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Publication Date

1981

Description

The amount of forage eaten by farm animals when forage is offered ad libitum is a major factor in the nutritive value of forage grasses. It is influenced by a number of internal and external factors. Experimental results of studies on the subject :reported in the literature are often contradictory, partially because, perhaps, of the methods of evaluation employed. We studied whether and to what extent different experimental procedures influenced the results of intake experiments in grass cultivars. Four cultivars of Lolium perenne differing in ploidy level and precocity were fed to sheep ad libitum, and voluntary intake was assessed using four different procedures: (1) fresh vs. dried forage; (2) grazing vs. barn feeding; (3) free choice vs. no choice be­tween cultivars; and (4) feeding at different stages of growth vs. feeding at same stage of growth. Highly significant differences between cultivars were found when cultivars were offered fresh for free choice on pasture and in the barn on the same dates. Late cultivars were preferred to early ones, and tetraploids were preferred to diploids. :Essentially the same results were obtained when hay of the flowering stage was offered free choice. When hay of the cultivars was fed as single feeds, differences between cultivars varied with stages of growth. They were larger at earlier than at later stages, and sometimes interactions occurred. Hay intake decreased significantly with advancing stages of growth. Differences in stage of growth in all cultivars at harvesting of the feeds had a much larger effect than differences in cultivars. With respect to voluntary intake, genetic differences among grass cultivars suggest the possibility of genetic improvement. The procedures for assessment of intake should he chosen according to the intended use of the forage.

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Effect of Experimental Methods on Results of Voluntary Intake Experiments with Grass Cultivars

The amount of forage eaten by farm animals when forage is offered ad libitum is a major factor in the nutritive value of forage grasses. It is influenced by a number of internal and external factors. Experimental results of studies on the subject :reported in the literature are often contradictory, partially because, perhaps, of the methods of evaluation employed. We studied whether and to what extent different experimental procedures influenced the results of intake experiments in grass cultivars. Four cultivars of Lolium perenne differing in ploidy level and precocity were fed to sheep ad libitum, and voluntary intake was assessed using four different procedures: (1) fresh vs. dried forage; (2) grazing vs. barn feeding; (3) free choice vs. no choice be­tween cultivars; and (4) feeding at different stages of growth vs. feeding at same stage of growth. Highly significant differences between cultivars were found when cultivars were offered fresh for free choice on pasture and in the barn on the same dates. Late cultivars were preferred to early ones, and tetraploids were preferred to diploids. :Essentially the same results were obtained when hay of the flowering stage was offered free choice. When hay of the cultivars was fed as single feeds, differences between cultivars varied with stages of growth. They were larger at earlier than at later stages, and sometimes interactions occurred. Hay intake decreased significantly with advancing stages of growth. Differences in stage of growth in all cultivars at harvesting of the feeds had a much larger effect than differences in cultivars. With respect to voluntary intake, genetic differences among grass cultivars suggest the possibility of genetic improvement. The procedures for assessment of intake should he chosen according to the intended use of the forage.