Ruminal pH measurement, prediction, and application in dairy cattle

The experiments presented in this thesis were designed to improve our understanding of subacute ruminal (SARA), rumen function, and their role in milk fat depression. Therefore, the main objective was to develop an animal model to induce a sustainable pH depression. The animal model was utilized to study the association between ruminal pH and ruminal temperature and investigated the effect of ruminal pH on milk fat depression in the presence of polyunsaturated fatty acids. The first experiment was designed to develop a system for the continuous recording of ruminal pH. The system allowed the mobility of animals during recording and was comprised of a heavy-duty pH electrode that was immersed in the rumen and connected to portable pH recorder for data acquisition. Ruminal pH was recorded every minute for 24 hours a day. The second experiment developed the mathematical methodology to predict biological values from ruminal pH measurements. This approach permitted the analysis of ruminal pH measurements from different studies. Continuous ruminal pH measurements from 6 previous SARA studies conducted in our laboratory were analyzed using this approach. This approach improved our understanding of SARA and provided an index to compare the severity of ruminal pH depression across studies. Ruminal pH minima had a high correlation (R2 = 0.77) with ruminal temperature. This indicated that measuring ruminal temperature has the potential to diagnose SARA. The final experiment showed that cows with ruminal pH depression had a greater extent of milk fat depression than cows without ruminal pH depression when soybean oil was infused ruminally. This depression in milk fat was accompanied with a change in the milk fatty acid profile and an increase in the milk concentrations of biohydrogenation intermediates known to depress de novo synthesis of milk fat in the mammary gland

Effect of short-term versus long-term grassland management and seasonal variation in organic and conventional dairy farming on the composition of bulk tank milk

Bulk tank milk from 28 dairy farms was sampled every second month for 2 yr to assess the effects of grassland management, production system and season on milk fatty acid (FA) composition, concentrations of fat-soluble vitamins, Se, and milk sensory quality. Grassland management varied in terms of time since establishment. Short-term grassland management (SG) was defined as establishment or reseeding every fourth year or more often, and long-term grassland management (LG) was defined as less frequent establishment or reseeding. Fourteen organic (ORG) dairy farms with either short-term or long-term grassland management were paired with 14 conventional (CON) farms with respect to grassland management. Within ORG farms, SG farms differed from LG farms in herbage botanical composition, but not in concentrate FA concentrations, dry matter intake, or milk yield. Within CON farms, herbage composition, concentrate FA concentrations, dry matter intake, and milk yield showed no or insignificant variations. The ORG farms differed from CON farms in herbage botanical composition, concentrate FA concentrations, concentrate intake, and milk yield. Compared with ORG-LG farms, ORG-SG farms produced milk fat with higher proportions of C10:0 and C12:0 associated with higher herbage proportions of legumes (Fabaceae) and lower proportions of other dicotyledon families. Compared with milk from CON farms, milk fat from ORG farms had higher proportions of most saturated FA and all n-3 FA, but lower proportions of C18:0 and C18:1 cis-9 associated with higher forage proportion and differences in concentrations of FA in concentrates. Compared with the outdoor-feeding periods, the indoor feeding periods yielded milk fat with higher proportions of most short-chain and medium-chain FA and lower proportions of most C18-FA associated with grazing and higher forage proportions. Milk concentrations of α-tocopherol and β-carotene were lower during the grazing periods. Inclusion of fishmeal in organic concentrates may explain higher Se concentrations in organically produced milk. Milk sensory quality was not affected in this study. In conclusion, grassland management had minor effects on milk composition, and differences between ORG farms and CON farms may be explained by differences in concentrate intake and concentrate FA concentrations. Milk produced on ORG farms versus CON farms and milk produced during the outdoor versus indoor feeding periods had potential health benefits due to FA composition. In contrast, the higher milk-fat proportions of saturated FA in milk from ORG farms may be perceived as negative for human health

Ruminal acidosis and the rapid onset of ruminal parakeratosis in a mature dairy cow: a case report

