Effects of low and high calcium intake prepartum on calcium mobilization rate around parturition in dairy cows

Forty-one dairy cows were fed a low (LCa-13 g/d) and a high (HCa-83.5 g/d) calcium ration in the 8 weeks prior to parturition and the effect on the Ca mobilization rate around parturition was studied. Plasma Ca values were stable in the LCa group around parturition. In the older cows of the HCa group a very slight decrease in the mean plasma Ca was observed: 2.58 mmol/l at 12-36 h ante partum decreased to 2.38 mmol/l at parturition. Hypocalcaemia, which commonly occurs around parturition, did not occur in 40 of the cows. A subclinical hypocalcaemia (1.8 mmol/l) occurred in one cow (parity 10) from the HCa group. To assess the efficiency of Ca mobilization, a severe hypocalcaemia (1.0 mmol/l) with clinical signs was induced by means of Na2EDTA infusion (0.90 mmol/min), starting at 10 h post-partum. The older cows in the LCa group required more Na2EDTA than those in the HCa group. Higher urinary hydroxyproline excretion in the week before parturition in the LCa than in the HCa group suggested a higher bone turnover. Plasma PTH levels around parturition were not significantly different between the groups. The amount of colostrum milked out in the first 10 h post-partum did not influence Ca homeostasis around parturition. The results contradict those of many other experiments in which hypocalcaemia was observed in cows ingesting high levels of Ca. It is concluded that the restricted feed intake prepartum possibly had a favourable effect on Ca homeostasis.     

Effects of calcium and magnesium intakes and feeding level during the dry period on bone resorption in dairy cows at parturition

A study was made of the influence of low and high calcium intakes at two feeding levels (experiments 1 and 2), and of different magnesium intakes (experiment 3) during the dry period, on the cellular resorptive activity in bone of dairy cows at parturition. In experiment 1 (26 cows) the feed intake was 1.12 times maintenance and the calcium intake was either 13.0 g d-1 or 83.5 g d-1. In experiment 2 (33 cows) the feed intake was 1.9 times maintenance and the calcium intake was either 26.4 g d-1 or 87.2 g d-1. In experiment 3 the cows feed intake was 1.4 times maintenance, the calcium intake was 71 to 72 g d-1 and the magnesium intake was either 16.6 g d-1 or 71.0 g d-1. Bone biopsies were taken from the tuber coxae between three and eight hours after parturition. In experiment 1 the cellular resorptive activity in bone from older cows was higher in the cows receiving the low calcium diet. In experiment 2 the differences between the bone resorptive activities of the two groups were small. In experiment 3 the bone resorptive activity was lower in the cows with a deficient supply of magnesium. There were significant relationships in young cows, but not in older cows, between the cellular resorptive activity in bone and the rate of calcium mobilisation measured biochemically. These results suggest that in older dairy cows bone resorption makes only a minor contribution to the total rate of calcium mobilisation at parturition and is therefore of minor importance for the prevention of periparturient hypocalcaemia.     

Influence of a deficient supply of magnesium during the dry period on the rate of calcium mobilisation by dairy cows at parturition

The influence of a deficient magnesium supply during the dry period on the ability of dairy cows to mobilise calcium at parturition was investigated. The daily rations pre-partum consisted of 6 kg grass hay, and 4 kg concentrates containing either 1.58 per cent magnesium (HMg) or 0.22 per cent magnesium (LMg). Nine cows of parity one to six received the LMg diet and 10 cows of parity one to seven the HMg diet. Both rations provided 1.40 times maintenance on an energy basis and contained 4 per cent potassium in the dry matter. Throughout the dry period the mean concentration of magnesium in the plasma of the LMg group was significantly lower than in the HMg group and at parturition the mean plasma concentrations were 0.65 mmol litre-1 and 1.16 mmol litre-1, respectively. After parturition two cows in the LMg group showed clinical signs of hypocalcaemia but none of the HMg group did so. Cows of the LMg group had a lower mean rate of calcium mobilisation (0.27 mmol min-1) than those of the HMg group (0.34 mmol min-1) but the difference could not be explained by differences in bone turnover as reflected by urinary hydroxyproline excretion. Such a reduced rate of calcium mobilisation may be a contributory factor in the high incidence of milk fever in some herds fed inadequate magnesium in the dry period.     

