Embryo‐maternal Communication during the First Days of Embryonic Life

The mechanisms of embryo‐maternal communication during the first days of embryonic life are largely unknown. Using the bovine as a model, the aims of our study were to morphologically characterize the interaction between the pre‐implantation embryo and the epithelium of the maternal ampulla, isthmus and uterotubal junction by light and scanning electron microscopy. For this purpose, oviducts were removed from cows revealing a functional corpus luteum on day 3 after insemination. These were compared to oviducts removed on day 3 (metestrus) of the estrous cycle. Three days after insemination, the majority of the epithelial cells in the ampulla were secretory cells distinctly protruding into the oviductal lumen. Contrary the ampulla of cows on day 3 of the cycle predominantly revealed ciliated cells in the oviductal epithelium. As shown by Periodic Acid Schiff reaction (PAS) with and without amylase digestion, the secretory cells of the ampulla synthesized merely glycoproteins during metestrus, but large amounts of glycogen during pregnancy. In the isthmus no morphological differences were seen between pregnant and cyclic cows. The most conspicuous finding during pregnancy was seen in the uterotubal junction: Vital cumulus cells embedded in between epithelial cells had developed short cytoplasmic processes intensely contacting the epithelial uterine cells. The embryos obtained ex vivo were regularly covered with a thick layer of homogenous extracellular matrix. Contrary embryos produced in vitro– both with and without coculture with oviductal cells –revealed a clearly visible zona pellucida with spongy appearance and numerous pores. Our results imply that already during the first days of life there is intense interaction of the pre‐implantation embryo and the maternal genital tract part of which may be mediated by cumulus cells.     

Milk casein and fatty acid fractions in early lactation are affected by nutritional regulation of body condition score at the beginning of the transition period in primiparous and multiparous cows under grazing conditions

The objective was to evaluate the effect of body condition score (BCS) at 30 days before calving (−30 days) induced by a differential nutritional management, parity and week of lactation (WOL) on milk yield and composition, and milk casein and fatty acid composition. Primiparous and multiparous Holstein cows with high BCS (PH, n = 13; MH, n = 9) and low BCS (PL, n = 9; ML = 8) under grazing conditions were sampled at WOL 2 and 8 (before and after peak of lactation). Milk yield was greater in multiparous than in primiparous cows and tended to decrease from WOL 2 to 8 only in ML cows. Milk protein, fat and casein yields were greater in multiparous than in primiparous cows and decreased from WOL 2 to 8. Milk casein concentration in milk protein was greater in MH cows than in ML, PH and PL cows at WOL 2. Milk κ‐casein was greater, and β‐casein was less in multiparous than in primiparous cows. As lactation progressed, proportion of casein fractions were not altered. Only κ‐casein fraction was affected by BCS at −30 days as PL showed a higher concentration than PH. The de novo (4:0–15:1) and mixed‐origin fatty acids (16:0–16:1) in milk fat increased, whereas preformed fatty acids (≥17:0) decreased from WOL 2 to 8. Saturated (SAT) fatty acids tended to be greater and monounsaturated fatty acids (MUFA) were less in multiparous than in primiparous cows. High‐BCS cows had greater concentrations of polyunsaturated (PUFA), conjugated linoleic acid (CLA) as well as n‐6 and n‐3 fatty acids in milk fat than low‐BCS cows. The results indicate that casein and fatty acid fractions in milk were affected by parity and may be modified by a differential nutritional management during the pre‐calving period (BCS at −30 days) in cows under grazing conditions.     

MHC Class II+ (HLA-DP-like) Cells in the Cow Reproductive Tract: II. Immunolocalization of MHC Class II+ Cells in Oviduct and Vagina

