Subcutaneous lysophosphatidylcholine administration promotes a febrile and immune response in Holstein heifer calves.

Lysophosphatidylcholine (LPC) is immunomodulatory in nonruminants; however, the actions of LPC on immunity in cattle are undefined. Our objective was to study the effects of LPC administration on measures of immunity, liver health, and growth in calves. Healthy Holstein heifer calves (n = 46; age 7 ± 3 d) were randomly assigned to 1 of 4 treatments (n = 10 to 11 calves/treatment): a milk replacer diet unsupplemented with lecithin in the absence (CON) or presence of subcutaneously (s.c.) administered mixed (mLPC; 69% LPC-16:0, 25% LPC-18:0, 6% other) or pure LPC (pLPC; 99% LPC-18:0), or a milk replacer diet supplemented with 3% lecithin enriched in lysophospholipids containing LPC in the absence of s.c.-administered LPC (LYSO) for 5 wk. Calves received 5 s.c. injections of vehicle (10 mL of phosphate-buffered saline containing 20 mg of bovine serum albumin/mL; CON and LYSO) or vehicle containing mLPC or pLPC to provide 10 mg of total LPC per kilogram of BW per injection every 12 h during wk 2 of life. Calves were fed a milk replacer containing 27% crude protein and 24% fat at 1.75% of BW per day (dry matter basis) until wk 6 of life (start of weaning). Starter grain and water were provided ad libitum. Body measurements were recorded weekly, and clinical observations were recorded daily. Blood samples were collected weekly before morning feeding and at 0, 5, and 10 h, relative to the final s.c. injection of vehicle or LPC. Data were analyzed using a mixed model, with repeated measures including fixed effects of treatment, time, and their interaction. Dunnett's test was used to compare treatments to CON. Peak rectal temperatures were higher in mLPC or pLPC, relative to CON. Plasma LPC concentrations were greater in mLPC and LYSO calves 5 h and 10 h after the final injection, relative to CON. Calves receiving mLPC and pLPC also had higher circulating serum amyloid A concentrations, relative to CON. Calves receiving mLPC had greater serum aspartate aminotransferase, γ-glutamyltransferase, and glutamate dehydrogenase concentrations, relative to CON. Calves provided mLPC experienced lower average daily gain (ADG) after weaning, relative to CON. The LYSO treatment did not modify rectal temperatures, ADG, or measures of liver health, relative to CON. We conclude that LPC administered as s.c. injections induced an acute febrile response, modified measures of liver and immune function, and impaired growth in calves.

Effects of dietary organic acid and pure botanical supplementation on growth performance and circulating measures of metabolic health in Holstein calves challenged by heat stress.

To evaluate the effects of heat stress environmental conditioning and dietary supplementation with organic acid and pure botanicals (OA/PB) on growth in dairy calves, we enrolled 62 bull (noncastrated) and heifer calves in a study with a completely randomized design. Calves were assigned to 1 of 5 groups (n = 11 to 14/group): (1) thermoneutral conditions (TN-Con), (2) HS conditions (HS-Con), (3) thermoneutral conditions and pair-fed to match nutrient intake with HS-Con (TN-PF), (4) HS with low-dose OA/PB [75 mg/kg of body weight (BW); 25% citric acid, 16.7% sorbic acid, 1.7% thymol, 1.0% vanillin, and 55.6% triglyceride; HS-Low], or (5) HS with high-dose OA/PB (150 mg/kg of BW; HS-High). Supplements were delivered as a twice-daily bolus via the esophagus from wk 1 through 13 of life; all calves, including those on the control treatments, received an equivalent amount of triglyceride used for microencapsulation. Calves were raised in TN conditions from birth until weaning. After weaning, calves (62 ± 2 d; 91 ± 10.9 kg of BW) were transported to a new facility and remained in TN conditions [temperature-humidity index (THI): 60 to 69] for a 7-d covariate period. Thereafter, calves remained in TN or were moved to HS conditions (THI: diurnal change 75 to 83 during night and day, respectively) for 19 d. Clinical assessments were performed thrice daily, BW was recorded weekly, and blood was sampled on d 1, 2, 3, 8, 15, and 19. Upon experiment completion, calves from HS-Con and TN-Con were euthanized, and hot carcass and visceral organ weights were recorded. The mixed model included calf as a random effect; treatment, day, hour (when appropriate) as fixed effects, and the interactions of treatment × day and treatment × hour (when appropriate). Rectal and skin temperatures and respiration rates were greater in HS-Con than in TN-Con. During heat stress exposure, dry matter intake (DMI), average daily gain (ADG), and gain to feed (G:F) were lower in HS-Con relative to TN-Con. Comparing HS-Con and TN-PF, ADG and G:F were similar. Plasma fatty acid concentrations were elevated in TN-PF compared with HS-Con and TN-Con. Despite tendencies for increased aspartate aminotransferase, HS conditions did not overtly influence liver and inflammation markers. Liver weights were lower in HS-Con relative to TN-Con. During the first week of heat exposure, DMI was greater for HS-Low relative to HS-Con. Supplementation of OA/PB at low and high levels had a similar G:F to HS-Con. We conclude that reductions in DMI accounted for production losses during HS conditioning and that dietary OA/PB supplementation was not able to improve growth performance in heat-stressed calves.

Effects of dietary deoiled soy lecithin supplementation on milk production and fatty acid digestibility in Holstein dairy cows.

Deoiled soy lecithin is a feed additive enriched in phospholipids. Our study evaluated the effects of dietary deoiled soy lecithin supplementation on (1) milk production and composition, (2) plasma and milk fatty acid (FA) content and yield, and (3) apparent FA digestibility and absorption in lactating dairy cows fed fractionated palm fat. In a split-plot Latin square design, 16 Holstein cows (160 ± 7 days in milk; 3.6 ± 1.2 parity) were randomly allocated to a main plot receiving a corn silage and alfalfa haylage-based diet with palm fat containing either moderate (MPA) or high palmitic acid (HPA) content at 1.75% of ration dry matter (72 or 99% palmitic acid, respectively; n = 8/palm fat diet). On each palm fat diet, deoiled soy lecithin was top-dressed at 0, 0.12, 0.24, or 0.36% of ration dry matter in a replicated 4 × 4 Latin square design. Following a 14-d covariate period, lecithin supplementation spanned 14 d, with milk and blood collected during the final 3 d. Milk composition and pooled plasma markers were measured. The statistical model included the fixed effects of palm fat type, lecithin dose, period, and the interaction between palm fat type and lecithin dose. The random effect of cow nested within palm fat group was also included. Lecithin linearly decreased dry matter intake. In cows fed HPA, lecithin feeding reduced milk fat content and tended to decrease milk fat yield. Although no changes in milk yield were observed, a quadratic reduction in 3.5% fat-corrected milk was observed with increasing lecithin dose. Lecithin linearly increased energy-corrected milk efficiency in cows fed MPA. Lecithin supplementation also decreased milk urea nitrogen, relative to unsupplemented cows. The proportion of 16-carbon FA in milk fat decreased linearly with lecithin dose, whereas 18-carbon FA increased linearly. Lecithin reduced de novo FA (<16-carbon) content and tended to increase preformed FA (>16-carbon) content in a linear manner. Compared with MPA, HPA diets reduced apparent total and 16-carbon FA digestibility and absorption. Deoiled soy lecithin feeding did not modify FA digestibility or absorption. Our observations suggest that soy lecithin feeding modifies rumen digestion to reduce dry matter intake and change milk composition.