Bulgarian Journal of Agricultural Science
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Effect of different physical forms of calf starter feed on some rumen parameters
Gancho Ganchev, Todor Slavov, Krum Nedelkovorcid
Abstract: The aim of the present experiment was to compare the effect of the physical forms of a starter for dairy replacement calves on some rumen fermentation parameters. Nine male calves at 4 days of age and averaging 41.3 (SD = 3.6) kg were divided into three groups. The calves were housed in individual hutches bedded with straw. The calves were weaned at 56 days of age and remained in the experiment until 70 days of age. Three starter feeds of different physical forms were tested: 1) Whole maize grain plus pelleted protein concentrate (WMP); 2) Pelleted starter feed (PSF); and 3) Starter in a meal form with coarsely ground maize (MSF). The ingredient and chemical composition of the three starter feeds were similar. The calves from all groups received 4 L of whole milk until 56 days of age. The liquid feed was provided twice a day from 4 to 35 days of age, and once a day from 36 to 56 days of age. From 35 days of age, calves were offered alfalfa hay ad libitum. Ruminal fluid samples for pH, volatile fatty acids (VFA), ammonia and total number and genera of ciliated protozoa in the ruminal contents were collected using oral stomach tube on days 28, 42, 56 and 70 of the experiment. The results suggested that the physical forms of the starter feed did not affect the pH, VFA and ammonia in the rumen. The total number of ciliated protozoa in the rumen was increased (P < 0.05) at 56 and 70 days of age for calves fed the starter feed in PSF form compared to the MSF. The number of ciliated protozoa of the genus Isotricha was higher (P < 0.01) after feeding with PSF at the age of 28, 42 and 70 days compared with the group fed with MSF diet.
Keywords: calves; physical forms; protozoa count; rumen fermentation; starter feed
Citation: Ganchev, G., Slavov, T. & Nedelkov, K. (2026). Effect of different physical forms of calf starter feed on some rumen parameters. Bulg. J. Agric. Sci., 32(2), 447–452
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Date published: 2026-04-29
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