Some attempts to improve the nutritive value of urea for dairy cows. 3. Its adjunction to fermentable carbohydrates: starea

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.     

The substitution of soybean meal for urea: the effect on the ammonia content of the rumen fluid, the N flow in the duodenum, the nitrogen and energy balances and the milk production

In different experiments, the nutritive value of maize silage associated with urea was compared with that of the same forage associated with soybean meal. The ammonia concentration in the rumen fluid was measured with two dry cows fitted with a permanent rumen cannula. Urea gave rise to much higher NH3 concentrations compared with soybean meal. The duodenal N flow was measured with two dry cows fitted with a re-entrant cannula at 10 cm from the pylorus. Adding increasing amounts of either of the two N supplements to the maize silage showed that they were equivalent with low N intakes. However, clearly more N reached the intestine with soybean meal than with urea when the N intake increased. With 33 cows in the second part of lactation, the substitution of soybean meal for urea decreased the urinary N loss. At the same time, it significantly increased the mammary protein secretion and the milk production. The increase of the dietary metabolizable energy density noted under these feeding conditions corresponded to about two thirds of the increase of the milk production. Milk composition was only slightly affected.     

Effects of diets containing alfalfa hay or barley flour mixed alfalfa silage on feeding behavior, productivity, rumen fermentation and blood metabolites in lactating cows

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.     

Ammonia and urea in corn silage-based complete mixed diets for dairy cows

Source of supplemental N was evaluated in three corn silage-based complete mixed diets (CMD) fed to lactating dairy cows. Diets were formulated to be isonitrogenous and contained 60% corn silage and 40% concentrate on a dry matter basis. Diets were: CMD-A, ammoniated corn silage (ammonia provided 16% of total N) plus concentrate; CMD-U, untreated corn silage and concentrate (16% of total N from urea) and CMD-S, untreated corn silage plus concentrate with soybean meal. Ammoniation at 1.0% of dry weight increased crude protein content of silage from 8.5 to 12.7%. Daily means for cows fed CMD-A, CMD-U and CMD-S were: 24.2, 24.3 and 24.5 kg of fat-corrected milk; 3.17, 3.10 and 3.15% milk protein; 3.41, 3.67 and 3.63% milk fat and 3.02, 2.99 and 3.02 kg intake of total dry matter/100 kg body weight. Differences were not significant except for reduced milk fat percentage for cows fed the ammoniated corn silage diet. Both anhydrous ammonia and urea at 16% of total dietary N were found to be practical and economical substitutes for part of the supplemental soy protein. When compared to CMD with all soybean protein, greater savings in feed costs resulted from inclusion of ammoniated corn silage than with inclusion of urea.     

Performance of tropical dairy cows fed whole crop rice silage with varying levels of concentrate

The objective of this experiment was to evaluate the effect of concentrate/milk yield ratios on feed intake, nutrient digestibility, rumen fermentation efficiency, and milk production in dairy cows fed with a basal diet of whole crop rice silage (WCRS). Sixteen crossbred cows (75 % Holstein-Friesian (HF) and 25 % Thai cows) in mid-lactation were assigned to four dietary treatments in a completely randomized design. Treatments corresponding to four concentrate/milk yield ratios (0, 1:1, 1:2, and 1:3 (kg/kg)) were used. All cows were offered WCRS (with 1.5 % urea and 3 % molasses) ad libitum. Silage and concentrate were fed individually twice a day. Results revealed that dry matter intake (12.8–14.5 kg/day), nutrient digestibility (62.5–68.7 %), and rumen fermentation efficiency were not significantly affected by concentrate supplementation. Milk yield (10.2–11.5 kg/day) and milk composition were similar between cows fed with sole WCRS and those supplemented with concentrate mixture, although milk fat tended to increase in cows fed with sole WCRS. In conclusion, sole WCRS fed to dairy cows without concentrate supplementation resulted in similar feed intake, nutrient digestibility, rumen fermentation, and milk production as compared to those supplemented with concentrate in lactating dairy cows. These results suggest that in tropical areas where rice crop is surplus, WCRS could sustain reasonable levels of milk production among dairy cows with little or no concentrate supplementation provided that urea and molasses are included in the silage.     

