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Dietary Betaine Impacts the Physiological Responses to Moderate Heat Conditions in a Dose Dependent Manner in Sheep

View Article: PubMed Central - PubMed

ABSTRACT

Simple summary: Heat stress in sheep initiates physiological methods to dissipate heat that result in decreased production. This study investigated the use of a dietary supplement, the osmolyte betaine fed at two doses (2 or 4 g/day), on the physiological responses to heat in sheep. Heat exposure initiated physiological responses such as an increased rectal temperature and respiration rate as expected, while betaine supplemented at 2 g/day ameliorated these responses. Thus, dietary betaine supplementation may have beneficial effects for sheep exposed to heat.

Abstract: Heat exposure (HE) results in decreased production in ruminant species and betaine is proposed as a dietary mitigation method. Merino ewes (n = 36, 40 kg, n = 6 per group) were maintained at thermoneutral (TN, n = 18, 21 °C) or cyclical HE (n = 18, 18–43 °C) conditions for 21 days, and supplemented with either 0 (control), 2 or 4 g betaine/day. Sheep had ad libitum access to water and were pair fed such that intake of sheep on the TN treatment matched that of HE animals. Heart rate (HR), respiration rate (RR), rectal (TR) and skin temperatures (TS) were measured 3 times daily (0900 h, 1300 h, 1700 h). Plasma samples were obtained on 8 days for glucose and NEFA analysis. The HE treatment increased TR by 0.7 °C (40.1 vs. 39.4 °C for HE and TN respectively p < 0.001), TS by +1.8 °C (39.3 vs. 37.5 °C, p < 0.001) and RR by +46 breaths/min (133 vs. 87 breaths/min, p < 0.001) compared to TN. The 2 g betaine/day treatment decreased TR (39.8, 39.6 and 39.8 °C, p < 0.001), TS (38.7, 38.0 and 38.5 °C, p < 0.001) and RR (114, 102 and 116 breaths/min for control, 2 and 4 g betaine/day, p < 0.001) compared to control. Betaine supplementation decreased plasma NEFA concentrations by ~25 μM (80, 55 and 54 μmol/L for 0, 2 and 4 g/day respectively, p = 0.05). These data indicate that dietary betaine supplementation at 2 g betaine/day provides improvements in physiological responses typical of ewes exposed to heat stress and may be a beneficial supplement for the management of sheep during summer.

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Mean (a) rectal temperature; (b) skin temperature; (c) heart rate and (d) respiration rate responses to 0 (□), 2 (Δ) and 4 (◊) g betaine/day in sheep (Merino ewe’s, n = 6 sheep per group) exposed to thermoneutral (TN) conditions (solid lines) and 0 (■), 2 (▲) and 4 (♦) g dietary betaine/day in sheep exposed to heat (HE) conditions (dashed lines). Data are mean ± sed for environmental temperature × betaine treatment × time of day pooled across the 21 d study. The p-values for the effects of time, environmental temperature and dietary betaine on rectal temperature and respiration rate were <0.001, <0.001 and <0.001 respectively. The p-values for the effects of time, environmental temperature and dietary betaine on skin temperature were <0.001, <0.001 and <0.001 respectively. The p-values for the effects of time, environmental temperature and dietary betaine on heart rate were <0.001, <0.001 and <0.001 respectively. See text for description of day effects and interactions.
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animals-06-00051-f001: Mean (a) rectal temperature; (b) skin temperature; (c) heart rate and (d) respiration rate responses to 0 (□), 2 (Δ) and 4 (◊) g betaine/day in sheep (Merino ewe’s, n = 6 sheep per group) exposed to thermoneutral (TN) conditions (solid lines) and 0 (■), 2 (▲) and 4 (♦) g dietary betaine/day in sheep exposed to heat (HE) conditions (dashed lines). Data are mean ± sed for environmental temperature × betaine treatment × time of day pooled across the 21 d study. The p-values for the effects of time, environmental temperature and dietary betaine on rectal temperature and respiration rate were <0.001, <0.001 and <0.001 respectively. The p-values for the effects of time, environmental temperature and dietary betaine on skin temperature were <0.001, <0.001 and <0.001 respectively. The p-values for the effects of time, environmental temperature and dietary betaine on heart rate were <0.001, <0.001 and <0.001 respectively. See text for description of day effects and interactions.

Mentions: The average TR (across all time points and weeks) was lower in sheep exposed to the TN compared to HE environment (39.4 vs. 40.1 °C, sed 0.049, Figure 1a; p < 0.001). The TR was greatest at 1700 h in HE sheep (39.3, 39.4 and 39.4 °C for TN and 39.5, 40.3 and 40.4 °C for HE at 0900 h, 1300 h and 1700 h respectively, sed 0.039, p < 0.001). Rectal temperature was influenced by experimental day (p < 0.001) and an interaction between day and temperature such that TR was greater in HE sheep and increased with experimental day in both HE and TN sheep (data not shown). When summarized by week a similar pattern was noted such that TR was greater in week 3 compared with weeks 1 and 2 (39.7, 39.7 and 39.8 °C for weeks 1 to 3 respectively, sed 0.065, p = 0.015). Over the course of the experiment, the 0900 h TR did not change with experimental week (39.5 and 39.4 °C for weeks 1 vs. 3 respectively). Progressively, TR increased at 1300 h and 1700 h as experimental week advanced (39.8 and 40.0 °C for weeks 1 and 3 at both 1300 and 1700 h respectively, sed 0.06, p < 0.001), indicating a general reduction in the ability of sheep to adapt to the chronic heat load.


