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1.
Thirty‐four Holstein dry cows and 16 lactating cows were used in balance trials to identify the effects of feeding and animal performance on nitrogen (N), phosphorus (P) and potassium (K) excretion by dairy cows, and to develop prediction models for these excreta. Orchard grass silage, corn silage, alfalfa silage or timothy hay were offered to dry cows. Orchard grass silage or alfalfa silage, and concentrates were offered to lactating cows. In the statistical analysis, the independent variables were bodyweight (kg), dry matter (DM) intake (kg/day), milk yield (for lactating cows only, kg/day), water intake (free water plus water in feed, kg/day), intake (g/day) of N, P and K and dietary contents (% of DM) of crude protein, P and K. The dependent variables were N, P and K excretion (g/day) in feces and urine. In both dry and lactating cows, intake of N, P and K had large effects on corresponding excretion. The results indicated that a decrease in the intake of N, P and K could decrease the corresponding excretion. Further research by path analysis showed that K intake positively affected urinary N excretion in dry cows indirectly, through water intake and urine volume.  相似文献   

2.
Effects of exposure to hot environment on urea metabolism were studied in lactating Holstein cows. Four cows were fed ad libitum a total mixed ration and housed in a temperature‐controlled chamber at constant moderate (18°C) or high (28°C) ambient temperatures in a cross‐over design. Urea nitrogen (N) kinetics was measured by determining urea isotopomer in urine after single injection of [15N2]urea into the jugular vein. Both dry matter intake and milk yield were decreased under high ambient temperature. Intakes of total N and digestible N were decreased under high ambient temperature but urinary urea‐N excretion was increased. The ratio of urea‐N production to digestible N was increased, whereas the proportion of gut urea‐N entry to urea‐N production tended to be decreased under high ambient temperature. Neither return to the ornithine cycle, anabolic use nor fecal excretion of urea‐N recycled to the gut was affected by ambient temperature. Under high ambient temperature, renal clearance of plasma urea was not affected but the gut clearance was decreased. Increase of urea‐N production and reduction of gut urea‐N entry, in relative terms, were associated with increased urinary urea‐N excretion of lactating dairy cows in higher thermal environments.  相似文献   

3.
Data of 20 balance measurements from Holstein dairy cows and urine samples from 24 Japanese Black beef cows were collected to evaluate the relationships between urine pH and electrolyte status in cows fed forages. The ratio of forages in the diet was 70–100% in dairy cows and beef cows were fed Italian ryegrass silage and wheat bran. Mean urine pH in dairy cows was 8.10, ranging from 7.27 to 8.71, and that in beef cows was 7.73, ranging from 7.42 to 8.12. There were positive correlations between urine pH and urinary K contents (P = 0.0012) or K intake (P = 0.019) in dairy cows, although plasma Na, Cl and K had no effect on urine pH. There was a weak negative correlation (P = 0.039) between urine pH and urinary Na content in dairy cows. However, there were no significant correlations between urine pH and urinary Na, Cl and K contents in beef cows. These results indicate that the concentrated urinary K due to the increased K intake may directly enhance urine pH in dairy cows fed mainly forages.  相似文献   

4.
Abstract

Fifteen multiparous dairy cows were used in a five replicated 3×3 Latin square design to study the effects of ratio of rumendegradable-protein (RDP) and rumen-undegradable-protein (RUP) on nitrogen (N) conversion in Chinese Holstein dairy cows. Three diets were formulated isonitrogenously with varying ratio of RDP/RUP. High ratio of RDP/RUP resulted in high urinary N excretion and total N excretion, but no significant dietary effects were observed on milk yield, milk composition, and nitrogen excretion in faeces. Different protein degradability changed the partitioning of the N excretion between urine and faeces. Results indicated that reduction in ratio of RDP/RUP could improve the efficiency of N utilization in lactating dairy cows by reduced N excretion in urine and faeces without impairing milk production.  相似文献   

