Feeding fodder beet (Beta vulgaris L.) with either barley straw or pasture silage to non-lactating dairy cows

AIMS: To determine the suitability of diets containing either approximately 85% fodder beet (Beta vulgaris L.) with barley straw or 65% fodder beet with pasture silage when fed to non-lactating dairy cows, by measuring intakes, digestibility, rumen function including microbial growth, and N excretion.

METHODS: Holstein-Friesian cows fitted with permanent rumen fistulae were fed either 65% fodder beet with pasture silage (Silage; n=8) or 85% fodder beet with barley (Hordeum vulgare L.) straw (Straw; n=8) in an indoor facility over a 9-day period, for measurement of intakes, digestibility, rumen function and urine production. The cows were adapted to the diets over 2 weeks before the indoor measurements. Feed was available for about 6 hours/day, as practiced commercially for wintering non-lactating cows.

RESULTS: Five cows fed the Straw diet had to be removed from the trial because of acute acidosis; four on Day 1 of the measurement period and one on Day 7. One cow allocated to the Silage diet refused to eat fodder beet bulbs and was also removed from the trial. Two cows fed the Silage diet were also treated for acidosis. DM intakes were lower with the Straw than Silage diets (6.4 (SE 0.4) vs. 8.3 (SE 0.5) kg/day) and organic matter (OM) digestibility was lower with the Straw than Silage diets (77 (SE 1) vs. 83 (SE 1) g/100g). The N content of the two diets was 1.14 and 1.75?g/100?g DM and there was a net loss of N by cows fed the Straw diet (?22.7 (SE 7) g/day). Rumen microbial N production was much lower in cows fed the Straw than the Silage diet (6.6 (SE 1.3) vs. 15.8 (SE 0.7) g microbial N/kg digestible OM intake). Concentrations of ammonia in rumen liquid collected on Days 5–6 were below detection limits (<0.1?mmol/L) in 36/48 (75%) samples collected from cows fed the Straw diet and in 27/48 (56%) cows fed the Silage diet. Mean urinary N excretion was lower in cows fed the Straw than the Silage diet (52.0 (SE 5.8) vs. 87.7 (SE 5.9) g/day).

CONCLUSION AND CLINICAL RELEVENCE: An over-wintering diet for dry cows comprising about 65% fodder beet with 35% pasture silage provided adequate nutrition, although there was some risk of acidosis. In contrast, the diet containing about 85% fodder beet with barley straw resulted in lower DM intakes, poor rumen function, negative N balance so that both nutrition and welfare were compromised.     

The usefulness of determining urea levels and the acidity of milk for evaluating protein nutrition in cows

Samples of blood, urine and milk were examined in 94 clinically healthy cows of 10 herds. The average milk samples and the feed ration used in these herds were also examined. The determination of urea concentration and milk acidity was evaluated as to its suitability for the assessment of the protein-glycide ratio and acid-base activity of feed ration. The determination of urea content in an average milk sample was found to be an expeditious procedure. The results of this examination can be used for the evaluation of the protein supply to cows with the same reliability as the determination of serum urea. The passage of urea from serum to milk was proportional. The correlation coefficient for the relation of both parameters was statistically highly significant (r = 0.940). According to the calculated equation of regression line (f2 = 0.734 + 0.669 X f1), the values from 2.94 to 4.10 mmol/l are approximately adequate to the reference range of serum urea from 3.30 to 5.00 mmol/l in milk used in Czechoslovakia. The acidity of milk was found to have a low sensitivity for being used with success for the determination of the acid-base activity of feed ration. The examination of the net acid-base urinary output cannot be replaced by the determination of milk acidity.     

Nitrogen metabolism in dairy cows fed restricted amounts of grass–clover silage supplemented with seeds from narrow-leafed lupin or pea

