Melissa Royal

DECLINING FERTILITY IN DAIRY CATTLE: CHANGES IN TRADITIONAL AND ENDOCRINE PARAMETERS OF FERTILITY

Reproductive performance of 714 Holstein Friesian dairy cows was monitored between October 1995 and June 1998 using thrice weekly milk progesterone determinations. Defined endocrine parameters such as interval to post-partum commencement of luteal activity, inter-ovulatory interval and length of luteal and inter-luteal intervals were used with a number of traditional measures of reproductive performance to investigate the current status of fertility in a sample of United Kingdom dairy herds. A comparison of the results of the 1995 to 1998 trial with those of a previous (1975 to 1982) milk progesterone database, which included 2503 lactations in British Friesian cows monitored using a similar milk sampling protocol, revealed a decline infertility between these periods. Between 1975-1982 and 1995-1998, pregnancy rate to first service declined from 55·6% to 39·7% ( P P P post partum (delayed luteolysis type I; 7·3% to 18·2%) and during subsequent cycles (delayed luteolysis type II; 6·4% to 16·8%), although the incidence of prolonged anovulation post partům (delayed ovulation type I; 10·9% to 12·9%) and prolonged inter-luteal intervals (delayed ovulation type II; 12·9% to 10·6%) did not alter significantly. These changes resulted in an increase in mean luteal phase length from 12·9 (s.e. 0·09) to 14·8 (s.e. 0·17) days and an increase in inter-ovulatory interval from 20·2 (s.e. 0·1) to 22·3 (s.e. 0·2) days. The decline infertility was also reflected in traditional measures of fertility since although interval to first service remained relatively unchanged (74·0 (s.e. 0·4) to 77·6 (s.e. 1·1) days) calving interval lengthened from 370 (s.e. 2·2) to 390 (s.e. 2·5) days. Collectively these changes may have contributed to the decline in pregnancy rates observed over the last 20 years.

Fertility in the high-producing dairy cow

Abstract Genetic correlations between milk yield and reproductive measures in dairy cows are unfavourable. This suggests that successful selection for higher yields may have led to a decline in fertility. There is also evidence that an imbalance of nutrients, in either high genetic merit cows or those fed diets not matched to their performance, leads to poorer reproductive performance. Physiological reasons for the antagonism have not been elucidated. In this paper we examine the complexity of genetic, nutritional, physiological and management factors of the yield versus fertility antagonism. To maintain or recover high fertility in modern dairy cows calls for a two-pronged approach involving both inclusion of fertility in broader breeding goals and adjustment to management practices.

Sequence variants in the bovine gonadotrophin releasing hormone receptor gene and their associations with fertility.

Seven sequence variants (SVs) have been identified in exon 1 and in the promoter region upstream of the bovine gonadotrophin releasing hormone (GnRH) receptor gene, at nucleotides g.-331A>G, g.-108T>C, g.+206G>A, g.+260C>T, g.+341C>T, g.+383C>T and g.+410C>T relative to the translation start site. The SVs at nucleotides g.-108, g.260, g.341 and g.410 and those at g.206 and g.383 formed two groups with complete linkage disequilibrium within groups, but incomplete linkage disequilibrium between groups, and none of the SVs altered receptor amino acid sequence. The g.-108T>C allelic variants were associated with an approximately 0.4 day reduction in predicted transmitting ability for days to first service. None of the allelic variants affected the pattern of circulating LH following administration of GnRH. The g.260C>T alteration introduced a new transcription factor binding site in a region of DNA with relatively low nucleosome formation potential. The data suggest that selection for animals carrying the g.-108T>C group of alterations will improve fertility in the dairy cow.

Short communication: heritability of milk fatty acid composition and stearoyl-CoA desaturase indices in dairy cows.