5.
Ten lactating cows were used to determine the effect of feeding non-fibrous carbohydrate (NFC) supplement before grazing on feed intake and nitrogen (N) utilization throughout a grazing season. The experiment was conducted from June to September. Cows grazed twice a day (2.5 h × 2) under a set stocking system and were fed NFC supplement (1 kg/4 kg of milk yield) 2 h before grazing (PRE) or immediately after grazing (POST). Cows were also fed a grass and corn silage mixture ad libitum. Herbage dry matter intake (DMI) was greater for PRE than for POST throughout the experiment and decreased from June to September. Conversely, silage DMI was less for PRE than for POST throughout the experiment and increased over the grazing season. Consequently, total DMI for PRE did not differ from that for POST. Milk urea-N concentration and urinary urea-N excretion in June did not differ between the treatments, whereas that after July was higher for PRE than for POST. Proportion of urinary N excretion to absorbed N intake in June was lower for PRE than for POST, but that after July was higher for PRE than for POST. Feeding NFC supplement before grazing would improve N utilization when cows eat large amounts of herbage high in N.  相似文献   

6.
An experiment was conducted to examine the effect that various isoenergetic diets, containing different quantities of soluble carbohydrate and fiber and different types of starch, have on nitrogen (N) balances. Six lactating dairy cows in early to midlactation consuming grass silage diets with not less than 600 g/kg total DMI as forage were used in the experiment. Four concentrates were prepared that had higher amounts of either fiber, soluble sugars, corn (low degradable starch source), or barley (high degradable starch source). Overall N utilization by the cows was poor, rarely exceeding 0.30 g milk N/g of dietary N intake. Fecal N outputs accounted for more than half of total N excreted in all treatments except for diets supplemented with high degradable starch, in which urinary N excretion was significantly higher compared with the other treatments. Milk yield was unaffected by concentrate type, averaging 19.9 kg/d, but milk protein content decreased from 32.9 for starch-based diets to 30.9 and 30.0 g/kg for the soluble sugar- and fiber-based diets, respectively. The efficiency of N utilization improved in the low degradable starch treatment, which had lower N excretion (65%) and higher protein concentration in milk. Furthermore, feeding cows corn-based concentrates reduced urinary N excretion by almost 30% compared with barley-based concentrates; therefore, feeding corn-based diets is recommended for the reduction of nitrogen pollution in lactating dairy cows.  相似文献   

7.
The study set out to examine the effects of supplementing grass silage with various levels of protein concentration and degradability on dietary nitrogen (N) excretion in lactating dairy cows consuming at least 60% forage. Six Holstein/Friesian cows in early to midlactation were offered six diets comprising two levels of crude protein (210 and 290 g/kg DM) and three levels of protein degradability in the concentrate achieved using different amounts of untreated or formaldehyde-treated soybean meal. Despite a difference of almost 100 g/d in N intake, apparent fecal and milk N outputs were not significantly affected. Protein degradability also had no effect on N outputs in feces and milk. However, there was a major effect of both level and degradability of CP on urinary N output. Moreover, an interaction between level and degradability of CP was detected, such that the rate at which urinary N increases with increasing CP degradability was higher on the high-CP than on the low-CP diet. A low level of protein (150 g/kg DM in the diet) and medium to low rumen-degradable protein supplements provided a significant reduction in N excretion without compromising lactational performance (mean 24.8 kg/d), in terms of both milk yield and composition. This study also demonstrated that a high efficiency of N utilization could be achieved on low-CP diets (supplying less than 400 g N/d), with feces being the main route of N excretion, whereas an exponential excretion of urinary N was observed as N intake exceeded 400 g N/d.  相似文献   

