Dietary supplementation of rumen-protected methionine decreases the nitrous oxide emissions of urine of beef cattle through decreasing urinary excretions of nitrogen and urea.

BACKGROUND: Two consecutive trials were carried out to study the effects of dietary supplementation of rumen-protected methionine (RPM) on nutrient digestibility, nitrogen (N) metabolism (Trial 1), and consequently the nitrous oxide (N2 O) emissions from urine in beef cattle (Trial 2). Eight 24-month-old castrated Simmental bulls with liveweights of 494 ± 28 kg, and four levels of dietary supplementation of RPM at 0, 10, 20, and 30 g head-1 d-1 , were allocated in a replicated 4 × 4 Latin square for Trial 1 and the N2 O emissions from the urine samples collected in Trial 1 were measured using a static incubation technique in Trial 2. RESULTS: Supplementation of RPM at 0, 10, 20, and 30 g head-1 d-1 to a basal ration deficient in methionine (Met) did not affect the apparent digestibility of dry matter, organic matter, neutral detergent fiber, or acid detergent fiber (P > 0.05), but decreased the urinary excretions of total N (P < 0.05) and urea (P < 0.001), increased the ratio of N retention / digested N (P < 0.05) in beef cattle, and decreased the estimated cattle urine N2 O-N emissions by 19.5%, 23.4%, and 32.6%, respectively (P < 0.001). CONCLUSION: Supplementation of RPM to Met-deficient rations was effective in improving the utilization rate of dietary N and decreasing the N2 O emissions from urine in beef cattle. © 2019 Society of Chemical Industry.

Validating and optimizing spot sampling of urine to estimate urine output with creatinine as a marker in dairy cows.

An experiment was conducted to validate and optimize the procedure of spot urine sampling with urinary creatinine as a marker to estimate urine outputs of dairy cows. Twelve lactating cows were used in a randomized complete block design. Cows were grouped and randomly assigned to 2 experimental diets: a corn silage-based diet and an alfalfa silage-based diet with supplemental potassium. The experiment lasted for 21 d and total collection (TC) of urine was conducted for the last 3 d. Twelve spot samples of urine from individual cows were collected over a 3-d period during TC to represent every 2-h sampling in a 24-h cycle. Creatinine excretion rate (mg/kg of body weight per d) was variable among cows from 16.7 to 34.5 with an average of 27.3. Creatinine concentrations of spot samples within cow were averaged to simulate urine samples obtained from various spot sampling frequencies (equally spaced 12, 6, 4, and 2 time points starting at feeding: 12TP, 6TP, 4TP, and 2TP, respectively). Large diurnal variation of urinary creatinine concentration was observed within cow. Creatinine concentration was greater (75 vs. 65 mg/dL) for 12TP compared with TC, resulting in underestimating (29.8 vs. 32.6 kg/d) urine outputs. When compared among 12TP, 6TP, 4TP, and 2TP, creatinine concentrations were different and urine outputs tended to be different for 2TP compared with 12TP, 6TP, and 4TP. In addition, despite underestimation of urine output, a regression analysis indicated strong linear relationships between 12TP, 6TP, or 4TP and TC, suggesting that this technique can successfully identify the differences in urine outputs altered by dietary treatments. However, 4TP failed to detect statistical differences in urine outputs between a corn silage-based diet and the alfalfa silage-based diet with supplemental potassium, indicating that a spot urine sampling frequency of at least 6 was required to identify dietary effects on urine outputs. According to the pattern of diurnal changes in urinary creatinine concentration, a spot sample at about 10 h after feeding may have potential to obtain a urine sample that is more representative (i.e., creatinine concentration) of TC urine compared with urine from multiple sampling frequencies. Overall, urinary creatinine as a marker with spot sampling of urine underestimated urine output. However, 12TP and 6TP were successful in identifying changes in urine outputs by dietary treatments.

Evaluation of creatinine as a urine marker and factors affecting urinary excretion of magnesium by dairy cows.

