ABSTRACT.- This study identified the relationship between energy balance and some blood metabolites in primiparous dairy cows with different calving conception interval. Twenty primiparous Holstein-Friesian dairy cows were grouped according to the interval (days) from calving to conception into early-conception (early-c; 150 days) group; and evaluated on day-7 prior to parturition, and days 28, 56 and 90 postpartum. All groups presented positive energy balance, serum concentrations of HDL, urea-N and progesterone with no difference on days 28 and 56 of lactation.

ABSTRACT.- Reproduction is crucial in the efficiency of grazing-based beef production systems. There are different ways to improve reproductive indices in cattle, such as through herd management, nutrition and/or genetics. It was shown that different levels of herbage allowance and the use of crossbred cows could improve the follicular and uterine characteristics that translate into higher cow fertility.

ABSTRACT.- CONTEXT: The Latin America-Caribbean (LAC) region has the potential to pursue a sustainable expansion of livestock production and capitalise on the growing global demand for dairy and beef products. However, it is necessary to understand the predominant production systems and their biophysical, economic, social, and environmental performances. OBJECTIVE: This study aimed to compare the milk production systems of nine countries of the region according to their major biophysical, socio-economic, and environmental performance indicators.

ABSTRACT.- Dairy systems in South America's humid subtropics include grass-legume pastures in rotation with winter-summer double-cropping for silage, thus combining direct grazing with periods of effective confinement for concentrate and silage supplementation. The environmental impacts of these so-called hybrid systems remain unclear. © The Author(s), under exclusive licence to Springer Nature B.V. 2024.

ABSTRACT.- Management practices during the rearing of dairy heifers should allow an adequate body growth and reproductive development to attain puberty several months before the first conception. Proposed target age and body weight (BW) at first calving for Holstein heifers are between 22-24 months and 82% of mature BW, respectively, for which heifers must conceive at around 15 months of age with 60% of their mature BW.

ABSTRACT.- The process of intensification of the dairy sector has been characterized in recent decades by the increase in milk production per hectare, the increase in livestock density, the inclusion of more concentrates in the diet, and the improvement of the genetic merit of dairy cows. The use of models has productive, environmental, and economic advantages. The objectives of the study were to describe a new model, "OLE!

ABSTRACT.- Uruguay's dairy can potentially enhance milk productivity competitively, but intensification risks elevating nitrogen (N) surplus, heightening environmental concerns. This study quantified farm-gate N inputs and outputs, calculating N surplus (input-output) and N use efficiency (NUE=output/input) for 17 commercial modal dairy systems identified in the 2014 and 2019 national surveys and six prospective intensified systems based on experimental pastoral farmlets achieving near-maximal rainfed productivity. .-.-.-.-.-.-.-.-.-.

ABSTRACT.- The impact of GnRH treatment on the day of TAI in beef cows has received limited investigation, especially concerning its association with estrus expression. Consequently, two experiments were conducted to assess the potential of GnRH treatment on the day of TAI to enhance fertility according to the expression or not of estrus in beef cows. Experiment 1 aimed to determine ovulation rate and luteal function, while Experiment 2 aimed to determine the effect of the two GnRH treatment approaches on pregnancy rate. © The Author(s).

ABSTRACT.- Mixed systems of grain and livestock production based on pasture-crop rotations are a promising strategy to promote agriculture resilience and allow an ecological intensification of agriculture yet little is known about underlying processes in soil. To test the hypothesis that pasture-crop rotations preserve soil structure and select for beneficial soil and rhizosphere microbiota, supporting soil health and grain production, a long-term field experiment under no-tillage was studied.

ABSTRACT.- Correction to: Scientific Reportshttps://doi.org/10.1038/s41598-024-59513-6, published online 02 May 2024. The PDF version of this Article contained errors in Equations 1 and 2, where the equations were incompletely displayed. The correct equations are displayed below: (Formula presented.) (Formula presented.) The original Article has been corrected. © The Author(s) 2024.