Bone mineral changes in dairy cows. The effect of low and high calcium feeding during late pregnancy and at parturition

The bone mineral content in two coccygeal vertebrae of 16 cows of Swedish Red and White Breed was measured with dichromatic photon absorptiometry during the period nine weeks prepartum to one week postpartum. For eight weeks before calving eight cows received 37 g Ca and 50 g P/day and the other eight, 76 g Ca and 50 g P/day. The mean bone mineral changes of the cows on the low Ca ration did not change. The cows on the high Ca ration had a slight increase (4 %) in bone mineral content to some days before calving. The postpartum bone mineral changes were, however, lower than the one prepartum. There was no significant difference between the mean bone mineral changes of the two groups.     

Alterations in neutrophil phagocytosis and lymphocyte blastogenesis in dairy cows around parturition

The bovine blood neutrophil phagocytosis and the blood and milk lymphocyte proliferative response upon stimulation with Phytohaemagglutinin, Concanavalin A and Pokeweed mitogens was studied from 3 weeks prior to calving until 3 weeks after calving. Neutrophil phagocytosis and the total and differential blood leukocyte counts were performed by flow cytometry. A gradual increase in the percentage of phagocytized bacteria and the average number of bacteria per phagocyte was observed before calving followed by a sharp fall on the first postpartum. This was followed by a steady increase in the above parameters reaching the highest levels at two weeks postpartum. There was a gradual increase in the number of neutrophils in blood as calving approached followed by a sharp decrease after calving. The number of lymphocytes in blood dropped before calving, being at the lowest level on the day before calving. The proliferative response of blood and milk lymphocytes upon stimulation with the three mitogens was low during the week preceding parturition with the lowest value on the day before calving. The response of blood lymphocytes returned to a higher level the second week after calving while that of milk lymphocytes remained at a low level during the first and the second postpartum weeks.     

Plasma mineral and energy metabolite concentrations in dairy cows fed an anionic prepartum diet that did or did not have retained fetal membranes after parturition

OBJECTIVE: To compare plasma total calcium, phosphorus, magnesium, nonesterified fatty acids (NEFA), beta hydroxy butyrate (BHB), and glucose concentrations in parturient dairy cows that were fed an anionic prepartum diet between those with and without retained fetal membranes (RFM) at 24 hours after parturition. ANIMALS: 152 Holstein cows that calved during October through December of 1997 PROCEDURE: All cows were fed an anionic prepartum diet. Blood sample was taken within 6 hours after parturition from randomly selected cows. Thirty-nine cows had a diagnosis of RFM at 24 hours after parturition; 113 were not affected with RFM. At calving, body condition score (BCS; 1 [thin] to 5 [obese]), parity, and calving difficulty score were recorded. Plasma calcium, phosphorus, magnesium, NEFA, BHB, and glucose concentrations were compared between cows with or without RFM. RESULTS: Cows with RFM had significantly lower plasma calcium concentration soon after calving, compared with cows without RFM. Cows with a parity of > or = 3 had significantly lower plasma concentrations of calcium and higher concentrations of magnesium, compared with cows with a parity of 1 or 2. Cows with a BCS of > or = 3.25 at calving had significantly higher plasma concentrations of BHB than cows with a BCS of 2.75 to 3.0. Cows with dystocia had significantly higher plasma concentrations of glucose, compared with cows without dystocia. CONCLUSIONS AND CLINICAL RELEVANCE: In parturient cows fed a prepartum anionic diet, those with RFM have lower plasma calcium concentrations than cows without RFM, although this association does not prove a cause-effect relationship.     

酵母铬对围产前期奶牛抗氧化能力的影响

研究在日粮中添加不同水平的酵母铬对围产前期奶牛抗氧化性能的影响。选用20头体况和预产期相近的中国荷斯坦奶牛,随机分为4组,对照组为基础日粮,3个处理组在基础日粮中分别添加2.4、4.8和7.2g/d的酵母铬。结果显示,与对照组相比,添加酵母铬可以提高血清中总抗氧化能力（T-AOC）,超氧化物歧化酶（SOD）和谷胱苷肽过氧化物酶（GSH-Px）的活力（P〈0.01）;在4.8g/d铬水平下,与对照组相比饲喂酵母铬奶牛血清丙二醛（MDA）含量显著降低（P〈0.01）。结果表明,基础日粮添加酵母铬,0.4mg Cr/kg干物质（DM）可提高围产前期奶牛抗氧化能力。     

Effects of calcium intake and parity on plasma minerals and bone turnover around parturition

