The effect of a chronic stressor, lameness, on detailed sexual behaviour and hormonal profiles in milk and plasma of dairy cattle

The objectives of the present study were to quantify the effects of a biological chronic stressor (lameness) on the duration and frequency of different oestrous behaviours in parallel with milk hormone profiles. Dairy cows 51.8 +/- 1.4 days postpartum (n = 59), including 18 non-lame control cows, were scored for lameness and closely observed for signs of oestrus having had their follicular phases synchronized by administration of gonadotrophin-releasing-hormone (GnRH) followed by prostaglandin F(2alpha) (PG) 7 days later. Lameness shortened the period when herd-mates attempted to mount the lame cows (1.83 +/- 0.69 h vs 5.20 +/- 1.53 h; p = 0.042) but did not affect the overall duration of total behaviours (lame 12.3 +/- 1.3 h vs non-lame 15.2 +/- 1.3 h). Lameness also lowered the intensity of oestrus [1417 +/- 206 points (n = 18) vs 2260 +/- 307 points (n = 15); p = 0.029]. Throughout the synchronized oestrous period, lame cows mounted the rear of herd-mates less frequently (p = 0.020) and tended to chin rest less (p = 0.075). Around the period of maximum oestrous intensity, lameness also diminished the proportion of cows mounting the rear of another cow and chin resting (p = 0.048, p = 0.037, respectively). Furthermore, lame cows had lower progesterone values during the 6 days before oestrous (p < or = 0.05). Fewer lame cows were observed in oestrus following PG (non-lame 83%, lame 53%; p = 0.030); however, if prior progesterone concentrations were elevated, lame cows were just as likely to be observed in oestrus. In conclusion, following endogenous progesterone exposure, lameness shortens the period when herd-mates attempt to mount lame cows but does not affect the incidence of oestrous. However, lame cows are mounted less frequently and express oestrus of lower intensity. This is associated with lower progesterone prior to oestrus but not with abnormal oestradiol or cortisol profiles in daily milk samples.

Health-related aspects of integrated pest management.

Basic concepts and philosophy of integrated pest management are presented in order to dispel several misconceptions and to provide the necessary background information for discussion of its relationship to the health-related effects of pesticide use. Implications for human health of current pesticide practices in Central America are examined to illustrate major problems associated with the injudicious use of insecticides, i.e., human pesticide poisonings, development of insect resistance, and persistence in the environment. Mitigation of these problems would ideally be achieved through the efforts and cooperation of a multidisciplinary team of scientists and technical people in the medical and agricultural sciences. The dilemma associated with the development of integrated pest control systems in developing countries is discussed. The FAO/UNEP Global Programme was reviewed.