8.
The effects of barley flour on the fermentation parameters of alfalfa silage and on the productivity of dairy cows were investigated. Alfalfa forage was ensiled either with or without barley flour. Barley flour was soaked in water for 24 h before being mixed with alfalfa (12 kg: 100 kg dry matter bases) at ensiling. Eighteen multi-parous cows were assigned to three equal treatment groups using a completely randomized design. Three isocaloric and isonitrogenous total mixed rations containing alfalfa hay, ordinary alfalfa silage or barley flour mixed alfalfa silage were then prepared. The concentrations of ammonia nitrogen, acetic acid and butyric acid were lower in barley flour mixed alfalfa silage compared to that in ordinary alfalfa silage but the concentration of lactic acid was lower in the ordinary alfalfa silage. Feeding behavior, milk yield and composition, ruminal fermentation and blood metabolites were measured. Although dry matter intake and milk production were not affected, the effect of preparation of alfalfa influenced feeding behavior and rumen fermentation parameters. Cows on alfalfa silage diets spent longer ruminating compared to those fed alfalfa hay. The ruminal ammonia nitrogen and blood urea were affected by ensiling (alfalfa hay versus alfalfa silages) while both parameters were lower in cows fed on barley flour mixed alfalfa silage than those fed on ordinary silage. Although similar blood glucose was recorded for cows fed on alfalfa silages, it was higher in cows fed on alfalfa hay. It is concluded that the addition of barely flour when making alfalfa silage may improve both the fermentation process during ensilage and the ruminal ammonia nitrogen utilization with no significant effects on productivity.  相似文献   

9.
Twenty-three lactating dairy cows were switched from a standard diet to a ration of alfalfa/grass silage and 1 kg rapeseed cake supplemented with raw potatoes and fodder beets allowed on a semi-restricted basis. The effects of feed choice on urinary markers for nitrogen metabolism were evaluated by the Stepwise regression technique. Each kilogram dry matter of potatoes and fodder beets lowered milk urea concentration and also the urinary ratio urea/creatinine to a similar extent, but allantoin and fecal results suggested larger hindgut fermentation and hence lower ruminal microbial protein production with potatoes than with fodder beets. The variation for concentration of urinary constituents associated with animal, sampling day and sampling time suggests multiple sampling within a day as preferable for spot sampling. It is concluded that the reluctance to potatoes by some cows may cause initial difficulties when fed to high yielding cows naïve to the feed.  相似文献   

10.
日粮类型对奶牛粪尿特性及氮排放的影响   总被引：3，自引：0，他引：3  
通过研究不同类型日粮对泌乳奶牛粪尿及氮排放的影响,达到减少和控制氮排放的目的,本试验选用12头体重514 kg、年龄3～5岁的中国荷斯坦奶牛为试验动物,分为3组,分别饲喂粗料为干秸秆玉米,精粗比40∶60的A日粮、粗料为玉米青贮,精粗比分别是40∶60和60∶40的B和C日粮进行了对其粪尿特性及氮排放的试验研究。结果表明,日粮类型对奶牛粪便及尿液产生量均有一定的影响。粪便产生量结果为秸秆型A日粮>青贮型低精比B日粮>青贮型高精比C日粮。3种日粮的尿液产生量为C日粮>B日粮>A日粮。同时,日粮类型对奶牛氮平衡具有显著的影响,秸秆型日粮的乳氮、尿氮含量和氮的消化率极显著低于青贮型日粮低(P<0.01),粗料均为青贮玉米条件下,随日粮精料水平的提高,氮消化率和尿氮极显著增加(P<0.01),粪氮和乳氮增加不显著(P>0.05)。结果提示,秸秆型日粮的摄入氮主要是从粪中排出,粗料为青贮玉米时,随日粮精料水平的提高粪氮比例减少,而尿氮比例增加,粪氮和尿氮占总粪尿氮的比例基本一致。  相似文献   

11.
Starea, an intimate mixture of gelatinized wheat starch and urea, was tested again urea with regard to the ammonia release in the rumen, the amount and composition of the nitrogen fraction reaching the intestine, the nitrogen and energy balances, and the performance of lactating cows. Maize silage was the basal feed in all experiments. The ammonia concentration in the rumen liquor was measured in two cows fitted with a permanent rumen cannula. The curve of the ammonia concentration was about the same with both nitrogen supplements, and peaked at about 250 mg/l (14.7 mmol/l) two hours postfeeding. Two dry cows fitted with a re-entrant cannula at 10 cm from the pylorus were fed with maize silage supplemented with increasing amounts of either urea or starea. The duodenal nitrogen flow rapidly levelled off with both supplements and no significant difference between them could be detected. The amount of ammonia in the duodenal digesta remained very low. Nitrogen digestibility measured in lactating cows was not noticeably affected when starea instead of urea was added to maize silage. However, nitrogen excretion in the urine tended to decrease, while nitrogen secretion in milk was augmented with starea. The digestibility of the rations and their metabolizable energy supply were not significantly affected, and milk production was quite the same with both supplements, apart from the higher amount of milk protein obtained with starea compared with urea. As a general conclusion from the whole work conducted on the nutritive value of urea for lactating cows, it can be stated that the decline in performance of the animals after substitution of urea for conventional protein is mainly due to a decrease of the metabolizable energy concentration in the diets. None of the attempts tested in an effort to improve the nutritive value of urea was able to overcome this difficulty.  相似文献   

