The First Colostrum is Not Simply an Antibody Bolus, It is the First Complete Nutritional Intervention of Life 

Birth is an abrupt change in both temperature and nutrition. A newborn ruminant goes from the stable warmth of the uterus into surroundings that may be roughly 10 to 15°C colder than its core body temperature. It starts losing heat right away. At the same time, the calf, lamb or kid has to stand, suckle, keep its blood sugar up and produce its own heat, all with very limited energy reserves.

Newborns make heat in two ways: shivering (rapid involuntary muscle contractions that produce heat), and non-shivering thermogenesis (heat production without shivering). Brown adipose tissue (BAT), or brown fat, is the main source of non-shivering heat in newborn ruminants. Brown fat cells are packed with mitochondria and contain a protein called UCP1, which lets them burn fuel to release heat directly. Fatty acids are a key fuel for this process, and the newborn's first feedings supply more fatty acids, along with glucose and other nutrients, to keep that metabolism going.

From Birth to Staying Warm 

Colostrum Fat is More Than a Side Note

While colostrum quality is usually evaluated by IgG concentration, it is so much more than just an antibody bolus. Colostrum is a nutrient-dense first feed, providing protein, fat, lactose (milk sugar), vitamins, minerals and bioactive components that have naturally evolved to support early life health, development and survival.

Fat specifically matters for three reasons:

1. The most energy-dense nutrient in colostrum
2. Provides a high concentration of fat soluble vitamins
3. Supplies fatty acids the newborn uses directly in its own fat metabolism.

The strongest direct evidence comes from a 2026 study by Erkinger et al. Twelve calves were fed colostrum from the same pool, either at its natural 4.81% fat or with the fat experimentally reduced to 0.58%. Energy intake during the colostrum phase was 24.5 MJ/day for the full-fat group versus 15.5 MJ/day for the low-fat group.

The differences showed up in the blood:

• Full-fat calves had higher blood glucose (sugar) over the first four days, plus higher triglycerides and several cholesterol fractions.
• Low-fat calves had higher cortisol and glucagon, hormones that typically rise when the body is stressed or needs to draw on its own energy stores.
• Serum IgG was the same in both groups.

In other words, calves can reach the same level of passive immunity from colostrum while receiving very different levels of metabolic support. The study was small, but it is the clearest evidence so far that these two jobs of colostrum feeding can be separated.

Natural variation points the same way. In a 2026 study of 46 Holstein calves fed their own dams' colostrum, von Riedheim et al. found that calves receiving higher-fat colostrum had higher blood phospholipids, triglycerides and cholesterol during the first 24 hours. The link with phospholipids was strong, with a correlation of r = 0.76 at 24 hours.

Why this matters in lambs and goat kids

Lambs and kids are especially vulnerable to heat loss because they have a lot of skin surface relative to their small body size. Brown fat is an important source of heat for them, and their ability to keep producing heat is closely tied to early nutrient supply. Classic 1998 research in newborn lambs by Clarke and Symonds showed that a feeding of just 50 mL of colostrum increased brown fat heat-producing activity. This supports a link between early feeding and heat production, although it does not prove that colostrum fat alone switches brown fat on.

The Whole of Colostrum Matters, Not Just IgG Content

The fundamentals of Day-One management have not changed: adequate IgG concentration, enough total IgG mass, fast feeding, the right volume, clean colostrum and successful passive transfer. The new evidence does not suggest replacing IgG measures with fat measures, but establishes the value fat from colostrum provides newborn ruminants to support early life growth, development and thermogenesis.

What it does is add a question worth asking. A Brix % or IgG evaluation tells you the immune potential of the meal, but not its full nutritional or energy value. That difference may matter most when maternal colostrum falls short and a replacer or supplement strategy is needed.

