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Why is it getting more difficult to successfully artificially inseminate dairy cows?*

Published online by Cambridge University Press:  01 August 2008

H. Dobson ,
S. L. Walker ,
M. J. Morris ,
J. E. Routly  and
R. F. Smith
H. Dobson*
Affiliation:
Department of Veterinary Clinical Science, University of Liverpool, Leahurst, Neston, Wirral CH64 7TE, UK
S. L. Walker
Affiliation:
Department of Veterinary Clinical Science, University of Liverpool, Leahurst, Neston, Wirral CH64 7TE, UK
M. J. Morris
Affiliation:
Department of Veterinary Clinical Science, University of Liverpool, Leahurst, Neston, Wirral CH64 7TE, UK
J. E. Routly
Affiliation:
Department of Veterinary Clinical Science, University of Liverpool, Leahurst, Neston, Wirral CH64 7TE, UK
R. F. Smith
Affiliation:
Department of Veterinary Clinical Science, University of Liverpool, Leahurst, Neston, Wirral CH64 7TE, UK
*
E-mail: hdobson@liv.ac.uk
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Abstract

Successfully using artificial insemination (AI) is defined as getting cows pregnant when the farmer wants them in-calf and making the best use of appropriate genetic potential. Over the past 30 to 50 years, the percentage of animals in oestrus that stand-to-be-mounted (STBM) has declined from 80% to 50%, and the duration of STBM from 15 h to 5 h; both in parallel with a reduction in first-service-pregnancy-rate from 70% to 40%. Meanwhile, the incidence of lameness and mastitis has not decreased; and it takes more than an extra 40 and 18 days, respectively, to get a lame or mastitic cow in-calf compared to healthy herd-mates. The intensity of oestrus is 50% lower in severely lame cows, and fewer lame cows ovulate. Luteal phase milk progesterone concentrations are also 50% lower in lame cows, and follicular phase oestradiol is also lower in non-ovulating lame cows compared to ovulating animals. Furthermore, lame cows that do not ovulate do not have an LH surge, and the LH pulse frequency in their late follicular phase is lower (0.53 v. 0.76 pulses/h). Thus, we suggest that the stress of lameness reduces LH pulsatility required to drive oestradiol production by the dominant follicle. The consequent low oestradiol results in less-intense oestrus behaviour and failure to initiate an LH surge; hence there is no ovulation. A series of experimental studies substantiate our hypothesis that events activating the hypothalamus–pituitary–adrenal axis interfere at both the hypothalamus and the pituitary level to disrupt LH and oestradiol secretion, and thus the expression of oestrus behaviour. Our inability to keep stress at a minimum by appropriately feeding and housing high-production cows is leading to a failure to meet genetic potential for yield and fertility. We must provide realistic solutions soon, if we want to successfully use AI to maintain a sustainable dairy industry for the future.

Keywords

oestrusoestradiolprogesteroneLHstresslamenessmastitis
Type
Full Paper
Information
animal , Volume 2 , Issue 8 , August 2008 , pp. 1104 - 1111
Copyright
Copyright © The Animal Consortium 2008

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Footnotes

*

This invited paper was presented at BSAS meeting ‘Fertility in Dairy Cows – bridging the gaps’ 30–31 August 2007, Liverpool Hope University.

