Effect of roughage quality and period of day on rumen fill after meal termination, digestion, passage rates, and diurnal feeding behaviour in cattle fed on tropical roughage.
Bhiya, Siyabonga Thapelo.
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In tropical and subtropical regions, ruminant production is prominently dependent on tropical veld grass characterized by low nutritional quality. Feed intake is an essential constituent determining animal performance and the degree at which ruminants utilize feeds of poor quality is reigned by the passage from and degradability rates of digesta in the rumen. Feed intake by ruminants is regulated by rumen fill, which is further influenced by processes occurring in the rumen i.e. degradation, digestion, and passage rates. Furthermore, intake is a result of time spent eating and meal pattern hence, feeding behaviour regulates intake. Therefore, rumen fill, degradation, digestion, passage rates, and feeding behaviour are vital in understanding intake by ruminants. The objectives of the study were to: (i) determine the effect of roughage quality and period of day on diurnal rhythm of feeding behaviour patterns in cattle, (ii) determine the effect of roughage quality and period of day on rumen fill after meal termination, and (iii) confirm the effect of roughage quality on degradation, digestibility, and passage rates. Four ruminally cannulated Jersey heifers were assigned to four dietary treatments comprising improved roughage quality (IRQ), semi-improved roughage quality (SIRQ), moderately improved roughage quality (MIRQ), and poor roughage quality (PRQ). Consequently, heifers were randomly assigned to one of the four roughage diets in a 4 × Latin square design. Data on time spent on each of 11 different behavioural activities (drinking water, eating, idling standing and lying, ruminating whilst standing and lying, hedonic feeding, grooming, licking objects, tongue rolling, and other activities i.e. feed searching) was recorded. Roughage quality had no significant effect on the time spent on each behavioural activity except grooming and tongue rolling. The period-of-day affected time spent on each activity except for idling whilst lying and tongue rolling. Consequently, heifers spent more time eating during the day and ruminating at night. Roughage quality had no effect on fractional passage rates, rumen retention time, and mean retention time. Conversely, the mean retention time of solids in the hindgut was affected by roughage quality. Roughage quality had no effect on total rumen load, rumen DM, and rumen liquor. Total rumen load and rumen liquor were affected by period of day except for rumen DM. Total rumen digesta and rumen liquor were greater at evening than in the morning, afternoon, and late afternoon.