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This study was conducted to investigate individual metabolic and endocrine adaptation to lactation under conditions of identical housing and feeding conditions in high-yielding dairy cows. Forty-five cows were studied on a research farm under standardized but practical conditions. From wk 2 before calving until wk 14 postpartum, blood samples were collected at weekly intervals and assayed for blood chemistry and various metabolites and hormones. Body weight, BCS, and backfat thickness were also recorded weekly. Milk yield, milk composition, and feed intake and energy balance were accordingly measured during the postpartum phase. The animals were retrospectively classified according to their plasma concentration of [beta]-hydroxybutyrate (BHB): cows in which a BHB threshold of 1 mM was exceeded at least once during the experiment were classified as BHB positive (BHB+); cows with BHB values consistently below this threshold were classified as BHB negative (BHB-). Using this classification, differences for NEFA and glucose concentrations were observed, but the mean calculated energy balance did not differ between the groups during the experimental period (-22.2 MJ of [NE.sub.1]/d [+ or -] 4.7 for BHB+ and -18.9 MJ of [NE.sub.1]/d [+ or -] 4.9 for BHB-). In BHB+ cows, the peripartum decrease (P < 0.05) of BW, BCS, and backfat thickness was more pronounced than in BHB- cows. Mean milk yields did not differ between groups. However, BHB+ cows had greater milk fat and lesser milk protein contents (P < 0.05), resulting in a greater (P < 0.05) fat:protein ratio than in BHB- cows. Thus, to some extent, cows were able to compensate for the negative energy balance by adjustments in performance. Milk acetone concentrations followed BHB concentrations in blood. Insulin-like growth factor-I and leptin concentrations were greater (P < 0.05) in BHB- cows during the time of observation than in the BHB+ cows. Comparing the reproductive variables recorded (first increase of progesterone, first service conception rate, number of services per conception, interval from calving to first AI, interval from first AI to conception, and days open) between the 2 groups yielded no significant differences. Our findings imply that despite comparable energy balance, there is considerable individual variation of the adaptive ability of cows during early lactation based on a variety of metabolic and endocrine variables. Key words: body condition, dairy cow, energy supply, ketosis, metabolic profile

The transition of pregnancy to lactation, with the concomitant negative energy balance during early lactation, requires substantial adaptive performance of the cow. Apart from clinical disease problems, the identification of cows with suboptimal adaptation is relevant to be able to adequately treat these animals or modify the ration. Effective approaches are necessary to provide maximal information at the earliest time possible. We therefore aimed to identify a measurement that, when applied at a defined point in time relative to calving, was relevant as much as possible to other information on metabolic and health status during early lactation. Blood samples were collected weekly from 4 wk antepartum to 12 wk postpartum from 38 high-yielding Holstein-Friesian cows. Nonesterified fatty acids, beta-hydroxybutyrate, IGF-I, and leptin were measured in serum, and BCS was recorded. Health status was characterized using the concentrations of haptoglobin, the number of leukocytes and neutrophils, as well as the activity of glutamate dehydrogenase (GLDH) in blood to evaluate liver status. Using the factors related to fat mobilization, the animals were classified according to their values recorded at one defined point in time or time interval as being above or below certain thresholds. For each criterion, the groups classified were compared with regard to the time-course yielded from all recordings. From 7 criteria of classification, the most closely related to the variables of fat mobilization was obtained when using NEFA and IGFI (thresholds of 0.5 mm and 39 ng/mL in wk 1 postpartum, respectively). Both items were then combined into to the criterion NEFA + IGF-I. Applying these criteria, the relations to indices of health and liver status were detectable on the basis of NEFA- and NEFA + IGF-I-classes, which yielded differences in both GLDH and leukocyte numbers. Animals with NEFA > 0.5 mm showed increased GLDH activity but decreased leukocyte numbers. The time and effort required for measuring the IGF-I-concentration in addition to NEFA is not justified for evaluating the metabolic status. Nonesterifled fatty acid values [greater than or equal to] 0.5 mm during the first week of lactation were considered as the most suitable criterion for identifying limited adaptive performance. Key words: adaptation, cattle, fat mobilization, insulin-like growth factor-I, nonesterified fatty acid, transition period

