[Show abstract][Hide abstract] ABSTRACT: The aim of this study was to estimate the potential profitability of a combined supplement of folic acid and vitamin B-12 given around parturition and in early lactation in commercial dairy herds in Que ' bec. A total of 791 dairy cows from 14 herds were enrolled. Cows were assigned to weekly intramuscular injections of saline or 320 mg of folic acid and 10 mg of vitamin B-12. Treatments began 3 wk before the expected calving date and lasted until 8 wk of lactation. Within each herd, data on production, reproduction, and incidence of metabolic disorders and other diseases were recorded. With regard to the Canadian dairy industry, which operates under a supply management system, two scenarios were studied: (1) quota kept constant and (2) number of cows kept constant. For scenarios 1 and 2, eight and seven herds out of 14, respectively, obtained a positive annual net margin per cow following the vitamin supplement. The average net margins were Can$ 31.18 and Can$-4.86 N cow(-1) yr(-1) for scenarios 1 and 2, respectively. The variability of the response highlights that supplies of these vitamins by ruminal synthesis were probably different among herds and actual knowledge does not allow predicting supplies according to the diet.
Full-text · Article · Dec 2014 · Canadian Journal of Animal Science
[Show abstract][Hide abstract] ABSTRACT: The present study aimed to determine whether the improvement in postpartum energy balance frequently reported in cows under short dry period management could be due to an improvement in ruminal function related to the reduction in the number of diet changes before calving. Six multiparous and 6 primiparous Holstein cows equipped with ruminal cannula were assigned to 6 blocks of 2 cows each according to parity, projected milk production at 305 d, and expected calving date. Within each block, cows were randomly assigned to either a conventional (CDP; 63.2 ± 2.0 d) or a short dry period (SDP; 35.2 ± 2.0 d) management in a randomized complete block design. The CDP cows were fed a far-off diet until 28 d before calving, followed by a prepartum diet, whereas SDP cows received only the prepartum diet. After calving, both groups were fed the same lactation diet. Milk yield and dry matter intake (DMI) were recorded daily and milk composition, weekly. Blood samples were taken twice a week during the first 4 wk postcalving and weekly otherwise. Omasal and ruminal samples were collected approximately 3 wk prior and 3 wk after calving. From 28 d before calving until calving, when the 2 groups of cows were fed the same prepartum diet, there was no effect of the dry period length management on DMI, plasma concentrations of β-hydroxybutyrate, nonesterified fatty acids, and glucose and nutrient digestibility in the rumen. However, CDP cows tended to have lower ruminal pH and higher ruminal concentrations of total volatile fatty acids than SDP cows. From calving to 60 d in milk, daily DMI was higher for SDP than for CDP cows (22.3 ± 0.44 vs. 20.7 ± 0.30 kg), but milk production and milk concentrations and yields of fat, protein, and total solids were not affected by the dry period length management. After calving, body weight loss was reduced and body condition score tended to increase more rapidly for SDP than for CDP cows. Nutrient digestibility in the rumen, expressed in kilograms per day, was greater or tended to be greater for SDP cows, but differences were no longer significant when expressed per unit of nutrient ingested. The decrease in plasma nonesterified fatty acids and β-hydroxybutyrate in SDP cows without effect on milk yield suggests an improved energy balance likely due to greater DMI. Results from the present study seem to indicate that reducing the number of diet changes before calving could facilitate ruminal adaptation to the lactation diet and improve energy balance postpartum.
