Antiketogenic effects of monensin in early lactation

Effects of monensin supplementation on lactation performance of dairy cows: a systematic review and dose-response meta‑analysis

The aim of this study was to conduct a comprehensive review with meta-analysis to determine the effects of the dose-response relationship between monensin supplementation and dairy cow performance and milk composition. Results from 566 full-text articles and 48 articles with 52 studies were meta-analyzed for pooled estimates. Monensin supplementation up to 23 ppm increased milk production, with the optimal dose being 12.6 ppm. Monensin supplementation at doses ranging from 16 to 96 ppm increased milk production in the prepartum phase (- 28 to 0 day relative to calving). From 60 to 150 DIM, monensin supplementation up to 21 ppm had a significant positive effect on this outcome, while supplementation in the 37 to 96 ppm range caused a decrease in this variable. At 0 to 60 and > 150 DIM, monensin supplementation had no effect on milk yield. At dosages of 22 to 96 ppm, 12 to 36 ppm, and below 58 ppm and 35 ppm, respectively, monensin supplementation resulted in significant decreases in dry matter intake (DMI), milk protein percentage, milk fat percentage, and milk fat yield. Overall, based on the results of this meta-analysis and considering all variables, the recommended optimal dose of monensin could be about 16 ppm.

Digestibility, lactation performance, plasma metabolites, ruminal fermentation, and bacterial communities in Holstein cows fed a fermented corn gluten-wheat bran mixture as a substitute for soybean meal

The purpose of this research was to investigate the effects of replacing soybean meal (SBM) with a fermented corn gluten-wheat bran mixture (FCWM) on nutrient digestibility, lactation performance, plasma metabolites, ruminal fermentation, and bacterial communities in Holstein cows. Nine healthy multiparous (parity = 3) Holstein cows with similar body weights (624 ± 14.4 kg), days in milk (112 ± 4.2), and milk yields (31.8 ± 1.73 kg; all mean ± standard deviation) were used in a replicated 3 × 3 Latin square design with 3 periods of 28 d. Cows were fed 1 of 3 dietary treatments in which FCWM replaced SBM as follows: basal diet with no replacement (0FCWM); 50% replacement of SBM with FCWM (50%FCWM); and 100% replacement of SBM with FCWM (100%FCWM). The diets were formulated to be isocaloric and isonitrogenous. The results showed that the total-tract digestibility of dry matter and crude protein increased linearly with increased dietary FCWM, and we found a trend for increased total-tract neutral detergent fiber and potentially digestible NDF digestibility. Milk yield tended to increase in a linear manner as more FCWM was consumed, and energy-corrected milk production was significantly increased with FCWM supplementation as a result of increased milk protein and lactose yields. Plasma glucose and IgG concentrations increased linearly with increasing FCWM supplementation, but plasma malondialdehyde concentration decreased linearly. Concentrations of total volatile fatty acids and propionate showed a linear increase with increasing FCWM supplementation, leading to a linear decrease in pH. The relative abundance of ruminal Prevotellaceae, Veillonellaceae, and Prevotella 1 increased linearly with increasing FCWM supplementation, and the relative abundance of ruminal Succinivibrionaceae and Muribaculaceae decreased linearly. The relative abundance of fecal Ruminococcaceae, Prevotellaceae, and Ruminococcaceae UCG-005 increased linearly with increasing FCWM supplementation, but the relative abundance of fecal Peptostreptococcaceae decreased linearly. Overall, the replacement of SBM with FCWM altered the composition of the ruminal bacterial community and improved nutrient digestibility, lactation performance, and ruminal fermentation in cows, providing a data reference for the use of FCWM in dairy production.

Effects of prepartum diets varying in dietary energy density and monensin on early-lactation performance in dairy cows

Our objectives were to evaluate the effects of prepartum monensin supplementation and dry-period nutritional strategy on the postpartum productive performance of cows fed monensin during lactation. A total of 102 Holstein cows were enrolled in the experiment (32 primiparous and 70 multiparous). The study was a completely randomized design, with randomization restricted to balance for parity, body condition score, and expected calving date. A 2 × 2 factorial arrangement of prepartum treatments was used; the variables of interest were prepartum feeding strategy [controlled-energy diet throughout the dry period (CE) vs. controlled-energy diet from dry-off to 22 d before expected parturition, followed by a moderate-energy close-up diet from d 21 before expected parturition through parturition (CU)] and prepartum monensin supplementation [0 g/t (control, CON) or 24.2 g/t (MON); Rumensin; Elanco Animal Health, Greenfield, IN]. Lactation diets before and after the dry period contained monensin at 15.4 g/t. During the close-up period, cows fed CU had greater DM and NE_L intakes than cows fed CE. Calf BW at birth tended to be greater for cows fed CU than for those fed CE but was not affected by MON supplementation. Diet did not affect calving difficulty score, but cows supplemented with MON had an increased calving difficulty score. We found a tendency for a MON × parity interaction for colostral IgG concentration, such that multiparous MON cows tended to have lower IgG concentration than CON cows, but colostral IgG concentration for primiparous MON and CON cows did not differ. Postpartum milk yield did not differ between diets but tended to be greater for cows supplemented with MON. Milk fat and lactose content were greater for cows fed CU than for those fed CE, and lactose content and yield were increased for cows supplemented with MON. Solids-corrected and fat-corrected milk yields were increased by MON supplementation, but were not affected by diet. Overall means for postpartum DMI did not differ by diet or MON supplementation. The CU diet decreased the concentration of nonesterified fatty acids during the close-up period but increased it postpartum. Neither diet nor monensin affected β-hydroxybutyrate or liver composition. Overall, postpartum productive performance differed little between prepartum dietary strategies, but cows fed MON had greater energy-corrected milk production. In herds fed monensin during lactation, monensin should also be fed during the dry period.

