this study was to evaluate the effects of feeding an immunomodulatory supplement (OmniGen-AF^® [...] Read more.

Nutritional and cooling strategies to abate the negative effects of heat stress during the dry period have been used to improve the performance of dairy cattle. The objective of this study was to evaluate the effects of feeding an immunomodulatory supplement (OmniGen-AF^®, OMN) before, during, and after exposure to either heat stress or active cooling during the dry period on immune function and mammary development in dairy cows. During late lactation (at least 60 d before dry off), cows were provided with evaporative cooling systems (shade, fans, and soakers) and assigned to two groups: placebo (56 g/d of AB20^® top-dressed; CON) or OmniGen-AF^® (OMN, 56 g/d top-dressed). Cows were dried off ~46 d before the expected calving date and further split into evaporative cooling (shade, fans, and soakers; CL) or heat stress (only shade; HT) pens. Thus, after dry off, there were four treatment groups: heat stress with placebo (HT, n = 17), HT with OMN supplementation (HT + OMN, n = 19), CL with placebo (CL, n = 16), and CL with OMN supplementation (CL + OMN, n = 11). From a subset of cows (n = 6–8 per group), four blood samples were collected during the dry period (−43, −39, −32, and −21 d relative to calving) to evaluate neutrophil function and blood hematology. In addition, mammary biopsies (4–6 cows/treatment) were collected at −43, −39, −32, and −21 d relative to calving to evaluate mammary gland gene expression and histology, i.e., Tdt dUTP nick-end labeling (TUNEL) and Ki67. Genes related to autophagy, apoptosis, and cell proliferation were analyzed by qRT-PCR. Relative to CL, HT downregulated the expression of beclin-2 (BECN2) but upregulated the expression of beclin-1 (BECN1) on days −43 and −39 relative to calving, respectively. Also, relative to CL, HT upregulated the expression of BAX and FAS on day −39 relative to calving. These differences in gene expression were followed by HT cows having a lower total cell apoptosis rate during involution relative to CL cows. Further to these effects, HT leads to a lower alveoli number relative to CL cows. As in the CL treatment, OMN cows have a higher total cell apoptosis rate and alveoli number relative to CON cows. In addition, OMN cows have higher total cell proliferation relative to CON. Prolactin (PRL) and cortisol concentrations were evaluated during the dry period at days −45, −26, −3, and −1 relative to calving. Relative to CL, HT cows had higher PRL at day −45 but lower PRL on day −1 relative to calving, and a similar trend was observed for cortisol concentrations. In summary, HT impacts mammary gland gene expression, compromises mammary involution, reduces alveoli number, and alters hormone dynamics throughout the dry period. Following the same trends as the CL treatment, OMN increases mammary gland turnover by having a higher cell apoptosis and cell proliferation rate and lower connective tissue relative to CON cows. Full article

(This article belongs to the Special Issue Effects of Heat Stress on Animal Reproduction and Production)

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12 pages, 838 KB

Open AccessArticle

Heat Stress and Betaine Affect Lipolysis in Pig Adipose Tissue Explants

by Zaira Pardo, Manuel Lachica, Rosa Nieto, Isabel Seiquer and Ignacio Fernández-Fígares

Animals 2025, 15(19), 2845; https://doi.org/10.3390/ani15192845 - 29 Sep 2025

Viewed by 1286

Abstract

Heat stress (HS) is an environmental variable challenging pig production worldwide. It may alter carcass composition by increasing fat deposition but the mechanisms are poorly understood. Betaine is a metabolic modifier able to decrease carcass fat in pigs, but the effects of betaine [...] Read more.