Twelve dairy cows in mid to late lactation were fed iso-nitrogenous diets (161 g CP/kg DM, forage:concentrate ratio 65:35) where rolled barley and coarsely ground seeds from either narrow-leafed lupin or field pea supplemented grass–clover silage. Feed allowance was individually restricted and fixed (18.8 ± 0.6 kg dry matter/day) throughout the experiment to avoid refusals. The experiment was of 2 × 2 change-over design and utilized a previous change-over experiment with 3 periods as covariate. Nitrogen balance was assessed by quantitative urine sampling and fecal spot sampling in eight cows whereas rumen metabolism was studied in four cannulated cows. Production of energy corrected milk was 24.3 kg/day with the lupin diet and 23.2 kg/day with the pea diet (P < 0.05). Daily milk fat yield was also higher (P < 0.05) with the lupin diet. Proportion of feed N excreted in milk did not differ between diets. Milk urea concentration, as well as the amounts of total urinary N and urinary urea were higher (P < 0.05) for the lupin diet, while urinary N proportion of feed N only tended (P = 0.08) to be higher with the lupin diet. N balance was lower with the lupin diet. Digestibilities of organic matter, neutral detergent fiber and crude protein did not differ between diets and neither did ruminal pools of these constituents. In addition, there were no differences between the diets with respect to the ruminal concentrations of NH₃-N and total volatile fatty acids, and only minor differences in ruminal pH and ruminal concentrations of iso-acids and α-amino-N. It is concluded that the higher fat content in lupins compared to peas is an advantage in typical Scandinavian home-grown rations and probably explains the higher milk yield in this experiment. Differences in protein utilization between lupins and peas are of small magnitude when fed ground without thermal processing. In practical feeding, ad libitum forage allowance may create response differences between lupin seeds and peas not observed in this experiment.     

Influence of balance of protein and energy metabolism in rumen on hypomagnesaemia in cows

This study was carried out in order to determine the influence of nitrogen excess in rumen and deficit of digestible organic matter in a feed ration for dairy cows on hypomagnesaemia at the beginning of green forage feeding. The balance of nitrogen and energy metabolism in rumen was determined using the rules of evaluation of the nutritional value of fodder (PDI system) according to the Institut National de la Recherche Agronomique (INRA), taking into consideration a potential protein synthesis from nitrogen by microorganisms in rumen (MPRN) and microbial protein synthesized from digestible organic matter (MP(RE)). It was found that an increase in the amount of rumen degradable protein (RDP) and MPRN-MPRE balance leads to a significant increase of urea nitrogen in serum (p < 0.05). An increase of total MPRN-MPRE balance in rumen results in a decrease of Mg concentration in serum. It has been demonstrated that in cows fed green forage at the end of spring (2nd half of May to 1st half of June) when the MPRN-MPRE balance is not higher than 187 g, adding 7 g or 25 g of MgO/cow/day to the same extent successfully prevents hypomagnesaemia.     

The use of the sugar beet in swine nutrition. 2. The effect of different preparation processes on the apparent prececal and fecal digestibility

With ileum cannulated sows were tested the apparent precaecal and faecal digestibility of crude nutrients from raw and thermically treated fodder sugar beets of size "Rosamona". Two samples from two different harvest years, differing extremely in the content of disaccharides were tested. The crude nutrient digestibility affected stronger by content of sucrose then by treatment. Fodder sugar beets with contents of disaccharide lower then 400 g/kg DM showed low precaecal and faecal digestibilities. A longer cooling phase decreased the feed value of steamed beets through the microbial attack in the formation of precaecal indigestible sugar alcohols (mannitol).     

Variation in selected blood plasma constituents during the post-partum and breeding periods in dairy cows

Concentrations of insulin-like growth factor-I, albumin, beta hydroxybutyrate, glucose and urea were measured in 12 plasma samples collected over 9 weeks from mid-August from each of 40 cows in four seasonal herds which calved from mid-July. These herds comprised Jersey or Holstein-Friesian animals, with each breed grazed at two stocking rates. Daily dry matter intakes (kg dry matter/cow/day), which were estimated from pasture assessments before and after grazing, ranged from 4% (low stocked Jersey herd) to 38% (high stocked Friesian herd) below recommended intakes for each breed of cow in peak lactatipn. Stocking rate was associated with a 4% reduction in liveweight for cows in the high stocked herds and a 20% reduction in daily milk production (as a proportion of the low stocked herds' liveweight and milk production).

Eight cows produced at least one blood sample with a beta hydroxybutyrate concentration of more than 1.0 mmol/l. There were 42% of samples with glucose concentrations greater than 4.1 mmol/l. These two concentrations were the maximum values classified as normal for these two metabolites by the Ruakura Animal Health Laboratory. No concentrations of the other metabolites were outside their respective normal ranges. Breed, age and individual animals usually had greater effects on the average metabolite concentrations than did stocking rate.