Impacts of feeding monensin sodium on production and the efficiency of milk production in dairy cows fed total mixed rations: evaluation of a confounded literature

The amount of milk Canadian dairy farmers produce is limited to a production quota expressed in milk fat. Because milk economic value is primarily based on fat and protein, it can be advantageous to decrease the milk fat to protein ratio. Monensin sodium has been suggested to reduce milk fat proportion and outputs, but not milk protein. Publications using lactating dairy cows were utilized to assess predictability of production responses to monensin feeding based upon their base production characteristics and diet composition. Predicted animal output changes due to monensin had poor fits with low r2 (0.31–0.44) and unevenly distributed residuals. Further assessment revealed that cow characteristics, and diets, were not independent of monensin feeding level. Thus, the 43 comparisons were clustered into levels of 10–12, 14–18, or 20–24 mg kg−1 of diet dry matter (DM). Milk fat yield reductions due to monensin differed (P < 0.05; 10–12 and 14–18 mg kg−1 DM), or tended to differ (P = 0.057; 20–24 mg kg−1 DM), from zero (i.e., no change). Monensin addition to total mixed rations of lactating dairy cows negatively impacted milk fat yield to a greater extent than milk protein.

Dosage-dependent effects of monensin on the rumen microbiota of lactating dairy cattle

We examined the dose-dependent effects of feeding lactating dairy cows a standard diet supplemented with monensin at 175, 368, or 518 mg cow^-1 day^-1 on the rumen microbiota. For each dosage, 3 animals were randomly assigned into groups and fed the same basal total mixed ration diet supplemented with monensin, at the respective dose. After 20 days, rumen samples were taken and the effect on the microbiota was examined by 16S rRNA gene sequence analysis and qPCR. At the lowest dose no significant change in 16S rRNA gene sequences associated with any bacterial phyla was observed; however, at the medium and high dosages, we observed significant reductions in sequences associated with gram-positive bacteria and significant increases in those associated with gram-negative bacteria that were dosage dependent. All dosages reduced the levels of sequences associated with methanogenic archaea in the rumen, with the medium dosage showing the largest decline. No significant difference was observed for the 18S rRNA gene sequences associated with protozoa in any of the libraries. Our results indicate that with this diet the medium dosage of monensin was most efficacious for the reduction in methanogenic archaea in the rumen of lactating dairy.

A 100-Year Review: Metabolic modifiers in dairy cattle nutrition

The first issue of the Journal of Dairy Science in 1917 opened with the text of the speech by Raymond A. Pearson, president of the Iowa State College of Agriculture, at the dedication of the new dairy building at the University of Nebraska (J. Dairy Sci. 1:4-18, 1917). Fittingly, this was the birth of a new research facility and more importantly, the beginning of a new journal devoted to the sciences of milk production and manufacture of products from milk. Metabolic modifiers of dairy cow metabolism enhance, change, or interfere with normal metabolic processes in the ruminant digestive tract or alter postabsorption partitioning of nutrients among body tissues. Papers on metabolic modifiers became more frequent in the journal around 1950. Dairy farming changed radically between 1955 and 1965. Changes in housing and feeding moved more cows outside, and cows and heifers in all stages of lactation, including the dry period, were fed as a single group. Rations became wetter with the shift to corn silage as the major forage in many rations. Liberal grain feeding met the requirements of high-producing cows and increased production per cow but introduced new challenges; for example, managing and feeding cows as a group. These changes led to the introduction of new strategies that identified and expanded the use of metabolic modifiers. Research was directed at characterizing the new problems for the dairy cow created by group feeding. Metabolic modifiers went beyond feeding the cow and included environmental and housing factors and additives to reduce the incidence and severity of many new conditions and pathologies. New collaborations began among dairy cattle specialties that broadened our understanding of the workings of the cow. The Journal of Dairy Science then and now plays an enormously important role in dissemination of the findings of dairy scientists worldwide that address existing and new technologies.

Economic Synergy between Dry Cow Diet Improvement and Monensin Bolus Use to Prevent Subclinical Ketosis: An Experimental Demonstration Based on Available Literature

The prevention of subclinical ketosis (SCK) is based on maintaining adequate nutrition in dairy cows during the dry period and close to calving. Recently, an oral-route monensin bolus to prevent SCK was approved in Europe. The present study aims to define the allocation of resources for SCK management at the herd level and evaluate the profitability of administering monensin boluses in cows at risk for SCK. A stochastic model was used to calculate the total cost of SCK for a population with a given prevalence of cows at risk for SCK. This model included the ability of the farmer to correctly target and preventatively treat these cows at risk for SCK. The results clearly demonstrated economic synergy between two management practices. First, reducing the prevalence of cows at risk for SCK dramatically reduces the total cost of SCK and seems profitable in most situations. Second, monensin bolus use to reduce the occurrence of SCK in cows already at risk for SCK is cost-effective. The results also highlighted three economic strategies to manage SCK in the dairy industry in Europe. First, monensin bolus use throughout an entire herd when the prevalence of cows at risk for SCK is high is only profitable in the short-term as a tool to correct acute deterioration at the herd level. Second, decreasing the prevalence of cows at risk for SCK through adequate feeding in the dry period is of financial interest as a baseline strategy when prevalence is high, assuming moderate additional cost linked to the new diet. Third, monensin bolus use when the prevalence of cows at risk for SCK is low is also profitable as a long-term strategy when only cows at high risk for SCK (such as cows that are over-conditioned, old, or have a previous history of SCK-related disorders) are targeted for preventative treatment. Authors suggest to use the present results considering that farmers have a correct, but not perfect, ability to target animals to be preventively targeted with the monensin bolus. Further work is required to facilitate the early identification of cows at risk for SCK.

