Magnesium absorption as influenced by the rumen passage kinetics in lactating dairy cows fed modified levels of fibre and protein

Magnesium in dairy cattle nutrition: A meta-analysis on magnesium absorption in dairy cattle and assessment of simple solubility tests to predict magnesium availability from supplemental sources

Supplemental Mg sources differ in bioavailability, and solubility is one of the determining factors. We explored whether and which in vitro solubility tests could reliably differentiate the quality of supplemental Mg sources. In experiment 1, we compared 3 chemical methods using an acetic acid solution (50 mL/L, termed vinegar test), a 1 M ammonium nitrate solution, and an artificial rumen buffer fluid without rumen microbiota. The Mg solubility results suggested the vinegar test was the best method due to its robustness, simplicity, and reproducibility. In experiment 2, we validated the reliability of the vinegar test using 4 MgO sources from experiment 1 and 12 new MgO sources plus a laboratory-grade MgO as a standard. Accordingly, we repeated the vinegar test with short (0.5 h) and long (3.0 h) incubation times on these sources and then conducted ruminal incubations in 24-h batch culture experiments. The repeated vinegar test resulted in similar results as in experiment 1. Linear regression across both experiments showed the soluble Mg content (g/kg) = 44.46 (±2.55) × pH - 142.9 (±14.9), root mean square error (RMSE) = 10.2, P slope <0.001, and concordance correlation coefficient (CCC) = 0.953. The predictable pH range was from 4 to 6. The equation cannot be applied to low-alkaline sources such as Mg sulfate, Mg acetate, or a group of MgO with exceptionally high alkaline properties showing a cluster of pH above 8.5. Solubility of the MgO sources in the vinegar test ranged from 5 to 35%, whereas the 24-h ruminal incubations led to more solubility (15-70%). Nevertheless, the differences among most MgO sources were parallel to the data from the in vitro rumen solubility. Next, we performed a meta-analysis of published studies (21 studies, 94 treatments) to assess the true Mg absorption in vivo and potential factors affecting Mg absorption in dairy cows. It appeared that on average dairy cows absorbed about 20% of the Mg intake (range 10-40%), regardless of their lactation status. We revealed a new strategy to predict Mg absorption relative to dietary K as follows: true Mg absorption (g/d) = 0.3395 (±0.025, P < 0.001) × Mg intake (g/d) - 1.9273 (±1.16, P = 0.11) when dietary K ≤20 g/kg DM, and 0.154 (±1.06, P = 0.05) + 0.209 (±0.026, P < 0.001) × Mg intake (g/d) when dietary K >20 g/kg DM (RMSE = 2.19). This strategy improved the accuracy of prediction as compared with the existing prediction (CCC = 0.922 vs. 0.845). Still, over- or underestimations inherent to individual studies were evident and might be related to unaccountable factors, especially the quality of supplemental Mg sources. In conclusion, the vinegar test is a useful tool to rank inorganic Mg sources with alkaline properties. Including in vitro solubility data in Mg nutrition research could help to refine the prediction of bioavailable Mg contents and increase precision in feed formulation.

Effects of Different Yeast Selenium Levels on Rumen Fermentation Parameters, Digestive Enzyme Activity and Gastrointestinal Microflora of Sika Deer during Antler Growth

The aim of this experiment was to study the effects of different selenium supplemental levels on rumen fermentation microflora of sika deer at the velvet antler growth stage. A total of 20 5-year-old, healthy sika deer at the velvet antler growth stage with an average body weight of (98.08 ± 4.93) kg were randomly divided into 4 groups, and each group was fed in a single house. The SY1 group was the control group, and the SY2 group, SY3 group and SY4 group were fed a basal diet supplemented with 0.3, 1.2 and 4.8 mg/kg selenium, respectively. The pretest lasted for 7 days, and the formal trial period lasted for 110 days. The results show that: At the velvet antler growth stage, the digestibility of neutral detergent fiber and acid detergent fiber of sika deer in the SY2 group was significantly higher than that in the control group (p < 0.01). The digestibility of cellulose and crude fiber of sika deer in the SY2 group was significantly higher than those in the SY3 and SY4 groups (p < 0.01) and significantly higher than that in the control group (p < 0.05). The contents of acetic acid and propionic acid in the rumen fluid of sika deer in the SY2 group were significantly higher than those in the SY1 group (p < 0.05). Digestive enzyme analysis of rumen fluid at the velvet antler growth stage showed that the activity of protease in rumen fluid in the SY2 group was significantly lower than those in the SY1 group and SY4 group (p < 0.05). The relative abundance of Fibrobacter succinogenes in the SY2 group was significantly higher than that in the SY1 group (p < 0.05) and extremely significantly higher than those in the SY3 and SY4 groups (p < 0.01). Correlation analysis between yeast selenium level and bacterial abundance showed that the yeast selenium content in rumen fluid was significantly positively correlated with Butyrivibrio and Succiniclasticum (p < 0.01). Further verification of bacterial flora functioning showed that the SY2 group was more inclined to the degradation and utilization of fiber. In conclusion, 0.3 mg/kg selenium supplementation can increase the abundance of Prevotella ruminicola and Fibrobacter succinogenes in the rumen of sika deer and improve the degradation of fibrous substances by mediating the catabolite repression process.

