Concentration of ammonia in the urine of dairy cows given green feed rations and winter feed rations

The concentration of ammonia in urine at a known level of energy yielding nutrients offered in feed rations was determined in 987 dairy cows in four summer feeding seasons and 1420 cows in three winter feeding seasons. The long-term average ammonia levels in urine showed no significant variation with the two types of feed rations. Different feed rations in the feeding seasons had no significant influence on ammonia concentration in the urine of lactating cows. On a long term-average as well as in the overwhelming majority of the winter and summer feeding seasons, high-pregnant cows had significantly higher ammonia contents in urine than the cows in the first and second lactation stage. At feeding rations complying with Czechoslovak Standard CSN 46 7070 the content of ammonia in the urine of lactating cows was lower than the recorded long-time averages and averages for individual stages; on the other hand, in high-pregnant cows the ammonia level was higher in both types of feed rations and the difference from lactating cows increased 3.25 times. This suggests that neither do the feed rations currently used in practice nor those strictly adhering to the Czechoslovak Standard meet the biological demand of high-pregnant cows and often lead to the injury of hepatal parenchyma. Ammonia concentration of 11.7 to 58.7 mmol per litre of urine is considered as a tolerable limit.     

Heifer rearing conditions affect length of productive life in Swedish dairy cows

Associations between rearing conditions and the risk of culling in dairy cows were studied by survival analysis. Data were collected from 1039 Swedish Red cows, 1029 Swedish Holsteins, and 56 cows of other milk or cross-breeds, representing all female animals born in 109 Swedish herds during 1998. Length of productive life was defined as the number of days from 1st calving to culling. The applied Weibull proportional hazards model included time-independent effects of breed, housing from 3 to 7 months of age, number of housing changes before calving, grazing before 1st calving, herd median age at 1st calving, age at 1st calving, cow housing, herd lactational incidence risk of veterinary-reported clinical mastitis, and the random effect of herd. Time-dependent effects were year, month, the interaction year by month, parity, number of breedings, pregnancy status, the interaction parity by pregnancy status, herd mean milk-production level, relative milk yield within breed-parity, and veterinary-reported clinical mastitis. The lactation was divided into six stages in which pregnancy status was assumed to be known by the farmer and culling could occur. Median productive life time in culled cows was 780 d and 14% of the records were censored due to terminated data collection. An individual calving age of 28.2–30.9 months was associated with the highest culling risk, 1.2-fold higher than calving at ≤25.3 months, whereas the risk decreased almost linearly with a higher herd median age at 1st calving. Housing in slatted pens with >7 calves from 3 to 7 months was associated with a 1.7-fold increase in risk, relative to litter pens. If a cow had changed housing system 4 times before 1st calving it increased the risk of culling 1.4 times, relative to two housing changes. These results show that rearing factors affect the productive life time of dairy cows in Swedish family operations.     

Cholic acid levels in the serum of dairy cows with metabolically-caused liver diseases

Three groups of freshly calved dairy cows suffering from fatty liver syndrome of different stages were examined for serum cholic acid (SCA) levels to assess the value of SCA-determination as a diagnostic approach to fatty liver syndrome. A. Comparison of the SCS levels between cows with and without ketonuria: Cows with ketonuria (n = 13) and with elevated plasma ASAT activity, indicating a moderate liver damage, showed a rise of their mean SCA level to 35.3 (+/- 14.9) mumol/l. Freshly calved cows without ketonuria (n = 10) had at the same time a mean SCA level of 17.9 (+/- 6.4) mumol/l, falling practically into the physiological range. The SCA level increased above the physiological range in 10 of the 13 cases with ketonuria, in seven of them even more than twice. B. Interrelationship between SCA level and hepatic lipid content: Increase in hepatic total lipid (TL) was always associated with SCA-elevation. The mean SCA level was 55 (+/- 22.0) mumol/l in cases of severe fatty liver (TL = 200-280 g/kg), and 39.5 (+/- 6.0) mumol/l in the moderate form (TL = 180-200 g/kg) of the syndrome. C. Peripartal SCA levels of cows with fatty liver: Clinically healthy cows (n = 6) with ketonuria and an elevation of serum ASAT and FFA concentrations had a mean SCA level of 35-45 mumol/l. One cow of this group, which developed acute fatty liver syndrome and died within the period of study, showed an extreme SCA level of 100 mumol/l in it's terminal stage.(ABSTRACT TRUNCATED AT 250 WORDS)     

