Performance and metabolism of dairy calves fed starter feed containing citrus pulp as a replacement for corn

The aim of the present study was to evaluate the effect of replacing corn grain with citrus pulp (CSP) in the starter concentrate on performance and metabolism of dairy calves. Twenty-four individually housed Holstein calves were blocked according to birth date and weight and fed one of the following concentrates: (1) concentrate containing 64% corn and 0% CSP (0CSP); (2) concentrate containing 32% corn and 32% CSP (32CSP); and (3) concentrate containing 0% corn and 64% CSP (64CSP). Animals were fed 4 L of milk replacer daily (20% crude protein, 16% ether extract) divided in two meals (at 0700 hours and 1800 hours). The starter feed and water were provided ad libitum. Starter intake and faecal score were monitored daily. Bodyweight and measurements (withers height, hip width and heart girth) were recorded weekly. Blood samples were collected weekly, and ruminal fluid samples at 4, 6 and 8 weeks of age, 2 h after the morning feeding. After 8 weeks, animals were harvested to evaluate the development of the proximal digestive tract. Concentrate composition had no effect (P>0.05) on concentrate intake, weight gain, bodyweight, body measurements, and faecal score. However, there was a lower concentration of ruminal butyrate (P<0.05) in animals receiving 0CSP than in those fed the starter containing CSP. The 0CSP concentrate resulted in a lower (P < 0.05) total weight of the proximal digestive tract, weight of the reticulum-rumen and weight of the omasum than did the other concentrates. The length of the rumen papillae was the greatest (P < 0.05) in 32CSP-fed animals. However, papillae area in animals fed 32CSP concentrate was larger (P < 0.05) than that in 0CSP- and 64CSP-fed animals, with no difference observed between these latter two treatments. However, 0CSP-fed animals showed a higher proportion of abomasum than did the animals fed 32CSP and 64CSP concentrates. The replacement of 50% or 100% of corn by CSP in the starter feed of dairy calves did not affect performance and probably contributed to the better development of the proximal digestive tract.