Grazing versus housing in native dairy goats: Impacts on milk yield, composition, and conjugated linoleic acid enrichment under arid conditions.

Background and Aim: Milk yield and composition in goats are heavily influenced by feeding and management practices, especially in arid areas where forage availability varies. Native goats in northern Mexico are well adapted to tough environments, yet there is limited evidence on how different production systems impact their milk quality. This study aimed to compare milk yield, chemical makeup, and the fatty acid (FA) profile, particularly conjugated linoleic acid (CLA), of early-lactation native goats managed under grazing and housed systems. Materials and Methods: Ten clinically healthy native goats in early-lactation were randomly assigned to two treatments: grazing (n = 5) and housed (n = 5). Housed goats received a mixed ration, while grazing goats foraged daily on native rangeland. Milk yield was recorded weekly, and 100 mL composite milk samples were analyzed for fat, protein, lactose, and FA profile using infrared spectrophotometry and gas chromatography. The experimental period included 14 days of adaptation and 42 days of data collection. Data were analyzed using a completely randomized design with repeated-measures in PROC MIXED (SAS v9.4), and Tukey's test was applied for comparisons (p < 0.05). Results: 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. In contrast, grazing goats produced milk with higher fat concentration (+42.3%; p = 0.0238) and a 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). Grazing also decreased medium-chain saturated FAs while increasing long-chain FAs and total monounsaturated FAs. Conclusion: Grazing boosts the nutritional quality of milk from native goats by increasing unsaturated FAs and significantly raising CLA levels, 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.