Effect of amount of milk replacer fed and the processing of corn in starter on growth performance, nutrient digestibility, and rumen and fecal fibro lytic bacteria of dairy calves

Steam Flaking

Effect of amount of milk replacer fed and the processing of corn in starter on growth performance, nutrient digestibility, and rumen and fecal fibrolytic bacteria of dairy calves

INTRODUCTION:

Feeding milk or milk replacer (MR) at more than 10% of body weight can lead to better weight gain and improved feed efficiency. The importance of weight gain in heifers is significant due to its relationship with higher milk production. Weight gain in calves decreases at the time of weaning, which poses a challenge in raising nursing calves.

The rate of solid feed intake has a negative relationship with the rate of liquid feed intake in calves. It has been reported that feeding high amounts of milk replacer (MR) delays rumen development and reduces nutrient digestibility, especially fiber, after weaning. Feeding starter feed (CS) with processed grains promotes the production of butyrate and propionate and the growth of rumen papillae due to increased fermentation and digestion levels. However, this increase is not due to higher CS intake. In fact, it has been shown that feeding processed grains (e.g., steam-rolled and steam-flaked) decreases CS intake but increases starch digestibility of the grain and short-chain fatty acids, thereby improving feed efficiency. ​

Goals:

The objective of this study was to investigate the effects of the milk replacer (MR) feeding rate and corn processing in the calf starter (CS) on growth performance, nutrient digestibility, and fiber-degrading bacteria in the rumen and feces of dairy calves.

MATERIALS AND METHODS:

To this end, 48 castrated male Holstein calves, aged 2 to 3 days on average, were randomly assigned to one of four treatments in a 2 × 2 factorial design with two levels of milk replacer (MR) feeding rates—low (LO) at 0.749 kg MR and high (HI) at 1.498 kg MR—and two types of corn processing in the starter feed: whole corn (WC) and steam-flaked corn (FC). Calves in the LO group (24 calves) received 0.749 kg/day (on a dry matter basis) of MR for 6 weeks, followed by 0.375 kg/day of MR during the last week. Calves in the HI group received increasing amounts of MR: 0.749 kg/day in week 1, 0.851 kg/day in week 2, 1.135 kg/day in week 3, 1.498 kg/day in weeks 4 and 5, and finally 0.749 kg/day in the last week. The study included a nursery period (weeks 1 to 8) and a growth period (weeks 9 to 16), and calves were weaned at 6 weeks of age.

RESULTS AND DISCUSSION:

Rumen fluid and fecal samples were collected in weeks 5 and 8 to determine the quantity of fiber-degrading bacteria and nutrient digestibility. In this study, the populations of rumen cellulose-degrading bacteria (Ruminococcus albus, Fecalibacterium prausnitzii, and Fibrobacter succinogenes S85), hemicellulose-degrading bacteria (Butyrivibrio fibrisolvens, Prevotella sp., and Ruminococcus flavefaciens), and fiber-degrading bacteria (Clostridium cluster IV) were measured. ​

In this study, it was observed that calves in the HI treatment consumed 48.6% more milk replacer (MR) compared to the LO treatment, but in contrast, they consumed 33% less starter concentrate (CS) than the LO group. During the early weeks (2 to 7 weeks), the higher CS intake in calves fed the LO diet led to increased ruminal fermentation activity and improved digestibility of dry matter (DM) and organic matter (OM) before weaning, as well as better digestibility of NDF and ADF both before and after weaning. Conversely, calves fed the HI diet showed higher digestibility of DM and OM during the milk-feeding period, indicating they received more metabolizable energy (ME).

 

Chart 1. Effect of Experimental Treatments (HI-FC, HI-WC, LO-FC, and LO-WC) on Nutrient Digestibility

Calves fed with the HI treatment showed better weight gain from weeks 2 to 5 and had higher body weight from weeks 3 to 8 compared to those fed with LO. However, in week 7, calves on the HI treatment had a lower average daily weight gain compared to calves on the LO treatment. The higher growth rate in body weight and skeletal development during weeks 9 to 16 for calves fed LO was likely due to better gastrointestinal development and improved transition from liquid feed to solid feed in the LO group. Although overall weight gain before and after weaning was higher in HI-fed calves compared to LO, due to the greater efficiency of solid feed utilization in weeks 9 to 16 by the LO group, calves fed with the HI diet lost their early growth advantage by week 16.


