Long-term growth, feed efficiency, enteric methane emission, and blood metabolite responses to in utero hyperthermia in Holstein heifers

Authors: RIESGRAF, KAYLEE - University Of Wisconsin; Akins, Matthew; LAPORTA, JIMENA - University Of Wisconsin; WEIGEL, KENT - University Of Wisconsin

Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/7/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary: Late gestation heat stress in dairy cattle induces severe negative consequences on the neonatal calf that hinder lifelong performance. We analyzed the growth trajectory, feed efficiency, methane emissions, and blood serum metabolomics of 18-month-old heifers that were exposed to either heat stressed or thermoneutral in utero environments. Overall, in utero heat stressed heifers were shorter in body length and similar to their in utero cooled counterparts in body weight, feed efficiency, and methane emissions. Differential blood metabolites were primarily involved in lipogenic pathways. This data may further our understanding of cellular disfunctions caused by in utero heat stress that might compromise heifer’s growth, and liver and mammary gland development and function.

Technical Abstract: Dairy producers are beginning to experience production and animal welfare pressures from increasing frequency and severity of heat stress events due to global climate change. Offspring performance during the pre-weaning and lactating periods is compromised when exposed to heat stress during late gestation (in utero). However, knowledge of the lingering impacts of in utero heat stress on the yearling dairy heifer is limited. Herein, we investigated the long-term effects of in utero heat stress on heifer growth, feed efficiency, and enteric methane emissions in post-pubertal heifers. During the last 56 d of gestation, 38 pregnant cows carrying heifer calves were exposed to either heat stress (IUHT; n = 17) or artificial cooling (IUCL; n = 21). At 18 ± 1 months of age, the resulting IUCL and IUHT heifers were enrolled in the present 63-day study. Heifers were blocked by weight and randomly assigned to three pens with Calan gates. Body weights (BW) were recorded on three consecutive days at the start and end of the trial and used to calculate average daily gain (ADG). Body condition score (BCS), hip width, body length, and chest girth were measured once at the start and end of the study. All heifers were fed a TMR comprised of 46.6% oatlage, 44.6% grass/alfalfa haylage, 7.7% male-sterile corn silage, 0.3% urea, and 0.8% mineral/vitamin supplement (DM basis). The TMR and refusal samples were obtained daily, composited weekly, and dried to calculate DMI. During the study, each pen had access to a GreenFeed unit (C-Lock, Rapid City, SD) for 8 ± 1d to measure CH4 and CO2 gas fluxes. During the last three days of measuring CH4 and CO2 fluxes, fecal samples were collected, composited by animal, dried, and analyzed to calculate NDF, OM, and DM digestibility. On the last day of fecal sampling, blood samples were also collected via coccygeal venipuncture, and gas chromatography time-of-flight mass spectrometry analysis was performed Residual feed intake (RFI; predicted DMI - observed DMI) and feed conversion efficiency (FCE; DMI/ADG) were calculated to estimate feed efficiency. No differences were found in initial or final BW, hip width, chest girth, or BCS; however, IUCL heifers were longer in body length compared with IUHT heifers. Dry matter intake, ADG, RFI, and FCE were similar between IUHT and IUCL heifers. In utero heat stressed and IUCL heifers produced similar amounts of methane and carbon dioxide, and no differences were found in the number of GreenFeed visits or latency to approach the GreenFeed. The concentrations of six blood metabolites involved in lipogenic pathways were different between in utero treatments. In conclusion, in utero heat stress does not seem to have long-term effects on feed efficiency or methane emissions during the post-pubertal growing phase; however, IUCL heifers maintained a body length advantage over their IUHT counterparts and differed in concentrations of several candidate metabolites that encourage further exploration in the liver and mammary gland.