Grazing behavior and intake of goats rotationally grazing Tanzania-grass pasture with different post-grazing residues

Abstract

This study aimed to evaluate intake and ingestive behavior of goats rotationally grazing Tanzania (Panicum maximum cv. Tanzânia 1) pastures with 2 levels of post-grazing residue. The experimental area consisted of 1.2 ha of Tanzania pasture divided into 12 paddocks (24 areas), managed under 2 post-grazing residues: low green (leaf + stem) herbage mass (GHM) post-grazing (LR, approximately 1,500 kg/ha GHM); and high GHM post-grazing (HR, approximately 3,000 kg/ha GHM). Each paddock was grazed for 3 consecutive days (D1, D2, D3) followed by 33 days rest and evaluated from October 2005 to April 2006. Animal behavior (grazing time, bite rate and bite size/weight) was evaluated on each grazing day. While goats spent more time grazing on LR than HR (P=0.02), bite rate did not differ between treatments or among days (P=0.31) and averaged 26.5 bites/min. In contrast, bite weight was greater in HR (0.15 g/bite) than in LR (0.12 g/bite), and decreased from D1 to D3 (P<0.001). Absolute dry matter intake of goats was greater in the HR (2.19 kg/d) than the LR (1.89 kg/d) treatment; however, differences were not significant (P>0.05) when intake was determined on a body weight or metabolic weight basis. Our findings are consistent with the general assumption that bite weight is a trade-off between quantity and quality of the herbage mass and is the main determinant of animal performance. More studies are needed to determine animal performance on the various treatments and to determine management strategies to provide a desirable balance between animal weight gain and pasture stability.Keywords: Animal behavior, foraging, grazing systems, Megathyrsus maximus, plant - animal relations.DOI: 10.17138/TGFT(4)91-100