Activity of stearoyl-CoA desaturase (SCD) in the mammary gland is important for determining the relative proportions of saturated and monounsaturated fatty acids in milk and the concentration of the conjugated linoleic acid isomer rumenic acid (RA; cis-9,trans-11 18:2). Previous studies identified a large degree of between-cow variation in SCD activity, which was consistent across diets and suggests a genetic influence. The objectives of this study were to quantify genetic and phenotypic variations in fatty acid concentrations and SCD indices in milk fat and to estimate their heritabilities in a population of United Kingdom dairy cows. Milk samples were collected from 2,408 daughters of 597 Holstein-Friesian sires on 325 commercial farms for determination of fatty acid profiles. Indices of SCD activity were calculated by expressing each SCD product (cis-9 14:1, cis-9 16:1, cis-9 18:1, and RA) as a proportion of the precursor plus product [e.g., SCDI(14)=cis-9 14:1/(14:0+cis-9 14:1)]. For individual fatty acids, phenotypic variance was considerably greater than additive genetic variance, resulting in small and nonsignificant heritability estimates (+/- standard error) for all except 6:0 (h(2)=0.27+/-0.10), 8:0 (h(2)=0.27+/-0.09), 12:0 (h(2)=0.13+/-0.07), cis-9 14:1 (h(2)=0.28+/-0.10), and cis-9 18:1 (h(2)=0.12+/-0.07). Heritability estimates of desaturase indices were significant for SCDI(14) (h(2)=0.38+/-0.11), SCDI(18) (h(2)=0.19+/-0.09), and SCDI(RA) (h(2)=0.21+/-0.09), but not for SCDI(16) (h(2)=0.05+/-0.06). This study provides evidence that additive effects are responsible for a significant proportion of the phenotypic variation in SCD activity in dairy cows. It is concluded that because heritability of desaturase indices is moderate and significant in many cases, these indices could be investigated further for use in future breeding programs to increase concentrations of monounsaturated fatty acids and RA while decreasing concentrations of saturated fatty acids in milk fat.

Cellular localization of aquaporins along the secretory pathway of the lactating bovine mammary gland: an immunohistochemical study.

In this study we examined the cellular localization of aquaporins (AQPs) along the secretory pathway of actively lactating bovine mammary glands using immunohistochemistry. Mammary tissues examined included secretory ducts and acini, gland cisterns, teats, stromal and adipose tissues. Aquaporin 1 (AQP1) was localized in capillary endothelia throughout the mammary gland in addition to myoepithelial cells underlying teat duct epithelia. AQP2 and AQP6 were not detected and AQP9 was found only in leukocytes. AQP3 and AQP4 were observed in selected epithelial cells in the teat, cistern and secretory tubuloalveoli. AQP5 immunopositivity was prominent in the cistern. AQP3 and AQP7 were found in smooth muscle bundles in the teat, secretory epithelial cells and duct epithelial cells. These immunohistochemical findings support a functional role for aquaporins in the transport of water and small solutes across endothelial and epithelial barriers in the mammary gland and in the production and secretion of milk.

Fertility in dairy cows: bridging the gaps.