The aim of this study was to determine and examine the distribution of major frequency MHC II+ cells in the oviduct and vagina of cows during the oestrous and dioestrus phases. Right oviduct (ampulla, isthmus) and vaginal samples taken from a total of twenty seven multiparous cows were used. Tissue samples were processed to obtain both cryostat and paraffin sections. Sections were stained immunocytochemically using StreptABC method using a specific monoclonal antibody to MHC II+ cell population. Intra-epithelial and subepithelial areas along with lamina propria, muscularis mucosae and serosa of both ampulla and isthmus and intra-epithelial/subepithelial areas and mucosae of vagina were examined for the presence of MHC II+ cells. The density of immune positive cells was determined using a subjective scoring system. MHC II+ cells were demonstrated in all areas examined in both oestrus and dioestrus. In oestrus, the density of MHC II+ cells decreased in subepithelial areas (in between the epithelial cells and the basal membrane) of isthmus, whereas the density of immune positive cells was increased in muscularis mucosae of isthmus ( P  < 0.05), lamina propria and muscularis mucosae of ampulla ( P  < 0.05) as well as in the mucosae of vagina ( P  ≤ 0.005). This study indicates that the density of MHC II+ cells observed in the oviduct and vagina increases in the majority of areas examined due to the effect of oestrogen.     

Laser Micro-dissection and Quantitative RT-PCR as a Tool for Cell Identification

The mechanisms of embryo-maternal communication during the first days of embryonic life are largely unknown. Using the bovine as a model, the aims of our study were to morphologically characterize the interaction between the pre-implantation embryo and the epithelium of the maternal ampulla, isthmus and uterotubal junction by light and scanning electron microscopy. For this purpose, oviducts were removed from cows revealing a functional corpus luteum on day 3 after insemination. These were compared to oviducts removed on day 3 (metestrus) of the estrous cycle. Three days after insemination, the majority of the epithelial cells in the ampulla were secretory cells distinctly protruding into the oviductal lumen. Contrary the ampulla of cows on day 3 of the cycle predominantly revealed ciliated cells in the oviductal epithelium. As shown by Periodic Acid Schiff reaction (PAS) with and without amylase digestion, the secretory cells of the ampulla synthesized merely glycoproteins during metestrus, but large amounts of glycogen during pregnancy. In the isthmus no morphological differences were seen between pregnant and cyclic cows. The most conspicuous finding during pregnancy was seen in the uterotubal junction: Vital cumulus cells embedded in between epithelial cells had developed short cytoplasmic processes intensely contacting the epithelial uterine cells. The embryos obtained ex vivo were regularly covered with a thick layer of homogenous extracellular matrix. Contrary embryos produced in vitro – both with and without coculture with oviductal cells –revealed a clearly visible zona pellucida with spongy appearance and numerous pores. Our results imply that already during the first days of life there is intense interaction of the pre-implantation embryo and the maternal genital tract part of which may be mediated by cumulus cells.     

Infiltration of local immune cells in the sow reproductive tracts after intra-uterine and deep intra-uterine insemination with a reduced number of spermatozoa is less than conventional artificial insemination

The present study investigated the infiltration of leukocyte subpopulations in the utero-tubal junction (UTJ) and each part of the oviducts at about 24 hr after intra-uterine insemination (IUI) and deep intra-uterine insemination (DIUI) compared to conventional artificial insemination (CAI) in sows. Fifteen crossbred Landrace x Yorkshire multiparous sows were used (CAI, n=5; IUI, n=5; DIUI, n=5). The sperm dose contained 3,000 × 10(6) (100 ml), 1,000 × 10(6) (50 ml) and 150 × 10(6) (5 ml) motile spermatozoa for CAI, IUI and DIUI, respectively. The sows were inseminated with extended fresh semen at 6 to 8 hr prior to the expected time of ovulation. At 25.2 ± 1.6 hr after insemination, the oviducts and the UTJ were collected. The tissue samples of UTJ, caudal isthmus, cranial isthmus and ampulla were transversely cut to a thickness of 5 μm and stained with H&E. The total numbers of lymphocytes, neutrophils, macrophages, eosinophils and plasma cells were determined under light microscope. It was found that the numbers of lymphocytes, eosinophils and macrophages after CAI, IUI and DIUI were not significantly different (P>0.1) in both epithelial and sub-epithelial connective tissue layer of the UTJ, caudal isthmus, cranial isthmus and ampulla. Intra-epithelial neutrophils in the UTJ were higher than cranial isthmus (P<0.05) and ampulla (P<0.05). In the UTJ, the intra-epithelial neutrophil in the CAI group was higher than DIUI group (P<0.01). Plasma cells in sub-epithelial layer of the endosalpinx in the CAI group were higher than DIUI group (P<0.05) and tended to be higher than the IUI group (P=0.08). In conclusion, compared to CAI, IUI and DIUI do not influence the infiltration of lymphocytes, macrophages and eosinophils in the UTJ and the oviduct prior to fertilization. But a lower number of neutrophils in the intra-epithelial layer of the UTJ and plasma cells in the sub-epithelial layers of the oviduct was observed in the DIUI group compared to CAI.     

