MATERNAL BEHAVIOR IN SHEEP PRODUCTION: EFFECTS ON LAMB PERFORMANCE AND ECONOMIC INDICATORS
This study assessed the economic impact of inadequate maternal behavior of sheep, between birth and first suck of the lambs in a commercial flock of meat sheep. We observed 222 pregnant Santa Ines ewes and their 327 lambs. Behavioral observations were performed, by direct method with focal samplings every five minutes. Maternal activities considered negative were preventing suck, withdrawing and butting. Statistical analyses were conducted by multiple linear and logistic regression models, using functions PROC REG and PROG LOGISTIC, of the software SAS 9.3. In economic analysis we simulated the ratios for production costs and revenues in case of manifestation or not of negative maternal activities. We investigated connections between maternal behavior, incidence of dystocia, need for artificial rearing, birth weight, pre-weaning mortality, prolificacy rate and weaning weight. Negative maternal behaviors were displayed by 19.37% of the ewes. Lamb weaning weight was influenced by birth weight (P<0.001) and litter size (P<0.01), but not by maternal behavior, artificial rearing or dystocia. Pre-weaning mortality was probably affected by maternal behavior (P=0.10) and litter size (P<0.05), but not by artificial rearing. Lambs from dams which did not display negative behavior had 82% higher chances of surviving until weaning. Probability of surviving until weaning reduced 50% with the increase of each additional lamb in the litter. Maternal behavior was significantly influenced by birth weight (P<0.01) and dystocia (P<0.05), but not by litter size. Chances of ewes do not display negative maternal behavior raised 105% for each 1 kg increase on birth weight of lambs. On the other hand, dystocia incidence increased in 79% the chances of negative behavior to occur. In the studied flock, dystocia incidence was not related to lamb birth weight. Economic analysis demonstrated that production cost would be higher for lambs whose mothers displayed negative behaviors, mainly due to greater need for artificial rearing, while sale income would be similar between groups. Negative maternal behavior was related to increases in pre-weaning mortality rate and need of artificial rearing. Thus, negative maternal behavior resulted in economic impact, represented by the increase of production cost and the decrease in 7% of revenues. These results are important to guide viability evaluation of investments that aim to improve maternal-offspring relation in sheep. Reasons for displays of negative behavior by important portions of that flock are not clearly elucidated, although data suggest relations with higher prolificacy and dystocia.
Keywords: economic evaluation, production cost, ewe