Effects of Moringa oleifera silage on milk yield,nutrient digestibility and serum biochemical indexes of lactating dairy cows

This study investigated the effects of Moringa oleifera (MO) as a partial substitute of alfalfa hay on milk yield, nutrient apparent digestibility and serum biochemical indexes of dairy cows. MO was harvested at 120 days post‐seeding. Fresh MO was cut, mixed with chopped oat hay (425:575 on a DM basis), ensiled and stored for 60 days. Sixty healthy Holstein dairy cows were allocated to one of three groups: NM (no MO or control), LM (low MO; 25% alfalfa hay and 50% maize silage were replaced by MO silage) or HM (high MO; 50% alfalfa hay and 100% maize silage were replaced by MO silage). The feeding trial lasted 35 days. The LM and HM diets did not affect dry matter (DM) intake, milk yield or milk composition (lactose, milk fat, milk protein and somatic cell count). The apparent digestibility of DM and NDF was lower for HM group than NM group. Additionally, there were no significant differences in serum biochemical indexes between the LM and NM groups. The HM group had lower serum concentrations of total cholesterol, high‐density lipoprotein cholesterol, and low‐density lipoprotein cholesterol and higher serum concentrations of urea than the NM group. The partial replacement of alfalfa hay (≤50%) and maize silage with MO silage had no negative effects on milk yield, in vivo nutrient apparent digestibility or serum biochemical indexes of lactating cows.     

Isobutylidene diurea, a new NPN source for ruminants. 3. Excretion of isobutylidene diurea following feeding of N-15 isobutylidene diurea to lactating cows

2 experimental cows received isobutylidenedi urea added to a natural diet in amounts of 175 g (I) and 730 g (II) per day for a period of several weeks before the trial was started. On the 1st day of experiment the morning dose was labelled with 5.05 g of excess 15N. 8 hrs after the beginning of the trial of 15N level in the TCE soluble portion of blood plasma (TCE=trichloroacetic acid) increased and remained at an elevated level until the 36th hour of experiment. Similarly, the values for maximum urinary 15N concentrations were maintained for a prolonged period of time. Isobutylidenedi urea was excreted with the urine in rates related to its solubility. Only small percentages of the 15N intake were excreted in the TCE soluble portion of the milk (cow I: 0.03%; cow II: 0.05%). The 15N-labelling of milk protein provides evidence for the fact that nitrogen from IBDU is utilized for the synthesis of milk in the cows. The amount of urea in milk averaged 400 mg per litre. None of the milk samples tested contained IBDU.     

日粮瘤胃能氮平衡对奶牛生产性能和牛奶中尿素氮的影响

本研究以12头泌乳中期荷斯坦牛为研究对象,采用随机区组设计分为3组,在干物质进食量相似的条件下,增加瘤胃快速可发酵能量,用玉米粉颗粒替代甜菜渣颗粒,三个处理分别替换0kg、0．4kg和0．8kg,试验期61d。结果表明,日粮处理对奶牛的产奶量和乳成分没有明显影响,玉米粉颗粒替代甜菜渣颗粒饲喂奶牛后可显著降低牛奶中尿素氮（MUN）浓度,评价目粮的瘤胃能氮平衡表明为正平衡,有明显低水平的MUN。试验证明,可以用日粮瘤胃能氮平衡判断饲喂日粮对奶牛MUN的影响。     

Metabolic and productive response to ruminal protein degradability in early lactation cows fed untreated or xylose‐treated soybean meal‐based diets

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.     

Effects of urinary excretion of nitrogen, potassium and sodium on urine volume in dairy cows

Data of 50 balance measurements were collected from dry and lactating Holstein cows to clarify the effects of urinary excretion of nitrogen (N), potassium (K) and sodium (Na) on urine volume in cows. In dry cows, orchardgrass silage, timothy hay, alfalfa silage and corn silage were offered to meet the TDN requirement. Orchardgrass silage or alfalfa silage diets were offered in switch back trials in lactating cows. There were no relationships between urinary excretion and plasma concentrations of K or Na in cows, but urinary N excretion increased with the increase of plasma urea nitrogen. There was positive correlation between urinary excretion and urinary content of Na, but urinary K contents increased rapidly by 1.3% with the increasing urinary K excretion and thereafter remained almost constant. The increasing urinary K and N excretion enhanced urine volume in cows, but urine production in cows was accurately estimated from the regression equation of urine K excretion on urine volume. Urine volume was not affected by urinary Na excretion. These results suggest that the increase of urine volume in cows affected by the increasing urinary excretion of K and N may be due to the maintenance of urine or plasma osmolality.     

Proportions of potatoes and fodder beets selected by dairy cows and the effects of feed choice on nitrogen metabolism

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.     