Nutrient balance studies require measuring urine volume, and urinary excretion can be used to assess Mg bioavailability. A less laborious method than total collection of urine could make balance studies more feasible and expand the utility of using urinary Mg as an index of bioavailability, but the method needs to be accurate and sensitive. Sampling interval can affect accuracy because excretion must be at steady state. Two experiments were conducted to (1) determine whether urinary creatinine could be used to accurately estimate urinary output of nutrients markedly excreted via urine (N, K, Na, S, and Mg; experiment 1) and (2) determine the appropriate sampling schedule to evaluate Mg excretion after abrupt diet changes (experiment 2). Experiment 1 was originally designed to evaluate the interaction of monensin [0 vs. 14 mg of monensin/kg of dry matter (DM)] and Mg source (MgO vs. MgSO4; total diet Mg: 0.36% of DM) under antagonism from increased dietary K (2.11% of DM) on urinary Mg excretion. Experiment 2 evaluated the interaction of Mg concentration (basal vs. supplemental MgO; total diet Mg: 0.20 vs. 0.42% of DM) and K (basal vs. supplemental K2CO3; total diet K: 1.60 vs. 2.57% of DM) on urinary Mg excretion over time. Using 4-d composite samples from total collection of urine (n = 34 cow-periods), the average daily excretion of creatinine was similar to previous estimates (29.0 ± 1.16 mg of creatinine/kg of body weight) but was variable among cows (root mean squared error = 2,980 mg/d; 14% of mean). Treatment-average estimated excretion of urine and urinary N, K, Na, S, and Mg were similar to actual values; however, differences between actual and estimated values could be substantial for individual cows. Using the mean creatinine excretion per kilogram of body weight for all cows to estimate urine eliminates the lack of fit variance resulting in artificially low within-treatment variation for estimated urine volume. The standard error of the mean for estimated urine volume was 23% less (1.93 vs. 2.51) than that for actual urine production. This inflated the type I error rate, and, consequently, statistical inferences on N and K excretion differed when urine output was estimated rather than measured. The standard error of the mean for excretion of Mg calculated with actual or estimated urine production were almost identical (0.92 vs. 0.97); however, similar standard error of the mean was likely caused by differences in the covariance of urinary Mg concentration with estimated or actual urine output. Based on spot sampling (experiment 2), urinary Mg reached steady state by 2 d following an increase in dietary K regardless of Mg level, whereas excretion of urinary Mg following an increase in dietary Mg continued to increase through 7 d. Estimating nutrient excretion with urinary creatinine and body weight on average is accurate, but variance is likely underestimated. Knowing the time course of urinary Mg excretion will improve the value of using urinary Mg concentration to assess diet adequacy or Mg bioavailability.

A nationwide survey of pathogenic leptospires in urine of cattle and buffaloes by Loop-mediated isothermal amplification (LAMP) method in Thailand, 2011-2013.

Leptospirosis is a worldwide distributed zoonosis which has long been endemic in Thailand. Cattle and buffaloes are important livestock species that live in close contact with humans, especially in rural areas. These animals may, therefore, act as long-term carriers of leptospirosis for humans and other livestock species. The present study employed loop-mediated isothermal amplification (LAMP) method to detect pathogenic leptospiral 16S rDNA in the urine of cattle and buffaloes for assessing associations between uroprevalence and species, sex, age and spatial distribution. A total of 3,657 urine samples were collected for laboratory diagnosis, and 312 of which turned positive to the test (true prevalence 5.90%; 95% CI 4.98-6.91). The highest true uroprevalence was found in lower northern region at 19.80% (95% CI 15.83-24.32) followed by upper and lower northeastern regions at 15.22% and 6.25%, respectively. However, the highest true uroprevalence in beef cattle, the majority of cattle in Thailand, was recorded in northeastern region which is the endemic area of human leptospirosis. The uroprevalence was not statistically different among species and types of examined animals. Male animals were over twice more likely to be infected compared to females. Excluding animals younger than one year of age due to small sample size, the uroprevalence upraised with increasing age. A collaborative investigation between veterinary and public health sectors is required to holistically explore the link between leptospirosis in humans and livestock, especially in high prevalent areas.

Effects of a dietary sweetener on growth performance and health of stressed beef calves and on diet digestibility and plasma and urinary metabolite concentrations of healthy calves.

