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Natural dry matter intake fluctuation impacts performance, feeding behavior and rumen morphometrics of feedlot cattle: 10 years of data assessment
This study aimed to evaluate the impact of natural DMI fluctuation on performance, carcass characteristics, feeding behavior, blood metabolic profile and rumen morphometrics of feedlot cattle. All 10 experiments used for this analysis were conducted at the feedlot research station (São Paulo State University, Botucatu campus) from 2006 to 2015. Data were collected from 838 yearling bulls fed high-concentrate diets in group pens (3 or 4 animals per pen; n = 238 pens). Pens were considered the experimental unit for this study. Daily DMI fluctuation was calculated for each pen as the difference in intake between consecutive days. Daily DMI fluctuation was expressed as variation according to the following formula: DMI fluctuation in kilograms/DMI of the previous day in kilograms × 100. The final data from each pen represented the average daily DMI fluctuation for the entire feeding period. Based on the overall median of DMI fluctuation of 5.62%, cattle were classified into two groups: high- or low-fluctuation. All data analysis was performed in R using a mixed model approach where pens and years were random variables and fluctuation group was considered as fixed. The low and high fluctuation groups presented a DMI fluctuation average of 4.79% and 6.74%, respectively. Low fluctuation group performed better than high fluctuation one, with greater ADG (1.45 kg vs. 1.39 kg; P = 0.05), DMI (9.16 kg vs. 8.89 kg; P = 0.06), total weight gain (143 kg vs. 137 kg; P = 0.08), LM area daily gain (0.18 cm2 vs. 0.16 cm2; P = 0.03), and lower shear force (4.71 kg vs. 5.41 kg; P = 0.03). In terms of feeding behavior, low fluctuation group spent more time ruminating (341 min vs. 322 min; P = 0.04), less time resting (893 min vs. 917 min; P = 0.06) and visited the water trough less often (6.6 visits vs. 7.4 visits; P = 0.04). No effects of DMI fluctuation was observed (P > 0.10) on blood metabolic profile, rumenites incidence and rumen morphometrics. This multiannual evaluation illustrates the severe impact of an apparent small DMI intake fluctuation on feedlot performance and raises even more awareness to bunk management and proper nutrition.
Keywords: feedlot, intake fluctuation, performance