Feedlot growth, carcass characteristics and meat quality of hair breed male lambs exposed to seasonal heat stress (winter vs. summer) in an arid climate

Effects of herbal formula on growth performance, apparent digestibility, antioxidant capacity, and rumen microbiome in fattening lambs under heat stress

Heat stress (HS) causes severe economic losses in sheep industry worldwide. The objective of the present study was to investigate the effects of a herbal formula (HF) supplement on growth, digestibility, antioxidant capacity, and rumen microbes in fattening lambs under HS. The HF composed of four herbs was prepared based on the theory of compatibility of Chinese medicine "Jun-Chen-Zuo-Shi". Two-hundred forty 3-month weaned lambs (initial weight 36.61 ± 0.73 kg) were randomly allocated into four groups, supplemented 0% (Control), 0.5%, 1.0%, and 1.5% HF in diets. All lambs were exposed to HS conditions with 79.7 of average temperature-humidity index throughout an experimental period of 35 days. Growth performance, apparent digestibility, and antioxidant activities, involving antioxidant enzymes and heat shock proteins (HSPs), were measured at the end of trial, as well as microbial communities in bacteria and archaea. Results showed that 0.5% HF increased (P = 0.02) average daily gain by 13.80% and decreased feed-to-gain ratio (P = 0.03) by 14.68%, compared to control. With increasing HF doses, the digestibility of ether extract and acid detergent fiber demonstrated a cubical (P < 0.01) and quadratic (P = 0.03) relation, respectively; moreover, glutathione peroxidase and catalase activities demonstrated a quadratic increase (P < 0.01). Serum levels of HSP60, HSP70, and HSP90 for 0.5% HF were lower than that in control (P < 0.05). On the other hand, total volatile fatty acid, acetic acid, butyric acid, valeric acid, and isovaleric acid levels exhibited quadratic increases (P ≤ 0.01) with HF doses. From rumen microbes, the abundance and diversity of bacterial community were improved by HF supplements. Particularly for 0.5% HF group, the operational taxonomic units were the greatest among all groups. Compared to control, Prevotella abundance for HF supplements from 0.5 to 1.5% increased by 35.57 to 60.15%, and Succiniclasticum abundance demonstrated a quadratic pattern (P = 0.02) with doses. Additionally, Methanosphaera abundance in archaeal community raised by 0.2 to 3.3-folds when lambs were fed the HF additions of 0.5 to 1.5%. In summary, dietary HF supplements would contribute to alleviating HS in lambs, and our results suggest the optimal dose of 0.5% HF supplement in diet.

Influences of a Supplemental Blend of Essential Oils Plus 25-Hydroxy-Vit-D3 and Zilpaterol Hydrochloride (β2 Agonist) on Growth Performance and Carcass Measures of Feedlot Lambs Finished under Conditions of High Ambient Temperature

Forty-eight Pelibuey × Katahdin male intact lambs (25.12 ± 3.79 kg LW) were used in a 70-d growing-finishing trial. Dietary treatments consisted of total mixed corn-based diet supplemented with: (1) no feed additives (Control); (2) 150 mg of essential oils blend plus 0.10 mg of 25-hydroxy-Vit-D3/kg diet offered throughout the 70-d experimental period (EOD3); (3) Control diet fed during the first 35 days and zilpaterol hydrochloride (ZH) supplementation at 6 mg/kg diet offered during the final 35 days of the experiment (32 days with ZH with a withdrawal 3-d before harvest), and (4) basal diet supplemented with EOD3 during first 35 days finishing, and EOD3 in combination with ZH (EOD3 + ZH) during the subsequent 32-days with ZH withdrawal 3 days before harvest. The temperature-humidity index during the experiment averaged 80.4 ± 3.2. There were no treatment interactions (p > 0.20) on growth performance and carcass measures. Supplemental EOD3 did not affect (p = 0.43) dry matter intake (DMI), but increased (p < 0.01) carcass adjusted average daily gain (ADG, 9.2%), gain efficiency (GF, 6.7%), and observed vs. expected dietary net energy for maintenance (NEm, 4.8%) and for gain (NEg, 6.4%). Supplemental ZH did not affect dry matter intake (DMI, p = 0.50) but increased (p < 0.01) carcass adjusted ADG (14.5%), GF (13%) and observed vs. expected dietary NEm (9%) and NEg (11.7%). Compared to control lambs, the combination of both additives increased ADG (24.9%), GF (21.2%), and observed vs. expected dietary NEm and NEg (14.2% and 18.9%, respectively). There were no treatment interactions on carcass characteristics, visceral organ mass, or on gene expression of IGF1, IGF2 and mTOR in longissimus muscle (LM). Supplemental EOD3 increased hot carcass weight (HCW; 4.0%, p < 0.01) but did not affect other carcass measures. Supplemental EOD3 decreased (3%, p = 0.03) intestine mass weight (g intestine/kg empty body weight). Supplemental ZH increased HCW (6%, p < 0.01), dressing percentage (1.7%, p = 0.04), and LM area (9.7%, p < 0.01), and decreased kidney-pelvic-fat percentage (16.2%, p < 0.01), fat thickness (14.7%, p = 0.03), and visceral fat. Compared to controls, the combination of EOD3 with ZH increased HCW (10.2%). It is concluded that growth performance responses to supplemental EOD3 and ZH are additive. Both supplements can be fed in combination without detrimental effects on expected benefits when fed separately. In addition, ZH supplementation improves carcass traits.