EFEITO DA MONENSINA SÓDICA SOBRE O PERFIL METABÓLICO DE OVELHAS ANTES E APÓS O PARTO

Resumo O estudo foi realizado com o intuito de avaliar o efeito da monensina, suplementada a partir de 60 dias antes do parto (dap) e por 30 dias pós-parto, sobre o perfil metabólico e hormonal de ovelhas. As ovelhas prenhas (n=13), foram divididas, de forma aleatória, em dois grupos, um que recebeu a monensina (n=7) (30 mg/dia) e o controle (n=6). Amostras de sangue e fluido ruminal foram colhidas aos 60, 50, 40, 30, 20 e 10 dias antes do parto, no momento do parto e nos 10, 20 e 30 dias pós-parto. As variáveis mensuradas foram: glicose, frutosamina, ácidos graxos não esterificados (AGNEs), β-hidroxibutirato, colesterol, triglicérides, proteína total, albumina, ureia e pesquisa de corpos cetônicos na urina. As determinações hormonais foram cortisol e a insulina. No fluido ruminal foi determinado o pH e a concentração dos ácidos graxos voláteis. Na análise estatística foi empregada a ANOVA e estudo de correlação (P<0,05). A monensina elevou (P<0,05) a concentração do propionato no rúmen e frutosamina e insulina no sangue. A administração da monensina promoveu melhora em alguns indicadores do balanço energético.

The effect of diet supplemented with vegetable oils and/or monensin on the vaccenic acid production in continuous culture fermenters

Studies have shown that supplementing ruminant diets with vegetable oils modulated the rumen biohydrogenation and increased polyunsaturated fatty acid in their products. These positive values are often accompanied by a marginal loss of supplemented unsaturated fatty acids and rise in the concentrations of saturated fatty acids. This study were carried out mainly to investigate the effect of supplementing diets with sunflower oil, olive oil with or without monensin on the production and accumulation of vaccenic acid (VA) in continuous culture fermenters as a long term in vitro rumen simulation technique. Eight dual-flow continuous culture fermenters were used in an 8 replication experiment lasted 10 days each (first 7 days for adaptation and last 3 days for samples collection). Supplementing diets with plant oils and monensin in the present experiment increased VA and conjugated linoleic acids (P > 0.05) in ruminal cultures. The results suggest that supplementing diets with both olive oil and sunflower oil and monensin increased VA accumulation compared to plant oils supplemented alone without affecting the rumen dry matter and organic matter digestibility.

Pathophysiological evaluation of subacute ruminal acidosis (SARA) by continuous ruminal pH monitoring

Evaluation of the radio‐transmission pH‐measurement system for monitoring the ruminal pH and subacute ruminal acidosis (SARA) in cattle is described. This is done in order to reveal the possible application of this system for detection and pathophysiological research of SARA by continuous ruminal pH measurement. The possibility of using this system for assessment of the ruminal pH in SARA cattle, and the presence of negative correlation between the ruminal pH and ruminal temperature in heathy and SARA cattle were determined. In addition, the 16S rRNA gene pyrosequencing analysis showed that the ruminal microbial community was simpler in SARA cattle, and the bacterial numbers in SARA cattle were lower than those in healthy hay‐fed cattle. Concentrate feeding might have reduced the diversity of the ruminal microbial community. Changes in the ruminal microbial community of SARA cattle might be related to the changes in ruminal pH followed by the decrease in the number of some bacteria. Continuous monitoring of the ruminal pH using the radio‐transmission pH‐measurement system would be applied for detection and prevention of SARA in the field and pathophysiological research of SARA, including ruminal zymology and bacteriology, which have been determined previously by sampling of the ruminal fluid and measuring of ruminal pH.

Effects of monensin on metabolism and production in dairy saanen goats in periparturient period

This trial evaluated the effects of dietary supplementation with monensin sodium on dry matter intake, metabolic parameters and milk yield and milk composition of dairy Saanen goats in the periparturient period. Twelve Saanen pregnant dairy goats were assigned to a treatment and a control group. Saanen goats were fed monensin as its 10% sodium salt in the amount of 33 mg/kg of total dry matter intake during 30 d before parturition till d 42 in milk. Blood samples were collected from each goat at d 30, 15 and 7 before expected kidding time and also in d 1, 7, 13, 19, 21, 28, 35 and 42 postpartum. The serum concentrations of β-Hydroxybutyrate (BHBA), non-esterifed fatty acid (NEFA), calcium, magnesium, inorganic phosphorus, cholesterol, triglyceride, urea, total protein, albumin and glucose and aspartate aminotransferase (AST) activity were determined. The BHBA concentration significantly decreased in goats, which received monensin in comparison to controls in the postpartum period (p = 0.049). The concentration of sodium (Na) was significantly influenced by monensin treatment in the postpartum period (p = 0.048). In addition, the difference in dry matter intake was highly significant between the two groups during the pre-partum period. Controls had more dry matter intake (DMI) than treatment goats (p = 0.0001). Mean 3.5% fat corrected milk production was not influenced by monensin treatment. However, milk fat percentage was significantly decreased in monensin treated goats (p = 0.0017).

