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The effects of induced subacute ruminal acidosis (SARA) using grain pellet-based (GPI) and alfalfa pellet-based diet models on systemic immunological parameters were evaluated in nonlactating Holstein cows. The systemic immunological parameters analysed in this study included rectal temperature, blood cell leukogram, expression of lipopolysaccharide (LPS) recognition receptors on leukocytic cells, and plasma and serum proteins. Also, blood biochemistry was analysed. There were no significant differences in rectal temperature, blood cell leukogram, expression of LPS recognition receptors and fibrinogen or haptoglobin concentrations between control and SARA induction treatments. Concentrations of serum amyloid A and lipopolysaccharide-binding protein increased while total protein concentrations decreased in response to GPI SARA compared to control. Blood glucose and urea concentrations increased and decreased, respectively, with GPI SARA treatment. Grain pellet-induced SARA resulted in changes to serum proteins and acute phase proteins but did not affect other systemic immunological parameters suggesting a localized inflammatory response was initiated.

The effects of induced subacute ruminal acidosis (SARA) using grain pellet-based (GPI) and alfalfa pellet-based diet models on systemic immunological parameters were evaluated in nonlactating Holstein cows. The systemic immunological parameters analysed in this study included rectal temperature, blood cell leukogram, expression of lipopolysaccharide (LPS) recognition receptors on leukocytic cells, and plasma and serum proteins. Also, blood biochemistry was analysed. There were no significant differences in rectal temperature, blood cell leukogram, expression of LPS recognition receptors and fibrinogen or haptoglobin concentrations between control and SARA induction treatments. Concentrations of serum amyloid A and lipopolysaccharide-binding protein increased while total protein concentrations decreased in response to GPI SARA compared to control. Blood glucose and urea concentrations increased and decreased, respectively, with GPI SARA treatment. Grain pellet-induced SARA resulted in changes to serum proteins and acute phase proteins but did not affect other systemic immunological parameters suggesting a localized inflammatory response was initiated.

The goal of this research was to evaluate the effects of calf starter fermentation on rumen pH, metabolic adaptation of ruminal epithelia and growth of calves during the weaning transition. In study 1, calf starter consumption increased short chain fatty acid concentration in the rumen and changed expression of genes involved in ketogenesis and intracellular pH regulation but did not affect rumen pH. In study 2, decreasing dietary starch content did not increase rumen pH. However, feeding a calf starter that had the highest in situ dry matter disappearance lowered rumen pH without adversely affecting feed intake and growth of calves. These findings suggest that rumen epithelium can metabolically adapt to increased fermentation in the rumen at molecular level, and that sub-acute rumen acidosis may not adversely affect feed intake and productivity of dairy calves during the weaning transition. / Animal Science

L'acidose ruminale latente (ou acidose sub-clinique) est une préoccupation majeure pour la nutrition des ruminants à haut potentiel de production. Cet état se caractérise par une instabilité du microbiote et des fermentations ruminales qui s’orientent variablement vers le propionate et/ou le butyrate. L’une des stratégies de prévention de l’acidose latente consiste à distribuer dans l’alimentation des ruminants des probiotiques capables de rééquilibrer le microbiote et les fermentations ruminales (dans un sens favorable pour l’animal). L’analyse de la bibliographie montre toutefois que l’effet des probiotiques, et plus particulièrement des bactéries probiotiques (BP), est variable et parfois contradictoire ce qui serait probablement lié à l’instabilité du microbiote. Afin d’étudier la possibilité de prévenir l’acidose latente par les bactéries propioniques et/ou lactiques, nous avons émis l’hypothèse que leur efficacité dépend des orientations fermentaires dans le rumen. Des acidoses latentes butyrique et propionique caractérisées par des profils fermentaires et microbiens distincts ont été développées chez le mouton non productif et la vache laitière pour étudier l’effet et le mode d’action de la bactérie propionique P63 seule ou associée aux lactobacilles Lb. plantarum ou Lb. rhamnosus (P63, Lp + P63 et Lr + P63) sur le fonctionnement de l’écosystème ruminal et les performances animales. Chez