Dairy cattle are an integral part of agriculture worldwide, providing many products in addition to milk for the human population. The efficient production of these products is of utmost importance and high reproductive performance is absolutely crucial to this. In September 1999, Dr Michael Diskin led a committee (Dr Joseph M. Sreenan, Prof James Roche, Prof Maurice Boland and Dr Diarmuid O’Callaghan) to organize an extremely successful and informative occasional meeting ‘Fertility in the High-Producing Dairy Cow’, jointly with the British Society of Animal Science (BSAS) in Galway, Ireland, to address the important issue of declining reproductive performance in dairy cattle. The full papers were later published in an occasional publication by BSAS (2001). As discussed by Dr John Robinson in the conference summary, ‘ydelegates, after a starting point of uncertainty about how to deal with the problem [infertility], came away very well informed scientifically and, if perhaps with varying views as to the best way forward, more aware of the multidisciplinary research and development approach now being used to investigate it’. Dr Robinson concluded his summary by stating ‘Reversing this relentless decline in dairy cow fertility, while simultaneously sustaining high yields, is not going to be easyyyit is a challenge that will require great interchange of information and ideas between science, practice, research and development. The establishment of contacts and beginning of such interchange has been initiated during this [Galway, 1999] meeting and it is essential that this is sustained.’ Now, exactly 8 years later, it seemed time for those representatives from all disciplines involved in attempting to improve dairy cattle fertility to reconvene. Since 1999, the continued and well-documented decline in dairy cow fertility worldwide (Royal et al., 2000; Lucy, 2001; Mayne et al., 2002; Washburn et al., 2002; Lopez-Gatius, 2003; Swedish Dairy Association, 2005) has prompted new research into diverse aspects of dairy cow reproduction. To name but a few areas and publications, these include aspects such as genetics (Royal et al., 2002a and 2002b; Berry et al., 2003; Haile-Mariam et al., 2003; Philipsson and Lindhe, 2003; Wall et al., 2003; Holmberg and AnderssonEklund, 2006; Weigel, 2006; Hayhurst et al., 2007; Petersson et al., 2007; Veerkamp and Beerda, 2007), nutrition (Kadokawa and Martin, 2006; Robinson et al., 2006; Chagas et al., 2007; Friggens and Newbold, 2007; Wathes et al., 2007) Economics (Vargas et al., 2002; Esslemont, 2003; Santarossa et al., 2004; McGuirk et al., 2007), veterinary interventions and management (Refsdal, 2000; Roche et al., 2000; Sheldon et al., 2004; Bertoni et al., 2006; Diskin et al., 2006; Drillich et al., 2006; Mansell et al., 2006; Mee, 2007; Valergakis et al., 2007). It has also prompted the development of new technology and applications in the field. The purpose of this conference and subsequent publications is to provide an update on these activities since 1999 and to provide a forum for ‘bridging the gaps’ between the different disciplines involved. Invited and submitted theatre and poster sessions included new, up and coming presenters in addition to keynote speakers from across the globe, recognized as international experts in their field. As was the case at the 1999 meeting, the content is of direct interest to scientists, university lecturers, veterinarians, farm advisors and technical representatives working within the dairy industry as well as many dairy farmers. The following papers are a collection of research published at the conference. Dobson et al. (2008) highlight the factors predisposing to lowered fertility and disrupted oestrus in order to review ‘Why it is getting more difficult to successfully AI dairy cows’. The review by Morris and Diskin (2008), considers the current knowledge on embryo growth, development and survival in the cow and how these may be influenced by changes in uterine function and the concentration of systemic progesterone. Leroy et al. (2008), continues the investigations into the embryo reviewing a number of possible mechanisms linking negative energy balance to oocyte quality. Furthermore, in the event an embryo is formed after fertilization, the paper investigates whether the quality of early life is impaired. Interestingly, the prenatal environment is known to have a large impact not only

Detection of delayed cyclicity in dairy cows based on progesterone content in monthly milk samples

We examined whether infrequent milk sampling for progesterone analysis could be used as a management or diagnostic tool by the dairy farmer to predict delayed ovarian cyclicity in dairy cows. The data included 1040 lactations from 324 Swedish Red cows and 183 Swedish Holstein cows and were randomly divided into two datasets. A logistic regression model was fit to the first dataset and the model was then validated on the other dataset. The model was also validated using a British dataset comprising 1212 lactations from 1080 British Holstein-Friesian cows. The dependent variable was whether delayed ovarian cyclicity occurred or not, delayed ovarian cyclicity defined as progesterone levels below threshold value for the first 56 or 45 days postpartum in the Swedish or British dataset, respectively. The basic model included the effects of breed, parity, season and housing type. To the basic model various progesterone-based measurements were added. These were the interval from calving to commencement of luteal activity and the percentage of samples with luteal activity within 60 days after calving, using all samples in the databases or one sample per month. The accuracy of the conditional probability of delayed ovarian cyclicity calculated with the different models was obtained using receiver operating characteristic (ROC) curves and calculating the area under curve. Sensitivity and specificity were calculated for cut-off probabilities using the ROC analyses. The accuracy was highest (0.94-0.99) when including the progesterone measurements based on milk sampling for progesterone analysis 2-3 times per week. The accuracy was between 0.85 and 0.88 when the progesterone measurements with monthly milk sampling were added to the model and 0.76 or 0.67 with the basic model. This study clearly shows that infrequent milk sampling for progesterone analysis, such as once a month as in the regular milk recording system, could be used to predict delayed ovarian cyclicity in dairy cows. This increases the opportunity for earlier treatment of anovulatory dairy cows and may therefore decrease involuntarily extended calving intervals in the herd.

