Agriculture and Agri-Food Canada, the National Sciences and Engineering Council of Canada (NSERC)... more Agriculture and Agri-Food Canada, the National Sciences and Engineering Council of Canada (NSERC), the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA), the Canadian Dairy Commission (CDC), and the Dairy Farmers of Ontario (DFO).
The objective of the study was to determine the effect of active dry Saccharomyces cerevisiae (AD... more The objective of the study was to determine the effect of active dry Saccharomyces cerevisiae (ADSC) supplementation on dry matter intake, milk yield, milk components, ruminal pH, and microbial community during a dietary regimen that leads to subacute ruminal acidosis (SARA). Sixteen multiparous, rumen-cannulated lactating Holstein cows were randomly assigned to 1 of 2 dietary treatments that included ADSC (Biomate; AB Vista, Marlborough, UK; 8 × 10(10) cfu/head per day) or control. During wk 1 to 6, all cows received a high-forage (HF) diet (77:23, forage:concentrate). Cows were then abruptly switched during wk 7 to a high-grain (HG) diet (49:51, forage:concentrate) and remained on the HG until the end of wk 10. Feed intake and milk yields were recorded daily. Ruminal pH was recorded continuously using an indwelling system for 1 to 2 d per week during the pre-experimental phase, and wk 6, 7, and 10. Ruminal digesta samples were collected at the end of the experiment and analyzed fo...
Chlortetracycline (CTC) is commonly administered to young animals at subtherapeutic levels to opt... more Chlortetracycline (CTC) is commonly administered to young animals at subtherapeutic levels to optimize growth efficiency. However, how CTC alters mammalian metabolism is poorly described. The goal of this experiment was to compare the profile of proteins expressed by the livers of growing steers that contained none versus subtherapeutic levels of CTC. Protein was extracted from homogenates, resolved (500 μg) by 2-D gel electrophoresis, visualized with Sypro-ruby, and the amount of fluorescence among analogous “spots” (proteins) compared. CTC-treatment increased (P < 0.034) expression of 8 proteins and reduced that of (P < 0.043) 12 proteins. Affected proteins were digested with trypsin, peptide fragments subjected to MALDI-TOF analysis, and peptide mass spectra compared (MASCOT) to Swiss-Prot proteins. Collectively these analyses revealed that GBRA5 (20%), UN13B (131%), SPAT2 (89%), SSX5 (89%), and PRDX6 (161%) was increased and that of ASCC2, MT1A, and SRY was detected, whereas the expression of PDE6B (3...
The molecular mechanisms underlying rumen epithelial adaption to high-grain (HG) diets are unknow... more The molecular mechanisms underlying rumen epithelial adaption to high-grain (HG) diets are unknown. To gain insight into the metabolic mechanisms governing epithelial adaptation, mature nonlactating dairy cattle ( n = 4) were transitioned from a high-forage diet (HF, 0% grain) to an HG diet (65% grain). After the cattle were fed the HG diet for 3 wk, they returned to the original HF diet, which they were fed for an additional 3 wk. Continuous ruminal pH, ruminal short chain fatty acids, and plasma β-hydroxybutyrate were measured on a weekly basis, and rumen papillae were biopsied from the ventral sac to assess alterations in mRNA expression profiles. The subacute form of ruminal acidosis was diagnosed during the first week of the HG period (4.6 ± 1.6 h/day
The effects of health management strategy during rearing on subsequent growth performance and ind... more The effects of health management strategy during rearing on subsequent growth performance and indicators of immune system stimulation in grower-finisher (G-F) pigs were evaluated. Pigs of approximately 25 kg body weight (BW) were sourced from three different management systems: (1) a farrow-to-finish unit with identified respiratory problems (Conventional), (2) segregated early weaned (SEW; piglets sourced from multiple sow herds), and (3) a minimal disease farrow-to-finish operation (MD). The pigs were of similar genetic background and were housed under similar conditions until slaughter. During the grower phase, MD had the highest average daily gain (ADG) (P < 0.05), while it was similar for SEW and Conventional (P > 0.10). Feed to gain (F:G) was similar for MD and SEW (P > 0.10), and poorest for Conventional (P < 0.05). During the finisher phase, SEW had the lowest ADG, and the poorest F:G (P < 0.05); these parameters were similar for Conventional and MD (P > 0....