Two experiments were conducted to explore the effects of a sodium saccharin-based dietary sweetener (Sucram) on growth performance, health, and physiological responses of feedlot steers. In Exp. 1, 173 newly-received male calves purchased from auction barns were fed 0, 100, 200, or 300 g of Sucram/t of DM over 56 d. Overall, ADG and G:F (P > 0.10) were not different among treatments, but steers receiving 200 g Sucram/t displayed numerically greater ADG (23%). In addition, DMI was 17% greater for steers receiving 200 g of Sucram/t compared to steers fed the control diet (cubic effect, P = 0.09). The morbidity rate for respiratory disease did not differ (P > 0.50) among treatments. In Exp. 2, 15 steers (initial BW = 261 ± 28 kg) were used to evaluate the effects of Sucram on apparent total tract digestibility, plasma metabolite concentrations, and urine monoamine metabolite concentrations. Treatments consisted of ad libitum access to a 60% concentrate diet (Control), ad libitum access to Control + 200 g of Sucram/t of DM (Adlib), and Control + 200 g of Sucram/t of DM with feed intake paired to the Control (Paired). By design, steer DMI during the metabolism period did not differ (P = 0.34) between Paired and Control, but DMI tended (P = 0.14) to be 8.2% greater for Adlib than for Control. Treatments did not alter (P > 0.17) apparent total tract nutrient digestibility. Postprandial plasma citrulline concentration was lower (P = 0.03) for Adlib than for Control and tended to be lower (P = 0.13) for Paired than for Control. Plasma homocysteine concentration was reduced (P < 0.03) by feeding Sucram. Urinary concentrations of ethylmalonic acid, vanillymandelic acid, and 5-hydroxyindolacetic acid were greater (P < 0.06) for Adlib than for Control; Paired steers had a greater (P = 0.02) urine vanillymandelic acid concentration than Control steers and tended (P < 0.12) to have a greater urinary concentration of ethylmalonic and 5-hydroxyindolacetic acid than Control steers. Serum insulin was greater for Adlib than for Control steers (P = 0.04) and tended to be greater for Paired than for Control steers (P = 0.14), but serum prolactin area did not differ (P > 0.22) among treatments. Supplementation with Sucram may increase feed intake by newly-received, stressed feedlot calves. Saccharin supplementation reduced plasma homocysteine and increased urinary excretion of vanillymandelic acid, suggesting an improved activity of the dopamine reward system.

Watering cattle (young bulls) with brackish water--a hazard due to its salt content?

OBJECTIVE: The aim of this experimental study was primarily to test the effects and reactions of cattle offered salty water as the only source of drinking water. MATERIAL AND METHODS: Mineral balance studies were carried out on three bull, continuously fed a ration based on hay, hay cobs, barley, soybean meal and a vitamin/mineral supplement. The salt content of the drinking water varied between the trials (trials I/II/III: 0.10/5.00/10.0 g/l; town water supplemented by different amounts of an additive containing 95.4% sodium chloride and 4.6% potassium chloride). RESULTS: Rising salt concentration of the drinking water led to significantly higher sodium, potassium and chloride intake (sodium: trial I/II/III = 5.42/59.5/ 157 g/day; potassium: trials I/II/III = 108/117/121 g/day; chloride: trials I/II/III = 22.8/112/266 g/day) mainly caused by a significantly higher water intake (trials I/II/III: 21.8 ± 2.03/30.4 ± 3.08/41.5 ± 5.89 kg/day). Amounts of urine increased significantly (trials I/II/III: 3.99 ± 0.46/ 9.66 ± 1.34/20.2 ± 3.14 kg/day). The concentrations of minerals in the urine (sodium: trials I/II/III = 123/3729/6705 mg/kg; potassium: trials I/II/III = 17345/9996/ 5496 mg/kg; chloride: trials I/II/III = 2020/ 9672/11870 mg/kg) and faeces (sodium: trials I/II/III = 1299/6544/ 7653 mg/kg; potassium: trials I/II/III = 6343/3719/3490 mg/kg; chloride: trials I/II/III = 3851/4580/4693 mg/kg) also changed significantly over time. Serum values of sodium tended to decrease (trials I/II/III: 142/137/137 mmol/l) within the physiological range, whereas those of chloride increased (trials I/II/III: 91.5/95.6/97.5 mmol/l) at higher salt concentrations in drinking water. The haematocrit, pH-value as well as urea content in blood were not affected by the higher salt intake. In balance trial III (highest salt load: 10.0 g/l), sodium intake of the bulls reached 0.57 ± 0.03 g/kg BW (~22.1 ± 0.9 g sodium/kg dry matter feed). CONCLUSION AND CLINICAL RELEVANCE: An increase of salinity in drinking water up to 10 g/l--with otherwise harmless water quality--had no measurable negative effects on animal health in the investigation period and subsequent periods (total of 58 days with more than 5.00 g of salt per litre drinking water).

Nutritional evaluation of wheat straw treated with Crinipellis sp. in Sahiwal calves.

