Submitted to: Proceedings of International Symposium on the Nutrition of Herbivores
Publication Type: Proceedings
Publication Acceptance Date: 1/26/2000
Publication Date: 1/26/2000
Citation: Interpretive Summary: Grazing management systems can affect both quantity and quality of forage available, which can alter grazing behavior and productivity of cows. Previous research conducted in the subtropics demonstrated that cattle spend less time grazing in spring than summer because forage quality is higher in spring. Furthermore, during summer, heat tolerant cattle were reported to graze longer and during hotter periods of the day than non heat tolerant cattle. The objective of this study was to determine the effect of breed (Angus, Romosinuano, or Senepol) and nutritional demand (with and without creep-grazed calves) on cow grazing behavior and performance. In 1997, Angus (non heat tolerant), Romosinuano (heat tolerant), and Senepol (heat tolerant) cows nursing Romosinuano calves (by natural conception or embryo transfer) were used, and in 1998, Angus and Romosinuano cows nursing their purebred calves were used. Grazing time of the cows was determined using vibracorders for 7 consecutive days in July, August, and September. Creep grazing treatment had no effect on cow grazing time within a 24-hr period. Total grazing time was not affected by breed either year, but in 1997 Angus and Senepol grazed longer than Romosinuano in July and September. For all breeds, most grazing occurred between 0300-0900 and 1500-2100 hr. In general in 1997, grazing time of Senepol >or= Angus >or= Romosinuano. In 1998, grazing time of Angus and Romosinuano was similar except for 1500-2100 hr when Angus > Romosinuano.
Technical Abstract: The objective of this study was to determine the interaction of breed (Angus, Romosinuano, or Senepol) and nutritional demand (with and without creep-grazed calves) on the grazing behavior and performance of lactating Bos taurus beef cattle in the subtropics. In mid June 1997, Angus (n=30), Romosinuano (n=30), and Senepol (n=36), nursing Romosinuano calves (natural conception [n=30] or embryo transfer [n=66]) were stratified into four, treatment (creep grazing vs. no creep grazing)/ replicate groups. Grazing time of the cows was determined using vibracorders for 7 d consecutively in July, August, and September. In 1998, the study was repeated using only Angus (n=41) and Romosinuano (n=37) cows and their purebred, natural service calves. Creep grazing treatment had no effect (P>.05) on total or relative distribution (0300-0900, 0900- 1500, 1500-2100, or 2100-0300 hr) of cow grazing time within a 24-hr period. Total grazing time was not affected by breed either year, but in 1997 there was a treatment x breed x trial interaction (P<.01) for total grazing time with Angus, Senepol > Romosinuano in July and September. Within a 24-hr period, grazing behavior was bimodal for all breeds with more grazing occurring between 0300-0900 and 1500-2100 hr. But in general in 1997 during a 24-hr period, the grazing time of Senepol > or = Angus > or = Romosinuano. In 1998, grazing time of Angus and Romosinuano was similar except for 1500-2100 hr when Angus > Romosinuano.