Search

The objectives of this study were: (1) to evaluate feed efficiency indexes and their relationships with body measurements and blood and ruminal metabolites in the pre-weaning period; (2) to determine if such measurements can be used as feed-efficiency markers during the pre-weaning period. Holstein–Gyr heifer calves (n = 36), enrolled between 4 and 12 weeks of age, were classified into two residual feed intake (RFI) and residual body weight gain (RG) groups: high efficiency (HE; RFI, n = 10; and RG, n = 9), and low efficiency (LE; RFI, n = 10; and RG, n = 8). Calves were fed whole milk (6 L/day) and solid feed ad libitum. Body developments were measured weekly and feed intake (milk and solid feed) daily during the whole period. Blood samples were collected at 12 weeks of age and analyzed for glucose, insulin and β-hydroxybutyrate (BHB). Samples of ruminal content were collected on the same day and analyzed for pH, NH3-N, and volatile fatty acids (VFA). Among the growth characteristics, only the initial hip width differed between the RFI groups, and withers height differed between the RG groups. Concentration of BHB was greater and glucose: insulin ratios tended to be greater in LE-RG animals. Butyric acid proportions were similar among RFI groups, but tended to be greater for HE-RG than for LE-RG. Overall, correlation coefficients between RFI or RG and blood, rumen, or morphometric markers were low. Thus, it is unlikely that measurements of metabolic indicators, per se, will be useful in the early identification of more efficient animals. Understanding the underlying physiological basis for improved feed efficiency in dairy heifers requires further investigation.

ABSTRACT The study evaluated the average return on invested capital (ROIC) in function of the variations in the historical prices of beef cattle and the odds of return on that capital gain within the system of beef cattle fattening on a farm in the state of Minas Gerais, Brazil, from 2004 to 2007. To calculate the risk of ROIC, monthly data of beef cattle prices (BM&F) were used from July 1997 to December 2013, revised by the General Price Index of the Fundação Getúlio Vargas in December 2013. The corrected data were divided into five classes that correspond to the risk scenarios. In light of these classes, the observed frequencies and their respective probabilities were calculated. The cumulative and updated ROIC were -3.02 and 0.24%, respectively. The odds for obtaining returns above 8.4% (Brazilian Selic Rate) per year were median, corresponding to 32.0 and 34.94% for the calculation of operating profit (ROIC OP) and total profit (ROIC TP), respectively. The expected average annual return was 6.26 and 7.66% for ROIC OP and ROIC TP, respectively. The standard deviation and coefficient of variation showed a high risk of ROIC because the scale and extent of dispersion per unit of expected return were elevated in the accumulation period and the risk for 2013 was reduced according to the price of beef cattle. The expected risk of ROIC was considered high between 2004 and 2007 and average for 2013. The probability of return on capital invested in the intensification of fattening beef cattle is a function of the selling price of cattle and purchase of inputs, in which the high scenario ranching provides greater probability of getting a return above the bank interest rates.