le mouton en situation d’acidose propionique, les BP utilisées ont amélioré le pH ruminal via une réduction de la proportion en lactobacilles. Chez la vache laitière, la stabilisation du pH a été associée à une moindre disponibilité en hydrogène susceptible d’être transformé en protons, suite à une augmentation de la propionogenèse et/ou de la densité bactérienne, deux voies consommatrices d’hydrogène. Au cours de l’acidose latente butyrique, l’amélioration du pH n’a été observée que chez les moutons supplémentés avec Lp + P63. Cet effet semblait être dû à une diminution des acides gras volatils et de la proportion en S. bovis mais aussi à un pH initial faible (pH < 5,5) probablement optimal pour l’action des BP ; ce qui n’était pas le cas chez les vaches pour lesquelles le pH initial était compris entre 5,9 et 6,1. En revanche, l’efficacité digestive a été augmentée par l’association de P63 aux lactobacilles chez la vache laitière. L’association Lp + P63 a augmenté les activités fibrolytiques (cellulase, xylanase) et la digestibilité de la matière organique, tandis que Lr + P63 a amélioré la digestion des fibres et a diminué la production de méthane de 25%. Nous n’avons pas observé d’effet sur les performances zootechniques, ce qui serait probablement dû au dispositif expérimental en carré Latin qui n’est peut-être pas optimal pour mettre en évidence l’effet des BP. Nos résultats sont les premiers à démontrer l’efficacité des bactéries probiotiques pour sécuriser et/ou améliorer la digestion des rations et réduire la production de méthane chez le ruminant en acidose, et l’association de P63 avec les souches de Lactobacillus sont les plus efficaces. Enfin, nous avons validé notre hypothèse selon laquelle l’effet et le mode d’action des bactéries probiotiques pour prévenir l’acidose dépendent des orientations fermentaires dans le rumen. / Subacute ruminal acidosis (SARA) is a major concern for the nutrition of high-producing ruminants. This digestive disorder is characterized by the instability of the microbial ecosystem and fermentations which are oriented towards propionate and/or butyrate at the expense of acetate (propionic or butyric SARA). Among the strategies used to prevent SARA, supplementation with direct-fed microbials (DFMs) is thought to be able to balance the ruminal microbiota and fermentation. The analysis of the literature shows that the effect of DFMs, especially bacterial ones, is variable and sometimes contradictory which is probably related to the instability of the microbiota. To investigate the possibility of preventing SARA by propionibacteria and/or lactobacilli based DFMs, we hypothesized that their effectiveness depends on the ruminal fermentation patterns. Butyric and propionic SARA, characterized by distinct microbial and fermentation profiles, have been developed in non-productive sheep and lactating dairy cows to investigate the effects and mode of action of the Propionibacterium P63 alone or in conjunction with the lactobacilli strains Lb. plantarum or Lb. rhamnosus (P63, P63 and Lp + Lr + P63) on the ruminal ecosystem and animal performances. During the propionic SARA induced in sheep, the DFMs used increased the ruminal pH with a concomitant reduction in the lactobacilli population. In dairy cows, the pH stabilization was associated with a lower availability of hydrogen capable of being transformed into protons, following a stimulation of propionogenesis and/or bacterial growth that consume hydrogen. During butyric SARA, improvement in pH was observed only in sheep supplemented with Lp + P63. This effect appeared to be due to a decrease in VFA production and S. bovis proportion. Moreover, the lower initial pH (pH <5.5) was probably optimal for DFMs action, which was not the case for the dairy cows for which the initial pH was between 5.9 and 6.1. For the dairy cows, diet digestion was improved when P63 and lactobacilli association were fed. Indeed, Lp + P63 increased the fibrolytic activities (cellulase, xylanase) and digestibility of organic matter, while Lr + P63 improved fiber digestion and decreased methane production by 25%. We did not observe any effect on animal performances, which was probably due to the Latin square design that is not the best to evaluate the DFMs effects on animal performances. Our results are the first to demonstrate the effectiveness of bacterial DFMs to secure and/or improve diet digestion and reduce methane production in ruminants. Moreover, it seems that the association of P63 with the lactobacilli strains is more effective. Finally, we validated our hypothesis that the effect and mode of action of bacterial DFMs to prevent SARA is conditioned by ruminal fermentation patterns.

