Effects of Energy Balance on Ovarian Activity and Recovered Oocytes in Holstein Cows Using Transvaginal Follicular Aspiration
Kendrick, Kerry Wyn II
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The effects of energy balance on hormonal patterns and recovered oocytes were evaluated in 20 lactating Holstein cows during two trial periods (fall/spring). Cows were randomly selected and assigned to one of two dietary treatments formulated so that cows consumed 3.6% BW (HE- 1.78 mcal/kg; n=6 in fall, n=5 in spring) and 3.2% BW (LE-1.52 mcal/kg; n= 5 in fall, n=4 in spring). Body weight and body condition score (BCS) were recorded prior to parturition and weekly throughout the fall trial. Ultrasound guided transvaginal follicular aspirations were conducted twice weekly between d 30 and 100 of lactation. Follicle size and number were recorded. Follicular fluid (FF) was aspirated from the largest follicle, and serum samples were collected for hormone assay (IGF-1; estradiol (E2); progesterone (P4, serum ); LH and FSH). Oocytes were collected and graded based upon cumulus density and ooplasm homogeneity, then fertilized and cultured in vitro. Milk yield averaged 41.64 Â± .3 kg/d (mean Â± SE) for HE and 32.8 Â± .3 kg/d for LE. There was a significant cubic day postpartum by treatment interaction for milk yield. Dry matter intake and BW treatment by week interactions were significant for the cubic and linear components, respectively. Oocyte numbers increased linearly from d 30 to 100 postpartum. HE cows produced more good + oocytes (1.5 Â± .2 ) than LE cows (1.4 Â± .1). Follicles less than or equal to 5 mm predominated throughout the study (6.4 Â± 3.0). However, greater numbers of follicles 10 to 14 mm and greater than or equal to 15 mm were found in the fall (1.98 Â± .08 and .50 Â± .06) than spring (1.11 Â± .3 and .23 Â± .07). Follicular fluid IGF-1 was higher in HE (2.3 Â± .2 ng/ml) than in LE cows (1.6 Â± .2 ng/ml). Mean basal serum FSH concentration was lower at 28 d postpartum (173 Â± 8 pg/ml) compared to later (521 Â± 25 at d 60 and 650 Â± 25 pg/ml at d 110). Serum P4 peaked at 35 d postpartum, with HE cows having 1 ng/ml higher P4 than LE cows. Low dietary energy reduced milk yield, DMI, BCS, FF IGF-1 and serum P4 and had a negative impact on oocyte quality.
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