A field trial was conducted to examine the effect of extended calving interval (CI) on production and profitability of high yielding cows (n = 937). First insemination was performed at 154 and 93 d postpartum (pp), for treatment and control primiparous cows, respectively, and at 124 and 71 d pp for treatment and control multiparous cows, respectively. During the first experimental lactation, average daily value-corrected milk (VCM) yield was 28.5 and 27.7 kg/d of CI for treatment (n = 131) and control (n = 133) primiparous cows, respectively. No significant difference in average daily VCM yield (33.0 and 32.8 kg/d of CI) was found between treatment (n = 271) and control (n = 215) multiparous cows . In the first 150 d of the subsequent lactation, there were significant differences in milk and VCM production in favor of the treatment primiparous cows (41.4 vs. 39.7 kg of VCM/d) but no significant differences in the production of multiparous cows. Primiparous and multiparous cows with extended lactations were more profitable. During the first experimental lactation, there were advantages of $0.19 and $0.12/d of CI in the net returns for primiparous cows and multiparous cows with longer CI, respectively. When the economic analysis included the first experimental lactation plus the first 150 d of the subsequent one, the net return per day of CI was higher for cows with an extended voluntary waiting period: $0.21/d and $0.16/d for primiparous and multiparous cows, respectively. A delay of 60 d with respect to the usual voluntary waiting period in the beginning of inseminations of high yielding cows has economic advantages and allows the farmer an option for decisions regarding individual cows.

The objectives of this study were to identify and evaluate production and environmental factors that influence milk urea (MU) in Israeli dairy herds, to analyze the relationships between MU concentration and nutritional variables, and to examine a possible association between MU and pregnancy rate (PR). Production and environmental data were obtained from the Israeli Dairy Herd Improvement (DHI) Center (n = 1,279,600). Programmed total mixed rations (feeds and quantities) on milk-test day were collected from 42 dairy herds. Data on 36,073 cows that were inseminated close to milk-test day and pregnancy diagnosis results were obtained from the DHI data bank. Highly significant positive relationships were found between MU concentration and milk yield and fat percentage; relationships between MU and milk total protein percentage and somatic cell count were negative. Milk urea levels were higher during the summer months and were higher for adult cows. These levels increased as lactation progressed. Milk urea was positively associated with dietary levels of crude protein, ruminal digestible protein, and neutral detergent fiber contents; it was negatively associated with ration energy and nonstructural carbohydrate contents. Significant influences of specific feeds on MU were detected. A significant negative association was found between MU level and PR. Least squares means for PR for cows in the lowest and highest MU quartiles were 38.4 and 36.1%, respectively. Increasing levels of MU were negatively related to reproductive performance of dairy cows, but the risk of nonpregnancy caused by high levels of MU was lower than reported in previous studies.

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JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. Center for Latin American Studies at the University of Miami is collaborating with JSTOR to digitize, preserve and extend access to Journal of Interamerican Studies and World Affairs. his article examines whether the free-market, open-economy model adopted by Chile's civilian, democratically elected administrationsof Patricio Aylwin (after March 1990) and Eduardo Frei (after March 1994)has affected the country's distribution of income and degree of poverty and, if so, how. The free-market model was inherited from the military regime headed by General Pinochet (1973-1990) and adopted by his civilian successors almost without modification despite the fact that the post-1990 administrations were explicitly committed to making alleviation of poverty and reduction of inequalities in income a top priority. The article examines the extent to which the determinants of poverty and inequality have changed (if, indeed, they have changed at all) since the end of the military regime in 1990and if so, why. After brief discussions of (a) the nature of the problem and (b) its historical roots, the article will look at two important factors in this regard: the role that the tightening labor market played in the economy, especially after the economic recovery which began in the mid-1980s, and the role that was played by the appreciation of the Chilean currency (the peso), both of which have much to say about the impact of neoliberal economics. The effects of democratic politics are apparent after 1990 when the middle sectors experienced a substantial improvement in their share of income. This development relates to the nature of government expenditures, and to social expenditures in particular. The final section summarizes the article's conclusions.' David E.ost observers are in general agreement that the Chilean economy is the most successful in Latin America. Output, led by exports and investment (domestic and foreign), has been growing at an average rate of over 6% per year since the mid-1980s, with forecasts of 7.5% growth for 1995 and 6.5% for 1996, respectively (see EIU, 1994; El Mercurio, 1995 a-h). Inflation is falling gradually and is expected, by the end of the 1990s, to reach the levels of the Organization for Economic Cooperation and Development (OECD). Domestic savings are substantial: the privately run pension funds have accumulated assets amounting to about 50% of the gross domestic product (GDP). External accounts are also healthy.Exports have been increasing at a rate of more than 10% per year ever since the mid-1980s. The economy is becoming increasingly more open: external trade (exports plus imports), as a share of GDP, rose from 51% in 1987, to 69% in 1990, and 78% in 1994. Th...