Wheat straw was subjected to solid-state fermentation (SSF) with lignolytic white-rot fungus (WRF) Crinipellis sp. for 5 days to improve the nutritive value and digestibility. The fungal treatment caused a significant (P < 0.05) decrease in cell wall constituents viz., neutral detergent fiber (NDF), acid detergent fiber (ADF), hemicellulose, lignin, and cellulose to the extent of 10.4, 11.2, 8.7, 8.7, and 12.1 %, respectively, with increase (P < 0.05) in crude protein (CP) (51.6%) and ash (25.8%) contents in fungal treated wheat straw (FT-WS) than untreated wheat straw (UT-WS). Further, in vitro gas production, in vitro true dry matter digestibility and in vitro true organic matter digestibility at 48 h, metabolizable energy (ME) content, microbial biomass production, and short-chain fatty acids synthesis were significantly (P < 0.05) higher in FT-WS. In vivo feeding trial in 10 Sahiwal calves (8-12 months) comprised of (1) control group (T1) fed with ad libitum chopped UT-WS and (2) treatment group (T2) offered with ad libitum chopped FT-WS, in addition to supplementation of groundnut cake and green berseem (Trifolium alexandrium) forage to both groups. Digestibility of nutrients for dry matter (DM), organic matter, CP, NDF, ADF, hemicellulose, cellulose, and total carbohydrates were significantly (P < 0.05) higher in T2 compared to T1. Moreover, daily DM (P < 0.05), digestible crude protein (P < 0.01), and ME intakes were also higher (P < 0.05) in group T2 with higher (P < 0.05) nitrogen (N) retention, which resulted in significantly (P < 0.05) higher average daily gain in body weight (135 vs. 102 g/day). It was concluded that SSF with WRF Crinipellis sp. holds potential in upgrading the nutritional worth of wheat straw for feeding growing calves.

Influence of feeding increasing levels of dry corn distillers grains plus solubles in whole corn grain-based finishing diets on total tract digestion, nutrient balance, and excretion in beef steers.

Four crossbred steers (average BW = 478 ± 33 kg) were used in a 4 × 4 Latin square design to determine the effects of dietary concentration of dry corn distillers grains plus solubles (DDGS) in whole corn-based finishing diets on total tract digestion and nutrient balance and excretion. The DDGS were fed at 0% (control), 16.7%, 33.3%, and 50% of dietary DM. All diets contained 10% (DM basis) alfalfa/grass haylage and were formulated to meet or exceed the estimated requirements for CP. Steers were fed the experimental diets ad libitum for a 14-d adaptation period followed by a 5-d period for fecal and urine collection. Increasing concentration of DDGS in diets from 0 to 50% of DM linearly decreased (P < 0.05) total tract DM and starch digestibility (from 77.8 to 72.9%, and 89.2 to 81.5%, respectively). Daily N and P intakes linearly increased (P = 0.06 and P = 0.01, respectively) with increasing DDGS concentration. Fecal and urinary N, P, S, Mg, and K excretion linearly increased (P < 0.05) with increasing DDGS concentration; however, Se and Na excretion did not differ (P > 0.38) among treatments. Retention (g/d; intake minus urinary and fecal excretion) of N did not differ (P > 0.16) among treatments. Retention of P tended (P = 0.07) to linearly increase and retention of S (g/d) linearly increased (P = 0.004), with increasing DDGS concentration. There were no effects (P > 0.16) of dietary treatment on digestion and retention of Se, Mg, K, and Na. Plasma P and S concentrations increased (P = 0.03 and 0.01, respectively) with increasing DDGS concentration. These data indicate that feeding DDGS up to 50% of dietary DM in whole corn grain-based finishing diets does not have a negative effect on nutrient retention but decreases digestibility. Total excretion of N, P, Ca, Mg, S, and K increased as DDGS concentration increased.

Comparative study on the effect of chemicals on Alternaria blight in Indian mustard--a multi-location study in India.

High severity of Altemaria blight disease is a major constraint in production of rapeseed-mustard in India. The aim of this study was to investigate the suppressive potential of chemicals viz., zinc sulphate, borax, sulphur, potash and calcium sulphate, aqueous extracts viz., Eucalyptus globosus (50 g l-1) leaf extract and garlic (Allium sativum) bulb (20 g l-1) extract, cow urine and bio-agents Trichoderma harzianum, Pseudomonas fluorescence in comparison with the recommended chemical fungicide (mancozeb), against foliar disease Alternaria blight of Indian mustard [Brassica juncea (L.) Czern. and Coss] under five different geographical locations of India. Mancozeb recorded the lowest mean severity (leaf: 33.1%; pod: 26.3%) of Alternaria blight with efficacy of garlic bulb extract alone (leaf = 34.4%; pod = 27.3%) or in combination with cow urine (leaf = 34.2%; pod = 28.6%) being statistically at par with the recommended chemical fungicide. Chemicals also proved effective in reducing Alternaria blight severity on leaves and pods of Indian mustard (leaf = 36.3-37.9%; pod = 27.5-30.1%). The effective treatments besides providing significant reduction in disease severity also enabled increase in dry seed yield of the crop (mancozeb = 2052 kg ha-1; garlic = 2006 kg ha-1; control = 1561 kg ha-1).

Periparturient effects of feeding a low dietary cation-anion difference diet on acid-base, calcium, and phosphorus homeostasis and on intravenous glucose tolerance test in high-producing dairy cows.