Effect of dietary monensin on the bacterial population structure of dairy cattle colonic contents

To determine the effect of monensin, a carboxylic polyether ionophore antibiotic, on the bacterial population structure of dairy cattle colonic contents, we fed six lactating Holstein cows a diet containing monensin (600 mg day(-1)) or an identical diet without monensin. Fresh waste samples were taken directly from the animals once a month for 3 months and assayed for their bacterial population structure via 16S rRNA gene sequence analysis. In total 6,912 16S rRNA genes were examined, comprising 345 and 315 operational taxonomic units (OTUs) from the monensin fed and control animals, respectively. Coverage estimates of the OTUs identified were 87.6% for the monensin fed and 88.3% for the control colonic content derived library. Despite this high level of coverage, no significant difference was found between the libraries down to the genus level. Thus we concluded that although monensin is believed to increase milk production in dairy cattle by altering the bacterial population structure within the bovine gastrointestinal tract, we were unable to identify any significant difference in the bacterial population structure of the colonic contents of monensin fed vs. the control dairy cattle, down to the genus level.

Interaction of molasses and monensin in alfalfa hay- or corn silage-based diets on rumen fermentation, total tract digestibility, and milk production by Holstein cows

Sugar supplementation can stimulate rumen microbial growth and possibly fiber digestibility; however, excess ruminal carbohydrate availability relative to rumen-degradable protein (RDP) can promote energy spilling by microbes, decrease rumen pH, or depress fiber digestibility. Both RDP supply and rumen pH might be altered by forage source and monensin. Therefore, the objective of this study was to evaluate interactions of a sugar source (molasses) with monensin and 2 forage sources on rumen fermentation, total tract digestibility, and production and fatty acid composition of milk. Seven ruminally cannulated lactating Holstein cows were used in a 5 x 7 incomplete Latin square design with five 28-d periods. Four corn silage diets consisted of 1) control (C), 2) 2.6% molasses (M), 3) 2.6% molasses plus 0.45% urea (MU), or 4) 2.6% molasses plus 0.45% urea plus monensin sodium (Rumensin, at the intermediate dosage from the label, 16 g/909 kg of dry matter; MUR). Three chopped alfalfa hay diets consisted of 1) control (C), 2) 2.6% molasses (M), or 3) 2.6% molasses plus Rumensin (MR). Urea was added to corn silage diets to provide RDP comparable to alfalfa hay diets with no urea. Corn silage C and M diets were balanced to have 16.2% crude protein; and the remaining diets, 17.2% crude protein. Dry matter intake was not affected by treatment, but there was a trend for lower milk production in alfalfa hay diets compared with corn silage diets. Despite increased total volatile fatty acid and acetate concentrations in the rumen, total tract organic matter digestibility was lower for alfalfa hay-fed cows. Rumensin did not affect volatile fatty acid concentrations but decreased milk fat from 3.22 to 2.72% in corn silage diets but less in alfalfa hay diets. Medium-chain milk fatty acids (% of total fat) were lower for alfalfa hay compared with corn silage diets, and short-chain milk fatty acids tended to decrease when Rumensin was added. In whole rumen contents, concentrations of trans-10, cis-12 C(18:2) were increased when cows were fed corn silage diets. Rumensin had no effect on conjugated linoleic acid isomers in either milk or rumen contents but tended to increase the concentration of trans-10 C(18:1) in rumen samples. Molasses with urea increased ruminal NH(3)-N and milk urea N when cows were fed corn silage diets (6.8 vs. 11.3 and 7.6 vs. 12.0 mg/dL for M vs. MU, respectively). Based on ruminal fermentation characteristics and fatty acid isomers in milk, molasses did not appear to promote ruminal acidosis or milk fat depression. However, combinations of Rumensin with corn silage-based diets already containing molasses and with a relatively high nonfiber carbohydrate:forage neutral detergent fiber ratio influenced biohydrogenation characteristics that are indicators of increased risk for milk fat depression.

Effects of monensin and dietary soybean oil on milk fat percentage and milk fatty acid profile in lactating dairy cows

