N OCIETY' - the Society for Reproductive Biology

Effect offeeding management on progesterone release from CIDR devices inovariectomised dairy cowsA.R. Rabieet, K.L. Macmillan! and MJ. Rathbone 2IDepartment of Veterinary Science, University of Melbourne, 250 Princess HWY, Werribee, VIC, Australia2InterAg, 558 Te rapa Road, P.O. Box 20055, Hamilton, New ZealandIntroduction:The effects of nutrition on progesterone production andclearance rates in dairy cattle have not been intensivelystudied. The early postpartum period in cattle ischaracterized by anovulatory anoestrus. The duration ofanoestrus can be affected by body condition andnutritional intake. Progesterone administrated pervagina (CIDR device) has been widely used to treat thiscondition in dairy cattle (1). The efficacy of thistreatment when using a CIDR device partly depends onthe rate of progesterone released from the device (2). Itis not known whether environmental factors such asnutrition and housing can affect the profile ofprogesterone release from a CIDR device. This studywas conducted to determine the possible effect of someof these factors on progesterone release from a CrDRdevice in dairy cows.Materials and Methods:Six non-lactating Holstein-Friesian cows wereovariectomised. Plasma and faecal progesteroneconcentrations were measured for 4 weeks to monitorcomplete clearance of progesterone from the animaltissues following the operation. A CIDR device (1.9gprogesterone) was inserted into the vagina of each cowat least 4 weeks after ovariectomy and left in place for11 days. In the first II-day period of study cows werehoused in individual pens and fed with lucerne andoaten chaff (Table 1). In the second period, they weregrazed on mixed pasture (2 pastures, Table 1). Theinterval between the two periods was 4 weeks. Bloodsamples were taken daily for 11 days and progesteroneconcentrations were measured using RIA. A Soxhletextraction technique was used to determine the residualamount of progesterone in spent CIDR devicesfollowing insertion in the animal (2).Results and Discussion:The only difference in the diets fed in the two periodswas the higher dry matter content of the lucerne andoaten chaff in the first period (P = 0.001; Table 1).Plasma progesterone concentrations (1.18 ± 0.17 vs1.74 ± 0.34) and the amount of progesterone releasedfrom the CIDR devices (0.64 ± 0.04 vs 0.88 ± 0.04)were significantly lower during the period where cowswere confined and fed with lucerne and oaten chaff (P= 0.02, Fig. 1). These differences may have beenassociated with diet or with housing. Factors whichmay affect the amount ofprogesterone that is releasedfrom a device could include the rate of blood flow tothe anterior part of vagina, frequency of defaecation,composition and physical form of the diet. Althoughthere was not a significant difference in thecomposition of the diet, 'physical form and passage rateoffaeces in confined cows may have altered the contactbetween CrDR device and the vaginal wall therebyaltering the effective surface area for release. Bloodmetabolites and protein could also affect vaginalenvironment. However, the lack of physical activitywith confinement may also have altered the frequencyor pattern of contact of the device with the vaginalmucosa and consequently reduced the amount ofprogesterone released from a device.Table 1: Nutritional values of the dietsDM 1 CP 2 Digestibility ME 3Lucerne & 86.4 12.5 64.2 8.9oaten ChaffMixed 41.4 12 61.0 8.5pasture1 Dry Matter 2 Crude Protein 3 Metabolisable Energy2.5GICE 1.5.!!