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PubMed2004

Effects of bifenthrin on Daphnia magna during chronic toxicity test and the recovery test.

The acute and chronic toxic effects of bifenthrin on Daphnia magna were studied. The results showed that 24 h-EC50, 48 h-LC50 and 96 h-LC50 of bifenthrin on D. magna were 3.24, 12.40 and 1.40 microg/L respectively. And the LOEC and NOEC of bifenthrin were 0.02 and 0.004 microg/L respectively. The recovery test of bifenthrin on Daphnia magna was presented. Daphnia magna (F0 generation) were exposed during 21 d to different bifenthrin concentrations. Offspring (animals from the first and third brood: F1 (1st) and F1 (3rd), respectively) were transferred to a free pesticide medium during a 21 d recovery period. In this recovery study, survival, growth, reproduction (mean total young per female, onset of reproduction and number broods per female) and the intrinsic rate of natural increase (r) were assessed as parameters. Reproduction such as number of young per female as well as length was still reduced in F1 (1st) generation daphnids from parentals (F0) exposed to the bifenthrin. However F, (3rd) individuals from parentals exposed to pesticide concentrations were able to restore reproduction when a recovery period of 21 d was allowed, but the length of F, (3rd) from parentals exposed to the 0.5 and 0.75 microg/L bifenthrin concentration was still significantly effected (P < 0.05).

Animals↗

PubMed2026

The Puerperium in the Modern Dairy Cow: A Review.

The puerperium represents a critical physiological period during which the bovine reproductive tract transitions from pregnancy to renewed fertility. In the modern high-producing dairy cow, this transition is challenged by profound metabolic, endocrine, immunological, and structural demands that collectively influence uterine health, ovarian function, and subsequent reproductive performance. This review examines current understanding of the physiology of the puerperium in dairy cattle, with particular emphasis on uterine involution, immune clearance of postpartum contamination, endocrine regulation, and resumption of ovarian cyclicity. Further, it contrasts high-yielding Holsteins with fertility selected dairy populations. Normal uterine involution involves coordinated myometrial contraction, tissue remodelling, endometrial regeneration, and tightly regulated inflammatory responses. Failure of these processes predisposes cows to postpartum uterine disorders, including retained fetal membranes, metritis, endometritis (purulent vaginal discharge with cytological confirmation), and pyometra, which remain major contributors to subfertility and economic loss. Central to the pathophysiology of puerperal disease is negative energy balance, which disrupts immune competence, alters hepatic steroid metabolism, impairs ovarian signalling, and compromises oocyte and embryo quality. Emerging evidence highlights the complex interplay between metabolism, immunity, and the uterine microbiome, shifting current perspectives away from pathogen-centric models toward host resilience. Advances in biomarkers, genomic selection, and precision monitoring offer new opportunities for targeted reproductive management. Ultimately, optimisation of transition period management remains the cornerstone of supporting physiological puerperal recovery and sustaining reproductive efficiency in modern dairy systems.

Animals↗

PubMed1999

Thyroid function and effects on reproduction in ewes exposed to the organochlorine pesticides lindane or pentachlorophenol (PCP) from conception.

There is concern over the potential endocrine-modulating effects of long-term exposure to pesticides. In this study, ewe lambs were exposed to lindane and pentachlorophenol (PCP) from conception to necropsy at 67 wk. of age. The ewe lambs (and their mothers) were given untreated feed (n = 6) or feed treated with 1 mg/kg body weight/day of lindane (n = 8) or PCP (n = 13). Estrus was synchronized at 32 wk. of age, and ewe lambs were exposed to vasectomized rams. Ewe lambs were then exposed to intact rams during the following two natural estrous periods and subsequent reproductive performance was monitored. Serum was collected every 2 wk. during development, daily during the synchronized cycle and frequently (every 15-60 min) for 6-18 h either with or without stimulation with thyroid-stimulating hormone (TSH) during the synchronized luteal phase or TSH/thyroid-releasing hormone (TRH) at 65-66 wk of age. Ewe lambs fed a PCP-treated diet had a significantly reduced serum concentration of both T4 and free T4, and a reduction in the magnitude and duration of the T4 and free T4 response to TSH, despite normal endogenous levels of TSH and a normal TSH response to TRH. PCP exposure had a less detrimental influence on unstimulated T3 levels; however, the T3 (but not reverse T3) response to TSH was markedly reduced in PCP-treated ewe lambs. Ewe lambs given lindane also had a significantly reduced serum concentration of T4; however, despite continued exposure to lindane, T4 levels returned to normal by 10 wk. of age. Detrimental effects on reproductive function were only seen following estrous synchronization when both PCP and lindane exposure reduced the number of corpora lutea (CL) and total CL volume and increased luteinizing hormone (LH) pulse frequency. In addition, lindane-treated ewes had shorter estrous cycles and lower luteal progesterone concentrations. No marked effects of pesticides were seen on fertility following mating during natural estrous periods. In conclusion, the pesticides affected reproduction only after estrous synchronization, whereas PCP consistently disrupted thyroid function, most likely through a direct effect on the thyroid gland.

