A.R Rabiee

The effect of level of feed intake on progesterone clearance rate by measuring faecal progesterone metabolites in grazing dairy cows

The objective of the present study was to determine the effect of level of feed intake of pasture on P4 clearance rates in dairy cows. Twelve non-lactating Holstein-Friesian cows aged 4-9 years were randomly allocated to a restricted or ad libitum group. The ad libitum group had unrestricted access to irrigated pasture, whereas the restricted group had access for only 2h per day. Each animal was drenched orally twice daily with a chromic oxide capsule to allow daily feed intake to be estimated from faecal output (FO). Endogenous progesterone (P4) production was eliminated by subcutanously implanting a capsule containing 6 mg of a potent GnRH-agonist (deslorelin) into the ear of each animal 3 weeks before inserting a CIDR device containing 1.9 g P4 into the vagina. Two luteolytic PGF2alpha were given 10 days later. Each device was removed after 11 days and residual P4 measured. Daily plasma samples were assayed for P4. Faecal samples were also taken daily and assayed for pregnanes (FP4M) containing a 20-oxo-, a 20alpha- or a 20beta-OH group with EIAs. The average daily dry matter (DM) intake of pasture was higher for cows in the ad libitum group (15.9 versus 6.3 kg DM, P=0.001). Their plasma P4 concentrations were lower (1.08 versus 1.71 ng/ml, P=0.05), even though the average residual P4 content of the used CIDR devices was not affected by feed intake (1.20 versus 1.25 g, P>0.05). The concentrations of FP4M were not affected by level of feed intake (20-oxo-: 3.3 versus 1.7, 20alpha-: 3.5 versus 3.7, 20beta-: 2.1 versus 3.2 microg/g DM). Daily excretion rates of 20-oxo- and 20alpha- were higher in ad libitum cows (20-oxo-: 17.8 versus 4.3mg per day, P=0.05; 20alpha-: 18.2 versus 8.9 mg per day, P=0.001), but daily yield of faecal 20beta- was not affected by feed intake (11.9 versus 8.6 mg per day, P=0.5). These results show that there was a negative relationship between feed intake and plasma P4 concentrations in these CIDR-treated GnRH-downregulated Holstein cows. Concentrations of FP4M were not affected by level of feed intake or FO, but daily excretion rate of FP4M was associated with the volume of faeces.

Uptake of glucose and cholesterol by the ovary of sheep and cattle and the influence of arterial LH concentrations

Time series analysis methods were used to evaluate the relationships between the uptake of glucose and cholesterol, and arterial luteinizing hormone (LH) concentrations. Classical arterio-venous difference methods were applied to study ovarian uptake of metabolites. Arterial and venous samples (n=20) were obtained from six cows and nine sheep every 10min. There were highly significant positive cross-correlations of 0.5 for cattle and 0.8 for sheep between the uptake of glucose and cholesterol at lag 0. All individual cross-correlations were significant for sheep. Uptake of these metabolites was not significantly associated with arterial LH concentrations in the cows. This study suggests that glucose may promote cholesterol uptake into the ovarian cells or vice versa. This study is the first to identify such a relationship. If these findings are repeated, the possibility exists that control of the oestrous cycle and fertility may be achieved by seeking a common regulator of uptake of these metabolites or by uncoupling the association between glucose and cholesterol.

Progesterone clearance rate in lactating dairy cows with two levels of dry matter and metabolisable energy intakes.