Feeding rations with low dietary cation-anion difference (DCAD) to dairy cows during late gestation is a common strategy to prevent periparturient hypocalcemia. Although the efficacy of low-DCAD rations in reducing the incidence of clinical hypocalcemia is well documented, potentially deleterious effects have not been explored in detail. The objective of the study presented here was to determine the effect of fully compensated metabolic acidosis on calcium and phosphorus homeostasis, insulin responsiveness, and insulin sensitivity as well as on protein metabolism. Twenty multiparous Holstein-Friesian dairy cows were assigned to 1 of 2 treatment groups and fed a low-DCAD ration (DCAD = -9 mEq/100g, group L) or a control ration (DCAD = +11 mEq/100g, group C) for the last 3 wk before the expected calving date. Blood and urine samples were obtained periodically between 14 d before to 14 d after calving. Intravenous glucose tolerance tests and 24-h volumetric urine collection were conducted before calving as well as 7 and 14 d postpartum. Cows fed the low-DCAD ration had lower urine pH and higher net acid excretion, but unchanged blood pH and bicarbonate concentration before calving. Protein-corrected plasma Ca concentration 1 d postpartum was higher in cows on the low-DCAD diet when compared with control animals. Urinary Ca and P excretion was positively associated with urine net acid excretion and negatively associated with urine pH. Whereas metabolic acidosis resulted in a 6-fold increase in urinary Ca excretion, the effect on renal P excretion was negligible. A more pronounced decline of plasma protein and globulin concentration in the periparturient period was observed in cows on the low-DCAD diets resulting in significantly lower total protein and globulin concentrations after calving in cows on low-DCAD diets. Intravenous glucose tolerance tests conducted before and after calving did not reveal group differences in insulin response or insulin sensitivity. Our results indicate that fully compensated metabolic acidosis increased the Ca flux resulting in increased urinary calcium excretion before calving and increased plasma Ca concentration on the day after calving, whereas the effect on P homeostasis was unlikely to be clinically relevant. The clinical relevance of the effect of metabolic acidosis on the plasma protein and globulin concentration is unclear but warrants further investigation.

Measurement of urinary zearalenone concentrations for monitoring natural feed contamination in cattle herds: On-farm trials.

The aims of the present study were to investigate the efficacy of measuring bovine urinary zearalenone (ZEN) concentrations by using a commercially available ELISA method in cattle kept under different feeding conditions to monitor the natural contamination of feeds at the farm level, and to investigate the effects of supplementation of a mycotoxin adsorbent (MA) product in the feed based on urinary ZEN concentration. First, Japanese Black cattle herds kept for breeding (4 herds) and fattening (4 herds) purposes were provided with similar feeding conditions. Then, urinary samples from 5 cows in each herd were collected and analyzed. Second, dairy cows from 1 herd fed with total mixed rations (TMR) were selected. After thorough mixing of the MA (40 g/d) with TMR, the supplemented TMR was fed according to the following schedule: with MA for 2 wk, without MA for 3 wk; then with MA for 2 wk and without MA for 6 wk. Urine samples were collected from cows (n = 6 to 7) and examined before and after each interval. Zearalenone concentrations were measured by the ELISA and liquid chromatography-tandem mass spectrometry methods. The concentration of ZEN and its metabolites was expressed after creatinine (Crea) correction [ZEN or metabolites (pg/mL)/Crea (mg/dL); pg/mg of Crea]. In the first experiment, the urinary concentrations of ZEN and its metabolites were variable in all herds, and significant differences were observed between herds. In 1 fattening herd, in particular, urinary ZEN concentrations were greater (P < 0.001) than in the other 3 herds. This might reflect significant natural ZEN contamination of the feed at the farm level. In Exp. 2, urinary ZEN concentrations displayed peculiar trends after supplementation with MA. After 2 wk of supplementation, a significant decrease of ZEN (P < 0.05) was observed. Zearalenone concentrations remained at a reduced amount during 3 wk without MA supplementation and 2 wk with MA supplementation. When MA was not added to the feed for the next 6 wk, the concentrations increased to the original quantity. These findings indicate the usefulness of measuring concentrations of urinary ZEN and its metabolites not only for monitoring the natural ZEN contamination of cattle feed at the farm level but also for in vivo evaluation of MA function after supplementing feeds with MA.

Effects of anionic salts supplementation on blood pH and mineral status, energy metabolism, reproduction and production in transition dairy cows.