Eight pregnant heifers (primiparous cows) and seven pregnant cows in their second, third and forth pregnancies (multiparous cows) were assigned to two groups and fed either a low calcium (Ca) diet (Ca, 0.46%) or a high Ca diet (Ca, 0.86%) ad libitum from 3 weeks before the expected calving date to 3 days after parturition. All cows were examined for a change in dry matter intake (DMI), plasma minerals and bone turnover around parturition. The dietary Ca level did not affect the DMI in both primiparous and multiparous cows. The DMI of primiparous cows was significantly lower than that of multiparous cows (P < 0.05) in both the low and high dietary Ca groups. The dietary Ca level did not affect the concentrations of plasma Ca, phosphorus, magnesium and parathyroid hormone throughout the experimental period. Plasma phosphorus in primiparous cows was significantly higher (P < 0.05) than that of multiparous cows around parturition. Plasma Ca and magnesium tended to be higher (P < 0.10) in primiparous cows. The dietary Ca level did not affect the plasma osteocalcin (OC) level measured as bone formation or the urinary deoxypyridinoline (DPD) excretion measured as bone resorption before parturition in both primiparous and multiparous cows. After parturition, the plasma OC level was lower than it was before parturition in multiparous cows fed a low Ca diet, and in primiparous cows. There were no significant differences in urinary DPD excretion between each group before and after parturition. Both the plasma OC level and urinary DPD excretion of primiparous cows were significantly higher than those of multiparous cows in both the low and high dietary Ca groups.     

酵母铬对围产前期奶牛免疫功能的影响

选用20头体况和预产期相近的中国荷斯坦奶牛,随机分为4组,对照组喂基础日粮,3个处理组在基础日粮中分别添加2.4、4.8、7.2g/d的酵母铬。结果显示,与对照组相比,添加酵母铬可以提高外周血淋巴细胞转化能力,提高了IgM、IgG和IgA的含量(P0.01)。结果表明,基础日粮添加2.4g/d的酵母铬,使DM铬添加水平为0.4mg/kg时,效果较好。     

Impacts of dietary fat level and saturation when feeding distillers grains to high producing dairy cows

This experiment was conducted to determine whether increasing the net energy (NE_L) of a total mixed ration (TMR) with mainly unsaturated fat from corn distillers dried grains with solubles (DDGS) vs. rumen inert (RI)‐saturated fat has similar impacts on animal performance. The experiment was an incomplete Youden square with three treatments and four 28‐days periods, completed on a large commercial dairy using three early lactation pens each with approximately 380 multiparity cows. The TMR for all treatments was the same, except for 150 g/kg dry matter (DM) of each TMR which contained 90 g/kg high‐protein DDGS (HPDDGS) and 60 g/kg beet pulp (i.e. low‐fat control diet; LFC); 150 g/kg DDGS (i.e. high‐fat diet with unsaturated fat; HFU); or 111 g/kg HPDDGS, 20 g/kg beet pulp and 19 g/kg RI fat (i.e. high‐fat diet with saturated fat; HFS). The DM intake was highest (p < 0.05) for HFU‐fed cows. Milk, fat and true protein yields, as well as milk energy output, were higher (p < 0.01) when cows were fed HFS vs. HFU and LFC diets. Milk true protein concentration was lowest (p < 0.01) for HFS‐fed cows, but milk fat % was lowest (p < 0.01) for HFU and highest (p < 0.01) for HFS‐fed cows. There were numerous differences (p < 0.01) in milk fatty acid levels amongst diets. The increase in body condition score was lowest (p < 0.01) for LFC. Whole tract digestibility of acid detergent fibre was lower (p < 0.01) for LFC vs. HFS cows, and fat digestion was lowest (p < 0.01) for LFC‐fed cows. This DDGS, high in unsaturated fatty acids, was fed at high levels (i.e. 152 g/kg DM) with little impact on animal performance vs. a lower fat control diet, although addition of an RI‐saturated fat to create a diet with a similarly higher fat level resulted in higher animal productivity.     

Production responses of lactating dairy cows and heifers given thiabendazole at parturition

A field trial was conducted to examine the effects on productivity of dairy cattle in 6 herds given thiabendazole at parturition. Criteria examined were milk and fat production, calving interval, services per conception, culling rate, and (in a subset of cows) hematologic response. Analysis of the data for all cows as a group did not indicate a significant effect. For first-calf heifers in 1 herd, a significant (P less than 0.01) and economically important increase in milk production was observed; why the effect was seen was not determined.     

