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ARS Home » Plains Area » Clay Center, Nebraska » U.S. Meat Animal Research Center » Nutrition, Growth and Physiology » Research » Publications at this Location » Publication #305182
Title: The consequence of level of nutrition on heifer ovarian and mammary development

Author
item Freetly, Harvey
item VONNAHME, K - North Dakota State University
item McNeel, Anthony
item CAMACHO, L - North Dakota State University
item Amundson, Olivia
item Forbes, Elizabeth
item Lents, Clay
item Cushman, Robert - Bob

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/10/2014
Publication Date: 11/21/2014
Publication URL: http://handle.nal.usda.gov/10113/59894
Citation: Freetly, H.C., Vonnahme, K.A., McNeel, A.K., Camacho, L.E., Amundson, O.L., Forbes, E.D., Lents, C.A., Cushman, R.A. 2014. The consequence of level of nutrition on heifer ovarian and mammary development. Journal of Animal Science. 92(12):5437-5443.

Interpretive Summary: Replacing cows in the herd is second only to nutrition as the single greatest input cost in cow/calf beef production. The increased availability of cereal grains for feeding livestock has allowed replacement heifers to enter the production system at younger ages. Many heifer development programs feed heifers large quantities of feed to ensure they reach puberty before breeding. Nutrition level during development has been associated with altered milk production and longevity; however, the mechanisms that lead to these outcomes have not been identified. We found that heifers whose growth has been slowed through nutrition level before puberty, and accelerated near puberty to breeding, have more follicles on their ovaries than heifers fed for rapid weight gain throughout the same period. This increase in follicle number may result in prolongation of her reproductive years.

Technical Abstract: Replacing cows in the herd is second only to nutrition as the single greatest input cost in cow/calf beef production. The increased availability of cereal grains for feeding livestock has allowed replacement heifers to enter the production system at younger ages. Many heifer development programs feed heifers large quantities of feed to ensure they reach puberty before breeding. Nutrition level during development has been associated with altered milk production and stayability. We hypothesized that heifers exposed to different levels of nutrition during the peripuberal period would differ in methylation of the DNA in the mammary gland and ovarian cortex. We also hypothesized that the ovarian reserve would decrease in heifers fed for rapid growth compared to heifers fed for slow growth during puberty. At 257 ± 1 d of age, heifers in the Stair-Step treatment (n = 6) receive 157 kcal ME/BW kg0.75 for 84 d, and heifers in the Conventional treatment (n = 6) were offered 228 kcal ME/BW kg0.75. At d 84, heifers were fed for an additional 83 d. Stair-Step heifers were offered 277 kcal ME/BW kg0.75, and heifers on the Conventional treatment received 228 kcal ME/BW kg0.75. Mammary weights (P = 0.43), capillary area density (P = 0.74), and capillary surface density (P = 0.18) did not differ between treatments; nor did alveolar number (P = 0.55) and alveolar density (P = 0.49). Reproductive tract weights (P = 0.69) and ovarian weight (P = 0.68), and ovarian size (P > 0.75) did not differ between treatments. In histological sections, Stair-Step heifers had more primordial follicles than Conventional heifers (P = 0.02), but primary (P = 0.59) and secondary (P = 0.15) follicles did not differ. Global methylation of parenchymal tissue (P = 0.82), mammary fat pad (P = 0.45), and ovarian cortex (P = 0.14) did not differ between treatments. Anterior pituitary weight did not differ between treatments (P = 0.16). Our hypothesis that modifying peripubertal nutrition modifies global methylation of the mammary and ovary is not supported; however, our hypothesis that it modifies the ovarian reserve is supported.