A protocol for initiating oestrus and ovulation early post partum in dairy cows

The objective of the present study was to evaluate the efficacy of a prostaglandin F 2α (PGF 2α ) and progesterone (P4) treatment in initiating oestrus and ovulation post partum (PP) in Holstein-Friesian cows. Using four herds, the treatment protocol consisted of a single intra-muscular injection of PGF 2α (Estrumate) between days 12 to 14 PP followed 48 h later by progesterone treatment via intra-vaginal CIDR insertion for a period of 7 days. Milk samples for progesterone determination were collected three times weekly from 7 to 65 days PP. The ovarian activity and reproductive performance of treated (T, no. = 153) animals and untreated control cows (C, no. = 315) were compared. Treatment was effective ( P P P P

Identification and quantification of factors affecting neonatal immunological transfer in dairy calves in the UK

The object of the study was to quantify the prevalence of failure of passive transfer in UK dairy farms and to identify variables that had a significant impact on the rate of immunological transfer. In a six-month study of 444 calvings from seven UK dairy farms, 26 per cent of calves failed to receive adequate immunoglobulin transfer as judged by a plasma total protein (pTP) concentration less than 5.6 g/dl. Colostrum immunoglobulin concentration, indirectly measured using Brix refractometry, showed wide variations with samples ranging from 10.3 to 34.7 Brix units. Thirty-seven per cent of samples were below the suggested cut-off Brix score for colostrum quality of 22 per cent. Potential associations between covariates and plasma protein concentration were investigated using multiple linear regression models. The covariate with the greatest impact on the pTP concentration was the farm on which the calf was born (P<0.05). A significant but small association was demonstrated between colostrum immunoglobulin concentration and calf pTP concentration (P<0.01). Multiple linear regression models suggested that the time of colostrum collection after calving, parity of the dam, and the individual farm were associated with the Brix measurements (P<0.05). This study suggested that veterinary review of colostrum protocols on farm with emphasis on prompt collection and dosing after calving remains a simple and effective measure to improve passive transfer and thus calf health on UK dairy farms.

Use of plasma samples to assess passive transfer in calves using refractometry: comparison with serum and clinical cut-off point

Complete or partial failure of passive transfer (FPT) of immunoglobulins in the neonatal calf can result in an increased susceptibility to disease, a higher risk of mortality and decreased growth rates (Robison and others 1988, Tyler and others 1998, Tyler and others 1999, Waldner and others 2009, Furman-Fratczat and others 2011). It is therefore critical to the survival and successful rearing of a calf that adequate passive transfer is achieved. Determining the amount of immunoglobulins a neonatal calf has received is a useful measure for veterinary surgeons and farmers to allow monitoring and standard setting for calf health and husbandry. Immunoglobulins may be measured directly by means of a radial immunodiffusion assay (Mancini and others 1965), and although this test is the industry gold standard, it is laboratory based, requiring a minimum of 24 hours to be performed and, thus, is not applicable to routine on-farm monitoring of adequacy of passive transfer. Measuring serum total proteins by hand-held refractometry offers a convenient, simple, rapid and inexpensive on-farm tool by which farmers and veterinary …