Chlamydia abortus in Cows Oviducts,Occasional Event or Causal Connection?

Fifty‐seven genital tracts of regularly slaughtered culled Piedmontese cows, aged 7.4 ± 4.3 years (mean ± SD), range: 2.6–15.6 years, were grossly and microscopically examined. DNA extracted from oviducts was subjected to PCR to evaluate the presence of Chlamydia spp. The 15 PCR‐positive oviducts were subjected to Sanger sequencing and showed the presence of Chamydia abortus, with an identity range between 99 and 100%. Nine of the PCR‐positive samples belonged to the 24 animals with a normal macroscopic appearance of the whole genital tract (percentage of positive oviducts in normal genital tracts 9/24 = 37.5%), while six belonged to the 33 genital tracts with lesions in one or more organs (percentage of positive oviducts in pathological genital tracts 6/33 = 18.1%); of these, a single animal had salpingitis. The detection of C. abortus in bovine oviducts is of particular interest because it has never been previously investigated or reported.     

Sperm localization in the oviducts of artificially inseminated dairy cattle

Eight animals, 3 heifers and 5 primiparous cows, were artificially inseminated by intrauterine deposition of frozen-thawed semen. The insemination dose comprised 20×10⁶ or 200 × 10⁶ spermatozoa, frozen in French mini straws. Four animals were inseminated at fixed time interval (72 or 84 h) after cloprostenol injection. The remaining 4 animals were inseminated in spontaneous oestrus. Slaughter took place 2 or 12 h after insemination. After fixation the oviducts were cut into segments, which were serial-sectioned and stained. Six sections per segment were examined under the microscope for sperm recovery.The number of spermatozoa recovered from the oviducts varied considerably among animals. Recovery was poor (less than 50 spermatozoa) in 4 animals. Recovery was low when insemination took place in induced oestrus and with the lower sperm number (20×10⁶). In animals in which more than 50 spermatozoa were found the distribution varied both between animals and between oviducts within the same animal. Overall, more spermatozoa were found in the lower (UTJ, isthmus and AIJ) than in the upper (ampulla) parts of the oviducts. In 3 out of 4 animals more spermatozoa were recovered from the left than from the right oviduct. Only in 1 animal were the majority of spermatozoa found in the oviduct ipsilateral to the follicle-bearing ovary.     

Exploring relationships between body condition score,body fat,activity level and inflammatory biomarkers

Obesity is associated with inflammatory disorders in humans, including degenerative joint disease. While obesity is endemic in horses, its relationship to equine degenerative joint disease has not been explored. The current study sought to describe relationships between: body weight (BW), body condition score (BCS), lameness grade (AAEP), total body fat mass (kg; FM) and fat per cent (FP) [multifrequency bioelectrical impedance analysis (mfBIA)], age, gender, activity level (AL), synovial fluid (SF) and plasma (PL) PGE₂ and glycosaminoglycan (GAG) in horses. During this field investigation, the BCS (of nine) of 54 horses at multiple farms in southern Ontario, Canada, was determined. Horses were categorized as thin (BCS=3/9; n = 6), moderate (BCS=4 or 5/9; n = 18), overweight (BCS=6 or 7/9; n = 19) or obese (BCS=8 or 9/9; n = 11). Total fat mass (kg) and body fat% was measured using mfBIA, lameness was assessed (AAEP lameness scale) and synovial fluid was collected via aseptic arthrocentesis from the left intercarpal joint for assessment of inflammatory biomarkers (PGE₂, GAG). Means were compared with a one‐way ANOVA; correlation coefficients were calculated using a Spearman Rank Order Correlation to reveal correlations between variables. BCS was positively correlated with BW, FM, FP, AL and PL‐PGE₂. BW was also significantly positively correlated with PL‐PGE₂. It is concluded that BCS is significantly correlated with PL‐PGE₂, due in part to the combined effect of AL and body condition. Net inflammatory effects of body fat on risk for joint disease require further study.     

