test day milk records of a holstein dairy farm collected during years 2004 to 2006 on 142 cows in the 1st lactation vs. 140 cows in the 2nd lactation were used in this research. there were real milk yields of cows available in each part of lactation in this farm making it possible to compare functions based on the new criteria (squared error of estimation). five functions were compared to estim...

Most studies on the factors limiting sustained energy intake (SusEI) during peak lactation period have been performed in females at the 1st lactation event. However, an inconsistent change in SusEI is observed between the 1st and 2nd lactation event. Thus, the limits to SusEI may be associated with reproductive experiences, but the effects of reproductive experiences on SusEI or reproductive ou...

Rats ovulate during the 1st or 2nd night following parturition (Hoffman & Schwartz, 1965). Subsequently, oestrus is not usually observed during lactation. After weaning, cycling is resumed and only then can oestrus be discerned (Long & Evans, 1922). The possibility of studying the relation between lactation and fertility is, therefore, conditional on effective mating of the females at the post-...

milk and fat yields in 3x and 4x milking schedule in holstein cows of iran were investigatedusing 374170 milk and fat yield test day records measured on the 1st and 2nd lactions of 54580 dairycattle coming from 205 herds. the records had been collected from 2007 to 2009 by the iraniananimal breeding center (iabc). the results indicated that an increases in the milking frequency from3x to 4x inc...

Enzootic bovine leukosis is a contagious disease of cattle caused by the retrovirus, bovine leukemia virus (BLV) and is the most common cause of malignant neoplasm in cattle. In order to facilitate surveillance of this disease in dairy herds, we developed a method to combine ELISA of milk collected during routine production testing with a prescribed sampling of cows that is independent of the p...

BACKGROUND Parturition is supposed to be related to oxidative stress, not only for the mother, but also for the newborn. Moreover, it is not clear whether consecutive pregnancies, parturitions, and lactations are similar to each other in regards to intensity of metabolic processes or differ from each other. The aim of the study was to compare dynamic changes of antioxidative parameters in colos...

The object of an experiment was inorganic and organic forms of zinc, copper and manganese applied in mineral mixtures to dairy cows. The experiment was carried out on 90 cows with average milk yield for previous lactation of about 9 500 kg milk. The cows received mineral mixtures containing inorganic or organic forms of zinc, copper and manganese for 6 weeks before calving and during the first ...

The duration of the diestrous period in vaginal smears and the levels of progestins in ovarian venous blood were investigated in rats whose lactation period was prolonged by replacing pups at appropriate intervals. In prolonged lactating rats, the first diestrous period after the pospartum ovulation (21.7 +/- 0.8 days) was similar to that occurring in normal lactating rats. Subsequently proestr...

to study the effects of environmental factors on milk and fat yields (240day) traits of iranian buffaloes, 22596 and 22165 records were utilized for milk and fat yield traits, respectively. uni and bivariate analysis for estimation of (co)variation components of the traits were done in five lactations. milk yield in the 1st lactation had the highest number of records (4482), collected through c...

Background: It was hypothesized that under apparently good management practices in dairy farms, some cows may not be metabolically perfect during the breeding period and this may affect their performance. Aims: This study was conducted to assess probable metabolic drawbacks in mid-lactation dairy cows affecting their performance. Methods: Thirt...