Month Of Parturition Research Articles

Effect of pre- and postpartum supplementation of a pure glycerol product to dairy cows on feed intake, metabolic markers, and milk yield and components

The objective of this study was to quantify the effects of supplementing transition dairy cows with a low inclusion dry glycerol product in the pre- and postpartum periods on feed intake, metabolic markers, and milk yield and components. Multiparous Holstein dairy cows (n = 60) were enrolled in a 2-by-2 factorial design study. Starting 21 d before expected parturition, cows individually received a dry cow diet with (1) 250 g/d glycerol product supplementation [66% pure glycerol (United States Pharmacopeia grade); GLY], or (2) no supplementation (CON) mixed to their total mixed ration. After parturition, cows, again, were individually assigned to either GLY, or (2) no supplementation (CON) to their partial mixed ration for the first 21 d in milk (DIM). Cows were milked by an automated milking system and offered a target of 5.4 kg DM/d pellet (23% of target total dry matter intake, DMI) in the automated milking system and followed for 42 d into lactation. Blood samples were collected 6.3 ± 3.47 d before calving for all blood measures and 3, 7, 10, and 14 DIM for analysis of glucose and β-hydroxybutyrate, as well as 3 and 7 DIM for nonesterified fatty acids (NEFA) and haptoglobin. Initial dry cow body weight (BW), calf birth weight, previous 305-d milk, and month of parturition were used as covariates in the statistical model. Cows supplemented with GLY prepartum lost less BW and consumed more DMI pre- and postpartum, as well as had lower postpartum blood β-hydroxybutyrate and NEFA concentrations compared with those fed the CON treatment prepartum. Cows supplemented with GLY postpartum had lesser DMI in the first 42 DIM than cows fed CON postpartum, but also had reduced blood NEFA concentrations, odds of a high haptoglobin test, odds of a low blood glucose test, and lesser preformed fatty acid concentrations and yields in their milk. Cows supplemented glycerol both pre- and postpartum lost the least total BW from -21 to 21 DIM. No treatment effects were detected for milk yield; however, cows receiving GLY postpartum had lower milk fat. Overall, glycerol supplementation during the transition period, particularly during the 21 d before calving, was associated with markers of improved metabolic status.

An Upper Palaeolithic Proto-writing System and Phenological Calendar

In at least 400 European caves such as Lascaux, Chauvet and Altamira, Upper PalaeolithicHomo sapiensgroups drew, painted and engraved non-figurative signs from at least ~42,000bpand figurative images (notably animals) from at least 37,000bp. Since their discovery ~150 years ago, the purpose or meaning of European Upper Palaeolithic non-figurative signs has eluded researchers. Despite this, specialists assume that they were notational in some way. Using a database of images spanning the European Upper Palaeolithic, we suggest how three of the most frequently occurring signs—the line<|>, the dot <•>, and the <Y>—functioned as units of communication. We demonstrate that when found in close association with images of animals the line <|> and dot <•> constitute numbers denoting months, and form constituent parts of a local phenological/meteorological calendar beginning in spring and recording time from this point in lunar months. We also demonstrate that the <Y> sign, one of the most frequently occurring signs in Palaeolithic non-figurative art, has the meaning <To Give Birth>. Thepositionof the <Y> within a sequence of marks denotes month of parturition, an ordinal representation of number in contrast to the cardinal representation used in tallies. Our data indicate that the purpose of this system of associating animals with calendar information was to record and convey seasonal behavioural information about specific prey taxa in the geographical regions of concern. We suggest a specific way in which the pairing of numbers with animal subjects constituted a complete unit of meaning—a notational system combined with its subject—that provides us with a specific insight into what one set of notational marks means. It gives us our first specific reading of European Upper Palaeolithic communication, the first known writing in the history ofHomo sapiens.

Reproductive Steroid Hormone Patterns in Baleen of Two Pregnant Humpback Whales (Megaptera novaeangliae).

Case studies of two pregnant humpback whales whose hormones were analyzed in baleen may illuminate when humpback whales ovulate, gestate, and give birth. These physiological metrics could assist in accurate population growth assessments and conservation of the species. This study shows that baleen hormone analysis can be a useful tool for understanding whale reproductive physiology.

Phenotypic Assessment of Probiotic and Bacteriocinogenic Efficacy of Indigenous LAB Strains from Human Breast Milk.

