Which of the following factors is critical for evaluating dairy cattle?

Milk yield and composition are indeed critical factors in evaluating dairy cattle because they directly relate to the economic productivity and efficiency of a dairy operation. The primary purpose of dairy cattle is to produce milk, and understanding both the quantity (milk yield) and quality (milk composition, including butterfat and protein content) helps farmers and breeders make informed decisions about breeding, feeding, and overall management strategies.

In evaluating a dairy cow, high milk yield indicates that the animal is largely fulfilling its role as a dairy producer, while favorable milk composition is essential for meeting market demands and ensuring the profitability of dairy products. Breeders often select animals not just based on their ability to produce large quantities of milk, but also on the nutritional quality of that milk, which can significantly affect the value of the product.

While factors such as coat color, age, and overall size can provide some insights into the dairy animal's potential, they do not directly correlate with the primary purpose of dairy cows, which is to efficiently produce high-quality milk. Therefore, focusing on milk yield and composition is paramount in evaluating the effectiveness and suitability of dairy cattle in a commercial setting.