Effects of feeding and animal performance on nitrogen, phosphorus and potassium excretion by Holstein cows

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.     

Improving the nutritive value of wheat straw with urea and yeast culture for dry season feeding of dairy cows

The study evaluated the effects of feeding urea treated/supplemented wheat straw-based diets with addition of yeast culture (YC) as a dry season feed for dairy cows. Wheat straw diets with 3.6 % urea and 5.8 % molasses were formulated to upgrade nonprotein nitrogen levels and fibre degradation in the rumen. Yeast culture was included at 0 and 10 g/cow/day in mixer with commercial dairy meal to improve on fibre degradation and milk yield. Two experiments were conducted. Firstly, an in sacco dry matter degradability (DMD) trial with three steers in a completely randomized design (CRD) with a 3?×?2 factorial arrangement to determine the effects on intake and rumen degradation parameters. Secondly, feeding trial with 18 lactating cows in a 3?×?2 factorial arrangement at two levels of yeast culture (0 and 10 g/cow/day) and three types of urea interventions: No intervention (WS); addition of urea to straw at the time of feeding (USWS); and 7 days incubation of straw with urea (UTWS). Yeast cultures addition had no effect on rumen pH and NH₃-N, but urea intervention showed an effect on rumen pH with USWS being lowest (p?<?0.05). Both urea interventions and yeast culture addition had no effect (p?>?0.05) on dry matter intake, milk yield, and milk composition but they increased (p?<?0.05) propionate yields.     

4个青贮玉米品种的青贮发酵品质及瘤胃降解特性的比较

为筛选出适合在苏中地区种植的青贮玉米(Zea mays L.)品种,本试验对4个青贮玉米品种进行全株青贮,比较青贮品质和瘤胃降解特性。试验结果表明：‘雅玉8号’全株玉米青贮的乳酸含量较高(P<0.05),pH值、氨态氮含量和乙酸含量低于‘扬大109’(P<0.05)。全株玉米青贮的瘤胃干物质有效降解率由高到低依次为‘康源01号’(40.98%)、‘扬大109’(39.25%)、‘雅玉8号’(37.69%)和‘牧场06号’(35.29%)。瘤胃中性洗涤纤维有效降解率由高到低依次为‘扬大109’(29.91%)、‘雅玉8号’(28.75%)、‘牧场06号’(27.12%)和‘康源01号’(21.20%)。综上所述,在本试验选取的4个青贮玉米品种中,‘牧场06号’是最适宜在苏中地区推广种植的青贮玉米品种。     

Performance of lactating dairy cows fed a diet based on treated rice straw and supplemented with pelleted sweet potato vines

The purpose of this study was to evaluate the effects of sweet potato vine pellet (SWEPP) in concentrate diets on nutrient digestibility and rumen ecology in lactating dairy cows fed on urea-treated rice straw. Three multiparous Holstein crossbred cows in mid-lactation were randomly assigned according to a 3?×?3 Latin square design, and the treatments were as follows: T1 = control (no supplementation), T2 = supplementation of sweet potato vine pellet with 50 g/kg urea (SWEPP I) at 300 g/head/day, and T3 = supplementation of sweet potato pellet with 100 g/kg urea (SWEPP II) at 300 g/head/day, in concentrate diets, respectively. The result revealed that supplementation of SWEPP did not affect feed intake, ruminal pH, and blood urea nitrogen (P?>?0.05). However, apparent digestibilities of organic matter, crude protein, and neutral detergent fiber were higher in SWEPP II than those in others. Furthermore, ruminal ammonia nitrogen (NH₃-N) and milk yield were significantly higher (P?<?0.05) in animals fed with SWEPP II than those fed with SWEPP I and control, respectively. In addition, there were no differences in purine derivatives and microbial nitrogen supply among all the treatments. Based on this study, it could be concluded that SWEPP is a good source of supplement which resulted in significant improvement in apparent digestibility, rumen fermentation, and milk yield in lactating dairy cows fed on urea-treated rice straw.     