Breast milk is the combination of bioactive compounds and microflora that promote newborn’s proper growth, gut flora, and immunity. Thus, it is always considered the perfect food for newborns. Amongst their bioactives, probiotic communities—especially lactic acid bacteria (LAB)—are characterized from breast milk over the first month of parturition. In this study, seven LAB were characterized phenotypically and genotypically as Levilactobacillus brevis BDUMBT08 (MT673657), L. gastricus BDUMBT09 (MT774596), L. paracasei BDUMBT10 (MT775430), L. brevis BDUMBT11 (MW785062), L. casei BDUMBT12 (MW785063), L. casei BDUMBT13 (MW785178), and Brevibacillus brevis M2403 (MK371781) from human breast milk. Their tolerance to lysozyme, acid, bile, gastric juice, pancreatic juice, and NaCl and potential for mucoadhesion, auto-aggregation, and co-aggregation with pathogens are of great prominence in forecasting their gut colonizing ability. They proved their safety aspects as they were negative for virulence determinants such as hemolysis and biofilm production. Antibiogram of LAB showed their sensitivity to more than 90% of the antibiotics tested. Amongst seven LAB, three isolates (L. brevis BDUMBT08 and BDUMBT11, and L. gatricus BDUMBT09) proved their bacteriocin producing propensity. Although the seven LAB isolates differed in their behavior, their substantial probiotic properties with safety could be taken as promising probiotics for further studies to prove their in vivo effects, such as health benefits, in humans.

Long term monitoring of the reproductive behavior of wild Chinese pangolin (Manis pentadactyla)

Observations of Chinese pangolin (Manis pentadactyla) in the wild are extremely rare and challenging because of their nocturnal and cryptic activity patterns and low population density. The present article reported the first field observation in eastern Taiwan, from October 4, 2012 to June 16, 2016, on the reproductive behavior of the Chinese pangolin based on the monitoring of a female (LF28) using radiotelemetry and camera traps. During this period, LF28 aged from 1–4.5 years old and gave two single-births, both took place in early December, at 3 and 4 years old, respectively. We recorded the entire 157 days of the first nursing period from parturition to maternal separation. For the second infant, the gestation period was estimated to be around 150 days based on the evidence that the pregnancy started in early Jul. 2015 and the offspring was born on Dec. 9, 2015. During the entire nursing period, LF28 frequently moved the offspring from one nursing burrow to another staying various durations ranging from 1 day to more than 35 days, and almost all (= 15/16) of these burrows were located in the core (MCP75) of LF28’s home range. Started from the month of parturition and lasting throughout the whole nursing period, different adult males constantly visiting the nursing burrows were recorded. Mating behavior was recorded once outside the burrow in March, which provided evidence of the occurrence of post-partum estrus in this species. Delayed implantation was proposed based on the observation of a several months lag between copulation and the estimated pregnancy initiation date. The present study demonstrated the advantage of using remote technologies to learn the life history of resting fossorial species.

Effect of lactation length and litter size on milk composition of Boer goat within one month of parturition

Effect of lactation length and litter size on milk composition of Boer goat within one month of parturition

Ecological drivers of female lion (Panthera leo) reproduction in the Kruger National Park.

The role of social cues in the reproduction of social mammals, particularly carnivores, has been thoroughly studied and documented in literature. However, environmental cues such as resources of water, food, and shelter have been identified to a lesser extent. Pregnant lions (Panthera leo) are notoriously secretive during the final stages of pregnancy and postpartum. Behavioral indicators depicted by movement patterns obtained by remote detection of collared female lions in the Kruger National Park were necessary for the monitoring of birth timing. Over the study period, eight plus a potential three parturition incidences of collared females were recorded. Of the variables measured (step length, range size, duration, prey biomass, and rainfall), range size during the month of parturition was the most indicative movement pattern of a successful birth. By backdating the potential birth month of the litters, date of conception was calculated and our results revealed a correlation between the birthing peaks of preferred prey during the month of conception. Birth timing in conjunction with remote sensing and ecological factors were thus identified behaviors associated with denning.

