Abstract
The objective of this study was to evaluate the effect of the physical form of starter and inclusion of hay in the diet of preweaning dairy calves on performance, digestibility, ruminal development, and mRNA expression of genes involved in ruminal metabolism. Holstein × Gyr crossbred male calves (n = 38 1day old) were assigned to 3 treatments for 9 weeks: Control (n = 13; pellet starter with 4 mm diameter and 18 mm length and 4% steam-flaked corn), Ground (n = 12; same starter of the control but ground pass through a 4.0 mm sieve), or Ground plus 5% chopped Tifton hay GH (n = 13). All calves were fed 4 L/d of whole milk up to 63 d of age and were abruptly weaned at 64 d of age. Water and diets were offered ad libitum. Samples of ruminal contents were obtained from all animals at 30, 45, and 60 d of age to evaluate pH, ammonia nitrogen, and volatile fatty acids (VFA). At 55 d of age, an apparent digestibility assay was performed using 18 animals (n = 6/ treatment). At 65 d of age, the 18 animals were euthanized to evaluate the development of the digestive tract. The physical form of starter and the dietary inclusion of hay did not influence starter intake (Control 326 g/d, Ground 314 g/d and GH 365 g/d), daily weight gain (Control 541g/d, Ground 531g/d and GH 606g/d), feed efficiency, apparent nutrient digestibility, energy partitioning, nitrogen balance, ruminal pH, ammonia nitrogen concentration, VFA, the development of the digestive tract and the mRNA expression of genes involved in AGV metabolism.
Highlights
According to the NRC 2001 [1], besides being palatable, calf starter must be made of good quality ingredients to ensure adequate supply of protein, energy, fiber, vitamins, and minerals while having a coarse texture
The objectives of this study were to evaluate the effect of the physical form of starter and hay provision in the diet of dairy calves during the preweaning period on growth, nutrient digestibility, energy partitioning, nitrogen balance, rumen development and level of mRNA expression of genes involved in ruminal metabolism
Since the different treatments did not yield differences in nutrient digestibility, it is possible to conclude that the inclusion of 5% hay in the diet of calves during the pre weaning does not alter the digestibility of nutrients. This statement is reinforced by the results reported by [31], evaluating crossbred Holstein x Gyr calves fed a complete diet consisting of 6 L/d of liquid diet with 13.5% of total solids and a commercial starter, similar to the one used in the present study, verified digestibilities of 85, 88, 85, and 88% for dry matter (DM), organic matter (OM), crude protein (CP), and gross energy content (GE), respectively, in a trial performed between 50 and 55 d of age
Summary
According to the NRC 2001 [1], besides being palatable, calf starter must be made of good quality ingredients to ensure adequate supply of protein, energy, fiber, vitamins, and minerals while having a coarse texture. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript
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