Animals↗

PubMed1983

Suprachiasmatic nuclei influence circannual and circadian rhythms of ground squirrels.

Golden-mantled ground squirrels, maintained under constant conditions of photoperiod and temperature sustained lesions of the suprachiasmatic nuclei (SCN) or of the medial basal hypothalamus. Destruction of the SCN eliminated or disrupted circadian activity rhythms and shortened the period of the circannual reproductive cycle. Circannual body weight cycles were eliminated or disrupted in several SCN-lesioned animals and one squirrel had a 3- to 5-mo body weight rhythm; however, most SCN-lesioned squirrels with disrupted circadian activity cycles manifested normal circannual body weight rhythms. The SCN are important for circadian organization of locomotor activity of this diurnal rodent, but the generation and expression of circannual body weight and reproductive rhythms can proceed in the absence of coherent circadian organization. The SCN are less essential for the generation and expression of circannual than of circadian cycles.

Animals↗

PubMed1984

Effect of shortened photosynthetic period on C-assimilate translocation and partitioning in reproductive soyeans.

Starch accumulation rate in leaves of vegetative soybeans is inversely related to the length of the daily photosynthetic period. However, it is not known whether a similar response would be observed during reproductive growth. Soybeans (Glycine max L. Merr. cv Amsoy 71) were grown to three stages of reproductive growth (beginning seed, mid seed-fill, and late seed-fill) under 12-hour daylengths, and then shifted to 6-hour photosynthetic periods (12-hour photoperiods) for 4 days. One and 4 days after treatment, a mid-canopy leaf was pulsed with (14)CO(2), and sampled for radiolabeled starch and water-soluble compounds at 0.5, 1, 3, 9, and 21 hours after labeling.Plants exposed to the 6-hour photosynthetic periods at the beginning seed stage retained and incorporated significantly more label as starch than did those given 12-hour photosynthetic periods. However, plants exposed to the shortened photosynthetic periods at the late seed-fill stage partitioned less label into starch. Plants exposed at mid seed-fill gave a variable response.Shortened photosynthetic periods resulted in preferential partitioning of recently fixed carbon to the seed at the expense of the pod wall. The results of these experiments suggest that the increased sink demand present during late reproductive growth may be of greater importance in control of leaf starch accumulation than is the length of the daily photosynthetic period.

Journal Article↗

PubMed2003

[Birth rates and reproductive risk in adolescents in Chile, 1990-1999].

