Effects of gestational plane of nutrition and selenium supplementation on mammary development and colostrum quality in pregnant ewe lambs

¹ Center for Nutrition and Pregnancy, Department of Animal Sciences, North Dakota State University, North Dakota State University, Fargo
² USDA, ARS, U. S. Sheep Experiment Station, Dubois, ID 83423

^* To whom correspondence should be addressed. E-mail: Kim.Vonnahme{at}ndsu.edu.

	Abstract

To examine effects of nutritional plane and selenium (Se) supplementation on colostrum quality and mammary development, individually fed, pregnant Rambouillet ewe lambs were allotted randomly to 1 of 6 treatments in a 2 x 3 factorial arrangement. Main effects included dietary Se level which began at breeding (d = 0) [adequate Se (ASe, 9.5 µg/kg BW) vs. high Se (HSe, 81.8 µg/kg BW)], and plane of nutrition which began at d 50 of gestation [60% (RES), 100% (CON), and 140% (HIGH) of requirements]. Upon parturition lambs were immediately separated from dams and weighed. Three hours after lambing, colostrum yield was determined and samples were obtained for components and IgG analysis. Ewes were slaughtered within 24 h of parturition, and mammary tissues were collected for determination of alveolar secretory epithelial cell proliferation index and luminal area. Gestation length was reduced (P < 0.01) in HIGH ewes compared to RES and CON ewes. Although birth weights were reduced (P < 0.01) in RES and HIGH compared with CON ewes, there was little effect of diet on placental size. Mammary gland weight was reduced (P 0.05) in RES compared to CON and HIGH, which were similar. However, when expressed as g/kg BW, mammary gland weight in HIGH ewes was less (P = 0.03) compared to RES and CON. Colostrum weight and volume were reduced (P < 0.01) in RES and HIGH ewes compared with CON. Although colostrum IgG concentration was greater in RES ewes compared to CON and HIGH, total IgG was lower (P 0.06) in RES and HIGH compared to CON ewes. The percentage of alveolar cells proliferating was increased (P < 0.04) in HIGH compared with RES ewes, with CON being intermediate. Percentage of alveoli luminal area per unit tissue area was increased (P = 0.04) in RES compared with HIGH and CON ewes, which did not differ. Selenium had no effect (P 0.15) on mammary gland weight, colostrum quantity, or IgG concentration in pregnant ewe lambs. Improper nutrition from mid to late pregnancy in ewe lambs altered colostrum quality and quantity, and reduced offspring birth weight, which may have negative implications for lamb health and survival during the early postnatal period.

Key Words: colostrum, ewe lambs, nutritional level, pregnancy, selenium