Response to kisspeptin and gonadotropin-releasing hormone agonist administration in Holstein-Friesian dairy heifers with positive or negative genetic merit for fertility traits.

Previous research has identified that Holstein-Friesian dairy heifers with positive (POS) genetic merit for fertility traits (FertBV) reach puberty earlier than heifers with negative (NEG) FertBV. The hypothalamus-pituitary-gonadal (HPG) axis is functional in heifers before the onset of puberty, with increased LH release evident as heifers progress toward puberty. We investigated the functionality of the HPG axis in peripubertal Holstein-Friesian dairy heifers with divergent POS or NEG FertBV, hypothesizing that the earlier puberty onset of POS heifers is associated with earlier activation of the HPG axis than in NEG heifers. In experiment 1, we tested the dose responsiveness of POS heifers to an intravenous injection of either kisspeptin [Kiss; 2, 4, or 8 µg/kg of body weight (BW); n = 3 per dose] or a GnRH agonist (buserelin; 5, 10, or 20 ng/kg of BW; n = 3 per dose). The use of these 2 agonists investigates the status of the HPG axis in both the hypothalamus (Kiss) and pituitary (buserelin) glands. Doses of 4 µg/kg BW of Kiss and 10 ng/kg BW of buserelin produced submaximal LH responses and were used in experiment 2, in which previously unused POS (n = 22) and NEG (n = 18) FertBV heifers were challenged with both agonists at 10 and 12 mo of age in a partial crossover design. Heifers were randomly allocated to treatment groups, balanced for age and BW. The LH response to buserelin was greater in POS heifers than NEG heifers at 10 mo of age, with no difference in response at 12 mo. The FSH response to buserelin and the LH and FSH responses to Kiss did not differ between the POS and NEG heifers at either age. These results indicate an association between divergent genetic merit for fertility and the LH release to buserelin at 10 mo of age, supporting the hypothesis that gonadotropin responsiveness to a GnRH agonist is more advanced in POS heifers than in NEG heifers.

Development of an intrauterine infection model in the postpartum dairy cow.

AIMS: To develop an intrauterine infection model for Trueperella pyogenes in postpartum dairy cows and to assess the effect of this infection on the degree of intrauterine inflammation and concentrations of progesterone in serum. METHODS: The oestrous cycles of 36 healthy, non-pregnant, postpartum dairy cows were synchronised. They were then treated by intrauterine infusion of 0.5 g cephapirin before being blocked by age and randomly assigned to treatment with intrauterine infusion of saline (n = 18), 107 (n = 9) or 109 (n = 9) cfu of T. pyogenes, approximately 4 days after the expected time of ovulation (Day 0). Prior to intrauterine infusion on Day 0 and again on Days 3, 7, 10, and 15, cytobrush samples were collected from the uterus of each cow for microbiology and assessment of the percentage of polymorphonuclear neutrophils (PMN%). Blood samples were collected on the same days for measurement of concentrations of progesterone in serum, and uterine lumen diameter was assessed daily using transrectal ultrasonography. RESULTS: Trueperella pyogenes was isolated from 5/18 (28%), 7/9 (78%) and 8/9 (89%) cows infused with saline, 107 or 109 cfu of T. pyogenes, respectively (p < 0.001). Mean PMN% in the control cows did not change over time (p > 0.05), whereas it was higher on Days 7 and 10 than Day 0 in the 107 cfu group, and higher on Days 3 and 10 than Day 0 in the 109 cfu group (p < 0.05). The percentage of observations with uterine lumen diameters >2 mm was higher in cows infused with 107 (29.3 (95% CI = 14.5-44.2)%) or 109 cfu (19.2 (95% CI = 7.0-31.5)%) than in control cows (3.1 (95% CI = 0.1-6.0)%) (p < 0.001). Mean concentrations of progesterone in serum were higher in cows infused with 107 cfu (2.01 (SE 0.19) ng/mL) than cows infused with 109 cfu (1.01 (SE 0.27) ng/mL), with the control group intermediate (1.41 (SE 0.19) ng/mL) (p = 0.03). CONCLUSIONS: Infusion of 107 or 109 cfu of T. pyogenes resulted in the establishment of intrauterine infection in 83% of cows. Infection resulted in increased uterine lumen diameter, and an inflammatory response, i.e. elevated PMN%. CLINICAL RELEVANCE: This intrauterine infection model may be useful for future research on, for example, the pathogenesis of intrauterine infection in postpartum dairy cows.

The microenvironment of ovarian follicles in fertile dairy cows is associated with high oocyte quality.