12.
Ten Holstein cows averaging 120 d in lactation were arranged in replicated 5 x 5 Latin squares with 3-wk periods to evaluate the role of sulfur (S) in the dietary cation-anion balance equation. Diets were based on corn silage in Exp. 1 and sorghum silage in Exp. 2. Supplemental S and chloride (Cl) from the double sulfate of potassium and magnesium and CaCl2 were used to manipulate dietary cation-anion balance from 0 to +30 meq when expressed as meq [(Na + K)-(Cl + S)]/100 g diet DM and from +19 to +49 meq when expressed as meq [(Na + K)-Cl]/100 g diet DM. Blood pH was not affected by cation-anion balance, although both S and Cl supplementation tended to lower pH. Blood HCO3- and urine pH decreased and plasma calcium (Ca) and urinary Ca excretion increased as anion was added to the diet. Milk fat production tended to be increased by the low S supplementation. Dietary Cl and S had similar effects on acid-base status. Therefore, we suggest that S be included with Cl in the dietary cation-anion balance equation for lactating dairy cows as follows: meq [(Na + K)-(Cl + S)]/100 g diet DM. Although response of acid-base status to S and Cl was similar, as more data comparing the acidogenicity of S vs Cl become available, it may be necessary to include a modifying coefficient for S in the equation to adjust for differences between S and Cl in acid-generating potential. This coefficient may be further dependent on the dietary source of S.  相似文献   

13.
Isobutylidene diurea (IBDU) was tested against urea with regard to the ammonia release in the rumen, the amount and composition of the nitrogen fraction reaching the intestine, the nitrogen and energy balances and the performance of lactating cows. Maize silage was the basal feed in all experiments. The ammonia concentration in the rumen liquor was measured in two dry cows fitted with a permanent rumen cannula. The ammonia release was clearly restrained when IBDU was substituted for urea, and the peak values were of the same order as those found with soybean meal. Two dry cows fitted with a re-entrant cannula at 10 cm from the pylorus were fed with maize silage supplemented with increasing amounts of either urea or IBDU. The duodenal flow levelled off with urea, but it continued to rise with IBDU even when high amounts were added to the silage. However, a large fraction of this increase was in the form of ammonia, corresponding to 60% of the dietary nitrogen supplied by IBDU. The amount of non-ammonia nitrogen was also higher with IBDU. The nitrogen balance of lactating cows was not noticeably affected when IBDU instead of urea was added to the maize silage. In the same manner, the digestibility of the rations and their metabolizable energy supply were not significantly modified, and the milk productions were quite similar with the two N compounds, apart from the tendency to lower milk fat and milk protein productions.  相似文献   

14.
The objective of this study was to evaluate the effect of substituting brown rice grain for corn grain in total mixed ration (TMR) silage containing food by‐products on the milk production, whole‐tract nutrient digestibility and nitrogen balance in dairy cows. Six multiparous Holstein cows were used in a crossover design with two dietary treatments: a diet containing 30.9% steam‐flaked corn (corn TMR) or 30.9% steam‐flaked brown rice (rice TMR) with wet soybean curd residue and wet soy sauce cake. Dietary treatment did not affect the dry matter intake, milk yield and compositions in dairy cows. The dry matter and starch digestibility were higher, and the neutral detergent fiber digestibility was lower for rice TMR than for corn TMR. The urinary nitrogen (N) excretion as a proportion of the N intake was lower for rice TMR than for corn TMR with no dietary effect on N secretion in milk and fecal N excretion. These results indicated that the replacement of corn with brown rice in TMR silage relatively reduced urinary N loss without adverse effects on feed intake and milk production, when food by‐products such as soybean curd residue were included in the TMR silage as dietary crude protein sources.  相似文献   