This work helps to determine the extent of immune system involvement in the adaptive response to subacute ruminal acidosis (SARA) in three parts. The first (Chapter 2) uses non-lactating cows to study specific changes in inflammatory protein expression in which SARA is created. The second (Chapter 3), uses the same model as Chapter 2. However, in this case, lactating cows are used to help establish the time course for adaptation to acidosis. The third part (Chapter 4) delineates the genomic changes that occur in the rumen epithelium when a therapeutic intervention is introduced using exogenous supplemental butyrate. In the first experiment, the expression of the extracellular matrix (ECM) proteins type IV collagen and laminin β1 decreased, and the monocarboxylate transporter MCT1, increased during the acidotic challenge. Nuclear factor of activated T-cells, NFATc2, and tumour necrosis factor alpha (TNF-α) decreased while interleukin-1 beta (IL-1β) increased during the experimental treatment period. Chapter 3 measured lipopolysaccharide (LPS) and its carrier, LPS binding protein, LBP, which were found to be elevated due to SARA. Moreover, NFATc2 was reduced during this period. Exogenous butyrate resulted in increased plasma LBP, plasma beta hydroxyl butyrate (BHBA), and ruminal butyrate. Milk parameters (total protein and fat) were unaffected by treatment, as were rumen LPS, acetate, valerate, isovalerate, and isobutyrate. Moreover, exogenous butyrate increased gene transcription of genes involved in non-specific host defences (NHSD) such as mucin, and remodelling (RM), such as matrix metallopeptidase 16 (MMP16), and decreased the transcription of genes of the immune response (IR), such as nuclear factor kappa B2 (NFκB2). Together, these three experiments have demonstrated that although wound healing is mediated by the immune system in more severe models of epithelial damage, our model of SARA did not involve full-thickness, penetrating lesions and hence did not involve the systemic immune system to such a degree than was previously thought. In addition, we were able to demonstrate that the addition of butyrate to this model of grain-induced acidosis was beneficial, as it decreased the local inflammatory response and helped the epithelium adapt to its harsher environment. / 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).

Os aditivos alimentares monensina e óleos funcionais foram avaliados em dietas com elevada proporção de concentrado fornecida de forma abrupta a 12 novilhos canulados no rúmen. Foi utilizado delineamento de blocos ao acaso com medidas repetidas no tempo em dois períodos experimentais de 21 dias, com no mínimo seis semanas para readaptação dos animais à dieta volumosa (feno de Tifton). A dieta basal composta por 92,25% de concentrado (82,41% de milho quebrado, 6,78% de farelo de soja, 7,75% de feno de Tifton picado, 1,77% núcleo mineral e 1,29% ureia) foi fornecida no dia 1 de cada período experimental. Os animais receberam um dos aditivos alimentares, como seguem: sem aditivos (CTR), 400 mg de óleos funcionais de mamona e líquido da casca de caju/kg de MS ingerida (OF), 30 mg de monensina/kg de MS ingerida (M30) e 40 mg de monensina/kg de MS ingerida (M40). As variáveis ruminais e sanguíneas, o comportamento ingestivo e os microrganismos ruminais foram avaliados. Cada novilho foi considerado uma unidade experimental. Os dados foram analisados com o Proc Mixed, tendo o tempo após o fornecimento da alimentação como medidas repetidas. Animais alimentados com M40 reduziram a concentração total de ácidos graxos de cadeia curta (P = 0,017), a concentração de lactato (P = 0,0012) e osmolaridade ruminal (P = 0,04). Houve interação entre tratamento e dias após transição abrupta sobre a ingestão de matéria seca expressa em kg/dia (P = 0,008) e peso corporal (P = 0,045), bem como para o pH médio do rúmen (P = 0,04), a proporção molar