Changes in the acid-base index of blood in dairy cows in relation to the seasonal composition of feed rations and phases of the reproductive cycle

The changes in the acid-base indices of the blood of dairy cows in different stages of reproduction cycle were studied in relation to the composition of feed ration in the autumn, winter, spring and summer feeding seasons. The cows were in the following stages of their reproduction cycle: Group I the fourth to sixth month of gravidity, II eighth to ninth month of gravidity, III one to two months after calving. The seasonal composition of feed ration was demonstrated to exert a significant influence on the acid-base balance of the blood of cows in the studied stages of reproduction. A considerable occurrence of metabolic acidoses with different levels of compensation was observed when the cows were given the autumn and winter feed rations. Subclinical acid-base disorders of different directions (metabolic and respiratory alkaloses, acidoses) frequently occurred in the green feeding season. The frequency of acid-base disorders as a result of incorrect nutrition was found to be the highest in highly pregnant cows (group II) and in those one to two months after parturition (group III), i. e. in the periods with a significant influence on the reproduction process. On the whole, the best situation as to the acid-base balance was found in cows in the fourth to sixth month of their gravidity, irrespective of the seasonal effect of feed ration.     

泌乳前期奶牛在不同采食水平下产奶性能及血清指标的差异比较

为了研究不同采食水平下泌乳前期奶牛产奶量、乳成分及血清指标的差异,从40头健康泌乳前期奶牛中选取18头,分高采食量(HF)组(平均采食量为53.67 kg/d)、中采食量(MF)组(平均采食量为48.55 kg/d)和低采食量(LF)组(平均采食量为44.15 kg/d),每组各6头,在相同的条件下饲养,试验期70 d,每周记录产奶量并采集奶样(50 mL),分别于试验开始、第30和60天采集血样。结果显示:与LF组相比,MF组、HF组的产奶量分别增加了4.79 kg、9.83 kg(P0.05),MF组、HF组的4%标准乳分别增加了5.94 kg(P0.05)、9.8 kg(P0.05),HF组的尿素氮下降了10.21%(P0.05);HF组的白蛋白、甘油三酯含量随采食水平显著升高(P0.05);MF组、HF组的游离脂肪酸、总胆固醇、胰岛素显著高于LF组(P0.05);HF组的胰岛素样生长因子、神经肽的含量显著高于MF组和LF组(P0.05);LF组的胆囊收缩素含量显著高于MF组和HF组(P0.05)。结果表明:高采食量的奶牛不仅产奶量高,营养物质和能量代谢快,而且与采食调控和能量代谢相关的生化指标和激素含量要比低采食奶牛变化更显著,为研究采食量调控提供科学依据。     

Plasma cholesterol levels and short-term adaptations of metabolism and milk production during feed restriction in early lactating dairy cows on pasture

Low plasma total cholesterol (TC) concentrations are characteristic during the negative energy balance in early lactating dairy cows. The objective was to investigate short-term effects of different TC concentrations during an aggravated energy deficiency through a 1-week concentrate withdrawal on adaptations of metabolism and milk production. Multiparous Holstein cows (n = 15) were investigated during 3 week beginning at 24 ± 7 DIM (mean ± SD). Cows were kept on pasture and received additional concentrate in experimental week 1 and 3, while in week 2, concentrate was withdrawn. Blood was sampled once and milk twice daily. Based on their average TC concentration during week 1 (prior to concentrate withdrawal), cows were retrospectively assigned into a high (H-Chol; n = 8, TC ≥ 3.36 mmol/L) and a low TC groups (L-Chol; n = 7, TC < 3.36 mmol/L). Concentrations of phospholipids and lipoproteins were higher in H-Chol compared to L-Chol throughout the study (p < 0.05). During concentrate withdrawal, milk yield, glucose and insulin concentrations decreased similarly in both groups, while milk fat, milk acetone and plasma BHB were higher in H-Chol compared to L-Chol (p < 0.05). Compared to initial values, plasma NEFA, TAG and VLDL increased in both groups within 2 days after concentrate withdrawal (p < 0.05). Concentrations of NEFA during week 2 were greater in L-Chol compared to H-Chol (p < 0.05). Despite reintroduction of concentrate, milk yield in H-Chol remained lower for two more days compared to week 1 (p < .05), whereas milk yield recovered immediately in L-Chol. Activity of aspartate aminotransferase was higher in H-Chol compared to L-Chol in week 2 (p < 0.05). Greater plasma TC concentrations were associated with a reduced increase of NEFA. Further research is warranted if TC concentrations are related to adipose tissue mobilization and fatty acid turnover.     

