Peripartal calcium homoeostasis of multiparous dairy cows fed rumen‐protected rice bran or a lowered dietary cation/anion balance diet before calving

Milk fever is one of the most important metabolic diseases in dairy cattle. Reducing the dietary cation/anion balance (DCAD) with anionic salts is a common prevention strategy. However, many small European farms cannot use total mixed rations (TMR) in the close‐up period. Including anionic salts in compound feeds can result in feed refusals and moderate inclusions to preserve feed palatability results in insufficient DCAD reduction. Rumen‐protected rice bran induces the adaptation of Ca metabolism in dairy cows by a reduction of Ca intake and by a reduction of the availability of dietary Ca. In the presence of a negative control, rumen‐protected rice bran (2.8 kg/day) was compared with a lowered DCAD diet (from 269 to 4 meq/kg DM) in their effect to prevent milk fever. In a randomized block design, 45 multiparous Holstein cows joined the trial sequentially from 21 days before the expected calving date and were observed until the 8th week of lactation. Feed and nutrient intakes were recorded, and Ca, P, Mg in serum and urine, urine pH, serum NEFA and milk production in early lactation were compared. Feeding rumen‐protected rice bran before calving improved the recovery of calcaemia after calving and had a positive effect on DMI after calving. The moderately low DCAD diet did not positively influence serum Ca at calving. Calcaemia recovered even later than in control, and cows showed reduced DMI post‐calving and higher NEFA levels in the first 36 h after calving. This moderate reduction of DCAD did not provide an intermediate prevention level indicating that DCAD needs to be reduced to the recommended levels to prevent milk fever. Rumen‐protected rice bran may be a suitable feed to reduce hypocalcaemia post‐partum and can be included in pre‐calving compound feeds representing a palatable alternative to anionic salts.     

Effect of diets containing sulfate or chloride-based anionic salts,fed to grazing prepartum dairy cows,on concentrations of Ca in plasma,disease incidence and milk yield

AIMS: To compare the effect of two partial mixed ration diets containing either sulfate or chloride-based anionic salts, fed to grazing prepartum dairy cows, on concentrations of Ca, Mg, P and beta-hydroxybutyrate (BHB) in plasma, disease incidence and milk yield during the early postpartum period.

METHODS: The study was conducted on a seasonal-calving grazing dairy farm located in Benton (MO, USA). In August 2016, two groups of 200 cows were randomly assigned at 30 days before expected parturition to receive either a sulfate or chloride-based anionic diet, to achieve a dietary cation–anion difference (DCAD) of ?25?mEq/kg DM. Cows were fed partial mixed rations to provide 50% of their DM intake, with 50% provided by grazing fescue pasture. Urine samples were collected from 20 cows from each group once a week for 5 weeks until calving for pH assessment. At parturition, 42 cows per group were selected at random and blood samples collected on Days 1, 2, 3 and 7 postpartum. The study continued until 100 cows per group calved. Health events and cumulative milk yield until 30 days postpartum were recorded. Concentrations of Ca, P, and Mg in plasma at Days 1, 2, 3, and 7, and BHB in plasma at Day 7 postpartum were assessed.

RESULTS: Mean urine pH was lower in cows in the chloride than sulfate group (p≤0.06) on four of five sampling occasions. Mean concentrations of Ca in plasma on Day 1 were 2.00 (95% CI=1.94–2.05) and 1.91 (95% CI=1.88–1.97) mmol/L for the chloride and sulfate groups, respectively (p=0.15), and on Day 3 were 2.03 (95% CI=1.97–2.08) and 1.90 (95% CI=1.84–1.96) mmol/L, respectively (p=0.038). Concentrations of Mg, P and BHB in plasma and incidence of diseases postpartum were similar in both groups (p>0.05). There were no cases of clinical hypocalcaemia in either group.

CONCLUSIONS AND CLINICAL RELEVANCE: Prepartum cows fed a partial mixed ration with a negative DCAD containing chloride-based anionic salts and free access to a fescue pasture had lower prepartum urine pH, and higher concentrations of total Ca in plasma during the first week postpartum, than cows receiving a partial mixed ration containing sulfate-based anionic salts.     

