The physical form of starter (finely ground versus pelleted) and alfalfa hay (chopped versus pelleted) in Holstein dairy calves: Effects on growth performance, feeding behaviour, ruminal fermentation, and urinary purine derivatives

This study evaluated the effects of the physical form of the starter [finely ground starter (GS) vs. pelleted starter (PS)] and physical form of alfalfa hay [chopped alfalfa hay (CAH) vs. pelleted alfalfa hay (PAH)] on growth performance, digestibility, ruminal fermentation, and urinary purine derivatives. Forty 3-day-old male Holstein calves (average BW of 39.7 kg) were assigned in a completely randomized design with a 2 x 2 factorial arrangement of the treatments as follows: (1) ground starter with chopped alfalfa hay (GS-CAH), (2) ground starter with pelleted alfalfa hay (GS-PAH), (3) pelleted starter with chopped alfalfa hay (PS-CAH), and (4) pelleted starter with pelleted alfalfa hay (PS-PAH). The geometric mean particle size for the experimental starter diets were 0.61, 0.76, 2.17, and 2.31 mm for GS-CAH, GS-PAH, PS-CAH, and PS-PAH, respectively. All calves were weaned on d 53 of age and remained in the study until d 73 of age for the final measurements. Results showed that during the pre-weaning period, calves receiving the PS diets had greater starter intake (479 vs. 322 g/d; P = 0.01) and average daily gain (639 vs. 509 g/d; P < 0.01) than those fed with the GS diets regardless of the physical form of the alfalfa hay. Further, the PS diets increased the weaning and final body weights (P <= 0.01), heart girth at weaning (P = 0.05) and final body length (P = 0.02) compared with the GS groups. Moreover, non-fibre carbohydrate (P = 0.05) and organic matter digestibility (a tendency; P = 0.08), urinary allantoin (P = 0.04), and total purine derivatives (14.9 vs. 16.7 mmol/d for GS and PS diets, respectively; P = 0.05) increased in the PS diets compared to the GS diets. However, urinary nitrogen excretion was higher (P = 0.03) in the GS compared with the PS diets, which indicated lower nitrogen efficiency. Yet, no difference was found in the ruminal fermentation profile when calves were fed with different starter physical forms. Regarding the alfalfa hay physical form, the results showed that the growth performance and ruminal fermentation were not influenced by the different physical forms of AH. However, feeding calves with PAH diets reduced the neutral detergent fibre digestibility (P = 0.05) and tended to reduce the urinary allantoin concentration (P = 0.06) compared with the CAH groups. There was no interaction between the physical form of the starters and alfalfa hay for the starter intake, growth performance, ruminal fermentation pattern, and urinary PD excretion. It could be concluded that under the condition of the current study, pelleted alfalfa hay is not recommendable because of being associated with lower fibre digestibility and reduced rumen microbial growth. Regarding the starter physical form, the pel- leted starter was more favourable than the ground starter form in terms of growth performance and nitrogen efficiency in dairy calves. Furthermore, the pelleted starter form would possibly have other benefits when concurrently fed with chopped alfalfa hay rather than fed with pelleted alfalfa hay in dairy calf diet.

Automated summary

The study evaluated the effects of different physical forms of starter and alfalfa hay on growth performance, digestibility, ruminal fermentation, and urinary purine derivatives in Holstein calves. Pelleted starter led to higher starter intake, average daily gain, and final body weights compared to ground starter, while also increasing digestibility and purine derivative excretion. Pelleted alfalfa hay was associated with lower fibre digestibility and reduced microbial growth in the rumen compared to chopped alfalfa hay.