OBJECTIVE: For Chilean teenage mothers under 15 years old and from 15 to 19 years old, to evaluate the trends in birth rates and reproductive risk for the period of 1990-1999. METHODS: A database was constructed using data from the Demography Yearbook (Anuario de demografía) volumes published by Chile's National Institute of Statistics (Instituto Nacional de Estadísticas) for 1990-1999. From that database we calculated the trends in the number of live births and in the rates of maternal mortality, late fetal mortality, neonatal mortality, and infant mortality among the teenage mothers under 15 and from 15 to 19 years old. We calculated the risk odds ratio (OR) for both of those age groups in comparison with women from 20 to 34 years old. The groups were compared using Fisher's exact test or the chi-square test, and the analysis of trends in the period studied was carried out with Pearson's correlation, with an alpha level of 0.05. RESULTS: In the period studied, for the teenage mothers under age 15, the respective rates for maternal mortality, late fetal mortality, neonatal mortality, and infant mortality were 41.9 per 100 000 live births, 5.1 per 1 000 live births, 15.2 per 1 000 live births, and 27.4 per 1 000 live births. For the adolescents from 15 to 19 years, the corresponding rates were 19.3, 4.1, 8.1, and 16.6; for the women 20-34 years old, they were 26.8, 5.0, 6.7, and 12.1. The adolescents under 15 had higher risks of maternal mortality (OR = 1.56; 95% confidence interval (CI): 0.50 to 4.31; P = 0.372) and of fetal mortality (OR = 1.02; 95% CI: 0.76 to 1.36; P = 0.890), but those differences were not statistically significant. However, the younger adolescents did have significantly higher risks of neonatal mortality (OR = 2.27; 95% CI: 1.92-2.68; P < 0.0001) and of infant mortality (OR = 2.39; 95% CI: 2.04 to 2.62; P < 0.0001). In comparison to the women 20-34 years old, the teenage mothers from 15 to 19 years old had significantly lower risks of maternal mortality (OR = 0.72; 95% CI: 0.56 to 0.92; P < 0.008) and of fetal mortality (OR = 0.81; 95% CI: 0.77 to 0.86; P < 0.0001) but significantly higher risks of neonatal mortality (OR = 1.20; 95% CI: 1.16 to 1.25; P < 0.0001) and of infant mortality (OR = 1.38; 95% CI: 1.35 to 1.42; P < 0.0001). Among both the older teenage mothers and the mothers 20-34 years old there was a significant downward trend in maternal, fetal, neonatal, and infant mortality rates in the period studied; in the younger adolescents only neonatal mortality and infant mortality declined significantly. There was a rising trend in the number of live births among the two groups of teenage mothers, but that trend was statistically significant only for the mothers under 15; among mothers 20-34 years old there was a statistically significant downward trend. CONCLUSIONS: In the period studied, the Chilean teenage mothers faced greater reproductive risk than did the women 20-34 years old. The number of live births among teenage mothers tended to rise during the 1990-1999 period, but the change was significant only for the mothers under age 15. These results point to the need to develop programs that improve both sex education and birth control practices starting in early adolescence.

Adolescent↗

PubMed1988

Egg-laying pattern of the semi-domesticated helmeted guinea fowl (Numida meleagris galeata).

1. Studies on the egg laying pattern of the semi-domesticated helmeted guinea fowl showed that the birds laid eggs between 06.00 and 20.00 h local time (05.00 to 19.00 h GMT). 2. More (67.9%) were laid in the evenings (15.00 to 20.00 h) than at any other period. 3. There were two distinct periods in the reproductive cycle: a breeding season which began in April and ended in September, and a resting or non-breeding period between October and March. 4. Sequence length was predominantly of 4 eggs and July was the month of peak egg production.

Animals↗

PubMed2005

[Adverse effects of nonylphenol on the reproductive development of F1 male SD rats in sexual maturation period].

OBJECTIVE: To investigate the adverse effects of perinatal exposure to nonylphenol (NP) on the reproductive development of F1 male SD rats in sexual maturation period. METHODS: The pregnant rats were randomly divided into control, 50 mg/kg, 100 mg/kg, and 200 mg/kg NP groups respectively. NP was administered to dams by gavage from gestation day 7 to weaning period. Rat pups were sacrificed at postnatal day 55. The concentration of serum testosterone was measured by radioimmunoassay. The epididymis was subjected to the determination of sperm count and motility while the testis was submitted to histopathological and immunohistochemical analyses. RESULTS: Compared with control, the concentration of serum testosterone, sperm count and motility in the 200 mg/kg NP dose groups significantly decreased (P < 0.05), and the histopathological examination revealed that NP-treated groups had higher rates of maldeveloped siminiferous tubules, smaller amount of Sertoli cells and weaker spermatogenesis. The expression of proliferative cell nuclear antigen (PCNA) significantly decreased in the 200 mg/kg NP dose groups (P < 0.05). The expression of Arom in 100 mg/kg and 200 mg/kg NP dose groups was lower than that in control. There was no significant difference in ER expression between the control and NP-treated groups. CONCLUSION: These findings indicated that 200 mg/kg Nonylphenol apparently damaged the reproductive development of F1 male SD rats in the sexual maturation period.

Animals↗

PubMedDate not supplied

[The role of steroid hormones in the sexual and agonistic behaviors of male silver foxes].