Effect of parity number on the dry matter intake of dairy cows during the first week after calving

We investigated the effect of parity number on the dry matter intake (DMI) of cows during the first week after calving. Eighty‐three cows were evaluated from 14 days before to 7 days after calving. DMI and milk yield were measured for 7 days after calving, and the calving score was measured. Blood samples were collected throughout the experiment. The average DMI during the first week after calving was reduced in the first‐lactation heifers and high‐parity number cows. A quadratic relationship between the parity number and the DMI was observed. The first‐lactation heifers had lower prepartum serum total protein (TP) concentration and milk yield, higher prepartum serum nonesterified fatty acid (NEFA) concentration and calving score than the multiparous cows. The recovery rate of serum calcium (Ca) after calving was slow in the cows in the parity 6. The DMI was positively affected by the serum Ca concentration after calving, milk yield, and prepartum serum TP concentration and was negatively affected by the calving score and prepartum serum NEFA concentration. We conclude that the DMI immediately after calving tends to be lower in first‐lactation heifers and high‐parity number cows, but factors that reduce the DMI differ according to parity number.     

Low potassium diets with different levels of calcium in comparison with different anionic diets fed to prepartum dairy cows: Effects on sorting behaviour,total tract digestibility,energy metabolism,oxidative status and hormonal response

This study investigated the effects of low potassium diets with different levels of Ca compared to two diets low in dietary cation–anion difference (DCAD) fed prepartum as a strategy to prevent hypocalcemia on sorting behaviour, total tract digestibility, oxidative status and energy and protein metabolism of transition cows. Forty-eight pregnant dairy cows were assigned to 4 treatment groups: Low Ca, low K (LCLK), High Ca, low K (HCLK), Supplementation with anionic mineral mixture (AMS) supplementation with SoyChlor (CAS). After parturition, all animals were fed a standard postpartum diet. Data were collected until 21 DIM. Prepartum urinary pH was significantly reduced by the low DCAD diets, while postpartum Ca homeostasis was affected by the HCLK ration. Feeding AMS induced sorting against particles <1.18 mm in favour of particles >19 mm prepartum. In contrast, cows fed CAS showed an increase in selective consumption of fine particles and sorted against longer particles similar to the HCLK and LCLK groups. Postpartum sorting activity was not affected by the dietary treatments. After calving, apparent digestibility of NDF was significantly reduced in the HCLK group. Prepartum, we observed effects on serum concentrations of non-esterified fatty acids were higher and insulin sensitivity was lower in the AMS group. Blood urea nitrogen (BUN) was decreased in cows fed the CAS ration. Postpartum, we found serum protein to be decreased with the low DCAD diets while BUN was decreased in the CAS group. The low DCAD rations increased prepartum serum malondialdehyde concentrations, while postpartum total antioxidant capacity was lower in the HCLK and the AMS group. From these data, we conclude that AMS decreased prepartum intake due to compromised palatability. Intermediate protein metabolism was affected by the low DCAD diets, while parameters of oxidative stress were probably affected by acid–base balance and Ca homeostasis.     

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

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

Milk fever in dairy cows: a review of pathophysiology and control principles

The periparturient or transition period of 4 weeks before and 4 weeks after calving is characterised by a greatly increased risk of disease. Hypocalcaemia around calving is a risk factor for many of these diseases and is an indirect risk factor for increased culling. The incidence of clinical hypocalcaemia (milk fever) in the field generally ranges from 0-10%, but may exceed 25% of cows calving. In research trials conducted on milk fever the incidence has approached 80% of cows calving. Homeostasis of calcium (Ca) is regulated by calcitonin, parathyroid hormone and 1,25(OH)(2) vitamin D(3). Age increases the risk of milk fever by approximately 9% per lactation. Control of milk fever has revolved around stimulation of homeostatic mechanisms through feeding a pre-calving diet low in Ca. More recently, the role of the dietary cation anion difference (DCAD) in the prevention of Ca disorders has been examined, both by field research and meta-analysis. The most appropriate form of the DCAD equation has been contentious, but recent meta-analyses have shown that the equation (Na(+)+K(+))-(Cl(-)+S(2-)) is most effective for predicting milk fever risk. Decreased risk of milk fever is linear with DCAD, whereas the effect of DCAD on urinary pH is curvilinear. A pivotal role of providing dietary magnesium (Mg) before calving has been confirmed by meta-analysis, and a quadratic effect of Ca on milk fever risk was found with a peak occurring with dietary levels of 1.1-1.3% of dry matter. Risks of milk fever increase with increased dietary phosphorus (P) fed pre-calving and with increasing days of exposure to a pre-calving diet. Meta-analysis has revealed that the important roles of dietary Ca, Mg and P, as well as the duration of exposure to the pre-calving diet in milk fever control strategies are independent of DCAD. Studies on the effect of exposure to well designed pre-calving diets have shown that substantial improvements in production, reproduction and animal health can be made but further examination of the influence of the period of exposure to different diets is warranted.     