References

At-Taras, EE, Spahr, SL 2001. Detection and characterization of estrus in dairy cattle with an electronic heatmount detector and an electronic activity tag. Journal of Dairy Science 84, 792–798.CrossRefGoogle Scholar
Bartlett, PC, Miller, GY, Lance, SE, Heider, LE 1992. Clinical mastitis and intramammary infections on Ohio dairy farms. Preventive Veterinary Medicine 12, 59–71.CrossRefGoogle Scholar
Beckett, S, Lean, I, Dyson, R, Tranter, W, Wade, L 1998. Effects of monensin on the reproduction, health, and milk production of dairy cows. Journal of Dairy Science 81, 1563–1573.CrossRefGoogle ScholarPubMed
Bigras-Poulin, M, Meek, AH, Martin, SW, McMillan, I 1990. Health-problems in selected Ontario Holstein cows – frequency of occurrences, time to first diagnosis and associations. Preventive Veterinary Medicine 10, 79–89.CrossRefGoogle Scholar
Borsberry, S, Dobson, H 1989. Periparturient diseases and their effect on reproductive performance in five dairy herds. Veterinary Record 124, 217–219.CrossRefGoogle ScholarPubMed
Britt, JH, Scott, RG, Armstrong, JD, Whitacre, MD 1986. Determinants of estrous behavior in lactating Holstein cows. Journal of Dairy Science 69, 2195–2205.CrossRefGoogle ScholarPubMed
Bulman, DC, Wood, PDP 1980. Abnormal patterns of ovarian activity in dairy cows and their relationships with reproductive performance. Animal Production 30, 177–188.Google Scholar
Butler, WR 2003. Energy balance relationships with follicular development, ovulation and fertility in post partum dairy cows. Livestock Production Science 83, 211–218.CrossRefGoogle Scholar
Cavalieri, J, Flinker, LR, Anderson, GA, Macmillan, KL 2003. Characteristics of oestrus measured using visual observation and radiotelemetry. Animal Reproduction Science 76, 1–12.Google Scholar
Chamberlain, AT, Wassell, TR 1995. The size and cost of the estimation error when using analysis of a sample of a dairy herd to assess whole herd performance. Preventive Veterinary Medicine 23, 65–71.CrossRefGoogle Scholar
Clarkson, MJ, Downham, DY, Faull, WB, Hughes, JW, Manson, FJ, Merritt, JB, Murray, RD, Russell, WB, Sutherst, JE, Ward, WR 1996. Incidence and prevalence of lameness in dairy cattle. Veterinary Record 138, 563–567.CrossRefGoogle ScholarPubMed
Coe, BL, Allrich, RD 1989. Relationship between endogenous estradiol-17 beta and estrous behavior in heifers. Journal of Animal Science 67, 1546–1551.CrossRefGoogle ScholarPubMed
Collick, DW, Ward, WR, Dobson, H 1989. Associations between types of lameness and fertility. Veterinary Record 125, 103–106.CrossRefGoogle ScholarPubMed
Dekkers, JCM, Ten Hag, JH, Weersink, A 1998. Economic aspects of persistency of lactation in dairy cattle. Livestock Production Science 53, 237–252.CrossRefGoogle Scholar
Dobson, H 1987. Effect of transport stress on luteinizing hormone released by GnRH. Acta Endocrinologica 115, 63–66.Google ScholarPubMed
Dobson, H, Alam, MGS, Kanchev, LN 1987. Effect of betamethasone treatment on luteal life-span and the response to GnRH in dairy cows. Journal of Reproduction and Fertility 80, 25–30.Google Scholar
Dobson, H, Ribadu, AY, Noble, KM, Tebble, JE, Ward, WR 2000. Ultrasound and hormone profiles of ACTH-induced persistent ovarian follicles (cysts) in cattle. Journal of Reproduction and Fertility 120, 405–410.CrossRefGoogle ScholarPubMed
Dransfield, MB, Nebel, RL, Pearson, RE, Warnick, LD 1998. Timing of insemination for dairy cows identified in estrus by a radiotelemetric estrus detection system. Journal of Dairy Science 81, 1874–1882.CrossRefGoogle ScholarPubMed
Duffield, TF, Leslie, KE, Sandals, D, Lissemore, K, McBride, BW, Lumsden, JH, Dick, P, Bagg, R 1999. Effect of a monensin-controlled release capsule on cow health and reproductive performance. Journal of Dairy Science 82, 2377–2378.Google Scholar
Enting, H, Kooij, D, Dijkhuizen, AA, Huirne, RBM, Noordhuizen, GS, Stassen, EN 1997. Economic losses due to clinical lameness in dairy cattle. Livestock Production Science 49, 259–267.CrossRefGoogle Scholar
