Effects of sire genotype on lamb performance at weaning in extensive sheep systems.

A low finishing weight and poor carcass characteristics are major causes of lower incomes in extensive sheep flocks; however, the use of terminal sire crossbreeding would improve lamb performance and carcass traits under these conditions. The aim of this study was to evaluate sire breed effects on the performance of lambs born to Corriedale ewes in extensive sheep systems in Western Patagonia. A total of 10 Corriedale, 10 Dorset, nine Suffolk and seven Texel sires, 16 of which were under a genetic recorded scheme and 20 selected from flocks not participating in genetic improvement programmes, were used across six commercial farms for 2 successive years. Data were collected from 685 lambs of the four resulting genotypes. Overall, Corriedale lambs were 0.47 kg lighter at birth than crossbred lambs (P0.05). Carcass conformation was higher in Texel sired lambs compared with Corriedale lambs (P<0.05), with Dorset and Suffolk sired lambs being intermediate. Crossbred lambs showed a greater (P<0.001) eye muscle than Corriedale. Commercial cuts were affected by sire breed, as a result of the Corriedale lambs being smaller and having lighter carcass than crossbred lambs. Significant improvement in lamb weights at weaning and carcass traits could be expected when using a terminal sire on Corriedale ewes in Western Patagonia. However, no advantages were detected with the use of recorded sires under these production systems.

Determination of the country of origin of farm-raised shrimp (family penaeide) using trace metal profiling and multivariate statistics.

The role of Customs and Border Protection on shrimp importations into the United States is discussed. The focus of this work is to present evidence that the comparison of trace metal data from an imported shrimp sample to an authentic reference database using multivariate statistics produces an accurate geographic location of the sample. The authentic reference database includes data from more than 100 sampling sites spread over eight countries along with the accuracy of each site relative to its known geographic origin. Potential sources of bioaccumulation are briefly discussed; however, it is beyond the scope of this work to provide scientific verification of the mechanism for trace metal uptake. Three examples of imported shrimp are provided for demonstrating the exact procedure for determining their true countries of origin.

Molecular analysis of Salmonella enteritidis isolates from the Caribbean by pulsed-field gel electrophoresis.

Using pulsed-field gel electrophoresis (PFGE), between 1987 and 1996 we analyzed Salmonella enteritidis isolates from gastroenteritis cases in four Caribbean countries: Barbados, Saint Kitts and Nevis, Saint Lucia, and Trinidad and Tobago. We also determined the resistance of the isolates to 12 antimicrobial agents. Of the 129 isolates of S. enteritidis available for testing, DNA digested by XbaI revealed 13 distinctive PFGE patterns. The most prevalent XbaI PFGE patterns were group 1 (88 of 129 isolates, 68.2%) and group 2 (26 of 129, 20.2%). The patterns found among S. enteritidis isolates correlated with the geographical origin of the isolates. Of the 28 isolates from Barbados, 20 of them (71.4%) belonged to XbaI PFGE group 2, and of the 93 isolates from Trinidad and Tobago, 78 of them (83.9%) belonged to group 1. SpeI digestion of S. enteritidis genome was not as discriminatory as XbaI. Overall, of the 129 isolates, 67 of them (51.9%) exhibited resistance to one or more of the 12 antimicrobial agents that we tested. The prevalence of resistance was 53.8% for the S. enteritidis isolates tested from Trinidad and Tobago, 50.0% for those from Barbados, 28.6% for those from Saint Lucia, and 100.0% for one isolate from the island of Saint Kitts. Resistance was highest to triple sulfur (59 of 129 isolates, 45.7%), followed by furadantoin (10 of 129, 7.8%), ampicillin (7 of 129, 5.4%), and carbamycin (5 of 129, 3.9%).

[The dynamics of contraceptive use in Mexico]. / Dinamica del uso de metodos anticonceptivos en Mexico.

PIP: The authors identify some variables associated with the adoption and continuation of contraception in Mexico. The focus is on determinants of choice of different methods, as well as the impact of selected socioeconomic and demographic factors and the influence of institutions providing family planning services on choice of method.^ieng

[Population policy: new alternatives or old premises for 1989 to 1994?]. / Politica de poblacion. Nuevas alternativas o viejas premisas para 1989 a 1994?

PIP: The notion that government intervention is essential for establishing a rational course of population development has persisted throughout the evolution of population policy in Mexico and has been reflected in the search for mechanisms to assure appearance of the desired demographic profile. Political will is, however, constrained by the requirement that policy and programs respect human rights, and by the considerable inertia in population dynamics resulting from previous conditions. Examination of population policies and programs announced by Mexico since 1977 shows more similarities than differences. All three programs state that the general objective is to raise the level of living of the population. Modifications have occurred in the programmatic instruments intended to carry out policy. Family planning appeared as the central focus of the first program, but by the third National Population Program in 1980-84, it had become a subprogram and the central focus was on the relation between population and development. Other needs initially relegated to secondary status, such as mortality reduction in specific groups, have assumed greater importance. The belief persists that slowing population growth will favorably affect national development and well being. But recent history demonstrates that living conditions of the population obey the logic of the economic development model and distribution of wealth.^ieng

[The preoccupation with goals]. / La preocupacion por las metas

PIP: Contraception has become the principle factor in Mexico's fertility drop during the past 15 years. Between 1976-82, 47.7% of married women in the population used contraception. The national policy established a growth rate of 1.9% for 1988 implying a global fertility rate of 3.1, with a 58% utilization rate; results of the 1987 Demographic and Health Survey demonstrated that Mexico achieved a fertility rate of 3.8 and a 52.7% utilization rate. In Mexico fertility is perceived as the key variable that can change the demographic profile of the country with family planning as the means of changing people's value systems and controlling the growth of the population. In Mexico, regional characteristics determine the number of children couples decide to have. There are 4 groups of behavior: 1) the Northeast (63%) and Northwest (70%) which have accurate statistical data, share borders with the US and are economically developed; 2) the North Zone of the Isthmus of Tehuantepec and the 3 regions on the coast (Gulf 54%; South Center 51%; and Center 55%); 3) the North Center (46%); and 4) the Southeastern region (32%) with the lowest prevalence rates in the country. There is a need to modify the demographic rationale of determining targets towards a more social/historical perspective that acknowledges regional differences in a country and allows new interest in understanding the reproductive behavior of women and couples.^ieng