Number of Spermatozoa in the Crypts of the Sperm Reservoir at About 24 h After a Low‐Dose Intrauterine and Deep Intrauterine Insemination in Sows

The aim of this study was to investigate the number of spermatozoa in the crypts of the utero‐tubal junction (UTJ) and the oviduct of sows approximately 24 h after intrauterine insemination (IUI) and deep intrauterine insemination (DIUI) and compared with that of conventional artificial insemination (AI). Fifteen crossbred Landrace × Yorkshire (LY) multiparous sows were used in the experiment. Transrectal ultrasonography was performed every 4 h to examine the time of ovulation in relation to oestrous behaviour. The sows were inseminated with a single dose of diluted fresh semen by the AI (n = 5), IUI (n = 5) and DIUI (n = 5) at approximately 6–8 h prior to the expected time of ovulation, during the second oestrus after weaning. The sperm dose contained 3000 × 10⁶ spermatozoa in 100 ml for AI, 1,000 × 10⁶ spermatozoa in 50 ml for IUI and 150 × 10⁶ spermatozoa in 5 ml for DIUI. The sows were anaesthetized and ovario‐hysterectomized approximately 24 h after insemination. The oviducts and the proximal part of the uterine horns (1 cm) on each side of the reproductive tracts were collected. The section was divided into four parts, i.e. UTJ, caudal isthmus, cranial isthmus and ampulla. The spermatozoa in the lumen in each part were flushed several times with phosphate buffer solution. After flushing, the UTJ and all parts of the oviducts were immersed in a 10% neutral buffered formalin solution. The UTJ and each part of the oviducts were cut into four equal parts and embedded in a paraffin block. The tissue sections were transversely sectioned to a thickness of 5 μm. Every fifth serial section was mounted and stained with haematoxylin and eosin. The total number of spermatozoa from 32 sections in each parts of the tissue (16 sections from the left side and 16 sections from the right side) was determined under light microscope. The results reveal that most of the spermatozoa in the histological section were located in groups in the epithelial crypts. The means of the total number of spermatozoa in the sperm reservoir (UTJ and caudal isthmus) were 2296, 729 and 22 cells in AI, IUI and DIUI groups, respectively (p < 0.01). The spermatozoa were found on both sides of the sperm reservoir in all sows in the AI and the IUI groups. For the DIUI group, spermatozoa were not found on any side of the sperm reservoir in three out of five sows, found in unilateral side of the sperm reservoir in one sow and found in both sides of the sperm reservoir in one sow. No spermatozoa were found in the cranial isthmus, while only one spermatozoon was found in the ampulla part of a sow in the IUI group. In conclusion, DIUI resulted in a significantly lower number of spermatozoa in the sperm reservoir approximately 24 h after insemination compared with AI and IUI. Spermatozoa could be obtained from both sides of the sperm reservoir after AI and IUI but in one out of five sows inseminated by DIUI.     

Effect of fat supplementation during transition period on plasma leptin and non‐esterified fatty acid concentrations in Holstein cows

The objective of this experiment was to investigate the effect of fat supplementation during the transition period on pre and postpartum body weight (BW), body condition score (BCS), non‐esterified fatty acids (NEFA), glucose and leptin concentrations in Holstein cows. Holstein cows (n = 15) received a low fat diet (LF; 1.61 Mcal net energy for lactation (NEL)/kg of dry matter [DM]), moderate fat diet (MF; 1.68 Mcal NEL/kg DM) or a high fat diet (HF; 1.74 Mcal NEL/kg DM) for 4 weeks prior to calving. All cows were fed similar lactation diets ad libitum (1.74 Mcal NEL/kg DM) for 30 days after calving. Increasing diet energy density during transition period had no effect on prepartum DMI, BCS, BW, glucose and NEFA concentrations (P > 0.05); but leptin concentrations and energy balance (EB) were affected by treatments (P < 0.05). Animals fed HF had less plasma leptin prepartum. After parturition, BW, milk production, milk fat, protein, urea nitrogen and plasma glucose concentrations were affected by prepartum diets (P < 0.05). Fat supplementation prepartum did not affect postpartum NEFA. In conclusion, prepartum fat supplementation decreased leptin concentration prepartum.     

