Changes in the Tissue and Volume of the Stomachs of Calves Following the Removal of Dry Feed or Consumption of Inert Bulk

Open Access
Publisher Website
Google Scholar
Abstract
Twelve Holstein heifer calves at 16 and 38 wk. of age were sacrificed after a growth study in which 6 had voluntarily consumed a high-concentrate diet and six a high-roughage diet. Ratios of hay to concentrate were 9:1 and 1:9. Four bull calves, 2 fed only milk and 2 fed milk while consuming shavings, also were studied. Rumen papillae disappeared in the calves reversed to milk diets. The rumen collapsed around less fill, but maintained the same potential (water-filled) volume after 18 wk. of milk feeding, as had existed in calves of the same age on dry feed slaughtered at the beginning of the reversal period. This observation was interpreted as indicating a stasis, and not retrogression of reticulo-rumen volume. The amount of muscular tissue (fat-free dry) was less in reversal calves, but the effect was not statistically significant. A stasis in omasal tissue growth occurred, and the abomasum continued to grow at the same rate as body size. Mucosal and muscular growth were independent. (1) Reticulo-rumen mucosa retrogressed at a more rapid rate than muscle. (2) Muscular development was extensive in the absence of mucosal development in calves consuming shavings. (3) Compared to muscle, well-developed mucosa contained lower nitrogen percentages when expressed on a fat-free dry matter basis (13.3 and 15.1%, respectively). Rumen papillae length was greater in faster-gaining (high-concentrate) calves. Apparently, both rapid growth and papillary development were due to the higher energy levels consumed by these animals.