Effect of weaning age and pace on blood metabolites, cortisol concentration, and the mRNA abundance of inflammation-related genes in gastrointestinal, adipose, and liver tissue of Holstein dairy calves

The objective of this study was to evaluate the effects of weaning age and pace on blood metabolites, cortisol concentration, and mRNA abundance of inflammation-related genes in Holstein dairy calves. Seventy-one day-old calves [38.8 ± 4.4 kg, body weight (BW) ± sd] blocked by gender and birth BW, were randomly assigned to a 2 × 2 factorial arrangement of treatments. The first factor was weaning age [6 weeks (early) vs. Eight weeks (late)], the second factor was weaning pace [abrupt (4 step-down over 3 d, the initial milk replacer was 7.6 L, which was reduced 1.9 L in each step-down) vs. gradual (7 step-down over 14 d, the initial milk replacer was 7.6 L, which was reduced 1.09 L in each step-down)], generating early-abrupt (EA), early-gradual (EG), late-abrupt (LA), and late-gradual (LG) treatments. All treatments had 10 female and 8 male calves, except EA that had 1 fewer male calf. Milk replacer (MR; 24% CP, 17% fat) was bottle-fed, up to 1,200 g/d, twice daily (0600h and 1800h). EA and EG calves received 46.2 kg MR while LA and LG calves received a total of 63 kg MR. The study had 2 cohorts (2020, n = 40; 2021, n = 31), and each cohort included all treatments. Blood was collected from the jugular vein at 0900h on d 3 and d 7 of age, a day before starting and a day after weaning completion; male calves were humanely killed a day post-weaning. Rumen, jejunum, large intestine, liver, omental adipose and perirenal adipose tissues were sampled to determine the mRNA abundance of inflammation-related genes. Weaning pace, age, and pace × age, birth BW, and sex were included as fixed and cohort was included as random effects in the model. Blood metabolites and cortisol were analyzed as repeated measure, and sampling day, pace × sampling day, and age × sampling day were also included as additional fixed effects. Significance were noted at P ≤ 0.05 and tendencies when 0.05

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Key Words

• inflammation
• inflammatory markers
• pre-ruminant calves
• weaning strategies

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Affiliation(s)

B C Agustinho Department of Animal, Veterinary & Food Sciences, University of Idaho, Moscow, ID 83844
A Wolfe Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, AB Canada T6G 2P5
C Y Tsai Department of Animal, Veterinary & Food Sciences, University of Idaho, Moscow, ID 83844
L M Pereira Department of Animal, Veterinary & Food Sciences, University of Idaho, Moscow, ID 83844
D E Konetchy Department of Animal, Veterinary & Food Sciences, University of Idaho, Moscow, ID 83844
A H Laarman Department of Animal, Veterinary & Food Sciences, University of Idaho, Moscow, ID 83844; Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, AB Canada T6G 2P5
P Rezamand Department of Animal, Veterinary & Food Sciences, University of Idaho, Moscow, ID 83844.

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