Pregnancy and parturition in dromedary camels I. Factors affecting gestation length, calf birth weight and timing of delivery

In the present study, we evaluated the role of genetic, physiologic and environmental factors in affecting gestation length, calf birth weight and time of parturition in dromedary camels. Reproductive data were collected over a 10-year period at the world's first intensively managed, large-scale camel dairy farm. We hypothesized that environmental conditions (i.e. photoperiod) have a decisive effect on these reproductive parameters. The effect of various factors was tested with linear mixed models and variance component analysis. A total of 557 (13.1%) primiparous and 3691 (86.9%) multiparous parturitions were observed in 2,123 dromedaries. Parturitions had a pronounced seasonal distribution. The mean (±SE) length of gestation and mean (±SE) birth weight were 384.5 ± 0.17 days (n = 4,093, CV = 2.88%) and 34.5 ± 0.09 kg (n = 3,909, CV = 16.8%), respectively. All but one fixed factors (type of breeding) affected length of gestation and calf birth weight. Month of conception (27.1%), female camel (11.2%) and live-dead status of the calf (10.6%) were responsible for close to 50% of the variation in gestation length. At the same time, female camel (30.3%), parity (11.3%), year (6.9%) and month of parturition (6.2%) had the strongest relative influence on the variation in calf birth weight. Both reproductive traits showed a pronounced circannual variation. Mean length of gestation was longer by app. 18 days in dromedaries conceiving in November compared to those becoming pregnant in May. Average new-born weight was 4.4–4.9 kg higher in December compared to that in September and April. Dromedaries gave birth throughout the 24 h period, but most of the deliveries (n = 3,117, 74.1%) occurred from sunrise to sunset. The peak of deliveries was between 2 and 3 pm. Month of the year has a strong effect on the timing of deliveries. In contrast, the time from sunrise to parturition did not differ among the months. Peak of deliveries occurred 7–9 h after sunrise and the median of time from sunrise to parturition was 8 h and 24 min. These results give strong support to the original hypothesis. Seasonal changes were independent of nutritional factors, were associated with climatic conditions (i.e. photoperiod) and may reflect an endogenous circannual rhythm in foetal development. The dromedary camel could be a useful in vivo model to study the effect of the environment on feto-maternal communication, fetal development and timing of parturition.

The effects of breed, month of parturition and sex of progeny on beef cow fertility using calving interval as a measure

This study aimed to evaluate levels of beef cow fertility using calving interval (CI; measured in days) as a measure, and investigate the effects of breed, season, year and progeny gender on CI. The CI data included 273 764 records collected between 1997 and 2012 and included the seven most common breeds (and their crosses) in Northern Ireland (Charolais, Limousin, Belgian Blue, Simmental, Blonde d’Aquitaine, Aberdeen Angus and Hereford), accounting for 94.1% of beef dams recorded. Mean CI for all cows was 395 days, 30 days longer than the optimum 365 days. Charolais and Belgian Blue dams had the longest CI (P<0.05). Cows older than 144 months had a longer CI (P<0.05) compared with cows younger than 144 months. Charolais sires had a shorter subsequent CI of 392 days (P<0.05) compared with the other breeds. Cows calving in June had the shortest subsequent CI (376 days;P<0.05), whereas cows calving in November had the longest subsequent CI (410 days). Progeny gender did not significantly affect CI. This study establishes the level of beef cow fertility using CI as a measure in Northern Ireland is sub optimal and there are opportunities for improvement. Factors identified as influencing CI included dam breed, sire breed and month of parturition. This knowledge can be used to direct breeding programmes and inform knowledge transfer protocol to improve sustainability of beef production.

Factors affecting pregnancy length and phases of parturition in Martina Franca jennies

The knowledge of normal pregnancy length, duration of parturition stages, and neonatal early adaptation is mandatory for a rationale management of birth, especially in monotocous species with long gestations. This study reports data obtained from a large number of Martina Franca jennies with normal healthy pregnancies and spontaneous eutocic delivery of a mature, healthy, and viable donkey foal. Pregnancy lasts, on average, 371 days, and only the fetal gender significantly determines pregnancy length, with longer gestations observed in jennies bearing male fetuses. Other factors such as the year of foaling, month of ovulation, month of parturition, birth weight of the foal, and age of the jenny did not influence pregnancy length. The first stage of foaling lasted on average 65 minutes, the second stage 19 minutes, and the third stage 58 minutes. The umbilical cord ruptured on average within 16 minutes after birth; the foal stood up in 61 minutes and suckled the colostrum for the first time within 10 minutes after birth and again after 143 minutes of birth; meconium passage occurred, on average, 86 minutes after birth. Although times reported for the process of foaling are similar to data reported for the horse, the times for early neonatal donkey foal adaptation are longer as compared to the horse foal.

