عنوان مقاله [English]
Background and Objectives: Lower critical temperature for a neonatal dairy calf ranges from 5 to 15°C. As the temperature drops below the calf's lower critical temperature, calf needs more dietary energy to maintain body temperature. If calves are fed the same amount of milk as under moderate environmental conditions, less energy will be available to support growth. In most small and medium holder Iranian farms, dairy calves are usually fed 4 L/d (equivalent to approximately 10% of birth weight) of liquid feed in fixed amounts until they are weaned on 60 d old. The aim of present experiment was to investigate the effect of milk replacer plane of nutrition (restricted vs. moderated; 4 vs. 6 L/d) on starter feed intake patterns, feeding behavior, and health in cold-stressed neonatal Holstein calves.
Materials and Methods: Twenty-four (n = 12 calf/treatment; 3 d old) newborn female Holstein calves (40.1 ± 0.84 kg; BW ± SE) were randomly assigned to receive either restricted (4 L/d; RPN) or moderated (6 L/d; MPN) milk replacer (21% crude protein, 17% fat, and 43% lactose on a dry matter basis) plane of nutrition. Calves were reared outdoor in individual pens with a mean ambient temperature of 3°C during the experiment. Calves were fed milk replacer twice daily at 0800 and 1700 h in pens bedded with wheat straw. Milk replacer intake, starter feed intake, fecal score (on a 1–5 score system), and ambient temperature were measured daily. All calves were visually observed (every 5 min) to monitor the eating, ruminating, resting, standing, lying, drinking, and non-nutritive oral behaviors for a 8-h period (between 0900 and 1700 h) once per 3 successive d before weaning (d 50–52 of the trial) as well as once per 3 successive d after weaning (d 83–85 of the trial). Repeated-measures ANOVA was used to compare feed intake and feeding behaviors between treatment groups, and logistic regression model using a binomial distribution (PROC GLIMMIX) was used to assess the chance of diarrhea (≥3) and needs to medication before weaning. Poisson regression model (PROC GENMOD) was also used to test group differences in frequency and duration of diarrhea and days medicated before weaning.
Results: Milk replacer dry matter intake and average daily gain were greater in MPN vs. RPN fed calves. Meal pattern including meal frequency (6.0 bouts/8-h), meal length (10.7 min), inter-meal interval (80.1 min), eating rate (14.5 g of starter feed/min), and meal size (154.5 g of starter feed/bout) and rumination pattern including the number of bouts (3.8 bouts/8-h), rumination duration (17.1 min), and interval between rumination bouts (129.2 min) were not affected by treatment groups. Time spent ruminating and time devoted to drinking were greater in MPN vs. RPN calves. Meal frequency, meal length, eating rate, meal size, rumination duration and time for standing were greater but inter-meal interval and time for lying were lower during the post- vs. pre-weaning period. Non-nutritive oral behaviors and diarrhea frequency were not affected by experimental treatments. Calves receiving RPN vs. MPN had lower chance of diarrhea and greater chance of medication. Days with diarrhea and medication days were shorter in RPN vs. MPN fed calves.
Conclusion: Feeding MPN increased average daily gain in cold stressed calves. The lack of significant different in starter intake between experimental treatments was probably due to the lack of difference in the number and size of the meals. Although the calves fed MPN experienced higher chance of diarrhea with longer duration, but the incidence of diarrhea was not affected by the level of milk replacer feeding.