No preview · Article · Oct 2014 · Journal of Dairy Science
[Show abstract][Hide abstract] ABSTRACT: The purpose of this study was to measure the effects of a supplementation in folic acid and vitamin B-12 given before calving and in early lactation on milk production and components within the first 60 days in milk (DIM) as well as the 305-d yield, and on indicators of energy balance for dairy cows in commercial dairy herds. A total of 805 dairy cows (271 primiparous and 534 multiparous) in 15 commercial dairy herds were involved. From February to December 2010, every 2 mo and within each herd, cows were assigned, according to parity, predicted 305-d milk production, and calving interval to receive weekly intramuscular injections (5 mL) of either 1) saline 0.9% NaCl (Control) or 2) 320 mg of folic acid+10 mg of vitamin B-12 (Vitamins). Treatments began 21 (SD 8) d before the expected calving date and lasted until 60 (SD 4) DIM. For the first 60 DIM, average milk yield was 35.0 kg/d and was not affected by treatment. On average, milk fat concentration was decreased in early lactation for cows in the vitamin group as compared with control, from 42.1 to 40.3 g/kg whereas milk protein concentration was increased by the supplement, from 30.9 to 31.5 g/kg. Milk lactose and milk urea nitrogen concentrations were unaffected by treatment. No treatment effect was found on 305-d milk and protein yields. The vitamin supplement reduced 305-d milk fat yield in primiparous cows as compared with controls whereas no treatment effect was observed for multiparous cows. As indicators of energy balance, the fat:protein ratio was decreased by 0.06 and body condition score losses after calving tended to be smaller for cows in the vitamin group as compared with control. The decrease of the fat:protein ratio by the vitamin supplement was greater in primiparous cows than in multiparous cows. Cows receiving the vitamin supplement lost less body weight (estimated by heart girth circumference) during the first 60 DIM than control cows. Estimated body weight losses of 22.8 and 30.3 kg were recorded for vitamin and control cows, respectively. The observed reduction in estimated body weight loss coupled with a reduction of the fat:protein ratio without effect on milk yield suggest that supplementary folic acid and vitamin B-12 could have an effect on energy partitioning in early lactation.
No preview · Article · Sep 2014 · Livestock Science
[Show abstract][Hide abstract] ABSTRACT: Abstract Text: Subclinical ketosis is a common early lactation disorder. Herd prevalence is often unknown because there are no specific clinical symptoms and because individual testing of dairy cows can be costly and time consuming. Since October 2011, Valacta (Dairy Centre of Expertise, Quebec and Atlantic Canada) offers routine infra-red testing of β-hydroxybutyrate (BHB) in DHI milk samples. Over 293,000 milk samples from fresh cows (DIM 5-35) from 4179 dairy herds have been analyzed for BHB concentration (199,003 multiparous and 94,036 primiparous cows). Based on a previously published trial comparing blood and milk BHB concentrations, thresholds were established as follows: cows with milk BHB concentrations ≥ 0.20 mM were declared ketotic (POS); cows with milk BHB concentrations below 0.15 mM were declared non-ketotic (NEG); and cows with intermediate BHB concentrations were classified as potentially ketotic (SUSPECT). Overall incidence of subclinical ketosis (POS and SUSPECT) was 24.7% over the first 5 weeks of lactation. Incidence for DIM 5 to 35 was 21.5% and 26.6% for primiparous and multiparous cows, respectively. Distribution of incidence in relation to DIM was different between primiparous and multiparous cows. Highest incidence for primiparous cows (33.7%) was in the first week postpartum but in the third week for multiparous cows (33.5%). By DIM 35, incidence declined to 13.1% and 17.9% for primiparous and multiparous cows, respectively. Among herds with at least 10 cows analyzed for BHB (n=3560), within herd prevalence of ketosis for the 10th, 25th, 50th, 75th and 90th percentile were 11, 17, 24, 33 and 43% respectively. Ketosis prevalence was affected by month of calving (P<0.001). Highest incidence was observed for cows calving in May-June and October-November whereas lowest incidence was observed for cows calving in August and September. Ketosis prevalence was also affected by breed (P<0.001). Prevalence for Ayrshire (n=12,443), Brown Swiss (n=1814), Holstein (n=271,367) and Jersey (n=6554) cows was 24.4, 22.7, 24.7 and 34.6%, respectively. Milk BHB concentration was negatively correlated with milk Fat:Protein ratio (R=-0.39; P<0.001) and the correlation was affected by breed. Correlations between milk BHB and Fat:Protein ratio were -0.34, -0.35, -0.39 and -0.32 for Ayrshire, Brown Swiss, Holstein and Jersey cows, respectively (P<0.001). Results indicate subclinical ketosis incidence varies greatly among dairy herds and is influenced by breed and season. Monitoring of subclinical ketosis prevalence is important as a first step towards greater transition success.