de propionato (P = 0,034) e a proporção molar de valerato (P = 0,031). O tratamento M30 apresentou a menor relação acetato:propionato (P = 0,03). Os tratamentos não alteraram o comportamento ingestivo (P &ge; 0,05) ou as atividades comportamentais (P &ge; 0,05), bem como a expressão relativa de F. Succinogenes (P = 0,465), S. bovis (P = 0,781) e M. elsdenii (P = 0,972). O tratamento CTR apresentou maior propensão à ocorrência de desbalanço no sistema ácido-básico do sangue. Porém, o volume globular sanguíneo, o pH e a osmolaridade do sangue não foram alteradas pelos tratamentos (P &ge; 0,05). Os aditivos alimentares utilizados em dietas com elevada proporção de concentrado fornecidas de forma abrupta agiram sob formas distintas na redução da acidose subclínica. De forma geral, a inclusão de OF e M40 não resultou em melhoria expressiva no ambiente ruminal diante da situação desafiadora da dieta, especialmente na primeira semana, quando o tratamento M30 apresentou melhor capacidade de estabilizar a fermentação ruminal. / Monensin and functional oils were evaluated in high-concentrate diet abruptly fed to 12 ruminally canullated steers. A randomized complete block design with repeated measures over time within two experimental periods of 21 days each was used, with at least six weeks for readaptation of steers to forage diet. In the high-concentrate basal diet (92.25% of concentrate) the follow treatments were added: no additives (CTR); 400 mg of castor oil and cashew nut shell liquid/kg of DMI (FO); 30 mg monensin/kg of DMI (M30) and 40 mg monensin/kg of DMI (M40). The ruminal variables, blood metabolites, feeding behaviour and microbial variable were determined. Each steer was analysed as an experimental unit. Data were analysed by Proc Mixed with time after feeding used as repeated measures.Treatment M40 showed lower ruminal total short chain fatty acids (P = 0.017), lactate concentration (P = 0.0012) and osmolality (P = 0.04). The dry matter intake expressed by kg/day (P = 0.008) and porcenteage of body weight (P = 0.045), as well as mean rumen pH (P = 0.04), propionate (P = 0.034) and valerate (P = 0.031) molar proportion had significative interaction between treatment and day. The treatment M30 showed lower acetate:propionate ratio (P = 0.03). Treatments did not change the feed behaviour (P &ge; 0.05), behavioural activities (P &ge; 0.05), and relative expression of Fibrobacter succinogenes (P = 0.465), Streptococcus bovis (P = 0.781) and Megasphaera elsdenii (P = 0.972). The blood packed volume cell, osmolality and pH were unaffected by treatments (P &ge; 0.05), but high propensity to systemic acid-base imbalance were observed in CTR diet. Feed additives had different effects to reduce the subacute acidosis. The use of FO and M40 did not change most of the rumen fermentation variables, especially in the first week after abrupt transition, where M30 provided higher protection against acidosis.

Feeding diets rich in rapidly fermentable non-structural carbohydrates can lead to the development of ruminal acidosis. This study was conducted to determine if the duration of time that cattle are fed a high-grain diet affects their absorption of short-chain fatty acids (SCFA) and susceptibility to, and recovery from, ruminal acidosis. Sixteen Angus heifers (BW ± SEM, 261 ± 6.1 kg) were assigned to 1 of 4 blocks, and fed a backgrounding diet consisting of 60% barley silage, 30% barley grain, and 10% supplement (DM basis). Within block, cattle were randomly assigned to 1 of 2 treatments differing in the number of days they were fed the high-grain diet prior to an acidosis challenge: 34 d for long-adapted (LA) and 8 d for short-adapted (SA). All cattle were exposed to the same 20-d dietary transition using 5 dietary steps until achieving the final diet that contained 9% barley silage, 81% barley grain, and 10% supplement (DM basis). Data were collected