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 × 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