Individual variability in physiological adaptation to metabolic stress during early lactation in dairy cows kept under equal conditions

This study was conducted to investigate individual metabolic and endocrine adaptation to lactation under conditions of identical housing and feeding conditions in high-yielding dairy cows. Forty-five cows were studied on a research farm under standardized but practical conditions. From wk 2 before calving until wk 14 postpartum, blood samples were collected at weekly intervals and assayed for blood chemistry and various metabolites and hormones. Body weight, BCS, and backfat thickness were also recorded weekly. Milk yield, milk composition, and feed intake and energy balance were accordingly measured during the postpartum phase. The animals were retrospectively classified according to their plasma concentration of beta-hydroxybutyrate (BHB): cows in which a BHB threshold of 1 mM was exceeded at least once during the experiment were classified as BHB positive (BHB+); cows with BHB values consistently below this threshold were classified as BHB negative (BHB -). Using this classification, differences for NEFA and glucose concentrations were observed, but the mean calculated energy balance did not differ between the groups during the experimental period (-22.2 MJ of NE(1)/d +/- 4.7 for BHB+ and -18.9 MJ of NE(1)/d +/- 4.9 for BHB-). In BHB+ cows, the peripartum decrease (P < 0.05) of BW, BCS, and backfat thickness was more pronounced than in BHB- cows. Mean milk yields did not differ between groups. However, BHB+ cows had greater milk fat and lesser milk protein contents (P < 0.05), resulting in a greater (P < 0.05) fat:protein ratio than in BHB- cows. Thus, to some extent, cows were able to compensate for the negative energy balance by adjustments in performance. Milk acetone concentrations followed BHB concentrations in blood. Insulin-like growth factor-I and leptin concentrations were greater (P < 0.05) in BHB- cows during the time of observation than in the BHB+ cows. Comparing the reproductive variables recorded (first increase of progesterone, first service conception rate, number of services per conception, interval from calving to first AI, interval from first AI to conception, and days open) between the 2 groups yielded no significant differences. Our findings imply that despite comparable energy balance, there is considerable individual variation of the adaptive ability of cows during early lactation based on a variety of metabolic and endocrine variables.     

Variations of Neospora caninum antibody levels in milk during lactation in dairy cows

A longitudinal study was performed to investigate the variations of Neospora caninum antibody levels in individual milk during lactation as well as the association between antibody levels in serum and milk. Serum and milk samples of 15 milking cows were collected between February 2003 and September 2004 in three smallholder dairy farms in Khon Kaen province in northeast Thailand. All samples were analyzed for presence of antibodies by an N. caninum iscom ELISA test kit and the results were given as percent positivity (PP). The effects of time between calving and sampling, lactation number, and season on milk and serum PP were studied using Generalized Estimation Equations methods. All cows were antibody positive in either milk or serum at the first two consecutive samplings. Although serum and milk PP varied considerably, milk PP was consistently positive throughout the study. Cows of all lactation groups had a higher adjusted mean of milk PP at calving compared to later months after calving although the only significant difference was in first lactation. Serum and milk PP were always lower in first lactation than in second and later lactations. An adjusted mean of milk PP for cows classified as having serum PP> or =55 was significantly (P<0.05) higher than that of cows classified as having lower serum PP. Our results indicate that individual milk can be an alternative material to demonstrate presence of N. caninum antibodies in lactating cows.     

Changes in fatty acid composition of milk from lactating dairy cows during transition to and from pasture