The greatest effect was associated with sample day, especially for insulin-like growth factor-I and urea. A significant breed x stocking rate x sample day interaction in urea concentrations indicated that changes in the feeding value of the grazed pastures available to each herd were sufficient to produce separate fluctuating patterns in the daily average concentrations.

These results showed that frequent sampling on a herd basis would be necessary to identify the significance of factors which may be contributing to sample day variation in the concentration of metabolites in the plasma of pasture-fed cows.     

Influence of zeolite A supplementation during the dry period of dairy cows on feed intake, on the macro and trace element metabolism around calving and milk yield in the following lactation

The object of the present study was to determine the influence of zeolite A, a calcium binder from the group of the aluminosilicate, on feed intake, macro and trace element metabolism as well as the milk yield in the following lactation in dairy cows. 46 cows were allotted to 2 groups (A--control group and B--experimental group). They were fed a total mixed ration (TMR) ad libitum 2 weeks before calving. Additionally the cows in group B received 90 g zeolite A/kg dry matter (DM). The individually feed intake was registered daily. The serum was analysed for Ca, Mg, and Pi (inorganic phosphate), Fe, FFA (free fatty acid) and beta-HB (hydroxybutyrate) and the plasma for the trace elements Cu, Zn, and Mn. After calving the milk yield (FCM) and the milk composition (fat, protein, lactose and urea) were analysed. Feed intake of group B, amounting to 6.2 +/- 1.3 kg DM/d was around 48% lower as compared to 12.0 +/- 1.4 kg DM/d for group A. The zeolite addition into the TMR showed a stabilizing effect on the average Ca concentration in the serum around calving. This effect led to a significantly lower Mg concentration on the day of calving and 1 day post partum. The Pi concentration was significantly lower already after the 1st week of zeolite supplementation and on the day of calving as compared to group A. There was no essential effect of zeolite A on the trace element concentration. The depression of feed intake for group B led to a significant increase of FFA one week after beginning zeolite supplementation and of beta-HB around calving. The feed intake post partum as well as the milk yield were not affected by zeolite supplementation. Because decreased feed intake of group B after zeolite supplementation and the occurred hypophosphatemia, it is not acceptable to use zeolite A in the proved dose for preventing milk fever.     

Variation in selected blood plasma constituents during the post-partum and breeding periods in dairy cows

Concentrations of insulin-like growth factor-I, albumin, beta hydroxybutyrate, glucose and urea were measured in 12 plasma samples collected over 9 weeks from mid-August from each of 40 cows in four seasonal herds which calved from mid-July. These herds comprised Jersey or Holstein-Friesian animals, with each breed grazed at two stocking rates. Daily dry matter intakes (kg dry matter/cow/day), which were estimated from pasture assessments before and after grazing, ranged from 4% (low stocked Jersey herd) to 38% (high stocked Friesian herd) below recommended intakes for each breed of cow in peak lactation. Stocking rate was associated with a 4% reduction in liveweight for cows in the high stocked herds and a 20% reduction in daily milk production (as a proportion of the low stocked herds' liveweight and milk production). Eight cows produced at least one blood sample with a beta hydroxybutyrate concentration of more than 1.0 mmol/l. There were 42% of samples with glucose concentrations greater than 4.1 mmol/l. These two concentrations were the maximum values classified as normal for these two metabolites by the Ruakura Animal Health Laboratory. No concentrations of the other metabolites were outside their respective normal ranges. Breed, age and individual animals usually had greater effects on the average metabolite concentrations than did stocking rate. The greatest effect was associated with sample day, especially for insulin-like growth factor-I and urea. A significant breed x stocking rate x sample day interaction in urea concentrations indicated that changes in the feeding value of the grazed pastures available to each herd were sufficient to produce separate fluctuating patterns in the daily average concentrations. These results showed that frequent sampling on a herd basis would be necessary to identify the significance of factors which may be contributing to sample day variation in the concentration of metabolites in the plasma of pasture-fed cows.     

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.     

