Effects of growth hormone administration on vitamin D metabolism and vitamin D receptors in the pig

Twelve 36-kg pigs were given either 100 micrograms/kg porcine pituitary growth hormone (pGH) or placebo injections daily for 33 days. Serum was obtained weekly for analysis of minerals and vitamin D metabolites. On day 34, the pigs were sacrificed and renal and duodenal tissue were obtained for analysis of vitamin D receptor content (VDR). Animals treated with pGH grew faster and had a higher rate of bone accretion than did control animals. Serum concentrations of 1,25-dihydroxyvitamin D (1,25-(OH)2D) were significantly higher in pGH-treated pigs than in control pigs at all time points following initiation of treatment, with the greatest difference observed at day 28 (42.4 +/- 4.9 pg/ml in controls vs. 65.4 +/- 4.7 pg/ml in pGH-treated pigs). Serum 24,25-dihydroxy-vitamin D tended to be lower in pGH-treated pigs than in control pigs, being significantly lower on day 21 of the experiment (3.22 +/- .52 vs. 6.73 +/- 1.22 ng/ml, respectively). Serum concentrations of 25-hydroxyvitamin D and calcium were unaffected by pGH treatment. Kidneys of control pigs contained significantly more unoccupied vitamin D receptors than did kidneys from pGH-treated pigs (73.3 +/- 4.3 vs. 58.3 +/- 4.1 fmoles/mg protein). Duodenal tissue unoccupied vitamin D receptor content was similar in both pGH-treated (245 +/- 17.9 fmoles/mg protein) and control (263 +/- 21.8 fmoles/mg protein) pigs. Duodenal occupied vitamin D receptor concentration was similar in both pGH-treated (6.8 +/- .75 fmoles/mg protein) and control pigs (5.32 +/- .77 fmoles/mg protein).(ABSTRACT TRUNCATED AT 250 WORDS)     

钙与维生素D_3对肉品质的影响

本文首次系统阐述了钙与维生素D3对肉的嫩度及其他食用品质与感官品质的影响 ,并对二者改善肉品质的机理作了深入分析 ,最后指出了今后的研究方向     

The effect of intramuscularly administered vitamin D3 on serum vitamin D metabolites and electrolytes in vitamin D3 deficient dairy cows

The effect of intramuscular administration of vitamin D₃ (1×10⁶ IU D₃/100 kg bodyweight) to 3 different dairy breeds on the serum levels of vitamin D₃, 25-OH-D₂, 25-OH-D₃, Ca, inorganic P and Mg was studied.The vitamin metabolites and the electrolytes were analysed on 9 occasions during a 36-day period. Vitamin D₃ was analysed on 6 occasions during the same period. No significant breed differences were observed except for 25-OH-D₃ (P ≤ 0.05). The D₃ level rose in 1 day from < 2 ng/ml to 906 ng/ml and decreased to below 50 % of the peak level after 6 days. At the end of the experiment (day 36) vitamin D₃ was < 2 ng/ml. 25-OH-D₃ rose from < 2 ng/ml to 106 ng/ml in 6 days and stayed at this level during the whole experiment. 25-OH-D₂ decreased from 16 ng/ml to 5 ng/ml during the observation period.     

Influence of different calcium contents in diets supplemented with anionic salts on bone metabolism in periparturient dairy cows