Five Holstein cows producing an average of 25.4 ± 6.4 kg/d and 347 ± 111 days in milk were used to study the changes in fatty acid composition in milk from lactating dairy cows during transition to and from pasture. The 45-d experiment was divided into 3 periods. During the first 2 d of the experiment (Period I), cows were fed a TMR diet containing 50% conserved forage and 50% grain. On day 3, cows were turned out to pasture and remained on all-pasture diet for 29 d (Period II). On day 32, cows were withdrawn from pasture and offered a TMR diet until day 45 (Period III). Milk yield was recorded daily, and milk fat content and fatty acid (FA) composition were determined daily for composite samples collected from a.m. and p.m. milkings. Data were analyzed using spline regression (H₀ = zero slope) to determine whether there was any change in the concentration of a particular fatty acid after a specific time or whether it had stabilized. Cows produced an average of 25.2 ± 5.5, 13.7 ± 5.6, and 12.1 ± 4.8 kg/d of milk with 3.6, 4.2, and 3.6% fat during pre-pasture, pasture, and post-pasture diets, respectively. The conjugated linoleic acid (CLA) content was 0.45% of total fat during pre-pasture, reached to a maximum of 2.53% on day 23 into pasture and plateaued thereafter for the period. Milk fat C_18:1 t-11 content was 2.89% of total fat during pre-pasture, reached a maximum of 7.95% after day 22 in pasture, and plateaued afterwards. The C_18:2 content declined gradually from pre-pasture to pasture diet with no further decrease observed after day 22, while C_18:3 content increased until day 7 on pasture. The post-pasture CLA content in milk fat reached a value similar to pre-pasture within 4 days after the cows were withdrawn from pasture. No change in other fatty acids was observed after day 7 once the cows were switched to post-pasture diet. In the present study, it took 23 days to establish the highest level of CLA in milk fat after turning cows out to pasture, whereas only 4 days were needed to bring it back to the original level once the cows were withdrawn from pasture. Other milk fatty acids were stabilized around day 23 after turning cows out to pasture and by day 7 after being withdrawn from pasture and put back on a TMR diet inside the barn.     

The effect of feed barrier design on displacements during feeding of dairy cows in small herds

The aim of this study was to investigate the effect of feed barrier design on displacements in dairy cows fed only roughage diets in the bunk in small commercial dairy herds. Six Norwegian dairy herds with open barriers (OB) and six herds with individual headspace barriers (IHB) were randomly selected. Number of displacements and withdrawals without physical contact was somewhat higher, but not significantly higher, in the IHB herds than in the OB herds but the variation between herds within the type of barrier were very large. The number of pushes and buttings directed towards the front part of the body of cows was significantly higher in the OB herds than in the IHB herds whereas pushes and butts directed towards the side of cows were significantly higher in the IHB herds than in the OB herds.     

Magnesium in the blood and urine of cows during various stages of the reproductive interval being fed summer and winter feed rations

Magnesium concentration was investigated in the blood plasma and urine of 3460 cows in the course of four green-feeding seasons and four winter feeding seasons in 1980 to 1984. A decrease in the magnesium content in blood plasma was found to intensify in the last six weeks of gravidity. In the first stage of lactation the magnesium concentrations of plasma begin to grow to reach a relative maximum in the cows in the second stage of lactation. These regularities apply to both the summer and winter feeding seasons. The magnesium content in urine has a similar pattern. The summer values of the magnesiemia of whole cow populations are significantly higher than the winter values. Tendencies to lower magnesium concentrations generally prevail in both blood plasma and urine; these tendencies are most conspicuous in the cows in the last six weeks to parturition. As a rule, the concentrations of magnesium in urine were lower in summer than in the season of winter feed rations. As for the contents of the blood plasma magnesium of the cow populations as well as individual cows, there are considerable differences between various stages but the trends are the same in all groups. In the green feeding season the range of fluctuation of the magnesiemia values is larger than in the winter feeding season. The same tendency of changes in individual groups was also recorded in the magnesium concentrations in the urine of cows in different stages. However, the direction of the changes did not always correspond to the direction of the changes in the blood plasma. A practical requirement has been derived from the results of the study that magnesium contents should be increased in the feed rations given to high-pregnant cows and cows in the first lactation.     

5-Hydroxytryptamine-4 receptor messenger ribonucleic acid levels and densities in gastrointestinal muscle layers from healthy dairy cows

Serotonin (5-hydroxytryptamine, 5-HT) is involved in gastrointestinal tract (GIT) motor functions through binding to specific receptors located in the GIT walls. The objectives of the current study were to compare mRNA levels and binding sites of 5-HT(4) receptors (5-HTR(4)) in smooth muscle layers from the fundus abomasi, pylorus, ileum, cecum, proximal loop of the ascending colon (PLAC), and external loop of the spiral colon (ELSC) of healthy dairy cows, and to verify whether mRNA and protein expression were correlated. Smooth muscle samples were prepared by scraping the mucosa and submucosa from full-thickness intestinal wall samples. The mRNA levels of 5-HTR(4) were measured by real-time PCR and expressed relative to those of the housekeeping gene glyceraldehyde phosphate dehydrogenase. Binding studies were performed using the 5-HTR(4) antagonist [(3)H]GR113808. The mRNA levels of 5-HTR(4) were affected (P < 0.05) by location along the GIT. The mRNA levels of 5-HTR(4) in the ELSC and the ileum were greater than in the PLAC (P = 0.05 and P = 0.07, respectively) but similar to those of all other locations. The competitive binding of [(3)H]GR113808 to suspended membranes from the fundus abomasi, pylorus, cecum, and ELSC was best fit by a 2-site receptor model, whereas it was best fit by a 1-site receptor model in the ileum and PLAC. The mRNA levels and numbers of 5-HTR(4) were not correlated (r = 0.14; P = 0.71). In conclusion, mRNA and binding sites for 5-HTR(4) are present in the smooth muscle layer of the entire GIT of dairy cows and may play a role with respect to motility. The effects of activation of this receptor subtype may be different among GIT locations due to differences in the amount of high- relative to low-affinity binding sites.     