Metabolic Responses of Periparturient Holstein Cows and Heifers Supplemented with Chromium Picolinate

Thirty-four Holstein cows, 18 primiparous and 16 multiparous, were used to determine the effects of supplemental Cr on carbohydrate and lipid metabolism during the transition period. From approximately 3 wk prior to anticipated calving date until parturition, Cr-treated cows were given 51 mg Cr picolinate via a gelatin capsule bolus three times weekly, equivalent to an average daily intake of approximately 2 ppm Cr. Control cows were given empty gelatin capsules. All cows were fed total mixed rations, with one ration fed to dry cows, a second to lactating cows for wk 1 of postpartum (transition), and a third to lactating cows thereafter. Blood samples were collected via jugular venipuncture at 1, 2, and 3 wk prior to anticipated calving date as well as immediately following calving, 3 d post calving, and 1, 2, and 3 wk post calving. Samples were analyzed for glucose, insulin, and nonesterified fatty acids (NEFA). Within 1 wk prior to calving, a frequently sampled intravenous glucose tolerance test was performed, and blood plasma samples were analyzed for concentrations of glucose and insulin. Plasma glucose response to the frequently sampled intravenous glucose tolerance test was evaluated by calculating the half-life and fractional turnover rate for the period from 2 to 19 min after glucose infusion. Supplemental Cr did not affect circulating concentrations of glucose, insulin, or NEFA (P>0.1). Plasma NEFA concentrations were greater in primiparous cows (P<0.01) throughout the experiment, with the difference being most apparent during the 3 wk postpartum. Glucose concentrations reached a greater peak at time of calving in primiparous cows than in multiparous cows (P=0.07). There was an increase in glucose clearance rate (P=0.06) and a trend toward decreased glucose half-life (P<0.1) in primiparous cows supplemented with Cr. Insulin peak concentrations were unaffected by treatment or parity (P>0.1). Data suggest that Cr supplementation may alter carbohydrate metabolism in primiparous cows during the transition period.     

Studies of the transition cow under a pasture-based milk production system: metabolic profiles

This study describes the effect of parity (multiparous versus primiparous) and body condition score (BCS) at calving (<3 or > or =3; scale 1-5) on variations of BCS, body weight (BW) and metabolic profiles in Holstein cows grazing on improved pastures. Forty-two cows were studied (21 multiparous and 21 primiparous) from 2 months before to 3 months after calving. BCS, BW and milk production were measured every 2 weeks. Blood samples were taken every 2 weeks to determine total protein, albumin, urea, non-esterified fatty acids (NEFA), beta-hydroxybutyrate (BHB), cholesterol, aspartate aminotransferase (AST), calcium, phosphorus and magnesium. Primiparous cows had lower BCS during the early postpartum (PP) period and produced less milk than multiparous. In primiparous cows NEFA concentrations were higher during the early postpartum period; BHB levels were similar in both categories during this period. Primiparous cows showed a more unbalanced metabolic profile than multiparous cows, reflecting that they are recovering from the loss of BCS after calving with less success.     

Increasing selenium supply during the close-up dry period improves nutrient metabolism and attenuates inflammatory response after calving in dairy cows

The objective of this study was to investigate whether feeding selenium (Se)-replete cows a Se-yeast supplement in late pregnancy affects nutrient metabolism and inflammatory response during the periparturient period. Twenty cows were randomly assigned to two groups with 10 cows each. Cows in one group received Se-yeast at 0.3 mg Se/kg DM during the last 4 weeks before calving in addition to fed a TMR containing supplemented sodium selenite at 0.3 mg Se/kg DM (Se-yeast), while cows in another group were only fed a TMR containing supplemented sodium selenite at 0.3 mg Se/kg DM (Control). Blood samples were collected and analyzed for nonesterified fatty acids (NEFA), β-hydroxybutyrate (BHBA), glucose, insulin, tumor necrosis factor-α (TNF-α), interleukin (IL)-1β, IL-6, serum amyloid A (SAA), haptoglobin (Hp), and albumin. In control cows, plasma NEFA, IL-1β, IL-6, SAA, and Hp levels increased after calving, but glucose, insulin, and albumin levels decreased after parturition. Se-yeast supplemental cows had lower postpartum concentrations of NEFA, TNF-α, IL-1β, IL-6, SAA, and Hp, and higher postpartum levels of glucose, insulin, and albumin compared with control cows. The results indicate that feeding Se-replete cows a Se-yeast supplement in late pregnancy improves nutrient metabolism and attenuates the inflammatory response after calving.     