Variations in protein and fat contents and their fractions in milk from two species fed different forages

This study aimed at determining the variations in milk constituents which could be varied by feed and animal species. To achieve this goal, two groups of homoparity Baladi cows and Egyptian buffaloes (n = 20 per species) were used. Each group was divided into two subgroups (n = 10): subgroup I received legume forage (Egyptian clover) and subgroup II received grass forage (sorghum forage). All experimental animals were fed the diet consisting of concentrate, forage and rice straw as 50, 25 and 25% of dry matter intake respectively. Milk samples were taken for analysis. The trial lasted until the 3rd month of parturition. The main results indicated that lactating cattle fed legume forage significantly (p ≤ 0.01) had more content of casein nitrogen (513 mg/100 ml milk), lower content of glutamic acid (23.56 g/100 g milk protein) and more content of cis-9, trans-11 18:2 conjugated linoleic acid (CLA) (0.77 g/100 g milk fat) compared with 433, 26.67 and 0.53, respectively, for cattle fed grass forage. With regard to the species effect, results showed that buffalo milk appeared to contain significantly higher (p ≤ 0.01) contents of casein nitrogen, phenylalanine, glutamic and arachidonic acid compared with cow's milk. However, the latter was significantly (p ≤ 0.01) more in the cis-9, trans-11CLA (0.59 g/100 g milk fat) than that in buffalo milk (0.47 g/100 g milk fat). The results revealed that not only forage type played a critical role in determining the variations of milk nitrogen distribution, milk amino acids and fatty acids but also animal species had a significant effect on these parameters.

Effect of season, month of parturition and lactation on estrus behavior and ovarian activity in Barki x Rahmani crossbred ewes under subtropical conditions

The correlations between some meteorological parameters and fertility data were evaluated in Barki x Rahmani crossbred ewes using the records of five consecutive years (2003–2007). Additionally, estrus detection and ultrasonic evaluation were applied on eighteen mature dry ewes during breeding and non-breeding seasons. The effect of lactation was evaluated by monitoring estrus behavior in ninety four lactating ewes from 40 to 120 d after parturition. Moreover, ultrasonography was used to identify ovarian activity in six cyclic and six acyclic non-lactating ewes. Results revealed that relative estrus occurrence and fertile mating were positively correlated (P <0.05) with high temperature and long photoperiod (conditions of summer season), and were negatively correlated (P < 0.01) with rainfall (condition of winter season). During breeding season, estrus rate, serum progesterone concentration, and diameter of largest follicle were significantly (P < 0.05) higher than those observed during the non-breeding season. Furthermore, month of parturition had a significant effect (P < 0.05) on estrus rate of lactating ewes where ewes that lambed in August, September, and October recorded higher estrus rate than those lambed in November and December. However, the lactational strength did not exert any deleterious effect on the reproductive performance of lactating ewes.In conclusion, in Egypt under subtropical conditions, Barki x Rahmani crossbred ewes exerted optimum estrus behavior and fertile mating during summer season. The reduction in estrus activity during lactation was due to the seasonal effect rather than lactational stress.

Monitoring the nutritional and reproductive state of dairy cows through the presence of urea in milk

The effects of farm, parity (PO) and month of parturition on milk production, percentage of fat and protein, somatic cell count (SCC), and milk urea nitrogen (MUN) concentration were assessed on four specialized dairy farms using 120 cows. Also, the effects of MUN on gestation rate (GR) and artificial insemination rate (AIR) in early lactation were studied. The parameters of production and milk quality were similar among farms and were not influenced by the month of parturition. Farm D presented the highest MUN concentration. Concentration of MUN, percentages of fat and protein and SCC were not influenced by PO. Cows with a value of MUN between 10.1 and 13.0 mg/dL had the highest AIR and GR between days 55 and 70 postpartum and after 70 days in milk. These data suggested that MUN concentration was a useful parameter to predict the nutritional and reproductive stages of dairy cows.

SHepatic Triacylglycerols and Plasma Non-esterified Fatty Acids and Albumin Levels in Cross Breed Cows in Ahvaz City of Khuzestan Province of Iran: An Abattoir Study

The aim of the present study was to compare the hepatic triacylglycerols (TAG) and total lipid and plasma Non-Esterified Fatty Acids (NEFA) and albumin in cows in different stages of productivity slaughtered at Ahvaz abattoir. So, a total of 203 blood and liver samples were collected from the indigenous hybrid cows immediately after being slaughtered at the abattoir. The cows were divided into 4 groups according to their pregnancy statuses: 1-8 months pregnant, 8-9 months pregnant, less and more than 1 month of parturition. Percentage of TAG and Total Lipids (TL) were measured in the liver and NEFA and albumin were measured in the blood circulation. All the liver samples in this study showed some degrees of fatty infiltration. The accumulation of fat in the liver rose significantly (p < 0.001) during the first month after parturition and returned to the same level of pregnancy after one month. We also noticed that plasma NEFA concentration was significantly higher (p < 0.05) during the first month of parturition and serum albumin level relegated to its lowest level (p < 0.05) in the last month of pregnancy. These results reveal that fatty liver is quite common in all the animals in the region especially in their early lactation. These findings indicate the necessity of reconsideration in the animal's food policies in the area and some especial approaches during the early phase of lactation.

