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Eighteen sows were allocated to a 2 x 3 randomized incomplete block design with 2 stages of lactation (early and peak) and 3 protein levels: deficient (D), adequate (A), or in excess (E) of lactation requirement. In early lactation, compared with A, sows fed E had lower (P = 0.05) piglet growth rate and sows fed D or E had lower (P<0.05) casein yield. In early lactation, piglet growth rate and milk protein and casein yield increased from D to A and decreased from A to E (quadratic, P = 0.095, P < 0.05, and P<0.01, respectively). Protein intake did not affect CAT-1, ASCT1, ATB0,+ mRNA abundance, or CAT-1 protein level. Overall, CAT-2B mRNA abundance decreased linearly with increasing protein intake (P<0.05). Compared with A, E decreased CAT-2B mRNA abundance (P<0.05). Compared with early lactation, peak lactation did not increase CAT-1 mRNA abundance or relative CAT-1 protein content, but increased abundance of ASCT1 and ATB0,+ mRNA (P<0.01). Mammary CAT-2B appears to be adaptively regulated in vivo at the transcription level, whereas ASCT1 and ATB0,+ mRNA abundances are associated only with stage of lactation.
Neither protein intake nor stage of lactation affects porcine mammary CAT-1 gene expression in vivo.
J Pérez Laspiur, JL Burton, PSD Weber, J Moore, RN Kirkwood, and NL Trottier, 2009, Journal of Nutrition, 139: 1677–1684.