Pre-partum monensin supplementation improves body reserves at calving and milk yield in Holstein cows dried-off with low body condition score

The objective of this study was to determine the effect of a monensin controlled-release capsule administered intraruminally at drying-off on body condition score (BCS) at calving, milk yield, fertility and concentration of energy-related blood metabolites in Holstein cows dried-off with low BCS (< or = 3.0, scale 1 to 5 with a 0.25 point of increment). Between July and August, 2001, 220 cows from parity 2 or more and dried-off 50-70 days before expected parturition, with a BCS < or = 3.0 were randomly assigned to either a treatment group (n=110; oral capsule of monensin releasing 335 mg/day for 95 days) or a control group (no capsule, n=110). At assignment, on day 21 before expected parturition, at calving, and at 7, 14, and 21 days in milk a blood sample was obtained from a random sub sample of 10 cows per group. Effects of monensin on serum NEFA, BHBA and glucose were measured. Milk yield, milk fat and protein content (%) at DHIA test days during the entire lactation, 305 ME milk production and reproductive responses were compared. Monensin significantly improved BCS at calving, increased milk yield at test days 4 and 8, decreased the percentage of milk protein, did not change the percentage of milk fat, and decreased NEFA and BHBA during the post-partum period.     

Effects of first postpartum progesterone rise,metabolites, milk yield,and body condition score on the subsequent ovarian activity and fertility in lactating Holstein dairy cows

Seventy multiparous healthy lactating Holstein cows (fat-corrected milk yield = 7,561.8 kg) were monitored from 14 days before to 70 days after calving. Transrectal ultrasound scanning was performed twice weekly from 7 to 65 days postpartum. Blood samples were also collected twice weekly to measure serum P₄ and biweekly to detect serum β-hydroxybutyrate (βHB) and nonesterified fatty acid (NEFA) concentrations. Body condition score (BCS) was taken biweekly after calving. Based on the serum P₄ profile of 59 cows (11 cows were excluded due to the occurrence of postpartum diseases) studied, 27 (45.8%) had normal ovarian activity, while 21 (35.6%), six (10.1%), three (5.1%), and two (3.4%) had delayed ovulation (DOV), prolonged luteal phase (PLP), short luteal phase (SLP), and cessation of ovarian activity, respectively. Cows with PLP had an earlier ovulation compared to that of cows with normal ovarian activity (23.16 ± 4.02 vs 31.9 ± 8.35 days; P < 0.05). PLP cows also had a greater mean ± standard deviation peak milk yield (44.2 ± 5.8 vs 37.2 ± 5.7 kg/day, 75 days postpartum; P < 0.05) than cows with normal postpartum ovarian activity. The PLP group also had greater milk production in the previous lactation period. Logistic regression analysis indicated that cows with P₄ concentration ≥1 ng/ml on day 24 after calving were more at risk for PLP by 1.1 for each 1 kg increase in mean peak milk yield during 75 days after calving. BCS was lower in cows with DOV compared to that of cows with normal ovarian activity at any time after calving (P < 0.05). Serum βHB concentrations in DOV cows were significantly higher than that of normal cows on day 42 after calving (0.69 ± 0.29 vs 0.54 ± 0.12 mmol/L, P < 0.05). No significant difference was found in the mean concentrations of NEFA between cows in different groups at any time after calving (P > 0.05). The concentrations of P₄ on days 28 and 31 were negatively correlated with βHB concentration on day 42 after calving in cows with normal ovarian activity (R = −0.44, P = 0.02). In conclusion, these findings suggest that early ovulation and hence early postpartum P₄ rise in addition to the high milk production could partly be responsible for the occurrence of PLP in dairy cows.     