荷斯坦牛皮肤褶皱厚度及体况评分性状遗传分析

本研究通过对荷斯坦牛颈侧部、肋部和后乳房基部皮肤褶皱厚度（分别简称为颈部、肋部和乳房皮褶厚）及体况评分（body condition score,BCS）进行大群测定,旨在探究荷斯坦牛不同部位皮肤褶皱厚度和BCS的群体特征,并建模估计荷斯坦牛不同部位皮肤褶皱厚度及BCS的遗传参数。本研究于2015—2020年夏季测定了北京地区12个规模化牧场10 915头泌乳荷斯坦牛的皮肤褶皱厚度,同时对测定牛群进行了体况评分,使用单性状和四性状动物模型分别对颈部皮褶厚、肋部皮褶厚、乳房皮褶厚和BCS进行遗传分析并估计遗传参数,并计算了上述4个性状与奶牛寿命和繁殖等重要功能性状之间的近似遗传相关。结果显示,荷斯坦牛乳房皮褶厚、颈部皮褶厚、肋部皮褶厚和体况评分分别为（7.49±1.45） mm、（7.27±1.34） mm、（11.74±1.90） mm和（2.94±0.79）;乳房皮褶厚和颈部皮褶厚为中等遗传力性状,遗传力分别为0.11和0.15;肋部皮褶厚和体况评分为中高遗传力性状,遗传力分别为0.28和0.22;不同部位的皮褶厚之间存在中高遗传相关,颈部和肋部皮褶厚之间的遗传相关最高（0.69）,颈部和乳房皮褶厚之间的遗传相关最低（0.21）;BCS与不同部位皮褶厚之间遗传相关的差异较大,BCS与颈部、肋部皮褶厚之间为正遗传相关（0.28、0.13）,BCS与乳房皮褶厚之间为负遗传相关（-0.25）;体况评分和皮褶厚性状与部分重要功能性状之间存在中等遗传相关。本研究对奶牛3个部位的皮肤褶皱厚度和BCS性状进行了遗传分析,研究获得的遗传参数有助于通过皮肤褶皱厚度和BCS理解奶牛体脂沉积的遗传基础,助力我国奶牛的平衡育种。     

Histological Characteristics of the Equine Oviductal Mucosa at Different Reproductive Stages

The objective of this work was to study cellular changes in the epithelium of the mare’s oviduct. Oviductal samples were taken from mares at different reproductive stages for optical microscopy and Hoechst 33258 staining. Glandular-like structures were observed in 100% of the oviducts. These structures were of the tubular type and were formed by ciliated and nonciliated epithelial cells arranged in a way similar to the epithelial surface. The amount of structures decreased progressively from the ampulla to the isthmus, but did not change through the different reproductive stages. Histological changes in the epithelium of the oviduct were observed associated with the reproductive stages. In the ampulla, the amount of ciliated cells decreased in the anovulatory phase compared with other reproductive stages. Cords of connective tissue lined by epithelium (trabeculae) and dividing completely the lumen of the oviduct were found in 50% of the oviducts. Epithelial cells projected toward the lumen as large vesicles of cytoplasm, sometimes containing a nucleus. The amount of cells presenting nuclear protrusion varied throughout the oviduct, with highest incidence in the ampulla, decreasing progressively toward the isthmus (P < .05). In addition, nuclear protrusions were higher in number during the anovulatory and luteal phases than in the other reproductive stages (P < .05). These nuclear protruding cells appeared to be extruding from the epithelium and showed no signs of apoptosis based on the histological and fluorescent stains used. The existence of these gland-like structures in the oviductal mucosa should be considered when studying the oviductal physiology in mares.     