At the initiation of lactation, Ca homeostatic mechanisms have to react to a tremendous increase in demand for Ca. Mobilization of Ca from bone and increased absorption from the gastrointestinal tract are required to re-establish homeostasis. It has been shown that dietary anions play an important role in the prevention of milk fever by mobilizing Ca from bone and by increasing Ca absorption in the GI tract. The purpose of the present study was to investigate the influence of different Ca contents in diets supplemented with anionic salts on bone metabolism of dairy cows. Twenty-four holstein cows (housed inside, second to fourth lactation) without a milk fever history were divided into four groups (A, B, C, D). Each group was fed a different diet which was given from day 263 of gestation till the day of parturition. Group A and B received a low calcium diet (4 g/kg DM) whereas group C and D received a high Ca diet (8 g/kg DM). In addition group B and D received anionic salts. The DCAD was calculated with the formula: DCAD (mEq/kg DM)=(0.2 Ca2++0.16 Mg2++Na++K+)-(Cl-+0.6 S2-+0.65 P3-). Blood and urine samples were collected on days 256, 270 and 277 of gestation, on the day of parturition as well as the following 5 days and on days 9, 14 and 19 after parturition. Serum Ca, P, Mg, ICTP, OC, VITD, PTH and urinary pH were analysed. The bone resorption marker ICTP showed a significant increase after parturition in all the groups. On the contrary, the bone formation marker OC decreased after parturition in all the groups. The VITD concentrations in group D and the urinary pH in group B were significantly lower compared to the other groups (p<0.05). The Ca concentrations tended to be higher in group B around parturition than in all the other groups. No significant influence of the four different diets on all the other parameters could be shown. In conclusion, this data showed that the addition of anions and the different Ca contents had no significant influence on bone resorption and bone formation markers. This may be because of the fact that the dietary cation-anion balance was not low enough (DCAD-group A: 181 mEq/kg DM, group B: -48 mEq/kg DM, group C: 210 mEq/kg DM and group D: 28 mEq/kg DM) to induce a metabolic acidosis with all its positive effects on calcium metabolism.     

Supranutritional oral supplementation with vitamin D3 and calcium and the effects on beef tenderness

Ultimate meat tenderness can be influenced by numerous preslaughter and postmortem management techniques. Increased levels of intracellular Ca2+, through postmortem injection, infusion, or marination, have been shown to improve the tenderness of cooked meat products. Oral supplementation with vitamin D3 effectively increases serum Ca2+ and has been hypothesized to increase muscle Ca2+ content, the activity of muscle proteases, and thus the tenderness of cooked beef. Individual Charolais x Hereford heifers (n = 191) were assigned to an unsupplemented control group or groups that were supplemented via oral bolus (for dose regulation purposes) with one of seven levels of vitamin D3 (1, 2, 3, 4, or 5 x 10(6) IU D3/d, 2 x 10(6) IU DS/d plus 75 g CaCO3 or 4 x 106 IU D3/d plus 75 g CaCO3) for 2, 4, 6, or 8 d antemortem. Individual feedlot performance, serum Ca2+ levels, and carcass data were collected, and eight longissimus steaks/carcass were used to obtain Warner-Bratzler shear force values measured at 2, 7, 14, and 21 d postmortem for longissimus steaks cooked to 70 degrees or 85 degrees C. Cattle supplemented with 4 x 10(6) IU D3/d plus 75 g of CaCO3 had lower daily feed intake (as-fed) and reduced (P < 0.05) average daily gains compared with controls during the 8-d supplementation period. Additionally, supplemented cattle had numerically higher dressing percentages, possibly due to less fill at the time of slaughter, because carcass weights and USDA yield grades did not differ (P > 0.05) across treatment groups. Supplementation with 1, 2, 3, 4, or 5 x 10(6) IU D3/d, for 2 or more days, increased (P < 0.05) serum Ca2+ concentrations compared with controls. Whereas cattle that received additional dietary Ca2+ in the form of CaCO3 had the lowest blood serum Ca2+ concentration. Although blood serum Ca2+ was increased, supplementation with any level of vitamin D3 for any length of time up to 8 d did not improve (P > 0.05) Warner-Bratzler shear force at 2, 7, 14, or 21 d of postmortem aging compared with controls when steaks were cooked to final internal temperatures of either 70 (control means 6.27, 4.91, 4.64, and 3.80 kg, respectively) or 85 degrees C (control means 7.31, 5.32, 4.69, and 4.46 kg, respectively). Results indicated that oral supplementation with vitamin D3 (at high or low doses) for 2 to 8 d before slaughter increased serum Ca2+ concentration but does not improve cooked longissimus tenderness.     

