Computer spreadsheets for predicting feed requirements and feed budgeting

Brookes, I. M.; Morris, S. T.; Parker, W. J.

doi:10.33584/jnzg.1993.55.2071

Cited by 4 publications

(4 citation statements)

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“…With the Model method, net pasture production was calculated as the sum of estimated pasture intake by grazing livestock, plus change in pasture cover from the start to the end of the period. Intake was estimated using a spreadsheet-based model (Brookes et al 1993) which calculated daily DM intake from published equations for energy requirement. Input data, collected over the 2-year period, were livestock numbers, ewe and lamb liveweights, mating and lambing date, lambing %, wool production and shearing date, and feed energy concentration.…”

Section: Methodsmentioning

confidence: 99%

Measuring production of continuously grazed hill pastures

Devantier¹,

Lambert²,

Brookes³

et al. 1998

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Estimates of pasture production are critical for comparing treatment effects in research trials, as inputs to decision support models, and for on-farm use in constructing grazing plans. We compared two techniques for measuring pasture production, over 2 years in 36 paddocks continuously grazed with sheep, on hill country at the Ballantrae Research Station. One technique (Cut method) involved harvesting pasture regrowth after trimming to a standard height. The other (Model method) calculated pasture production as the sum of grazing animal intake (estimated using a spreadsheet-based model with inputs including animal performance and pasture quality) and changes in pasture cover (above-ground biomass). Annual pasture production estimates were reasonably well correlated (R2 = 0.66), but those using the Cut method were 55% greater than using the Model method. Agreement was best in spring and summer, and poorest in autumn and winter. Factors contributing to these discrepancies included the contrasting starting conditions for the pasture at the start of each measurement period (shorttrimmed for the Cut method, and patch-grazed for the Model method); the effect of grazing in the Model method maintaining pastures in a more vegetative state; and the greater losses from senescence and decay in the Model method pastures. The potential for errors using the Model method was high where measurement periods were short, as accuracy of measurement of pasture cover can be suspect. The Model method probably better quantified net pasture production in grazed pastures. Keywords: grazing, hill pasture, intake, model, pasture production

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Section: Methodsmentioning

confidence: 99%

Measuring production of continuously grazed hill pastures

Devantier¹,

Lambert²,

Brookes³

et al. 1998

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“…Holmes et al (1989) later tabulated the annual feed requirements and stocking rate (cows/per 10 t DM eaten/ ha) for Jersey and Freisian cows ranging from 350 to 425 and 400 to 550 kg liveweight, respectively, and producing between 140 and 220 kg milkfat (244 to 383 kg MS) per lactation. These data indicate breed substitution rates, but even more usefully, anyone wishing to evaluate dairy systems could access the same spreadsheet (Brookes et al 1993) and generate feed consumption estimates for any management, cow liveweight and MS production combination. The most widely applied livestock standard in New Zealand dairying is the "base" dairy cow for measuring genetic progress.…”

Section: Evolution Of the System In New Zealandmentioning

confidence: 99%

“…The base ewe was assumed to weigh 55 kg (pre-mating), wean one lamb at 25 kg and consume 550 kg DM per annum. Feed consumption for the other ewe "types" was calculated using the Brookes et al (1993) spreadsheet model of sheep feed requirements. Seasonal variation in "SU equivalents" increases with ewe performance (Table 2).…”

Section: Evolution Of the System In New Zealandmentioning

confidence: 99%

“…The simplest modelling approach is to mechanistically simulate only the animal demand component of the farming system as described by Brookes et al (1993). However, because of the interaction between the livestock classes, pasture production and quality, and management (see Table 4), modelling the whole system provides more realistic estimates of animal substitution rates within a farm.…”

Section: A Modelling Approach Vs National Standardsmentioning

confidence: 99%

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Standardisation between livestock classes: the use and misuse of the stock unit system

Parker¹

1998

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The stock unit (SU) system is used extensively in New Zealand agriculture. These applications include inter- and intra-farm comparisons, rural lending and valuation, and farm system design and analysis. The livestock classes and performance levels to which SU conversion factors are applied has increased significantly since Professor Coop defined the ewe equivalent (EE) system, and now includes deer, goats and other non-conventional livestock species. This has led to a proliferation of SU values and their incorrect application and interpretation, especially in between-farm comparative analysis. Benchmarking provides a more economically rational way of improving the profitability of livestock farms than the use of standards based on SUs. Obtaining agreement on the specifications of animal-pasture-financial models to allow users to derive substitution rates between stock classes according to their farm's resources and management practice is preferred to publishing national standards for SUs. Keywords: comparative analysis, livestock classes, standardisation, stock unit

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