A mature dairy cow was transitioned from a high forage (100% forage) to a high-grain (79% grain) diet over seven days. Continuous ruminal pH recordings were utilized to diagnose the severity of ruminal acidosis. Additionally, blood and rumen papillae biopsies were collected to describe the structural and functional adaptations of the rumen epithelium. On the final day of the grain challenge, the daily mean ruminal pH was 5.41 ± 0.09 with a minimum of 4.89 and a maximum of 6.31. Ruminal pH was under 5.0 for 130 minutes (2.17 hours) which is characterized as the acute form of ruminal acidosis in cattle. The grain challenge increased blood beta-hydroxybutyrate by 1.8 times and rumen papillae mRNA expression of 3-hydroxy-3-methylglutaryl-coenzyme A synthase by 1.6 times. Ultrastructural and histological adaptations of the rumen epithelium were imaged by scanning electron and light microscopy. Rumen papillae from the high grain diet displayed extensive sloughing of the stratum corneum and compromised cell adhesion as large gaps were apparent between cells throughout the strata. This case report represents a rare documentation of how the rumen epithelium alters its function and structure during the initial stage of acute acidosis

Fishmeal supplementation during ovine pregnancy and lactation protects against maternal stress-induced programming of the offspring immune system

Background: Prenatally stressed offspring exhibit increased susceptibility to inflammatory disorders due to in utero programming. Research into the effects of n-3 PUFAs shows promising results for the treatment and prevention of these disorders. The purpose of this study was to investigate whether maternal fishmeal supplementation during pregnancy and lactation protects against programming of the offspring\u27s immune response following simulated maternal infection. Methods: In order to accomplish this, 53 ewes were fed a diet supplemented with fishmeal (FM; rich in n-3 PUFA) or soybean meal (SM; rich in n-6 PUFAs) from day 100 of gestation (gd 100) through lactation. On gd135, half the ewes from each dietary group were challenged with either 1.2 μg/kg Escherichia coli lipopolysaccharide (LPS) endotoxin to simulate a bacterial infection, or saline as the control. At 4.5 months of age the offspring\u27s dermal immune response was assessed by cutaneous hypersensitivity testing with ovalbumin (OVA) and candida albicans (CAA) 21 days after sensitization. Skinfold measurements were taken and serum blood samples were also collected to assess the primary and secondary antibody immune response. Results: Offspring born to SM + LPS mothers had a significantly greater change in skinfold thickness in response to both antigens as well as a greater secondary antibody response to OVA compared to all treatments. Conclusions: Supplementation during pregnancy with FM appears to protect against adverse fetal programming that may occur during maternal infection and this may reduce the risk of atopic disease later in life

The effect of supplementing pony diets with yeast on 1. In vivo and in vitro digestibility, faecal pH and particle size

Fibre is essential to maintain healthy gut; however, energy demands of performance horses can be too high to be met by forages alone. Yeast may support the function of cellulolytic bacteria to digest fibre. The aim of this work was to determine the effect of an oral supplement (VistaEQ) containing 4% live yeast on the in vitro and in vivo digestibility of high-starch (HS) and high-fibre diets (HF). Eight ponies were used in a 4 × 4 Latin square design consisting of 4- × 19-day periods and four diets: HF, HF + yeast (HFY), HS and HS + yeast (HSY). In vivo apparent digestibility (AD) was estimated using total collection technique, and faecal particle size was measured using NASCO digestive analyser. Faeces from the ponies were subsequently used as an inoculum in ANKOM RF gas production system to assess fermentation kinetics in vitro. Each module contained 1 g of feed substrate DM in the following combinations: 50% grass hay and 50% alfalfa (HF_50 : 50) or concentrate (HS_50 : 50), and 75% grass hay and 25% alfalfa (HF_75 : 25) or concentrate (HS_75 : 25) with or without yeast. Yeast was able to induce more gas production from HF_75 : 25, HS_75 : 25 and HF_50 : 50 feed substrates incubated with respective faecal inoculum base. Yeast did not affect pH in vitro when the substrates were incubated in 50 : 50 ratio, while the pH was higher for HF_75 : 25 incubated with correspondent faecal inoculum compared to HS_75 : 25 and HSY_75 : 25. Yeast had no effects on ADF and CP AD of either diet. Yeast addition increased DM (HF: 0.2%, HS: 0.4%), organic matter (HF: 0.7%, HS: 1.3%), NDF (HF: 0.5%, HS: 1.5%), total detergent fibre (HF: 0.7%; HS: 0.4%) (P < 0.05) and also tended to increase hemicellulose AD (HF: 0.9%, HS: 1.2%) (P < 0.10). Faecal pH in vivo was higher for both HF diets compared to HS diet without yeast supplementation (P < 0.001, HF and HFY: 6.8; HS: 6.6, HSY: 6.7). However, no difference was observed in faecal pH when HSY was compared to both HF diets. Yeast had no effect on the size of the faecal particles (P > 0.05). Yeast increased in vitro gas production, suggesting more energy could be extracted from the feed, and the in vivo AD of some of the nutrients when HF and HS diets were fed