Esslemont, RJ, Bryant, MJ 1976. Oestrous behaviour in a herd of dairy cows. Veterinary Record 99, 472–475.CrossRefGoogle Scholar
Esslemont, RJ, Kossaibati, MA 1996. Incidence of production diseases and other health problems in a group of dairy herds in England. Veterinary Record 139, 486–490.Google Scholar
Etherington, WG, Christie, KA, Walton, JS, Leslie, KE, Wickstrom, S, Johnson, WH 1991. Progesterone profiles in postpartum Holstein dairy-cows as an aid in the study of retained fetal membranes, pyometra and anestrus. Theriogenology 35, 731–746.CrossRefGoogle Scholar
Etherington, WG, Kinsel, ML, Marsh, WE 1996. Relationship of production to reproductive performance in Ontario dairy cows: herd level and individual animal descriptive statistics. Theriogenology 46, 935–959.Google Scholar
Fabre-Nys, C, Martin, GB 1991. Hormonal control of proceptive and receptive sexual behavior and the preovulatory LH surge in the ewe: reassessment of the respective roles of estradiol, testosterone and progesterone. Hormones and Behavior 25, 295–312.CrossRefGoogle Scholar
Fonseca, FA, Britt, JH, McDaniel, BT, Wilk, JC, Rakes, AH 1983. Reproductive traits of Holsteins and Jerseys – effects of age, milk-yield, and clinical abnormalities on involution of cervix and uterus, ovulation, estrous cycles, detection of estrus, conception rate, and days open. Journal of Dairy Science 66, 1128–1147.CrossRefGoogle ScholarPubMed
Frei, C, Frei, PP, Stark, KDC, Pfeiffer, DU, Kihm, U 1997. The production system and disease incidence in a national random longitudinal study of Swiss dairy herds. Preventive Veterinary Medicine 32, 1–21.Google Scholar
Fulkerson, WJ, Wilkins, J, Dobos, RC, Hough, GM, Goddard, ME, Davison, T 2001. Reproductive performance in Holstein-Friesian cows in relation to genetic merit and level of feeding when grazing pasture. Animal Science 73, 397–406.CrossRefGoogle Scholar
Galindo, F, Broom, DM, Jackson, PGG 2000. A note on possible link between behaviour and the occurrence of lameness in dairy cows. Applied Animal Behaviour Science 67, 335–341.CrossRefGoogle ScholarPubMed
Garforth, C, McKemy, K, Rehman, T, Tranter, R, Cooke, R, Park, J, Dorward, P, Yates, C 2006. Farmers’ attitudes towards techniques for improving oestrus detection in dairy herds in South West England. Livestock Science 103, 158–168.CrossRefGoogle Scholar
Garnsworthy, PC 2006. Body condition score in dairy cows: targets for production and fertility. In Recent advances in animal nutrition – 2006 (ed. PC Garnsworthy and J Wiseman), pp. 150–200. Nottingham University Press, Nottingham, UK.Google Scholar
Glencross, RG, Esslemont, RJ, Bryant, MJ, Pope, G 1981. Relationships between the incidence of pre-ovulatory behavior and the concentrations of oestradiol-17-beta and progesterone in bovine plasma. Applied Animal Ethology 7, 141–148.CrossRefGoogle Scholar
Green, MJ, Leach, KA, Breen, JE, Green, LE, Bradley, AJ 2007. National intervention study of mastitis control in dairy herds in England and Wales. Veterinary Record 160, 287–290.Google Scholar
Grohn, YT, Erb, HN, McCulloch, CE, Salomiemi, HS 1990. Epidemiology of reproductive disorders in dairy cattle: associations among host characteristics, disease, and production. Preventive Veterinary Medicine 8, 25–39.CrossRefGoogle Scholar
Hackett, AJ, McAllister, AJ 1984. Onset of estrus in dairy-cows maintained indoors year-round. Journal of Dairy Science 67, 1793–1797.CrossRefGoogle ScholarPubMed
Haile-Mariam, M, Bowman, PJ, Goddard, ME 2003. Genetic and environmental relationship among calving interval, survival, persistency of milk yield and somatic cell count in dairy cattle. Livestock Production Science 80, 189–200.CrossRefGoogle Scholar
Hall, JG, Branton, C, Stone, EJ 1959. Estrus, estrous cycles, ovulation time, time of service and fertility of dairy cattle in Louisiana. Journal of Dairy Science 42, 1086–1094.CrossRefGoogle Scholar
