Zinc plays critical roles during embryogenesis, fetal growth, and milk secretion, which increase the zinc need for pregnancy and lactation. Increased needs can be met by increasing the dietary zinc intake, along with making homeostatic adjustments in zinc utilization. Potential homeostatic adjustments include changes in circulating zinc, increased zinc absorption, decreased zinc losses, and cha...

To better understand the role of nutrition in regulating mammary gland development and lactation, we designed a novel stair-step compensatory nutrition regimen that is a unique combination of dietary energy restriction and realimentation (refeeding) phases; the basic concept of this regimen is to exploit the biological nature of the compensatory growth phenomenon in concert with one or more hor...

Lactating dairy cow diets with more than 24% starch (DM basis) are common, but recent high corn prices have fueled a desire to feed lower-starch diets. The potential for using digestible neutral detergent fiber or pectin from byproduct feeds or sugars to partially replace starch from corn grain in diets fed to lactating dairy cows was reviewed. Potential modifying effects of corn silage, starch...

Three-hour milk production measurements determined by machine milking at 3-d intervals throughout a 63-d lactation period were used to describe lactation curves for crossbred ewes lambing at 1 and 2 yr of age and rearing single and twin lambs. Age of ewe, type of rearing, and day of lactation affected (P < 0.05) milk production. Over the 63-d lactation, average daily milk production was 2.56 an...

Lactation records for milk, fat, and protein yields were calculated from test-day data adjusted for the effects of lactation stage, age, previous days open, days pregnant, and test-day class (herd, test date, and milking frequency). Those lactation records reflect the improved accounting of environmental effects from a test-day model and can be combined with historical lactation records. Test-d...

Multivariate factor analysis and principal component analysis were used to decompose the correlation matrix of test-day milk yields of 48,374 lactations of 21,721 Italian Simmental cows. Two common latent factors related to level of production in early lactation and lactation persistency, and 2 principal components associated with the whole lactation yield and persistency were obtained. Factor ...

Milk production is largely dependent on the shape of the lactation curve. Relevant elements of the lactation pattern are the peak yield, which represents the maximum milk yield during the lactation, and the lactation persistency, which expresses the ability of animals to maintain a reasonably constant milk yield after the lactation peak (Figure 1). Thus, persistent animals are those that show f...

The difficulties and costs of measuring individual feed intake in dairy cattle are the primary factors limiting the genetic study of feed intake and utilisation, and hence the potential of their subsequent industry-wide applications. However, indirect selection based on heritable, easily measurable, and genetically correlated traits, such as conformation traits, may be an alternative approach t...

A case-acquisition and decision-support system was developed to support the analysis of group-average lactation curves and to acquire example cases from domain specialists. This software was developed through several iterations of a three-step approach involving 1) problem analysis and formulation in consultation with two dairy nutrition specialists; 2) development of a case-acquisition and dec...

Clinical mastitis in dairy cows has for many years been the subject of numerous epidemiological surveys to determine the main risk factors. In most cases this data has been analysed using a standard Poisson model without taking into consideration possible dependence between consecutive pathological events. These analyses have brought to light a great many potential risk factors without making i...