Effect of fat supplementation during transition period on plasma leptin and non‐esterified fatty acid concentrations in Holstein cows

The objective of this experiment was to investigate the effect of fat supplementation during the transition period on pre and postpartum body weight (BW), body condition score (BCS), non‐esterified fatty acids (NEFA), glucose and leptin concentrations in Holstein cows. Holstein cows (n = 15) received a low fat diet (LF; 1.61 Mcal net energy for lactation (NEL)/kg of dry matter [DM]), moderate fat diet (MF; 1.68 Mcal NEL/kg DM) or a high fat diet (HF; 1.74 Mcal NEL/kg DM) for 4 weeks prior to calving. All cows were fed similar lactation diets ad libitum (1.74 Mcal NEL/kg DM) for 30 days after calving. Increasing diet energy density during transition period had no effect on prepartum DMI, BCS, BW, glucose and NEFA concentrations (P > 0.05); but leptin concentrations and energy balance (EB) were affected by treatments (P < 0.05). Animals fed HF had less plasma leptin prepartum. After parturition, BW, milk production, milk fat, protein, urea nitrogen and plasma glucose concentrations were affected by prepartum diets (P < 0.05). Fat supplementation prepartum did not affect postpartum NEFA. In conclusion, prepartum fat supplementation decreased leptin concentration prepartum.     

Use of Anionic Salts with Grazing Prepartum Dairy Cows

Twenty multiparous and four primigravid Holstein cows were utilized in a completely random design to characterize the influence of decreasing prepartum dietary cation-anion difference (DCAD) from +388 to +183 meq/kg diet on DMI, prepartum blood profiles, and postpartum milk yield and composition of dairy cows grazed during the prepartum period. Treatments began on wk −4 prepartum, continued through calving, and consisted of 1) pasture and grain pellet without anionic salts (control; +388 meq/kg) or 2) pasture and grain pellet containing anionic salts (AS) (+183 meq/kg). Prepartum cows were rotationally grazed as a single group and individually fed pellets twice daily at a rate of 0.5% of BW/d. Blood and urine samples were collected on wk −4, −2.5, and −1 prepartum and analyzed for Ca, Mg, K, Na, and Cl concentrations. Urine samples were also analyzed for pH. Chromic oxide was dosed twice daily during the last 4 wk of gestation and again for 10 d during wk 4 and 12 postpartum for estimation of intake. Cows calved on pasture and were then integrated into the regular milking herd and fed a total mixed ration (TMR). Daily milk yield and weekly milk samples were collected through wk 14 of lactation. Prepartum and postpartum DMI, milk yield and composition, and plasma minerals were not affected by treatment. No clinical cases of milk fever were observed for either treatment group. Reducing prepartum DCAD from +388 to +183 meq/kg DM did not improve prepartum blood profiles or postpartum milk yield or composition; therefore, this type of supplementation was not economical.     

The effects of calcium supplementation of dairy cattle after calving on milk, milk fat and protein production, and fertility

AIM: To determine the effect of calcium supplementation of dairy cattle after calving on serum concentrations of calcium, magnesium, and phosphorous after calving, and on reproductive and productive performance in the following lactation. METHODS: This was a double-blind randomised clinical trial using 356 dairy cows of parity 3 or greater from six seasonally calving commercial dairy herds. Cows were randomly assigned to a treatment and control group. The treatment group received two doses of 380 ml of calcium chloride in oil (49 g of elemental calcium); the first dose was given as soon as practical after calving and the second 12 hours later. Control cows received 380 ml of a placebo using the same treatment regime. Treatment and control cows had blood samples taken during the first 7 days after calving to determine serum calcium, magnesium and phosphorous levels. Treatment and control cows were monitored throughout the lactation to measure production and reproductive performance. RESULTS: Treatment had no effect on PSM to first service intervals. Treatment significantly reduced PSM to conception intervals in only one of the four herds with data available for analysis (p = 0.09). There was no difference between treatment groups for adjusted corrected milk yield calculated from the first herd test milk yield (p = 0.93) or 305-day milk solids production (p = 0.19). CONCLUSION: Further studies are required to identify reasons for the between-herd effectiveness of calcium chloride treatment in improving fertility.     

