Abstract #417
Section: Lactation Biology (orals)
Session: Lactation Biology I
Format: Oral
Day/Time: Tuesday 2:45 PM–3:00 PM
Location: Ballroom F
Session: Lactation Biology I
Format: Oral
Day/Time: Tuesday 2:45 PM–3:00 PM
Location: Ballroom F
# 417
Heat stress negatively affects the transcriptome related to overall metabolism and milk synthesis in mammary tissue of mid-lactating dairy cows.
Dengpan Bu*1,3, Lu Ma1,2, Shengtao Gao1, Zhengkui Zhou1, Lance H. Baumgard4, Jiang Duo5, Massimo Bionaz5, 1State Key Laboratory of Animal Nutrition, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing, China, 2CAAS-ICRAF Joint Lab on Agroforestry and Sustainable Animal Husbandry, World Agroforestry Centre, East and Central Asia, Beijing, China, 3Hunan Co-Innovation Center of Safety Animal Production, Changsha, Hunan, China, 4Department of Animal Science, Iowa State University, Ames, IA, 5Animal and Rangeland Sciences, Oregon State University, Corvallis, OR.
Key Words: transcriptome, milk synthesis, heat stress
Heat stress negatively affects the transcriptome related to overall metabolism and milk synthesis in mammary tissue of mid-lactating dairy cows.
Dengpan Bu*1,3, Lu Ma1,2, Shengtao Gao1, Zhengkui Zhou1, Lance H. Baumgard4, Jiang Duo5, Massimo Bionaz5, 1State Key Laboratory of Animal Nutrition, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing, China, 2CAAS-ICRAF Joint Lab on Agroforestry and Sustainable Animal Husbandry, World Agroforestry Centre, East and Central Asia, Beijing, China, 3Hunan Co-Innovation Center of Safety Animal Production, Changsha, Hunan, China, 4Department of Animal Science, Iowa State University, Ames, IA, 5Animal and Rangeland Sciences, Oregon State University, Corvallis, OR.
Study objectives were to examine transcriptome related to casein synthesis in lactating cows under heat stress (HS) by using RNA sequencing. Four multiparous Holstein dairy cows (101 ± 10 DIM; 38 ± 2 kg milk/d) were randomly assigned to 1 of 4 environmental chambers with a crossover design. Following a 9-d adaptation period, cows were either subjected to HS [36°C during the day and 32°C during the night; temperature-humidity index (THI) = 87.2 and 81.8] for 9d or kept in thermal neutral conditions [TN: 20°C; THI = 65.5] for 9 d, but pair-fed (PF) with heat-stressed cows. There was a 30-d washout between periods. Mammary biopsies were obtained at the end of each period. HS decreased milk yield (17%) and protein content (4.1%). HiSeq2000 platform was used to measure the mRNA profile. Alignment to the cattle reference genome (Bos_taurus.UMD3.1) was performed using spliced read mapper Tophat2 and a quasi-negative binomial model was used to analyze the normalized data, which included as covariates the cow effects and the order in which the treatment and control conditions were implemented. The effects of HS on gene expressions were tested using quasi-likelihood F tests. The analysis was performed with the edgeR package in R. There were 1,718 differentially expressed genes (DEG; FDR < 0.01): 870 upregulated and 848 downregulated genes in HS vs. PF. Major casein genes (CSN1S2, CSN1S1, CSN3, and LALBA) and amino acid transporters (SLC38A10, SLC38A3, SLC38A1, SLC30A2, SLC34A2, SLC1A2, SLC38A3, SLC1A4, SLC1A5, SLC38A3, SLC7A5, SLC7A8, SLC1A1, and SLC1A2) were downregulated in HS vs PF. Inhibited casein genes and amino acid transporters likely explains the observed decrease in protein synthesis. Besides decrease in protein synthesis, data analyzed using the Dynamic Impact Approach and Database for Annotation, Visualization and Integrated Discovery revealed a general inhibition of metabolic pathways in HS vs. PF, in particular, most impacted pathways were related to lipid, lactose, and amino acid synthesis. In summary, transcriptome analysis revealed that HS directly (independent of reduced feed intake) markedly altered mammary metabolism.
Key Words: transcriptome, milk synthesis, heat stress
