Schmitt S, Mack J, Kienzle E, Alexander L G, Morris P J, Colyer A, Dobenecker B
Chair of Animal Nutrition and Dietetics, Ludwig-Maximilians-University Munich, Oberschleissheim, Germany.
WALTHAM® Centre for Pet Nutrition, Waltham-on-the-Wolds, UK.
J Anim Physiol Anim Nutr (Berl). 2018 Apr;102(2):e798-e805. doi: 10.1111/jpn.12837. Epub 2017 Nov 13.
According to a previous meta-analysis, adult dogs do not notably increase calcium absorption from the gastrointestinal tract when calcium intake is decreased. This results in a negative calcium balance even with a moderate calcium reduction. In this study we wanted to verify (i) whether a negative calcium balance occurs at a calcium intake equivalent to NRC (2006) (Nutrient requirements of dogs and cats, 2006, The National Academies Press, Washington, DC) minimal requirements, and if so (ii) whether the negative calcium balance will persist for up to 6 months on a low-calcium diet. After a pre-feeding period of at least 18 weeks with calcium intake slightly exceeding maintenance requirements (200 mg/kg body weight ), 12 dogs (6 Beagles, 6 Foxhound crossbreds) were fed a low-calcium diet for 28 weeks. One dog was removed from the trial for reasons unrelated to the study at week 23. Calcium intake amounted to 60 mg/kg body weight corresponding to the minimal requirement for maintenance in dogs (NRC, 2006 (Nutrient requirements of dogs and cats, 2006, The National Academies Press, Washington, DC)). Digestion trials were carried out at week 7, 14, 21 and 28 of the low calcium feeding period. At these time points, and at week 18 of the pre-trial, blood samples were taken and analysed for calcium, ionised calcium, phosphorus, parathyroid hormone, vitamin D, serum crosslaps and bone alkaline phosphatase. Apparent calcium digestibility was negative throughout the study, suggesting a negative calcium balance. There was no systematic decrease in faecal calcium excretion. Serum calcium, ionised calcium and phosphorus remained within the reference range. Serum crosslaps increased continuously from baseline to week 28 of trial, with averages increasing from 0.102 ng/ml to 0.279 ng/ml, suggesting osteoclastic activity, indicative of calcium mobilisation from the skeleton. The study supports the theory of a lack of adaptation of intestinal calcium absorption from diets with relatively low calcium content in dogs. This agrees with clinical findings in dogs eating low-calcium diet.
根据之前的一项荟萃分析，当钙摄入量减少时，成年犬不会显著增加胃肠道对钙的吸收。即使钙摄入量适度减少，也会导致钙平衡为负。在本研究中，我们想要验证：（i）当钙摄入量相当于美国国家研究委员会（NRC，2006）（《犬猫营养需求》，2006年，美国国家科学院出版社，华盛顿特区）的最低需求量时，是否会出现钙平衡为负的情况；如果是这样，（ii）低钙饮食下钙平衡为负的情况是否会持续长达6个月。在至少18周的预饲期内，钙摄入量略超过维持需求量（200毫克/千克体重），之后，12只犬（6只比格犬，6只猎狐犬杂交种）被喂食低钙饮食28周。在第23周时，有1只犬因与研究无关的原因退出试验。钙摄入量为60毫克/千克体重，相当于犬维持所需的最低需求量（NRC，2006（《犬猫营养需求》，2006年，美国国家科学院出版社，华盛顿特区））。在低钙饲喂期的第7、14、21和28周进行消化试验。在这些时间点以及试验前的第18周，采集血样并分析钙、离子钙、磷、甲状旁腺激素、维生素D、血清交联C末端肽和骨碱性磷酸酶。在整个研究过程中，表观钙消化率均为负值，表明钙平衡为负。粪便钙排泄量没有系统性下降。血清钙、离子钙和磷仍在参考范围内。血清交联C末端肽从基线到试验第28周持续增加，平均值从0.102纳克/毫升增加到0.279纳克/毫升，表明破骨细胞活性，提示有钙从骨骼中动员出来。该研究支持犬对钙含量相对较低的饮食中肠道钙吸收缺乏适应性的理论。这与食用低钙饮食的犬的临床发现一致。