Practical implications

• Protect the fundamentals. Getting enough IgG into the newborn quickly is still the first priority.
• Think about the whole meal. Volume, total solids, protein, fat, energy, cleanliness and feeding temperature all shape what the newborn actually receives.
• Watch for cold risk. Calves, lambs and kids born in cold, wet or windy conditions need more energy to stay warm.
• Don't overstate the role of fat. Research shows colostrum fat affects newborn metabolism, but it has not identified an ideal fat level or shown that more fat is always better.
• Whole Colostrum Replacers Are Essential. Having a colostrum replacer on hand that is whole colostrum in order to provide the bioactives and specific fats required by lambs and kids is necessary to ensure even in emergencies calves receive quality colostrum.
• More research is needed in small ruminants. Studies that isolate the effect of colostrum fat in lambs and goat kids are still limited.

Conclusion

The first hours of life are among the most metabolically demanding a ruminant will ever face. The placenta has stopped supplying nutrients, the temperature around the newborn has dropped suddenly, and it must absorb antibodies for passive immunity while it’s body begins to develop and tries to keep itself warm.

References:

1. Erkinger,H.,von Riedheim, M.A.E., Calisici, O., and Gross, J.J. 2026. Colostral fat content modulates glucose homeostasis and lipid metabolism in neonatal calves exposed to cold temperatures. Journal of Dairy Science. 109:7618-7630. doi:10.3168/jds.2025-28151.

2. von Riedheim, M.A.E. et al. 2026. Associations of individual nutrient and non-nutrient factors on endocrine and metabolic parameters in neonatal calves fed colostrum from their own dams. Journal of Dairy Science. 109(3):3048-3062. doi:10.3168/jds.2025-27341.

3. Silva, F.L.M. et al. 2021. Thermoregulatory responses and performance of dairy calves fed different amounts of colostrum. Animals. 11(3):703. doi:10.3390/ani11030703.

4. Mota-Rojas, D. et al. 2022. Neonatal infrared thermography images in the hypothermic ruminant model: Anatomical-morphological-physiological aspects and mechanisms for thermoregulation. Frontiers in Veterinary Science. 9:963205. doi:10.3389/fvets.2022.963205.

5. Xiao, Z.H., Duan, H.W., and Li, L. 2026. Brown adipose tissue in ruminants: development, thermogenic function, and nutritional regulation. Frontiers in Veterinary Science. 13:1819034. doi:10.3389/fvets.2026.1819034.

6. Clarke, L., and Symonds, M.E. 1998. Thermoregulation in newborn lambs: influence of feeding and ambient temperature on brown adipose tissue. Experimental Physiology. 83. doi:10.1113/expphysiol.1998.sp004146.

7. Silva, A.P., Cezar, A.M., de Toledo, A.F., Coelho, M.G., Tomaluski, C.R., Virgínio Júnior, G.F., and Bittar, C.M.M. 2024. Enrichment of medium-quality colostrum by adding colostrum replacer, combined or not with transition milk in the feeding of dairy calves. Scientific Reports. 14:5533. doi:10.1038/s41598-024-55757-4.

8. Lopez, A.J., Echeverry-Munera, J., McCarthy, H., Welboren, A.C., Pineda, A., Nagorske, M., Renaud, D.L., and Steele, M.A. 2023. Effects of enriching IgG concentration in low- and medium-quality colostrum with colostrum replacer on IgG absorption in newborn Holstein calves. Journal of Dairy Science. 106:3680-3691. doi:10.3168/jds.2022-22518.

9. Eekhoff, M.K., Hansen, S.L., and Drewnoski, M.E. 2026 Invited Review: Vitamin A in beef cow-calf systems-Biological relevance, revisiting of requirements, and unresolved questions. Applied Animal Science. 42:263-283. doi:10.15232/aas.2025-02772.

10. Lombard, J. et al. 2020. Consensus recommendations on calf- and herd-level passive immunity in dairy calves in the United States. Journal of Dairy Science. 103:7611-7624. doi:10.3168/jds.2019-17955.