There is a growing body of evidence to suggest direct involvement of the cytokines interleukin-1 ... more There is a growing body of evidence to suggest direct involvement of the cytokines interleukin-1 (IL-1), interleukin-6 (IL-6) and tumour necrosis factor-α (TNF-α) in the initiation of skeletal muscle catabolism and depressions in growth performance as a result of diseases, while TNF-α and IL-6 are presumably under the control of IL-1. An experiment was conducted to investigate whether an interleukin-1 receptor antagonist (IL-1ra) could reduce growth depressions in a model of subclinical disease in growing pigs. In this study, 24 crossbred barrows and gilts were randomly assigned to three treatments: (1) healthy control (HC), saline infusion; (2) sick control (SC), infection with Mycoplasma hyopneumoniae and vaccination with porcine reproductive and respiratory syndrome modified live virus (PRRSV) vaccine and saline infusion; (3) SC plus infusion with IL-1ra (SC+IL-1ra). An additional six pigs were killed at the initiation of the trial to determine initial body composition for estima...
American Journal of Animal and Veterinary Sciences, 2012
The objective of this study was to characterize the mRNA and protein expression of inflammatory a... more The objective of this study was to characterize the mRNA and protein expression of inflammatory and structural genes in the rumen epithelium during grain-induced ruminal acidosis in lactating dairy cattle. A total of 16 rumen-fistulated, lactating Holstein dairy cattle (618±35 kg of body weight, 221±32 days in milk) were used in a randomized complete block design study. All cattle were initially fed a high-forage diet (HF; 88.9% of dry matter) and after a baseline (wk 0) measurement, half of the cattle were randomly assigned and transitioned to a high-concentrate diet (HC; 62.2% of dry matter) which was fed for 3 weeks (weeks 1, 2 and 3). Continuous ruminal pH, ruminal LPS and plasma LPS-binding protein were measured each week followed by a rumen papillae biopsy used for mRNA and protein quantification. After the baseline period, ruminal LPS was higher in HC compared to HF cattle (28851±6905 vs. 5771±3042 EU mL −1). There was no difference in mRNA expression of inflammatory and structure genes in rumen papillae between HF and HC cattle during all weeks. With regard to protein expression, there was an up regulation (p = 0.02) of nuclear factor of activated T-cells cytoplasmic 2 expression during weeks 1, 2 and 3; however, all other inflammatory markers within the rumen epithelium were unchanged by treatment. These results suggest that although graininduced ruminal acidosis leads to characteristic whole-animal inflammatory response, only marginal changes in inflammatory and structural gene and protein expression in the rumen epithelium were detected.
American Journal of Animal and Veterinary Sciences, 2012
Problem statement: Subacute Ruminal Acidosis (SARA) is a metabolic disorder affecting approximate... more Problem statement: Subacute Ruminal Acidosis (SARA) is a metabolic disorder affecting approximately 20% of all dairy cattle in North America. Although the presence of SARA has been described for some time, the etiology of the disorder remains uncertain. For example, many animals diagnosed with SARA seem to remodel and adapt their epithelium to accommodate the stresses imposed by SARA, but not before exacting a significant health and economic toll. Specifically, a search is on in which a desire to identify the system and associated pathways that are causative agents in the progression and development of SARA is evident. We hypothesize that adaptation to SARA is facilitated by the immune system. Approach: In order to answer of this question, 4 mature, nonlactating dairy cattle were transitioned from a High Fiber (HF; 0% grain) diet to High Grain (HG; 65% grain) diet. Having fed the HG diet for three weeks, the cattle were then transitioned back to the HF diet for an additional three weeks to facilitate adaptation. SARA was diagnosed by pH data only during the first week and not during the remaining weeks, indicating that adaptation to the HG diet took place within one week. Results: In this study, significant (p<0.05) extracellular matrix protein changes (COL4A1, LAMB1) were seen during this study indicating a change in matrix architecture to facilitate adaptation. In addition, similar significant (p<0.05) patterns of expression of inflammatory cytokines and mediators of the LPS-mediated toll-like receptor pathway were seen. Conclusion: These results indicate that the immune system is involved in the adaptation of the rumen epithelium to a HG diet, but to a lesser extent than was previously thought. This is the first time an attempt has been made to link the immune system and wound healing in the adaptation of the bovine rumen to a HG diet.