The objectives of this study were to determine the effects of a pre-partum diet with lower than recommended (DCAD=-82 mEq/kg of dietary DM) amounts of anionic salts on metabolism, health, reproductive performance and milk production in dairy cows. Sixty Holstein multiparous cows were enrolled 21 days prior to expected calving date. The animals were randomly assigned to receive one of two rations: 30 cows received anionic ration [-82 mEq (NA+K-Cl-S)/kg of DM] for 21 d to parturition and the other group (n=30) were fed a usual dry period ration (+192 mEq/kg of DM). Serum samples obtained at days -21, +3 and +21 relative to calving were analyzed for beta-hydroxybutyrate (BHBA), non-esterified fatty acids (NEFA), glucose, calcium (Ca), inorganic phosphorus, magnesium, chloride, sodium, potassium, cholesterol, urea, creatinine, total protein, albumin, and aspartate aminotransferase (AST). Urine pH declined from 8.4 at 21 d before calving (pre-treatment) to 6.2 at day 7 pre-partum in the treatment group. Repeated-measure mixed model analysis indicated that the concentrations of Ca were significantly increased and creatinine, and AST were significantly decreased by lowering DCAD. The concentrations of BHBA, NEFA and glucose were not affected by treatment. The incidence of milk fever and culling were 5 and 11 times higher in the control group in comparison with the treatment group, respectively. The intervals from calving to first breeding and to pregnancy were not influenced by treatment. There was no group effect on average daily milk yield or fat percentage.

Magnesium absorption by lactating dairy cows on a grass silage-based diet supplied with different potassium and magnesium levels.

The objective of the present study was to investigate the interactions of dietary K intake typical for forage-based diets on Mg balance in lactating dairy cows. Six lactating multiparous cows of the Swedish Red and White breed in midlactation were used. Two concentrations of Mg (1.9 and 4.3 g/kg of dry matter) and 3 concentrations of K (19, 28, and 37 g of K/kg of dry matter) were obtained by adding appropriate amounts of MgO and KHCO(3) to the diet. The experimental setup was a 6 x 6 Latin square design with a 2 x 3 factorial arrangement of treatments. Each experimental period lasted 14 d (9-d treatment adaptation period and 5-d data collection). There was no effect of Mg or K dietary supplementation on milk yield. Supplementing the ration with K did not significantly affect the Mg apparent absorption, urinary Mg excretion, or plasma Mg concentration. The Mg balance, estimated as the Mg losses in milk and urine, was positively related to Mg intake but not affected by K intake. The amount of apparently digested Mg was related to the Mg balance. The apparent digestibility ranged from 0.12 to 0.24 with no effect of mineral supplementation. There was a significant curvilinear relationship between plasma Mg and urinary Mg excretion, with a more marked increase in urinary Mg excretion at higher plasma levels of Mg.

The effect of vitamin C supplementation on plasma concentration and urinary excretion of vitamin C in cattle.

We investigated the plasma concentration and urinary excretion of vitamin C in cows supplemented with vitamin C. Five cows (mean BW = 597 kg) were allocated to a 5 x 5 Latin square design and supplemented with a vitamin C preparation coated with hydrogenated soybean oil at 0, 10, 20, 40, or 60 mg of vitamin C per kg of BW per day for 9 d. Plasma and urine samples were collected for measuring vitamin C concentration. Urinary excretion of vitamin C was expressed as the ratio of vitamin C to creatinine. Plasma vitamin C concentration and urinary vitamin C excretion increased quadratically as dietary vitamin C increased (P < 0.001); that is, the lowest dose affected neither plasma vitamin C concentration nor urinary vitamin C excretion but the plasma vitamin C concentration and urinary vitamin C excretion increased (P < 0.05) with increasing supplementation of vitamin C at greater doses. This suggests that plasma vitamin C concentration affects urinary excretion of vitamin C in cattle and that plasma vitamin C concentration exceeded the renal threshold for vitamin C in the cows receiving vitamin C at 20 mg/kg of BW per day. Furthermore, increased urinary excretion of vitamin C appears to limit plasma vitamin C concentration in response to vitamin C intake. The daily excretion of vitamin C was estimated by the reported value of daily creatinine excretion, indicating that the daily amount of vitamin C excreted into urine was more than half of supplied vitamin C. Therefore, a large part of supplied vitamin C probably escapes ruminal degradation and is absorbed but excreted into urine.

Effects of 25-hydroxyvitamin D3 and manipulated dietary cation-anion difference on the tenderness of beef from cull native Korean cows.

