Transition milk feeding to calves after the first co- lostrum feed has been shown to reduce the inci- dence of respira- tory symptoms.


excretion was greatest in calves fed UHT. Where possible, the recommendation is to feed whole milk that has been hygien- ically harvested and handled to calves without further heat treatments or acidifications. Various high-quality milk replacers are available, and it is rec- ommended that these only contain milk-source proteins. Studies have shown that milk replacers with oligosaccharides that have high bioactive potential can help establish benefi- cial gut microbiota (Badman et al., 2019). Feeding man- nan-oligosaccharides (for example, Bio-Mos and Actigen, Alltech Inc.) to young calves supports the development of a well-functioning intestinal wall, good local immunity and im- proved feed efficiency and provides the ability to bind patho- gens such as Salmonella enterica and Escherichia coli (Spring et al., 2015). Actigen added to the milk feed daily has been shown to aid the development of gut immunity, de- crease diarrhoeal disease severity, improve feed efficiency and improve weight gain in young calves (Heinrichs et al., 2013). A meta-analysis of 20 studies of Bio-Mos in whole milk, waste milk or milk replacers has proven consistent improve- ments in calf weight gain and shown an average increase of 64 g in daily gain, resulting in a 3.6 kg higher weaning weight compared with unsupplemented calves (Berge, 2016).


Take care of the gut microbiota The rumen is colonised with various facultative aerobic bac- teria within a few hours after birth. Strict anaerobic bacteria (such as cellulolytic and proteolytic bacteria) establish within the first two weeks of life. The rumen, initially colonised by microbial flora derived from milk, increases in diversity with the consumption of starter feed (Malmuthuge et al., 2013). A good-quality starter grain specifically formulated for calves should be introduced during the first days of life. Palatability is important for intakes, and calves tend to prefer and per- form better on textured muesli-type starter feed composed of pellets and whole grain. Ruminal papillae development is enhanced through the volatile fatty acids produced as a


result of starter feed consumption. A starter should prevent keratin build-up on the ruminal papillae, which can reduce their absorptive capacity. The textured starter with whole grains can provide physical abrasiveness that prevents the keratin build-up. Pelleted and fine-ground starters give rapid starch fermentation, giving rise to ruminal acidosis, and do not provide enough abrasiveness to prevent keratin build-up on the papillae. This may reduce feed intake and weight gain compared with textured starters. The addition of dietary forage to starter diets can positively influence digestion and performance in developing calves (Moeini et al., 2017). Forage sources are an essential buffer for the gastrointestinal tract via the fibre matrix and stimulate rumination and salivation. Forages increase the ruminal pH and are, therefore, important alongside all-pelleted or finely ground grain. Furthermore, forages may aid in preventing keratin build-up through their abrasive structure and pro- vide welfare benefits for the calf. Giving drinking water to neonatal calves has also been shown to positively affect the gut microbiota and has been associated with higher weight gain and improved fibre digestibility and feed efficiency ( Wickramasinghe et al., 2019). Metaphylactic or prophylactic inclusion of antimicrobials in the animal feed disrupts the essential healthy gut microbiota and increases antimicrobial resistance. Furthermore, indi- vidual injectable antibiotic treatments can lead to increased diarrhoeal disease days and depressed grain intake and weight gain (Berge et al., 2009b). Thus, the long-term costs of antibiotic use far exceed the price of the drug itself. The future performance of the herd is laid down in the gut of the young heifers; take care of the gut microbiota, and they will work together for the heifer’s growth and health. The Alltech Gut Health programme can assist dairy farmers in addressing enteric challenges and optimising heifer health and growth.


References available on request. ▶ DAIRY GLOBAL | Volume 8, No. 3, 2021 29


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