American Journal of Animal and Veterinary Sciences, 2013
Subacute Ruminal Acidosis (SARA) is a disorder in cattle which can lead to chronic inflammation i... more Subacute Ruminal Acidosis (SARA) is a disorder in cattle which can lead to chronic inflammation in the rumen epithelium, known as rumenitis. Butyrate has been shown to attenuate some of the detrimental effects of inflammatory gastroenteral disorders but the molecular mechanisms mediated by butyrate have not been defined. The objective of this study was to define the inflammatory-related genomic changes responsible for the beneficial effects of butyrate. Experimentally, 16 fistulated dairy cows at mid-lactation were fed a SARA-inducing (45% non-fiber carbohydrate) diet beginning 2 days before the beginning of treatment and continuing throughout the experiment. Cows were then evenly divided into treatment groups where a carrier with (n = 8) or without (n = 8) supplemental butyrate (2.5% initial DM intake) was deposited into the rumen daily for 7 days. The minimum rumen pH was higher in cows with supplemental butyrate (4.96±0.09 to 5.20±0.05, p = 0.040), but mean pH, maximum pH and the duration for which rumen pH was below 5.6 was unaffected. Free plasma Lipopolysaccharide (LPS) concentration was unaffected by treatment as was the concentration of Serum Amyloid A (SAA), although the LPS Binding Protein (LBP) concentration was increased by the addition of butyrate to the rumen (6.91±0.29 to 7.93±0.29 µg mL −1 , p = 0.024). Of the rumen Short Chain Fatty Acids (SCFA) tested, only butyrate showed a pronounced treatment effect, rising from 8.60±0.94 to 21.60±0.94 mM (p≤0.0001). Plasma Beta-Hydroxybutyrate (BHBA) concentration also increased (799.50±265.24 to 3261.63±265.24 µM, p≤0.001). Butyrate infusion did not affect milk parameters (total fat, lactose, total protein and LOS); however, when related to dry matter intake, milk production efficiency was increased (p = 0.035). Microarray and qRT-PCR analyses of rumen papillae biopsies collected on day 7 found that butyrate administration affected (p≤0.05) the expression of genes involved in Non-Specific Host Defense (NSHD), Remodeling or adaptation (RM) and Immune Response (IR). Of the 49 genes tested by qRT
The structural and functional adaption of the rumen epithelium during the transition period is la... more The structural and functional adaption of the rumen epithelium during the transition period is largely undescribed. To characterize the adaptation of the rumen epithelium during transition, multiparous dairy cattle (n=12) fitted with rumen fistulas and fed a low-energy dry cow diet (1.37 Mcal/kg, net energy for lactation) were transitioned abruptly to a high-energy lactating cow diet (1.68 Mcal/kg, net energy for lactation) immediately after parturition. Rumen papillae were biopsied at -3, +1, and +6 wk relative to calving. The histology of morphology of the rumen papillae was evaluated under the light microscope and electron microscope, and mRNA profiling was performed using an Affymetrix GeneChip Bovine Gene 1.0 ST Array (Affymetrix, Santa Clara, CA). Data preprocessing was conducted using the robust multi-array average method, and detection of significant genes was conducted using ANOVA. Also, the Benjamini-Hochberg false discovery rate of 0.1 was applied. Microscopic examination...
