Nutritional interventions for dairy calves undergoing weaning and heat stresses
Date
2022-12
Authors
Wickramasinghe, Handagala Kaluwalaya Janaka Priyankara
Major Professor
Advisor
Appuhamy Jayasooriya, Ranga
Baumgard, Lance H
Gorden, Patrick J
Koltes, Dawn A
Tyler, Howard D
Committee Member
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Abstract
Dairy calves experience marked growth depressions during weaning and heat stress. Inflammation and oxidative stress are responsible for a considerable portion of that growth depression, and represent serious animal welfare concerns. The intestinal barrier function impairment is a leading cause of inflammation in young animals undergoing weaning or exposed to heat stress. As far as weaning is concerned, step-down weaning schemes are proposed to mitigate the growth slumps and associated stresses. However, the literature suggests the need to optimize those schemes to achieve expected outcomes. Despite the environmental management tools such as fans and misters to mitigate heat stress, the subpar performance of heat-stressed cattle demands nutritional interventions to mitigate the intestinal barrier function damage, inflammation, and oxidative stress. Data on pigs and poultry show that functional amino acids such as glutamine (Gln) and branched-chain amino acids (BCAA), and phytogenic feed additives (PFA) are promising strategies to alleviate the negative consequences of weaning and heat stress. This dissertation focused on evaluating those nutritional interventions in weaning and heat-stressed calves under the hypothesis that the effects seen in monogastric species would be true for dairy calves.
Chapter 2 describes a study to examine the effects of a Gln supplementation (2.0% of DMI) in a step-down weaning scheme on starter feed intake (SFI), average daily gain (ADG), paracellular permeability of intestinal epithelium (PPIE), and inflammation markers of dairy heifer calves weaned from a high milk volume (9.0 L/d). The step-down weaning was initiated by decreasing the milk volume to 3.0 L/d, and calves continued to receive the 3.0 L/d milk until they were weaned completely with a 1.0 kg/d SFI. Glutamine was fed dissolved in the 3.0 L/d milk, and PPIE was determined with lactulose: D-mannitol (LMR) in blood serum 1.0 h after feeding those sugars in milk using gas chromatography-mass spectrometry (GC-MS). The responses of calves beginning the scheme at 35 d of age with, or without Gln were compared with that of calves beginning the scheme without Gln at 49 d of age (n = 12). Additionally, an in vitro experiment with calf intestinal epithelial cells (CIEC) was conducted to elucidate the impact of Gln on the tight junction protein abundance and the localization to the cell membrane. The in vivo study results revealed that the milk volume restriction at 35 d negated ADG during weaning. The supplementation of Gln tended to increase the ADG to a level similar to that of calves beginning weaning without Gln at 49 d. Calves with Gln increased the SFI faster and completed weaning 3 d earlier than calves without Gln (51 vs. 54 d of age). Despite the SFI increase, serum BCAA concentrations decreased more rapidly in calves with vs. without Gln. Regardless of the age, weaning without Gln increased LMR 7 d after the milk restriction, whereas calves with Gln did not experience such an LMR increase. Blood haptoglobin, and LPS-binding protein concentrations, however, increased earlier than the LMR increase suggesting that inflammation might have preceded the PPIE increase in response to the milk volume restriction. The in vitro experiment results revealed a 2 to 3-fold increase in tight junction protein expression in CIEC when media Gln concentration increased from 0.0 to ≥5.0 mM. The extracellular Gln supplementation improved energy status but did not affect the localization of tight junction proteins to the cell membrane of CIEC. Overall, the supplementation of Gln at 2.0% of DMI could improve ADG and preserve intestinal barrier function of dairy calves weaned from a high milk volume without affecting post-weaning growth or SFI.