The objective of this study was to investigate the effect of monensin (MN) and dietary soybean oil (SBO) on milk fat percentage and milk fatty acid (FA) profile. The study was conducted as a randomized complete block design with a 2 x 3 factorial treatment arrangement using 72 lactating multiparous Holstein dairy cows (138 +/- 24 d in milk). Treatments were [dry matter (DM) basis] as follows: 1) control total mixed ration (TMR, no MN) with no supplemental SBO; 2) MN-treated TMR (22 g of MN/kg of DM) with no supplemental SBO; 3) control TMR including 1.7% SBO; 4) MN-treated TMR including 1.7% SBO; 5) control TMR including 3.4% SBO; and 6) MN-treated TMR including 3.4% SBO. The TMR (% of DM; corn silage, 31.6%; haylage, 21.2%; hay, 4.2%; high-moisture corn, 18.8%; soy hulls, 3.3%; and protein supplement, 20.9%) was offered ad libitum. The experiment consisted of a 2-wk baseline, a 3-wk adaptation, and a 2-wk collection period. Monensin, SBO, and their interaction linearly reduced milk fat percentage. Cows receiving SBO with no added MN (treatments 3 and 5) had 4.5 and 14.2% decreases in milk fat percentage, respectively. Cows receiving SBO with added MN (treatments 4 and 6) had 16.5 and 35.1% decreases in milk fat percentage, respectively. However, the interaction effect of MN and SBO on fat yield was not significant. Monensin reduced milk fat yield by 6.6%. Soybean oil linearly reduced milk fat yield and protein percentage and linearly increased milk yield and milk protein yield. Monensin and SBO reduced 4% fat-corrected milk and had no effect on DM intake. Monensin interacted with SBO to linearly increase milk fat concentration (g/100 g of FA) of total trans-18:1 in milk fat including trans-6 to 8, trans-9, trans-10, trans-11, trans-12 18:1 and the concentration of total conjugated linoleic acid isomers including cis-9, trans-11 18:2; trans-9, cis-11 18:2; and trans-10, cis-12 18:2. Also, the interaction increased milk concentration of polyunsaturated fatty acids. Monensin and SBO linearly reduced, with no significant interaction, milk concentration (g/100 g of FA) of short- and medium-chain fatty acids ( Collapse

Key Words Collapse

MESH Headings

• Animals
• Cattle/metabolism
• Diet
• Dietary Proteins/administration & dosage
• Eating
• Fats/analysis
• Fatty Acids/analysis
• Female
• Lactation
• Milk/chemistry
• Milk/drug effects
• Monensin/pharmacology
• Silage
• Soybean Oil/pharmacology
• Glycine max
• Zea mays

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Grants Collapse

Affiliation(s)

O AlZahal University of Guelph, Guelph, Ontario, N1G 2W1 Canada
N E Odongo
T Mutsvangwa
M M Or-Rashid
T F Duffield
R Bagg
P Dick
G Vessie
B W McBride

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Effects of prepartum administration of a monensin controlled release capsule on rumen pH, feed intake, and milk production of transition dairy cows

Effects of prepartum administration of a monensin controlled release capsule (CRC) on rumen pH, dry matter intake, and milk production during the transition period and early lactation were determined in 16 multiparous Holstein cows. Cows were divided into blocks of 2 depending on calving date. Cows were fed either a close-up dry cow or a lactating cow total mixed ration ad libitum. Rumen pH was monitored continuously using indwelling probes. Monensin did not affect average daily rumen pH, time below pH 6, time below pH 5.6, area below pH 6, and area below pH 5.6 throughout the experiment. Average daily pH, time below pH 6, and time below pH 5.6 before calving were 6.62, 65.6 min/d, and 17.6 min/d, respectively, and did not differ among the weeks before calving. Average daily pH, time below pH 6, and time below pH 5.6 were 6.19, 443.3 min/d, and 115.5 min/d, respectively, during the first week after calving, and were 6.36, 204.3 min/d, and 52.4 min/d, respectively, during the sixth week after calving. In the weeks after calving, average daily pH showed a quadratic increase, time below pH 6 showed a quadratic decrease, and time below pH 5.6 showed a linear decrease. Monensin did not affect dry matter intake and daily yields of milk, milk fat, and milk protein. Results suggest that prepartum administration of a monensin CRC did not increase rumen pH in multiparous cows fed the experimental diets during the transition period and early lactation.

Effect of Monensin Delivery Method on Dry Matter Intake, Body Condition Score, and Metabolic Parameters in Transition Dairy Cows

An investigation was conducted to compare the effects of the monensin controlled-release capsule, monensin sodium in feed, and a negative control on feed intake and metabolic parameters in a randomized and blinded clinical trial. A total of 136 Holstein cows and heifers were assigned to a negative control group, administered a monensin controlled-release capsule (CRC) or administered 22 mg/kg of dry matter of monensin sodium in the total mixed ration (premix). Cows were enrolled 3 wk prior to expected calving; at this time monensin treatment began. Cows were located at the Elora Dairy Research Centre (Elora, Ontario, Canada). Blood samples were obtained at enrollment, at 1 wk prior to expected calving date, at calving, and at 1 and 2 wk postpartum. Sera from these samples were analyzed for beta-hydroxybutyrate (BHBA), nonesterified fatty acids, glucose, urea, bilirubin, aspartate aminotransferase activity, insulin, and cortisol. Cows were assigned a body condition score upon enrollment and upon completion of the trial. The dry matter intake was measured for all cows for the entire experimental period (12.0, 11.7, and 11.3 kg/d for control, premix, and CRC groups, respectively). However, no differences in dry matter intake between treatment groups were noted. The interaction of experimental group and sampling time was significant for serum concentration of BHBA and urea. Both monensin delivery methods significantly decreased serum BHBA postpartum. Urea concentrations were increased in the postpartum period compared with the prepartum samples. The CRC group had a significant impact on reducing the loss in body condition over the study period. Serum concentrations of all measured metabolic parameters varied over the peripartum period. Calving season, parity, and body condition score at the start of the study period influenced many of the measured metabolic parameters.