The objective of this study was to characterize the mRNA expression of metabolic and proliferativ... more The objective of this study was to characterize the mRNA expression of metabolic and proliferative genes in the rumen epithelium during ruminal acidosis. To meet our objectives, 16 rumen-fistulated, lactating Holstein dairy cattle (618 ± 35 kg of body weight, 221 ± 32 d in milk) were used in a randomized complete block design. All cattle were fed a high-forage diet (HF; 88.9% of dry matter) for 5 wk before the experiment. After the baseline week (wk 0), half of the cattle were randomly assigned and transitioned to a high-concentrate diet (HC; 62.2% of dry matter) which was fed for 3 wk (wk 1, 2, and 3). For the last 48 h of each week, continuous ruminal pH, short-chain fatty acids, and plasma β-hydroxybutyrate were assessed, followed by a rumen papillae biopsy. Milk production was higher in HC cattle compared with HF during wk 1, 2, and 3 (17.4 ± 0.5 vs. 23.4 ± 0.9 kg/d, respectively); however, the mean ruminal pH was decreased (5.75 ± 0.03 vs. 6.30 ± 0.02). The HC cattle spent more time below pH 5.6 (594 ± 54 vs. 3 ± 3 min/d) and displayed greater concentrations of ruminal butyrate (15.8 ± 0.9 vs. 10.2 ± 0.4 mmol) and plasma β-hydroxybutyrate (1,036 ± 63 vs. 778 ± 20 μM) compared with the HF cattle. The mRNA expression of genes involved in ketogenesis (HMGCS2 and PPARA) and short-chain fatty acid transport (MCT1) was unchanged by treatment. However, a downregulation in HMGCS1 (0.72 ± 0.09), one of the cholesterol biosynthesis genes, was observed in HC cattle during wk 1 of the grain challenge. In addition, the relative mRNA expression value of insulinlike growth factor-binding protein 3 was lower (0.78 ± 0.06), whereas insulin-like growth factor-binding protein 5 was higher (1.79 ± 0.15) in HC compared with HF cattle. These results suggest that grain-induced ruminal acidosis alters the mRNA expression of IGFbinding proteins and a cholesterolgenic enzyme in the rumen epithelium of lactating dairy cattle.
Agriculture and Agri-Food Canada, the National Sciences and Engineering Council of Canada (NSERC)... more Agriculture and Agri-Food Canada, the National Sciences and Engineering Council of Canada (NSERC), the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA), the Canadian Dairy Commission (CDC), and the Dairy Farmers of Ontario (DFO).
The objective of the study was to determine the effect of active dry Saccharomyces cerevisiae (AD... more The objective of the study was to determine the effect of active dry Saccharomyces cerevisiae (ADSC) supplementation on dry matter intake, milk yield, milk components, ruminal pH, and microbial community during a dietary regimen that leads to subacute ruminal acidosis (SARA). Sixteen multiparous, rumen-cannulated lactating Holstein cows were randomly assigned to 1 of 2 dietary treatments that included ADSC (Biomate; AB Vista, Marlborough, UK; 8 × 10(10) cfu/head per day) or control. During wk 1 to 6, all cows received a high-forage (HF) diet (77:23, forage:concentrate). Cows were then abruptly switched during wk 7 to a high-grain (HG) diet (49:51, forage:concentrate) and remained on the HG until the end of wk 10. Feed intake and milk yields were recorded daily. Ruminal pH was recorded continuously using an indwelling system for 1 to 2 d per week during the pre-experimental phase, and wk 6, 7, and 10. Ruminal digesta samples were collected at the end of the experiment and analyzed fo...
Chlortetracycline (CTC) is commonly administered to young animals at subtherapeutic levels to opt... more Chlortetracycline (CTC) is commonly administered to young animals at subtherapeutic levels to optimize growth efficiency. However, how CTC alters mammalian metabolism is poorly described. The goal of this experiment was to compare the profile of proteins expressed by the livers of growing steers that contained none versus subtherapeutic levels of CTC. Protein was extracted from homogenates, resolved (500 μg) by 2-D gel electrophoresis, visualized with Sypro-ruby, and the amount of fluorescence among analogous “spots” (proteins) compared. CTC-treatment increased (P < 0.034) expression of 8 proteins and reduced that of (P < 0.043) 12 proteins. Affected proteins were digested with trypsin, peptide fragments subjected to MALDI-TOF analysis, and peptide mass spectra compared (MASCOT) to Swiss-Prot proteins. Collectively these analyses revealed that GBRA5 (20%), UN13B (131%), SPAT2 (89%), SSX5 (89%), and PRDX6 (161%) was increased and that of ASCC2, MT1A, and SRY was detected, whereas the expression of PDE6B (3...