Immunolocalization of nerve growth factor (NGF) and its receptors (TrkA and p75LNGFR) in the reproductive organs of Shiba goats

The objective of this study was to determine the immunolocalization of NGF and its receptors (TrkA and p75LNGFR) in the reproductive tract of the Japanese Shiba goats. Five adult goats were used in this study and sections of ovaries, uteri and oviducts were immunostained by the avidin-biotin-peroxidase complex method (ABC). The results showed that NGF and its receptors (TrkA and p75LNGFR) were expressed in granulosa cells, theca cells, interstitial cells and lutein cells in ovaries. Immunoreactions for NGF, TrkA and p75LNGFR were also detectable in epithelial cells and muscle cells of the ampulla and isthmus of the oviduct, and in epithelial cells and uterine glands of the uterus. These results strongly suggest autocrine and paracrine regulation of reproductive function by NGF in the reproductive tract of female Shiba goats.     

Effect of body condition score and reuse of progesterone‐releasing intravaginal devices on conception rate following timed artificial insemination in Nelore cows

This study had the aim of investigating the efficiency of timed artificial insemination (TAI) through the progesterone‐releasing intravaginal device (PRID), used in new condition and for the second and third times in Nelore cows. The effects of device reuse and body condition score (BCS) on the conception rate (CR) were evaluated in 1,122 multiparous Nelore cows (mean BCS of 2.7 ± 0.4), which were randomly distributed into three groups that received new (n = 330), once (n = 439) and twice used (n = 353) PRID. Among the 1,122 females that underwent TAI, 573 became pregnant, thus representing an overall CR of 51.06%. Cows with BCS between 2.75 and 4.0 had greater (p < .0001) CR (69.75%) than cows with BSC of 2.0–2.5 (32.98%). It was observed that the CR through using PRID was 60.00%, 51.71% and 41.93% for new, once and twice used PRID, respectively, with difference between all groups (p < .0001). Under tropical conditions, animals with BCS greater than 2.5 had a higher CR, and the CR decreased proportionally with the number of times that the PRID had been used.     

Effects of season and body condition on appetite, body mass and body composition in ad libitum fed pony mares

Changes in appetite, body mass (BM), body condition score (BCS), direct (ultrasonographic) and indirect (deuterium oxide dilution technique) measures of body fat were monitored in Welsh Mountain pony mares (n = 11, 5–19 years of age) offered ad libitum access to a complete diet (gross energy 16.9 ± 0.07 MJ/kg dry matter) for 12 weeks during summer (n = 6; 246 ± 20 kg) and winter (n = 5; 219 ± 21 kg). At the outset, each group comprised two thin (BCS 1–3/9), moderate (BCS 4–6/9) and obese (BCS 7–9/9) animals.For ponies that were non-obese at the outset, BM was gained more rapidly (P = 0.001) in summer (0.8 ± 0.1 kg/day) than winter (0.6 ± 0.0 kg/day). This was associated with a seasonal increase in dry matter intake (DMI) which became maximal (summer, 4.6 ± 0.3% BM as DMI/day; winter, 3.5 ± 0.1% BM as DMI/day) during the second month. The appetite of the obese ponies was half that reported for non-obese animals in the summer and BM remained constant irrespective of season.Body ‘fatness’ increased progressively for non-obese but not obese ponies. Body fat content was exponentially associated with increasing BCS but BCSs >6 were not useful indicators of actual body fat. Endogenous circannual mechanisms to suppress winter weight gain were insufficient to prevent the development of obesity in ad libitum fed ponies.     

Effect of nutrient levels during the far‐off period on postpartum productivity in dairy cows

The present study aimed to determine the effects of differing nutrient levels during the far‐off period on postpartum metabolism and milk production in lactating cows. Twenty‐six multiparous cows were assigned to three dietary treatments in the far‐off period: a low‐energy diet (L, n = 9, 80% intake of the total digestible nutrients requirement), a moderate‐energy diet (M, n = 8, 105%) and a high‐energy diet (H, n = 9, 130%). During the close‐up period, all cows were provided with 105% intake. After parturition, all cows were fed a lactation diet. The BCS recovery was slow, and low milk yield was found in the H group. In the L group, BCS recovery was favorable after parturition, and lactation persistence was increased. The L group had low rumen endotoxin activity and a high initial ovulation rate after parturition. These findings indicate that a high‐energy diet during the far‐off period has a deleterious effect on milk production. In contrast, the restricted diet in the far‐off period increased adaptability with respect to peri‐parturition metabolic changes, improved the post‐parturition nutritional state, and increased milk production. Furthermore, it suggests that the nutrient levels in the far‐off period affect rumen endotoxin activity and reproductive function after parturition.     

