J anim sci 1995-espinoza-2888-92


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J anim sci 1995-espinoza-2888-92

  1. 1. Effects of calcium soaps of fatty acids on postpartum reproductive activity in beef cows and growth of calves J. L. Espinoza, J. A. Ramirez-Godinez, J. A. Jimenez and A. Flores J ANIM SCI 1995, 73:2888-2892.The online version of this article, along with updated information and services, is located on the World Wide Web at: http://jas.fass.org/content/73/10/2888 www.asas.org Downloaded from jas.fass.org by guest on August 18, 2011
  2. 2. Effects of Calcium Soaps of Fatty Acids on Postpartum Reproductive Activity in Beef Cows and Growth of Calves1 J. L. Espinoza2, J. A. Ramirez-Godinez3, J. A. Jimenez, and A. Flores ´ Facultad de Zootecnia, Universidad Autonoma de Chihuahua, Perif. ´ Francisco R. Almada Km. 1, Apdo. Postal 4-28, C.P. 31031, Chihuahua, Chih. MexicoABSTRACT: Beef cows were used to determine the respectively). A similar tendency was observed ininfluence of calcium soaps of fatty acids (CSFA) body condition scores in the same postpartum periodsincorporated in a range supplement on postpartum (4.1 vs 3.4, P < .01 and 3.6 vs 2.5, P < .01 for M and C,reproductive characteristics and growth of calves. respectively). Concentrations of total cholesterol,Cows were assigned randomly to receive 0 (C, n = 68) high-density lipoprotein cholesterol, low-densityor 125 g/d of CSFA (M, n = 66). Diets were lipoprotein cholesterol, very-low-density lipoproteinisonitrogenous (23%) and were used during 105 d, cholesterol, and triglycerides were greater ( P < .01) inbeginning at 61 ± 36 d (range) precalving. Two blood M than in C cows. Percentage of cycling (progesteronesamples were collected monthly (7-d intervals). > 1 ng/mL) cows at 30 to 90 d postpartum was 38% inWeights of calves at 35, 50, and 90 d of age andweaning weight adjusted to 200 d of age were greater M and 22% in C ( P < .02). Percentage of pregnantin M than in C (46.8 vs 43.8 kg, P < .05; 56.0 vs 50.6 cows during the first half of the breeding season waskg, P < .01; 98.8 vs 91.8 kg, P < .01; and 186 vs 173 kg, greater ( P < .02) in M (62.5%) than in C cowsP < .01, respectively). Body weights at 35 and 50 d (35.5%). We concluded that CSFA incorporated in apostcalving were greater in M than in C cows (334 range supplement during pre- and postpartum periodsand 310 kg, P < .01; 329 and 300 kg, P < .01, improved reproductive efficiency and growth of calves. Key Words: Beef Cattle, Nutrition, Reproduction, Fat J. Anim. Sci. 1995. 73:2888–2892 Introduction provision of linolenic acid (precursor to PGF2a) may improve follicular recruitment and conception rates Development of commercial products based on (Lucy et al., 1991b). Feeding CSFA increased plasmacalcium soaps of fatty acids ( CSFA) offers beef cattle LH in beef cows after calf removal (Hightshoe et al.,producers a method of increasing energy density in 1991). Addition of supplemental fat to dairy and beefrange supplements without harming forage utilization cattle diets probably stimulates lipoprotein cholesterol(Hightshoe et al., 1990). export by the intestine and increases circulating Feeding bypass fat (Megalac) to dairy cows plasma LDL and HDL cholesterol concentrationresulted in greater conception rates (Ferguson et al., (Talavera et al., 1985). Feeding diets high in lipid1988). The mechanism by which bypass fat influences content ( 8 % ) to cows and heifers resulted in increasedreproductive function is not well understood. Feeding concentration of HDL in serum and follicular fluidfat may positively influence reproductive performance (Wehrman and Williams, 1989).of cows by promoting an earlier return to positive The objectives of this study were to determine theenergy balance, earlier ovarian cycling postpartum, influence of Megalac, as a source of CSFA, onand higher conception rates at first service (Butler reproductive efficiency during the postpartum periodand Smith, 1989; Carroll et al., 1990). In addition, in suckled beef cows maintained under pasture conditions and to determine the influence of CSFA on calf growth. 