阴离子盐对奶牛围产期血浆离子平衡的影响

采用20头荷斯坦经产奶牛按配对试验设计,研究在干奶后期(产前约3周)添加阴离子盐添加剂对奶牛产前1周、2周和产后1周、2周及分娩当日血浆离子浓度、胎衣不下发病率以及产乳热发病情况的影响。结果表明,饲喂阴离子盐日粮4d后可使尿液pH值显著降低(P<0.05),试验组与对照组比较产前一周和产后一周血浆钙离子浓度有上升的趋势,分别为(7.98vs7.26)和(7.81vs7.19),距分娩1周血浆镁离子浓度有降低趋势(1.96vs2.16),在分娩当日试验组血浆镁离了浓度低于对照组(1.90vs2.01),产前1周和分娩当日血浆钠离子浓度低于对照组,分别为(123.90vs126.43,P<0.05)和(124.28vs125.93,P<0.05)。在本试验条件下添加阴离子盐对血浆其他离子浓度没有显著影响(P>0.05),通过对胎衣不下发生情况的统计表明,饲喂阴离子盐能够减少胎衣不下的发生。     

Induction of parturition in dairy cows with dexamethasone.

Sixty Holstein cows were paired by parity and sire, and one of each pair was allocated at random to treatment or control; 17 cows were injected with 7.5 mg/100 kg dexamethasone trioxa undecanoate 14 days before the predicted date of calving, 13 cows received the same dose five days before term and 30 cows were left untreated. The treatment significantly advanced parturition and 29 of the 30 induced cows calved within 72 hours of the injection. Induction at day 14 before term was safe for calf and dam, the calves were 3.2 kg lighter than control calves and there was a high incidence of retained placenta. Treatment for this condition resulted in increased veterinary costs of 14.50 pounds per cow exclusive of dexamethasone treatment. Treatment at this stage was also associated with low pregnancy rates in the next breeding season. Calves born after induction at five days before term were not significantly lighter than calves from control cows, the problem of retained placenta was less marked and there were no subsequent effects on fertility. There were no significant effects of induction on milk yield or milk quality up to 200 days of lactation.     

TMR日粮不同颗粒大小对奶牛采食行为的影响

试验选择6头体况良好,产奶天数(DIM)接近的荷斯坦奶牛,采用3×3重复拉丁方设计,通过给奶牛饲喂由不同颗粒片段大小(长切割L,短切割S,中等水平M)的玉米青贮组成的TMR日粮来研究其对奶牛采食、反刍行为等的影响。结果表明:降低日粮颗粒片段大小,奶牛的干物质采食量(DMI)、中性洗涤纤维采食量(NDFI)及酸性洗涤纤维采食量(ADFI)均下降,但各处理组间差异不显著(P>0.05);物理有效中性洗涤纤维采食量(peNDFI)也下降,L组与S组间差异显著(P<0.05);降低日粮颗粒大小,奶牛的采食时间、反刍时间及总咀嚼时间下降,L组与S组间奶牛的采食和反刍时间差异显著(P<0.05);奶牛的总咀嚼时间L组与M组、M组与S组间差异显著(P<0.05),而L组和S组间差异极显著(P<0.01)。试验表明,改变日粮颗粒大小对奶牛的DMI等影响不显著,对奶牛的咀嚼活动则有显著的影响。     

Cholecystokinin mediates depression of feed intake in dairy cattle fed high fat diets

Two experiments were conducted to investigate the effects of 1) different concentrations of dietary fat and 2) i.v. administration of a cholecystokinin receptor antagonist (MK-329) on feed intake and plasma concentrations of hormones and metabolites in dairy cattle. In Experiment 1, 4 lactating Holstein cows were used in a 4 x 4 Latin square design. Treatments were diets with 1) no fat added, 2) 30 g fat/kg feed (calcium salts of long-chain fatty acids as fat supplement), 3) 60 g fat/kg, and 4) 90 g fat/kg added. Cows were fed once daily a diet of concentrate, corn silage, alfalfa haylage, and alfalfa pellets. Dry matter intake decreased linearly with increasing concentrations of dietary fat (P < 0.0001). Overall plasma concentrations of nonesterified fatty acids (P < 0.0001), triacylglycerol (P < 0.0006), and cholecystokinin (P < 0.02), increased linearly with each level of dietary fat, but there was a linear decrease in plasma insulin (P < 0.0008). In Experiment 2, 4 nonpregnant and nonlactating Holstein heifers were used in a cross-over design in a 2 x 2 factorial arrangement of treatments. Treatments were diet (fatty acids, 27 g/kg vs 103 g/kg diet dry matter) and i.v. injections (MK-329 vs vehicle). Heifers were fed once daily a total mixed ration of corn silage, cracked corn and soybean meal with or without fat supplement. Diets were switched by period and either MK-329 (70 microg/kg body weight) or its vehicle was injected i.v. at 2 hr postfeeding. Daily dry matter intake was decreased by feeding the high fat diet (P < 0.02) but was not affected by injections. Injection of MK-329, however, increased dry matter intake by 92% in heifers fed the high fat diet during the first 2 hr postinjection compared to vehicle injection. Plasma pancreatic polypeptide concentration was increased by the high fat diet at 2 hr postfeeding (P < 0.02) but was lowered by MK-329 at 1 hr postinjection (P < 0.001). Plasma insulin was lowered by the high fat diet (P < 0.01) but was not affected by injections. The elevated plasma cholecystokinin concentration may have mediated depressed feed intake of dairy cattle fed the high fat diets.     