Effect of dietary carbohydrate and monensin on expression of gluconeogenic enzymes in liver of transition dairy cows1

Thirty-four multiparous Holstein cows were used in a randomized block design to evaluate the effects of feeding nonforage fiber sources (NFFS), monensin, or their combination on expression of gluconeogenic enzymes in the liver during the transition to lactation. The addition of 0 or 300 mg/d of monensin to a conventional (CONV) or NFFS prepartum diet was evaluated in a 2 x 2 factorial arrangement of treatments. The NFFS diet was formulated by replacing 30% of the forage component of the CONV diet with cottonseed hulls and soyhulls. The CONV and NFFS basal diets were fed at dry-off and continued through parturition. Monensin was fed from -28 d relative to calving (DRTC) through parturition. At calving, all cows were placed on the same diet. Liver biopsy samples obtained at -28, -14, +1, +14, and +28 DRTC were used to determine pyruvate carboxylase (PC) and cytosolic phosphoenolpyruvate carboxykinase (PEPCK-C) mRNA expression. Feeding NFFS resulted in greater (P < 0.05) prepartum DMI compared with the CONV diet. There was no effect of prepartum diets on postpartum DMI or average milk production to 56 d of lactation. Expression of PC mRNA was elevated (P < 0.05) at 1 d postpartum, but there was no effect of NFFS or monensin on PC mRNA abundance. Expression of PEPCK-C mRNA at calving was increased (P < 0.05) with prepartum monensin feeding. The data indicate that feeding monensin to transition cows induces hepatic PEPCK-C mRNA expression before calving. The increased expression of hepatic PEPCK-C mRNA with monensin feeding suggests a feed-forward mechanism of metabolic control in ruminants that links molecular control of gluconeogenesis with the profile of rumen fermentation end products.

Efficacy of a lasalocid supplement in the diet of dairy cows in early lactation in a pasture-based dairy system

The lasalocid supplement, Bovatec, was fed to dairy cows at 300 mg of active ingredient for ~3 weeks precalving to up to 16 weeks postcalving in a pasture-based system. Sixty primiparous cows and 120 multiparous cows were allocated to equivalent control and lasalocid groups based on expected calving date, size and previous production history. To facilitate the feeding of the lasalocid, it was mixed with maize silage (~1 kg DM/cow.day) and fed as one feed on a concrete feed pad early in the morning each day before calving and before the afternoon milking during lactation. The control group received the maize silage without lasalocid. Otherwise, the feeding of both groups was exactly the same. The key response associated with adding lasalocid to the diet differed between the primiparous and multiparous cows. Although the average daily milk yield responses to lasalocid were not significant (P > 0.05) at 1.1 and 0.6 kg/cow for the primiparous and multiparous cows, respectively, significant (P < 0.05) increases in the milk yield of the primiparous cows were consistently recorded between weeks 5 and 15 of lactation. With the multiparous cows, there was a significant (P < 0.05) decrease in the circulating concentrations of serum β-hydroxybutyrate in those fed the lasalocid, with this being related to a tendency (P = 0.087) for these animals to maintain higher body condition scores for much of the early lactation treatment period. There were no other treatment differences of biological importance.

Effects of feeding propionibacteria to dairy cows on milk yield, milk components, and reproduction

Two weeks before parturition, 38 Holstein primiparous and multiparous cows were assigned to 1 of 3 treatment groups: control animals (n = 13) received regular total mixed rations (TMR), the low-dose group (n = 14) received the control TMR plus 6 x 10(10) cfu/cow of Propionibacterium strain P169 (P169), and the high-dose group (n = 11) received the control TMR plus 6 x 10(11) cfu/cow of P169 from -2 to 30 wk postpartum. Weekly milk samples were analyzed for percentage of milk fat, protein, lactose, and SNF, milk urea nitrogen, and somatic cell counts. Daily milk production expressed as 4% fat-corrected milk was affected by treatment and week x parity. High-dose and low-dose P169-treated cows exhibited 7.1 and 8.5% increases above controls in daily 4% fat-corrected milk, respectively. Treatment x parity and week significantly influenced percentage of milk fat, lactose, and protein, whereas treatment x parity and treatment x week influenced SNF. Ruminal propionate levels were influenced by treatment such that high-dose P169 cows had greater molar percentage of propionate than did low-dose P169 and control cows. Change in body weight postpartum was influenced by week x parity and treatment x parity such that high-dose and low-dose P169 multiparous cows exhibited a more rapid recovery of wk-1 body weight than did control multiparous cows. There was no treatment, parity, or interaction on days to first postpartum ovulation or on estrous behavior at 45 and 90 d postpartum. We concluded that P169 might have potential as an effective direct-fed microorganism to increase milk production in dairy cows.

Monensin for Lactating Dairy Cows Grazing Mixed-Alfalfa Pasture and Supplemented with Partial Mixed Ration

The effect of monensin on milk production was evaluated in 58 lactating Holstein cows (48 multiparous; 10 primiparous) grazing a mixed-alfalfa pasture and supplemented with a partial mixed ration in a completely randomized design with repeated measurements. Cows were paired by calving date, lactation number, previous lactation milk production, body weight, and body condition score and were assigned to one of 2 treatments: control or monensin. Cows on the monensin treatment received 2 monensin controlled-release capsules (335 mg/d for 90 d), one 30 d before the expecting calving date and the other 60 d after calving. Short-term (0 to 150 d in milk) and long-term (305-d adjusted lactation) effects of monensin were evaluated. Pasture (measured by difference between pre- and postgrazing pasture mass), supplements, and total dry matter intake did not differ between treatments and averaged 8.7, 14.1, and 22.9 kg/d, respectively. In the short-term, monensin increased milk production (27.7 vs. 26.6 kg/d) and milk protein yield (0.890 vs. 0.860 kg/d); milk fat yield was not affected (0.959 kg/d). Monensin decreased milk fat content (3.51 vs. 3.60%) with no changes in milk protein content (3.25%). In the long term, milk production and milk protein yield were also increased by monensin: 214 and 7 kg, respectively. Monensin reduced the loss of body condition score and increased percentage of pregnancy at first service (44.8 vs. 20.7%). Monensin improves production and reproduction performance of dairy cows grazing a mixed-alfalfa pasture and supplemented with a partial mixed ration.

