Sow milk yield is the main determinant of piglet growth rate as it is the only source of energy for suckling piglets. Sows do not produce enough milk to sustain optimal growth of their litter and this problem was made worst with the current use of hyperprolific sow lines. Milk yield is influenced by numerous factors but one factor of importance which is often overlooked is mammary development. In swine, mammary development takes place in prepuberty, as of 3 months of age, during the last third of pregnancy, and during lactation. It is during these periods of rapid mammary growth that nutritional strategies could be used to enhance mammary development. From 90 days of age until puberty, a 20% feed restriction drastically reduces mammary tissue mass whereas decreasing protein intake has no effect on mammary development and feeding the phytoestrogen genistein increases mammary cell number. During late gestation, feeding very high energy levels may have detrimental effects on mammary development and subsequent milk production. Bqdy condition is important to consider. Gilts that have a lower feed intake during gestation and are too thin at the end of gestation have reduced mammary development. Feeding during lactation also affects mammary development.There is an increase in weight of functional mammary glands when sows are fed either more protein or more energy. It is therefore imperative to maximise feed intake of lactating sows. Much remains to be learned about the optimal feeding management to enhance mammary development in gilts and sows.
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