Silver fox males were tested for sexual and agonistic behaviour after introduction of a female at different stages of the reproductive cycle. The high level of aggressive interactions between male and female and no mountings were observed out of the reproductive season. During the reproductive season, the introduction of anoestrus female did not affect the aggressive behaviour but increased the number of mountings while introduction of a receptive female reduced aggressive contacts and augmented sexual behaviour in pairs independently of mating. Considerable variations in testosterone and oestradiol but not cortisol plasma levels were observed between different stages of sexual activity. At the beginning of the reproductive season, silver fox males responded to anoestrus females with significant increase in their blood levels of testosterone and oestradiol. Contents of these two hormones did not change in males during the reproductive season when they encountered a receptive female. A female did not elicit any cortisol response in a male during different periods of the reproductive cycle. The data obtained suggest that the sexual behaviour in silver fox males can be facilitated by testosterone and oestradiol while aggressive interactions between male and female occur independently of these hormones.

Agonistic Behavior↗

PubMed2007

Associations among body condition score, body weight, and reproductive performance in seasonal-calving dairy cattle.

The objective of the present study was to identify and quantify relationships between body condition score (BCS) and body weight (BW) in dairy cows with reproduction variables in pasture-based, seasonal-calving dairy herds. Over 2,500 lactation records from 897 spring-calving Holstein-Friesian dairy cows were used in the analyses. Eleven BCS- and 11 BW-related variables were generated, including observations at calving, nadir, planned start of mating (PSM), and first service, as well as days to nadir and the amount and rate of change between periods. The binary reproductive variables were cycling by PSM, mated in the first 21 d from PSM, pregnant to first service, and pregnant in the first 21, 42, and 84 d of the seasonal mating period. Generalized estimating equations were used to identify BCS and BW variables that significantly affected the probability of a successful reproductive outcome. After adjusting for the fixed effect of year of calving, parity (for cycling by PSM only), and the interval from calving to either first service or PSM, reproductive performance was found to be significantly affected by BW or BCS at key points, and by BCS and BW change during lactation. All reproductive response measures were negatively affected when BCS and BW measures indicated an increased severity and duration of the postpartum negative energy balance. In particular, cycling by PSM was positively associated with calving BCS, whereas pregnancy at 21, 42, and 84 d post-PSM were positively associated with nadir BCS and BW gain post-PSM, and negatively associated with BCS loss between calving and nadir. The results highlight the important role that BCS and BW loss has on reproductive performance, especially in seasonal-calving dairy systems because of the short period between calving and PSM.

Animals↗

PubMed1989

Serum 11-ketotestosterone and testosterone concentrations associated with reproduction in male bluegill (Lepomis macrochirus: Centrarchidae).

Male bluegill (Lepomis macrochirus) display a complex reproductive behavior involving two alternative life history pathways: delay of sexual maturation to become "parentals" or precocious maturation as "cuckolders." The purpose of our study was to investigate the association of two androgens, 11-ketotestosterone (11KT) and testosterone (T), with reproduction in these two types of males. Radioimmunoassay techniques were used to measure daily levels of the two androgens in the blood serum of parental male bluegill captured during the prespawning, spawning, and nesting periods throughout the reproductive season. Dramatic changes in the levels of 11KT and T were observed among parental males during these periods. Peaks occurred at the onset of spawning activity during each breeding bout. Compared to spawning parental males, spawning cuckolder males had significantly lower serum levels of 11KT. In contrast, the serum levels of T among parental and cuckolder males were not significantly different. These findings suggest that the elevated levels of 11KT are associated with the behaviors displayed by spawning parental males. The levels of T, however, seem to be associated with the occurrence of a phenomenon common to both parental and cuckolder males, such as development of gonads and/or spermiation.

Animals↗

PubMed1990

[Reproductive and developmental toxicity study of mofezolac (N-22) (1)--Study by oral administration of N-22 prior to and early stages of pregnancy in rats].

Mofezolac (N-22), a newly developed analgesic and anti-inflammatory agent, at dose levels of 0, 10, 30 and 90 mg/kg/day were administered orally to males from pre-mating to mating period and to females from pre-mating to early gestation period. Effects on reproductive performance of both sexes, especially reproductive capability, and development of offspring were examined. 1. In male parents, no changes in body weight and food consumption were found in all male groups, but the increase in gastric mucosal lesions such as ulcers were observed in 30 and 90 mg/kg/day groups. 2. In female parents, the decrease in body weight and food consumption of 90 mg/kg/day group during early gestation period were found, but at necropsy no changes were shown in all female groups. 3. Reproductive capability, mating and pregnancy performance were not affected. 4. No effects of N-22 on fetuses were observed. 5. The suggestions were as follows: No effect dose levels (NOELs) for male and female general-toxicologically were 10 and 30 mg/kg/day, respectively. NOELs for reproductive capability and for fetal development were 90 mg/kg/day.

