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

Abstract

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.

The control of short-term feed intake by metabolic oxidation in late-pregnant and early lactating dairy cows exposed to high ambient temperatures

“…Transition as compared to mid-lactating cows possess a lower COX but a greater FOX rate, demonstrating the high contribution of FOX to the energy charge and thus the impact on the control of feed intake during the transition period.Heat-stressed lactating cows as compared to lactating cows that on a lower plane of nutrition do not appear to mobilize adipose tissue despite reduced DMI[31]. Constant NEFA concentration during heatstress[14,31] should not alter FOX and in agreement with this assumption we found that daily FOX did not respond to HS exposure. However, early-lactating but not dry cows exposed to HS showed a trend towards an increased time-lag between meal and the postprandial minimum of FOX, indicating that a meal ingested under HS condition delays postprandial FOX.…”

“…Heat stress considerably increases water losses due to increased 324 sweating and breathing thereby increasing the requirements for water 325 [14,24]. In the present study, daily WI was not significantly different be-326 tween pre-partum cows kept either under TN or HS conditions, and sur-327 prisingly, WI of post-partum cows was even lower under HS conditions.…”

Prediction of drinking water intake by dairy cows

“…1 Seif et al, 1973;Woodford et al, 1984;Silanikove et al, 1997;Osborne et al, 2002bOsborne et al, , 2009Kojima et al, 2005;Kume et al, 2010;Khelil-Arfa et al, 2014;Lamp et al, 2015. …”

Auswirkungen hoher Umgebungstemperaturen auf laktierende Milchkühe – unter praxisüblichen Bedingungen in Norddeutschland von Bedeutung?

“…Ergebnisse Trotz der bereits zu Beginn des Beobachtungszeitraumes recht hohen Außentemperaturen (19,(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23),0° C im Tagesmittel) traten während einer Hitzeperiode (bis zu 27,9° C im Tagesmittel) deutliche Reduktionen in der Trockensubstanzaufnahme aus der Teil-TMR (ca. -15 %) und der Milchleistung (ca.…”