Nematode parasites make a big difference in the appetite of beef cattle and thus their weight gain. Left to right are four of the paddocks used in nematode research at the LSU AgCenter’s Dean Lee Research Station near Alexandria. The road about a third of the way from the top serves as one border, and the tree line at the bottom is another border. Each of the paddocks is about 4 acres and contains five calves. The differences in appearance are due to forage height and availability because of the decreased appetite of parasitized control animals. The paddocks that contain animals that have been treated for nematode parasites are lighter in color, indicating less available forage. At relatively high stocking rates, treated animals may graze their paddocks closely enough that they do not have sufficient forage for optimum weight gain. Animals not treated, on the other hand, may have significantly more available forage and even though they desire less forage, they have all they want and can reach their performance potential. This can mask some of the differences between the treated and nontreated animals. Nematode infections as well as factors such as forage palatability and toxicity can also bias forage evaluation studies by affecting forage availability and nutritive value. Replicates of different stocking rates may be necessary to accurately evaluate differences.
Alvin Loyacano, Professor, Dean Lee Research Station, Alexandria, La.