 ​

Chart 2. Effect of experimental treatments (HI-FC, HI-WC, LO-FC, and LO-WC) on calf weight gain during weeks 1 to 6 (pre-weaning), weeks 7 to 8 (weaning), and weeks 9 to 16 (post-weaning).

It is possible that HI calves, when weaned with a step-down reduction in milk volume during the sixth week over one week, experienced more intestinal health issues during the post-weaning weeks. This may have caused them to expend more energy in the gut to adapt during the weaning period.

Corn processing can be beneficial for young calves because it increases starch digestibility in the rumen, stimulating rumen papillae growth. Studies have shown that the starch digestibility of steam-flaked corn is higher than that of whole corn grain in mature ruminants (97% compared to 84%). However, in this study, no difference in starch digestibility was observed at the 95% confidence interval. Nevertheless, the production of short-chain fatty acids (SCFA) and the digestibility of organic matter (OM) and dry matter (DM) were affected during the 12th week. The lower OM and DM digestibility in calves fed whole corn (WC) was likely due to reduced digestibility of crude protein (CP) and fat. The higher SCFA production in calves fed steam-flaked corn (FC) compared to WC can be explained by the greater digestibility of FC in the rumen and the passage of WC through the rumen. The site and rate of corn digestion in the rumen also affect fiber digestibility in dairy and beef cattle diets. However, in this study, due to the low fiber content in the starter feed (CS), no significant effect (at the 5% level) on the digestibility of neutral detergent fiber (NDF) and acid detergent fiber (ADF) was observed.

Chart 3. Effect of experimental treatments (HI-FC, HI-WC, LO-FC, and LO-WC) on short-chain fatty acid (SCFA) production.

The results indicate that the amount of milk replacer (MR) fed has a greater impact than corn processing in the starter concentrate (CS) on performance, fiber digestibility, and populations of fibrolytic bacteria in the rumen and feces. Bacterial assessments in the rumen and feces showed that due to higher CS intake in calves fed the low MR (LO) treatment, bacterial populations in the rumen and feces increased compared to the high MR (HI) treatment. The observed increase in microbial populations was consistent with improved fiber digestibility (NDF and ADF digestibility during weeks 5 and 8), increased body weight (BW) post-weaning, body weight, and physical measurements at 16 weeks of age. Insufficient microbial fermentation in the rumen caused by reduced CS intake when calves were fed higher volumes of milk or MR may have led to decreased fiber digestibility.

CONCLUSIONS:

High rates of milk replacer (MR) feeding reduce fiber digestibility both before and after weaning, as well as during the growth phase (weeks 5, 8, and 12). The average daily weight gain and pelvic width measurements before weaning were higher in calves fed the high (HI) feeding rate compared to low (LO), but these decreased after weaning, resulting in similar body weight and pelvic width at 16 weeks of age. Calves fed with the LO treatment had a higher proportion of fibrolytic bacteria in the rumen and feces compared to those fed with HI. Considering the combination of MR feeding rates and corn processing, both low and high MR feeding rates can be paired with either steam-flaked corn or whole corn in the calf starter, as corn processing had little or no effect on digestibility, intake, and calf growth.

REFERENCES :

https://doi.org/۱۰.۳۱۶۸/jds.۲۰۱۹-۱۷۳۷۲

 Van Niekerk, J., et al., Effect of amount of milk replacer fed and the processing of corn in starter on growth performance, nutrient digestibility, and rumen and fecal fibrolytic bacteria of dairy calves. Journal of Dairy Science, ۲۰۲۰. ۱۰۳(۳): p. ۲۱۸۶-۲۱۹۹.