Abstract
The objectives of this study were to investigate how milk replacer (MR) allowance and differing concentrations of starch and neutral detergent fiber in starter alters visceral tissue and overall growth of the calf. Calves were randomly assigned to 1 of 4 dietary treatments (n = 12 per treatment) arranged in a 2 × 2 factorial based on daily MR allowance (MRA) and amount of starch in pelleted starter (SPS) as follows: 0.691 kg of MR/d [dry matter (DM) basis] with starter containing low or high starch (12.0% and 35.6% starch, respectively) and 1.382 kg of MR/day (DM) with starter containing low or high starch. All calves were housed in individual pens with straw bedding until wk 5 when bedding was covered to minimize intake. Calves were fed MR twice daily (0700 and 1700 h) containing 24.5% crude protein (DM) and 19.8% fat (DM), and had access to pelleted starter (increased by 50 g/d if there were no refusals before weaning, and then 200 g/d during and after weaning) and water starting on d 1. Calves arrived between 1 and 3 d of age and were enrolled into an 8-wk study, with calves undergoing step-down weaning during wk 7. Intakes were measured daily, and body weight (BW) and blood samples were recorded and collected weekly. Calves were dissected in wk 8 for visceral tissue measurements. Overall, there was increased MR DM intake for the high- (0.90 ± 0.01 kg/d; ± SE) compared with the low-MRA (0.54 ± 0.01 kg/d) calves, whereas starter DM intake increased in low- (0.47 ± 0.05 kg/d) compared with high-MRA (0.20 ± 0.05 kg/d) calves, which was driven by increases in wk 6, 7, and 8. High-MRA calves had increased BW during wk 2, 3, 4, 5, 6, and 7. The difference in BW disappeared by wk 8, with overall average daily gain having a tendency to be increased in high (0.57 ± 0.04 kg/d) compared with low-MRA (0.50 ± 0.04 kg/d) calves, whereas average daily gain was increased in high-MRA calves during wk 2 and 3 and increased in low-MRA calves during wk 7 and 8. There were several differences throughout visceral tissue measurements, but most notably, an increase in rumen mass (i.e., full, empty, and digesta weights) in low- compared with high-MRA calves, as well as in low- compared with high-SPS calves was observed. The length, width, and 2-dimensional area of rumen papillae were also increased in low- (area: 0.88 ± 0.03 mm2) compared with high-MRA (0.46 ± 0.03 mm2) calves. The majority of differences were attributed to increased MR allowance, which contributed to reduced pelleted starter intake by more than 50% and reduced rumen development, whereas differences in starch intake from the completely pelleted starter had minimal effects on overall growth and tissue measurements.
Highlights
There has been interest in feeding dairy calves a high amount of milk or milk replacer (MR) during the preweaning period, which has promoted greater rates of weight gain, structural growth, and feed efficiency (Diaz et al, 2001; Khan et al, 2007; Sweeney et al, 2010)
We hypothesized that higher MR-fed calves would have increased growth performance and enhanced visceral tissue growth compared with lower MR-fed calves preweaning, whereas starch concentrations in starter would have no effect on growth performance or growth of visceral tissue
Calves were randomly assigned to 1 of 4 dietary treatments (n = 12 per treatment) arranged in a 2 × 2 factorial based on daily MR allowance (MRA) and amount of starch in pelleted starter (SPS) as follows: (1) 0.691 kg of MR dry matter (DM)/d with pelleted starter containing low starch (12.0% DM basis; LL), (2) 0.691 kg of MR DM/d with pelleted starter containing high starch (35.6% DM basis, LH), (3) 1.382 kg of DM/d with pelleted starter containing low starch (HL), and (4) 1.382 kg of DM/d with pelleted starter containing high starch (HH), which started in the second week after all calves received 0.691 kg of DM/d for the first week
Summary
There has been interest in feeding dairy calves a high amount of milk or milk replacer (MR) during the preweaning period, which has promoted greater rates of weight gain, structural growth, and feed efficiency (Diaz et al, 2001; Khan et al, 2007; Sweeney et al, 2010). Calf starters containing readily fermentable carbohydrates (i.e., starch), which are fermented to produce VFA in the rumen, play a critical role in stimulating rumen epithelial growth (Sakata and Tamate, 1978; Gorka et al, 2009; Malhi et al, 2013) This rumen tissue growth and development is important for the metabolic transition to a true functional ruminant. Recognizing current industry feeding trends, it is important to investigate how a high amount of MR feeding influences the intake of pelleted starters containing differing concentrations of starch, and, subsequently, its effects on growth performance of dairy calves during both the pre- and postweaning phases. The objectives were to measure the effects of amount of MR fed and level of starch in starter on growth performance, blood metabolites, and visceral tissue growth
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