INFLUÊNCIA DOS FATORES AMBIENTAIS SOBRE O TAMANHO DA LEITEGADA AO NASCER E TAXA DE MORTALIDADE À DESMAMA DE LEITÕES NO BREJO PARAIBANO

This experiment was carried out to evaluate the influence of the environmental and genetic factors on the litter size and mortality rate at birth and weaning f pigs in Paraiba, Brazil. The Zootechnical data was collected from farm SUPASA, in the district of Guarabira, state of Paraiba, Brasil. They were analyzed the data of pure swine Landrace and Large White and crossed animals (Landrace x Large White), born in the period from 1995 to 1996. The following characteristics were evaluated number of born pigs per litter (piglets born alive) and the rate of mortality of the pigs at weaning, in relation to the mother’s race, month and year of parturition, and sex of the pigs. After the studies of the collected data significant differences were verified among races for the litter size, it was observed that Landrace andthe crossed showed larger number of pigs per litter than Large White. The year and the month of parturition mad significant effect on the litter size, as well as the mortality rate. KEY WORDS: Breed, genetics parameters, produtive effficiency, reproduccion, swine

Epidemiological and Bacteriological Survey of Buffalo Mastitis in Nepal

A total of 355 Murrah cross buffaloes, consisting of 23 subclinical and 332 clinical mastitis cases brought to the Veterinary Teaching Hospital, Chitwan, Nepal from 2002 to 2005, were analyzed to determine the organisms involved, the seasonal occurrence of mastitis, and antibiotic susceptibility of mastitis pathogens. Coagulase negative Staphylococci (CNS) such as Staphylococcus albus and S. epidermidis were the predominant organisms associated with subclinical cases, and CNS and Coliforms in clinical cases. The maximum number (16%) of clinical cases of mastitis were observed in the month of July, when temperature and humidity are highest. The incidence of clinical mastitis was higher in animals during 1st calving and during the 1st month of parturition. Resistance to antibiotics was determined for 55, 23 and 149 isolates of Staphylococcus spp., Streptococcus spp. and Coliforms, respectively. In vitro drug sensitivity testing revealed that enrofloxacin had the highest average sensitivity (91%) for all types of bacteria. The effectiveness of other drugs detected were gentamicin (87%), tetracycline (83%) and chloramphenicol (82%). The antibiogram showed that both gentamicin and enrofloxacin are slowly becoming resistant. Mastitis pathogens have developed resistance to ampicillin and penicillin.

Genetic and environmental effects over milk production of buffalo cows in Brazil

The objective of this paper was to evaluate the relevance of environmental and genetics effects on milk production of buffalo cows in Brazil. The data were based on the Buffalo Genetic Improvement Program - PROMEBUL, using information of 1,911 cows (107 Jafarabadi, 101 Mediterranean, 1,056 Murrah and 647 crossbred females) with parturition between 1982 and 2003. The mathematic model for evaluating milk production included the fixed effects of herd, parturition year (1982 to 2003) and month (January to December), calf’s sex (male or female), genetic group (Jafarabadi, Mediterranean, Murrah, and crossbreed), number of milking (one or two), lactation order (1 to 12) and duration of lactation (as a linear effect). The mean milk production in herds was 1,590.36 ± 609.25 kg. All sources of variation were significant (P<0.05) for the studied characteristics, except calf’s sex. The mean milk production per genetic group was 1,651.4; 1,592.2; 1,578.3 and 1,135.5 kg, for Murrah, Mediterranean, Crossbred and Jafarabadi, respectively. The duration of lactation was the most important source of variation over milk production, followed by the year of parturition, herd, parturition order, genetic group and month of parturition.

