GC Analysis of Fatty Acid Profiles in Goat Milk: Impact of Grazing vs. Housed Systems

Mexican researchers set out to compare milk yield, chemical makeup, and the fatty acid (FA) profile of early-lactation native goats managed under grazing and housed systems, using infrared (IR) spectrophotometry and gas chromatography (GC) for analysis of fat, protein, lactose, and FA. A paper based on their work was published in Veterinary World.¹

In Mexico’s Comarca Lagunera, considered the country’s primary goat-milk basin, local herds produced over 58 million liters of milk in 2023, which accounts for one-third of the country’s output.^2,3 Itis estimated that approximately 70% of these goats graze native rangeland during the day and are penned at night, while the remaining 30% are kept in continuous confinement and fed concentrate-based diets.⁴

As a result, the production system influences nutrient supply, which ultimately affects both the mount of milk produced and its composition.The health significance of this data is significant. A meta-analysis of human trials showed that a daily intake of 3 g cis-9, trans-11 conjugated linoleic acid (CLA) lowered fasting blood sugar by 4% and decreased tumor-proliferation markers by 7%.⁵ Goat milk can provide up to 60 mg of CLA per 100 mL when grazing is the primary feed source, nearly double the level found in stall-fed goats.⁶

“Despite the significance of native goats in arid and semi-arid regions,” write the authors of the paper,¹ “there is limited knowledge of how different production systems affect their milk traits. Most existing research on milk yield, chemical makeup, and FA profiles has come from high-producing exotic breeds kept under intensive indoor management, leaving a major gap in understanding for locally adapted animals.”

For this study, ten clinically healthy native goats in early lactation were randomly assigned to two treatments: grazing (n = 5) and housed (n = 5). The housed goats received a mixed ration, while the grazing goats foraged daily on native rangeland. Milk yield was recorded weekly; 100 mL composite milk samples were analyzed for fat, protein, lactose, and fatty acid (FA) profile using IR spectrophotometry and GC. The experimental period included 14 days of adaptation and 42 days of data collection.¹

The data indicated that the housed goats showed significantly higher (p < 0.05) daily milk yield (1.41 vs. 0.81 kg per day) and fat-corrected milk (1.22 vs. 0.83 kg per day). Protein and lactose concentrations were also greater in housed goats. The grazing goats more favorable FA profile, including increased unsaturated FAs such as oleic acid (C18:1 c9), α-linolenic acid (C18:3 n-3), and cis-9, trans-11 CLA (p = 0.0009). In addition, the ability for the goat to graze resulted in milk with decreased medium-chain saturated FAs and increased long-chain FAs and total monounsaturated FAs.¹

“Grazing boosts the nutritional quality of milk from native goats by increasing unsaturated FAs and significantly raising CLA levels,” write the authors of the study,¹ “though it comes with a reduction in milk volume. These results underscore the importance of native goats and extensive grazing systems for producing nutrient-rich milk in arid areas, supporting both sustainability and potential markets for functional foods.”

The team believes that future research should include larger herds, multi-seasonal sampling, and mid- to late-lactation stages to better understand temporal patterns. Mechanistic studies linking forage composition, ruminal biohydrogenation pathways, and milk FA deposition, in their opinion, would further improve understanding of how diet influences milk nutritional quality. Furthermore, the evaluation of partial supplementation strategies, drought-resilient feeding systems, and economic feasibility models will also be critical to support climate-adaptive and resource-efficient production under semi-arid conditions.¹

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References

1. Trejo-López, M. T.; Hernández-Mendo, O.; Granados-Rivera, L. D. et al. Grazing Versus Housing in Native Dairy Goats: Impacts on Milk Yield, Composition, and Conjugated Linoleic Acid Enrichment Under Arid Conditions. Vet World 2025, 18 (12), 4093-4104. DOI: 10.14202/vetworld.2025.4093-4104
2. Torres-Hernández, G.; Maldonado-Jáquez, J. A.; Granados-Rivera, L. D. et al. Creole goats in Latin America and the Caribbean: A priceless resource to ensure the well-being of rural communities. Int. J. Agric. Sustain. 2022, 20, 368–380. DOI: 10.1080/14735903.2021.1933361
3. Servicio de Información Agroalimentaria y Pesquera (SIAP). Avance Mensual de La Producción Pecuaria. Servicio de Información Agroalimentaria y Pesquera, México, 2023. https:// nube.siap.gob.mx/avance_pecuario/ (accessed 22-12-2025)
4. Tajonar, K.; López Díaz, C. A.; Sánchez Ibarra, L. E. et al. A Brief Update on the Challenges and Prospects for Goat Production in Mexico. Animals 2022, 12 (7), 837. DOI: 10.3390/ani12070837
5. Tudisco, R.; Grossi, M.; Addi, L. et al. Fatty Acid Profile and CLA Content of Goat Milk: Influence of Feeding System. J. Food Res. 2014, 3 (4), 93. DOI: 10.1111/jpn.12344
6. Bodnár, Á.; Egerszegi, I.; Kuchtik, J. et al. Effect of Grazing on Composition, Fatty Acid Profile and Nutritional Indices of Goat Milk and Cheese. J. Anim. Feed Sci. 2021, 30 (4), 320–328. DOI: 10.22358/jafs/144843/2021