Keywords: Ketosis, Dairy cow, DHI
[Show abstract][Hide abstract] ABSTRACT: Abstract Text:
Effects of forage particle length on apparent ruminal synthesis and post-ruminal supply of thiamin and vitamin B12 were evaluated in two experiments. Alfalfa and orchardgrass were harvested and ensiled at two theoretical lengths of cut: 19-mm (long cut, LC) or 10-mm (short cut, SC). Within a forage type, rations containing silages of each length of cut as the sole forage were offered to ruminally and duodenally cannulated lactating Holstein cows in crossover design experiments. Experiment 1 compared diets containing LC and SC alfalfa silage (~47% forage, ~20% forage NDF and ~25% total NDF) offered to 13 cows in two 19-d treatment periods. Experiment 2 compared diets containing LC and SC orchardgrass silage (~50% forage, ~23% forage NDF and ~28% total NDF) offered to 15 cows in two 18-d treatment periods. In Experiment 1, intakes of thiamin and vitamin B12 were greater (P<0.01) for LC than SC (thiamin: 89.4 vs. 77.5 ± 2.13 mg/d; vitamin B12: 118.6 vs. 67.1 ± 2.55 µg/d). Neither duodenal flows of thiamin (P=0.94, 174.2 ± 18.87 mg/d) and vitamin B12 (P=0.17, 8223 ± 713.0 µg/d) nor apparent ruminal synthesis of these vitamins (thiamin, P=0.15, 90.9 ± 17.82 mg/d; vitamin B12, P=0.16, 8131 ± 711.0 µg/d) were affected by treatment in Experiment 1. In Experiment 2, there was no effect of treatment on the intake of vitamins (thiamin, P=0.79, 71.9 ± 2.55 mg/d; vitamin B12, P=0.85, 111 ± 3.9 µg/d), duodenal flows (thiamin, P=0.80, 156 ± 9.5 mg/d; vitamin B12, P=0.88, 6887 ± 476.0 µg/d), or their apparent ruminal synthesis (thiamin, P=0.82, 84.1 ± 8.14 mg/d; vitamin B12, P=0.88, 6725± 473.0 µg/d). The reduction of legume particle length decreased the dietary supply of thiamin and vitamin B12. However, forage particle length, in the studied range, did not affect apparent synthesis of thiamin and vitamin B12 in rumen or the supply of these vitamins to the sites of absorption.
Keywords: dairy cow, thiamin, vitamin B12
[Show abstract][Hide abstract] ABSTRACT: Abstract Text: The transition period is the most critical time in the lactation cycle of a cow. It is generally accepted that a successful transition will have a positive impact on performances in the following lactation. Several years ago, Nordlund and collaborators have developped the Transition Cow Index® (TCI): a tool to objectively evaluate transition. These authors have previously identified feedbunk space, number of group changes and size and comfort of rest area as the main factors affecting transition success in freestall herds. The aim of the present study was to identify factors that have an impact on transition success specifically in tie stall herds. Tie stall dairy herds (n=48) from Qubec, Canada were selected based on their average TCI to have high and low TCI herds. Each herd was visited and producers were asked to complete a survey on their management decisions and practices (examples: number of place changes, number of daily feed push ups, boluses). In addition, several observations and measures (examples: stall dimensions, type and amount of bedding, lighting) were taken on each farm. Results suggest that nervousness of cows was the most important factor affecting transition success (calm vs nervous cows, observed on the day of the visit; P = 0.04). Use of straw and woodshavings as bedding at any stage of the transition period significantly increased TCI (P≤0.03) whereas type of flooring (any type of mat vs concrete) had no impact (P≥0.15). Providing a Rumensin bolus to dry cows tended to improve TCI (P=0.09). Number of place changes during the transition period (P=0.09) and number of times feed is pushed back (P=0.07) tended to positively impact TCI. Stall dimension factors significantly correlated with TCI are reported in the table below.
