Effects of OmniGen AF feed supplementation on glucocorticoids, blood leukocyte messenger RNA abundance, and energy metabolism in overstocked Holstein dairy cows

The physiological consequences of overstocking require more investigation, and no research has explored whether dietary supplements could mitigate the anticipated negative physiological effects. OmniGen AF (OG, Phibro Animal Health Corporation, Teaneck, NJ, USA) is a nutritional supplement that has been shown to support the immune system of cattle following internal and environmental stressors. This study aimed to determine if a 45-day period of OG feed supplementation would influence whole blood leukocyte messenger RNA abundance, energy metabolism and glucocorticoid concentration, during a two-week period of overstocking. Two stocking density treatments (control: one headlock and lying stall per cow; overstocked: 0.5 headlocks and 0.5 lying stalls per cow) and two diet treatments (control: no added supplement; and OG: 56 g/cow per day) were investigated. Four pens of 15 cows were fed their assigned diet (two pens per diet; control stocking density) for 45 days after which each stocking density treatment was applied for a 14-day period using a cross-over design; this study design was replicated twice. During each 14-day period, blood was collected on day four to measure whole blood leukocyte messenger RNA abundance (cluster of differentiation 80, interleukin 8 receptor-beta, interleukin 10 receptor-beta and L-selectin) and fecal samples were collected every two days to measure fecal cortisol metabolite concentration (11,17-dioxoandrostanes). At the end of each 14-day period, eight cows from each pen were selected for an intravenous glucose tolerance test; glucose, insulin and non-esterified fatty acids were measured. There were no effects of diet or stocking density on leukocyte messenger RNA abundance. Fecal cortisol metabolite concentrations were highest for overstocked cows on the control diet on day four of the stocking density treatment; however, by day 10, overstocked cows fed OG had the highest fecal cortisol metabolite concentrations. Overstocked cows, regardless of diet, had an attenuated insulin response during the glucose tolerance test, represented by a lower area under the curve estimate. Cows fed OG but not overstocked, had a lower non-esterified fatty acid nadir during the glucose challenge, compared to all the other treatments. In conclusion, overstocking prompts a physiological stress response and alters energy metabolism by decreasing the insulin response to an intravenous glucose challenge. Feeding OG during overstocking delayed the increase in fecal cortisol metabolites by several days; however, it is unclear if this altered glucocorticoid response benefited the cow, as OG had no effect on insulin responses or immune parameters.

Effect of withdrawing an immunomodulatory feed additive from lactating cow diets on peripheral blood mononuclear cell proliferation

Supplementation of immunomodulatory feed additives, such as OmniGen AF (OG), helps to maintain immune competency; however, it is unknown if immune benefits persist in lactating cows after OG is removed from the diet. The aim of this trial was to evaluate the effect of withdrawing OG from the diet on peripheral blood mononuclear cells (PBMC) proliferation of midlactation dairy cows. Multiparous Holstein cows (N = 32), blocked by parity (2.7 ± 0.8) and days in milk (153 ± 39 d) were randomly assigned to one of the two dietary treatments within each block: diets were top dressed with either OG (56 g/d/cow) or placebo (CTL, 56 g/d/cow). Cows were housed in the same free-stall pen and individually fed once per day through Calan gates. All cows were fed the same diet containing OG for at least 1 yr before the onset of treatments. Cows were milked three time per day and milk yield was recorded at each milking. Milk samples were collected from three consecutive milkings weekly and composition analyzed. Body weight (BW) and condition score were measured weekly. Blood samples were collected at -1, 1, 3, 5, and 7 wk relative to the onset of treatments for the isolation of PBMC. The PBMC were cultured with concanavalin A (ConA) and lipopolysaccharides (LPS) for 72 h in vitro to determine proliferative responses. Prior to the experiment, cows in both treatments had similar disease incidence. During the experiment, cows did not show symptoms of disease. Withdrawing OG from the diet did not affect (P ≥ 0.20) milk yield or composition, intake, or BW. Compared with CTL, feeding OG maintained greater body condition score (2.83 vs. 2.92, P = 0.04). Regardless of time, relative to CTL, PBMC isolated from cows fed with OG had a greater proliferative rate when stimulated with LPS (stimulation index: 1.27 vs. 1.80, P = 0.05) and tended to have greater proliferation when stimulated with ConA (stimulation index: 5.24 vs. 7.80, P = 0.08). In conclusion, withdrawing OG from the diet of midlactation cows reduced proliferative response of PBMC suggesting that the immunomodulatory role of OG is lost as early as 1 wk after its withdrawal from the diet of lactating dairy cows.

