Tropical Sheep Research Articles

EQUATIONS FOR BODY WEIGHT ADJUSTMENTS IN BLACK BELLY EWE LAMBS

<p><strong>Background. </strong>As body weight (BW) is rarely determined on fasted animals in most production systems, the need to develop accurate mathematical models for adjusting BW has been identified. <strong>Objective.</strong> To evaluate models for estimating shrunk body weight (SBW) and empty body weight (EBW) in Black Belly growing ewe lambs raised in tropical conditions. <strong>Methodology.</strong> Data of sixty Black Belly ewe lambs, between four to eight months of age with a mean BW of 26.55± 3.92 kg (± SD) were used. The SBW was estimated based on the BW without fasting (fed) and the EBW based on SBW through three models: 1. Linear; 2.-Linear without intercept and 3.- Exponential. The predictive capacity of the models was evaluated by cross-validation. <strong>Results. </strong>The correlation coefficients between BW and SBW and SB and EBW were high (r = 0.94; <0.0001). The coefficients of determination (r<sup>2</sup>) for the equations between BW and SBW were 0.89 (P<0.001); and 0.86 (P<0.001) for the relationship between SBW and EBW. Based on the AIC (26.81) Eq. 2 described the relationship between BW and SBW better than Eq. 1, (AIC = 28.44) and Eq. 3 (AIC =28.35). The final model to estimate SBW as a function of BW was: SBW (kg): 0.96 (±0.001***) × BW. With respect to the SBW and EBW ratio, Equation 5, was better than the linear Eq. 4, (AIC = 33.01) and Eq. 6 (AIC = 33.35). The following model was: EBW (kg): 0.81 (± 0.06***) × SBW. The cross-validation of the equation of the relationship between BW and SBW showed that Eq. 1 had a higher r2 (0.87), and lower RMSEP and MAE than Eq. 2 and Eq. 3. Also, the equation of the relationship between SBW and EBW the cross-validation revealed that Eqs. 4 and 6 had the higher <sup>r2</sup> (0.82), and lower RMSEP and MAE and tended to be more accurate than Eq. 5. <strong>Implications. </strong>The results obtained in present study contributes to the development of mathematical models for more accurate body weight adjustments in tropical sheep. <strong>Conclusion. </strong>The equations developed and evaluated in the present study revealed that the linear relationship between BW and SBW, and the linear and exponential relationship between SBW and EBW can be used to body weight adjustments in growing Black Belly ewe lambs. It's worth noting that this confirms that the SBW can be calculated using an adjustment factor of 0.96 FBW.</p>

Continental vs. tropical breed: Immunity comparison under heat stress conditions utilizing qRT-PCR technique

Understanding the responses of animals to seasonal heat stress on the genomic level has led to the identification of genes implicated in thermal stress reaction mechanisms. In this study, the relative gene expression of Interleukin-10 (IL-10), an anti-inflammatory cytokine and biomarker for heat stress-mediated immune modulation, was observed during the summer and winter seasons in continental and tropical sheep breeds, namely, Hungarian Indigenous Tsigai and White Dorper, employing quantitative real-time polymerase chain reaction (qRT-PCR). Temperature-humidity indices (THI) were calculated to assess heat stress levels. The results indicate that IL-10 CT-values were significantly higher during the summer, when heat stress prevails, in both sheep breeds compared to winter. While the White Dorper exhibited a higher numerical value for the summer relative gene expression ratio (16.2) compared to the Hungarian Indigenous Tsigai (12.3), no significant differences in CT values were observed between breeds or among sexes. These findings suggest the immune-adaptive characteristics of the two sheep breeds during seasonal heat stress. The variation of IL-10 gene expression levels between the two breeds can be attributed to their geographical origins; the White Dorper emerging from arid subtropical South Africa and the Hungarian Indigenous Tsigai Sheep thriving in the seasonally harsh Carpathian climate for centuries.

Parámetros reproductivos y de fertilidad de ovejas en el trópico alto de Colombia

Two studies were conducted on sheep in the high tropics of Colombia to study reproductive and fertility parameters associated with animal growth in this ecological zone. In the first trial, 1,389 records were used to analyze, through descriptive statistics, the fertility parameters, the birth rate, and the yield per multiple births of three genetic groups of sheep: the native Criolla and Manchada Paramuna breeds, and they were compared with the imported race Blackface. In the second study, the duration of the estrous cycle was determined and serum progesterone values were determined during the estrous cycle in 19 Criolla x Romney Marsh crossbred ewes, in this experiment, five moments of the cycle were analyzed. The fertility rates found in the Criolla and Manchada Paramuna breeds were 73.1 and 72 %, respectively, and were higher than those of the Blackface sheep (65 %). Blackface ewes showed the highest incidence of multiple births (29 %) and Manchada Paramuna ewes had the highest birth rates (93.7 %). Criolla x Romney Marsh crossbred ewes recorded a mean duration of the estrous cycle of 17.8 d. The highest progesterone secretion (11.5 nmol/L) occurred on day 9 of the estrous cycle, while in the estrus phases, its value was 0.32 nmol/L. This study contributes to the knowledge of the reproductive aspects of Colombian native sheep

Genomic selection signatures in Brazilian sheep breeds reared in a tropical environment