Stall length far-off cows
Stall length precalving cows
Stall width precalving cows
Stall width fresh cows
Keywords: Transition success, TCI,Tie stall
[Show abstract][Hide abstract] ABSTRACT: Abstract Text:
In Qubec, Canada, age at first calving occurs on average at 27 mo whereas the target is 22-24 mo to maximize herd profitability. The aim of this study was to generate indicators (such as heifer weight and height at 15 and 24 mo, and age at which optimal weight for breeding is attained i.e. 55% of mature weight) and their respective relative accuracy (RA) using a growth predicting model based on random regression. Weight and height data records from 1995 to 2012, respectively measured by chest girth, and height at the withers on Holstein (HO), Jersey (JE), and Brown Swiss (BS) dairy heifers were obtained from Valacta database (DHI agency, Ste-Anne-de-Bellevue, QC, Canada). Heifers with less than 2 records were excluded from the analysis. For each heifer, weight at 15 and 24 mo were computed using a second degree polynomial equation for which individual parameters were obtained from random regression using R (v1.15.2) and nlme package. For height, a non-linear mono-molecular random regression model was used. Age at optimal breeding weight was calculated by the square root of the second degree polynomial equation. Relative accuracy was calculated as the prediction error variance, relative to an RA of 99% when a heifer was measured routinely every 3 mo, starting at 2 mo of age. Table 1 shows the mean, standard deviation (SD) of the five indicators described above, RA and mature weight. It is possible to observe that, on average, dairy heifers in Qubec, Canada could be bred at 13.6 mo, the optimal age for a first calving at 24 mo. These indicators could be calculated on an individual-heifer and on a herd-level basis, and used on farm as a management tool for reducing age at first breeding and at first calving.
Table 1. Indicators with their respective relative accuracy (RA, %)
Weight at 15 mo (kg)
Weight at 24 mo (kg)
Height at 15 mo (cm)
Height at 24 mo (cm)
Age at optimal breeding weight (mo)
Age at first breeding
Age at first calving
[Show abstract][Hide abstract] ABSTRACT: Increased production of dairy cows over the past years has triggered interest in reviewing optimal duration and management for the dry period. Results from recent studies suggest reduced early lactation negative energy balance, reduced ketosis, improved reproduction and no negative effects on production for multiparous cows. With regard to primiparous cows, production following lactation is reduced, but compensated for by the additional end of lactation milk. Reduced dry period length does not impair udder health, but is associated with increased risk of antibiotic residues in early lactation in the case of an early calving. Although the literature is scarce, calf health and immunity transfer are not affected by a short dry period. The objectives of the present review are to summarize results from recent trials and propose avenues for further research on short dry period management. Precise management conditions as well as specific cow characteristics for which short dry period results are optimized still need to be defined.
Full-text · Article · May 2014 · Canadian Journal of Animal Science
[Show abstract][Hide abstract] ABSTRACT: This study was undertaken to determine the effect of a combined folic acid and vitamin B12 supplement given in early lactation on culling rate, metabolic disorders and other diseases, and reproduction in commercial dairy herds. A total of 805 cows (271 primiparous and 534 multiparous cows) in 15 commercial dairy herds were involved. Every 2 mo from February to December 2010 and within each herd, cows were assigned according to parity, previous 305-d milk production, and calving interval to 5 mL of either (1) saline 0.9% NaCl (control group) or (2) 320 mg of folic acid + 10 mg of vitamin B12 (vitamin group). Treatments were administered weekly by intramuscular injections starting 3 wk before the expected calving date until 8 wk after parturition. A total of 221 cows were culled before the next dry period. Culling rate was not affected by treatment and was 27.5%; culling rate was greater for multiparous (32.2%) than for primiparous cows (18.8%). Within the first 60 d in milk (DIM), 47 cows were culled, representing 21.3% of total culling, and no treatment effect was noted. Ketosis incidence based on a threshold ≥100 µmol/L of β-hydroxybutyrate in milk was 38.3 ± 2.9% for the vitamin group and 41.8 ± 3.0% for the control group and was not affected by treatment. The combined supplement of folic acid and vitamin B12 did not decrease incidence of retained placenta, displaced abomasum, milk fever, metritis, or mastitis. However, the incidence of dystocia decreased by 50% in multiparous cows receiving the vitamin supplement, although no effect was observed in primiparous cows. The first breeding postpartum for multiparous cows occurred 3.8 d earlier with the vitamin supplement compared with controls, whereas no treatment effect was seen for primiparous cows. Days open, first- and second-breeding conception rates, number of breedings per conception, and percentage of cows pregnant at 150 DIM were not affected by treatment. The reduced percentage of dystocia combined with the earlier DIM at first breeding for multiparous cows receiving the combined supplementation in folic acid and vitamin B12 indicates that the vitamin supplement had a positive effect in older cows.