Effect of an Immunomodulatory Feed Additive in Mitigating the Stress Responses in Lactating Dairy Cows to a High Concentrate Diet Challenge

Dairy cows are often exposed to multiple stressors in a lactation-cycle, with sub-acute ruminal acidosis (SARA) a frequent example of nutritional stress. SARA affects ruminal and intestinal equilibrium resulting in dysbiosis with localized and systemic inflammation impacting animal health and productivity. OmniGen-AF (OMN, Phibro Animal Health Corporation, Teaneck, NJ, USA) is a feed product recognized for modulating innate immune function, especially during periods of stress. The objective of this study was to determine the effects of OMN in lactating dairy cows fed a high-starch, low-fiber diet. Twenty-four blocked cows were assigned to control or treatment (55 g/d). After the additive adaptation (49 d) cows were fed the challenge diet (28 d). Milk, rumination and pH were continuously recorded; components, rumen fluid, and blood were taken in multiple time-point and analyzed. Results showed that the challenge decreased the rumination, shifted ruminal fluid composition, decreased milk production and the components, and slightly increased the time below pH 5.5, with no differences between groups. The treatment produced greater rumen butyrate and lower lactate, prompter regeneration of red blood cells, increase of neutrophils, lower paraoxonase, gamma-glutamyl-transferase, and β-hydroxybutyrate, with no differences on other tested inflammatory markers. Results show that OMN helps modulating some of the metabolic and immunological responses to SARA.

Impact of heat stress and a feed supplement on hormonal and inflammatory responses of dairy cows

The aim of this trial was to evaluate the effects of an immunomodulatory supplement (OmniGen AF, OG; Phibro Animal Health Corp.) and heat stress on hormonal, inflammatory, and immunological responses of lactating dairy cows. Sixty multiparous Holstein cows were randomly assigned to 4 treatments in a 2 × 2 factorial arrangement using 2 environments: cooled using fans and misters, or noncooled, and 2 top-dressed feed supplements (56 g/d): OG or a placebo (CTL). Temperature-humidity index averaged 78 during the 8-wk trial. Blood was drawn to analyze cortisol, prolactin, and circulating tumor necrosis factor (TNF)-α and IL-10. Peripheral blood mononuclear cells (PBMC) were isolated and stimulated with hydrocortisone, prolactin, or lipopolysaccharide (LPS), individually or in several combinations, to assess induced proliferation and cytokine production. At d 52, 6 cows per treatment were injected i.v. with an LPS bolus (ivLPS) to assess hormone and cytokine responses. For cooled cows, feeding OG increased plasma cortisol concentration relative to CTL. Noncooled cows fed CTL had lower circulating TNF-α concentrations than noncooled-OG and cooled-CTL cows, with cooled-OG intermediate. Hydrocortisone+LPS-stimulated PBMC from OG cows tended to proliferate more than CTL. Relative to cooled cows, PBMC from noncooled cows produced more TNF-α and IL-10 when stimulated with LPS. Following ivLPS, cooled-OG cows had a greater cortisol response than the other treatments. In conclusion, OG supplementation enhanced cortisol release under basal condition and induced inflammation with cooling compared with CTL. This suggests that heat stress inhibits OG-mediated cortisol release. Heat stress seemed to enhance the inflammatory responses of PBMC from lactating cows. However, OG supplementation promoted PBMC proliferation under stress, or in the presence of hydrocortisone.

Influence of an immune-modulatory feed supplement on performance and immune function of beef cows and calves preweaning

The ability to positively alter immune and stress response with nutritional compounds is of great interest and importance to the beef industry. There is a proprietary product (OmniGen-AF [OG]; Phibro Animal Health, Quincy, IL) reported to have performance-enhancing benefits by altering animal response to stress and immune challenges. The objective of this 2-yr research project was to study the effect of supplementing OG to beef cows and their calves on breeding and growth performance. One hundred and twelve multiparous beef cows and 48 primiparous cows were randomly assigned to treatment in year 1; control (CON, no OG; n = 56 multiparous and 24 primiparous) or treatment (OG fed at 8.8 g/100 kg body weight [BW]; n = 56 multiparous and 24 primiparous). Multiparous cows (mean ± SD = 6.4 ± 0.4 yr; BW = 589 ± 9.2 kg; body condition score [BCS] 6.2 ± 0.07) were used in both years of the experiment and primiparous cows (mean ± SD = 2.1 ± 0.04 yr of age, weighed 400 ± 7.5 kg, and BSC of 5.6 ± 0.06) were only used in the first year of the experiment. CON and OG supplements were offered over two production cycles beginning in December approximately 60 d prior to projected calving through pre-breeding in May of each year. Calves from treatment cows were offered treatments in a creep supplement limited to a daily rate of 1% as-fed of BW prorated for 3-d/wk feeding from mid-July through weaning with OG offered at 8.8 g/100 kg BW. Primiparous cow's BW, BCS, and calf performance were not affected by treatment (P ≥ 0.15) in year 1. BW of multiparous OG cows tended (P = 0.10) to be heavier at weaning in year 1 and was greater (P = 0.05) at the onset of the experiment in year 2. Body condition of OG cows was greater (P ≤ 0.02) at weaning in both years 1 and 2, as well as at the onset of the experiment in year 2. Calves fed OG from the mature cows gained more (P = 0.05) BW during the creep feeding period than CON. Core body temperatures of OG heifers measured during the late summer with intravaginal temperature data loggers tended (P ≤ 0.10) to be less at 1400 and 1700 hours and were less (P = 0.05) at 1800 hours than CON heifers. Feeding OG did not result in changes (P = 0.25) in serum titer response to the BVD virus of calves during year 2. The results of the current experiment indicate feeding OG to beef cows and calves can result in improvement in BCS of cows, enhance weight gain of calves preweaning, and reduce heat loads in heifer calves during the late summer.