In this study, we characterized the effects of 25-hydroxyvitamin D3 (25-OH D3) and manipulated dietary cation-anion difference (DCAD) on the performance, urine pH, serum constituents, carcass traits, tissue residual vitamin D and its metabolites, beef tenderness, and mRNA and protein concentrations of Ca-dependent proteinases in LM using 24 cull native Korean cows. The cows were divided into 3 groups of 8: control, 25-OH D3 supplemented (25-OH D3), and manipulated DCAD plus 25-OH D3 supplemented (DCAD+25-OH D3). Cows receiving 25-OH D3 or DCAD+25-OH D3 were dosed with 125 mg of 25-OH D3 6 d before slaughter. The manipulated DCAD (-10 mEq/100 g of DM) diet was fed from 20 to 6 d (14 d) before slaughter. The DCAD+25-OH D3 treatment decreased urine pH and increased serum Ca concentrations. Although the vitamin D concentrations in LM, liver, and kidney were not affected by 25-OH D3 or DCAD+25-OH D3, muscle tissue 25-OH D3 concentrations were increased by both regimens. Serum 25-OH D3 concentrations were increased by 25-OH D3 supplementation, and the increase was even greater for DCAD+25-OH D3. The same pattern was observed for serum 1,25- (OH)2 D3. However, the LM concentration of 1,25-(OH)2 D3 was less for DCAD+25-OH D3 than for control. Although Ca concentrations of LM increased numerically in response to 25-OH D3 supplementation, no statistical differences in Warner-Bratzler shear force or sensory traits of LM were detected. The LM of cows receiving 25-OH D3 with or without manipulated DCAD had greater concentrations of mu-calpain and m-calpain mRNA, whereas the reverse was observed for calpastatin mRNA. Expression of mu-calpain protein was increased relative to control by DCAD+25-OH D3. The amount of 25-OH D3 and manipulated DCAD administered to cull native Korean cows was insufficient to improve tenderness of beef by increasing muscle Ca concentration. However, DCAD+25-OH D3 induced greater expressions of mu-calpain protein as well as mRNA.

Effect of glycine and vitamin supplementation on sulphur amino acid utilization by growing cattle.

Effects of glycine (Gly) and B-vitamins on sulphur amino acid (AA) utilization were studied in growing steers maintained under conditions where methionine (Met) was first limiting. Conditions were generated by limit feeding a diet low in ruminally non-degraded protein and abomasally infusing an AA mixture limiting in Met. Retained N tended (p = 0.07) to improve when steers received 10 mg folate, 10 mg vitamin B6, and 0.10 mg vitamin B12 daily. Hepatic vitamin B12 (p = 0.08) and folate (p = 0.05) concentrations increased with vitamin supplementation. In another trial, factorial treatments were 2 or 5 g/day L-Met and 0 or 50 g/day Gly infused abomasally. Retained N increased (p < 0.05) in response to Met, and responses were numerically larger in the presence of supplemental Gly. In a different trial, factorial treatments were 0 or 2.4 g/day L-cysteine (Cys) and 0 or 40 g/day Gly. Retained N was not affected by Cys in the absence of Gly, but was increased by Cys when Gly was supplemented (interaction, p = 0.01). B-vitamin status may affect sparing of Met by Cys. Supplemental Gly improved responses to supplemental Met and Cys.

Aspects of physiological effects of sodium zeolite A supplementation in dry, non-pregnant dairy cows fed grass silage.

The objective of the present study was to monitor serum and urine biochemical changes in dairy cows during and after oral administration of a synthetic sodium aluminium-silicate (zeolite A). A prospective longitudinal study involving four non-pregnant and non-lactating cows was chosen. Cows were randomly allocated to either a control or experimental group. The period of observation was three weeks. During the first week (period 1) cows were maintained on basic ration for the purpose of recording baseline values. During the second week (period 2) control cows were fed a basic diet (grass silage), while cows in the experimental group were fed the basic diet and supplemented with 1 kg zeolite pellets once daily. During the third week (period 3) both groups were fed the basic ration only and observed for any persistent effects after zeolite withdraw. Daily sampling included blood and urine. Selected physiological parameters were compared between groups during period 2 and 3, whereas mean values from period 1, 2 and 3 were compared within the groups. Zeolite supplementation revealed a significant influence on calcium homeostasis. A slight decrease in serum Ca and in renal excretion of calcium was observed in the experimental group at initiation of supplementation, whereas an increment in these parameters was recorded after withdrawal of zeolite supplementation. It is assumed, that zeolite caused a reduction in the availability of dietary calcium during supplementation, which possibly elicited an activation of calcium mobilisation. The influence of zeolite on calcium homeostasis was not evident from monitoring serum concentration of calcium regulating hormones (PTH, 1,25(OH)2D3, 25(OH)VitD) or renal excretion of markers of bone resorption. Enhanced active intestinal calcium absorption and bone resorption was therefore considered insignificant in the calcium mobilisation under the conditions of this experiment. The origin of the increased amount of Ca, which was observed in serum and urine after zeolite withdraw, is at present unknown, but it is suggested, that the readily mobilized Ca-pool in bone was a contributing factor. An effect of zeolite on phosphate and magnesium homeostasis in the experimental group was evidenced from the values of serum concentration and fractional excretion, which during supplementation were significant lower than in the control group. The influence of zeolite on phosphorus and magnesium is presumed to result from a combination of interference of zeolite with intestinal absorption and a marginal dietary supplementation of these minerals.