Effect of somatotropin on adipose tissue metabolism: Ontogeny of the enhanced response to adrenergic challenge in the lactating cow

Seven multiparous Holstein cows (>150 d postpartum) were used to evaluate the time course of the chronic adaptation in lipolytic response to adrenergic challenge with bovine somatotropin (bST) treatment. Cows received daily bST (sometribove; 40 mg/d) or excipient injections for 7 d (single reversal design) with a 7-d interim between periods. Epinephrine challenges (1.4 μg/kg body weight intravenously) were administered on Days −2, −1, 1, 2, 3, 5, and 7 of treatment at 10:00 a.m. (15 hr after bST or excipient injection). Frequent blood samples were collected, and concentrations of plasma glycerol (GLY) and nonesterified fatty acids (NEFA) were determined. Treatment with bST increased milk yield 23% (P < 0.05) and milk fat content 33% (P < 0.001) compared with controls. Somatotropin-treated cows entered negative energy balance by Day 3 and had higher basal plasma concentrations of GLY and NEFA than did controls by Day 2 and Day 3, respectively. Response to epinephrine, expressed as area under the response curve corrected for basal, was enhanced by bST treatment, regardless of energy balance. GLY response was greater than control by Day 1 of bST treatment (P < 0.01), and had plateaued by Day 2 (P < 0.001). The NEFA response area was higher than control and had plateaued by Day 1 of bST treatment (P < 0.001). Day 1 represented 15 hr after the first bST injection. Results illustrate that bST treatment results in enhanced in vivo lipolytic response to catecholamine challenge, and the metabolic adaptation is in place by 15 hr after the first bST injection.     

Effect of several doses of zeolite A on feed intake,energy metabolism and on mineral metabolism in dairy cows around calving

The object of the present study was to determine the influence of different zeolite A doses on dry matter intake (DMI) and mineral metabolism, and to evaluate an optimum dosage for preventing hypocalcaemia. Eighty pregnant dry cows were assigned to four groups (I–IV). They were fed a total mixed ration (TMR) ad libitum. Groups II, III and IV received an average daily dose of 12, 23 and 43 g zeolite A/kg DM for the last 2 weeks prepartum. Individually DMI was recorded daily. Blood and urine samples were taken before, during and after zeolite A supplementation. Serum was analysed for Ca, Mg, P_i, K, non‐esterified fatty acids and β‐hydroxybutyrate (BHB). Urine was analysed for Ca, Mg, P_i, K and net acid‐base excretion (NABE). After calving, milk yield (fat corrected milk) and milk composition were determined. During zeolite A supplementation, mean DMI of Group IV (7.3 ± 1.3 kg/cow/day) was significantly lower compared to Groups I–III (10.1, 10.9, 9.5 kg/cow/day). The reduced feed intake of Group IV resulted in significantly increased BHB as well as decreased NABE after calving. Zeolite A supplementation in higher doses (III and IV) had a stabilizing effect on Ca metabolism around calving for older cows, whereas cows in Groups I and II showed a subclinical hypocalcaemia. The mean serum Mg concentration decreased significantly in older cows in Group IV at calving. The mean P_i concentration in cows of Group IV decreased into ranges of hypophosphataemia already 1 week after beginning of zeolite A feeding. The mean DMI postpartum as well as the milk yield was not affected by zeolite A supplementation. Feeding of 23 g zeolite A/kg DM TMR prepartum proved to be an adequate dosage for reducing subclinical hypocalcaemia frequency without significant effects on feed intake and P_i concentration in serum.     

日粮离子平衡对围产期奶牛健康的影响

选择30头产前21天的奶牛，随机均分成对照组和试验组，对照组正常饲喂，试验组添加离子平衡调节剂。结果表明，试验组降低日粮离子平衡(DCAD)后奶牛尿液pH值显著降低(p＜0．01)，血液pH值稍有降低，但差异不显著(p＞0．3)。产前血清钙和产后血清磷的浓度显著提高(p＜0．05)，产后血清钙和产前血清磷的浓度也有较为明显的提高(p=0．224和p＝0．154)。试验组奶牛尿中酮体的检出率、产褥热和胎衣滞留的发生率都明显低于对照组。     

Effects of body condition at far-off dry period on blood biochemistry,liver triacylglycerol and muscular monocarboxylate transporter-1 mRNA expression in tropical Holstein dairy cows during peripartum period

