Relationships between eating rate of sheep and live weight gain, weight and fill of the gastrointestinal tract.

Nine ewe and eight wether weanling lambs were fed a pelleted diet containing 60% roughage and 40% concentrate for 12 h/day. Feed consumption (FC) was measured during the first 30 and 60 min (FC-30, -60). Total daily consumption (FCT) was also measured. With these data, feed efficiency (FE), eating rate index (ERI = FC/BW.75) and propensity to eat (percentage FC/unit of time) were calculated. After the completion of these studies, the lambs were slaughtered and weights of the full gastrointestinal tract (GIT) organs, empty organs and wet digesta were obtained. Dry digesta in the organs were estimated from samples of oven-dried digesta. Respective values for males and females were: FE, 6.36 and 7.50 (P less than .01); average daily gain (ADG), 285 and 230 g (P less than .02); FC-30, 597 and 488 g (P less than .05), and FC-60, 706 and 583 g (P less than .05). Significant correlations were found only for females for FC-30 with FCT, ADG with FE and FC-60 with FE (P less than .05). Significant correlations of ERI-30 and ERI-60 with ADG and FE were also observed for the combined sex data. Correlations between eating rate terms and organ or digesta weights were significant only for some reticulorumen (RR) and abomasal parameters. When data from the GIT were correlated with animal performance (FC, ADG, FE), the highest correlations observed were generally for females. Correlations with organ or digesta weights tended to be highest for the small intestine (SI) and ADG; these were followed by values of about equal magnitude for RR organ or digesta weights and ADG or FE. The highest correlations were those between ADG and full organ weight of the SI for males (.86, P less than .01) and between ADG and wet digesta weights of the SI for females (.86, P less than .01). It is concluded that organ and (or) digesta weights of the SI are highly related to animal performance and may be as important as the RR in affecting voluntary feed consumption of pelleted diets.