No preview · Article · Jan 2014 · Journal of Dairy Science
[Show abstract][Hide abstract] ABSTRACT: The Canadian dairy industry operates under a supply management system with production quotas (expressed in kilograms of butterfat per day) owned by dairy producers. Any management strategy influencing production responses must, therefore, be evaluated to estimate its effects on quota needed to sell the milk produced. In the present study, half of the cows from 13 commercial herds (850 cows, average of 70 cows per herd) were assigned to be managed for a short dry period (SDP; 35 d dry) and the other half was managed for a conventional dry period (CDP; 60 d dry) to evaluate the economic impact of a steady state involving either CDP or SDP. Economic variables included in the partial budget were: variations in revenues from milk and components as well as animals sold; costs related to feeding, reproduction, replacement, housing, and treatments. All variables were first estimated on a cow basis for each herd individually, and average results were used to calculate the partial budget for an average herd. Yearly milk and component yields per cow increased, which implies that fewer cows are required to produce the same amount of quota. Accordingly, 2 scenarios were investigated: in the first one, available quota was kept constant, and herd size was adjusted to avoid over-quota production. Consequently, the partial budget was calculated considering that 5 fewer cows were present in the herd. In this situation, switching to an SDP management increased net annual income for the farm by $2,677 (Can$), which represents $41.38 per cow. In the second scenario, the number of cows was kept constant, but additional quota (5.5 kg/d, $25,000/kg) was bought to allow selling all of the milk produced. In this case, net farm income was increased by $17,132 annually with SDP, which represents $245.18 per cow. This budget includes interest on the purchase of quota. A comparison of partial budgets for individual herds involved in the study revealed considerable variation among herds. Switching from a CDP to a SDP management would be beneficial for average dairy herds in eastern Canada.
[Show abstract][Hide abstract] ABSTRACT: A total of 850 Holstein cows from 13 commercial dairy herds were involved in the present study to compare the effects of 2 different dry period (DP) management strategies on health and reproductive parameters. Cows were assigned to either a short (SDP; 35-d) or a conventional (CDP; 60-d) DP management within each herd, based on previous 305-d milk yield, parity (414 primiparous and 436 multiparous), and estimated calving interval. Cows assigned to CDP were fed a dry cow ration from dry-off until 21 d prepartum, and were then switched to a precalving ration. Cows assigned to SDP were fed the precalving ration throughout their DP. Rations were specific to each herd. A significant treatment × parity interaction was found for culling rate. Dry period management did not affect culling rate for second-lactation cows but a significantly higher culling rate occurred in multiparous CDP cows compared with SDP (42.6 vs. 31.6% ± 3.7 for CDP and SDP, respectively). Management used in the DP did not affect incidence of severe ketosis, displaced abomasum, milk fever, and mastitis, although incidence of these metabolic disorders were lower in second-lactation than third- or greater-lactation cows. The incidence of mild ketosis (evaluated by milk ketone concentration) was lower following SDP, probably as a result of better energy balance. On the other hand, the incidence of retained placenta was higher in multiparous cows assigned to SDP, but the reason for this increase remains unclear. Nevertheless, this did not lead to increased incidence of metritis. Moreover, DP management did not influence reproductive measures, including days in milk at first breeding, number of breedings per conception, as well as conception rates at first and second services. Regarding days open, overall, all 13 herds were not significantly affected by treatment, but 1 herd clearly showed opposite results to the 12 others. Our results indicate that a short DP management strategy could facilitate transition from one lactation to the next by decreasing the incidence of mild ketosis, with no major negative effects on other health parameters and reproduction. The variation in results observed among herds suggests that other management practices influence the response observed following a short or conventional DP, emphasizing the need for other field studies.
