Colostral fat content modulates glucose homeostasis and lipid metabolism in neonatal calves exposed to cold temperatures

Thermoregulation in neonatal calves is essential to maintain body temperature. Especially during the cold season, a successful metabolic adaptation is required to avoid health and production losses. Colostrum and transition milk are characterized by an elevated fat content compared with mature milk. Although colostral fat content is known to vary considerably among cows, its specific effect on postnatal metabolic adaptation in calves under cold conditions has not been well characterized. The objective of the present study was to investigate the impact of a different fat content in colostrum and transition milk on metabolic adaptation in newborn calves during the cold season. Twelve calves (n = 9 Holstein, n = 3 Holstein × Limousin crossbred; birth weight 41.3 ± 1.8 kg) born to cows without dystocia were enrolled immediately after birth and studied until d 21 postpartum (p.p.). The experimental period lasted from February to March 2025. Based on sex, birth weight, and breed, calves were assigned to either a group receiving 2.5 L full-fat colostrum (FF; n = 6; 4.81% fat) or low-fat colostrum (LF; n = 6; 0.58% fat) at 4 and 12 h p.p. Both FF and LF derived from the same pool of colostrum and differed only in fat content. On d 2 and 3 p.p., FF and LF received transition milk (300 mL colostrum of different fat content mixed with 2.7 L bulk tank milk). From d 4 onwards, all calves were fed identically with bulk tank milk. Blood was sampled from d 2 to 7 and analyzed for various endocrine and metabolic parameters (e.g., glucose [GLU], insulin, cortisol, glucagon, nonesterified fatty acids [NEFA], triglycerides [TG], total cholesterol [TC], high-density lipoprotein cholesterol [HDL-C]), low-density lipoprotein cholesterol [LDL-C], very low-density lipoprotein cholesterol [VLDL-C], aspartate aminotransferase [ASAT], gamma-glutamyl transferase [GGT], triiodothyronine, thyroxine, total protein [TP], and IgG). Plasma GLU concentration increased during the first days after parturition in both LF and FF, with greater concentrations in FF during the first 4 d p.p. Serum concentrations of TG, TC, HDL-C, and VLDL-C were greater in FF until d 4 p.p., and TC and LDL-C were greater in FF compared with LF from d 5 to 21. No differences were observed for serum IgG, insulin, NEFA, and TP. Cortisol and glucagon concentrations as well as activity of GGT were elevated in LF compared with FF until d 4 of age. In conclusion, the present study showed that the fat content of colostrum and transition milk affected metabolic adaptation in neonatal calves during the first days of life. The overall lower energy availability in LF was reflected by changes of parameters related to glucose and lipid metabolism. Further studies investigating the impact of colostral fat content under different environmental conditions are warranted.