Effects of body condition score (BCS) at far-off dry period on blood biochemistry, liver triacylglycerol, and muscular monocarboxylate transporter-1 mRNA expression in tropical Holstein dairy cows during peripartum period were studied. Eight dry cows were divided into two groups of four cows based on their BCS at 8 weeks prepartum: high BCS (HBS) and low BCS (LBS). Blood samples were collected weekly from 8 weeks before expected calving date until 8 weeks postpartum for determination of serum glucose, non-esterified fatty acid (NEFA), and β-hydroxybutyrate (BHBA). Muscle and liver samples were biopsied at 2 weeks before expected calving date and at 2 weeks postpartum for determination of muscular monocarboxylate transporter-1 (MCT-1) mRNA expression and liver triacylglycerol concentrations. Decreased BCS and elevated serum NEFA and BHBA indicated that LBS cows entered to the NEB period earlier than did HBS cows. LBS cows showed lower liver TAG and higher muscular MCT-1 mRNA expression than did HBS cows. The MCT-1 mRNA expression at 2 weeks prepartum was negatively correlated with BCSs at 2–3 weeks prepartum and at 1–2 weeks postpartum. In conclusion, LBS cows most likely adapted to NEB by upregulation of muscular MCT-1 expression and had lower NEB consequences during postpartum period.     

Predictive value of prepartum serum metabolites for incidence of clinical and subclinical mastitis in grazing primiparous Holstein cows

The aim of this study was to measure changes in biochemical markers in the peripartum period of primiparous Holstein cows diagnosed with subclinical and clinical mastitis. In this study, 37 dairy cows were monitored daily during milking until 60 days postpartum and were categorized according to the occurrence of clinical mastitis (group mastitis (GM), n?=?9) or subclinical mastitis (group subclinical mastitis (GSUB), n?=?10) or absence of symptoms (control group (CG), n?=?18). Blood samples were collected weekly from ?30 to 60 days from calving. Samples were grouped for prepartum (?30 to 0 days from calving), early postpartum (0 to 30 days from calving), and late postpartum (30 to 60 days from calving) periods. Prepartum serum non-esterified fatty acid (NEFA) concentration was higher in GM than in CG (P?<?0.01). In addition, CG had higher prepartum serum glucose concentration than GM (P?=?0.03). In the early postpartum period, aspartate aminotransferase (AST) activity was lower in CG than in GSUB (P?<?0.05), and in the late postpartum period, AST activity was lower in CG than GSUB and GM (P?=?0.01). Somatic cell count was higher during the early and late postpartum periods for GM and GSUB when compared to CG (P?<?0.01). In this study, primiparous cows with low glucose and higher NEFA in the prepartum were more susceptible for mastitis in the early postpartum, probably due to low immune function associated to a more negative energy balance. In sum, increased prepartum serum NEFA concentration and decreased glucose in primiparous cows were associated with clinical mastitis incidence in the postpartum period.     

Effectiveness of calcium chloride in increasing blood calcium concentrations of periparturient dairy cows.

Calcium chloride supplements such as gels and drench were studied to determine their effectiveness for increasing blood serum Ca concentrations in periparturient dairy cows. Multiparous, pregnant Holstein dairy cows (n = 36) were assigned to one of four treatments. After calving, cows in four treatments received basal diet and two doses of either control inert gel (CON), gel containing CaCl2 and vitamins (CVG), gel containing CaCl2 and minerals (CMG), or CaCl2 as drench containing vitamins (CVD). The first dose was given within 2 h after calving and the second dose 12 h after the first dose. Each dose provided .07, 54.5, 56.0, and 33.2 g of elemental Ca in CON, CVG, CMG, and CVD treatments, respectively. Blood samples were collected at 0, 15, 30, 60, 180, and 360 min after each oral dose. The blood serum Ca concentrations were 6.26, 7.56, 6.20, and 5.96 mg/dL during the pretreatment period and deviated -13.5, 7.1, 9.3, and 18.1% from pretreatment levels at 18 h after the first dose in CON, CVG, CMG, and CVD treatments, respectively. The average changes in serum P from pretreatment levels were not different among treatments. Serum Mg concentrations remained below the pretreatment levels in all four treatments. Blood serum beta-hydroxybutyrate during the first 2 wk and milk yields during the first 4 wk of lactation were the same in all treatments. Three cases of clinical milk fever were observed in CON treatment and one case in CVD treatment. The oral supplements of CaCl2 as gel or drench increased the blood Ca levels in periparturient dairy cows. Increased supply of Ca through oral supplements of CaCl2 may prevent milk fever in cows that are marginally hypocalcemic.