The molecular mechanisms underlying rumen epithelial adaption to high-grain (HG) diets are unknow... more The molecular mechanisms underlying rumen epithelial adaption to high-grain (HG) diets are unknown. To gain insight into the metabolic mechanisms governing epithelial adaptation, mature nonlactating dairy cattle ( n = 4) were transitioned from a high-forage diet (HF, 0% grain) to an HG diet (65% grain). After the cattle were fed the HG diet for 3 wk, they returned to the original HF diet, which they were fed for an additional 3 wk. Continuous ruminal pH, ruminal short chain fatty acids, and plasma β-hydroxybutyrate were measured on a weekly basis, and rumen papillae were biopsied from the ventral sac to assess alterations in mRNA expression profiles. The subacute form of ruminal acidosis was diagnosed during the first week of the HG period (4.6 ± 1.6 h/day
The effects of health management strategy during rearing on subsequent growth performance and ind... more The effects of health management strategy during rearing on subsequent growth performance and indicators of immune system stimulation in grower-finisher (G-F) pigs were evaluated. Pigs of approximately 25 kg body weight (BW) were sourced from three different management systems: (1) a farrow-to-finish unit with identified respiratory problems (Conventional), (2) segregated early weaned (SEW; piglets sourced from multiple sow herds), and (3) a minimal disease farrow-to-finish operation (MD). The pigs were of similar genetic background and were housed under similar conditions until slaughter. During the grower phase, MD had the highest average daily gain (ADG) (P < 0.05), while it was similar for SEW and Conventional (P > 0.10). Feed to gain (F:G) was similar for MD and SEW (P > 0.10), and poorest for Conventional (P < 0.05). During the finisher phase, SEW had the lowest ADG, and the poorest F:G (P < 0.05); these parameters were similar for Conventional and MD (P > 0....
There is a growing body of evidence to suggest direct involvement of the cytokines interleukin-1 ... more There is a growing body of evidence to suggest direct involvement of the cytokines interleukin-1 (IL-1), interleukin-6 (IL-6) and tumour necrosis factor-α (TNF-α) in the initiation of skeletal muscle catabolism and depressions in growth performance as a result of diseases, while TNF-α and IL-6 are presumably under the control of IL-1. An experiment was conducted to investigate whether an interleukin-1 receptor antagonist (IL-1ra) could reduce growth depressions in a model of subclinical disease in growing pigs. In this study, 24 crossbred barrows and gilts were randomly assigned to three treatments: (1) healthy control (HC), saline infusion; (2) sick control (SC), infection with Mycoplasma hyopneumoniae and vaccination with porcine reproductive and respiratory syndrome modified live virus (PRRSV) vaccine and saline infusion; (3) SC plus infusion with IL-1ra (SC+IL-1ra). An additional six pigs were killed at the initiation of the trial to determine initial body composition for estima...