during an 8-d baseline period (BASE), on the d of the acidosis challenge (CHAL), and during two consecutive 8 d recovery periods (REC1 and REC2). Ruminal acidosis was induced by restricting feed to 50% of DMI:BW for 24 h followed by an intraruminal infusion of ground barley at 10% DMI:BW. Cows were then given their regular diet allocation 1 h after the intraruminal infusion. The duration of time fed the high-grain diet did not affect ruminal pH, lactate, or SCFA concentrations (P > 0.050). However, during BASE and on the day of CHAL the SA heifers experienced greater linear (P = 0.031), quadratic (P = 0.016), and cubic (P = 0.008) between day change in the duration of time that pH was < 5.5 than LA heifers. Relative to BASE, inducing acidosis increased daily duration (531 to 1020 min/d; P < 0.001) and area (176 to 595 (min × pH)/d; P < 0.001) that pH was < 5.5. Inducing ruminal acidosis also increased the daily mean (0.3 to 11.4 mM; P = 0.013) and maximum (1.3 to 29.3 mM; P = 0.008) rumen fluid lactate concentrations relative to BASE, suggesting that an acute bout of ruminal acidosis was induced. In addition, a treatment × day interaction for the duration that pH was < 5.5 during REC1 suggests that LA cattle tended to recover from the CHAL more rapidly than SA cattle (P = 0.085). Indeed, analysis of covariance confirmed that the LA heifers experienced a quicker linear (P = 0.019) recovery over time from CHAL. The greater rate of recovery possibly resulted from the LA heifers having greater rates of both fractional butyrate (45 vs. 36 %/h; P = 0.019) and propionate absorption (42 vs. 34 %/h; P = 0.045), and tending to have greater rates, on an absolute basis, of butyrate absorption (94 vs. 79 mmol/h; P = 0.087) iii and, on a fractional basis, of total SCFA absorption (37 vs. 32 %/h; P = 0.100). Treatment × period interactions revealed that LA heifers had greater serum D-lactate concentrations (P = 0.003), and fractional rates of lactate absorption (P = 0.024) than SA heifers, during CHAL and REC1, respectively. When treatments were pooled, the absorption (%/h and mmol/h) of acetate, propionate, butyrate, and total SCFA increased between REC1 and REC2, with intermediate values for BASE (P ≤ 0.05). Corresponding to a reduction in absorption during REC1 (2 d post CHAL), saliva production (kg/h; P = 0.018) increased between BASE and REC1, with intermediate values for REC2. These results indicate that the duration of time cattle are fed a high-grain diet may stabilize rumen pH, both prior to and after an induced bout of acute ruminal acidosis, likely through increased ruminal absorptive capacity for SCFA and lactate. In addition, this study found evidence to suggest that beef cattle possess the ability to increase saliva secretion in order to compensate for decreased absorptive capacity.

The objective of the first study was to quantify the effects of feeding Schizochytrium sp. microalgae (SP-1, Alltech, Inc., Nicholasville, KY) on milk fat and DHA content. Eight cows were fed: 0, 100, 300, or 600 g of algae per day. Fat percentage was greater (P < 0.05) for cows on treatments 0 g and 100 g than for cows on treatments 300 g and 600 g (P < 0.05). Docosahexaenoic acid in milk was greater for cows on treatment 300 and 600 than for cows on treatment 0 and 100 (P < 0.05). The objective of the second study was to assess yeast supplementation effects on high and low forage dairy cow diets. Four cows were assigned to 1 of 4 treatments: 1) low forage (LF), 2) low forage with 10 g/d yeast (Yea-Sacc®; Alltech Inc., Nicholasville, KY; LFY), 3) high forage (HF), or 4) high forage with 10 g/d yeast (HFY). Only rumination time and DMI were influenced by treatment (P < 0.01). Dry matter intake was 17.05, 13.41, 19.44, and 20.29 ± 1.40 kg/d and rumination time was 442.88, 323.09, 433.34, and 475.50 ± 21.93 min/d for cows on the LF, LFY, HF, and HFY treatments, respectively.