Ovarian follicular recruitment,granulosa cell steroidogenic potential and growth hormone/insulin-like growth factor-I relationships in suckled beef cows consuming high lipid diets: Effects of graded differences in body condition maintained during the puerperium

The effects of graded differences in body condition score (BCS) on ovarian follicular development, granulosa cell steroidogenic potential, and growth hormone (GH)-insulin-like growth factor-I (IGF-I) relationships were examined during the puerperium in beef cows fed high fat diets. Cows (n = 36) were allocated randomly about 90 d before expected calving to dietary treatments that resulted in BCS of 3 (very thin), 4 (thin), 6 (optimal) and 8 (obese) at parturition. Body weight and BCS were maintained after parturition by adjusting individual intakes of forage throughout the 17-d experiment, and all cows were fed a high lipid supplement (soybean oil; 0.44 kg/500 kg body weight) during this period. Follicular development in BCS 3 and 4 lagged behind that of BCS 6 and 8 throughout most of the study; however, cows in BCS 4 developed numbers of medium and large follicles by day 15 postpartum that were comparable to those of cows in greater BCS. Mean concentrations of total cholesterol (TCH) and total triglycerides (TG) in serum were greater (P < .05) for cows in BCS 8 vs. 3, 4 and 6 through days 12 (TCH) and 16 (TG) postcalving, respectively. High-density lipoprotein cholesterol (HDL-CH), progesterone and estradiol-17β concentrations in follicular fluid were not affected by BCS at ovariectomy (day 17 postpartum). Addition of insulin and low-density lipoprotein (LDL) to culture media maximized (P < .05) production of progesterone by granulosa cells, but in vivo BCS treatments had no effect. Serum GH concentrations were elevated (P < .05) in cows in BCS 3 and 4 compared to those in BCS 6 and 8 throughout the puerperium. Serum IGF-I tended (P < .10) to increase during the first few days after parturition, and both serum and follicular fluid IGF-I increased (P < .02 and P < .001, respectively) with increasing BCS. Data indicate that cows calving in BCS < 4, and fed such that weight and BCS do not increase, are unlikely to respond to short-term dietary fat supplementation.     

Influence of nutrition and body condition on pituitary, ovarian, and thyroid function of nonlactating beef cows

Nonpregnant Hereford cows (n = 70) were used to determine the effect of nutrient intake and body condition on reproductive and thyroid function. Body condition scores (BCS; 1 = emaciated; 9 = obese) of cows averaged 5.0 +/- .2 on July 1, and cows were fed for 4 mo either to lose weight and BCS (thin; n = 22), to maintain weight and BCS (moderate; n = 24), or to gain weight and BCS (fat; n = 24). After November 1, cows received a complete ration to maintain weight and BCS. Cows were slaughtered in December (six thin, eight moderate, and eight fat cows) or the subsequent March (16 cows per group). Before slaughter, cows were given two injections of prostaglandin F2 alpha (PGF) 11 d apart. Six days after the second PGF injection, cows were simultaneously treated with 100 micrograms of gonadotropin releasing hormone (GnRH; i.m.) and 100 micrograms of thyrotropin releasing hormone (TRH; i.v.) and serum samples were obtained. The BCS of cows at slaughter (8 d after PGF) averaged 3.4, 5.3, and 7.1 (P less than .01) and carcass energy content averaged 243, 432, and 714 Mcal (P less than .01) for thin, moderate, and fat cows, respectively. Wet ovarian (P less than .001) and corpora lutea (P less than .01) weights were heavier for fat cows. Content of LH in the pituitary gland and concentrations of thyroxine (T4) in serum after GnRH/TRH were not influenced by nutrient intake or BCS. However, thin cows had greater concentrations (P less than .05) of LH in serum after GnRH/TRH than did moderate or fat cows. We conclude that nutrient intake and body energy reserves of beef cows influenced ovarian function and LH in serum after treatment with GnRH.