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Blood parameters of 18 Nellore steers submitted to high concentrate diet in two sequential feeding regimes (Phase 1: restriction and Phase 2: ad libitum feed) were evaluated. In the first phase, steers were fed during 56 days in three intake levels of dry matter (ad libitum, 75 g dry matter (DM)/kg metabolic body weight (BW0.75) or 60 g DM/kg BW0.75. In the second phase, from the 57th day of confinement, animals fed 60 g DM/kg BW0.75 and 75 g DM/kg BW0.75 received feed ad libitum until the 136th day. In the 8th, 27th, 55th (first phase), 71st, 84th, 112th and 132nd (second phase day of experimental period, blood samples were collected and insulin-like growth factor I (IGF-I), triiodothyronine (T3), thyroxine (T4), glucose, plasma ureic nitrogen (PUN) and total protein (TP) were determined. In the first phase IGF-I, T4, glucose and total protein concentration was not different among treatments (P>0.05) and there was no interaction between treatment and time (P>0.05). There was an interaction among treatments and time on T3 and plasma ureic nitrogen (P0.05). For plasma ureic nitrogen concentration there was an interaction among treatments and time (P=0.02). Lower levels of diet intake can be used to improve animal performance in feedlot.

El objetivo del presente trabajo fue conocer los valores de referencia de tetraiodotironina (T4), principal hormona secretada por la glándula tiroides en condiciones normales e indicador de la concentración de yodo en el ambiente, en bovinos hembra bajo alimentación pastoril del NO de la provincia de La Pampa. Se obtuvieron muestras sanguíneas de 118 bovinos, distribuidos en seis esta blecimientos de los departamentos Maracó, Quemú Quemú, Rancul y Chapaleufú, zonas con características propias y con diferentes tipos de vegetación. El valor de T4 más bajo hallado se encontró en los animales del Departamento Rancul, y está en relación directa con las zonas fisiográficas muestreadas.

ABSTRACT The objective of the present study was to assess the effect of dietary supplementation of Omega-3 plus on some the physiological and biochemical traits in growing Baladi goats under hot summer conditions. Thirty-four growing male goats (4-5 months old) were randomly divided into two equal groups. Animals in group 1 were fed a concentrate feed mixture (CFM), which was the control group. Goats in group 2 (the experimental group) were offered Omega-3 plus (1,000 mg/animal day-1) (30% fish oil, containing 18% eicosapentaenoic acid and 12% docosahexaenoic acid + 100 mg wheat germ oil (0.22% tocopherols)) daily in addition to the basal diet for four months (the experimental period) during the hot summer season. Body weight (BW) changes of both groups were recorded monthly during the experiment. Blood samples were collected monthly, and total protein, immunoglobulin G (IgG), total cholesterol, triglycerides, liver enzymes (AST and ALT), blood urea nitrogen, serum creatinine, and thyroid hormones (T3 and T4) were estimated. A significant increase in the live BW of growing goats was recorded as a result of dietary supplementation of Omega-3 plus. Total protein, IgG, and T3 levels were higher than those obtained with control. In contrast, total cholesterol, triglycerides, urea, ALT, and AST levels were significantly reduced. The serum concentration of creatinine and T4 levels was indistinguishable from those of control. Addition of Omega-3 plus as a dietary supplement to growing goats under hot summer conditions increases their daily weight gain and improves their general physiological and biochemical status by decreasing total cholesterol, triglycerides, urea, ALT, and AST. It is thus suggested that Omega-3 plus should be used as a supplement in the growth period of goats.

Congenital hypothyroidism (CH) is one of the most common preventable causes of mental retardation. Newborn screening and thyroid therapy started within 2 weeks of age can normalize the cognitive and motor impairment caused by lack of thyroid hormone during the early postnatal phase of brain development. The availability of assays to determine thyroxin (T4) and thyroid stimulating hormone has allowed the establishment of newborn screening programs for CH. The Immunoassay Center (Cuba) developed the T4 Neonatal UMELISA(r) to determine neonatal T4 levels in dried blood on filter paper using 5 mm discs of samples, standards and controls. The number of diseases which can be diagnosed in Neonatal Screening Programs has increased, so it is necessary to make the maximum use of blood samples collected on filter paper. This work shows the standardization of the T4 Neonatal UMELISA(r) modified in order to use 3 mm discs. The assay was completed in 3 1/2 hours, with a measuring range of 25-400 nmol/L. The intra- and inter-assay coefficients of variation (CV) were 6-10 % and 7-12 % respectively, depending on the T4 concentrations. The recovery ranged from 91.8-115.1 %. The modified assay showed high Pearson correlation (r = 0.877) and concordance correlation (?c = 0.867) with the T4 Neonatal UMELISA(r). The performed modifications do not affect the sensitivity, precision and accuracy of the assay, permitting a more rational use of newborn blood samples and the possibility to increase the number of diseases included in the newborn screening programs.