Coefficient of relationship (r): the proportion of genes (or alleles) that two individuals share by common descent. Coefficient of relationship is a consequence of meiosis and sexual reproduction. Parents share 50% of their genes with their offspring (r=.50). Grandparents share 25% of their genes with their grand-offspring (r=.25). Half sibling share 25% of their genes, on average (r=.25), whil...

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 physiology of human lactation is described with secretions on mammary gland anatomy and development, the mechanisms of milk secretion and ejection, and the temporal sequence of events during the transition from pregnancy to lactation (lactogenesis). Finally, interactions between lactation and maternal metabolism are briefly described and the interaction of lactation with fertility discussed.

osteoporosis is considered as an important public health problem especially in postmenopausal women. there are some hypotheses support the contributory effect of pregnancy and lactation on osteoporosis later in life. high calcium demand during pregnancy and lactation and low estrogenic state support those hypotheses. numerous studies have investigated on the issue but there is no consensus abou...

This investigation evaluated mammary cell loss and replacement during lactation and the impact of administration of bST on these processes. During lactation, a gradual decrease in number of mammary epithelial cells within the mammary glands occurs and largely accounts for the decline in milk production with advancing lactation. This decrease is not appreciably impacted by the loss of viable epi...

Several functions were used to model fixed and random part of the lactation curve in Iranian primiparous Holstein cows using random regression analysis. Legendre polynomials of orders three and four as well as parametric lactation curve for the random part of the first lactation milk production were compared to find the best model. The models differed in fixed regression lactation curve part an...