Physicochemical Properties, Antioxidant Markers, and Meat Quality as Affected by Heat Stress: A Review

Heat stress is one of the most stressful events in livestock life, negatively impacting animal health, productivity, and product quality. Moreover, the negative impact of heat stress on animal product quality has recently attracted increasing public awareness and concern. The purpose of this review is to discuss the effects of heat stress on the quality and the physicochemical component of meat in ruminants, pigs, rabbits, and poultry. Based on PRISMA guidelines, research articles were identified, screened, and summarized based on inclusion criteria for heat stress on meat safety and quality. Data were obtained from the Web of Science. Many studies reported the increased incidences of heat stress on animal welfare and meat quality. Although heat stress impacts can be variable depending on the severity and duration, the exposure of animals to heat stress (HS) can affect meat quality. Recent studies have shown that HS not only causes physiological and metabolic disturbances in living animals but also alters the rate and extent of glycolysis in postmortem muscles, resulting in changes in pH values that affect carcasses and meat. It has been shown to have a plausible effect on quality and antioxidant activity. Acute heat stress just before slaughter stimulates muscle glycogenolysis and can result in pale, tender, and exudative (PSE) meat characterized by low water-holding capacity (WHC). The enzymatic antioxidants such as superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) act by scavenging both intracellular and extracellular superoxide radicals and preventing the lipid peroxidation of the plasma membrane. Therefore, understanding and controlling environmental conditions is crucial to successful animal production and product safety. The objective of this review was to investigate the effects of HS on meat quality and antioxidant status.

Ferulic acid supplementation for 40 days in hair ewe lambs experiencing seasonal heat stress: short-term effects on physiological responses, growth, metabolism, and hematological profile

Free ferulic acid (FA) is a natural compound with antioxidant properties which mitigates the negative effects of cold stress in sheep; however, its impact on thermoregulatory responses in heat-stressed sheep has not been defined. The objective was to evaluate the effects of FA supplementation on physiological responses, serum analyte concentrations, and the hematological profile of heat-stressed hair ewe lambs. Twenty-two Dorper × Katahdin ewe lambs (initial body weight = 23.5 ± 2.8 kg and age = 4 months) were housed in individual pens for 40 days and assigned under a randomized complete block design to the following treatments (n = 11): basal diet with 0 (control) or 250 mg of FA/kg of feed. The FA × sampling day interaction only affected serum concentration of some metabolic hormones; particularly on day 20 of the trial, FA increased (P < 0.01) insulins and the insulin to glucose ratio while decreased (P = 0.05) thyroxine. Overall, supplemental FA did not affect rectal temperature, respiratory rate, most body surface temperatures, feedlot performance, and serum concentrations of metabolites, electrolytes, triiodothyronine, and cortisol. In addition, FA only tended to decrease (P ≥ 0.09) erythrocyte count and plaquetocrit and to increase (P = 0.08) mean corpuscular volume. In conclusion, FA supplementation did not improve the growth nor thermoregulatory capacity of heat-stressed hair ewe lambs. Still, it partially modulated the metabolism to reinforce some energetic adaptive mechanisms when the ambient temperature was ≥ 35 °C.

