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Whole or Ground Oats in Calf Starters: Effects on Rumen Fermentation and Rumen Development
A series of 3 trials were conducted to determine effects of whole or ground oats in starter grain on rumen fermentation and development of pre-weaned calves. Male Holstein calves (43.1 ± 2.3 kg BW at birth; n = 8, 9, and 7 for trials 1, 2, and 3 respectively) were housed in individual pens in a heated facility; bedding was covered with landscape fabric to avoid any consumption of bedding. In trials 1 and 2 only, calves were fitted with a rumen cannula by wk 2 of life. Water was offered free choice, and milk replacer was fed to 12% of birth BW. In all trials a fixed amount of starter (containing 25% oats either ground and in the pellet or whole; 18.7% CP, 12.7% NDF) was offered daily based on average intakes of calves on similar milk replacer diets; orts were fed through the cannula in trials 1 and 2. Calves were randomly assigned to all pelleted starter (Ground; n = 11) or pellets plus whole oats (Whole; n = 13). Rumen contents (trials 1 and 2) were sampled weekly at -8, -4, 0, 2, 4, 8, and 12 h after grain feeding for pH and VFA determination. Calves were euthanized 3 wk (trial 1) or 4 wk (trials 2 and 3) after grain was offered; organs were harvested, emptied, rinsed, and weighed to gauge digestive organ development. Experimental design was complete randomized block. Starter intake was not different between treatments by design (P > 0.05); weekly intakes were 481 ± 24; 1,575 ± 30; 3,176 ± 48; 4,656 ± 143 g for wk 1 to 4 of grain feeding. Weekly measurements of rumen digesta pH and molar proportion of individual VFA did not change with diet. Molar proportion of butyrate and pH linearly decreased with age while acetate proportion increased. Reticulorumen weight (569 Ground vs. 503 Whole ± 24 g) and papillae length (0.75 Ground vs. 0.68 Whole ± 0.03 mm) tended to be greater for Ground (P < 0.1) while abomasum weight (240 Ground vs. 274 Whole ± 9 g) was greater for Whole (P< 0.05). Liver and omasum weights were not different. Under the conditions of this study physical form of oats in starter grain did not affect rumen fermentation parameters; greater rumen weight and papillae length in Ground may be a result of greater nutrient availability of ground oats.
Keywords: Rumen-development, Oats