Effect of age and dietary plane of nutrition on transcript profiles of ruminal tissue of Holstein bull calves

Calf;milk replacer;crude protein;ruminal epithelium

Naeem, Aisha

关键词: Calf;    milk replacer;    crude protein;    ruminal epithelium;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/29586/Naeem_Aisha.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Transition around weaning in calves is as important as the transition around calving and largely depends on the metabolic and functional development of rumen. Higher protein intake during the early life period can induce changes at the transcriptional level to promote the early development of the rumen. This may benefit physical and metabolic rumen development. This study assessed the effects of enhanced early dietary plane of nutrition (ENH) and age on the gene expression pattern of ruminal epithelial tissue of neonatal Holstein calves. Male Holstein calves were fed (3 to 42 d age) reconstituted control milk replacer (MR) (20% CP, 20% fat; 1.25 lb solids/calf) plus conventional starter (19.6% CP, DM basis) or a high-protein MR (ENH; 28.5% CP, 15% fat; at ca. 2% of body weight) plus high-CP starter (25.5% CP, DM basis). Groups of calves in control and ENH were harvested after 43 d (wk 5) and 71 d (wk 10) of feeding. The ruminal epithelium from 5 calves in each group was used for transcript profiling using quantitative PCR and bovine oligonucleotide microarray. Reticulo-rumen mass post-weaning was greater (P<0.01) in calves consuming ENH diet. Transcriptome analysis revealed that 208 genes were modulated due to treatment and 587 due to time alone. Two-way comparisons were made to further computational analysis of the data; within diet (5 wk, ENH vs. CON; 10 wk, ENH vs. CON) and within time (ENH; 10 wk vs. 5 wk, CON; 10 wk vs. 5 wk). Due to an interaction at wk 5, 68 differentially expressed genes (DEGs) were observed and 53 at wk 10 (FDR P value <0.20; P value <0.15). An induction of most metabolic pathways and signaling pathways was seen in the week comparison in ENH (ENH; 10 vs. 5) but not in control (CON; 10 vs. 5). For the time effect, except for metabolism, all the signaling and genetic information pathways were inhibited at wk 10 as compared to wk 5. The identified genes were mainly associated with cellular growth and proliferation, cell death, cellular morphology and tissue development. The differential expression of selected genes was verified by real time (RT) qPCR. The expression of genes involved in cell proliferation (INSR, FOXO1, AKT3) was greater for ENH primarily at the end of the milk-fed period. The qPCR analysis revealed a marked up-regulation of the ketogenic genes HMGCS2, HMGCL, and BDH1 and urea transporter (SLC14A1) corresponding to an increased plasma β-hydroxybutyrate (BHBA) concentration and blood urea-N (BUN) by wk 10 regardless of treatment. The expression of the urea transporter (SLC14A1) increased markedly with age and was correlated with the increase in blood urea-N (BUN). These findings open new perspectives for further studies on diet-dependent alterations in neonatal calf ruminal epithelium.