Ionophore taste preferences of dairy heifers1

Two taste preference studies were conducted using six Holstein heifers in each experiment to determine preferences for no ionophore, lasalocid, or monensin in the diet. In Exp. 1, individually penned (approx. 5 mo old; 220 +/- 14 kg BW) heifers were fed a basal total mixed ration containing 46% corn silage, 46% grass haylage, and 8% soybean meal (DM basis). There were five treatments (mg/kg BW(-1)*d(-1)): 0 ionophore (control), 1 lasalocid (1L), 2 lasalocid (2L), 1 monensin (1M), or 2 monensin (2M). Ionophores were provided as part of the mineral mix that had been added to the control diet and through an ionophore-grain by-product mix to make the 2L and 2M treatments. All five diets were offered for 7 d, with the first 2 d for adaptation and the last 5 d for measurement of feed intake. The most preferred diet was then removed and the study continued with the four remaining diets. The most preferred diets were again eliminated sequentially, so that only two diets remained on d 13 and 14. Each feeding segment ranking of treatment preferences was determined based on the weight of feed refused at the end of each feeding segment. In Exp. 2, six 6-wk-old heifers (75 +/- 5 kg of BW) were individually fed either 0, 1L, or 1M in a study similar to Exp. 1, except that the most preferred diet was removed after 4 d, with the first day for adaptation and the last 3 d for measurement of feed intake. In Exp. 1, orthogonal contrasts indicated that heifers preferred the 1L and 2L diets over the 1M and 2M diets. Preferences between diet concentrations of ionophores (1 and 2 mg/kg of BW; Exp. 1) and the control and ionophore treatments did not differ, nor was there an interaction between ionophores and their concentration. Dairy heifers previously fed lasalocid prefer lasalocid over monensin when given a choice; however, heifers without previous exposure to an ionophore did not indicate a preference (Exp. 2).

Production and Health of Pasture-Fed Dairy Cattle Following Oral Treatment with the Ionophore Lasalocid

The aim of the study was to evaluate the effect of feeding the ionophore lasalocid on the productivity and health of seasonally calving, pasture-fed dairy cows. Dairy cows (n = 1020) from 4 herds were enrolled in a split-herd, prospective intervention study. Cows were blocked by breed and age, ranked on previous production, and then assigned to 2 treatment groups. Treatment cows were each exposed to 300 to 350 mg of lasalocid/d commencing 3 wk before and ending 18 wk after the start of the seasonal calving period. Milk production was determined on 3 occasions for each cow at approximately monthly intervals (herd tests 1 to 3), body condition score was determined fortnightly, and all disease occurrences were recorded. Lasalocid treatment increased milk volume milk protein and milk fat production by approximately 2%, without altering milk composition. Fewer lasalocid-treated cows than control cows (7.3 vs. 11.6%, respectively) were diagnosed with clinical mastitis. Lasalocid treatment of pasture-fed dairy cows resulted in reduced mastitis incidence and increased milk production without changes in body condition or negative effects on metabolic processes as monitored by metabolite concentrations.

Production and Blood Parameters of Holstein Cows Treated Prepartum with Sodium Monensin or Propylene Glycol

Forty-five multiparous Holstein cows were assigned to one of 3 treatments in a randomized complete block design. The objective was to evaluate the effects of sodium monensin (M) and propylene glycol (PPG) during the prepartum period on performance and metabolic parameters during the late dry and first 9 wk postpartum for cows receiving M postpartum. Treatments were: control (C), M in a controlled-release capsule to deliver 335 +/- 33 mg/d for approximately 100 d, and 300 mL/d of PPG drenched orally. Treatments started at 35 and 21 d prior to the expected date of calving for cows receiving M and PPG, respectively. To ensure that all treatments would be restricted to the prepartum period, C and PPG cows received a M controlled-release capsule in the first 24 h after calving. Prepartum propylene glycol administration increased concentrations of glucose and insulin, and decreased beta-hydroxybutyrate and nonesterified fatty acids in plasma prepartum. Milk production was similarly affected by treatments. However, prepartum M treated cows tended to produce more 3.5% fat-corrected milk compared with control, but similar to PPG. Milk fat content and yield tended to be greater for cows that received M prepartum than for C cows, while PPG cows were similar to M and C. Prepartum administration of M decreased milk protein content, but no effect was observed on protein yield.

