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Effects of Water Restriction on Nutrient Digestibility in Sheep Receiving Fixed Water: Feed Ratios¹

University of Missouri,^,3 Columbia 65201

Abstract

WATER to feed ratios of 1.75:1 and 1:1 were studied at two levels of intake of pelleted native hay, 600 g or 1,200 g per day. Eight rumen-fistulated yearling wethers received one of four treatments, low feed low water (LFLW), high feed low water (HFLW), low feed high water (LFHW) and high feed high water (HFHW). The trial was replicated four times. The required amounts of feed and water were offered and any refusals were inserted into the rumen so that the exact amounts were always consumed. The digestibilities of dry matter (DM), and nitrogen (N), as well as rumen pH and VFA levels, hematocrit and plasma urea-nitrogen (PUN) were determined. The rumens of sheep receiving HFLW rapidly became impacted and defecation greatly decreased, therefore, these sheep completed a 7-day digestion trial in only one of four replicates. The apparent digestibility of all nutrients for the HFLW sheep was extremely high because of the small fecal output. Their rumens were more acid and contained higher levels of VFA, although this may have been due to a decreased moisture level only. Their hematocrit and PUN values were higher indicating some hemoconcentration. The LFLW sheep had higher nutrient digestibilities than sheep fed either LFHW or HFHW but other measurements were similar. Urinary and fecal water losses were influenced by water intake, but the contribution of urinary loss was more significant for sheep than that reported for cattle. It is suggested that the elevated digestibilities usually observed with animals on restricted water intake are probably an artifact due to dry matter accumulation rather than to a real increase in fermentation or digestion.

¹ Contribution from the Missouri Agricultural Experiment Station. Journal Series No. 6274. Approved by the Director.

² The assistance of S. E. Grebing, O. Lewis and C. Wehmeyer is gratefully acknowledged.

³ Department of Animal Husbandry.