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Ultrasonography was used as a noninvasive method for quantitative estimation of the subcutaneous and abdominal adipose tissue depots in dairy cattle. The prediction model was created and validated with a total of 29 German Holstein cows; 6 were in early lactation (≤100 d in milk [DIM]) and 16 were in advanced lactation (101 to 292 DIM). Seven cows were nonpregnant and nonlactating and had been off milk for 350 to 450 d. Transcutaneous assessment of the thickness of subcutaneous and retroperitoneal adipose tissue was done at 16 sites on the body surface of all cows. After completion of the ultrasonographic measurements, the cows were slaughtered and the adipose depots were separately weighed. A stepwise multivariate regression analysis of the ultrasonographic variables was performed to estimate the slaughter weights of the different fat depots. Slaughter weights of the fat depots ranged from 5.0 to 43.0 kg for subcutaneous adipose tissue (SCAT), from 13.7 to 98.8 kg for abdominal adipose tissue (AAT), from 3.4 to 30.3 kg for retroperitoneal adipose tissue (RPAT), from 5.2 to 39.6 kg for omental adipose tissue (OMAT), and from 4.0 to 35.8 kg for mesenteric adipose tissue (MAT). The relationship between calculated amount of fat and slaughter weight of fat had coefficients of determination () and root mean square errors (kg) of 0.88 and 3.4, respectively, for SCAT; 0.94 and 6.1, respectively, for AAT; 0.94 and 1.7, respectively, for RPAT; 0.83 and 3.2, respectively, for OMAT; and 0.95 and 1.6, respectively, for MAT. The accuracy of ultrasonographic measurement of the different fat depots appears sufficient for the quantitative assessment of internal and subcutaneous fat stores in cows. This method is noninvasive and therefore allows safe and repeated monitoring of the amount of stored fat in different adipose tissue depots of German Holsteins cows.

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The somatotropic axis is a key metabolic pathway during transition from late pregnancy to early lactation in dairy cows. The first objective of this study was to determine the feasibility of selecting cows with persistent differences in total insulin-like growth factor 1 (IGF-1) concentration by taking only a single antepartum blood sample. The second objective was to elucidate the underlying causes of differences in peripheral IGF-1 concentrations throughout late pregnancy and whether hormonal axes also differed in dairy cows with low versus high IGF-1. Twenty clinically healthy Holstein Friesian cows were chosen based on their plasma IGF-1 concentration at 244 to 254 d after artificial insemination (AI) and other selection criteria (health status, body condition score, number of lactations). These cows were selected from a large-scale farm, transported to the clinic, and monitored daily from 261 to 275 d after AI. The concentrations of IGF-1, growth hormone, IGF binding proteins 2, 3, and 4, insulin, cortisol, thyroid hormones, progesterone, and estradiol were measured. Ultimately, 7 IGF-1-low and 7 IGF-1-high cows were statistically analyzed. Additionally, a liver biopsy was taken on d 270 ± 1 after AI for analysis of gene expression of somatotropic family members, liver deiodinase 1, and suppressor of cytokine signaling-2. It was possible to select cows with different IGF-1 concentrations based upon only 1 blood sample collected in late pregnancy. Concentrations of IGF-1 in IGF-1-low versus IGF-1-high animals (n=7 each) remained significantly different between groups from the day of selection of the animals until d 275 after AI. Second, the differences in total plasma IGF-1 concentration between experimental groups may be attributed to differences in hepatic production of acid labile subunit. The ability of IGFBP-3 to bind IGF-1 declined before calving in all cows. Furthermore, in addition to decreased mRNA expression of growth hormone receptor 1A and IGF-1 relative to calving, serum binding capacities for IGF-1 also decreased. Insulin-like growth factor binding protein 4 mRNA expression was higher in cows with low IGF-1 concentrations; this binding protein inhibits IGF-1 action at the tissue level and therefore may reduce IGF-1 bioavailability. Finally, other endocrine end points (e.g., insulin and thyroid hormones) differed between the 2 groups.

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