Biochemical and haematological measurements were used to identify constraints on productivity in beef cattle. One hundred and twelve Aberdeen Angus and Criollo Argentino females including lactating cows, dry non-pregnant cows and heifers were selected. Blood samples were taken in the middle of summer and autumn. Serum was analysed for haemoglobin, PCV, glucose, albumin, urea, creatinine, Ca, P, Mg, Fe, Cu, ALP, AST, ALT, CK, LDH, Cl-, Na and K content. Globulin was calculated by taking the difference between total protein and albumin. Percentages of all cattle that had metabolite levels outside reference ranges were: 15% (glucose), 8% (globulin), 5% (urea), 96% (Ca), 50% (P), 12% (Mg), 20% (Na), 5% (K), 24% (Cl), 18% (Fe), 5% (Cu) and 85% (CK). These results indicate with some certainty that dietary protein was not limiting. Body condition score loss was detected only in lactating cows. There were a few animals that could have presented chronic inflammatory disease. Phosphorus could be an important potential constraint on fertility, although the presence of symptoms of hypophosphataemia was not observed. The study also demonstrates the absence of anaemia or liver disease. Breed, seasonal and physiological state differences in some blood metabolites could be attributed to one or more of the following factors: chemical composition of the feed ingested, environmental temperature, nutrient content of the forage, animal age and cattle foraging experience. The study provides a basis for implementing helpful adjustments in current cattle management practices so as to alleviate the constraints on productivity, provided that these practices are profitable.
