Warren Matthew F, Vu Thien C, Toomer Ondulla T, Fernandez Juan David, Livingston Kimberly A
Prestage Department of Poultry Science, North Carolina State University, Raleigh, NC, United States.
United States Department of Agriculture, Agricultural Research Service, Raleigh, NC, United States.
Front Vet Sci. 2020 Jun 10;7:245. doi: 10.3389/fvets.2020.00245. eCollection 2020.
Increasing biopotency of cholecalciferol (D) from vitamin sources is essential in the poultry industry to meet nutritional demands and counter stressors. D exhibits hormonal traits and is responsible for calcium (Ca) absorption. 1-α-Hydroxycholecalciferol (1α) is a synthetic form of D that has equal efficacy and is cheaper to synthesize than 1,25-dihydroxycholecalciferol (active form of D), on broilers. However, 1α bypasses a critical regulatory point, the kidney, and may consequently lead to toxicity levels of Ca via Ca absorption. This study examined 1α supplementation in broiler diets with different Ca inclusion levels to determine if 1α at higher Ca levels caused Ca toxicity at starter and grower phases with Ross 708 male broiler chicks. In Experiment 1 (1-15 days of age), chicks were assigned to one of 10 treatment starter diets with five levels of Ca inclusion (0.80, 0.95, 1.10, 1.25, and 1.40%) with or without 1α supplementation (5 μg 1α/kg in feed) and eight replicate cages per treatment. In Experiment 2, chicks were fed common starter diet until 16 days of age, and then they were assigned to one of eight treatment diets with four levels of Ca inclusion (0.54, 0.76, 0.98, or 1.20%) with or without 1α supplementation (5 μg 1α/kg in feed). At the end of both experiments, blood was collected from broilers to determine blood chemistry, including concentrations of vitamin D metabolites. Intestinal tissues were also collected to examine gene expression. In Experiment 1, broilers not fed 1α exhibited a quadratic effect in ionized blood Ca (iCa) as dietary Ca inclusion levels increased; 1α-fed broilers displayed an increase in iCa as Ca inclusion levels increased ( = 0.0002). For Experiment 2, 1α-fed broilers displayed a decrease in 25-hydroxycholecalciferol plasma concentration as dietary Ca inclusion levels increased ( = 0.035); also, increasing Ca inclusion in diets increased expression of duodenal sodium phosphate cotransporter type II b (NPTIIb, = 0.03). Our findings imply that inclusion of 1α was beneficial because 1α enhanced Ca absorption during the starter phase; however, to avoid potential Ca toxicity or antagonism while using 1α during the grower phase, there should be consideration with reducing dietary Ca levels.
提高来自维生素源的胆钙化醇（D）的生物效价对于家禽业满足营养需求和应对应激源至关重要。D具有激素特性，负责钙（Ca）的吸收。1-α-羟基胆钙化醇（1α）是D的一种合成形式，其效力相同，且在肉鸡上比1,25-二羟基胆钙化醇（D的活性形式）合成成本更低。然而，1α绕过了一个关键的调节点——肾脏，因此可能通过钙吸收导致钙中毒水平。本研究检测了在不同钙添加水平的肉鸡日粮中添加1α的情况，以确定在罗斯708雄性肉鸡雏鸡的育雏期和生长期，较高钙水平下的1α是否会导致钙中毒。在实验1（1至15日龄）中，雏鸡被分配到10种处理的育雏日粮之一，其中钙添加水平有五个（0.80%、0.95%、1.10%、1.25%和1.40%），添加或不添加1α（饲料中5μg 1α/kg），每个处理有8个重复笼。在实验2中，雏鸡饲喂普通育雏日粮至16日龄，然后被分配到8种处理日粮之一，其中钙添加水平有四个（0.54%、0.76%、0.98%或1.20%），添加或不添加1α（饲料中5μg 1α/kg）。在两个实验结束时，从肉鸡采集血液以测定血液生化指标，包括维生素D代谢物的浓度。还采集肠道组织以检测基因表达。在实验1中，未饲喂1α的肉鸡随着日粮钙添加水平的增加，其离子化血钙（iCa）呈现二次效应；饲喂1α的肉鸡随着钙添加水平的增加，iCa升高（P = 0.0002）。对于实验2，饲喂1α的肉鸡随着日粮钙添加水平的增加，其25-羟基胆钙化醇血浆浓度降低（P = 0.035）；此外，日粮中钙添加量增加会使十二指肠IIb型钠磷共转运体（NPTIIb）的表达增加（P = 0.03）。我们的研究结果表明，添加1α是有益的，因为1α在育雏期增强了钙的吸收；然而，为了在生长期使用1α时避免潜在的钙中毒或拮抗作用，应考虑降低日粮钙水平。