The aim of these studies was to determine the effect of levels of dry matter (DM) and metabolisable energy (ME) intakes on clearance rate of progesterone (P4) in dairy cows. Thirty-two lactating Holstein-Friesian cows were selected for the study and were fed indoors in individual stalls for a period of 5 weeks. They were individually offered a diet of combinations of pasture, hay and pelleted cereal grain to achieve two different levels of DM and ME. In the first trial, 16 cows were allocated to two groups: (i) high DM (HDM), and (ii) low DM (LDM) intakes, while the amount of ME intake was constant. In the second trial, 16 cows were allocated to two groups: (i) high ME, and (ii) low ME intakes with similar amount of DM intake. A GnRH-agonist (deslorelin) was initially implanted in the ear of each cow to block endogenous P4 secretion. Then 3 weeks later, a CIDR device was inserted into the vagina of each cow and left in place for 11 days. Chromic oxide (Cr(2)O(3)) capsules were administered to allow daily faecal output (FO) to be estimated. Daily blood, faecal and milk samples were taken during the period of the experiment for P4 and faecal P4 metabolites analyses. Trial 1: The average milk yield was similar among cows in high and LDM intake groups (26.7 versus 25.0 l per day, P = 0.2). The average daily FO was 7.8 kg DM in the HDM and 5.7 in the LDM cows (P < 0.0001). Average daily DM intakes were 17.3 kg and 15.4 kg in the HDM and LDM groups, respectively (P < 0.0001). The average plasma P4 concentrations were similar between the two groups (1.56 versus 1.60 ng/ml, P = 0.7) but milk P4 concentrations were higher in LDM cows (4.6 versus 3.6 ng/ml, P = 0.02). The average daily excretion rate of P4 into the milk was higher in LDM cows (122.3 versus 88.5 microg, P = 0.002). The concentrations of faecal P4 metabolites (FP4M) were not influenced by the level of daily DM intake (2.85 versus 2.90 microg/g, P = 0.6). The average daily yields of FP4M were higher among cows in the HDM group (23.2 versus 16.3mg, P = 0.01). Trial 2: The average milk yield was 31.2l per day in HME cows compared to 25.0l per day in LME cows (P < 0.0001). The average daily FO was 7.8 kg DM in LME and 5.8 kg DM in HME cows (P < 0.0001), and the average DM content of faeces was higher in LME cows (15.8 versus 12.7%, P = 0.01). The average daily ME intake was 213MJ per day in HME group compared to 183MJ per day in LME group (P<0.0001). The average plasma and milk P4 concentrations were similar between the two groups (plasma P4 = 1.54 versus 1.56 ng/ml, P = 0.4; milk P4: 3.7 versus 3.6 ng/ml, P = 0.6). The average daily excretion rate of P4 into the milk was higher in HME cows (114 versus 88.5 microg, P = 0.03). Concentrations of FP4M were not influenced by the level of daily ME intake (2.5 versus 2.85 micro g/g, P = 0.08). However, daily yields of FP4M were greater in the LME group (23.2 versus 14.4 mg, P = 0.01). In conclusion, this study was unable to establish a relationship between the level of DM and ME in the diet with the excretion rates of FP4M metabolites and plasma P4 concentrations.

Effects of level of feeding and progesterone dose on plasma and faecal progesterone in ovariectomised cows

The effects of two levels of feeding and two doses of progesterone (P4) on plasma and faecal progesterone metabolites (FP4M) were studied using a total of 24 ovariectomised (OVX), non-lactating, Holstein-Friesian cows. Cows were grazed on improved ryegrass/white clover pastures and allowed ad libitum access to pasture or were restricted to grazing for a total of 4 h per day in two 2 h periods. Progesterone (P4) was administered as one or two, simultaneous, intravaginal progesterone devices (CIDR). The cows were adapted to their pasture supply for 2 weeks before the start of the progesterone treatments. The progesterone devices were administered for 11 days and the cows were dosed with slow release chromic oxide capsules during the P4 treatment to allow faecal output (FO) to be estimated. Daily blood samples for P4 assay and weekly samples for blood metabolite assay were collected. Faecal samples were collected per rectum daily and assayed for pregnanes containing a 20-oxo-, 20alpha- or a 20beta-OH group by enzyme immunoassay (EIA). Daily FO was higher (P < 0.001) for ad libitum than pasture restricted cows (6.3 vs 4.1 kg DM) but was similar for both doses of P4. The average mass of P4 released from a CIDR device over a 11-day period was higher for cows allowed ad libitum pasture compared with those on restricted pasture (0.64 vs 0.60 g; P = 0.04). Plasma P4 concentrations, however, were higher in restricted than ad libitum fed cows (1x CIDR: 1.81 vs 1.41 ng/ml; 2x CIDR: 4.10 vs 3.46 ng/ml). Increasing the progesterone dose significantly (P < 0.001) increased both the concentrations and daily totals of the faecal pregnanes assayed and total FP4M. Restricted pasture cows had higher (P < 0.001) pregnanes and FP4M concentrations than cows fed ad libitum. Daily total faecal pregnane and FP4M did not differ between feeding levels except for faecal 20alpha-pregnane which was highest for ad libitum fed cows (P < 0.05). These results showed that the plasma concentrations of P4 in CIDR-treated OVX cows were negatively associated with the level of feeding. Level of feeding and dose of P4 affected the concentrations of FP4M, but the daily excretion rate of FP4M was not positively influenced by the level of feeding.

Progesterone metabolism in ovariectomised non-lactating Holstein–Friesian cows treated with progesterone with two levels of feed intake