Effect of prepartum compensatory nutrition regimen on metabolism and performance of dairy cows

The impact of closely controlled energy management during the dry period upon general peripartum metabolism and the subsequent lactation was evaluated in multiparous dairy cows. Eight lactating, pregnant Holstein cows were paired according to current milk production and body condition score and assigned to either the control or the stair-step compensatory nutrition (SSCN) regimen 16 weeks prior to expected calving date. Control cows were fed according to National Research Council [National Research Council., 2001. Nutrient Requirements of Dairy Cattle. 7th rev. ed. Natl. Acad. Sci., Washington, DC.] recommendations and for ad libitum intake during late lactation and the far-off dry period. The SSCN cows were subjected to dietary energy restriction [80% of net energy for lactation requirements (NE_L)] during late lactation in order to maintain body weight, followed by realimentation (130% of NE_L) during the far-off dry period to induce a compensatory response. A common diet was fed thereafter. The SSCN cows gained less body condition during late lactation and tended to gain more body condition during the far-off dry and transition periods than control cows. There was no difference in dry matter intake during the prepartum transition period and early lactation. Milk yield was not affected by treatment. Serum nonesterified fatty acids (NEFA) were not altered by dietary treatment during late lactation and the dry period; however NEFA were lower in SSCN cows at week 4 of the subsequent lactation. Serum insulin was higher in SSCN cows 8 weeks prior to parturition (end of restriction), tended to be higher at 4 weeks (end of realimentation) before calving, and was also higher at week 12 of early lactation. An SSCN regimen stimulated body condition gain of mature dairy cows during the dry period, did not affect periparturient nutrient metabolism, and led to modest improvements in metabolic parameters later in the subsequent lactation.     

Responses of energy balance, physiology, and production for transition dairy cows fed with a low-energy prepartum diet during hot season

Twenty multiparous Chinese Holstein dairy cows calving in hot summer (S group), were compared with 20 similar control cows calving in cool autumn (C group). Diets were the same for both groups; prepartum diets had relatively low energy density. Average temperature–humidity index was 76.5 and 53.0 in summer and autumn, respectively. S group cows had significantly higher rectal temperatures (39.6 vs. 39.0 °C) and respiration rates (79.0 vs. 31.3 breaths/min) than C group, and consumed less feed (prepartum 8.0 vs. 12.3 kg/day, postpartum 16.3 vs. 21.2 kg/day). Calculated energy balance (EB) was ?7.98 vs. ?5.15 Mcal/day for S group prepartum and postpartum, respectively. In contrast, EB was 1.36 vs. ?2.03 Mcal/day for C group prepartum and postpartum, respectively. S group produced significantly less milk than C group by 15.4 % (5.2 kg/day) and 26.8 % (10.2 kg/d) for milk yield and energy-corrected milk, respectively. Percentages of milk fat (3.28 vs. 4.29 %), protein (3.08 vs. 3.33 %), and solids-not-fat (8.46 vs. 8.78 %) were significantly lower for S group. Milk urea nitrogen (19.54 vs. 13.31 mg/dL) was significantly higher in S group. Significantly lower feed efficiency was observed in S group (1.56 vs. 1.66). During the entire transition period, S group had significantly lower circulating glucose levels. S group had significantly higher levels of nonesterified fatty acids (NEFA) prepartum, but after 14 days in milk, NEFA was significantly lower. We conclude that increasing dietary energy density during transition period (especially prepartum) is necessary to minimize adverse effects of hot season.