Ovarian Follicular Activity in Lactating Holstein Cows Supplemented with Monensin

The objective of this study was to determine effects of monensin on ovarian follicular development and reproductive performance in postpartum dairy cows. Forty-eight multiparous Holstein cows were randomly assigned to receive either a control total mixed ration (n = 24) or the same diet plus 22 mg of monensin/kg (n = 24) from 21 d before anticipated calving until cows were either confirmed pregnant or were >180 d postpartum. Monensin had no effect on development of the first dominant follicle postpartum or the numbers of class 1 (3 to 5 mm), 2 (6 to 9 mm), or 3 (10 to 15 mm) follicles. Control cows had more class 4 (>15 mm) follicles at 10 to 13 d postpartum than cows in the monensin group. The first dominant follicle postpartum ovulated, regressed, or became cystic unrelated to differences between diets. However, the first ovulation postpartum occurred earlier in monensin-fed cows than in the control group (27.2 +/- 2.1 d vs. 32.4 +/- 1.5 d), with no dietary effects on the diameter of the ovulating follicle. Similarly, treatments did not differ in the proportion of cows with 2 or 3 waves of ovarian follicular development per cycle, nor in the number of follicles of all classes during the breeding period. Times of ovulation following treatment with prostaglandin F2alpha were not different between dietary groups. Pregnancy rates after timed artificial insemination were similar between diets. Supplementation with monensin resulted in a shorter postpartum interval to first ovulation but did not affect other reproductive measures in healthy, lactating dairy cows.

Effect of a monensin controlled release capsule on metabolic parameters in transition dairy cows

A prospective field study involving 251 Holstein cows and heifers from five dairy farms near Guelph, Ontario, Canada, was conducted to measure the effect of monensin delivered in a controlled release capsule 3 wk precalving on metabolic function in dairy cows immediately pre- and postcalving. At 3 wk before expected calving, cows were randomly assigned to receive either a controlled release capsule containing monensin or to serve as negative controls. Cows were blood sampled once per week precalving and once in the week following calving, at the same time of day and the same day of the week. Serum was evaluated for beta-hydroxybutyrate (BHBA), nonesterified fatty acids (NEFA), cholesterol, urea, glucose, calcium, and phosphorus. Monensin-treated cows had significantly decreased NEFA and BHBA and significantly increased concentrations of serum cholesterol and urea in the week immediately precalving. No effect of treatment was observed for calcium, phosphorus, or glucose in the precalving period. After calving, concentrations of phosphorus were lower and BHBA tended to be lower, and cholesterol and urea were higher in monensin-treated cows. There was no effect of treatment on NEFA, glucose, or calcium in the first week postcalving. Monensin treatment administered precalving significantly improved indicators of energy balance in both the immediate precalving and postcalving periods. The findings indicate better energy metabolism in monensin-treated cows as they approach calving. Improvement of energy balance before calving is important for the prevention of energy associated metabolic diseases, such as retained placenta, clinical ketosis, and displaced abomasum, which might occur immediately postcalving.

Effects of a monensin controlled-release capsule or premix on attenuation of subacute ruminal acidosis in dairy cows

The effects of monensin, administered either as a controlled release capsule (CRC) or a premix, on attenuating grain-induced subacute ruminal acidosis (SARA) and on ruminal fermentation characteristics in Holstein cows receiving a total mixed ration were investigated in two experiments. In both experiments, six multiparous, rumen-fistulated Holstein cows were used in a two-treatment, two-period crossover design with 6-wk periods. In Experiment 1, treatments were either a monensin CRC or a placebo CRC. In Experiment 2, treatments were either a monensin premix or a placebo premix. In both experiments, at the beginning of wk 4 SARA was induced in experimental cows for a 10-d period with a grain challenge model, and ruminal pH was measured continuously using indwelling pH probes. The administration of monensin either as a CRC or a premix had no effect on ruminal pH characteristics. Neither monensin CRC nor premix had an effect on ruminal volatile fatty acid concentrations, but reduced the acetate:propionate ratio. Monensin premix-treated cows were observed to have increased milk yield, largely as a result of a higher dry matter intake in monensin-treated cows compared to control cows. Milk fat content and yield were lower in monensin-treated cows compared to placebo-treated cows during SARA. In conclusion, there is no evidence that monensin was efficacious in raising ruminal pH during SARA under the conditions employed in this study.

Prepartum monensin for the reduction of energy associated disease in postpartum dairy cows

A total of 1317 Holstein cows from 45 farms in the Canadian provinces of Quebec, Prince Edward Island (PEI) and Ontario were enrolled in a randomized trial during 1998 and 1999 to further confirm the efficacy of a monensin controlled release capsule in preventing periparturient disease in lactating dairy cows. Cows were randomized on the farms to receive either a monensin controlled release capsule (CRC) 2 to 4 wk before expected calving or to serve as negative controls. Health data were collected for 90 d postcalving and were analyzed with logistic regression accounting for the intraherd correlation with generalized estimating equations. Monensin CRC significantly reduced the incidence of both clinical ketosis and abomasal displacement post-calving. There was a numerical but nonsignificant decrease in the incidence of retained placenta in cows receiving a monensin CRC. A pooled analysis of two separate but similar studies (conducted in 1995 and 1998) demonstrated a strengthened association between monensin CRC administration precalving and reduced periparturient disease. A 40% reduction in both abomasal displacement and clinical ketosis was observed with precalving administration of a monensin CRC. In addition, the larger dataset highlighted a trend for a 25% reduction in the incidence of retained placenta in monensin-treated cows. Improved energy metabolism as a result of monensin treatment is likely the mechanism for the reduction in incidence of all three of these diseases. Thus the term "energy associated disease" was created to assess the combined impact of the precalving monensin treatment on the incidence of retained placenta, displaced abomasum, and clinical ketosis. The monensin controlled release capsule reduced the incidence of energy associated disease by 30%.