Download Dietary Nutrient Affects Mammary Gland Growth in Lactating Sows

Dietary Nutrient Affects Mammary Gland Growth
in Lactating Sows
S. W. Kim, W. L. Hurley, and R. A. Easter1
Department of Animal Sciences
University of Illinois at Urbana-Champaign
There are many factors that can potentially affect mammary gland growth. Estrogen and progesterone
are known as essential hormonal factors for the growth of mammary glands during lactation. Insulin,
cortisol, thyroid hormone, and prolactin also support mammary gland growth. Nutrient intake may also
affect the growth of mammary glands. During gestation, dietary protein level does not affect mammary
gland growth of gilts (Weldon et al., 1991; Kusina et al., 1999). However, excessive energy intake
during gestation reduces mammary gland growth of gilts (Weldon et al., 1991).
The lactation period is a challenge for the sow. Milk production results in a high demand for nutrients by
the sow and sows will mobilize their body tissues when dietary nutrients do not meet the demands for
milk production. However, the mammary glands are also growing during lactation (Kim et al., 1999a),
even though sows are in a catabolic state. It may be expected that level of dietary nutrient intake during
lactation may impact mammary gland growth, although this relationship has not been demonstrated
previously.
Protein and energy intake affect mammary gland growth during lactation
Sixty-one primiparous sows were fed four different diets containing two levels of protein and two levels
of energy (Kim et al., 1999b). Teat order was observed from each litter one day prior to killing of sows
to know which glands were nursed during lactation. Sows were killed at times up to 30 d of lactation.
Mammary glands were dissected into individual glands and only glands known to have been nursed by
pigs during lactation were used for these analysis. Wet weight of individual glands was recorded.
Both protein intake and energy intake of lactating sows affected the growth of the mammary gland
during lactation. Growth of mammary glands was stimulated by increased dietary protein and energy
during lactation. We generated three-dimensional response surface graphs to show the effects of protein
and energy on mammary gland growth as lactation progressed (Figure 1). The x-axis represents total or
accumulative energy intake of the sow as lactation progresses, the y-axis represents total protein intake
of the sow, and the z-axis represents response variables, such as wet weight and DNA content. The
highest point of the graph indicates the combination of dietary protein and energy when mammary gland
1
Sungwoo Kim is a postdoctoral research associate of swine nutrition, Walter Hurley is a
Professor of lactation biology, and Robert Easter is a Head of Department and Professor of swine
nutrition.
growth was maximized. Thus, the day of lactation and dietary protein and energy levels when sows had
maximum mammary gland growth during lactation can be estimated. Mammary gland growth of lactating
sows was maximized when sows consumed daily 16.9 Mcal ME and 55 g lysine (990 g crude protein).
Maximal mammary gland size occurred between d 25 and 28 of lactation. Feeding sows adequately for
maximal mammary gland growth should be emphasized for improving weaning weight of pigs. Both
protein intake and energy intake during lactation should be considered when accounting for mammary
growth.
References
Kim, S. W., W. L. Hurley, I. K. Han, and R. A. Easter. 1999a. Changes in tissue composition
associated with mammary gland growth during lactation in the sow. J. Anim. Sci. 77:2510.
Kim, S. W., W. L. Hurley, I. K. Han, H. H. Stein, and R. A. Easter. 1999b. Effect of nutrient intake on
mammary gland growth in lactating sows. J. Anim. Sci. 77 (In press).
Kusina, J., J. E. Pettigrew, A. F. Sower, M. R. Hathaway, M. E. White, and B. A. Crooker. 1999.
Effect of protein intake during gestation on mammary development of primiparous sows. J.
Anim. Sci. 77:925.
Weldon, W. C., A. J. Thulin, O. A. MacDougald, L. J. Johnston, E. R. Miller, and H. A. Tucker.
1991. Effects of increased dietary energy and protein during late gestation on mammary
development in gilts. J. Anim. Sci. 69:194.