Natural contamination of dietary rice straw with zearalenone and urinary zearalenone concentrations in a cattle herd

The present study was conducted to 1) identify the natural source of feed contamination by zearalenone (ZEN), which was suspected to have caused persistently increased urinary ZEN concentrations in one of our experimental cattle herds, and 2) evaluate the effects of intervention against this source of contamination. As an experimental model, a fattening Japanese Black cattle herd showing persistently increased urinary ZEN concentrations was identified. Urinary ZEN concentrations of cows fed with new rice straw (experimental group, n = 6) vs. cows that continued to feed on the old rice straw (control group, n = 4) were measured at the start (d 1) and at 2 wk (d 14) after the onset of feeding with straw. In addition, the ZEN concentration in feed and water samples was measured by using both the ELISA and HPLC methods. Furthermore, isolation and identification of fungi from rice straw and concentrate feed samples were performed. The urinary ZEN concentration [ZEN (pg/mL)/creatinine (mg/mL) = pg/mg of creatinine] of cows fed with new rice straw was significantly (P < 0.05) less (843 pg/mg of creatinine) than that of cows fed with old rice straw (15,951 pg/mg of creatinine). On both d 1 and 14, the ZEN concentrations of old rice straw were greater than those of new rice straw. In addition, fungal colonies were observed in the culture media that was obtained from the old rice straw suspected of ZEN contamination, but not in the culture media from new rice straw or other feed samples. In conclusion, our field trials clearly indicate that the rice straw fed to the cows was naturally contaminated with ZEN, and that the monitoring of urinary ZEN concentrations could prove to be a useful tool for detecting the exposure of cattle to ZEN contamination at the farm level.     

复合饲料添加剂对荷斯坦奶牛生产性能及血清生化指标的影响

文章旨在探究复合型饲料添加剂对荷斯坦奶牛生产性能、血清生化指标的影响。采取单因素试验设计,将18头身体健康、体况相近的泌乳中期荷斯坦奶牛随机分为2组,分别为对照组、试验组（添加复合型饲料200 g/d）,其中每组设置3个重复,每个重复3头牛,整个试验周期为30 d。于试验期第15和30天采集奶牛乳样及空腹血样,用于测定其产奶性能及血清生化指标。结果显示：在第15和30天,复合饲料添加组奶牛血清白蛋白、尿素氮、甘油三酯、胆固醇、葡萄糖、谷草转氨酶、谷丙转氨酶较对照组均有所上升,但差异不显著（P＞0.05）|但试验组血清中总蛋白含量在15 d和30 d时均显著高于对照组（P＜0.05）|复合饲料添加剂组在第15和30天奶牛产奶量为（21.55±4.03）kg、（22.63±1.76）kg,与对照组相比,分别提高9.27%和14.2%（P＜0.05）|除此之外,试验组奶牛乳样中体细胞数和尿素氮水平均低于对照组,但只有尿素氮显著降低（P＜0.05）。综上所述,复合饲料添加剂具有提高荷斯坦奶牛中后期产奶量,增加血清蛋白含量,改善乳品质的作用。 [关键词]复合饲料添加剂|荷斯坦奶牛|生产性能|血清生化指标     

Does body size of dairy cows,at constant ratio of maintenance to production requirements,affect productivity in a pasture‐based production system?

This study compared productivity of dairy cows with different body weight (BW), but a constant ratio of maintenance to production requirements in their first lactation, in a pasture-based production system with spring calving. Two herds, Herd L (13 and 14 large cows in 2003 and 2004 respectively; average BW after calving, 721 kg) and Herd S (16 small cows in both years; 606 kg) [Correction added after online publication 14 January 2011: 16 small cows in both years; 621 kg was changed to 16 small cows in both years; 606 kg], all in their second or following lactations, were each allocated 6 ha of pasture and rotationally grazed on 10 parallel paddocks with equal herbage offer and nutritional values. Winter hay, harvested from the same pastures, was offered ad libitum in the indoor periods in a tied stall barn. Each herd received, per lactation and year, approximately 2000 kg dry matter (DM) of concentrates and of fodder beets, equally distributed to every individual. Indoors, the L-cows ingested more DM than the S-cows (18.7 vs. 16.3 kg DM/cow per day; p < 0.01), but DM intake per 100 kg of metabolic BW was similar (13.0 vs. 13.1 kg DM/cow per day). Estimates based on the n-alkane technique gave similar results on pasture (17.9 vs. 15.5 kg DM/cow per day; p < 0.001). Roughage intakes per 100 kg of metabolic BW, at 13.5 kg DM/cow per day, were similar. Mean annual yield of energy-corrected milk (ECM)/ha was slightly higher for the S-herd than the L-herd (13,026 vs. 12,284 kg) but was associated with a higher stocking rate (on average +20%) for the S-herd. Feed conversion efficiency (1.2 vs. 1.3 kg ECM/kg DM intake) and overall milk production efficiency (45.3 vs. 47.3 kg ECM/kg metabolic BW) were similar in L- and S-cows. Thus, both dairy cow types were equally efficient in utilising pasture-based forage.     

