The effect of iucerne hay quaiiiy on feedlot lambs

Lucerne hay is one of the most widely used roughage sources for ruminant diets, largely due to its reputation for providing high-quality nutrition. Important considerations for producers who use lucerne hay in their feed programme include assessing the true value of lucerne hay, determining the most suitable grade for specific feeding purposes, considering its cost, and balancing these factors against optimal feedlot performance.

- By Carina le Roux

In South Africa, lucerne hay is graded by the National Lucerne Trust (NLT) based on levels of acid detergent fibre (ADF), ash, and lignin. A new lucerne quality index (NLQI) value is calculated using near-infrared (NIR) spectroscopy, which subsequently determines the grade of the hay (Table 1).

The presence of foreign material, or substances not typically found in lucerne, also affect the final grading. While supreme lucerne has the highest NLQI value and represents the best overall quality, it is not always the most suitable option for feedlot use. Similarly, prime lucerne cannot automatically be considered the best choice, as its suitability depends on the intended use of the hay.

Lucerne as a protein source

Lucerne is widely recognised as a protein-rich roughage source. Its quality is typically assessed based on ADF, ash, and lignin content – proteins are not included when determining the NLQI value. In other words, the digestibility of the plant is key to defining its quality.

Higher ADF and lignin levels are associated with lower digestibility, which in turn reduces the availability of nutrients, including proteins. Interestingly, it is possible for grade 3 lucerne hay to contain more protein than grade 1 or even prime lucerne. This raises an important consideration: the intended use of the lucerne hay. Is it intended primarily as a roughage source, where its higher protein content offers a relative benefit, or is it being evaluated specifically as a protein supplement?