Os aditivos alimentares monensina e óleos funcionais foram avaliados em dietas com elevada proporção de concentrado fornecida de forma abrupta a 12 novilhos canulados no rúmen. Foi utilizado delineamento de blocos ao acaso com medidas repetidas no tempo em dois períodos experimentais de 21 dias, com no mínimo seis semanas para readaptação dos animais à dieta volumosa (feno de Tifton). A dieta basal composta por 92,25% de concentrado (82,41% de milho quebrado, 6,78% de farelo de soja, 7,75% de feno de Tifton picado, 1,77% núcleo mineral e 1,29% ureia) foi fornecida no dia 1 de cada período experimental. Os animais receberam um dos aditivos alimentares, como seguem: sem aditivos (CTR), 400 mg de óleos funcionais de mamona e líquido da casca de caju/kg de MS ingerida (OF), 30 mg de monensina/kg de MS ingerida (M30) e 40 mg de monensina/kg de MS ingerida (M40). As variáveis ruminais e sanguíneas, o comportamento ingestivo e os microrganismos ruminais foram avaliados. Cada novilho foi considerado uma unidade experimental. Os dados foram analisados com o Proc Mixed, tendo o tempo após o fornecimento da alimentação como medidas repetidas. Animais alimentados com M40 reduziram a concentração total de ácidos graxos de cadeia curta (P = 0,017), a concentração de lactato (P = 0,0012) e osmolaridade ruminal (P = 0,04). Houve interação entre tratamento e dias após transição abrupta sobre a ingestão de matéria seca expressa em kg/dia (P = 0,008) e peso corporal (P = 0,045), bem como para o pH médio do rúmen (P = 0,04), a proporção molar de propionato (P = 0,034) e a proporção molar de valerato (P = 0,031). O tratamento M30 apresentou a menor relação acetato:propionato (P = 0,03). Os tratamentos não alteraram o comportamento ingestivo (P &ge; 0,05) ou as atividades comportamentais (P &ge; 0,05), bem como a expressão relativa de F. Succinogenes (P = 0,465), S. bovis (P = 0,781) e M. elsdenii (P = 0,972). O tratamento CTR apresentou maior propensão à ocorrência de desbalanço no sistema ácido-básico do sangue. Porém, o volume globular sanguíneo, o pH e a osmolaridade do sangue não foram alteradas pelos tratamentos (P &ge; 0,05). Os aditivos alimentares utilizados em dietas com elevada proporção de concentrado fornecidas de forma abrupta agiram sob formas distintas na redução da acidose subclínica. De forma geral, a inclusão de OF e M40 não resultou em melhoria expressiva no ambiente ruminal diante da situação desafiadora da dieta, especialmente na primeira semana, quando o tratamento M30 apresentou melhor capacidade de estabilizar a fermentação ruminal. / Monensin and functional oils were evaluated in high-concentrate diet abruptly fed to 12 ruminally canullated steers. A randomized complete block design with repeated measures over time within two experimental periods of 21 days each was used, with at least six weeks for readaptation of steers to forage diet. In the high-concentrate basal diet (92.25% of concentrate) the follow treatments were added: no additives (CTR); 400 mg of castor oil and cashew nut shell liquid/kg of DMI (FO); 30 mg monensin/kg of DMI (M30) and 40 mg monensin/kg of DMI (M40). The ruminal variables, blood metabolites, feeding behaviour and microbial variable were determined. Each steer was analysed as an experimental unit. Data were analysed by Proc Mixed with time after feeding used as repeated measures.Treatment M40 showed lower ruminal total short chain fatty acids (P = 0.017), lactate concentration (P = 0.0012) and osmolality (P = 0.04). The dry matter intake expressed by kg/day (P = 0.008) and porcenteage of body weight (P = 0.045), as well as mean rumen pH (P = 0.04), propionate (P = 0.034) and valerate (P = 0.031) molar proportion had significative interaction between treatment and day. The treatment M30 showed lower acetate:propionate ratio (P = 0.03). Treatments did not change the feed behaviour (P &ge; 0.05), behavioural activities (P &ge; 0.05), and relative expression of Fibrobacter succinogenes (P = 0.465), Streptococcus bovis (P = 0.781) and Megasphaera elsdenii (P = 0.972). The blood packed volume cell, osmolality and pH were unaffected by treatments (P &ge; 0.05), but high propensity to systemic acid-base imbalance were observed in CTR diet. Feed additives had different effects to reduce the subacute acidosis. The use of FO and M40 did not change most of the rumen fermentation variables, especially in the first week after abrupt transition, where M30 provided higher protection against acidosis.