Harrison, RO, Ford, SP, Young, JW, Conely, AJ, Freeman, AE 1990. Increased milk production versus reproductive and energy status in high-producing dairy cows. Journal of Dairy Science 73, 2749–2758.CrossRefGoogle ScholarPubMed
Haskell, MJ, Rennie, LJ, Bowell, VA, Bell, MJ, Lawrence, AB 2006. Housing system, milk production, and zero-grazing effects on lameness and leg injury in dairy cows. Journal of Dairy Science 89, 4259–4266.CrossRefGoogle ScholarPubMed
Hemsworth, PH, Barnett, JL, Beveridge, L, Matthews, LR 1995. The welfare of extensively managed dairy-cattle – a review. Applied Animal Behaviour Science 42, 161–182.CrossRefGoogle Scholar
Hernandez, JA, Garbarino, EJ, Shearer, JK, Risco, CA, Thatcher, WW 2005. Comparison of the calving-to-conception interval in dairy cows with different degrees of lameness during the prebreeding postpartum period. Journal of the American Veterinary Medical Association 227, 1284–1291.Google Scholar
Heuer, C, Schukken, YH, Jonker, LJ, Wilkinson, JID, Noordhuizen, JPTM 2001. Effect of monensin on blood ketone bodies, incidence and recurrence of disease and fertility in dairy cows. Journal of Dairy Science 84, 1085–1097.CrossRefGoogle ScholarPubMed
Horan, B, Mee, JF, O’Connor, P, Rath, A, Dillon, P 2005. The effect of strain of Holstein-Friesian cow and feeding system on postpartum ovarian function, animal production and conception rate to first service. Theriogenology 63, 950–971.CrossRefGoogle ScholarPubMed
Hultgren, J 2002. Foot/leg and udder health in relation to housing changes in Swedish dairy herds. Preventive Veterinary Medicine 53, 167–189.CrossRefGoogle ScholarPubMed
Hurnik, JF, King, GJ, Robertson, HA 1975. Estrus and related behavior in postpartum Holstein cows. Applied Animal Ethology 2, 55–63.CrossRefGoogle Scholar
Huszenicza, G, Janosi, S, Kulcsar, M, Korodi, P, Reiczigel, J, Katai, L, Peters, AR, de Rensis, F 2005. Effects of clinical mastitis on ovarian function in post-partum dairy cows. Reproduction in Domestic Animals 40, 199–204.CrossRefGoogle ScholarPubMed
Judge, LJ, Erskine, RJ, Bartlett, PC 1997. Recombinant bovine somatotropin and clinical mastitis: Incidence, discarded milk following therapy, and culling. Journal of Dairy Science 80, 3212–3218.Google Scholar
Kanchev, LN, Dobson, H, Ward, WR, Fitzpatrick, RJ 1976. Concentration of steroids in bovine peripheral plasma during the oestrous cycle and the effect of betamethasone treatment. Journal of Reproduction and Fertility 48, 341–345.CrossRefGoogle ScholarPubMed
Kaneene, JB, Hurd, HS 1990. The National Animal Health Monitoring System in Michigan. I. Design, data and frequencies of selected dairy cattle diseases. Preventive Veterinary Medicine 8, 103–114.CrossRefGoogle Scholar
Kingwill, RG, Neave, FK, Dodd, FH 1970. Effect of a mastitis control system on levels of subclinical and clinical mastitis in 2 years. Veterinary Record 87, 94–99.Google Scholar
Lam, TJGM, Schukken, YH, Grommers, FJ, Smit, JAH, Brand, A 1993. Within-herd and between-herd variation in diagnosis of clinical mastitis in cattle. Journal of the American Veterinary Medical Association 202, 938–942.CrossRefGoogle ScholarPubMed
LeBlanc, SJ, Leslie, KE, Ceelen, HJ, Kelton, DF, Keefe, GP 1998. Measures of estrus detection and pregnancy in dairy cows after administration of gonadotropin-releasing hormone within an estrus synchronization program based on prostaglandin F-2 alpha. Journal of Dairy Science 81, 375–381.CrossRefGoogle Scholar
Leonard, N, Egan, J, Griffin, J, Hanlon, A, Poole, D 2001. A survey of some factors relevant to animal welfare on 249 dairy farms in the Republic of Ireland. Part 2: data on incidence of disease, culling and biosecurity measures. Irish Veterinary Journal 54, 454–456.Google Scholar
Loeffler, SH, de Vries, MJ, Schukken, YH 1999. The effects of time of disease occurrence, milk yield, and body condition on fertility of dairy cows. Journal of Dairy Science 82, 2589–2604.CrossRefGoogle ScholarPubMed
Lopez, H, Bunch, TD, Shipka, MP 2002. Estrogen concentrations in milk at estrus and ovulation in dairy cows. Animal Reproduction Science 72, 37–46.CrossRefGoogle ScholarPubMed
