Evaluation of Total Fecal Collection for Measuring Cattle Forage Intake

Abstract

Conventional digestibility trials with steers were conducted to evahutte relationships between actual forage intake and estimated forage intake using the total fecal collection procedure. Actual forage intake of 6 of the 9 forages fed was not accurately estimated by the widely used technique of dividing total fecal output by forage indigestibility estimated by in vitro procedures. This was because 4811 in vitro digestibility poorly estimated in vivo digestibility of 6 forages. Regression equations based on in vivo-in vitro digestibility relationships can reduce but not solve this problem because in vivo processes such as mastication and rumination are bypassed with in vitro techniques. The use of a 36-h microbial digestion period for nongrasses and a 72-96-h microbial digestion period for grasses shows potential to improve in vitro digestibility estimates of cattle in vivo digestibility. Another potential means of improving in vitro digestibility estimates is to select the highest digestibility value from forage or diet snmpies subjected to 36,4&, 60-, 72-, 84 and 96-h microbial digestion periods. Although mechanisms controlling forage intake in ruminants have been described by Ellis (1978) Mertens (1977), Church (1979) Van Soest (1982), and Mertens and Ely (1982), present techniques to measure intake of pasture and range forages by ruminants are laborious, costly, and subject to numerous errors (Cordova et al. 1978, Kartchner and Campbell 1980). The total fecal collection method discussed by Van Dyne (1969) has become the most favored approach for estimating forage intake by domestic ruminants. Although this procedure has been widely used, evaluation of its accuracy is limited (Van Dyne and Meyer 1964). Our objective was to evaluate the total fecal collection/ indigestibility method of Van Dyne (1969) for determining intake. Methods Two independent studies were conducted in 1980 and 1982 at the New Mexico State University farm. Details of each study will be reported separately. Study I Three feeding trials were conducted between May and September of 1980. Steers were fed alfalfa (Me&ago sativu) hay for 3 weeks before each trial. Five Hereford X Angus yearling steers, weighing approximately 340 kg each, were used in each trial. Trials were 14 days long with 10 days for adaptation and 4 days for data collection. Schneider and Flatt (1975: 124) concluded that a 5day adjustment period was adequate to clear previously fed diets from the digestive tract; Dubose and Embry (1956) reported that a 4-day collection period was sufficient to quantify fecal excretion in steers and lambs. Trials were in drylot pens where steers were fed ad libitum individually. Feed intake was determined by conventional handfed methods (Schneider and Flatt 1975:57). Steers were harnessed with fecal collection bags. Total fecal output was measured daily. Forages fed in the 3 drylot trials included milo hay (Sorghum vulgare) that had the heads removed, alfalfa hay, and oat hay (Avena sativu) that contained about 10% alfalfa.

Forage intake and botanical composition of feed for cattle fed Brachiaria/legume mixtures

“…Holechek et al (1986) studied Hereford × Angus yearling steers and found that the standard 48 h incubation procedure of Van Soest and Wine (1967) underestimated true in vivo digestibility of feeds ranging from only 1% for sainfoin (Onobrychis viciae-folia), to 9% for Timothy grass (Phleum pratense) and 13% for silver ) of the experimental diets. Bd = Brachiaria dictyoneura.…”

Feeding behaviour, feed intake, chemical and botanical composition of the diet of indigenous goats raised on natural vegetation in a semi-arid region of Zimbabwe

“…Estimates of the digestibility of the feed ingested by the goats were obtained using in vitro digestion techniques (Tilley & Terry 1963). Digestion of the feed samples with rumen liquor was prolonged to 72 h as recommended by Holechek et al (1986). An extended incubation period was used to avoid underestimation of digestibility in accordance with recommendations by Mertens & Ely (1982).…”

Influence of Two Native Shrubs on Goat Nitrogen Status

“…Our study involved only a limited number of feeds and it is quite possible Table 4 results are diet-specific relations that may not be applicable elsewhere. Total fecal nitrogen output has not been used as an indicator of protein status of ruminants grazing on rangelands; however, it can be evaluated through either total fecal collection (Stallcup et al 1975, Holechek et al 1986 or through external markers (Pond et al 1987). Total fecal nitrogen output may have potential as a future measure of grazing ruminant protein status.…”