Dairy Sci May 2011 Vol. 94, No. 5, pp. 2545-2556 The Effects of Early Weaning on Innate Immune Responses of Holstein Calves L.E. Hulbert*, C. Cobb, J. Carroll, M. Ballou The objectives of this study were to compare innate immune responses of calves weaned early (EW; n = 23; weaned at23.7 ± 2.3 d of age) with those of conventionally weaned calves (CW; n = 22; weaned at 44.7 ± 2.3 d of age). All calves were fed 3.8 L of colostrums within 12h of birth and were subsequently fed milk replacer twice daily. The weaning process began by withdrawal of the afternoon milk-replacer feeding. Milk was fully withdrawn, and the calf was considered completely weaned when it consumed 900 g of calf starter as-fed for 2 consecutive days. Blood samples were collected from all calves at 24, 27, 31, 45, 48, 52, and 66 ± 2.3 d of age. Early weaned calves took a variable amount of time to completely wean from milk replacer; therefore, data were also analyzed by comparing calves grouped by latency to completely weaned (fast = 1 to 5 d; intermediate = 6 to 8 d; slow = 15 to 17 d). Slow-EW calves weighed less than either the fast- or intermediate-EW calves before initiating weaning. At 27 d of age, circulating neutrophils were greater among EW calves than CW calves. Moreover, fast-EW calves had lower neutrophils: mononuclear cell ratios at 45 d of age than other EW calves. Slow-EW calves had lower TNF-α concentrations from whole blood stimulated with endotoxin at27 and 31 d of age compared with fast- and intermediate - EW calves. All EW calves had decreased neutrophils L-selectin at d 27 and increased neutrophils L – selectin at 31 d of age. At 31 d of age, neutrophilsβ2 - integrin was the greatest among the fast-EW calves. All EW calves had decreased neutrophils oxidative burst at 27 and 31 d of age. Three days after CW calves were weaned they had higher neutrophils, hematocrit percentages, and circulating cortisol than EW calves. In addition, 3 d after CW calves were weaned they, had decreased neutrophils oxidative burst responses to Escherichia coli. Weaning, irrespective of age, suppressed many innate immune responses. In addition, early weaning transiently suppressed L-selectin expression on neutrophils; however, the immunological significance in the context of the resistance to disease is unknown because EW calves likely had greater protection from passively derived immunoglobulins when they were weaned. Finally, calves with lower BW around 24 d of age may not be suitable for early weaning programs as evident in the suppressed secretion of TNF-α from whole blood cultures during the week following the initiation of weaning. *Department of Animal and Food Science, Texas Tech University, Lubbock, TX 79409
Posted on: Sun, 08 Sep 2013 00:04:00 +0000
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