~e 1Il..0.5ChaffPastureFigure 1: Plasma P4 and progesterone released fromCIDR devicesReferences:1) Macmillan KL and Burke CR (1996) Anim. Reprod.Sci. 42: 307-3202) Rathbone MI, et al. (1998) Proceedings of theInternational Symposium on Controlled Release ofBioactive Materials, 25: 249-250.Effect of nutrition on plasma progesterone concentrations in ovariectomiseddairy cows treated with progesteroneA.R. Rabiee and K.L. Macmillan1Department of Veterinary Science, University of Melbourne, 250 Princess HWY, Werribee, VIC, AustraliaIntroduction:Regulatory mechanism controlling luteal function andplasma progesterone (PP4) levels during the postpartumperiod have an important role in the dairy cattlefertility. The metabolic clearance rate (MCR) ofprogesterone also determines the relationship betweenprogesterone production rate and plasma concentration(1). The inverse relationship between feeding level andconcentrations of plasma progesterone (PP4) wasattributed to differences in clearance rate ofprogesterone rather than to changes in hormoneproduction (2). It is proposed that the mechanism forcontrolling PP4 was MCR of progesterone rather thanproduction rate. In the present study, an external sourceof progesterone was administrated and plasmaprogesterone concentrations were measured toinvestigate the effect of the level of feeding on plasmaprogesterone (PP4) in cows which received twodifferent forms ofprogesterone treatment.Materials and Methods:Six non-lactating Holstein-Friesian cows, which hadbeen previously ovariectomised, were allocatedrandomly into two groups: P4 by subcutaneousinjection (P4-s.c.) and P4 administration per vagina(P4.;p.v.). Cows in the P4-s.c. group received a dose of200mg progesterone Iday as in a single injection. Thosein P4-p.v. group, each had a CIDR device containing1.9g progesterone inserted per vagina for 11 days. Eachdevice was replaced with a new one after 11 days.Cows were housed in individual pens and fed withlucerne and oaten chaff. In the fITst period of the study,cows were fed a maintenance ration twice daily in themorning and afternoon, and offered on an individualbasis. In the second period, the entire procedure (partone) was repeated, but cows were fed half of the feedrelative to their requirements. Blood samples werecollected twice daily at 8.00h and 16.00h for 11 daysand progesterone concentrations were measured usingRIA.Results and Discussion:The level of feeding had a significant effect on plasmaprogesterone concentrations in the P4-s.c., but not inthe P4-p.v. group (Figure 1). Plasma progesterone wasnot significantly affected by day, time of sampling orany of the interactions (P > 0.05). Faecal outputsignificantly declined after reducing the maintenance(M) ration to V2 M (Table 1). There was no significantdifference in the mass of progesterone released from aCIDR device during the M or Yz M periods (0.66 vs0.63 g). Other studies (2,4) have also shown thatprogesterone MCR significantly increased with anincrease in feed intake from Yz M to 2M, or from % Mto M; but not from Yz M to M in intact or CIDR-treatedewes. It has been suggested that there is a directrelationship between the level of feed intake and rate ofblood flow to the liver and gut, and consequentlyprogesterone clearance rate (3). Studies in cattle (5)also showed that the frequency of feeding had asignificant role on peripheral progesteroneconcentrations. Several factors may affect plasmaprogesterone concentration, including the difference inprogesterone release rate. The difference in response tothe level of feeding between two groups may be due tothe form that progesterone was administrated. The dailydose of progesterone injection and release rate ofprogesterone in the P4-s.c. group was greater than inthe P4-p.v. group. This may have influenced the MCRrate of progesterone. These data demonstrate that thelevel of feeding and the route of progesteroneadministration have a key role in controlling plasmaprogesterone levels.Table 1: Mean (± SE) of feed intake and faecal outputduring the periods of M and Y2 M in both groups ofcows7~6~ 5 m:l1/2 M.sc:eQ) 43*Ql2~a. 10P 4 'pvP4-s.c.P 4 -s cP4-p.v.Feed intake (KgDM) (KgDM)M 11.86 ± 0.43 11.62 ± 1.30V2M 5.91+ 0.24 5.80 ± 0.62Faecal outputM 4.64± 0.09 4.9 ± 0.18Y2M 2.65 + 0.07 2.56 ±0.19Figure 1: plasma progesterone concentrations in P4-s.cand P4-p.v cowsReferences:1) Tait JF (1963) J. Clin. Endocr. 23: 1285.2) Parr RA et al. (1987). J. Reprod. Ferti!. 80: 317­320.3) Parr RA (1992) Reprod. Ferti!. Dev. 4: 297-300.4) Williams AH and Cumming IA (1982). J. Agric.Sci. 98: 517-522.5) Vasconcelos JLM et al. (1998) ADSA-ASAS jointmeeting.120 121