15.
Effects of different dietary rumen undegradable (RUP) to degradable (RDP) protein ratios on ruminal nutrient degradation, feed intake, blood metabolites and milk production were determined in early lactation cows. Four multiparous (43 ± 5 days in milk) and four primiparous (40 ± 6 days in milk) tie‐stall‐housed Holstein cows were used in a duplicated 4 × 4 Latin square design with four 21‐day periods. Each period had 14‐day of adaptation and 7‐day of sampling. Diets contained on a dry matter (DM) basis, 23.3% alfalfa hay, 20% corn silage and 56.7% concentrate. Cows were first offered alfalfa hay at 7:00, 15:00 and 23:00 hours, and 30 min after each alfalfa hay delivery were offered a mixture of corn silage and concentrate. Treatments were diets with RUP:RDP ratios of (i) 5.2:11.6 (control), (ii) 6.1:10.6, (iii) 7.1:9.5 and (iv) 8.1:8.5, on a dietary DM% basis. Different RUP:RDP ratios were obtained by partial and total replacement of untreated soybean meal (SBM) with xylose‐treated SBM (XSBM). In situ study using three rumen‐cannulated non‐lactating cows showed that DM and crude protein (CP) of SBM had greater rapidly degradable fractions. The potentially degradable fractions were degraded more slowly in XSBM. Treatment cows produced greater milk, protein, lactose, solids‐non‐fat and total solids than control cows. Increasing RUP:RDP reduced blood urea linearly. Feed costs dropped at RUP:RDP ratios of 6.1:10.6 and 7.1:9.5, but not at 8.1:8.5, compared with the 5.2:11.6 ratio. Intake of DM and CP, rumen pH, blood glucose, albumin and total protein, faecal and urine pH, changes in body weight and body condition score, and milk lactose and solids‐non‐fat percentages did not differ among treatments. Results provide evidence that increasing dietary RUP:RDP ratio from 5.2:11.6 to 7.1:9.5 optimizes nitrogen metabolism and milk production and reduces feed costs in early lactation cows. Reduced blood urea suggests reprodutive benefits.  相似文献   

16.
OBJECTIVE: To develop a simple diagnostic test to assess sodium status in large ruminants on the basis of the sodium-to-potassium ratio (Na:K) and to determine its relevance. ANIMALS: 7 buffalo heifers and 21 lactating, pregnant, and nonpregnant dairy cows and heifers. PROCEDURE: Buffalo heifers were subjected in 2 experiments to variable dietary sodium intake or sodium depletion and changes in sodium and potassium concentrations; Na:K was simultaneously monitored in various body fluids to study its value for indicating sodium status. Validity of the muzzle secretion test was assessed. RESULTS: Muzzle secretion and urinary Na:K and sodium concentration, but not serum electrolyte concentrations, reflected the sodium status of buffalo heifers in response to the widely variable intake of sodium (0.03 to 0.16% of dry matter [DM]). Progressive sodium depletion during an 11-day period, using saliva deprivation caused reciprocal changes in sodium and potassium concentrations in saliva and muzzle secretion, but not in urine. Decreasing urine sodium concentration was associated with decreasing urine potassium concentration. Saliva, urine, and muzzle secretion Na:K closely reflected the degree of sodium deficit. CONCLUSIONS AND CLINICAL RELEVANCE: Buffaloes or dairy cows maintained on optimal sodium intake had muzzle secretion and urine Na:K > 0.30. Muzzle secretion or urine Na:K < 0.20 or < 0.10, respectively, was indicative of sodium deficiency. Analysis of muzzle secretion Na:K, and to a large extent urine Na:K, may be used as a convenient diagnostic tool to assess sodium status in large ruminants. It has accuracy similar to that of saliva Na:K.  相似文献   