The influence of administration of biotin and zinc chelate (Zn-methionine) to cows in the first and second trimester of lactation on their health and productivity

In cattle, the prevention of diseases might be possible using dietary methods, with nutritional optimization of feed rations. For years significant influence has been associated with the addition of biotin, methionine and zinc (each given individually, or as chelate - Zn-methionine). The aim of this study was to evaluate the influence of biotin or biotin + Zn-methionine additives on the health and performance of cows, in the first and second trimester of lactation. This study was carried out in 3 groups of cows, 30 animals in each group. In the first group cows were fed the usual fodder used on the farm. In the second group biotin at 10 mg/day/cow was added. In the third group both biotin at 10 mg/day/cow and Zn-methionine at 5 g/day/cow were added. The administration of biotin increased the milk yield and reduced the occurrence of retained placenta, as well as endometritis puerperalis. However, the high doses of biotin suppressed ovulation and oestrus symptoms in the investigated cows (low progesterone levels on days 15, 21 and 45 after calving). Zn-methionine in comparison to biotin had a lower effect on the milk yield in the cows. Moreover, its supplementation improved the milk content, as well as some of the blood parameters; it also decreased the number of somatic cells in milk. The concurrent administration of biotin and zinc-methionine seemed to be a good method for the prophylaxis of subacute mastitis and for the improvement of the high yielding dairy cows' productivity.     

Chromium improves production and alters metabolism of early lactation cows in summer

Metabolic demands of early lactation introduce enormous challenges to dairy cows when coincided with environmental stresses. The objective of this study was to determine effects of a chromium (Cr) supplement on feed intake and blood indicators of nutrient metabolism in early lactation cows in summer. Fifteen Holstein cows at 38 ± 6 days in milk were grouped based on parity and randomly assigned to three supplemental doses of 0, 0.05 and 0.10 mg Cr/kg of BW^0.75. Cows received a basal mixed ration with a forage to concentrate ratio of 57.7:42.3, twice daily at 09:00 and 16:00 h for 9 weeks. The first 2 weeks were for adaptation, and the following 7 weeks were for weekly sampling and data collection. The Cr supplement (a Cr–methionine product with 10% Cr and 90% Met from a compound containing one atom of Cr and three molecules of Met) was mixed with 100 g of ground corn and top dressed with the morning feed. The average ambient temperature–humidity index was 77.7 units during the study. Dry matter intake increased from 21.8 to 24.2 and 23.7 kg/day when 0.05 and 0.10 mg Cr/kg BW^0.75 was provided respectively. Milk output of energy, fat, protein and total solids increased by providing Cr at 0.05 mg but not 0.10 mg/kg BW^0.75. Both doses of Cr increased milk protein content, but the higher Cr dose reduced feed efficiency compared with control. While rectal temperature and body condition score were unaffected, cows receiving 0.05 mg and not 0.10 mg Cr/kg BW^0.75 tended to have greater respiration rate than control cows. Blood insulin and non‐esterified fatty acids concentrations and the insulin to glucagon ratio decreased, and serum albumin increased when cows received 0.05 mg of Cr/kg BW^0.75. Blood glucose, glucagon, insulin‐like growth factor‐1, total protein, globulins, urea, BHBA, triglycerides, cholesterol, cortisol, progesterone, and high‐ and very low‐density lipoproteins were not affected. Therefore, supplemental Cr supply at 0.05 and 0.10 mg/kg BW^0.75 improved feed intake, only at 0.05 mg/kg BW^0.75 increased milk secretion, and mainly at 0.05 mg/kg BW^0.75 altered peripheral nutrient metabolism in early lactation Holstein cows under high ambient temperatures.     