1We gratefully acknowledge Dennis Hallford, Dept. of Anim. andRange Sci., New Mexico State Univ. for the progesterone assays andfor the preparation of this manuscript. Materials and Methods 2Present address: Universidad Autonoma de B.C.S. Apartado ´ ´Postal 19-B, La Paz, B.C.S., Mexico, C.P. 23000. 3To whom correspondence should be addressed. Multiparous Angus and Hereford × Angus cows ( n = Received October 4, 1994. 134) ranging from 5 to 7 yr of age were blocked by Accepted June 1, 1995. breed and age and assigned randomly to receive 1 kg/d 2888 Downloaded from jas.fass.org by guest on August 18, 2011
  3. 3. RESPONSE OF RANGE BEEF COWS AND CALVES TO BYPASS FAT 2889of a control diet ( C, n = 68) containing grain sorghum (Sera-Pak, Ames Division). The VLDL was calculated(80%), meat meal (18%), and urea ( 2 % ) (ME = 3.12 to be 1/5 of TG (Sera-Pak, Ames Division). Serum P4Mcal) or the same diet plus 125 g/d of Megalac ( M, n was determined by RIA using a commercial kit= 66; Church & Dwight Co., Princeton, NJ) as a (Diagnostic Products, Los Angeles, CA). Assays weresource of CSFA (ME = 3.8 Mcal). Diets were performed by the Animal Science Endocrinologyisonitrogenous (CP = 23%) and were fed during 105 d, Laboratory at New Mexico State University and thebeginning at 61 ± 3.9 d precalving. Birth weight of between- and within-assay coefficients of variationcalves was recorded. At three postpartum periods (35, were 5.2 and 8.1%, respectively.50, and 95 d), body condition scores ( BC1, BC2, and Data for calf weight, weight and body conditionBC3 [Whitman, 1975]) and body weights ( BW1, BW2, score in cows, and lipid metabolites were analyzed byand BW3) of cows were recorded. Weights of calves in analysis of variance in a completely randomizedthe same postpartum periods ( WC1, WC2, and WC3) design using the GLM procedure (SAS, 1988). Preg-and weaning weight ( WW) at 198 ± 6.0 d and 202 ± nancy rates at the first and second half and at end of5.1 d of age in C and M calves, respectively, were the breeding season were compared by chi-squarerecorded. All cows were exposed to mature Hereford (Steel and Torrie, 1980). The percentage of cyclingbulls (three bulls by group) that had passed breeding cows at 30 to 90 d and after 90 d postpartum weresoundness examinations (BIF, 1990) for a analyzed by the Catmod procedure (SAS, 1988).190-d breeding period on two pastures under a30-d rotational system. Two blood samples werecollected monthly from each cow (7-d intervals) on Results and Discussiondifferent postpartum periods, for determination oftotal cholesterol ( CHOL) , high-density lipoprotein Calf Weight. Calf weights from birth to weaning arecholesterol ( HDL) , low-density lipoprotein cholesterol shown in Table 1. The birth weight was similar ( P >( LDL) , very-low-density lipoprotein cholesterol .05) for calves from M (31.8 kg) and C (30.6 kg)( VLDL) , triglycerides ( TG) , and progesterone ( P4) . groups. Even though diets were not isoenergetic, theThe percentage of cycling cows at 30 to 90 d and > 90 d metabolizable energy provided by 125 g of M was notpostpartum was determined by the P4 concentration sufficient to stimulate greater fetal