Plasma parathyroid hormone-related peptide and bone metabolism in periparturient dairy cows

The first weeks of lactation in dairy cows are characterised by elevated bone resorption. The connection between lactation and bone metabolism is still much discussed. In this work, changes in the concentration of plasma parathyroid hormone-related peptide (PTHrP) and markers of bone metabolism were studied in Holstein cows and heifers in the dry period and early lactation to determine the role of PTHrP in the relationship between the rate of bone remodelling and the onset of lactation in dairy cows. Blood samples were taken 14 days before calving ('D-14', n = 23) and then on day 10 ('D+10', n = 21) and day 30 after calving ('D+30', n = 23). Using enzyme immunoassay (EIA), the concentrations of PTHrP, parathyroid hormone (PTH), carboxyterminal cross-linked telopeptide of type I collagen (CTX) and oestradiol and the activity of bone specific alkaline phosphatase (BSALP) were determined. The results showed a statistically significant increase in plasma PTHrP (p < 0.005) and CTX (p < 0.0001) in cows on 'D+10' as compared to 'D-14' and CTX on 'D+30' as compared to 'D-14' (p < 0.0001). Significant negative correlations were found between the concentrations of PTHrP and oestradiol (r = -0.29, p < 0.05) and those of CTX and oestradiol (r = -0.54, p < 0.0001). In nonpregnant heifers (n = 6), the concentration of CTX and the activity of BSALP were significantly higher (p < 0.0001) than in dry cows. The observed increments of PTHrP and bone resorption after parturition reveal adaptations of bone metabolism to lactation in dairy cows.     

Changes of vitamin E status of periparturient dairy cows and newborn calves

Eleven primiparous Holstein Friesian and their crossbred calves (F1, Japanese Black cattle × Holstein Friesian) and 10 multiparous Holstein Friesian and their Holstein Friesian calves were used to evaluate vitamin E status in periparturient period. Plasma α‐tocopherol (α‐toc) concentrations of the multiparous cows were significantly higher than those of the primiparous cows from 60 days before expected calving to 90 days of lactation (P < 0.05). The multiparous cows had a further decrease in the concentrations of α‐toc and total lipid in plasma to the calving than the primiparous cows. Colostrum α‐toc concentrations in multiparous cows were significantly higher than those of the primiparous cows (P < 0.05). Plasma α‐toc concentrations of calves borne by the multiparous cows were significantly higher than those of the primiparous cows at 5 days of age (P < 0.05). Plasma α‐toc concentrations of calves were highest at 5 and 15 days of age in the calves borne by the multiparous and primiparous cows, respectively, and decreased thereafter till 90 days of age. The higher vitamin E status of multiparous cows over primiparous cows might have reflected nutritional composition in the rations. Their calves afforded higher plasma α‐toc levels after birth because of more α‐toc transfer via placenta and more α‐toc secretion in the colostrums thereafter. Plasma α‐toc concentrations of the calves might have decreased as the calves became dependent upon the solid feed of low vitamin E content.     

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.     

补饲维生素D3对育肥猪血钙与肌肉钙含量的影响

本试验旨在研究宰前短期补饲维生素D3对育肥猪血钙和肌肉钙舍量的影响.将20头体重85 kg左右的杜长大三元杂交猪随机分为5组,每组4头.试验设维生素D3的补饲量(2.5×105 Iu/d或5×105IU/d)和补饲时间(5 d或10 d)两个因素.通过对血清钙水平和内中钙含量的测定采评价补饲维生素D3对育肥猪血钙和肌肉钙含量的影响.研究结果表明:补饲维生素D3能提高育肥猪的血清钙含量和肌肉钙的含量(P＜0.05),促进钙的沉积.     

瘤胃保护性蛋氨酸对奶牛的营养作用

瘤胃保护性蛋氨酸(RPMet)经过瘤胃后在小肠转化为蛋氨酸(Met),可增加进入小肠的Met数量,改善小肠氨基酸平衡,提高血清中必需氨基酸浓度、奶牛氮的利用率及其生产性能等.本文综述了RPMet对奶牛的营养作用.     