We hypothesised that heifers and cows with positive genetic merit for fertility would have a follicular microenvironment that resulted in better quality oocytes. To test this, we compared cumulus cell-oocyte complexes (COC) and follicular fluid from preovulatory follicles of 36 Holstein-Friesian nulliparous heifers and 50 primiparous lactating cows with either positive (POS, +5%) or negative (NEG, -5%) fertility breeding values (FertBV). Established gene markers of oocyte quality were measured in individual cumulus cell masses and oocytes, and concentrations of amino acids, steroids, and metabolites were quantified in corresponding follicular fluid and plasma. The timing of visually detectable oestrus in NEG FertBV heifers was inconsistent with their stage of COC maturation. Retrospective analyses of oestrous activity data indicated that NEG FertBV heifers were sampled earlier. Their recovered COC were morphologically less mature and exhibited differential expression of genes that are associated with follicular maturation (lower levels of BMPR2) and protein processing (higher levels of HSP90B1). Despite consistent sampling times being achieved in the lactating cows, lower concentrations of serine, proline, methionine, isoleucine, and non-esterified fatty acids were present in follicular fluid from POS FertBV cows. This was associated with higher expression of gene biomarkers of good oocyte quality (VCAN, PDE8A) in COC recovered from POS FertBV cows. This study supports our hypothesis that the follicular microenvironment in lactating dairy cows with high genetic merit leads to COC with higher metabolic rates and oocytes of superior quality. Moreover, an additional stressor such as lactation is required for this difference to be pronounced.

Estrous activity in lactating cows with divergent genetic merit for fertility traits.

This observational study aimed to determine the effect of genetic merit for fertility traits on estrous expression and estrous cycle duration in grazing dairy cows, as measured by an activity monitoring device. A secondary aim was to describe changes in expression of estrus that occur during successive estrous cycles postpartum. Neck-mounted, activity-monitoring devices (Heatime, SCR Engineers Ltd.) were fitted to nulliparous Holstein-Friesian heifers with positive (POS FertBV) or negative genetic merit for fertility traits (NEG FertBV) to capture activity data during their first and second lactations (POS FertBV: n = 242, n = 188; NEG FertBV: n = 159, n = 87 in lactation 1 and 2, respectively). An estrous event was identified when the activity change index exceeded 26 activity units (AU) for 4 h. A total of 1,254 and 892 estrous events were identified in lactation 1 and 2, respectively. Estrous duration was defined as the interval between when the threshold was first exceeded and when activity dropped below the threshold, with no new event starting within 24 h of the end of the previous event. This definition of estrus included cows in which activity crossed the threshold multiple times in a day and were classified as a single estrous event. A second measure, high activity duration, was defined as the total hours that activity exceeded the threshold. To characterize estrous activity, peak activity (above baseline) and total activity (area under the curve of activity above baseline) were measured. Compared with NEG FertBV cows, POS FertBV cows had more active, longer estrous events. In lactation 1, the POS FertBV group had a mean estrous duration and a high activity duration of 12.5 and 12.4 h compared with 11.4 and 11.3 h for the NEG FertBV group [standard error of the difference (SED) = 0.5 and 0.4 h, respectively]. This significant difference also occurred in lactation 2, with a mean estrous duration of 13.1 versus 11.8 h (SED = 0.5 h) and a high activity duration of 13.0 versus 11.8 h (SED = 0.4 h) in the POS and NEG FertBV groups, respectively. Total activity and peak activity were greater in the POS compared with the NEG FertBV group in lactation 1 (peak activity: 65.5 vs. 55.8 AU, SED = 2.4 AU; total activity: 588 vs. 494 AU, SED = 25 AU) and lactation 2 (peak activity: 72.5 vs. 61.2 AU, SED = 2.9 AU; total activity: 648 vs. 541 AU, SED = 30 AU). Estrous cycle duration did not differ between the POS and NEG FertBV groups (lactation 1: 20.4 vs. 20.6 d, SED = 0.25; lactation 2: 20.8 vs. 21.0 d, SED = 0.28). Less estrous activity of the cow was associated with the first postpartum estrus. In contrast, the number of previous estrous events did not consistently affect the duration of the subsequent estrous cycle. The outcomes of this study provide evidence that positive genetic merit for fertility traits is associated with more overt estrous expression. Selection for these traits may improve estrous expression and thus estrous detection in commercial herds.

Antineoplastic ether-linked phospholipid induces differentiation of acute myelogenous leukemic KG-1 cells into macrophage-like cells.

The culture of a human acute myelogenous leukemic cell line (KG-1) with a synthetic ether-linked phospholipid: 1-0-octadecyl-2-0-methylglycerol phosphocholine (ET-18-OCH3), suppressed the growth of the KG-1 cells while the variant subline, (KG-1a cells) similarly treated was unresponsive. The growth inhibition of the KG-1 cells was accompanied by morphological changes into cells of the monocyte/macrophage lineage. Histochemically, the ET-18-OCH3-treated KG-1 cells increase 17-fold in the nonspecific esterase activity when compared to control non-treated cells, whereas they responded negatively in the assay for the reduction of soluble nitroblue tetrazolium into insoluble blue formazan deposits (a marker for cells of the granulocytic lineage). Taken together, our data revealed that the synthetic ether-lipid inhibited the growth of the KG-1 acute myelogenous leukemic cells while inducing the differentiation of these cells into cells of the monocyte/macrophage-lineage. These effects of the synthetic ether lipid raise the possibility that naturally occurring ether-linked phospholipids may likewise function in vivo to modulate hyperproliferative processes and thus warrant further explorations.