growth. Similar( P 4 > 1 ng/mL = cycling cow). Blood was collected into research for birth weight in Hereford calves wasevacuated tubes via jugular venipuncture, maintained reported by Stuedemann et al. (1968). However, WC1on ice, allowed to clot, and centrifuged within 12 h was greater ( P < .05) in calves from the M groupafter collection. Serum was harvested and stored at (46.8 kg) than in calves from the C group (43.8 kg)−20°C until P4 and lipids (CHOL, HDL, LDL, VLDL, and was affected by sex, age, and birth weight ( P <and TG) were determined. Lipid profiles were deter- .05). Male calves were heavier. A similar differencemined by a commercial laboratory using automated, was observed in WC2 ( P < .01), with values of 56.0enzymatic procedures. The CHOL was determined in and 50.6 kg for calves of M and C, respectively. Theserum after having been hydrolyzed and oxidizedenzymatically. In the oxidation process, H2O2 was WC3 and adjusted WW were greater ( P < .01) inproduced. Its presence of peroxidase, by reaction with calves of the M group, with a difference of 7 and 13 kg4-amino-antipirine and fenol, was transformed in a for each variable, respectively (Table 1). Sex and agecoloring of quinonimine (Merck-Me ´xico, S. A.). The of calf affected ( P < .01) WC3, WW, and gain fromHDL were separated from chylomicrons, VLDL, and birth to weaning (132.8 kg in M vs 120.8 kg in C,LDL by addition of a precipitating reagent (phos-photungstic acid-magnesium chloride) to serum. Aftercentrifugation, the cholesterol content of the HDL Table 1. Weights of calves (kg) produced by cowsfraction remained in the supernatant and was deter- receiving either a control diet or Megalacmined by the enzymatic colorimetric method usingcholesterol esterase, cholesterol oxidase, peroxidase, Dietand the chromogen 4-aminophenazone/phenol (Sera-Pak, Ames Division). The LDL was determined by Item Controla ± SEb Megalacc ± SEd Pdifference between CHOL and HDL. The enzymatic Birth wt 30.6 ± .77 31.8 ± .70 > .05colorimetric method for TG determination is based on Days of agethe principle that glycerol released from hydrolysis of 35 (WC 1 ) 43.8 ± 2.67 46.8 ± 2.53 < .05triglycerides by lipoprotein lipase is converted by 50 (WC 2 ) 50.6 ± 2.47 56.0 ± 2.12 < .01glycerolquinase into glycerol-3-phosphate, which is 95 (WC 3 ) 91.8 ± 4.01 98.8 ± 3.60 < .01oxidized by glycerolphosphate oxidase to dihydrox- Weaning wte 173.0 ± 2.98 186.0 ± 2.72 < .01yacetone phosphate and hydrogen peroxide. In the a1 kg/d during 105 d, 68 cows with calf. b,dBased on 68 and 66 calves, respectively.presence of peroxidase, hydrogen peroxide oxidizes cControl diet mixed with 125 g/d of Megalac during 105 d, 66the chromogen 4-aminophenasone/N-ethyl-N-(3-sul- cows with calf.phopropyl)-m-anisidine to a violet-colored compound eAdjusted to 200 d of age. Downloaded from jas.fass.org by guest on August 18, 2011
  4. 4. 2890 ESPINOZA ET AL.respectively). The WW adjusted to 200 d of age was Table 3. Reproductive performance of cows fed agreater in M calves (186 kg) than C calves (173.8 control diet or a diet supplemented with Megalackg). The increase in calf weights observed in the M Dietgroup can be explained possibly by a greater milk Item Controla Megalacb Pproduction of cows fed bypass fat (Coppock and Wilks,1991). However, in those studies dairy cows were used Percentage cyclingand were fed greater levels of bypass fat. Moreover, 30 to 90 dc 22.0 38.0 < .02 > 90 dd 72.0 61.0 > .05Knapp and Grummer (1991) observed that milk fat FHBSe 37.5 62.5 < .02percentage was greater for Holstein cows fed 5 than EBSf 84.7 90.9 > .05for those fed 0% fat (3.46 vs 3.15%, respectively). a1 kg/d