The in vivo digestibility and the rates of degradation and passage of alfalfa hay (AH) and vetch straw (VS) were compared in three Granadina goats and three Segureña wethers fed at approximately maintenance level, using a change over design. The nylon bag technique was used to estimate the fractional rate of degradation of the feeds in the rumen. The fractional outflow rate of hay and straw particles was determined with chromium as a marker. No significant differences in the digestibility coefficients of nutrients between animal species were found. Nitrogen retention expressed as coefficients of both nitrogen intake and digested nitrogen was lower (P < 0.01) in goats than in sheep when VS was offered. There was no significant difference between goats and sheep in the effective degradability (measured at outflow rates in the range of 0.027 to 0.032 h-1) of dry matter (DM) for either forage. However, the effective degradabilities of the neutral detergent fibre (NDF) and crude protein (CP) of VS were lower (P < 0.01 and P < 0.001, respectively), in goats than in sheep. The degradation rates of DM, NDF and CP were not significantly different (P > 0.05) between goats and sheep. Also, the fractional rate of passage of particles from the rumen was not different (P = 0.056) between species, although there was a tendency for an increased outflow rate in goats. In a second experiment the effects of animal species, type of diet and frequency of feeding on rumen fermentation pattern were studied following a factorial design. Four goats and four wethers were used. They were randomly allocated to three dietary treatments: AH, VS or a 50:50 mixture of AH and VS (AH/VS). Rations were offered in two or three meals daily and samples of rumen content were obtained at 09.00, 11.00, 13.00, 15.00, 17.00 and 19.00 h. No difference in rumen pH was found between goats and sheep. Total volatile fatty acids and ammonia concentrations were higher (P < 0.001) in sheep than in goats. The molar proportions of acetate and isovalerate were higher (P < 0.01 and P < 0.001, respectively) in goats than in sheep, whereas the opposite was true for the molar proportion of n-butyrate. Feeding frequency had a slight effect on the rumen parameters measured. It is concluded that only minor differences in the digestive capacity and rumen activity of sheep and goats can be expected when they are fed on medium quality forages.
Three experiments were conducted in Granadina goats and Segureña wethers fed at maintenance level to evaluate the effect of including a mixture of barley and a new by-product derived from olive oil extraction (two-stage dried olive cake) on ruminal degradation and passage kinetics (Exp. 1), fermentation pattern and protozoa population (Exp. 2), and urinary purine derivatives excretion (Exp. 3). Polyethylene glycol was supplied to the animals to evaluate the effects of tannins contained in the by-product. The experimental diets were as follows: alfalfa hay and alfalfa hay plus a concentrate, formulated with two-stage dried olive cake, barley, and a mineral-vitamin mixture either with or without the addition of polyethylene glycol to the drinking water. The inclusion of two-stage dried olive cake in the diet resulted in an increase of condensed tannins. Ruminal VFA concentration in goats and wethers increased (P < 0.05) and ammonia N (NH3-N) concentration decreased (P < 0.05). The inclusion of two-stage dried olive cake decreased (P < 0.001) urinary allantoin excretion only in wethers. Ruminal degradation profiles and fractional passage rates were similar in goats and wethers. The polyethylene glycol supply increased (P < 0.001) DM and N degradation rates in both animal species but did not modify the fractional passage rate. Ruminal fermentation patterns were also similar in goats and wethers and were affected by polyethylene glycol supply. In general, Entodiniomorphida and Holotricha protozoa counts were higher (P < 0.05) in the rumen of goats than of wethers. Protozoa count in wethers responded more to polyethylene glycol supply than in goats. The present work presents the first data obtained from a comparative study with sheep and goats concerning urinary excretion of purine derivatives. The excretion was similar in both animal species when fed alfalfa hay; however, polyethylene glycol affected only urinary allantoin excretion in wethers. Results suggest a greater sensitivity of wethers than of goats to two-stage olive cake condensed tannins.
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