Evaluation of biochemical methods for estimating the sodium intake of dairy cows.

Samples of blood and urine were taken from 334 dairy cows in 29 herds, and the concentrations of sodium and potassium were measured in the serum and urine. The herds were split into five groups according to the amount of supplementary salt they were given: three groups given 10 to 20, 30 to 50 or 70 to 100 g salt per day, and two groups fed an ad libitum supply, given either in bowls or in the form of salt blocks, which were replaced either regularly or irregularly. The groups which received 70 to 100 g of salt daily or were supplied regularly ad libitum had significantly higher urinary sodium concentrations than the other groups. The group receiving 10 to 20 g a day had a significantly higher ratio of potassium:sodium in their urine than all the other groups, in which the ratio decreased as the level of supplementary salt increased. There were wider differences between the groups in terms of the urinary potassium:sodium ratio than in terms of the urinary sodium concentration but less variability within each group.

Effect of dietary or abomasal supplementation of exogenous polysaccharide-degrading enzymes on rumen fermentation and nutrient digestibility.

The effect of site of supplementation of a mixture of two crude preparations (Enzyme C and Enzyme X) of exogenous polysaccharide-degrading enzymes (EPDE) was studied in vivo using four ruminally and duodenally cannulated heifers (Exp. 1). The treatments were as follows: control (no EPDE), EPDE supplied through the diet (EF, 47.0 g/d), and EPDE infused continuously into the abomasum (EA, 41.6 g/d). Enzyme treatment increased the concentration of soluble reducing sugars (P < .05) and decreased NDF content (P < .05) in the treated feed, but this did not increase the rate or extent of in sacco disappearance of DM from the feed. Compared with control, ruminal fermentation was not affected by EF, but abomasal infusion increased (P < .05) rumen ammonia levels and shifted ruminal VFA patterns. Ruminal carboxymethylcellulase (CMCase) and xylanase activities were not affected by treatment. Abomasal infusion increased (P < .05) duodenal xylanase activity as compared with control and EF, but apparent digestion of DM, NDF, and CP were not affected by treatment. Negligible levels of CMCase and amylase reached the duodenum. During an in vitro experiment (Exp. 2), abomasal stability of the two EPDE was studied over a range of pH from 3.39 to .85, with or without pepsin. Carboxymethylcellulase activity (in Enzymes C and X) and beta-glucanase activity (in Enzyme C) were largely unstable against pepsin proteolysis (P < .001) and low pH (P < .001). Xylanase and amylase activities were resistant to pepsin but irreversibly inactivated at low pH. These two experiments showed that abomasal supplementation of EPDE did not successfully supply cellulases and amylases to the intestine, due partially to their limited resistance to low pH and pepsin proteolysis. Although EPDE significantly increased the level of xylanase activity at the duodenum, this did not significantly improve total tract digestion.

Urinary iodine level as an intake indicator in dairy cows.

Urinary iodine concentrations were determined in 672 dairy cows of 22 herds. Less than 20 micrograms per L, 20 to 50 micrograms per L, 50 to 100 micrograms per L and more than 100 micrograms per L were found in 27.5, 24.6, 16.8, and 31.3% of the cows, respectively. In terms of the ICCIDD grading, moderate iodine deficiency was recorded in 68.9% and normal iodine intake in 31.3% of the cows. The mean urinary iodine concentrations were 94.8 micrograms per L at the peak of the lactation period (n = 300), 82.3 micrograms per L immediately before drying off (n = 122), 92.5 micrograms per L in the cows fed summer rations (n = 267), and 79.2 micrograms per L in those fed winter rations (n = 405). The differences in mean values were nonsignificant. Urinary iodine concentrations were examined in the herd LOS in cows fed iodine-supplemented (LOS E) or nonsupplemented (LOS C) rations. Mean concentrations were 316.2 micrograms per L for LOS E (n = 46) and 52.3 micrograms per L for LOS C (n = 41). The difference was highly significant (P < 0.01). The status of the group LOS C was classified as a medium iodine deficiency. The mean iodine concentrations at the peak of the lactation period and immediately before drying off were also significantly higher (P < 0.01) in this group. The supplementation of iodine resulted in an increase of urinary iodine concentration and, in terms of ICCIDD, the increase of iodine intake to the normal range. Normal intake and moderate, medium and serious deficits were found in three, two, one, and four herds, respectively. Special attention should be paid to herds showing higher grades of iodine deficiency.