during 105 d, 68 cows with calves. Weight and Body Condition Score in Cows. Body bControl diet mixed with 125 g of Megalac during 105 d, 66 cowsweight was greater ( P < .01) in M cows at 35 and 50 d with calves. cCycling cows at 30 to 90 d postcalving.postpartum (BW1 = 334 vs 310 kg; BW2 = 329 vs 299 dCycling cows after 90 d postcalving.kg). However, BW3 was similar ( P > .05) between ePregnant cows at first half of a 190-d breeding season.groups (376 vs 360 kg in M and C, respectively). This fPregnant cows at end of a 190-d breeding season.similarity at period 3 was expected because BW3 wasobtained 30 d after treatments ended, when cows wereon common pasture. Body condition scores (BC1, BC2, (1975) reported that beef calves with greaterand BC3) followed a trend similar to that of BW (4.1 preweaning growth had more serum cholesterol thanvs 3.4, P < .01; 3.6 vs 2.25, P < .01; and 6.2 vs 5.9, P > did calves that gained less rapidly. Furthermore,.05, for M and C, respectively). Body condition score cholesterol in calves declined after weaning. Serumchange between BC2 and BC3 was greater ( P < .01) concentration of lipid metabolites (CHOL, HDL, LDL,in C than in M. Body condition score, body weight at VLDL, and TG) were greater ( P < .01) in cows fedsecond period, and body condition score change CSFA (Table 2). A similar response was observed bybetween BC2 and BC3 were affected ( P < .01) by Peters and Corah (1993) in beef heifers fed .454 kg ofpostpartum days. The tendencies in body weight and Megalac. Sklan et al. (1989) reported that serumcondition scores at the start of the postpartum period levels of CHOL and HDL were greater between 15 andsupport observations that energy intake in this period 29 d postpartum in CSFA-supplemented cows. Greateris less than required (Haresign, 1988). Williams concentrations of CHOL, HDL, and TG were also(1989) found that body condition score remained observed by Morgan and Williams (1989) in cows fedconstant through the first 100 d postpartum, and all diets with elevated lipids. Williams (1989) observedcows exhibited a slight decrease (13.7 kg) in BW that that mean concentrations of total CHOL and TG indid not differ between groups (8% vs 2.8% dietary control animals (2.8% dietary lipid) were lower thanlipid). However, in our study, feeding 125 g/d of in animals fed a high-lipid ( 8 % ) diet during the 4th,Megalac maintained a greater body weight and body 5th, and 6th wk after calving. By the 4th wk, plasmacondition score during the first 50 d postpartum. concentrations of CHOL and TG in cows supplemented Lipid Metabolites. Plasma concentrations of with a high-fat diet were greater than control valuescholesterol increased with ingestion of milk lipids by by 1.7- and 1.4-fold, respectively. The greater concen-suckling calves (Carroll and Hamilton, 1973). O’Kelly tration of metabolites can be explained by increased intestinal secretion of lipoproteins with a high content of TG such as VLDL. Table 2. Serum lipids (mg/dL) in cows fed either a Reproductive Performance. The percentage of cycling control diet or a diet supplemented with Megalac cows 30 to 90 d after calving was greater ( P < .02) in M (38%) than in C (22%). However, after 90 d Diet postpartum, the percentage of cycling cows was similar ( P > .05) between treatments (61 vs 72% forMetabolitea Controlb ± SEc Megalacd ± SEe P M and C, respectively [Table 3]).CHOL 146.2 ± 7.62 186.6 ± 6.99 < .01 The percentage of pregnant cows at end of theHDL 67.8 ± 4.49 81.4 ± 4.12 < .02 breeding season was similar ( P > .05) betweenLDL 97.1 ± 9.4 130.1 ± 8.6 < .01 treatments (91 vs 84% in M and C, respectively);VLDL 18.7 ± 