The effect of testosterone on sexual dimorphism is evident by differential growth of forelimb and neck muscles in bulls and steers. Divergent hormone sensitivites may account for the differential growth rates of individual muscles. Therefore, the objective of this study was to compare androgen receptor (AR) expression in three different muscles of bulls and steers at various ages and growth rates. Thirty Montbeliard bulls and 30 steers were assigned to four slaughter age groups. Four or five animals of each sex were slaughtered at 4 and 8 mo of age. Animals in the remaining two slaughter groups (12 and 16 mo) were divided into groups of either restricted (R) or ad libitum (AL) access to feed. Five animals of each sex and diet were slaughtered at the end of the restricted intake period at 12 mo of age. To simulate compensatory growth, the remaining animals (R and AL) were allowed ad libitum access to feed until slaughter at 16 mo of age. Total RNA was extracted from samples of semitendinosus (ST), triceps brachii (TB), and splenius (SP) muscles. Androgen receptor mRNA was quantified in 200-ng total RNA preparations using an internally standardized reverse transcription (RT) PCR assay. Data were analyzed using 18S ribosomal RNA concentrations as a covariable. Steers had higher AR mRNA levels per RNA unit than bulls (P < .01). Androgen receptor mRNA levels differed between muscles (P < .05), with lowest expression in the SP. The pattern of AR expression differed (P < .05) for each muscle with increasing age. Between 4 and 12 mo of age, AR mRNA levels increased (P < .05) in SP but remained unchanged in the ST and TB. Feeding regimen had no effect on muscle AR expression, but steers exhibiting compensatory growth had higher AR mRNA levels than AL steers (P < .01) or bulls (P < .01). Our results show that AR expression is muscle-specific and may be modulated by circulating testicular hormones. These data suggest that the regulation of AR expression may be linked to allometric muscle growth patterns in cattle and compensatory gain in steers. Key Words: Cattle, Skeletal Muscle, Growth, Castration, Androgens, Messenger RNA, Polymerase Chain Reaction

The importance of the GPR41 for the regulation of the leptin system in ruminants is not yet clarified. The aim of this study was to compare GPR41 mRNA expression in two different fat depots and to test the effects of intravenously infused propionate on GPR41 mRNA, serum leptin and its mRNA as well as leptin receptor mRNA in goats. In mice, GPR41 is recognized to be regulated by short chain fatty acids (SCFAs) with propionate being the most potent ligand. Propionate up-regulates leptin synthesis in this species. In contrast to monogastric mammals, ruminants almost entirely depend on SCFAs as energy source, but the reports about the relevance of propionate for leptin secretion in these species are controversial. Castrated male goats (Deutsche-Edelziege, 10 to 12 months old) were allocated to infusions through jugular catheters after an overnight fast. They received propionate infusions (96 μmol/kg*min; n=8) or NaCl-solution (equivalent Na-concentration; n=5). After recording leptin baseline concentrations for 1h, infusions were carried out for 260 min. Blood samples were collected in 10 to 15 min intervals and analyzed for leptin by ELISA. The mRNAs of leptin, leptin receptor (long form) and GPR41 from subcutaneous adipose tissue (SAT) and perirenal adipose tissue (PAT) were quantified by real-time RT-PCR after euthanasia (propionate group: n=4; NaCl group: n=5). Repeated measures analysis of serum leptin values showed an increase in the propionate versus the control group (p<0.05). Estimation of the mRNA expression data indicated a tendency for an increase of leptin mRNA in PAT (p=0.081) but not in SAT (p=0.106). The leptin receptor mRNA decreased in PAT (p=0.042) and in SAT, the latter decrease, however, did not reach the level of significance (p=0.286). GPR41 mRNA was elevated in SAT (p=0.029) but not in PAT (p=0.756). In conclusion, we established the expression of GPR41 in adipose tissue of a ruminant species; the effects of the propionate challenge indicate that GPR41 is involved in mediating propionate effects on the leptin system, at least at the provocative dosage tested. [ABSTRACT FROM AUTHOR]

The transition of pregnancy to lactation with the concomitant negative energy balance during early lactation requires substantial adaptive performance of the cow. Based on parameters of fat mobilization, we aimed to evaluate the adaptive status in dairy cows during the peripartal period. Blood samples were collected weekly from 4 wk ante partum to 12 wk post partum (p.p.) from 38 high yielding Holstein Frisian cows. For differentiating "adaptive performance satisfying" versus "adaptive performance limited" (AP-ltd), non-esterified free fatty acids (NEFA), beta-hydroxybutyrate, insulin-like growth factor-1 (IGF-1) and leptin were determined in serum and BCS was recorded. The animals were classified by using different thresholds and/or parameter combinations to determine which parameter will yield maximal consent with the other parameters to qualify only one or few parameters for field applications (GLM; SPPS). Health status was characterized using the concentrations of haptoglobin (Hp), the numbers of leukocytes and neutrophils as well as oxidative stress (dROM test) in blood. Liver impact was evaluated via glutamate-dehydrogenase (GLDH) activity in blood. From 7 criteria of classification, most information on fat mobilization was obtained from NEFA (>0.5 mM in wk 1 p.p.) as well as IGF-1 (<39 ng/mL in wk 1 p.p.) threshold values, and were combined as the criterion NEFA+IGF-1. Using this, the classification was matching in 27 animals. Meaningful conclusions about the relation between adaptive, health and liver status could be made on the basis of NEFA- and NEFA+IGF-1-classification. In the "AP-ltd" animals (NEFA; n=17 and NEFA+IGF-1; n=13), increased GLDH activities (p<0.05) and reduced leukocyte numbers (p<0.001) were determined. No differences were detected for neutrophil numbers, oxidative stress and concentration of Hp. In conclusion, routine determination of IGF-1 seems not justified to determine adaptive status. Instead, NEFA values >0.5 mM during the first wk of lactation were considered as the most suitable parameter for identifying limited adaptive performance. [ABSTRACT FROM AUTHOR]