Effect of different levels of dietary nitrogen supplementation on the relative blood urea nitrogen concentration of beef cows

The objective of this study was to determine if individual beef cows in a herd have an inherent ability to maintain their blood urea nitrogen (BUN) concentration when exposed to different levels of dietary nitrogen supplementation. Ten Hereford and 12 Nguni cows, aged between 2 and 16 years, were utilized in two crossover experiments. In the first experiment, cows were exposed to two diets: a balanced diet with a crude protein (CP) level of 7.9% and a modified diet with a CP level of 14%, formulated by adding 20 kg of feed grade urea per ton of the balanced diet. At the end of the first crossover experiment, cows received the balanced diet for 1 week. The second component utilized the same cows wherein they were fed the balanced diet in addition to another modified diet containing only 4.4% CP. Blood urea nitrogen concentration was measured 22 times (twice weekly) from each cow during both components of the study. A linear mixed-effects model was used to assess whether baseline BUN concentration (measured 1 week before onset of the study) was predictive of subsequent BUN concentration in individual cows. Breed, cow age, body condition score, and body mass were also evaluated for their effects on BUN concentrations. Albumin, beta hydroxybutyric acid (BHBA), glucose, and total serum protein (TSP) were compared between diets within each breed. Baseline BUN concentration was a significant predictor of subsequent BUN concentration in individual cows (P = 0.004) when evaluated over both components of the study. Breed (P = 0.033), the preceding diet (P < 0.001), current diet (P < 0.001), and the week during which sampling was performed (P < 0.001) were also associated with BUN concentration. Results suggest that beef cattle (within a herd) have an inherent ability to maintain their BUN concentration despite fluctuations in levels of available dietary nitrogen.

     

Effect of dietary potassium and anionic salts on acid–base and mineral status in periparturient cows

Dry cow diets based on grassland forage from intensive production contain high amounts of K and could be responsible for a reduced ability to maintain Ca homoeostasis. The aim of this study was to determine whether a moderate anionic salt supplementation to a forage‐based pre‐calving diet with varying native K content affects the mineral and acid–base status in transition cows. Twenty‐four dry and pregnant Holstein cows, without antecedent episodes of clinical hypocalcemia, were assigned to two diets during the last 4 weeks before estimated calving date. Twelve cows were fed a hay‐based diet low in K (18 g K/kg DM), and 12, a hay‐based diet high in K (35 g K/kg DM). Within each diet, six cows received anionic salts during the last 2 weeks before the estimated calving day. After calving, all cows received the high K diet ad libitum. Blood samples were taken daily from day 11 pre‐partum to day 5 post‐partum. Urine samples were taken on days 7 and 2 pre‐partum and on day 2 post‐partum. The anionic salt did not alter feed intake during the pre‐partum period. Serum Ca was not influenced by the dietary treatments. Feeding pre‐partum diets with low K concentrations induced a reduced metabolic alkalotic charge, as indicated by reduced pre‐partum urinary base–acid quotient. Transition cows fed the low K diet including anionic salts induced a mild metabolic acidosis before calving, as indicated by higher urinary Ca, lower urinary pH and net acid–base excretion. Although serum Ca during the post‐partum period was not affected by dietary treatment, feeding a low K diet moderately supplemented with anionic salts to reach a dietary cation–anion difference close to zero permitted to obtain a metabolic response in periparturient cows without altering the dry matter intake.     

Effects of high ambient temperature and restricted feed intake on urinary and plasma 3-methylhistidine in lactating Holstein cows

Three experiments were performed to examine the effects of high ambient temperature and feed restrictions on urinary 3‐methylhistidine (3MH) excretion and plasma 3MH concentrations as a marker of myofibrillar proteolysis in lactating Holstein cows. In a crossover design, four cows were maintained during two 14‐day treatment periods with ad libitum feed intake under constant moderate (18°C) or high (28°C) ambient temperature (Experiment 1), with ad libitum or 70% ad libitum feed intake under constant moderate temperature (Experiment 2), and with 70% ad libitum feed intake under constant moderate or high ambient temperature (Experiment 3). The total digestible nutrients intake was decreased (P < 0.01) under high ambient temperature (Experiment 1) or feed restriction (Experiment 2). Across experiments, urinary 3MH excretion during days 10–14 of each treatment period was not different among treatments. However, the plasma 3MH concentrations at day 14 of treatment were increased significantly under high ambient temperature with subsequent reduced feeding (P < 0.01) or moderate temperature with feed restriction (P < 0.05), and were increased slightly (P = 0.11) under high ambient temperature alone. These results show that the plasma marker of myofibrillar proteolysis in lactating dairy cows was increased at day 14 of treatments of high ambient temperature with subsequent reduced feeding, moderate temperature with feed restriction, or high ambient temperature alone.     