[Show abstract][Hide abstract] ABSTRACT: A total of 850 cows distributed among 13 commercial Holstein herds were involved in this study to compare the effects of 2 different dry period (DP) management strategies on milk and component yields as well as body condition score (BCS) over complete lactations. Within each herd and every 2 mo, cows were assigned to a short (35 d dry; SDP) or conventional (60 d dry; CDP) DP management based on previous lactation 305-d milk yield, predicted calving interval, and parity: primiparous (n=414) and multiparous (n=436). Cows assigned to CDP were fed a far-off dry cow ration from dry-off until 21 d prepartum, and were then switched to a precalving ration. Cows assigned to SDP were fed the precalving ration throughout their DP. Rations were different across herds, but the late-lactation, precalving, and early lactation rations were identical for both treatment groups within each herd. Additional milk was obtained at the end of lactation from cows assigned to SDP due to the extended lactation. Average daily milk yield in the following lactation was not different between treatments for third- or greater-lactation cows, but was significantly decreased in second-lactation SDP cows. However, when expressed as energy-corrected milk, this difference was not significant. Although lower for primiparous than multiparous cows, body weight and BCS were not affected by DP management strategy. Milk production and BCS responses to treatments varied among herds. Results from the present study suggest that a short DP management strategy could be more appropriate for today's dairy cows, although not suitable for all cows or all herds.
No preview · Article · May 2011 · Journal of Dairy Science
[Show abstract][Hide abstract] ABSTRACT: The aim of the project was to calculate the apparent synthesis or destruction of cobalamin (vitamin B(12)) and its analogs in the rumen as well as their apparent intestinal disappearance in dairy cows. Four lactating cows were fed a diet supplemented with cobalt alone (0.76 mg/kg of DM; control) or with cobalt and vitamin B(12) (cyanocobalamin, 500 mg/d; treated). In addition to cobalamin, the only biologically active molecule for the cow, 7 analogs were identified in duodenal and ileal digesta: cobinamide, which lacks the base, ribose, and phosphate groups; and 6 other molecules in which the base, 5,6-dimethylbenzimidazole, is replaced by cresol, 2-CH(3)-adenine, adenine, 2-CH(3)-S-adenine, or 5-OH-benzimidazole, or an unidentified cobamine. Small amounts of cobalamin and cobinamide were detected in the total mixed ration, but apparent synthesis of all forms took place in rumen. During the control period, cobalamin represented 38% of the total amounts of corrinoids produced in rumen. Approximately 11% of the average daily intake of cobalt was used for apparent ruminal synthesis of corrinoids, of which only 4% was incorporated into cobalamin. Only 20% of the supplement of cyanocobalamin was recovered at the duodenal level; cobinamide appeared to be the major product of degradation of supplementary cyanocobalamin in the rumen. During the control and treatment periods, there was an apparent intestinal disappearance of cobalamin and 5-OH-benzimidazole cobamide only; only the apparent intestinal disappearance of cobalamin differed between the 2 periods. Although cobalamin was not the major form synthesized by ruminal microflora and, even if supplementary cyanocobalamin was extensively destroyed by ruminal microflora, based on calculations of apparent intestinal disappearance, cobalamin seems to be the major form absorbed in the small intestine.
No preview · Article · Oct 2009 · Journal of Dairy Science
[Show abstract][Hide abstract] ABSTRACT: Biotin is present in nature either free or as biocytin, which is only degraded under the action of a specific enzyme: biotinidase. This enzyme is not included in analytical assays generally used. A method for sample preparation using biotinidase was developed in our laboratory before analysis by ELISA. Three cows equipped with duodenal and ileal cannulae were used to compare the effects of methods of sample preparation on calculations of apparent ruminal synthesis and intestinal absorption of biotin. There was no apparent ruminal synthesis of biotin, no matter whether free or total biotin was measured (p = 0.84). Results also suggested that rumen microbes cannot utilize nor degrade biocytin present in the feed. Estimates of apparent intestinal absorption were influenced by the sample preparation method (p = 0.002). Analysis of free biotin caused an artefact, suggesting intestinal synthesis of this vitamin; whereas determination of total biotin concentrations showed that absorption was taking place in the small intestine.