Potential of a rumen bolus containing 1,25-dihydroxyvitamin D3 glycosides for the prevention of hypocalcaemia in primiparous and multiparous dairy cows

Periparturient hypocalcaemia is a widespread metabolic disorder in dairy cows. Clinical and subclinical cases occur primarily in multiparous (Multi) cows, but subclinical cases have also been reported in primiparous (Primi) cows. A preventive strategy was investigated by administering the physiologically active vitamin D₃ metabolite, 1,25-dihydroxyvitamin D₃ (1,25-dihydroxycholecalciferol, 1,25(OH)₂D₃) as a rumen bolus. The bolus contained tablets of 1,25(OH)₂D₃ glycoside extract from Solanum glaucophyllum (SGE), releasing SGE over several days. The aim was to study the effect of a bolus containing 0 (C) or 500 µg (SGE) of 1,25(OH)₂D₃ on 1,25(OH)₂D₃ and mineral status in periparturient cows up to three weeks into lactation and on colostrum, milk and calves' blood mineral contents. The bolus was administered three to four days prior to expected calving to Primi and Multi cows fed a herbage-based diet (dietary cation-anion difference of +522 mEq/kg DM). One C or SGE bolus was applied to 12 Primi and 12 Multi cows. Blood was regularly sampled (and selected a posteriori for antepartum samples) in regard to the actual calving day (d0), immediately prior to bolus application and at day -2, 0.5, 1, 1.5, 2, 4, 8, 11, 15, 18 and 22. Additional samples included urine (at bolus application, d0.5 and d2), colostrum, milk samples (weekly) and calves' blood (d2). Blood serum 1,25(OH)₂D₃ increased between d0.5 and d2 in Primi-SGE, but remained unchanged in Primi-C, as did parathyroid hormone (PTH) and Ca in all Primi. Urinary Ca of Primi-SGE was increased on d2, indicating regulation of Ca excess. Three Multi-C cows with confirmed clinical hypocalcaemia needed treatment and thus were excluded from the dataset and replaced. Blood serum 1,25(OH)₂D₃ and PTH increased while Ca dropped by 40% between d0.5 and d2 in Multi-C, whereas 1,25(OH)₂D₃, Ca and PTH remained unchanged in Multi-SGE. Blood serum carboxyterminal telopeptide of type I collagen was higher in Primi than in Multi and increased with time, except in Primi-C. Mineral contents in colostrum, milk and blood serum of calves were not influenced to a relevant degree. In conclusion, Primi-C did not, in contrast to Multi-C, develop subclinical hypocalcaemia (<2.0 mmol Ca/l). Prevention of hypocalcaemia with one SGE bolus applied three to four days prior to expected calving was successful in maintaining blood Ca within normal range in Multi over the critical first two days and up to the first three weeks of lactation, without any observed detrimental effects on cows or calves.

Pharmacokinetics of 1,25-dihydroxyvitamin D3 glycosides from Solanum glaucophyllum extract given in a rumen bolus on blood mineral profiles in dry pregnant dairy cows

Providing tablets of 1,25-dihydroxyvitamin D3 (1,25(OH)2D3), the biologically active metabolite of vitamin D3, in a rumen bolus may be used as prevention for periparturient hypocalcemia in dairy cows. This study investigated the pharmacokinetics of 1,25(OH)2D3 glycosides extracted from Solanum glaucophyllum (SGE) on blood serum 1,25(OH)2D3, Ca, P and Mg response in dry pregnant dairy cows. Boluses contained tablets of SGE which differed in their release properties (rapid release, slow release and combination) and galenics (200 μg uncoated, 300 μg and 500 μg uncoated or coated, 2 × 500 μg uncoated). Nineteen blood samples were collected from 29 cows between 96 h before and 336 h after bolus administration. Blood serum 1,25(OH)2D3, Ca and P increased between 12 h and 120 h, 12 h and 264 h and 24 h and 264 h, respectively. Highest values were reached at 30 h, 72 h and 120 h for 1,25(OH)2D3, Ca and P, respectively. Baseline values were then reached at 216 h for 1,25(OH)2D3 and 336 h for Ca and P. Concentration of Mg decreased between 24 h and 216 h, before reaching values comparable to baseline at 264 h. Highest Ca values were obtained with the combined rapid and slow release properties (500 μg) and there was no effect from coating on pharmacokinetics. In conclusion, the antepartum oral SGE bolus administration may be suitable for the prevention of periparturient hypocalcemia.

Short term magnesium supplementation to reduce dark cutting in pasture finished beef cattle

This study assessed the capacity of magnesium supplementation to reduce muscle glycogen loss, ultimate pH and increase plasma magnesium in pasture fed slaughter cattle. Beef cattle (n = 1075) from 14 farms were supplemented with or without magnesium pellets for 7-14 days prior to slaughter. Magnesium was allocated at 9.83 g of elemental magnesium per head per day, while the control diet was balanced to be isoenergetic and isonitrogenous, but contained no added magnesium. Groups of cattle (n = 44) were slaughtered at the same processing plant over two consecutive seasons, from August - September 2016 to May - July 2017. Magnesium supplementation increased muscle glycogen (P < 0.01) in cattle supplied from 2 of 14 farms, and increased plasma magnesium in 4 of 14 farms (P < 0.01). Magnesium supplementation had no effect on overall incidence of ultimate pH between the magnesium and control supplementation groups. The benefits of short term magnesium supplementation prior to slaughter was inconsistent for protecting muscle glycogen.

Impact of Nutrients on the Hoof Health in Cattle

Lameness is currently one of the most important and economically demanding diseases in cattle. It is manifested in a change in locomotion that is associated with lesions, especially the pelvic limbs. The disease of the hoof is painful, affecting the welfare of dairy cows. Important factors that influence the health of the limbs include nutrition, animal hygiene, stable technology, and genetic and breeding predispositions. Nutrition is one of the basic preventive factors affecting the quality and growth of the hoof horn, and the associated prevalence of hoof disease. The strength and structure of the hoof horn are affected by the composition of the feed ration (amino acids, minerals, vitamins, and toxic substances contaminating the feed ration, or arising in the feed ration as metabolites of fungi).