1.25 26.0 ± 1.15 < .01TG 94.0 ± 6.27 130.0 ± 5.75 < .01 however, 62.5% of cows in M were pregnant during the aCHOL = total cholesterol; HDL = high-density lipoprotein first half of the breeding season, compared with 35.5%cholesterol; LDL = low-density lipoprotein cholesterol; VLDL = very- ( P < .02) in the C group (Table 3). Similar resultslow-density lipoprotein cholesterol; TG = triglycerides. were reported by Ferguson et al. (1988), who b1 kg/d during 105 d, 68 cows with calf. c,eBased on 32 and 38 samples, respectively. observed greater conception rates and fewer open days dControl diet mixed with 125 g/d of Megalac during 105 d, 66 in dairy cows supplemented with bypass fat. Incows with calf. contrast, cows fed CSFA (Sklan et al., 1991) initiated Downloaded from jas.fass.org by guest on August 18, 2011
  5. 5. RESPONSE OF RANGE BEEF COWS AND CALVES TO BYPASS FAT 2891ovarian cyclicity later than controls; however, after calving in our study may be related to a greater CHOLcyclicity began, more fat-fed cows than controls had available for P4 synthesis in M cows. This speculationnormal cycle length (18 to 26 d). Conception rate was is based on a study in which 80% of lipid-fed femalesgreater in cows fed CSFA and number of open days exhibited at least slight increases in baseline P4 beforewas reduced. induced estrous cycle with GnRH treatment, compared Feeding diets that contain fats and that are higher with 37% of controls (Williams, 1989). These observa-in energy may partially alleviate negative energy tions suggest that fat supplement affects the “quality”balance and stimulate ovarian function (Lucy et al., of the corpus luteum rather than the number or1991b). Hypothetically, the additional dietary energy quantity of corpora lutea.(and not the CSFA) stimulated the development offollicles and led to larger ovarian follicles in fat-fedcows. To test this hypothesis, Lucy et al. (1991a) Implicationsconducted an experiment in which three diets wereformulated for postpartum lactating cows: a control The calcium soaps of fatty acids may be used indiet (no CSFA), a diet containing CSFA with energy relatively small amounts in beef cow diets on range todensity equivalent to that of the control diet, and a improve reproductive efficiency during the postpartumthird diet that contained both additional energy and period. In this study, feeding Megalac resulted in moreCSFA. In that experiment, after 4 wk of feeding the cows cycling at 30 to 90 d postpartum and more cowsexperimental diets, preovulatory follicles were larger pregnant during the first half of the breeding season.in diameter in cows fed the CSFA diets with either These effects would result in older calves during thenormal or high energy levels than in cows fed the next production cycle and a greater efficiency in thecontrol diet. herd. Moreover, calves produced by Megalac-sup- Although mechanisms have not yet been deter- plemented cows were heavier than those produced bymined, mean serum concentrations of LH measured controls, which could justify addition of Megalac toduring three periods surrounding calf removal were pre- and postpartum cattle diets.greater in cows receiving CSFA than in controls(Hightshoe et al., 1991). Similar responses wereobserved by Lucy et al. (1989), who found that basal Literature CitedLH was increased in early postpartum dairy cows BIF. 1990. Guidelines for Uniform Beef Improvement Programsreceiving CSFA. However, feeding fat (CSFA) did not (6th Ed.). Beef Improvement Federation, Oklahoma Stateinfluence the basal, smoothed mean concentration and Univ., Stillwater.average LH amplitude (Lucy et al., 1991b). Reports of Butler, W. R., and R. D. Smith. 