Heat stress (HS) is an environmental variable challenging pig production worldwide. It may alter carcass composition by increasing fat deposition but the mechanisms are poorly understood. Betaine is a metabolic modifier able to decrease carcass fat in pigs, but the effects of betaine on lipolysis under high temperatures are not known. Our goal was to determine a potential effect of betaine on lipolysis in the fat tissue of Iberian pigs under thermoneutral (TN) or HS conditions. Eight pigs (89 kg BW) were used to obtain explants from dorsal subcutaneous adipose tissue. Explants were cultivated under TN (37 °C) or HS conditions (41.5 °C) for 1.5 h to study direct effects of HS on acute lipolysis. Treatments included control and betaine addition (200 µM). Indirect effects of HS were examined using the culture medium amended with 1 μM isoproterenol ±10 nM insulin in the presence or absence of betaine and HS. Media glycerol was measured at the end of the incubations as a proxy of lipolysis. HS decreased basal lipolysis (−47%; p < 0.001) but increased isoproterenol-stimulated (a β-agonist) lipolysis (+31%; p < 0.01). Betaine increased non-stimulated lipolysis both under TN and HS conditions (73%; p < 0.001). As expected, isoproterenol augmented lipolysis both in TN (2714%; p < 0.001) and HS (3589%; p < 0.001) conditions. The addition of insulin to lipolysis-stimulated explants analogously diminished glycerol release in TN (−39%; p < 0.001) and HS (−50%; p < 0.001) conditions. In conclusion, HS reduced non-stimulated lipolysis in Iberian pigs in line with increased adipose tissue accretion, while betaine partly increased lipolysis, counteracting the effects of HS. Betaine supplementation could be a strategy to counteract HS-induced fattening in pigs. Full article

(This article belongs to the Special Issue Effects of Heat Stress on Animal Reproduction and Production)

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17 pages, 5739 KB

Open AccessArticle

Impact of Heat Stress on Gene Expression in the Hypothalamic–Pituitary–Ovarian Axis of Hu Sheep

by Jianwei Zou, Lili Wei, Yishan Liang, Juhong Zou, Pengfei Cheng, Zhihua Mo, Wenyue Sun, Yirong Wei, Jun Lu, Wenman Li, Yulong Shen, Xiaoyan Deng, Yanna Huang and Qinyang Jiang

Animals 2025, 15(15), 2189; https://doi.org/10.3390/ani15152189 - 25 Jul 2025

Cited by 3 | Viewed by 2495

Abstract

Heat stress (HS) is a major environmental factor negatively impacting the reproductive performance of livestock. This study investigates the molecular mechanisms of heat stress on the hypothalamic–pituitary–ovarian (HPO) axis in Hu sheep. A heat-stressed animal model was established, and high-throughput RNA sequencing (RNA-seq) [...] Read more.

Heat stress (HS) is a major environmental factor negatively impacting the reproductive performance of livestock. This study investigates the molecular mechanisms of heat stress on the hypothalamic–pituitary–ovarian (HPO) axis in Hu sheep. A heat-stressed animal model was established, and high-throughput RNA sequencing (RNA-seq) was employed to analyze gene expression in the hypothalamus, pituitary, and ovarian tissues of both control and heat-stressed groups. The results revealed significant changes in estrus behavior, hormone secretion, and reproductive health in heat-stressed sheep, with a shortened estrus duration, prolonged estrous cycles, and decreased levels of FSH, LH, E₂, and P4. A total of 520, 649, and 482 differentially expressed genes (DEGs) were identified in the hypothalamus, pituitary, and ovary, respectively. The DEGs were enriched in pathways related to hormone secretion, neurotransmission, cell proliferation, and immune response, with significant involvement of the p53 and cAMP signaling pathways. Tissue-specific responses to heat stress were observed, with distinct regulatory roles in each organ, including GPCR activity and cytokine signaling in the hypothalamus, calcium-regulated exocytosis in the pituitary, and cilium assembly and ATP binding in the ovary. Key genes such as SYN3, RPH3A, and IGFBP2 were identified as central to the coordinated regulation of the HPO axis. These findings provide new insights into the molecular basis of heat stress-induced impairments in reproductive function—manifested by altered estrous behavior, reduced hormone secretion (FSH, LH, E₂, and P4), and disrupted gene expression in the hypothalamic–pituitary–ovarian (HPO) axis—and offer potential targets for improving heat tolerance and reproductive regulation in sheep. Full article

(This article belongs to the Special Issue Effects of Heat Stress on Animal Reproduction and Production)

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