17.
Nine multiparous Holstein cows were used in a replicated 3 × 3 Latin square design to determine the effects of substituting corn grain with brown rice (BR) grain in total mixed ration (TMR) silage on milk yield, ruminal fermentation and nitrogen (N) balance. The TMR silages were made from the ensiling of TMR containing (dry matter basis) 50.1% forage in rice silage and corn silage combination, and 49.9% concentrate. The grain portion of the diets contained 31.2% steam‐flaked corn, 31.2% steam‐flaked BR or an equal mixture of corn and BR. Dietary treatments did not affect dry matter intake, milk yield and milk fat, protein and lactose yields. The ruminal pH and total volatile fatty acid concentrations were not affected by dietary treatment. The urinary N excretion decreased linearly (P < 0.01) in response to increased levels of BR, with no dietary effect on N intake, N secretion in milk and fecal N excretion. Our results indicate that steam‐flaked BR is a suitable replacement for steam‐flaked corn in dairy cow diets, and that it can be included in rations to a level of at least 31.2% of dry matter without adverse effects on milk production, when cows were fed rice silage and corn silage‐based diets.  相似文献   

18.
The reduction of nitrogen (N) excretion in animal production is crucial in intensive farming systems particularly in the developed countries. In this study, a model to predict N excretion in cattle was developed based on existing feeding standards and evaluated using independent N balance experiments for Holstein steers and lactating cows and Japanese Black (JB) steers. Although model predictions for fecal and urinary N excretions appeared to be close to observed values in plot figures, statistical analysis showed that the model tended to over-predict both fecal and urinary N excretions, especially in Holstein lactating cows. This was because body weight changes of cows during lactation period were not considered in the model due to the lack of information (i.e., body weight gain or loss) available in the experimental data for evaluation. There were large mean bias and small line bias for urinary N prediction, but reverse results were obtained for fecal N prediction. The largest mean square prediction errors for both N excretions were due to random variation in all cases. When all data were pooled (combined), the accuracy for predictions for fecal N excretion was considerably high (r2 = 0.94), indicating that the model may predict fecal N excretion beyond breeds, sexes and physiological states (growing and lactating). More information and accumulated data will be required to predict urinary N excretion under a wide range of genotype and environmental situation.  相似文献   

19.
Nitrogen requirements of lactating cows were calculated by means of statistical relationships established for nitrogen excretion in faeces and urine, for nitrogen balance, and for nitrogen flow in proximal duodenum and terminal ileum. The data used for elaboration of the relationships came from simultaneous measurements of nitrogen and energy balances. It appears that an increase in dietary nitrogen solubility augments total nitrogen and apparently digestible nitrogen requirements of the animals because of higher urinary nitrogen losses. This effect can be off-set by an increased metabolizable energy intake. High proportions of concentrates in the diets cause a shift in nitrogen excretion from faeces to urine. Requirements of intestinal absorbed nitrogen and its conversion into milk protein are dependant of dietary nitrogen solubility and metabolizable energy concentration, while they are favourably influenced by energy supply. Crude protein concentration is not an adequate way for expressing optimal protein supply in lactating cows because it may vary between 11.2% and 20.0% according to dietary characteristics for the same animal.  相似文献   

20.
The objective of this study was to assess the relationship between milk urea nitrogen (MUN, mg/dL) and urinary nitrogen (UN) excretion (UN, g/day) in lactating Chinese Holstein cows. Twelve mature lactating cows were divided into four groups by their days in milk and milk yield and fed four different crude protein levels diets (13.2, 14.1, 15.0 and 16.2%, dry matter (DM) basis) with a similar net energy content. The experiment was conducted according to a multiple 4 × 4 Latin square design. The entire length of the experimental periods was 56 days, each period consisting of 14 days with days 1–9 for adjustment and days 10–14 for the collection of urine and data. The crude protein content had significant effects on the MUN content and UN excretion (P < 0.01), but little effect on milk yield and composition (P > 0.05). There was a close relationship between MUN and UN excretion (P < 0.001). The following equations were established to predict UN (g/day) excretion based on MUN (mg/dL) in the lactating Chinese Holstein cows: UN = 10.07 × MUN + 47.29. The results obtained in this study suggested that MUN could be used as a parameter to estimate UN excretion, while the equations to predict UN based on MUN might be somewhat different due to the differences in breeds of cow.  相似文献   

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