The effect of dietary calcium and phosphorus supplementation in zeolite a treated dry cows on periparturient calcium and phosphorus homeostasis

Previous studies have proved the possibility of preventing parturient hypocalcaemia by zeolite A supplementation during the dry period, and a recent in vitro study has indicated a marked calcium (Ca) as well as phosphorus (P) binding effect of zeolite A in rumen fluid solutions. Because of the connection between the Ca and P homeostatic systems, the preventive effect against parturient hypocalcaemia may arise from zeolite induced decreased availability of dietary Ca as well as P. In the present study, the expected Ca and P binding capacity was challenged by feeding high and low levels of dietary Ca and/or P to zeolite A treated dry cows. Twenty-one pregnant dry cows were assigned to four experimental groups receiving a dry cow ration unsupplemented or supplemented with extra Ca and/or P. During the last 2 weeks of the dry period all cows additionally received 600 g of zeolite A per day. A high level of dietary P prepartum significantly decreased the plasma Ca concentration before as well as immediately after calving (day 0-3). Conversely, the plasma inorganic phosphate concentration was higher among these cows than among cows receiving no supplemental P. The prepartum dietary Ca level significantly affected the serum 1,25-dihydroxyvitamin D concentration during zeolite supplementation, whereas the periparturient plasma Ca concentration was apparently not affected by the dietary Ca level. During zeolite A supplementation plasma parathyroid hormone was significantly higher among cows receiving additional P. The urinary deoxypyridinoline/creatinine ratio was not affected by the prepartal dietary Ca or P level. Serum aluminium (Al) was significantly higher during zeolite A supplementation than during the preceding period, indicating partial destruction of the zeolite in the intestinal tract with subsequent release and absorption of Al. It is suggested that the effect of prepartum zeolite supplementation on the periparturient Ca homeostasis depends on the level of Ca as well as P in the dry cow ration.     

Plasma parameters related to energy and lipid metabolism in periparturient Modenese and Italian Friesian cows

The aim of this work was to compare energy and lipid metabolism during the peripartum period between Modenese (MO) and Italian Friesian (IF) cows. The study was carried out on 33 pluriparous pregnant cows, 19 IF and 14 MO, reared together in the same herd and kept under equal conditions of management and nutrition. Blood was sampled from jugular vein starting 4 week before expected calving date until 4 week post‐calving, once weekly. Plasma was analysed for glucose, NEFA, BHBA, triglycerides and cholesterol concentrations. Body condition score (BCS) was assessed weekly after blood sampling. Data from antepartum (a.p.) and post‐partum (p.p.) periods were separately analysed as repeated measures by a linear mixed models with the effect of breed, time and their interaction as main factors and random cow within breed. The energy status differed between the two breeds during the peripartum period. We observed higher BCS a.p. and p.p. and lower BCS variations p.p. in MO compared to IF group. Modenese cows showed lower glucose and cholesterol concentrations (p < 0.001), but higher NEFA values, NEFA to cholesterol and NEFA to albumin ratios (p < 0.001) during a.p.; on the contrary, IF cows had higher (p < 0.05) cholesterol, NEFA, BHBA levels and NEFA to albumin ratio than MO ones during p.p. The differences observed between the two breeds suggest how MO cows are subjected to lipid mobilization during late gestation; on the contrary, IF cows are predisposed to mobilize their lipid reserves at the beginning of lactation to support high production. The results indicate a diverse ability to cope with metabolic stress and suggest the hypothesis that the differences in concentrations of plasma parameters and their variation amplitude around the calving period might depend on the different genetic merit for milk production between the two breeds.     