Response to adrenocorticotropic hormone or corticotrophin-releasing hormone and vasopressin in lactating cows fed an immunomodulatory supplement under thermoneutral or acute heat stress conditions

Adrenal responsiveness was tested in nonpregnant, lactating Holstein dairy cows fed diets supplemented with OmniGen-AF (OG; Phibro Animal Health Corp., Teaneck, NJ), an immune modulator, and in nonsupplemented control (CON) cows following bolus infusions of a combination of corticotropin-releasing hormone (CRH; 0.3 µg/kg of BW) and arginine vasopressin (VP; 1.0 µg/kg of BW) or ACTH (0.1 IU/kg of BW) in 2 environments: thermoneutral [TN; temperature-humidity index (THI) <60] for 24 h/d and heat stress (HS; THI >68 for 17 h/d). Cows (506) were initially fed OG (n = 254) or CON (n = 252) diets for 44 d before selection of a subgroup of cows (n = 12; 6 OG, 6 CON) for the study. The 2 subgroups were balanced for parity, milk yield, and days in milk. All cows were transported to and housed in 2 environmentally controlled rooms at the University of Arizona Agricultural Research Complex (Tucson). Cows were given 3 d to acclimate to the rooms and then underwent 12 d of TN conditions and then 8 d of HS conditions for a total of 24 d on experiment. Cows were infused with CRH-VP on d 9 of TN and on d 1 of HS and with ACTH on d 10 of TN and on d 2 of HS. Hormone infusions took place at 1000 h (0 h) on each infusion day. Blood samples, taken in 30-min intervals, were first collected at 0800 h (-2 h) and were drawn until 1800 h (8 h). Before infusion, serum progesterone was elevated in OG cows compared with CON cows. Infusion of releasing factors (CRH-VP or ACTH) caused increases in serum cortisol and progesterone, but cortisol release was greater in CON cows than in OG cows during HS, whereas progesterone did not differ between the 2 treatments. Serum ACTH increased following infusion of releasing factors, but this increase was greater following CRH-VP infusion than ACTH infusion. Serum bovine corticosteroid-binding globulin also increased following infusion of releasing factors in both treatment groups, but this increase was greater during HS in cows fed OG. The free cortisol index (FCI) increased following CRH-VP and ACTH and was higher in HS than in TN for both OG and CON cows. However, the FCI response was blunted in OG cows compared with CON cows during HS. Heat stress enhanced the adrenal response to releasing factors. Additionally, the adrenal cortisol and FCI response to releasing factors was reduced during acute heat stress in cows fed OG. Collectively, these data suggest that OG supplementation reduced the adrenal responsiveness to factors regulating cortisol secretion during acute HS.

Effects of an immunomodulatory feed additive on intramammary infection prevalence and somatic cell counts in a dairy herd experiencing major health issues

A trial was conducted to determine if feeding OmniGen-AF® (OG) to 22 late lactation cows 60 days prior to and during the early dry period, a time of increased susceptibility to mastitis, could reduce disease incidence in a dairy herd experiencing major health issues. Treated cows (n = 11) consumed a ration containing OG [9 g/100 kg of body weight/day] beginning 60 days before dry-off, during the dry period, and through 30 days in milk (DIM). Control cows received the same ration during the dry period through 30 DIM only. Body weights, body condition scores (BCS), intramammary infection (IMI) prevalence, new IMI rates, somatic cell counts (SCC), milk yield, and adverse health events were measured. No differences were found between treatments for body weight or BCS. Adverse health event data at calving showed no differences between treatments except for percentage of cows with hyperketonemia, which was lower among treated cows (63.6% vs 100%). Prevalence of IMI from calving through 30 DIM for treated cows (6.1%) was lower than controls (11.05%); likewise, new IMI rate during this time for treated cows (0.61%) was lower than controls (5.81%). The SCC from calving through 30 DIM for treated cows (215,000/ml) was lower than controls (493,000/ml). Average production/day at the first DHIA test (~33 DIM) showed that treated cows produced more milk (39.9 kg) than controls (35.34 kg). In conclusion, feeding OG 60 days prior to dry-off reduced hyperketonemia and mastitis, lowered SCC, and numerically increased milk yield in a dairy herd experiencing major health issues.