Lopez-Gatius, F, Yanis, J, Madriles-Helm, D 2003. Effects of body condition score and score change on the reproductive performance of dairy cows: a meta-analysis. Theriogenology 59, 801–812.CrossRefGoogle ScholarPubMed
Lyimo, ZC, Nielen, M, Ouweltjes, W 2000. Relationship among estradiol, cortisol and intensity of estrous behavior in dairy cattle. Theriogenology 53, 1783–1795.CrossRefGoogle ScholarPubMed
McCoy, MA, Lennox, SD, Mayne, CS, McCaughey, WJ, Edgar, HWJ, Catney, DC, Verner, M, Mackey, DR, Gordon, AW 2006. Milk progesterone profiles and their relationship with fertility, production and disease in dairy cows in Northern Ireland. Animal Science 82, 213–222.CrossRefGoogle Scholar
Melendez, P, Bartolome, J, Archbald, LF, Donovan, A 2003. The association between lameness, ovarian cysts and fertility in lactating dairy cows. Theriogenology 59, 927–937.CrossRefGoogle ScholarPubMed
Miglior, F, Muir, BL, van Doormaal, BJ 2005. Selection indices in Holstein cattle of various countries. Journal of Dairy Science 88, 1255–1263.CrossRefGoogle ScholarPubMed
Muir, BL, Fateh, J, Schaeffer, LR 2004. Genetic relationships between persistency and reproductive performance in first-lactation Canadian Holsteins. Journal of Dairy Science 87, 3029–3037.CrossRefGoogle ScholarPubMed
Nanda, AS, Dobson, H, Ward, WR 1990. Relationship between an increase in plasma cortisol during transport stress and the failure of oestradiol to induce an LH surge in dairy cows. Research in Veterinary Science 49, 25–28.CrossRefGoogle Scholar
Oltenacu, PA, Ekesbo, I 1994. Epidemiologic study of clinical mastitis in dairy-cattle. Veterinary Research 25, 208–212.Google Scholar
Opsomer, G, Coryn, M, Deluyker, H, de Kruif, A 1998. An analysis of ovarian dysfunction in high yielding dairy cows after calving based on progesterone profiles. Reproduction in Domestic Animals 33, 193–204.Google Scholar
Parker AJC 1992. Body condition score, milk fever and fertility in dairy cows. DBR dissertation, University of Liverpool, UK.Google Scholar
Patton, J, Kenny, DA, McNamara, S, Mee, JF, O’Mara, FP, Diskin, MG, Murphy, JJ 2007. Relationships among milk production, energy balance, plasma analytes, and reproduction in Holstein-Friesian cows. Journal of Dairy Science 90, 649–658.CrossRefGoogle ScholarPubMed
Pennington, JA, Albright, JL, Callahan, CJ 1986. Relationships of sexual activities in estrous cows to different frequencies of observation and pedometer measurements. Journal of Dairy Science 69, 2925–2934.CrossRefGoogle ScholarPubMed
Petersson, KJ, Gustafsson, H, Strandberg, E, Berglund, B 2006a. A typical progesterone profiles and fertility in Swedish dairy cows. Journal of Dairy Science 89, 2529–2538.CrossRefGoogle Scholar
Petersson, KJ, Strandberg, E, Gustafsson, H, Berglund, B 2006b. Environmental effects on progesterone profile measures of dairy cow fertility. Animal Reproduction Science 91, 201–214.CrossRefGoogle ScholarPubMed
Pursley, JR, Mee, MO, Wiltbank, MC 1995. Synchronization of ovulation in dairy-cows using PGF(2-alpha), and GnRH. Theriogenology 44, 915–923.CrossRefGoogle Scholar
Regula, G, Danuser, J, Spycher, B, Wechsler, B 2004. Health and welfare of dairy cows in different husbandry systems in Switzerland. Preventive Veterinary Medicine 66, 247–264.CrossRefGoogle ScholarPubMed
Roelofs, JB, Bouwman, EG, Dieleman, SJ, Van Eerdenburg, FJ, Kaal-Lansbergen, LM, Soede, NM, Kemp, B 2004. Influence of repeated rectal ultrasound examinations on hormone profiles and behaviour around oestrus and ovulation in dairy cattle. Theriogenology 62, 1337–1352.Google Scholar
Roelofs, JB, van Eerdenburg, FJCM, Soede, NM, Kemp, B 2005a. Pedometer readings for estrus detection and as predictor for time of ovulation in dairy cattle. Theriogenology 64, 1690–1703.Google Scholar
Roelofs, JB, van Eerdenburg, FJCM, Soede, NM, Kemp, B 2005b. Various behavioral signs of estrus and their relationship with time of ovulation in dairy cattle. Theriogenology 63, 1366–1377.Google Scholar
