Digestive Physiology and Nutrient Metabolism - Goat Science and Production - page 175

Adjustments are needed to consider effects of season,
environmental temperature, breed of animal, and physio-
logical stages of growth. Water intake usually is higher in
summer and with hot temperatures. Breeds of animals
adapted through natural selection to a shortage of water
may consume less water and lose less water with feces.
Gestation may increase water intake an average of 126%,
being even greater for animals bearing twins and triplets.
Water needed for lactation is estimated at 3.5 liter of water/
kg of milk production. The water content of milk is usually
suffi cient for growing the newborn up to 2-3 weeks of age;
however, providing free access to extra water is recom-
mended. The water need for nursing offspring is set at
8-13 mL/g body weight gain for growth plus another 120 -
140 mL/kg of metabolic body weight (BW 0.75 ) for mainte-
nance. Water needs for weaned animals for growth is set
at 7-8 mL/g of body weight gain with another 143 mL/kg
BW 0.75 required for maintenance (NRC, 2007 ).

information presented in this chapter has been extrapolated
from sheep and cattle data. Information regarding digestive
physiology and nutrient requirements for goats is very
limited and needs further investigation.

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Leek ,

SUMMARY
Goats are one of four existing true ruminant domesticated
agricultural species among ungulates that continue to be
very successful forage-consuming mammals. Goats benefi t
from a predigestive fermentation GI tract that allows for the
breakdown of fi ber to yield energy-rich fermentation prod-
ucts and the synthesis of microbial protein from nonprotein
nitrogen sources or recycled metabolic nitrogen. The other
benefi ts include production of vitamin B complex. Goats
use visual cues and taste to select for diets based on the
concentrate part of the plants and for shrubs and browse.
They have larger salivary glands that secrete tannin-bind-
ing protein in the saliva to detoxify tannin associated with
browse species. The newborn kid and up to 3 weeks of age
is preruminant, its intermediary metabolism is glucose
driven, and blood glucose is insulin sensitive. By 8 weeks
as a young ruminant, the intermediary metabolism shifts to
VFA driven and is less insulin sensitive.
Rumen dysfunction is not common in free-ranging
ruminants, and it appears to be manifested by mismanage-
ment of normal balances between animal and the diet.
They may include bloat, rumen acidosis, displaced aboma-
sums, urea toxicity, and nitrate toxicity. Goats require
nutrients for maintenance, growth, gestation, and produc-
tion of milk, meat, and fi ber. Carbohydrates and lipids
provide required energy; proteins are provided through
true protein or nonprotein nitrogen; vitamins and minerals
are provided through feeds or supplements; and water is
provided free choice. Knowledge of work of digestion and
nutrient metabolism in goats will help in proper manage-
ment and decision making when raising goats. Some of the

B.F. 1993a . Clinical diseases of the rumen: a

Physiologist 's view . Vet. Rec. 113 : 10 - 14 .
Leek , B.F. 1993b . Digestion in ruminant stomach . In: Duke 's
Physiology of Domestic Animals . Eleventh edition , M.
Swenson and W. Reece , eds. Comstock Publishing

Associates: Ithaca, New York .