The objective of the present study was to estimate (co)variance components for length of productive life (LPL) and some alternative reproductive traits of 6-year-old Nellore cattle. The data set contained 57,410 records for age at first calving from Nellore females and was edited to remove animal records with uncertain paternity and cows with just one piece of calving information. Only animals ...

Milk yields were measured every 6 weeks from 21220 days after calving in either moderate or low conditioned groups of Angus, Angus x Friesian or Simford first-calf heifers for 3 successive years. Day of peak yield, peak yield and total 220 day yield were calculated by fitting 3 published equations to data on each of the breed x year x calving condition combinations. All equations ranked breed a...

The factors influencing weight changes during the grazing season of Brown Swiss autumn-calving cows and Brown Swiss and Pirenaica spring-calving cows and their calves were studied over an 8-yr period in Spanish mountain conditions. The data set comprised 552 annual production cycles of cows that calved in two consecutive years. The animals grazed on alpine ranges during the summer and on forest...

Reproductive performance is a key driver of the economics of dairy and beef breeding herds. In the absence of hormonal treatment to induce or stimulate lactation, regular parturition and initiation of lactation are key events directly affecting the average daily milk production of dairy herds, culling decisions and farm gross margins. Thus efficient reproductive management is a critical prerequ...

Calving records from the Animal Breeding Center of Iran collected from January 1993 to December 2007 and comprising 1 163 594 Holstein calving events from 2 552 herds were used to evaluate reported perinatal calf mortality, 305-d milk yield, 305-d fat yield of milk and 305-d fat percentage of milk in singleand twin-births. A logistic regression model was constructed to analyze calf mortality be...

This 4-yr study was conducted with Angus (A)-sired and Polled Hereford (PH)-sired crossbred heifers that were exposed to either A or medium-frame Brahman (B) bulls from primiparous calvings either as 2- or 3-yr-olds. Each year, heifers were allotted at random within breed composition and age of dam to breeding groups on pasture for an 84-d breeding period that began in late March or early April...

The objective of this study was to evaluate the relationships between several health disorders: milk fever (MF; hypocalcaemia and parturient paresis), retained placenta (RP; retained foetal membranes), metritis (ME; endometritis and pyometra), ovarian cysts (OC; follicular and luteal cysts), clinical mastitis (CM), and lameness (LS; foot and leg problems) as affecting the reproductive performan...

Aerial photography and satellite imagery of the Petersen ice shelf, Nunavut, Canada, from 1959 to 2012 show that it was stable until June 2005, after which a series of major calving events in the summers of 2005, 2008, 2011 and 2012 resulted in the loss of 61% of the June 2005 ice-shelf area. This recent series of calving events was initiated by the loss of extensive regions of >50-year-old mul...