Royal, MD, Darwash, AO, Flint, APF, Webb, R, Wooliams, JA, Lamming, GE 2000. Declining fertility in dairy cattle: changes in traditional and endocrine parameters of fertility. Animal Science 70, 487–501.CrossRefGoogle Scholar
Schrick, FN, Hockett, ME, Saxton, AM, Lewis, MJ, Dowlen, HH, Oliver, SP 2001. Influence of subclinical mastitis during early lactation on reproductive parameters. Journal of Dairy Science 84, 1407–1412.CrossRefGoogle ScholarPubMed
Shpigel, NY, Winkler, M, Ziv, G, Saran, A 1998. Clinical, bacteriological and epidemiological aspects of clinical mastitis in Israeli dairy herds. Preventive Veterinary Medicine 35, 1–9.CrossRefGoogle ScholarPubMed
Shrestha, HK, Nakao, T, Suzuki, T, Akita, M, Higaki, T 2005. Relationships between body condition score, body weight, and some nutritional parameters in plasma and resumption of ovarian cyclicity postpartum during pre-service period in high-producing dairy cows in a subtropical region in Japan. Theriogenology 64, 855–866.CrossRefGoogle Scholar
Sprecher, DJ, Hostetler, DE, Kaneene, JB 1997. A lameness scoring system that uses posture and gait to predict dairy cattle reproductive performance. Theriogenology 47, 1179–1187.CrossRefGoogle ScholarPubMed
Stevenson, MA 2000. Disease incidence in dairy herds in the Southern highlands district of New South Wales, Australia. Preventive Veterinary Medicine 43, 1–11.Google Scholar
Stevenson, JS, Schmidt, MK, Call, EP 1983. Factors affecting reproductive performance of dairy cows first inseminated after 5 weeks postpartum. Journal of Dairy Science 66, 1148–1154.CrossRefGoogle ScholarPubMed
Stevenson, JS, Smith, MW, Jaeger, JR 1996. Detection of estrus by visual observation and radiotelemetry in peripubertal, estrus-synchronized beef heifers. Journal of Animal Science 74, 729–735.CrossRefGoogle ScholarPubMed
Tranter, WP, Morris, RS 1991. A case study of lameness in three dairy herds. New Zealand Veterinary Journal 39, 88–91.CrossRefGoogle ScholarPubMed
Van Eerdenburg, FJCM, Karthaus, D, Taverne, MAM, Merics, I, Scenzi, O 2002. The relationship between estrous behavioral score and time of ovulation in dairy cattle. Journal of Dairy Science 85, 1150–1156.CrossRefGoogle ScholarPubMed
Van Vliet, JH, Van Eerdenburg, FJCM 1996. Sexual activities and oestrus detection in lactating Holstein cows. Applied Animal Behaviour Science 50, 57–69.CrossRefGoogle Scholar
Veerkamp, RF, Oldenbroek, JK, Van Der Gaast, HJ, Van Der Werf, JHJ 2000. Genetic correlation between days until start of luteal activity and milk yield, energy balance, and live weights. Journal of Dairy Science 83, 577–583.CrossRefGoogle ScholarPubMed
Walker, WL, Nebel, RL, McGilliard, ML 1996. Time of ovulation relative to mounting activity in dairy cattle. Journal of Dairy Science 79, 1555–1561.CrossRefGoogle ScholarPubMed
Walker, SL, Smith, RF, Jones, DN, Routly, JE, Dobson, H 2008. Chronic stress, hormone profiles and estrus intensity in dairy cattle. Hormones and Behavior 53, 493–501.CrossRefGoogle ScholarPubMed
Whitaker, DA, Macrae, AI, Burrough, E 2004. Disposal and disease rates in British dairy herds between April 1998 and March 2002. Veterinary Record 155, 43–50.Google Scholar
Williamson, NB, Morris, RS, Blood, DC, Cannon, CM, Wright, PJ 1972. Study of estrous behavior and estrus detection methods in a large commercial dairy-herd. 2. Estrous signs and behavior patterns. Veterinary Record 91, 58–62.Google Scholar
Wishart, DF 1972. Observations on the oestrous cycle of the Friesian heifer. Veterinary Record 90, 595–597.Google Scholar
Xu, ZZ, McKnight, DJ, Vishwanath, R 1998. Estrus detection using radiotelemetry or visual observation and tail painting for dairy cows on pasture. Journal of Dairy Science 81, 2890–2896.Google Scholar
Zwald, NR, Weigal, KA, Chang, YM, Welper, RD, Clay, JS 2004. Genetic selection for health traits using producer-recorded data. I. Incidence rates, heritability estimates and sire breeding values. Journal of Dairy Science 87, 4287–4294.Google Scholar