Studies on the use of lucerne silage source for high-milk-producing dairy cows

Studies on the use of lucerne silage as a forage source for high-yielding dairy cows. It was the main objective of this study to investigate effects of lucerne silage inclusion in maize silage-based rations on dry matter intake, milk yield and metabolic parameters of high yielding dairy cows. Three total mixed rations (TMR) were used. They contained as the main forage source on a dry matter basis 41.5% maize silage and 12% grass silage (ration maize) or 18% maize silage and 29% of either grass silage (ration grass) or lucerne silage (ration lucerne). Organic matter digestibility, determined with wether sheep, was 77 and 65% for the grass and the lucerne silage, respectively. Each TMR was fed to 4 wether sheep to determine crude nutrient digestibilities. The content of net energy for lactation (NEL), as calculated from digestible crude nutrients, was (MJ/kg dry matter (DM)): 7.1 (maize), 7.2 (grass) and 6.8 (lucerne). Based on the results of a chemical fractionation of crude protein it was calculated that the content of utilisable crude protein (nXP) was not below 167 g/kg DM and that the N balance in the rumen was not negative for all 3 TMR. The TMR were fed for 169 days to at least 28 dairy cows per treatment which were in their first half of lactation. Feed intake, milk performance data and physiological indicators were measured for each individual cow. The DM intake was significantly higher in treatment lucerne (23.2 kg/d) than in treatments grass (21.2 kg/d) and maize (22.6 kg/d). Daily intakes of NEL and nXP were significantly lower in treatment grass than in the other two treatments. Milk yield was significantly higher in treatment maize (41.7 kg/d) than in treatments grass (37.3 kg/d) and lucerne (38.5 kg/d). This was associated with a significantly lower milk fat content in treatment maize (3.5%) in comparison with the other two treatments (3.9% each). Milk protein content was unaffected by treatment (3.4% on average). Similarly, the acetone content of milk was not significantly different between treatments. The beta-hydroxybutyrate content of the deproteinized blood was significantly higher in treatment lucerne at start of lactation, but this difference disappeared in subsequent parts of the experimental period. Measurements of back fat thickness indicated mobilisation and retention of energy by cows during the experimental period to be similar in all treatments. It is concluded that lucerne silage is a suitable forage source for high yielding dairy cows in spite of its low digestibility.     

The effect of Saccharomyces cerevisiae1026 used alone or with vitamin-mineral premix on biochemical parameters of blood and milk in dairy cows

When evaluating the effects of yeast culture (Saccharomyces cerevisiae1026) supplied with or without a vitamin premix and mineral bioplexes on some intermediates and end-products involved in the synthesis of milk constituents in 30 early-lactation Black and White Lowland cows, no significant differences were found in the glucose level, mineral contents and enzyme activities of the blood serum. The effect of yeast culture on the availability of minerals for milk synthesis depended upon the dynamics of degradation of mineral bioplexes in the rumen and the cows' mineral status. The insignificant increase found in blood total protein content and the simultaneous small differences in blood urea nitrogen (BUN) and milk urea nitrogen (MUN) values in cows supplied with the yeast culture were probably associated with a high ammonia incorporation into microbial protein in the rumen, which increased protein supply for milk protein synthesis and decreased the nitrogen loss.     

Effect of tannins and saponins in Samanea saman on rumen environment,milk yield and milk composition in lactating dairy cows

The objective of this study was to investigate the effects of tannins and saponins in Samanea saman on rumen fermentation, milk yield and milk composition in lactating dairy cows. Four multiparous early‐lactating dairy cows (Holstein‐Friesian cross‐bred, 75%) with an initial body weight (BW) of 405 ± 40 kg and 36 ± 8 day in milk were randomly assigned to receive dietary treatments according to a 4 × 4 Latin square design. The four dietary treatments were unsupplemented (control), supplemented with rain tree pod (S. saman) meal (RPM) at 60 g/kg, supplemented with palm oil (PO) at 20 g/kg, and supplemented with RPM at 60 g/kg and PO at 20 g/kg (RPO), of total dry matter (DM) intake. Cows were fed with concentrate diets at a ratio of concentrate to milk yield of 1:2, and chopped 30 g/kg of urea‐treated rice straw was fed ad libitum. The RPM contained condensed tannins and crude saponins at 88 and 141 g/kg of DM respectively. It was found that s upplementation with RPM and/or PO to dairy cows diets did not show negative effect on ruminal pH, blood urea nitrogen and milk urea nitrogen concentration (p > 0.05). However, supplementation with RPM resulted in lower ammonia nitrogen (NH₃‐N) concentration (p < 0.05). In addition, propionic acid and milk production increased while acetic acid, acetic to propionic ratio, methane production, methanogens and protozoal population decreased with RPM and/or PO supplementation. Furthermore, addition of PO and RPO in the diets increased milk fat while supplementation of RPM resulted in greater milk protein and Fibrobacter succinogenes numbers (p < 0.05). The population of Ruminococcus flavefaciens and Ruminococcus albus were not affected by any treatments. The findings on the present study showed that supplementation with RPM and RPO to diets of cows improved the rumen environment and increased milk yield, content of milk protein and milk fat.     