Thermoregulatory Response of Blackbelly Adult Ewes and Female Lambs during the Summer under Tropical Conditions in Southern Mexico

High environmental temperatures cause heat stress in ewes, resulting in thermoregulatory problems. In this study, the thermoregulatory responses of Blackbelly adult ewes (G1, n = 14) and female lambs (G2, n = 7), during the summer under tropical conditions, in southern Mexico were analyzed. Different physiological variables and skin temperatures (ST) of the ewes were recorded. Breathing frequency (BF) values were similar between groups at 116.73 ± 33.598 bpm (G1) and 113.661 ± 34.515 bpm (G2) (p > 0.05). In the case of skin elasticity (SE), there were no significant differences between the time of day and the age of the ewes (p > 0.05). Significant differences were observed between groups for BF, rectal temperature (RT), and heart rate (HR) values (p < 0.05). All ST values, for both groups, were significantly higher during the afternoon (p < 0.001). In general, all Blackbelly adult ewes and female lambs during the summer present severe heat stress conditions as a result of an increase in physiological constants and ST. It is concluded that all ewes thermoregulate body temperature by modifying different physiological variables to counteract the effect of heat stress.

Impact of Heatwaves on the Physiology and Retail Meat Quality of Lambs

The experiment investigated the impact of heatwaves (HWs) on the physiology, postmortem muscle metabolism and meat quality of lambs. Seventy-two second-cross lambs (Poll Dorset × (Border Leicester × Merino)) were selected and exposed to either 1, 3 or 5 days of HWs or thermoneutal (TN) (28–38 °C and 40–60% relative humidity, RH; 18–21 °C, 40–55% RH) conditions in climate-controlled chambers. Lambs exposed to 1–5 days of a HW exhibited higher respiration rates (RRs), rectal temperatures (RTs), skin temperatures (STs) and heart rates (HRs) compared to lambs exposed to an equal duration of TN conditions. However, HWs had no significant effects on muscle metabolism (rate and extent of pH decline, muscle glycogen and lactate content) and meat quality (cooking loss and shear force). Similarly, there were limited impacts of 1–5 days of HW on the colour (L*, a*, b* and R630/580) and drip loss of the longissimus thoracis et lumborum (LTL) and semimembranosus (SM) muscles for 4 days’ overwrap retail display. Results suggest that short-duration HWs (1–5 days) had significant negative effects on animal physiology but had no effect on the muscle metabolism and meat quality.

n-6 Polyunsaturated fatty acids in the feeding of late gestation hair ewes: the effects on thermoregulation, growth, and metabolism of heat-stressed growing lambs

The objective was to determine the effects of feeding soybean oil (SBO), an ingredient rich in n-6 polyunsaturated fatty acids (PUFA), to late gestation hair ewes on physiological responses, feedlot performance, and serum metabolite and electrolyte concentrations of their growing ewe lambs under outdoor heat stress conditions. Twenty-four Dorper × Pelibuey ewe lambs weaned (body weight = 21.5 ± 0.2 kg, age= 2 months, and multiple birth) born from ewes fed 0, 30, or 60 mg of SBO/kg dry matter (DM) during late gestation were selected (n = 8/treatment) to conduct a 30-day feeding trial during the summer season of a desert region (temperature = 34 °C and temperature-humidity index = 35 units). While rectal temperature was unaffected in any daytime, respiratory rate in the afternoon quadratically increased (P = 0.05) as the SBO levels increased from 0 to 60 mg/kg DM in the maternal diet. Final weight, average daily gain, and feed efficiency linearly increased (P = 0.04) with increasing levels of SBO. Body surface temperatures and serum concentration of glucose, cholesterol, triglyceride, total protein, urea, sodium, potassium, and chlorine did not vary by the SBO inclusion in the maternal diet. In conclusion, feeding late gestation hair ewes with source rich in n-6 PUFA appears to be an effective maternal nutritional strategy to improve post-weaning growth without compromising the thermoregulatory ability of their growing offspring under a heat stress environment.

Identifying the heat resistant genes by multi-tissue transcriptome sequencing analysis in Turpan Black sheep

Heat stress not only affects the physical condition but also affects reproductive performance in sheep. A thorough understanding of the molecular and physiological mechanisms underlying heat stress would certainly improve livestock productivity and provide genetic evaluation ways for heat resistant breeds selection. In this study, 85 Turpan Black sheep, a breed exhibited excellent heat resistance from long-term artificial selection, and 85 heat sensitive Kazakh sheep in Turpan basin were tested for physiological and reproductive performance from July to August in summer. The results showed that the estrus rate was significantly higher in Turpan Black sheep (P < 0.05), while the heart rate and respiratory rate of Turpan Black sheep are significantly lower than that of Kazakh sheep (P < 0.05). Furthermore, to clarify genes participated in heat stress response, the pituitary, ovarian and hepatic tissues from three Turpan Black sheep and three Kazakh sheep were subjected to RNA-seq. The results indicated that 32, 49 and 69 genes were up-regulated, and 39, 60 and 145 genes were down-regulated in pituitary, ovarian and hepatic tissues in Turpan Black sheep compared with that of the Kazakh sheep, respectively. KEGG and gene set enrichment analysis showed that the differentially expressed genes were mainly involved in signal transduction pathways. In particular, the differentially expressed genes in hepar were enriched in the energy metabolism pathway, while the differentially expressed genes in ovarian tissue were enriched in the ovarium steroidogenesis pathway. In conclusion, our results implied that the pituitary-ovary axis might include hepar as downstream targeted organism in heat resistant regulation. Under heat stress, the signals released from pituitary would impact steroidogenesis in ovary, and further alter energy metabolism in hepar. As we know, this is the first comparative study to investigate the gene expression in multi-tissue in sheep under heat stress.

