Abstract
Feed restriction and fasting experienced during commercial production negatively affect unweaned calves' behavior and health status. Transportation and stays at assembly centers are the main factors generating these disorders. For this study, 20 unweaned Angus-Holstein bull calves [44.1 ± 2.04 kg of body weight (BW) and 14.7 ± 0.63 d of age (± standard error)] were used to evaluate the effects of feed restriction and fasting on performance, energy status [serum concentration of glucose, β-hydroxybutyrate (BHB), and nonesterified fatty acids], and gastrointestinal permeability [serum concentration of citrulline, chromium (Cr)-EDTA, lactulose, and d-mannitol]. Calves were randomly assigned to 1 of 4 treatments that simulated the feed restrictions of an assembly center situation on one hand, and the fasting hours during transportation on the other. Treatments were as follows. Control (CT): from d -4 to -1, calves were fed 2.5 L of milk replacer (MR) twice daily; concentrate and straw were offered ad libitum. Mild (MD): calves were fed only MR (d -4 to -1) as described for CT, and on d -1 calves were subjected to a 9-h feed withdrawal. Moderate (MO): calves were fed only MR (d -4 to -1) as described for CT and on d -1 subjected to a 19-h feed withdrawal. Severe (SV): calves were fed only 2.5 L of a rehydrating solution twice daily (d -4 to -1) and on d -1 subjected to a 19-h feed withdrawal. From d 0 to d 42 (weaning) all calves were fed the same feeding program (MR, concentrate, and straw ad libitum). Results showed that BW was greater for the CT treatment compared with the others from d 0 to d 7, whereas BW of SV was lesser compared with the others from d -1 to d 7. No differences among treatments were observed at weaning. At d 2 concentrate intakes of MD, MO, and SV were lesser compared with CT. By d 4, concentrate intake of SV was similar to that for CT and greater than MD and MO. Similarly to BW, no differences in concentrate intake among treatments were observed at weaning on d 42 of the study. At d -1 for SV and d 0 in all restricted calves, serum glucose concentration was lesser compared with CT. At d -1 and 0, nonesterified fatty acids and BHB serum concentrations were greater in the SV calves compared with the other treatments. By d 2, serum concentrations of nonesterified fatty acids, BHB, and glucose were restored to CT levels. At d -1 serum citrulline concentration was lesser in SV and greater in MD calves. The CT calves had lower serum concentrations of Cr-EDTA (d -1 and d 0), lactulose (d 0), and d-mannitol (d 0) compared with the other restricted calves. Results showed that degree of dietary restriction, type of liquid diet (MR or rehydrating solution), and fasting hours (9 vs. 19 h) affected calves' BW, concentrate intake, and serum concentration of markers indicative of energy status and gastrointestinal permeability.
Highlights
Unweaned male dairy calves are considered a byproduct of the dairy industry, and their marketing for meat production has become a common practice
To simulate calves staying at an assembly center, different feed restriction levels were applied, and to simulate calf transport, different fasting duration times were combined with feed restriction levels, resulting in the following 4 randomly assigned treatment groups
Differences in body weight (BW) at d 7 (Figure 1) among MD, MO, and SV treatments could be related to the severity of the feed restriction (MR or rehydration solution (RS)) and the duration of fasting (9 vs. 19 h)
Summary
Unweaned male dairy calves are considered a byproduct of the dairy industry, and their marketing for meat production has become a common practice These calves can be marketed and transported from their origin farms directly to their final destinations or be marketed through assembly centers before being transported to calf-rearing facilities (Pardon et al, 2014; Wilson et al, 2020). Pisoni et al.: FEED RESTRICTION AND GUT PERMEABILITY IN CALVES restriction Overall, these conditions have been shown to negatively affect calves’ health, immunological status, and energetic balance (Cernicchiaro et al, 2012; Renaud et al, 2018; Marcato et al, 2020). Several studies conducted in bovines have demonstrated that short-term (Zhang et al, 2013) or progressive (Kvidera et al, 2017) feed restriction can affect tract barrier function and generate changes in intestinal architecture
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