The effects of diet and age on serum complement system activity in goat kids N. Castro a , F. Acosta c , T. Niño c , J. Vivas c , E. Quesada a , J. Capote b , A. Argüello a, ⁎ a Department of Animal Science, Las Palmas de Gran Canaria University, Arucas 35416, Spain b Canary Agronomic Science Institute, La Laguna, Tenerife, Spain c University Institute of Animal Health, Arucas 35413, Spain Received 21 March 2007; received in revised form 4 March 2008; accepted 13 March 2008 Abstract Thirty new born male kids were allotted into three groups to evaluate the effects of diet and age on complement system activity in serum. After the colostrum feeding period, the control group (C) received a commercial milk replacer; the CLA group received 20 g/kg milk replacer DM of conjugated linoleic acid; and the GMK group was fed with goat milk. The kids were fed colostrum for 2 days and then either milk replacer or goat milk from days 3 to 60. Blood samples were taken at 1, 10, 20, 30, 40, 50 and 60 days of age. The complement system activity was higher (P b 0.05) in the GMK group throughout the whole experiment through alternative pathway. C kids did not present complement activity at any time. CLA group complement activity was statistically higher than that of C kids from 30 to 60 days, through alternative pathways. In conclusion, the milk replacer formula should be reformulated because it did not induce any complement system activity in the first two months of life. © 2008 Elsevier B.V. All rights reserved. Keywords: Goat kid; CLA; Complement system; Diet 1. Introduction Conjugated linoleic acid (CLA) has broad biological activities such as anticarcinogenic (Ha et al., 1990), antidiabetic (Houseknecht et al., 1998), antiatherogenic (Nicolosi et al., 1993), and immunomodulatory (Sugano et al., 1998). Recently some papers have demonstrated the immunomodulatory role of CLA in different live- stock species (Bhattacharya et al., 2006; Suksombat et al., 2006; Castro et al., in press; JiHoun et al., 2007). Dietary immunomodulation, using orally active natural products, may become a strategy adopted by producers in the European Union and the United States as a means of maintaining current productivity levels after the withdrawal of antibiotics from livestock dietary for- mulations at growth-promoting levels. CLA is an authorized additive for pigs in European Union and in a few months' time it will be authorized for cattle and goats. The complement system plays a major role in the host defence mechanisms against infectious microbes, as it is involved both in specific and non-specific Available online at www.sciencedirect.com Livestock Science 119 (2008) 102 – 106 ⁎ Corresponding author. Fac. Veterinaria, Transmontaña s/n, 35413- Arucas, Spain. Tel.: +34 928451094; fax: +34 928451142. E-mail address: aarguello@dpat.ulpgc.es (A. Argüello). www.elsevier.com/locate/livsci 1871-1413/$ - see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.livsci.2008.03.004