1989. Interrelationship betweenpituitary response to GnRH stimulation in intact beef energy balance and postpartum reproductive function in dairycows consuming hyperlipidemic diets indicated that cattle. J. Dairy Sci. 72:767. Carroll, D. J., R. R. Grummer, and F. C. Mao. 1992. Progesteroneneither GnRH-induced LH release nor tonic release production by cultured luteal cells in the presence of bovine lowwas affected (Johnson et al., 1987; Morgan and and high density lipoproteins purified by heparin affinity chro-Williams, 1989). In contrast, De Luna et al. (1982) matography. J. Anim. Sci. 70:2516.fed protected lipids to ovariectomized cows in the early Carroll, D. J., M. J. Jerred, R. R. Grummer, D. K. Combs, R. A.postpartum period and observed greater concentra- Pierson, and E. R. Hauser. 1990. Effects of fat supplementation and immature alfalfa to concentrate ratio on plasma progester-tions of LH in response to exogenous GnRH. one, energy balance, and reproductive traits of dairy cattle. J. In addition to their more obvious effects on energy Dairy Sci. 73:2855.balance, CSFA may increase postpartum release of Carroll, K. K., and R.M.G. Hamilton. 1973. Plasma cholesterol levelsuterine prostaglandin F2a, which has been implicated in suckling and weaned calves, lambs, pigs and colts. Lipids 8:as an important modulator in the initiation of estrous 635. Coppock, C. E., and D. L. Wilks. 1991. Supplemental fat in high-cycles after calving (Madej et al., 1984). However, energy rations for lactating cows: Effects on intake, digestion,feeding fat (CSFA) did not influence 15-keto- milk yield, and composition. J. Anim. Sci. 69:3826.13,14-dihydro-prostaglandin F2a (Lucy et al., 1991b). De Luna, C. J., W. H. Brown, D. E. Ray, and T. N. Wagner. 1982. Although the mechanisms by which changes in lipid Effects to protected fat supplement on GnRH induced LHmetabolism may influence ovarian function have not release in ovariectomized and early postpartum beef cows. J.been determined, a wide array of potential pathways Anim. Sci. 55(Suppl. 1):348 (Abstr.). Ferguson, J. D., T. L. Blanchard, and W. Chalupa. 1988. Protein,exists (Williams, 1989). The P4 production by luteal fats and fertility in dairy cows. Bovine Proc. 20:112.cells was greater with highest HDL and LDL in vitro ´ Haresign, W. 1988. Condicion corporal, produccion de leche y(Carroll et al., 1992). Granulosa cells of heifers fed ´ reproduccion en el ganado vacuno. En: W. Haresign and D.J.A.high-fat diets ( 8 % ) during 30 d released 2.1- to ´ Cole (Ed.) Avances en Nutricion de los Rumiantes. p 1.3.5-fold more pregnenolone and P4 in vitro, and the Acribia, Spain. Hightshoe, R. B., R. C. Cochran, L. R. Corah, D. L. Harmon, and E.luteal activity was 18% greater (Wehrman et al., S. Vanzant. 1990. Influence of level and source of rumen-escape1991). Based on these studies, we speculate that the lipid in a supplement on forage intake and digestibility. J.greater percentage of cycling cows at 30 to 90 d after Anim. Sci. 68(Suppl. 1):571 (Abstr.). Downloaded from jas.fass.org by guest on August 18, 2011