American Journal of Animal and Veterinary Sciences, 2012
The objective of this study was to characterize the mRNA and protein expression of inflammatory a... more The objective of this study was to characterize the mRNA and protein expression of inflammatory and structural genes in the rumen epithelium during grain-induced ruminal acidosis in lactating dairy cattle. A total of 16 rumen-fistulated, lactating Holstein dairy cattle (618±35 kg of body weight, 221±32 days in milk) were used in a randomized complete block design study. All cattle were initially fed a high-forage diet (HF; 88.9% of dry matter) and after a baseline (wk 0) measurement, half of the cattle were randomly assigned and transitioned to a high-concentrate diet (HC; 62.2% of dry matter) which was fed for 3 weeks (weeks 1, 2 and 3). Continuous ruminal pH, ruminal LPS and plasma LPS-binding protein were measured each week followed by a rumen papillae biopsy used for mRNA and protein quantification. After the baseline period, ruminal LPS was higher in HC compared to HF cattle (28851±6905 vs. 5771±3042 EU mL −1). There was no difference in mRNA expression of inflammatory and structure genes in rumen papillae between HF and HC cattle during all weeks. With regard to protein expression, there was an up regulation (p = 0.02) of nuclear factor of activated T-cells cytoplasmic 2 expression during weeks 1, 2 and 3; however, all other inflammatory markers within the rumen epithelium were unchanged by treatment. These results suggest that although graininduced ruminal acidosis leads to characteristic whole-animal inflammatory response, only marginal changes in inflammatory and structural gene and protein expression in the rumen epithelium were detected.
American Journal of Animal and Veterinary Sciences, 2012
Problem statement: Subacute Ruminal Acidosis (SARA) is a metabolic disorder affecting approximate... more Problem statement: Subacute Ruminal Acidosis (SARA) is a metabolic disorder affecting approximately 20% of all dairy cattle in North America. Although the presence of SARA has been described for some time, the etiology of the disorder remains uncertain. For example, many animals diagnosed with SARA seem to remodel and adapt their epithelium to accommodate the stresses imposed by SARA, but not before exacting a significant health and economic toll. Specifically, a search is on in which a desire to identify the system and associated pathways that are causative agents in the progression and development of SARA is evident. We hypothesize that adaptation to SARA is facilitated by the immune system. Approach: In order to answer of this question, 4 mature, nonlactating dairy cattle were transitioned from a High Fiber (HF; 0% grain) diet to High Grain (HG; 65% grain) diet. Having fed the HG diet for three weeks, the cattle were then transitioned back to the HF diet for an additional three weeks to facilitate adaptation. SARA was diagnosed by pH data only during the first week and not during the remaining weeks, indicating that adaptation to the HG diet took place within one week. Results: In this study, significant (p<0.05) extracellular matrix protein changes (COL4A1, LAMB1) were seen during this study indicating a change in matrix architecture to facilitate adaptation. In addition, similar significant (p<0.05) patterns of expression of inflammatory cytokines and mediators of the LPS-mediated toll-like receptor pathway were seen. Conclusion: These results indicate that the immune system is involved in the adaptation of the rumen epithelium to a HG diet, but to a lesser extent than was previously thought. This is the first time an attempt has been made to link the immune system and wound healing in the adaptation of the bovine rumen to a HG diet.
American Journal of Animal and Veterinary Sciences, 2013
Subacute Ruminal Acidosis (SARA) is a disorder in cattle which can lead to chronic inflammation i... more Subacute Ruminal Acidosis (SARA) is a disorder in cattle which can lead to chronic inflammation in the rumen epithelium, known as rumenitis. Butyrate has been shown to attenuate some of the detrimental effects of inflammatory gastroenteral disorders but the molecular mechanisms mediated by butyrate have not been defined. The objective of this study was to define the inflammatory-related genomic changes responsible for the beneficial effects of butyrate. Experimentally, 16 fistulated dairy cows at mid-lactation were fed a SARA-inducing (45% non-fiber carbohydrate) diet beginning 2 days before the beginning of treatment and continuing throughout the experiment. Cows were