Changes in the rumen papillae during the periparturient transition in Holstein dairy cows are accompanied by changes in abundance of proteins involved in intracellular pH regulation, but not SCFA transport

The objective of this study was to examine changes in SCFA transportcapacity in the rumen epithelium during the parturition transition period.Twelve pregnant, cannulated primiparous and multiparous cows were fed astandard Total Mixed Ration (TMR) for the duration of the dry period; aftercalving, all cows were switched to an early lactation TMR. Rumen pH, fluid andbiopsies were taken 3 weeks before anticipated calving (PRE), 1 week afteractual calving (PERI) and 6 weeks after calving (POST). Rumen biopsies wereanalyzed for transport protein abundanceusing immunofluorescence. Immunofluorescence analysis showed no significantchanges in the abundance of monocarboxylate co-transporter, isoform 1 among thePRE, PERI and POST periods (16878±1555 A.U., 15613±1508 A.U. and 16886±1555A.U. respectively; MCT1). Also, sodium/proton exchanger, isoform 3 (NHE3) wasnot significantly different among the PRE, PERI and POST periods (10467±1066A.U., 9465±1066 A.U., 8552±1109 A.U., respectively). Sodium/Bicarbonate Co-transporter,isoform 1 (NBC1) was likewise unaffected by time, with the protein abundanceamong PRE, PERI and POST parturitionperiods changing from 16467±1274 A.U., 13983±1318 A.U. and 15047±1324 A.U.,respectively. Abundance of Carbonic Anhydrase, isoform 2 (CA2) decreased from12332±1580 A.U (PRE) to 7235±1580 (PERI) and 8121±1643 (POST) and this decreasewas significant (P = 0.01 PRE v. PERI). The observed changes in proteinabundance suggest that long-term adaptation of the rumen epithelium occurs toincrease transport capacity. Decreased CA2 abundance suggests thatintracellular acidification is occurring as part of epithelial remodelling.Taken together, this implies that, during the periparturient transition, adecrease in rumen pH leads to a decrease in intracellular pH in the rumenepithelium, promoting epithelial remodelling that result in increased SCFAtransport capacity

A characterization of inflammatory and structural markers within the rumen epithelium during grain-induced ruminal acidosis in lactating dairy cattle

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 grain-induced 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

Butyrate-mediated genomic changes involved in the non-specific host defenses, matrix remodelling and the immune response in the rumen epithelium of cows afflicted with subacute ruminal acidosis

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 ?g 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 ?M, 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-PCR, 9 (LCN2, MMP1, MUC16, GPX2, CSTA, FUT1, SERPINE2, BCAM, RAC3) were upregulated, 20 (MTOR, AKIRIN2, NFKBIZ, NFKB2, ACVR2A, LAMB1, FRS2, PPARD, LBP, NEDD4L, SGK1, DEDD2, MAP3K8, PARD6B, PLIN2, ADA, HPGD, FMO5, BMP6, TCHH) were downregulated and 20 were unchanged due to butyrate administration in the proximal gastrointestinal tract. These results demonstrate the potential protective effect and molecular mechanisms involved in a novel butyrate treatment for inflammatory gastrointestinal conditions