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.

我们假设在墨西哥北部旱地灌木丛上混合品种山羊的饮食选择取决于它们的产奶潜力。在冬季和春季（干旱季节），记录牛奶产量并每周收集草料样品。将山羊分为中等（MP； n = 20）或低产奶量组（LP； n = 20）。MP和LP山羊泌乳105 d的总产奶量分别为45.2±12.5和20.7±5.2L。大坝体重与产奶量呈正相关（P <0.001）。显微组织学分析表明，在干燥季节，山羊日粮主要由灌木（33％）和多年生草（36％）组成，而产奶量或季节对日粮选择没有影响。具有丰富的次生化合物的植物，例如Larrea tridentate和Prosopis laevigata冬季约占山羊饮食的7％。山羊表现出对选择性强格兰马草和巴豆lechleri在两个季节。MP山羊选择的牧草能量含量高于LP山羊（P <0.01）。春季山羊采食的CP含量高于冬季（8.1％）（12.7％； P <0.01）。我们得出的结论是，在两个季节中，产奶量较高的混种山羊选择相似的日粮作为产奶量较低的山羊。这些在墨西哥北部旱生灌木丛上饲养的混种山羊有潜力在冬季和春季（旱季）生产中等水平的牛奶；但是，在草料短缺的情况下，必须补充浓缩物以维持牛奶产量。