The Effects of Single or Combined Supplementation of Probiotics and Prebiotics on Growth Performance, Dietary Energetics, Carcass Traits, and Visceral Mass in Lambs Finished under Subtropical Climate Conditions

Simple Summary

Concern about the use of antimicrobial compounds in livestock production has promoted research of “generally recognized as safe” additive alternatives. Probiotics (living microorganisms) and prebiotics (certain type of carbohydrates derived from yeast) have been shown to alleviate the negative effects of stress and boost immunity, thereby enhancing efficiency of energy utilization. In some regions (i.e., tropical and arid zones), livestock experience adverse climatic conditions, including elevated ambient temperature and humidity, which affect their productivity. Supplementation with probiotics and prebiotics may help to alleviate these adverse effects. In the present study, supplemental probiotics or/and prebiotics improved dietary energetic efficiency in lambs finished under subtropical climatic conditions. The combination of probiotics with prebiotics reinforced this positive effect.

Abstract

The aim of this trial was to test the effects of the use of eubiotics (pro- and prebiotics) alone or in combination in the diet of lambs finished under subtropical climate conditions. For this purpose, 40 Pelibuey × Katahdin lambs (29.5 ± 4.8 kg initial live weight) were used in a 93 day growth-performance experiment. Dietary treatments consisted of a cracked corn-based finishing diet supplemented with (1) no eubiotics (control), (2) 3 g of probiotics (live Saccharomyces cerevisiae, SC), (3) 3 g of prebiotics (mannan oligosaccharide plus b-glucans, MOS), and (4) a combination of 1.5 g of SC and 1.5 g of MOS (SC+MOS). Throughout the study, the average temperature humidity index (THI) was 78.60. Compared to controls, supplementation with SC or MOS, alone did not affect average daily gain (ADG), but enhanced feed efficiency by 5.6% and 6.9% (gain-to-feed ratio, G:F) and dietary net energy by 4.6% and 5.9%, respectively. Compared to controls, SC+MOS enhanced ADG (10%), G:F (9.5%), and dietary net energy (7.2%). Lambs fed SC+MOS had also greater ADG, G:F, and dietary net energy compared to lambs fed SC alone. When compared to MOS, the combination enhanced ADG (10.4%, p = 0.04). This effect could be attributed to the increased dry matter intake (7.6%, p = 0.06), as neither G:F nor dietary energy was significantly affected. Compared with controls and SC, supplementation with MOS alone and SC+MOS increased kidney–pelvic–heart fat, while SC supplementation tended (p = 0.08) to reduce 4.1% the relative intestinal mass (as a proportion of empty body weight) when compared to controls. Treatment effects on the other carcass measures were not significant. In the present study, supplemental probiotics and/or prebiotics improved dietary energetic efficiency in lambs finished under subtropical climatic conditions. The combination of probiotics with prebiotics reinforced this positive effect.

Evaluation of standardized mixture of synbiotic-glyconutrients supplemented in lambs finished during summer season in tropical environment: growth performance, dietary energetics, and carcass characteristics

Twenty-four Pelibuey × Katahdin lambs (36.4 ± 2.9 kg initial weight) were used in a 77 d feeding trial in a randomized complete block design to evaluate the influence of a standardized synbiotic-glyconutrient combination (GLY) on growth performance, dietary energetic, and carcass characteristics of lambs finished during a period of high ambient temperature. Dietary treatments consisted of a high-energy basal diet supplemented (% of diet dry matter basis) with 0% versus 0.4% GLY. Throughout the study, the average temperature humidity index (THI) was 76.23, corresponding to the “alert” range, but daily maximum THI exceeded 80 for 2 to 6 h of each day of the 77 d study. Daily GLY intake averaged 0.10 g GLY·kg−1 live weight. Supplemental GLY increased (P = 0.04) daily water intake, but dry matter intake was not affected. Supplemental GLY increased (P < 0.03) initial 56-d, and overall (77-d) average daily gain, gain efficiency and estimated dietary net energy. Lambs fed GLY had greater (P ≤ 0.05) hot carcass weight and fat thickness, and decreased (P = 0.02) kidney-pelvic-heart fat. Supplemental GLY did not affect (P ≥ 0.16) shoulder tissue composition or relative weight of visceral mass. Synbiotic-glyconutrient combination improved growth performance, dietary energy, and carcass weight in lambs finished in high ambient temperatures. Enhancements in growth performance and dietary energetics were most appreciable during the first 56 d of the 77 d finishing period.

