Predicting Feed Intake of Food-Producing Animals (1987) / Chapter Skim
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7. Sheep
7. Sheep
Pages 75-82
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From page 75... ...
When sheep are fed to appetite and intake is accurately predicted, nutrient requirements can be expressed as a percentage of the diet, which also 75 most appropriately expresses requirements for rumen fermentation (Fox et al., 1984~. The purpose of this chapter is to identify and discuss the primary factors influencing feed intake in sheep and to present equations and adjustment factors that can be used to predict feed intake of sheep under widely vary ing feeding and environmental conditions.
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From page 76... ...
As digestible energy content is increased, for example, when grain in the diet is increased, metabolic controls become the dominant factors limiting intake. The use of diet energy concentration to predict intake describes the combined effects of physical fill and metabolic controls on appetite.
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From page 77... ...
PREDICTING DRY MATTER INTAKE OF SHEEP Based on the information presented in Chapter 1, the biological factors that appear to control intake are those related directly to direct dietary effects (distension of body wall, ruminal pH and acetate concentration, hepatic uptake of propionate) and metabolic factors mediated by the central nervous system, including size of adipose mass and demand for nutrients.
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From page 78... ...
However, silage intake by sheep may follow the pattern described by Equation 5 when ensiled at a more mature stage or at a low water content where lactic acid content is likely to be lower or oil meal supplements are used. More research is needed to separate out more clearly the independent effects of these variables.
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From page 79... ...
were summarized and tested against the various equations presented above. Included were diets ranging from corn silage to all concentrate fed to growing lambs and diets ranging from corn stover to high-energy lactation rations fed to ewes during the course of complete reproductive cycles.
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From page 80... ...
/' Overall 62 1.27 1.70 1.78 1.53 2.45 2.62 Early gestation 60 1.03 1.42 1.31 1.00 2.29 2.41 Mid-gestation 61 1.11 1.31 1.42 1.12 2.28 2.41 Late gestation 65 1.42 1.71 1.82 1.61 2.22 2.38 Lactations 61 1.60 2.44 2.73 2.54 3.02 3.27 Maintenance 60 0.90 1.19 1.07 0.74 2.35 2.47 aThe pelleted diets were whole or pelleted corn based, with alfalfa meal as a roughage. The silage was whole plant corn silage.
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From page 81... ...
Digestibility will be reduced 5 to 10 percent, but the benefit of greater energy intake to more nearly meet maintenance needs or intake over maintenance that is available for productive functions may offset this effect. In many circumstances, the reduced wastage plus the greater rate of passage benefits may more than offset digestibility reduction and economic costs.
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From page 82... ...
will allow intake to increase during cold weather and thus reduce their critical temperature. Protecting sheep from direct exposure to heat stress will prevent intake reduction, allowing energy intake over maintenance and, thus, performance to be maintained.
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