In the following study (Chapter 3), the Gln supplementation was decreased from 2.0 to 1.0% of DMI as the literature showed that the 1.0% supplementation was related to >5.0 mM Gln in the intestinal lumen of weaning piglets. Moreover, the 1.0% supplementation of Gln improved feed intake, ADG, and immune responses of piglets undergoing weaning and transportation stresses. Given the critical roles of BCAA as precursors and stimulatory signals in muscle growth, BCAA at the ratio of milk protein (17, 10, and 11 g/d Leu, Ile, and Val, respectively) were supplemented with the 1.0% Gln dose (~8.0 g/d). The Gln and BCAA supplementations were hypothesized to mitigate additively the growth slump of dairy calves undergoing the step-down weaning from a high milk volume at an early age of 35 d (n = 11). As observed in the previous experiment, the milk volume restriction (9.0 to 3.0 L/d) negated the ADG, but the 1.0% Gln supplementation did not affect ADG, SFI, or the efficiency (ADG: SFI) during weaning (35 to ~50 d of age). The supplementation of Gln and BCAA tended to increase ADG without affecting SFI and ADG: SFI during weaning. Neither Gln nor Gln+BCAA supplementations affected blood haptoglobin concentrations during weaning. Paradoxically, Gln and Gln+BCAA supplementations during weaning were associated with 9 and 18% decreases in SFI post-weaning (~50 to 70 d of age). Those SFI decreases were positively and negatively associated with plasma serotonin and leptin concentrations determined on the last day of the amino acid supplementations, respectively. Glutamine and BCAA fed in milk during weaning seemed to exert sustained and negative effects on the feed intake of dairy calves by modulating hormones secreted by the gastrointestinal tract.
Chapter 4 covers a study, which was aimed to evaluate a PFA added to a total mixed ration on DMI, ADG, indices of hyperthermia, and antioxidant and anti-inflammatory markers of weaned heifer calves (5-6 months old) subjected to a cyclic heat stress bout (HS) in the summer. Calves were fed total mixed ration with or without PFA (n = 11) for 7 d under usual summer conditions (the baseline), and then subjected to HS employed by setting the barn temperature at 33 °C during the daytime (0900 to 2000 h) for 7 d. Similar to what was observed with weaning, HS negated ADG relative to the baseline. However, the growth slump was not related to a DMI decrease indicating a substantial diversion of nutrients from growth, a significant energy efficiency decreases of growth, or both in response to HS. Calves decrease DMI during the day but ate more during the night making DMI similar between HS and the baseline. The PFA increased DMI during the day but did not affect the total daily DMI. Rectal temperature (>40 °C) and respiration rate (>120 breaths/min) indicated similar degrees of hyperthermia in calves with and without PFA. The blood carbon dioxide decreased, but oxygen increased in response to PFA postulating increased blood flow to the lungs, and perhaps to the periphery during HS. The blood inflammation markers, serum haptoglobin and plasma LPS-binding protein increased in calves without PFA while calves with PFA did not experience such a change in response to HS. Moreover, blood oxidative stress markers, plasma L-lactate, thiobarbituric acid reactive substances, protein carbonyl, and cortisol concentrations were lower in calves with PFA than calves without PFA during HS.
In summary, weaning from a high milk volume and summer heat stress bouts can result in substantial growth depression in dairy calves. The weaning-associated growth slumps were primarily a result of slow SFI increase and thus prolonged nutrient deficiencies. Nevertheless, the elevated blood markers of intestinal barrier function damage and inflammation of weaning calves indicate that energy diverted to other functions such as immune system activation could contribute to some part of the weight gain decline. The improved intestinal barrier function and weight gain improvement for Gln supplementation during weaning attest to such contribution. Nevertheless, supplementation of functional amino acids such as Gln and BCAA during weaning could negatively affect post-weaning SFI. Further investigation into the mechanisms involving those effects would explain the negative link between high milk volumes and SFI as Gln and BCAA represent a major part of free and protein-bound amino acid pools in milk. The diurnal heatwaves in the summer would not change daily DMI, as calves seem to consume more during the night to compensate for the DMI losses during extremely hot daytime. Despite the unchanged DMI, summer heat waves can result in zero weight gain in calves possibly due to the diversion of energy from growth to functions involved in thermoregulation and immune system activation. Feeding PFA often known to possess anti-inflammatory and antioxidant properties could improve health and wellbeing, but may not be potent enough to improve the weight gain of calves exposed to intense heat stress episodes. Nevertheless, further investigations into PFA addressing the variability in inclusion rates, diet composition, feeding duration, and interaction with other heat abatement practices would yield a better understanding of their potential to improve the growth of heat-stressed calves.
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dissertation