Dose-dependent effects of rumen-protected choline on hepatic metabolism during induction of fatty liver in dry pregnant dairy cows.

Objectives were to determine the effects of supplementing increasing amounts of choline ion on hepatic composition and mRNA abundance in pregnant dry cows subjected to a fatty liver induction protocol. Holstein cows (35 primiparous and 41 multiparous) at mean (± standard deviation) of 211 ± 9.9 days of gestation were blocked by body condition (3.59 ± 0.33) and assigned to receive 0, 6.45, 12.90, 19.35, and 25.80 g/day of choline ion as rumen-protected choline (RPC) as a top-dress for 14 days. Cows were fed for ad libitum intake on days 1 to 5 and restricted to 30% of the required net energy for lactation from days 6 to 14 of the experiment. Hepatic tissue was sampled on days 5 and 14 and analyzed for concentrations of triacylglycerol and glycogen, and mRNA abundance was investigated. Orthogonal contrasts evaluated the effects of supplementing RPC (0 g/day vs. rest), and the linear, quadratic, and cubic effects of increasing intake of choline ion from 6.45 to 25.80 g/day. Results are depicted in sequence of treatments from 0 to 25.8. During feed restriction, RPC reduced the concentration of hepatic triacylglycerol by 28.5% and increased that of glycogen by 26.1%, and the effect of increasing RPC intake on triacylglycerol was linear (6.67 vs. 5.45 vs. 4.68 vs. 5.13 vs. 3.81 ± 0.92% wet-basis). Feeding RPC during feed restriction increased abundance of transcripts involved in choline metabolism (CHKA, PLD1), synthesis of apolipoprotein-B100 (APOB100), and antioxidant activity (GPX3), and decreased the abundance of transcripts involved in hepatic lipogenesis (DGAT2, SREBF1) and acute phase response (SAA3). Most effects were linear with amount of choline fed. Changes in hepatic mRNA abundance followed a pattern of reduced lipogenesis and enhanced lipids export, which help explain the reduced hepatic triacylglycerol content in cows fed RPC. Choline exerts lipotropic effects in dairy cows by altering transcript pathways linked to hepatic lipids metabolism.

Feeding supplemental 25-hydroxyvitamin D3 increases serum mineral concentrations and alters mammary immunity of lactating dairy cows.

Objectives were to determine the effects of feeding supplemental 25-hydroxyvitamin D3 [25(OH)D3] on concentrations of vitamin D metabolites and minerals in serum, mammary immune status, and responses to intramammary bacterial infection in dairy cows. Sixty multiparous, pregnant lactating Holstein cows with somatic cell count <200,000/mL were blocked by days in milk and milk yield and randomly assigned to receive a daily top-dressed dietary supplement containing 1 or 3 mg of vitamin D3 (1mgD or 3mgD), or 1 or 3 mg 25(OH)D3 (1mg25D or 3mg25D) for 28 d (n = 15/treatment). Cows were kept in a freestall barn and fed a total mixed ration in individual feeding gates. Individual dry matter intake (DMI) and milk yield were recorded daily, and milk and blood samples were collected at 0, 7, 14, and 21 d relative to the start of treatment. At 21 d, cows fed 1mgD and 3mg25D received an intramammary challenge with Streptococcus uberis. Cows were observed for severity of mastitis, and blood and milk samples were collected every 12 h to measure inflammation. The 1mg25D and 3mg25D cows had greater serum 25(OH)D3 concentrations at 21 d compared with 1mgD and 3mgD cows (62 ± 7, 66 ± 8, 135 ± 15, and 232 ± 26 ng/mL for 1mgD, 3mgD, 1mg25D, and 3mg25D, respectively). The 3mg25D cows had greater concentrations of Ca and P in serum at 21 d compared with other treatments (Ca = 2.38, 2.4, 2.37, and 2.48 ± 0.02 mM, 1.87, 1.88, and 2.10 ± 0.08 mM for 1mgD, 3mgD, 1mg25D, and 3mg25D, respectively). Yields of milk and milk components, DMI, body weight, and concentrations of 1,25-dihydroxyvitamin D and Mg in serum did not differ among treatments. Abundance of mRNA transcripts for interleukin-1ß (IL1B) and inducible nitric oxide synthase (iNOS) in milk somatic cells before S. uberis challenge were increased in cows fed 25(OH)D3 compared with cows fed vitamin D3. Furthermore, IL1B, iNOS, ß-defensin 7, and ß-defensin 10 in milk somatic cells increased as concentrations of 25(OH)D3 increased in serum. Cows fed 3mg25D had less severe mastitis at 60 and 72 h after challenge with S. uberis compared with cows fed 1mgD. Concentrations of bacteria, somatic cells, and serum albumin in milk after challenge did not differ between treatments; however, an interaction between treatment and day was detected for lactate dehydrogenase in milk. Expression of adhesion protein CD11b on milk neutrophils after the S. uberis challenge was greater among 3mg25D cows compared with 1mgD cows. Transcripts of CYP24A1 and iNOS in milk somatic cells during mastitis also were greater in 3mg25D cows compared with 1mgD cows. Feeding 25(OH)D3 increased serum 25(OH)D3 more effectively than supplemental vitamin D3, resulting in increased serum mineral concentrations, increased expression of vitamin D-responsive genes, and altered immune responses to intramammary bacterial challenge.

A bioactive extract from Olea europaea protects newly weaned beef heifers against experimentally induced chronic inflammation1.

Weaning is one of the most stressful periods in the life of a ruminant. Several factors entrenched within typical management practices pose challenges to the calf gastrointestinal health. Weaning is associated with losses in BW and feed intake. In addition, increasing highly fermentable carbohydrates in the diet at the expense of physically effective fiber after weaning predisposes the development of rumen acidosis and increases the concentration of endotoxin in rumen fluid and the permeability of the lower gut to luminal contents. Endotoxin translocation can elicit immune activation, shifting the metabolic priorities toward the immune system, which if sustained over time can hinder animal health and performance. Strategic supplementation of additives with anti-inflammatory capacity could represent a suitable approach to decrease systemic inflammation, restoring barrier function to luminal contents. Bioactive extracts from Olea europaea have anti-inflammatory activity and have been shown to reduce systemic inflammation in other animal models. A generalized randomized block design was used to evaluate the impact of feeding an olive oil bioactive extract (OBE) to newly weaned heifers injected intravenously with sequentially increasing doses of lipopolysaccharide (LPS). A total of 36 heifers, distributed across 3 experimental periods, were randomly assigned to 1 of 4 treatments that consisted of intravenous injection of either saline (CTL-) or with 6 sequentially increasing doses of LPS (0.10, 0.25, 0.50, 0.75, 1.00, and 1.25 µg/kg of BW) over a 10-d period (CTL+), and CTL+ plus dietary supplementation with a low (OBE-L; 0.04% of diet DM) or a high (OBE-H; 0.16% of diet DM) dose of OBE. Feeding OBE reduced some of the negative effects of prolonged immune activation with LPS, such as improved DMI and decreased intravaginal temperature in some, but not all of the days of LPS challenge (P < 0.05). In addition, feeding OBE reduced circulating concentration of inflammatory markers such as IL-6 and haptoglobin (P < 0.05). Heifers supplemented with OBE had reduced cell surface expression of the cluster of differentiation 14 (CD14) in monocyte cells (P < 0.01), a key receptor for LPS recognition, which was correlated with a faster recovery of immune cell counts in plasma. In conclusion, dietary supplementation with OBE was successful in mitigating the negative effects of sustained immune activation in newly weaned heifers.