Administration, Oral↗

PubMed1992

Immunohistochemical demonstration of the presence and localization of diverse molecular forms of gonadotropin-releasing hormone in the lizard (Podarcis s. sicula) brain.

The immunohistochemical presence and the distribution pattern of four different molecular forms of gonadotropin-releasing hormone (GnRH) were investigated in the brain of both sexes of the lizard, Podarcis s. sicula. Animals used in this study were collected in November and April, representing two different periods of the reproductive cycle. The antisera used were those raised against synthetic mammalian GnRH, chicken GnRH-I and II, and salmon GnRH. Strong immunoreaction was obtained for salmon, chicken-I, and chicken-II GnRHs, whereas a very weak reaction was seen for the mammalian form of GnRH. The distribution of immunoreactive-GnRH perikarya and fibers did not vary with the sex, the reproductive condition of the animals, or the antiserum used. Also, the intensity of immunoreaction with any one antiserum was quite similar in both periods of the year and in all brains examined. The immunoreactive perikarya was seen as two distinct groups, one in the mesencephalon and the other in the infundibulum. Immunoreactive fiber endings were seen in the telencephalon, the optic tectum, the anterior preoptic area, the median eminence, the central grey matter, the rhombencephalon, and the cerebellum. No immunoreactive perikarya were seen in the telencephalon or the anterior preoptic area.

Animals↗

PubMed1997

Production of an oxytocin like substance by the subcommissural organ (SCO), related to the reproductive cycle in oviparous and viviparous reptiles.

The subcommissural organ (SCO) is a circumventricular organ of glial origin typical of all vertebrates. The SCO releases its secretion into the third ventricle to constitute Reissner's fibre (RF). Reportedly, in reptiles, SCO has cyclic secretory activity related to the reproductive cycle. In this immunocytochemical study we show that, in females of oviparous reptiles (Lacertidae: Podarcis sicula) and in a viviparous species (Scincidae: Chalcides chalcides), SCO secretion consists of hormones, in part of the oxytocin-like (OXY-like) type. The amount of OXY-like material in the cells and in the third ventricle varies according to the different stages of the reproductive cycle. In the oviparous species, OXY-like hormone secretion can be induced by FSH administration at 28 degrees C, in the period of winter reproductive stasis as well. In the viviparous skink, showing an annual single ovulatory cycle, OXY-like secretion is present in the basal region of the cells, and is released into the third ventricle only at delivery. The role of an OXY-like hormone in the SCO is here discussed in relation to the different stages of the reproductive cycle. Its influence on the hypothalamus-hypophysis-gonad axis and its role in the transport of eggs into the ducts in the oviparous species, and at delivery in the viviparous one, are also suggested.

Animals↗

PubMed2005

Immunohistochemical localization of gastrin-releasing peptide, neuronal nitric oxide synthase and neurone-specific enolase in the uterus of the North American opossum, Didelphis virginiana.

The present study has demonstrated the immunohistochemical localization of gastrin-releasing peptide (GRP), neuronal nitric oxide synthase (nNOS) and neurone-specific enolase (NSE) in the uterus of the North American opossum. Although the presence of GRP, nNOS and NSE has been reported recently in the uterus of eutherian species this is the first description of these peptides in a metatherian species. Metatherian mammals are of interest because in these species it is the prolonged lactation phase of development that is the period of primary reproductive investment rather than intrauterine development as is true of eutherian mammals. The opossum, like other marsupial species, has a very abbreviated gestation period which in Didelphis lasts only 12.5 days. GRP was localized in the cytoplasm of cells forming the surface lining epithelium and the glandular epithelium of the opossum endometrium late in pregnancy, at 11.5 days of gestation. Likewise, immunoreactivities of nNOS and NSE were found primarily within the epithelial cells of the endometrium at 11.5 days of gestation. As these peptides and enzymes appear primarily at the time of establishment of the yolk sac placenta (between day 10 and day 12.5 gestation), the present results strongly suggest that these factors may play a fundamental role in the placentation of the opossum.