Dietary Betaine Impacts the Physiological Responses to Moderate Heat Conditions in a Dose Dependent Manner in Sheep
Mean (a) rectal temperature; (b) skin temperature; (c) heart rate and (d) respiration rate responses to 0 (□), 2 (Δ) and 4 (◊) g betaine/day in sheep (Merino ewe’s, n = 6 sheep per group) exposed to thermoneutral (TN) conditions (solid lines) and 0 (■), 2 (▲) and 4 (♦) g dietary betaine/day in sheep exposed to heat (HE) conditions (dashed lines). Data are mean ± sed for environmental temperature × betaine treatment × time of day pooled across the 21 d study. The p-values for the effects of time, environmental temperature and dietary betaine on rectal temperature and respiration rate were <0.001, <0.001 and <0.001 respectively. The p-values for the effects of time, environmental temperature and dietary betaine on skin temperature were <0.001, <0.001 and <0.001 respectively. The p-values for the effects of time, environmental temperature and dietary betaine on heart rate were <0.001, <0.001 and <0.001 respectively. See text for description of day effects and interactions.
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Related In: Results  -  Collection

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animals-06-00051-f001: Mean (a) rectal temperature; (b) skin temperature; (c) heart rate and (d) respiration rate responses to 0 (□), 2 (Δ) and 4 (◊) g betaine/day in sheep (Merino ewe’s, n = 6 sheep per group) exposed to thermoneutral (TN) conditions (solid lines) and 0 (■), 2 (▲) and 4 (♦) g dietary betaine/day in sheep exposed to heat (HE) conditions (dashed lines). Data are mean ± sed for environmental temperature × betaine treatment × time of day pooled across the 21 d study. The p-values for the effects of time, environmental temperature and dietary betaine on rectal temperature and respiration rate were <0.001, <0.001 and <0.001 respectively. The p-values for the effects of time, environmental temperature and dietary betaine on skin temperature were <0.001, <0.001 and <0.001 respectively. The p-values for the effects of time, environmental temperature and dietary betaine on heart rate were <0.001, <0.001 and <0.001 respectively. See text for description of day effects and interactions.
Mentions: The average TR (across all time points and weeks) was lower in sheep exposed to the TN compared to HE environment (39.4 vs. 40.1 °C, sed 0.049, Figure 1a; p < 0.001). The TR was greatest at 1700 h in HE sheep (39.3, 39.4 and 39.4 °C for TN and 39.5, 40.3 and 40.4 °C for HE at 0900 h, 1300 h and 1700 h respectively, sed 0.039, p < 0.001). Rectal temperature was influenced by experimental day (p < 0.001) and an interaction between day and temperature such that TR was greater in HE sheep and increased with experimental day in both HE and TN sheep (data not shown). When summarized by week a similar pattern was noted such that TR was greater in week 3 compared with weeks 1 and 2 (39.7, 39.7 and 39.8 °C for weeks 1 to 3 respectively, sed 0.065, p = 0.015). Over the course of the experiment, the 0900 h TR did not change with experimental week (39.5 and 39.4 °C for weeks 1 vs. 3 respectively). Progressively, TR increased at 1300 h and 1700 h as experimental week advanced (39.8 and 40.0 °C for weeks 1 and 3 at both 1300 and 1700 h respectively, sed 0.06, p < 0.001), indicating a general reduction in the ability of sheep to adapt to the chronic heat load.

View Article: PubMed Central - PubMed

ABSTRACT

Simple summary: Heat stress in sheep initiates physiological methods to dissipate heat that result in decreased production. This study investigated the use of a dietary supplement, the osmolyte betaine fed at two doses (2 or 4 g/day), on the physiological responses to heat in sheep. Heat exposure initiated physiological responses such as an increased rectal temperature and respiration rate as expected, while betaine supplemented at 2 g/day ameliorated these responses. Thus, dietary betaine supplementation may have beneficial effects for sheep exposed to heat.

Abstract: Heat exposure (HE) results in decreased production in ruminant species and betaine is proposed as a dietary mitigation method. Merino ewes (n = 36, 40 kg, n = 6 per group) were maintained at thermoneutral (TN, n = 18, 21 &deg;C) or cyclical HE (n = 18, 18&ndash;43 &deg;C) conditions for 21 days, and supplemented with either 0 (control), 2 or 4 g betaine/day. Sheep had ad libitum access to water and were pair fed such that intake of sheep on the TN treatment matched that of HE animals. Heart rate (HR), respiration rate (RR), rectal (TR) and skin temperatures (TS) were measured 3 times daily (0900 h, 1300 h, 1700 h). Plasma samples were obtained on 8 days for glucose and NEFA analysis. The HE treatment increased TR by 0.7 &deg;C (40.1 vs. 39.4 &deg;C for HE and TN respectively p &lt; 0.001), TS by +1.8 &deg;C (39.3 vs. 37.5 &deg;C, p &lt; 0.001) and RR by +46 breaths/min (133 vs. 87 breaths/min, p &lt; 0.001) compared to TN. The 2 g betaine/day treatment decreased TR (39.8, 39.6 and 39.8 &deg;C, p &lt; 0.001), TS (38.7, 38.0 and 38.5 &deg;C, p &lt; 0.001) and RR (114, 102 and 116 breaths/min for control, 2 and 4 g betaine/day, p &lt; 0.001) compared to control. Betaine supplementation decreased plasma NEFA concentrations by ~25 &mu;M (80, 55 and 54 &mu;mol/L for 0, 2 and 4 g/day respectively, p = 0.05). These data indicate that dietary betaine supplementation at 2 g betaine/day provides improvements in physiological responses typical of ewes exposed to heat stress and may be a beneficial supplement for the management of sheep during summer.

No MeSH data available.


Related in: MedlinePlus