Fecal ammonia, urea, volatile fatty acid and lactate levels in dairy cows and their pathophysiological significance during diarrhea

Normal fecal samples were taken from lactating cows fed either a total mixed ration (TMR; n = 30) or pasture‐based diet (20) and from dry cows fed mainly on hay (15). Diarrheic fecal samples (n = 51) were collected from 21 sick dairy cows. Fecal analyses of ammonia, urea, lactate and volatile fatty acid (VFA) levels were used to evaluate colonic fermentation. Most normal feces had reasonably neutral pH, however, alkaline feces were observed in diarrheic cows. Although fecal lactate is higher in cows on grazing pasture, lactate levels were generally lower in the cows in the present study. Fecal VFA levels were higher in lactating cows than in dry cows. Elevated fecal urea was observed in diarrheic cows, however, many fecal samples in normal and diarrheic cows contained no urea. Fecal VFA levels in diarrheic cows were lower than in normal lactating cows, but were approximately equivalent to those in dry cows. Grazing or dry cows showed higher acetate and lower n‐butyrate proportions compared with TMR‐fed or diarrheic cows. Higher proportions of branched chain VFAs were observed in diarrheic cows, and the lowest level was observed in grazing cows. The present results indicate that intracolonic nitrogen equilibrium and proteolytic fermentation are altered by diarrheic status.     

The substitution of protein feed by lysine supplemented high protein wheat during the rearing and laying period in hens. 9. True amino acid digestibility of rations with varying lysine levels in hens who had a colostomy]

24 experimental birds were fed the same basal ration containing 74% high-protein wheat, 4% extracted soya bean meal, 7% extracted groundnut meal, 2% feed yeast, 1.75% dried green meal, 1.25% mixed vitamins and 10% of a mineral mixture. The birds were placed in 4 groups each comprising 6 hens. The first two groups received an optimum of lysine (0.68%) added to the ration. The rations for the two other groups contained 0.55% lysine. 6 birds of each group receiving either the lysinesupplemented or the unsupplemented rations were colostomated to investigate in which way the hydrolysed urine would affect the true amino acid digestibility. 8.3% of urinary N from the total amount of faecal N were precipitated as uranyl acetate in the faeces of hens fed the lysine-supplemented ration as compared with 7.3% urinary N in birds receiving the unsupplemented ration. The corresponding figures for non-precipitable faecal N were 8.9% and 8.2%. A comparison was made between the levels of amino acids excreted by colostomated and non-colostomated hens showing that 12.4% +/- 3% and 11.7% +/- 3% more amino acids (figures for the supplemented and unsupplemented rations) were excreted in the presence of urine. On the basis of these results the authors recommend that only colostomated hens should be used in digestibility and total metabolism trials.     

Changes in the serum levels of primary bile acids in dairy cows

Serum cholic acid (SCA) and serum chenodeoxycholic acid (SCDCA) concentrations were determined in healthy dairy cows by radioimmunoassay (RIA). The levels of these two primary bile acids were correlated with the cows' reproductive status. The lowest concentrations were measured in dry cows (SCA: 7.8 +/- 3.3 mumol/l, SCDCA.: 1.5 +/- 1.0 mumol/l). In freshly calved cows SCA and SCDCA was 17.8 +/- 6.9 mumol/l and 2.3 +/- 1.0 mumol/l, respectively, while in milking cows SCA and SCDCA was 15.8 +/- 5.7 and 2.3 +/- 0.8 mumol/l, respectively. SCA concentration showed a characteristic change on the days immediately after calving: on calving day it was close to the mean SCA concentration found for dry cows, then it underwent a striking abrupt rise and reached the value typical of post-parturient cows by post-partum (PP) day 4-5. Cholic acid was found to be the major primary bile acid in the blood of dairy cows. In dry cows the SCA:SCDCA ratio is 5:1. If the serum bile acid concentration rises, the SCA:SCDCA ratio will increase further.