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Publication Date
1981
Description
An adequate supply of nutrients for grazing animals depends on the intake and nutritive value of herbage. Little information is available on factors affecting herbage intake of grazing cows, particularly for grazing systems that do not involve daily change of animals to a new pasture. Our objectives were to determine the effects of variation in herbage mass ( due to variation in stage of maturity) and of herbage allowance on herbage intake by grazing dairy cows and on efficiency of consumption (herbage consumed as a proportion of herbage accumulated). From 1976 to 1979 the herbage intake oflactating cows was determined at Lelystad during 23 grazing periods and during 28 stall-feeding periods. The precut swards were predominantly perennial ryegrass (Lolium perenne). A sward-sampling technique was used for estimating herbage intake by cows grazing swards for 3 or 4 days, with corrections for herbage accumulation during grazing. If herbage samples were cut both with a motor scythe and a lawnmower at the start and finish of grazing, accurate intake figures could be obtained. The effect of herbage mass (M, kg/ha) was studied in three and four trials in 1976 and 1977, respectively. Within each trial, different levels of M were established by allowing parts of a sward to grow for periods of time of variable length. The daily herbage allowance (kg/day) was kept equal for all treatments. The treatments were compared in time within the same group of twelve cows. The experiment was performed both at pasture and indoors. With advancing maturity, M increased significantly. There were no significant effects of higher levels of M on daily intake of organic matter (OM) from herbage, neither by grazing nor by stall-fed cows. In early summer, the herbage consumed by both groups showed a decline in digestibility at increasing maturity. As a consequence, daily intake of nutrients from herbage declined significantly at higher levels of Mand also affected milk production negatively. However, in late summer, these effects were not significant. The efficiency of consumption was not affected significantly by M, so the mass of residual herbage was proportional to M. In 1978 and 1979 three levels of daily herbage allowance (A) were achieved by varying the area grazed at equal levels of M for the treatments. Four groups of six cows each were used in an 8-week changeover design experiment performed twice each year. Higher levels of A had significant positive effects on daily intake of OM and of nutrients from herbage and on daily milk produc• tion/gra:i:ing animal. The efficiency of consumption declined at higher A levels. High amounts of residual herbage, however, had a strong positive effect on net regrowth of herbage, especially in early summer. In alternating grazing-cutting systems, a high allowance may be profitable, both for intake/animal and for the accumulation and consumption of herbage/unit area. At a mean allowance h;ve1 of 23 kg/day above 4.5 cm, our grazing cows consumed 13.6-14.8 kg/day of OM from herbage if no concentrates were fed. This amount was sufficient, at the quality of the herbage in our trials, for a daily prnduction of 4 % fatcorrected milk of 22-23 kg.
Citation
Meijs, J.A C., "Effect of Herbage Mass and Allowance upon Herbage Intake by Grazing Dairy Cows" (1981). IGC Proceedings (1977-2023). 2.
(URL: https://uknowledge.uky.edu/igc/1981/section11/2)
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Effect of Herbage Mass and Allowance upon Herbage Intake by Grazing Dairy Cows
An adequate supply of nutrients for grazing animals depends on the intake and nutritive value of herbage. Little information is available on factors affecting herbage intake of grazing cows, particularly for grazing systems that do not involve daily change of animals to a new pasture. Our objectives were to determine the effects of variation in herbage mass ( due to variation in stage of maturity) and of herbage allowance on herbage intake by grazing dairy cows and on efficiency of consumption (herbage consumed as a proportion of herbage accumulated). From 1976 to 1979 the herbage intake oflactating cows was determined at Lelystad during 23 grazing periods and during 28 stall-feeding periods. The precut swards were predominantly perennial ryegrass (Lolium perenne). A sward-sampling technique was used for estimating herbage intake by cows grazing swards for 3 or 4 days, with corrections for herbage accumulation during grazing. If herbage samples were cut both with a motor scythe and a lawnmower at the start and finish of grazing, accurate intake figures could be obtained. The effect of herbage mass (M, kg/ha) was studied in three and four trials in 1976 and 1977, respectively. Within each trial, different levels of M were established by allowing parts of a sward to grow for periods of time of variable length. The daily herbage allowance (kg/day) was kept equal for all treatments. The treatments were compared in time within the same group of twelve cows. The experiment was performed both at pasture and indoors. With advancing maturity, M increased significantly. There were no significant effects of higher levels of M on daily intake of organic matter (OM) from herbage, neither by grazing nor by stall-fed cows. In early summer, the herbage consumed by both groups showed a decline in digestibility at increasing maturity. As a consequence, daily intake of nutrients from herbage declined significantly at higher levels of Mand also affected milk production negatively. However, in late summer, these effects were not significant. The efficiency of consumption was not affected significantly by M, so the mass of residual herbage was proportional to M. In 1978 and 1979 three levels of daily herbage allowance (A) were achieved by varying the area grazed at equal levels of M for the treatments. Four groups of six cows each were used in an 8-week changeover design experiment performed twice each year. Higher levels of A had significant positive effects on daily intake of OM and of nutrients from herbage and on daily milk produc• tion/gra:i:ing animal. The efficiency of consumption declined at higher A levels. High amounts of residual herbage, however, had a strong positive effect on net regrowth of herbage, especially in early summer. In alternating grazing-cutting systems, a high allowance may be profitable, both for intake/animal and for the accumulation and consumption of herbage/unit area. At a mean allowance h;ve1 of 23 kg/day above 4.5 cm, our grazing cows consumed 13.6-14.8 kg/day of OM from herbage if no concentrates were fed. This amount was sufficient, at the quality of the herbage in our trials, for a daily prnduction of 4 % fatcorrected milk of 22-23 kg.