Clinical acidosis in a Gippsland dairy herd

OBJECTIVE: To report on spontaneous clinical and subclinical acidosis in a large dairy herd, to evaluate the diets and feeding strategies involved, and to report on measures of rumen function in the cows affected. DESIGN: A Gippsland dairy herd was sampled as part of a wider randomised cross-sectional study that examined the prevalence, risk factors for, and effects of, acidosis on rumen function of dairy cattle. Three herds on the farm were involved in the study: the transition herd (cows 3 weeks prior to calving), the very fresh lactating herd (1 < days in milk < 10, herd 1) and the fresh lactating herd (10 < days in milk < 120, herd 2) including a small lame herd fed separately. The transition cows were fed 2 kg dry matter triticale per cow per day and hay with an estimated total dry matter intake of 4.8 kg per cow per day. The lactating cow diet included 6.75 kg dry matter triticale per cow per day with total concentrate fed being 8.1 kg dry matter per cow per day in the milking parlour. Silage, lucerne cubes, hay and pasture (herd 2 only) was also fed to the lactating cows with the estimated total dry matter intake for cows in herds 1 and 2 being 13.7 kg and 20.8 kg per cow per day respectively. Three primiparous and five multiparous cows in early lactation (< 100 days in milk) were randomly selected from each of two lactating herds: herds 1 and 2. Rumen fluid was sampled from each cow by both rumenocentesis and stomach tube. The rumenocentesis samples were tested for pH at the time of sampling. Stomach tube samples were frozen and subsequently tested for volatile fatty acid, ammonia, and D- and L-lactate concentration. RESULTS: In the very fresh herd, there was a high prevalence of severe lameness and scouring, coupled with a mean rumen pH 5.67, low mean total volatile fatty acid concentration 71.0 mM and high mean concentrations of L- and D-lactate, (7.71 mM and 7.31 mM), respectively. Cows in the fresh herd had moderate signs of scouring and lameness. A lame herd comprising approximately 50 cows separated from the fresh herd was also present on the farm. The mean rumen pH of the fresh herd was 5.74 and mean rumen concentrations of volatile fatty acids, ammonia, L- and D-lactate were within ranges considered normal. CONCLUSIONS: The transition diet failed to supply sufficient energy and protein for maintenance of cows of this live weight in late gestation. The diet fed to the very fresh herd was low in effective fibre and contained an excessive content of non-structural carbohydrate in the form of processed, rapidly fermentable grain. The sudden change from the transition diet to the diet fed to the very fresh herd probably also precipitated the outbreak of acidosis. This case report provides unique detail, including information on diets and rumen parameters, of an outbreak of acidosis in a pasture-fed herd.     

Effect of N fertilisation rate, energy supplementation and supplementation strategy on efficiency of N utilisation in the sheep rumen.

The effect of nitrogen (N) fertilisation (200 vs. 400 kg N ha-1 year-1) of pasture cut in the beginning (end of May) and the end (end of August) of the grazing season and of simultaneous or separated feeding of maize and grass (400 kg N ha-1 year-1) on efficiency of N utilisation in the rumen has been studied using four rumen cannulated wethers. Doubling N fertiliser rate increased grass CP production by about 60%, but induced extensive excess of rumen degradable N, reflected in high urinary urea excretion (rpearson = 0.747). The latter was lower (74% at the maximum) when feeding less fertilised or older grass or when supplementing with maize silage. Although simultaneous feeding of maize silage with grass changed patterns of rumen ammonia concentrations, no change in urinary excretion of purine derivatives was observed. Hence, faecal or urinary N excretion was unaffected by the supplementation strategy. Microbial growth efficiency was estimated from urinary excretion of purine derivatives and fermented OM. The latter was calculated from total rumen CH4 production, based on rumen fermentation stoichiometry and taking into account proportional concentrations of individual volatile fatty acids. Higher levels of intake tended to improve rumen microbial growth efficiency slightly (rpearson = 0.406), which, however, could not compensate for the reduced effective rumen DM degradability (rpearson = -0.442). The latter was apparently associated with a partial shift of the fermentation from the rumen to the hindgut, as suggested from the negative correlation (rpearson = -0.745) between faecal RNA concentrations and rumen effective degradability.