维生素A、D对肉鸡钙磷代谢相关激素水平的影响

试验旨在研究维生素A、D对肉鸡钙磷代谢相关激素水平的影响。采用4×4完全随机试验设计,将8日龄健康艾维茵雄性肉鸡384只称重后随机分为16个处理组。每个处理组设3个重复,每个重复8只鸡,试验期5周。其中,维生素A设4个添加水平,分别为1 500、3 000、15 000和45 000 IU/kg日粮。维生素D设4个添加水平,分别为500、1 250、2 500和5 000 IU/kg日粮。结果表明,45 000 IU/kg维生素A组的肉鸡血清BGP含量相对于1 500 IU/kg维生素A组有显著的降低趋势(P=0.08);随着日粮维生素A水平的增加(1 500～45 000 IU/kg),血清CaBP浓度呈趋于显著的一次线性降低趋势(P=0.092),血清维生素D3与CT含量也呈现降低趋势(P=0.12,P=0.18),其中,以15 000、45 000 IU/kg维生素A组较低,尤以45 000 IU/kg维生素A组最低;血清PTH含量呈显著的一次线性增加(P=0.029)。随着日粮维生素D水平的增加,血清维生素D3含量呈趋于显著的一次线性增加趋势(P=0.093),血清BGP浓度也呈一次线性增加趋势(P=0.14);其中,以2 500和5 000 IU/kg时较高,5 000 IU/kg时最高。由此可知,日粮维生素A过量引起肉鸡骨骼钙磷代谢发生障碍与血清CaBP浓度的降低及PTH浓度的增加有关,也与过量维生素A对维生素D的拮抗作用有关。     

Association between changes in plasma calcium concentration and plasma tartrate-resistant acid phosphatase activity in periparturient cows

Eight periparturient Holstein Friesian cows were examined for plasma tartrate-resistant acid phosphatase (TRAP) activity to assess the degree of bone metabolic activity and to evaluate the association between the change in calcium (Ca) concentration and bone metabolism during the periparturient period. Milk fever occurred in 1 of 8 cows just after parturition. Plasma TRAP activities did not markedly change in 5 of 8 cows during the experimental period. The changing rate of Ca between preparturition and just after parturition was under -20% in 3 of 8 cows, and low TRAP activities were observed in 2 of these 3 cows. This study suggests that cows with a low TRAP activity are at risk of developing milk fever in comparison to cows with high TRAP activity. Temporary increases of parathyroid hormone were observed in 7 cows, but not in the cow with milk fever.     

A proposed modulatory role of the endocannabinoid system on adipose tissue metabolism and appetite in periparturient dairy cows

To sustain the nutrient demands of rapid fetal growth, parturition, and milk synthesis, periparturient dairy cows mobilize adipose tissue fatty acid stores through lipolysis. This process induces an inflammatory response within AT that is resolved as lactation progresses; however, excessive and protracted lipolysis compounds the risk for metabolic and inflammatory diseases. The suppression of lipolytic action and inflammation, along with amplification of adipogenesis and lipogenesis, serve as prospective therapeutic targets for improving the health of periparturient dairy cows. Generally, the activation of cannabinoid receptors by endocannabinoids enhances adipogenesis and lipogenesis, suppresses lipolysis, and increases appetite in mammals. These biological effects of activating the endocannabinoid system open the possibility of harnessing the endocannabinoid system through nutritional intervention in dairy herds as a potential tool to improve dairy cows' health, although much is still to be revealed in this context. This review summarizes the current knowledge surrounding the components of the endocannabinoid system, elaborates on the metabolic effects of its activation, and explores the potential to modulate its activity in periparturient dairy cows.     

过瘤胃蛋白和丙二醇对乳牛瘤胃发酵、产乳量及乳成分的影响

用 8头荷斯坦黑白花奶牛 ,在饲粮中添加过瘤胃蛋白和丙二醇 ,研究其对乳牛瘤胃发酵、产乳量及乳成分的影响。结果表明 ,过瘤胃蛋白+丙二醇可显著提高丙酸浓度 (P <0 0 5) ,并且产乳量较对照组有增加的趋势。乳脂率、乳蛋白率、乳糖率及无脂固形物率 ,并未因添加过瘤胃蛋白和丙二醇而受到显著影响 (P >0 0 5)。乳蛋白质量、乳脂量及无脂固形物量 ,过瘤胃蛋白 +丙二醇组较对照组有增加的趋势 ,但差异均不显著 (P >0 0 5)。