Diet Selected by Goats on Xerophytic Shrubland with Different Milk Yield Potential

We hypothesized that diet choice of mixed-breed goats on xerophytic shrubland of northern Mexico depends on their milk yield potential. During winter and spring (dry season), milk yield was recorded and forage samples were collected weekly. Goats were separated into a medium (MP; n = 20) or low-milk yielding groups (LP; n = 20). Total milk yield for 105 d lactation was 45.2 +/- 12.5 and 20.7 +/- 5.2 L for MP and LP goats, respectively. Dam bodyweight was positively related to milk yield (P < 0.001). Microhistological analyses showed that goat diets were composed mainly of shrubs (33%) and perennial grasses (36%) during the dry season with no influence of milk-yield or season on diet selection. Plants with abundant secondary compounds such as Larrea tridentate and Prosopis laevigata constituted around 7% of the goat diets in winter. Goats showed strong selectivity for Bouteloua gracilis and Croton lechleri in both seasons. The energy content of forage selected by MP goats was higher (P < 0.01) than that of LP goats. CP content of forages selected by goats was higher (12.7%; P < 0.01) in spring than in winter (8.1%). We concluded that mixed-breed goats with higher milk yield capacity selected similar diets as goats with less milk production capacity during both seasons. These mixed-breed goats reared on xerophytic shrubland of northern Mexico have the potential for producing moderate levels of milk during winter and spring (dry season); however, concentrate supplementation is necessary to sustain milk production under condition of forage scarcity.