Animals↗

PubMed1995

Effect of restricted feeding during the rearing period and a "forced moult" at 40 weeks of production on the productivity of Pekin breeder ducks.

1. Six males and 24 female Cherry Valley Pekin ducklings were randomly allocated to each of 12 pens to test the effects of quantitative food restriction during the rearing period on the subsequent reproductive performance. At the end of the laying period (60 weeks) a "forced moult" was introduced and its effect on a further 40 weeks production investigated. 2. The 3 rearing treatments were 50% of ad libitum intake from 3 to 20 weeks; 75% of ad libitum intake from 3 to 20 weeks and ad libitum intake throughout. During the laying period (20-60 weeks) and post forced-moult period (60-100 weeks) duck breeder pellets were fed ad libitum to all groups. 3. Highly significant (P < or = 0.01) differences in favour of the restricted groups over the ad libitum-fed groups were observed in most of the responses studied. The following were the main advantages of food restriction: lower lifetime food intake, lower carcase fat content at 20 weeks, delay in sexual maturity, higher egg production, higher peak and terminal production, higher fertility, higher hatchability of eggs set and lower mortality. Egg mass and hatchability of fertile eggs was not influenced by food restriction in this experiment. The use of a "forced moult" showed that it could be of economical importance. 4. Difference between treatments in respect of absolute and relative visceral masses were also investigated. The absolute masses of the intestine, heart, gizzard and liver all decreased as the degree of food restriction increased. The relative visceral masses showed the opposite trend with the exception of the heart which showed no significant differences between treatments.

Aging↗

PubMed2005

Adaptations of the raccoon dog (Nyctereutes procyonoides) to wintering--effects of restricted feeding or periodic fasting on lipids, sex steroids and reproduction.

The raccoon dog (Nyctereutes procyonoides) is an omnivorous canid with autumnal hyperphagia and fattening followed by mid-winter passivity and fasting in boreal latitudes with seasonal snow cover. The effects of two different feeding levels (400 or 200 kcal/animal/d) or fasting (5-week fasting+1-week feeding+3-week fasting) on plasma lipids, sex steroids and reproductive success of farm-bred raccoon dogs (n=60 females and 24 males) were studied in winter. The body masses, body mass indices (BMIs) and levels of plasma triacylglycerols (TG), total cholesterol and low- and high-density lipoprotein cholesterol did not differ between the fed and the restrictively fed animals. During fasting, the plasma TG concentrations increased and the BMIs decreased, indicating the release of fatty acids from adipose tissue. After the fasting periods, the levels of plasma cholesterol and high-density lipoprotein cholesterol increased, whereas the TG levels decreased indicating the rebuilding of energy reserves. The fact that the different wintertime feeding regimes had no impact on the plasma glucose, total protein, cortisol, estradiol, progesterone or testosterone levels, or on the reproductive success, indicates versatile adaptive capacity in the species.

Adaptation, Physiological↗

PubMed1996

Resumption of ovarian activity in zebu cows (Bos indicus) in the humid tropics: influence of body condition and levels of certain blood components related to nutrition.

This study investigated the relationship between resumption of ovarian activity and body condition in a herd of 20 zebu cows in the humid tropics. Blood chemistry profiles to monitor nutritional status were also evaluated. Plasma progesterone was used to determine ovarian activity. During the study, which lasted 18 weeks post partum, 7 of the animals resumed ovarian activity while 13 remained in the anoestrous stage. The beginning of the first luteal phase was registered on day 87 +/- 19 (range 60 to 106). The animals which resumed cyclicity were in significantly better body condition and had significantly higher mean body weight than anoestrous cows. In the group which resumed ovarian activity, calcium levels decreased significantly from 3 weeks before until the first rise of progesterone in the first normal cycle. The study was divided into 2 periods corresponding to weeks 0 to 8 (I) and 9 to 18 (II) based on the finding that until week 8 all animals were reproductively inactive. During period I there were no significant differences between the groups in blood concentrations of albumin, glucose, urea, cholesterol, calcium and phosphorus. During period II albumin was significantly higher and urea significantly lower in the cows resuming ovarian activity. The results suggest that cows able to maintain their body condition from calving through the early post-partum period will have shorter intervals to first post-partum oestrus than cows which have lost body weight. The lower urea and higher albumin levels in the cyclic animals probably reflected a better feed efficiency--the demands of lactation were compensated by an altered nitrogen metabolism.

Animals↗