  6. 6. 2892 ESPINOZA ET AL.Hightshoe, R. B., R. C. Cochran, L. R. Corah, G. H. Kiracofe, D. L. Peters, C. W., and L. R. Corah. 1993. Effect of rumen-escape lipid on Harmon, and R. C. Perry. 1991. Effects of calcium soaps of fatty endocrine profiles, lipid metabolites and follicular dynamics acids on postpartum reproductive function in beef cows. J. during estrus synchronization in primiparous beef heifers. J. Anim. Sci. 69:4097. Anim. Sci. 71(Suppl. 1):72 (Abstr.).Johnson, M. S., T. N. Wagner, and D. E. Ray. 1987. Effects of SAS. 1988. SAS/STAT® User’s Guide (Release 6.03). SAS Inst. Inc., elevated serum lipids on luteinizing hormone response to Cary, NC. gonadotrophin releasing hormone challenge in energy deficient Sklan, D., E. Bogin, Y. Avidar, and S. Gur-Arie. 1989. Feeding anestrous heifers. Theriogenology 27:421. calcium soaps of fatty acids to lactating cows: Effect on produc-Knapp, D. M., and R. R. Grummer. 1991. Response of lactating dairy tion, body condition and blood lipids. J. Dairy Res. 56:675. cows to fat supplementation during heat stress. J. Dairy Sci. Sklan, D., U. Moallem, and Y. Folman. 1991. Effect of feeding 74:2573. calcium soaps of fatty acids on production and reproductiveLucy, M. C., R. L. De La Sota, C. R. Staples, and W. W. Thatcher. responses in high producing lactating cows. J. Dairy Sci. 74: 1991a. Effect of dietary calcium salts of long chain fatty acids 510. (CaLCFA), energy intake, and lactation on ovarian follicular Steel, R.G.D., and J. H. Torrie. 1980. Principles and Procedures of dynamics in Holstein dairy cows. J. Anim. Sci. 69(Suppl. 1): Statistics: A Biometrical Approach (2nd Ed.). McGraw-Hill 451 (Abstr.). Publishing Co., New York.Lucy, M. C., C. R. Staples, F. M. Michel, W. W. Thatcher, and D. J. Stuedemann, J. A., J. J. Guenther, S. A. Ewing, R. D. Morrison, and Bolt. 1991b. Effect of feeding calcium soaps to early postpartum G. V. Odell. 1968. Effect of nutritional level imposed from birth dairy cows on plasma prostaglandin F2 alpha, luteinizing hor- to eight months of age on subsequent growth and development mone and follicular growth. J. Dairy Sci. 74:483. patterns of full-fed beef calves. J. Anim. Sci. 27:234.Lucy, M. C., W. W. Thatcher, F. J. Michel, and C. R. Staples. 1989. Talavera, F. C., C. S. Park, and G. L. Williams. 1985. Relationships among dietary lipid intake, serum cholesterol and ovarian func- Effect of dietary calcium soaps of long chain fatty acids tion in Holstein heifers. J. Anim. Sci. 60:1045. (Megalac) on plasma prostaglandin F metabolite (PGFM), Wehrman, M. E., T. H. Welsh, and G. L. Williams. 1991. Diet- LH, energy balance, and follicular populations in early postpar- induced hyperlipidemia in cattle modifies the intrafollicular tum dairy cattle. J. Anim. Sci. 67(Suppl. 1):389 (Abstr.). cholesterol environment, modulates ovarian follicular dynamicsMadej, A., H. Kindahl, W. Woyno, L. E. Edquist, and R. Stupnicki. and hastens the onset of postpartum luteal activity. Biol. 1984. Blood levels of 15-keto-13,14-dihydro-prostaglandin F2 Reprod. 45:515. alpha during the postpartum period in primiparous cows. Wehrman, M. E., and G. L. Williams. 1989. Effect of dietary lipid Theriogenology 21:279. intake on serum and ovarian follicular lipid metabolites and onMorgan, A. R., and G. L. Williams. 1989. Effects of body condition follicular populations in beef females. Proc. So. Sect. Am. Soc. and postpartum dietary lipid intake on lipid metabolism and Anim. Sci. p 59 (Abstr.). pituitary function of beef cows. J. Anim. Sci. 67(Suppl. 1):385 Whitman, R. W. 1975. Weight change, body condition and beef cow (Abstr.). reproduction. Ph.D. Dissertation. Colorado State Univ., FortO’Kelly, J. C. 1975. Growth and lipid metabolism in genetically Collins. different types of calves in a tropical environment. Growth 39: Williams, G. L. 1989. Modulation of luteal activity in postpartum 125. beef cows through changes in dietary lipid. J. Anim. Sci. 67:785. Downloaded from jas.fass.org by guest on August 18, 2011
  7. 7. Citations This article has been cited by 3 HighWire-hosted articles: http://jas.fass.org/content/73/10/2888#otherarticles Downloaded from jas.fass.org by guest on August 18, 2011