Breeding objectives of Brangus cattle in Brazil.

Our goal was to define a breeding objective for Brangus beef cattle in Brazil. Bioeconomic models were produced and used to estimate economic values (EVs). The scenarios simulated were typical full-cycle beef production systems that are used in tropical and subtropical regions. The breeding objective contained pregnancy rate (PR), warm carcass weight (WCW), mature cow weight (MCW), number of nematode eggs per gram of faeces (EPG) and tick count (TICK). Two models were used in series to estimate the EV. A deterministic model was used to simulate effects of PR, WCW and MCW on profitability with a constant parasite load. Subsequently, stochastic models were used to estimate economic values for TICK and EPG as consequences of their environmental effects on weight gains, mortality and health costs. The EV of PR, WCW, MCW, EPG and TICK, was US$1.59, US$2.11, -US$0.24, -US$5.35 and -US$20.88, respectively. Results indicate positive emphasis should be placed on PR (12.49%) and WCW (65.07%) with negative emphasis on MCW (13.92%), EPG (2.77%) and TICK (5.75%). In comparison with the indexes usually used, these results suggest a reformulation in the selection indexes of the beef production system in tropical and subtropical regions in order to obtain greater profitability.

In vitro effect of condensed tannin extract from acacia (Acacia mearnsii) on gastrointestinal nematodes of sheep.

The aim of this study was to determine the inhibitory effects of condensed tannin extract from acacia on the feeding of first-stage larvae (L1) of Haemonchus contortus, Trichostrongylus vitrinus and Teladorsagia circumcincta. The experiment was developed such that the inhibition of feeding for each of the nematode species could be evaluated. L1 recovered from fecal samples from a donor with monospecific infection was incubated in several dilutions of acacia extract (AE). The LD50 was determined for the three species of nematodes. Polyethylene glycol (PEG) was added to all dilutions of AE to inactivate the condensed tannins (CT) from acacia and to confirm their effects on L1. The impact of CT on larval feeding inhibition was detected for all the species of nematodes (H. contortus, T. colubriformis and T. circumcincta). There were differences between the aqueouswater control and CT treated groups (P < 0.01). The LD50 values were 0.043, 0.038 and 0.050 (SE = 0.0024), for H. contortus, T. vitrinus and T. circumcincta, respectively. A difference was detected between the AE and AE + PEG treatments (P < 0.01). Analysis of these results suggested that the direct effect of CT on L1 of the nematodes studied could be used as an alternative means for controlling nematodes in sheep.