Effects of feeding frequency on the performance and welfare of mature Hereford cows and their progeny

A study was conducted to assess the effects of daily feeding (D) vs. feeding every third day (3D) on the performance of suckler cows and calves. In treatment 3D, the cows received the entire three-day feed portion on the first feeding day. The feeding regimens were imposed during the indoor feeding period in cold circumstances with grass silage and hay offered in the proportions of 1 : 1 on an energy basis for the cows. Thirty-two mature Hereford cows with an initial live weight (LW) of 787 kg and body condition score (BCS) of 3.33 were selected for the experiment. The experiment consisted of a winter feeding period and a grazing period averaging 225 and 96 days, respectively. Indoors the cows received a daily average 94 MJ metabolizable energy. The in vivo digestibility of dietary organic matter was similar in both treatments. No significant differences between the treatments were observed in cow LW, BCS, milk production and calf LW. Thirty-one cows were observed to be pregnant after the mating period. In the 3D treatment the serum concentrations of urea and long-chain fatty acids were increased on the third day after feeding compared to first and second days throughout the experiment, possibly due to activation of lipolysis and proteolysis. The 3D cows spent on average more (P < 0.001, 9.1% vs. 4.5%) time lying and less time (P < 0.05, 32.9% vs. 40.1%) outdoors than the D cows. On the basis of the results, feeding every third day is an acceptable winter feeding strategy for mature suckler cows if the cows receive enough energy for maintenance and milk production.     

Effect of exogenous estradiol on plasma concentrations of somatotropin, insulin-like growth factor-I, insulin-like growth factor binding protein activity, and metabolites in ovariectomized angus and braham cows

To determine the effect of breed and estradiol-17β on selected hormones and metabolites, ovariectomized (3 mo) Angus (n = 14) and Brahman (n = 12) cows were paired by age and body weight and randomly assigned as either nonimplanted controls (CON) or implanted with estradiol (E2) for 45 d. After Day 7 and through Day 42, plasma concentration of somatotropin was greater for E2 than CON cows (treatment X day, P < 0.05). During an intensive blood sampling on Day 36, E2 cows tended (P < 0.10) to have greater somatotropin pulse amplitudes than CON cows, but other parameters of somatotropin release were not affected (P > 0.10) by E2 treatment. The effect of breed was apparent on Day 36 as Brahman cows had greater (P < 0.05) somatotropin pulse amplitude, basal secretion, and mean concentration than Angus cows. Overall, plasma concentration of IGF-I was greater (P < 0.01) for E2 than CON cows (158.3 vs. 104.2 ng/ml) and was greater for Brahman than Angus cows (164.1 vs. 98.4 ng/ml). However, there was a trend (P < 0.10) for a treatment X breed X day interaction for IGF-I (i.e., the magnitude of increase in IGF-I concentration was greater in E2-Angus than E2-Brahman cows). After Day 7 and through Day 42, total plasma IGF binding protein (IGFBP) activity was greater (P < 0.01) for E2 than CON cows. Ligand blotting revealed at least five forms of IGFBP activity, and E2 cows had greater (P < 0.05) binding activity of IGFBP-3 and the 30- and 32-kDa IGFBP than CON cows. Brahman cows had greater (P < 0.05) IGFBP-3 and the 32-kDa IGFBP than Angus cows. After Day 14 and through Day 42, concentration of urea nitrogen (PUN) was greater (P < 0.001) for CON than E2 cows (treatment X day, P < 0.001). Brahman had greater (P < 0.01) PUN than Angus cows (16.6 vs. 14.2 mg/dl). Plasma concentration of glucose was greater (P < 0.01) for E2 than CON cows (78.9 vs. 76.4 mg/dl) but was not affected (P > 0.10) by breed. In summary, these data suggest that some, but not all, of the positive effects of estradiol on peripheral concentration of IGF-I and IGFBP activity can be attributed to increased somatotropin. Moreover, breed influenced basal and E2-induced secretion of somatotropin and IGF-I such that differences between Brahman and Angus cows in plasma IGF-I concentrations were abated within 3 wk of estradiol implantation. Thus, breed influences the metabolite and hormonal response of cattle to estrogenic implants.