Expression of Hp mRNA, one major acute phase protein in cattle, was detected in homogenates of the bovine mammary gland. The aim of this study was to localize Hp mRNA expression within the udder at the cellular level and to quantify any difference of the level of this expression caused by two major mastitis pathogens. For this purpose 3 quarters of each of 3 cows were subsequently inoculated with Escherichia coli (E. coli) at 6, 12 and 24 h pre-slaughter, the 4th quarter received saline 24 h pre-slaughter as control. Another 3 cows received Staphylococcus aureus (S. aureus) accordingly. After slaughter, tissue samples of each quarter were collected for analyses by in situ hybridization (ISH) and real-time RT-PCR. ISH allocated Hp mRNA expression to the alveolar epithelium of the mammary gland. In addition, evaluating the number of cells expressing Hp mRNA revealed a significant difference between the 4 quarters treated with E. coli (P<0.05) in contrast to the quarters exposed to S. aureus. A 17-fold rise in the number of epithelial cells expressing Hp in mammary tissues was detected during the course of E. coli infection, whereas Hp mRNA expression in response to S. aureus infection appeared unchanged. This divergence was confirmed by quantitative real-time RT-PCR: in contrast to S. aureus infected animals, Hp mRNA expression differed significantly between the quarters of E. coli infected animals (P<0.05). In the latter a 176-fold increase was observed from 0 to 24 h. In summary, this is the first study reporting the localization of Hp mRNA in mammary epithelium of cows. The lack of response to S. aureus within the first 24 h after infection is in contrast to E. coli infection and possibly highlights pathogen-species dependent modulation of the host's immune defense in the udder [ABSTRACT FROM AUTHOR]

This study examined the effect of plane of nutrition on the endocrinological regulation of the hypothalamic-pituitary-ovarian (HPO) axis in beef heifer calves during a critical sexual developmental window early in calf hood. Forty Holstein-Friesian × Angus heifers (mean age 19 d, SEM = 0.63) were assigned to a high (HI; ADG 1.2 kg) or moderate (MOD; ADG 0.50 kg) nutritional level from 3 to 21 wk of life. Intake was recorded using an electronic calf feeding system, BW was recorded weekly, and blood samples were collected on the week of age 5, 10, 15, and 20 for metabolite, reproductive, and metabolic hormone determination. At 19 wk of age, on sequential days, an 8-h window bleed was carried out for luteinizing hormone (LH), follicle-stimulating hormone (FSH), and estradiol analysis. To characterize anterior pituitary gland function, an intravenous GnRH challenge was conducted (19 wk of age). Blood was collected via a jugular catheter every 15 min for 135 min for the analysis of LH, FSH, and estradiol. Calves were subsequently euthanized at 21 wk of age; the anterior pituitary, metabolic organs, and reproductive tract were weighed, and ovarian surface follicular numbers and oocytes recovered were recorded. Mean ADG was 1.18 and 0.50 kg for HI and MOD, respectively, resulting in a 76.6-kg difference in BW (P < 0.001). Blood insulin, glucose, and IGF-1 concentrations were greater (P < 0.001) for HI compared with MOD. There was a diet × time interaction for leptin (P < 0.01); concentrations were greater in HI compared with MOD at 20 wk of age with no difference between treatments before this. Dietary treatment did not alter the concentrations of adiponectin or anti-mullerian hormone. There was a diet × time interaction for FSH, whereby MOD had greater concentrations than HI at 10, 15, and 20, but not at 5 wk of age. Over the duration of an 8-h window bleed (19 wk of age), serum concentrations of LH, LH pulse frequency, and LH pulse amplitude were unaffected by treatment, whereas FSH (0.23 vs. 0.43 ng/mL) and estradiol (0.53 vs. 0.38 ng/mL) concentrations were less than and greater, respectively, for HI than MOD (P < 0.05). Likewise, following a GnRH challenge, the area under the curve analysis revealed greater (P < 0.01) estradiol and lesser (P < 0.01) FSH concentrations in calves on the HI relative to MOD diet, whereas concentrations of LH were unaffected (P = 0.26) between treatments. Ovarian surface follicle numbers were greater (P < 0.05) in HI compared with MOD. Total reproductive tract, uterus, and ovarian tissue expressed relative to BW were greater (P < 0.05) for HI compared with MOD. In conclusion, enhanced nutrition in early calfhood advances the ontogeny development of the HPO axis., (© The Author(s) 2020. Published by Oxford University Press on behalf of the American Society of Animal Science. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)