then evenly divided into treatment groups where a carrier with (n = 8) or without (n = 8) supplemental butyrate (2.5% initial DM intake) was deposited into the rumen daily for 7 days. The minimum rumen pH was higher in cows with supplemental butyrate (4.96±0.09 to 5.20±0.05, p = 0.040), but mean pH, maximum pH and the duration for which rumen pH was below 5.6 was unaffected. Free plasma Lipopolysaccharide (LPS) concentration was unaffected by treatment as was the concentration of Serum Amyloid A (SAA), although the LPS Binding Protein (LBP) concentration was increased by the addition of butyrate to the rumen (6.91±0.29 to 7.93±0.29 µg mL −1 , p = 0.024). Of the rumen Short Chain Fatty Acids (SCFA) tested, only butyrate showed a pronounced treatment effect, rising from 8.60±0.94 to 21.60±0.94 mM (p≤0.0001). Plasma Beta-Hydroxybutyrate (BHBA) concentration also increased (799.50±265.24 to 3261.63±265.24 µM, p≤0.001). Butyrate infusion did not affect milk parameters (total fat, lactose, total protein and LOS); however, when related to dry matter intake, milk production efficiency was increased (p = 0.035). Microarray and qRT-PCR analyses of rumen papillae biopsies collected on day 7 found that butyrate administration affected (p≤0.05) the expression of genes involved in Non-Specific Host Defense (NSHD), Remodeling or adaptation (RM) and Immune Response (IR). Of the 49 genes tested by qRT
The structural and functional adaption of the rumen epithelium during the transition period is la... more The structural and functional adaption of the rumen epithelium during the transition period is largely undescribed. To characterize the adaptation of the rumen epithelium during transition, multiparous dairy cattle (n=12) fitted with rumen fistulas and fed a low-energy dry cow diet (1.37 Mcal/kg, net energy for lactation) were transitioned abruptly to a high-energy lactating cow diet (1.68 Mcal/kg, net energy for lactation) immediately after parturition. Rumen papillae were biopsied at -3, +1, and +6 wk relative to calving. The histology of morphology of the rumen papillae was evaluated under the light microscope and electron microscope, and mRNA profiling was performed using an Affymetrix GeneChip Bovine Gene 1.0 ST Array (Affymetrix, Santa Clara, CA). Data preprocessing was conducted using the robust multi-array average method, and detection of significant genes was conducted using ANOVA. Also, the Benjamini-Hochberg false discovery rate of 0.1 was applied. Microscopic examination...
The objective of this study was to characterize the mRNA expression of metabolic and proliferativ... more The objective of this study was to characterize the mRNA expression of metabolic and proliferative genes in the rumen epithelium during ruminal acidosis. To meet our objectives, 16 rumen-fistulated, lactating Holstein dairy cattle (618 ± 35 kg of body weight, 221 ± 32 d in milk) were used in a randomized complete block design. All cattle were fed a high-forage diet (HF; 88.9% of dry matter) for 5 wk before the experiment. After the baseline week (wk 0), half of the cattle were randomly assigned and transitioned to a high-concentrate diet (HC; 62.2% of dry matter) which was fed for 3 wk (wk 1, 2, and 3). For the last 48 h of each week, continuous ruminal pH, short-chain fatty acids, and plasma β-hydroxybutyrate were assessed, followed by a rumen papillae biopsy. Milk production was higher in HC cattle compared with HF during wk 1, 2, and 3 (17.4 ± 0.5 vs. 23.4 ± 0.9 kg/d, respectively); however, the mean ruminal pH was decreased (5.75 ± 0.03 vs. 6.30 ± 0.02). The HC cattle spent more time below pH 5.6 (594 ± 54 vs. 3 ± 3 min/d) and displayed greater concentrations of ruminal butyrate (15.8 ± 0.9 vs. 10.2 ± 0.4 mmol) and plasma β-hydroxybutyrate (1,036 ± 63 vs. 778 ± 20 μM) compared with the HF cattle. The mRNA expression of genes involved in ketogenesis (HMGCS2 and PPARA) and short-chain fatty acid transport (MCT1) was unchanged by treatment. However, a downregulation in HMGCS1 (0.72 ± 0.09), one of the cholesterol biosynthesis genes, was observed in HC cattle during wk 1 of the grain challenge. In addition, the relative mRNA expression value of insulinlike growth factor-binding protein 3 was lower (0.78 ± 0.06), whereas insulin-like growth factor-binding protein 5 was higher (1.79 ± 0.15) in HC compared with HF cattle. These results suggest that grain-induced ruminal acidosis alters the mRNA expression of IGFbinding proteins and a cholesterolgenic enzyme in the rumen epithelium of lactating dairy cattle.
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