STUDY OF SOME NON-GENETIC FACTORS AFEECTING GESTATION PERIOD AND BIRTH WEIGHT IN HAMMDANI EWES

The experiment has been conducted on 58 Hammdani ewes 2-5 years old at the sheep farm/ Girdarasha/College of Agric. – Univ. of Salahaddin during 2003-2004.The average length of gestation period and birth weight were 151.290 days and 5.025 kg respectively. Weight of the ewes at mating, and birth weight had significant effect (p≤0.05) on gestation period; ewes weight 80-89kg had shorter gestation periods 150.133 days, and ewes carried lambs weight at birth (≥5.6 kg) had longer gestation periods 152.304 days) .Age of ewes at mating, sex of lambs, Type of birth and month of parturition did not show significant effects on length of gestation period in Hammdani sheep . Type of birth, age and weight of Dams at mating were significant effect birth weight, single and twins lambs weight at birth were 5.289 and 4.459 kg respectively. Lambs born from ewes 3 and 4 years age largest than lambs born from ewes 2 years age. Sex of lamb and month of birth did not show significant effects on birth weight in Hammdani sheep.

Life history plasticity and population regulation in sea otters

We contrasted body condition, and age‐specific reproduction and mortality between a growing population of sea otters (Enhydralutris) at Kodiak Island and a high‐density near‐equilibrium population at Amchitka Island, Alaska. We obtained data from marked individuals, population surveys, and collections of beach‐cast carcasses. Mass:length ratios indicated that females (but not males) captured in 1992 at Amchitka were in poorer condition than those captured at Kodiak in 1986–1987. In 1993, the condition of females at Amchitka improved in apparent response to two factors: (1) an episodic influx of Pacific smooth lumpsuckers, Aptocyclus ventricocus, from the epi‐pelagic zone, which otters consumed; and (2) an increase in the otters’ benthic invertebrate prey resulting from declining otter numbers. Reproductive rates varied with age (0.37 [CI=0.21 to 0.53] births female−1 yr−1 for 2–3‐yr‐olds, and 0.83 [CI=0.69 to 0.90] for females ≥4 yr old), and were similar at both areas. Weaning success (pups surviving to ≥120 d), in contrast, was almost 50% lower at Amchitka than at Kodiak and for females ≥4 yr of age was 0.52 (CI=0.38 to 0.66) vs 0.94 (CI=0.75 to 0.99), respectively. Sixty‐two percent of the preweaning pup losses at Amchitka occurred within a month of parturition and 79% within two months. Postweaning survival was also low at Amchitka as only 18% of instrumented pups were known to be alive one year after mother‐pup separation. Adult survival rates appeared similar at Amchitka and Kodiak. Factors affecting survival early in life thus are a primary demographic mechanism of population regulation in sea otters. By maintaining uniformly high reproductive rates over time and limiting investment in any particular reproductive event, sea otters can take advantage of unpredictable environmental changes favorable to pup survival. This strategy is consistent with predictions of “bet‐hedging” life history models.

Length of postpartum anestrus in goats in subtropical Mexico: Effect of season of parturition and duration of nursing

The aim of this study was to determine whether season of birth and length of nursing affected the duration of postpartum anestrus in Creole female goats maintained on a constant plane of nutrition in subtropical Mexico. Three experiments were conducted in the Laguna region in the State of Coahuila, Mexico (26°N). In the first experiment, 34 goats gave birth in January; in the second, 31 females gave birth in May; and in the third, 22 goats kidded in October. At parturition, females were allocated to 1 of 3 groups based on body weight and date of parturition: kids were weaned at 2, 30 or 90 d according to their group. After weaning, females were milked manually once a day until the end of the study. All animals were kept in a shed and were fed alfalfa ad libitum and given 200 g of concentrate daily. Starting 1 wk after parturition, estrous behavior was detected twice daily using an apron-bearing male, and blood samples were obtained twice weekly to determine ovarian activity from the plasma progesterone levels. A strong effect of month of parturition was found on the duration of postpartum anestrus (P<0.0001), which was longer in females kidding in January (about 200 d) than in those kidding in May (about 100 d) or October (about 50 d). A tendency for an interaction between season of parturition and length of nursing was observed in the length of anovulation (P<0.07): for parturition in October, anestrus was longer when kids were weaned after 90 d than after 2 or 30 d (P<0.01). Season of parturition also affected dates of reinitiation of ovulatory and estrous activity (P<0.001). Proportions of normal, short and long cycles and of associations between estrous and ovulations were not influenced by season of parturition or the age of weaning. These data demonstrate that in subtropical latitudes, season of parturition can dramatically influence the duration of postpartum anestrus independently of the availability of food.