Effect of heat stress on growth and production performance of livestock and poultry: Mechanism to prevention

Heat stress is a widespread phenomenon in domestic animal feeding in tropical and sub-tropical areas that are subjected to a growing negative effect in livestock and poultry due to global warming. It leads to reduced food intake, retarded growth, intestinal disequilibrium, lower reproductive performance, immunity and endocrine disorders in livestock and poultry. Many studies show that the pathogenesis of heat stress is mainly related to oxidative stress, hormone secretion disorder, cytokine imbalance, cell apoptosis, cell autophagy, and abnormal cell function. Its mechanism refers to activation of mitogen-activated protein kinase (MAPK) signaling pathway and nuclear factor kappa B (NF-κB) signaling pathway, the fluctuation of tight junction protein and heat shock protein expression, and protein epigenetic modification. This manuscript reviews the mechanism of heat stress through an insight into the digestive, reproductive, immune, and endocrine system. Lastly, the progress in prevention and control techniques of heat stress has been summarized.

Growth performance and changes in physiological, metabolic and hematological parameters due to outdoor heat stress in hair breed male lambs finished in feedlot

The aim of this study was to evaluate the effect of seasonal heat stress (HS) on productive performance, physiological responses, metabolism, and hematological profile of hair breed male lambs finished in feedlot. Twenty Dorper × Katahdin male lambs (body weight = 34.6 ± 1.4 kg and age = 4.5 months) were housed in individual pens and exposed to environmental conditions of summer HS (n = 10, temperature = 28.3 ± 4.0 °C and THI = 77.2 ± 5.4 units) or winter thermoneutrality (n = 10, temperature = 19.2 ± 2.6 °C and THI = 64.0 ± 3.0 units). Each season, a 30-day feeding test was conducted to measure study variables. Compared to thermoneutral lambs, heat-stressed lambs had lower (P < 0.01) growth rate and feed efficiency without changing dry matter intake. Heat-stressed lambs presented higher (P < 0.01) rectal temperature and respiratory rate through the daytime than termoneutral lambs. On most sampling days, summer HS caused lower (P < 0.01) serum concentrations of glucose, cholesterol, total protein, urea, potassium, and thyroid hormones, but higher (P < 0.01) serum triglyceride and chlorine values. Overall serum concentrations of cortisol and insulin were unaffected by summer HS. The blood of heat-stressed lambs showed lower (P ≤ 0.03) erythrocyte and platelet counts, hemoglobin, and hematocrit, but higher (P ≤ 0.03) erythrocyte size and leucocyte count than the blood of thermoneutral lambs. In conclusion, hair breed male lambs in response to chronic conditions of summer HS had slow growth but avoided hyperthermia due to the activation of physiological, metabolic and endocrine adjustments.

Impact of heat stress on the growth performance and retail meat quality of 2nd cross (Poll Dorset × (Border Leicester × Merino)) and Dorper lambs

The present study investigated the impact of heat stress and genetics on lamb growth performance and meat quality. Forty-eight Dorper and 2nd cross [Poll Dorset × (Border Leicester × Merino)] lambs (38--42 kg; 4-5 months old) were allocated to either thermoneutral [TN; 18-21 °C, 45-55% relative humidity (RH)], or heat stress (HS; 28 °C-38 °C, 40-60% RH) conditions in a 2 × 2 factorial design for 2 weeks. Compared with 2nd cross, Dorper lambs had a lower respiration rate (RR) and rectal temperature (RT), and exhibited less decline in body weight under HS. 2nd cross lambs showed a higher body weight gain than Dorpers under TN conditions. HS increased a* and chroma of the Longissimus thoracis et lumborum (LTL) from 2nd cross lambs over 10 days of display, but had no impact on Dorper LTL. In conclusion, Dorpers showed higher heat tolerance compared with 2nd cross lambs during the 2 weeks HS.