The goal of this study was to measure the effects of level of feeding and the form of progesterone (P4) administration on the concentrations and yields of faecal P4 metabolites relative to differences in plasma P4 concentrations in non-lactating cows. Six non-lactating Holstein-Friesian cows were ovariectomised (OVX) and allocated to two groups: (i) P4 by subcutaneous injection (P4-s.c., n=3); and (ii) P4 administration per vaginum (P4-p.v., n=3). Each cow in the P4-s.c. group was injected subcutaneously once daily with 200mg P4. Each cow in the P4-p.v. group had a CIDR device inserted for 11 days when it was removed and replaced with a second device for further 11 days. Cows were fed a ration containing lucerne (33%) and oaten (66%) chaff at a maintenance level (M) in two portions in the first period of the study, and at a half-maintenance (1/2M) level during the second period. Chromic oxide capsules (Cr(2)O(3)) were administered twice daily to allow faecal output (FO) to be estimated. Plasma P4 and faecal P4 metabolites (FP4M; 20-oxo-pregnanes, 20alpha- and 20beta-OH-pregnanes) were measured during the treatment period. Daily FO declined after reducing the M diet to 1/2M (4.77 versus 2.61kg; P<0.01), whereas plasma P4 concentrations increased in the P4-s.c. group (4.2 versus 6.2ng/ml; P<0.05), but not in the P4-p.v. group (0.9 versus 1.0ng/ml; P>0.2). The mass of P4 released from a CIDR device during each 11-day period (M or 1/2M) was similar (0.66 versus 0.63g). Faecal 20-oxo-pregnanes (20-oxo-) concentrations were not affected by day or level of feeding, whereas faecal 20alpha-OH (20alpha-) and 20beta-OH (20beta-) concentrations were increased with the 1/2M diet in the P4-s.c. group (4.3 versus 5.6 microg/gDM; 2.2 versus 5.6 microg/gDM, respectively; P<0.05), but not in the P4-p.v. group (2.3 versus 2.7 microg/gDM; 1.7 versus 3.04 microg/gDM P>0.05). These changes in concentration only partly compensated for the reduced FO with the 1/2M diets as daily yields of FP4M (20-oxo- and 20alpha-) were greater during the M diet period (20-oxo-: 6.9 versus 4.1 microg/gDM; 2.7 versus 1.5 microg/gDM, for P4-s.c. and P4-p.v. groups, respectively; P<0.05, 20alpha-: 19.9 versus 13.6 microg/gDM; 10.9 versus 6.6 microg/gDM for P4-s.c. and P4-p.v. groups, respectively; P<0.05). The level of feeding and the route of P4 administration had key roles in controlling P4 concentrations in blood and daily FP4M yield.

Plasma, milk and faecal progesterone concentrations during the oestrous cycle of lactating dairy cows with different milk yields

The hypotheses tested in this study were that neither average progesterone (P4) concentrations in plasma and milk nor average progesterone metabolites concentrations in faeces would differ during an oestrous cycle in two groups of cows with differing daily milk yields. High producing (HP = 8) and low producing (LP = 8) dairy cows were selected randomly for the study. Their oestrous cycles were initially synchronised using P4 and prostaglandin F2alpha. Chromic oxide capsules were administered twice daily to measure total faecal output. Samples of blood, faeces and milk were taken daily throughout one oestrous cycle, plasma and milk P4, and faecal progesterone metabolites (FP4M) assayed. The average daily milk yields in the two groups were 30.8 and 21.9l per day, respectively (P < 0.0001), although daily faecal output was similar in both the groups (HP, 7.7 versus LP, 6.9 kg DM; P = 0.24). Mean plasma and milk P4 concentrations were similar in both the groups (plasma P4, 4.12 versus 4.05 ng/ml; P = 0.3; milk P4, 8.2 versus 8.3; P = 0.9) during dioestrus. Average daily excretion of P4 to the milk was greater in HP than LP cows (252 versus 185 microg, P = 0.04). Neither concentration nor the daily yield of FP4Ms was affected by level of milk yield (concentration: 12.2 versus 11.5 microg/g; daily yield: 89.1 versus 82.9 mg per day; P > 0.05). These data showed that the concentrations of P4 in plasma and milk, and the concentrations and daily yields of FP4M were not affected by the level of daily milk yields which differed by about 41% of the LP average of 21.9l.

Blood metabolite profile in Holstein-Friesian cows fed diets varying in dry matter and metabolizable energy density during early lactation

Dietary effects on circulating concentrations of some blood metabolites were assessed in Holstein-Friesian cows in early lactation. Thirty-two lactating cows were randomly assigned to receive four diets differing in dry matter intake (DMI) and metabolizable energy (ME) density, namely low dry matter and metabolizable energy (LL), low dry matter and high metabolizable energy (LH), high dry matter and low metabolizable energy (HL), high dry matter and high metabolizable energy (HH), and concentrations of some blood metabolites determined. At the end of the 5-week study, the level of insulin-like growth factor-I (IGF-I) was higher (P < 0.001) in cows on diet HH than those on diets HL, LH, or LL. The glucose concentration was higher (P < 0.001) in cows on HH and LH than those on HL and LL diets, while those of non-esterified fatty acid (NEFA) were similar in cows on the four dietary treatments. Cows fed HL and LL diets recorded higher (P < 0.001) beta-hydroxybutyrate (BHB) concentrations than those on the HH or LH diets. Urea concentration was higher (P < 0.001) in cows on LL than that of their counterparts on the other diets. IGF-I was positively correlated (P < 0.01) with glucose, but negatively related with BHB (P < 0.01) and urea (P < 0.05). Glucose was negatively correlated with BHB (P < 0.01) and urea (P < 0.05). NEFA was negatively correlated with urea (P < 0.05) while BHB was positively correlated with urea (P < 0.01). The levels of metabolites in the blood can reflect the nutritional status of cows during early lactation.