No preview · Article · Jul 2007 · Archives of animal nutrition
[Show abstract][Hide abstract] ABSTRACT: Two studies were undertaken to verify the effect of the forage to concentrate ratio of the diet on B-vitamin concentrations in ruminal contents. In Study I, eight primiparous and eight multiparous cows were used in a cross-over design, and concentrations of biotin, folates and vitamin B 12 were determined in ruminal fluid and plasma of cows fed a high-forage (HF; 58:42 forage to concentrate ratio; DM basis) or a low-forage (LF; 37:63 forage to concentrate ratio; DM basis) diet. In Study 2, six ruminally cannulated lactating cows were used in a cross-over design to evaluate the effects of forage to concentrate ratio (HF = 60:40; LF = 40:60; DM basis) on concentrations of seven B-vitamins in the particle-free fluid and in both liquid- and solid-associated bacteria. Results showed that B-vitamins were present mainly in the bacterial fractions of the ruminal content, while only limited amounts were found in the surrounding fluid. A change in the forage to concentrate ratio had a greater effect on vitamin concentration in the bacteria associated with the solid fraction than in those present in the liquid portion of the rumen. The most noticeable effects of a low forage diet were an increase in riboflavin, but a decrease in true vitamin B12 concentrations in solid-associated bacteria as well as a decrease in biotin concentration in particle-free fluid. In conclusion, it appears that ruminal B-vitamin concentration is altered by changes in the forage to concentrate ratio, which suggests that the supply of vitamins to dairy cows is influenced by diet composition.
No preview · Article · Sep 2005 · The Canadian veterinary journal. La revue veterinaire canadienne
[Show abstract][Hide abstract] ABSTRACT: Ruminal fluid was collected from dairy cows using three methods: (1) a stomach tube, or directly through the ruminal cannula with (2) a syringe screwed to a stainless tube covered by a fine metal mesh; or (3) a rubber tube connected to a vacuum pump. Fluid samples were either acidified to disrupt bacterial membranes or centrifuged to remove the bacterial fraction. B-vitamin concentrations were higher in the acidified than in the centrifuged fluid, while the collection method had only a limited effect. Results of this study strongly suggest that B-vitamin concentration in ruminal fluid is not a good indicator of their synthesis, and that the bacterial fractions should probably be considered.
No preview · Article · Sep 2005 · The Canadian veterinary journal. La revue veterinaire canadienne
[Show abstract][Hide abstract] ABSTRACT: Four lactating Holstein cows equipped with ruminal, duodenal, and ileal cannulas were used in 2 studies to evaluate the disappearance of supplementary B-vitamins before and from the small intestine. The cows were fed a total mixed ration with chromic oxide in 12 daily meals. Each study consisted of a control (no vitamin supplementation) and a treatment period (with vitamin supplementation). Amounts of vitamins (mg/d) supplemented in studies 1 and 2, respectively, were: thiamin: 300 and 10; riboflavin: 1600 and 2.0; niacin: 12,000 and 600; vitamin B6: 800 and 34; biotin: 20 and 0.02; folic acid: 2600 and 111; vitamin B12: 500 and 0.4. In study 1, vitamins were added to the feed 5 d before and during the 4-d collection period. In study 2, vitamins were infused postruminally 1 d before and during the 4-d collection period. Substantial disappearance before the duodenal cannula was noted in study 1 (67.8% thiamin, 99.3% riboflavin, 98.5% nicotinamide, 41.0% pyridoxine, 45.2% biotin, 97.0% folic acid, and 62.9% vitamin B12). Except for nicotinamide and folate, there was almost no disappearance of postruminally infused vitamins before the duodenal cannula (study 2), suggesting extensive ruminal destruction or use. Apparent intestinal absorption values differed greatly among vitamins, but the proportion of vitamins disappearing from the small intestine was not negatively influenced by supplementation. Except for riboflavin and niacin, absolute amounts disappearing from the small intestine were greater during the treatment than the control periods, suggesting that B-vitamin supply in dairy cows is increased by supplementation, although losses in the rumen are extensive.
No preview · Article · Jul 2005 · Journal of Dairy Science