Abstract
This study was conducted to evaluate the use of chromium oxide and the content of fecal nitrogen to estimate forage intake by female lambs on Italian ryegrass pasture. The pasture was managed under different forage allowances (FA): 6, 9 and 12% BW. The experiment was a randomized split-split plot design, in which the forage allowances were considered as main plots, the phenological stages as subplots and methods to determine intake as sub-subplots. Forage intake, in the ryegrass vegetative stage, is independent of forage allowance. Lower allowances limit forage intake from the pre-flowering stage, while at the reproductive stage, intake was lower in FA6, intermediate in FA9 and higher in FA12. The estimation of organic matter intake by lambs on Italian ryegrass is similar when chromium oxide and fecal nitrogen are used as markers. The forage intake according to forage allowances depends on the sward structure and is limited by high stem mass at the end of the phenological cycle.
Highlights
Forage intake is an important factor determining the performance of grazing herbivores through the ingestion of nutrients required for maintenance and production of these animals (Maggioni et al, 2009)
Fecal excretion has been more often estimated with the use of external indicators and, among them, the most widely used by the Brazilian scientific community is chromium oxide (Cr2O3), despite their known deficiencies (Carvalho et al, 2007; Zeoula et al, 2002)
There was no interaction between forage allowances × phenological stages (p > 0.10) for the allowance of leaf blades (LBA), but there was a difference for this variable between the evaluated allowances (p = 0.0195) and between the phenological stages of ryegrass (p < 0.0001)
Summary
Forage intake is an important factor determining the performance of grazing herbivores through the ingestion of nutrients required for maintenance and production of these animals (Maggioni et al, 2009). The determination of intake in grazing situations, has some limitations In this condition, the intake cannot be determined directly and various techniques are used to estimate it, such as the use of internal and external markers, esophageal fistulas and assessments of feeding behavior. 365-371, Oct.-Dec., 2015 dosage of an internal or external marker and did not require sampling of forage as grazed by the animals This intake can be estimated directly by an equation already determined. Recent researches evaluated the forage intake of sheep on ryegrass but using the agronomic method (Glienke, Rocha & Confortin, 2008; Roman et al, 2007) and with the double weighing technique (Camargo et al, 2012) These studies did not analyze the relationships with forage allowance nor aimed to determine the better method for the forage intake estimation. This study was conducted in order to compare the use of chromium oxide and fecal nitrogen to estimate forage intake by female sheep on ryegrass pasture under intermittent grazing and managed under different forage allowances: 6, 9 and 12% body weight
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