The molecular and genetic effects of heat stress are not as well understood as physiological effects. Heat Stress response should be considered one component of gene network coordinated across various cells, tissues and systems. Its action seeks to minimize the effects of the environment on cellular functions. The detection of selection signatures can identify genes and mutations associated with phenotypic traits even if they are no longer segregating within the populations of interest. This paper looked at 48 sheep breeds (1988 animals), of which 649 animals are from 6 Brazilian breeds reared in a tropical environment. These animals were genotyped using the 50 K SNP Chip. We applied different detection methods (HapFLK and PCAdapt) to identify genomic regions with selection signals (selection signatures). Three groups of breeds were defined, and the first component showed a clear separation between Hair_Warm and Wool_Cold groups. The second component showed some divergence between Wool_Cold and Wool_Warm, with some Hair_Warm breeds located together with Wool_Warm. Hair Brazilian breeds were separated from the others in the first breed component, while the second component segregated European breeds from African and Asian breeds. The four genomic regions identified in chromosomes 2, 7, 11 and 16 harbor several genes related to a wide range of functions. These include production traits (such as milk, growth and reproduction), metabolism (fat and energy), stress response (including immune and inflammation), as well as cell cycle functions. These genomic regions can be a starting point for identifying gene mutations and selecting adapted animals, mainly in a climate change scenario. The locally adapted tropical sheep breeds can be an important genetic reservoir of these thermotolerance genes.

Feeding by Logistic Feed (Mash, Silage, Pellet and Wafer) Compared with Conventional Feed on Physiological, Blood Biochemical and Body Weight Gain Recovery in Tropical Sheep Pasca Transportation

Feeding by Logistic Feed (Mash, Silage, Pellet and Wafer) Compared with Conventional Feed on Physiological, Blood Biochemical and Body Weight Gain Recovery in Tropical Sheep Pasca Transportation

Cassava pulp added to fermented total mixed rations increased tropical sheep's nutrient utilization, rumen ecology, and microbial protein synthesis.

The price of animal production will be affected by the significant increase in feed costs. The objective of this research was to investigate the impact of adding waste cassava pulp to fermented total mixed ration (FTMR) on nutrient utilization, rumen ecology, and microbial protein synthesis in tropical sheep. A 3 × 3 replicated Latin square design was used to randomly arrange nine crossbreed lambs (Santa Inês × Dorper) with an initial body weight (BW) of 18.7 ± 1.6 kg (mean ± SD). During a 21-day trial, the animal was offered a random selection of concentrate diets and rice straw (control), total mixed ration (TMR), or FTMR. During the investigation, data on nutrition utilization, rumen ecology, and microbial protein synthesis were analyzed using analysis of variance. The finding shows that FTMR had significantly higher dry matter (DM) intake and DM intake per BW than either TMR or control (p < 0.05). Lamb fed on FTMR had significantly higher DM, organic matter protein, crude protein, and neutral detergent fiber digestion than those on control or TMR (p < 0.05). Rumen pH values for all treatments ranged from 6.68 to 6.73, with no significant differences. Growing lambs fed FTMR had greater rumen total volatile fatty acid and propionic acid concentrations than those given TMR and the control (p < 0.05). Protozoa were not different across the FTMR groups, although total bacterial and fungal zoospores were increased. In addition, when lambs were fed FTMR containing cassava pulp, ruminal microbial protein synthesis was significantly increased. It could indicate that feeding growing lambs with FTMR could improve nutrient utilization, ruminal fermentation, and microbial protein synthesis. However, studies on the effects of FTMR on sheep performance, meat quality, and milk quality are necessary.

Feeding value of sorghum stover fed to tropical hair sheep as complete rations in chop, mash, pellet, and block forms.

Background and Aim:Poor palatability, low bulk density, and low nutritive value restrict the utilization of the crop residues as animal feeds. Altering the physical characteristics of feed by blending the roughage and concentrates in the form of complete feed improves the nutrient use efficiency and reduces the feed wastage, feed cost, and labor cost. The study aims to determine suitable processing methods (mash, pellet, or block forms) for efficient utilization of sorghum stover-based complete rations vis-a-vis conventional feeding methods in sheep.Materials and Methods:The sorghum stover was incorporated in complete rations with roughage to concentrate ratio of 50:50 proportion in a growth trial of 120 days. The feed ingredients were chaffed, ground in a hammer mill, passed through expander-extruder, and compressed by feed block machine to prepare chop, mash, pellet, and block form of rations, respectively. Twenty-four male intact growing Nellore×Deccani cross lambs (3.5±0.5 months age, 14.50±0.41 kg (mean ± SD) at the start of the experiment) were divided into four experimental groups of six animals each in a complete randomized design. The experimental rations were randomly allotted to each group and evaluated for their intake, nutrient utilization, and growth performance.Results:The sheep fed on pellet-based ration consumed a higher (p<0.05) quantity of dry matter. The digestibility coefficients of organic matter, crude protein, and neutral detergent fiber were higher (p<0.05) in processed rations (mash, pellet, or block). Further, the nitrogen balance (g/d) was higher (p<0.05) in the mash, pellet, and block form of rations, compared to chopped ration. The processing method did not influence calcium or phosphorous balance parameters, except for their urinary losses, which showed an increasing trend (p=0.07). The ram lambs fed with pelleted ration showed higher (p<0.05) weight gain than mash, block, or chaff forms. The efficiency of feed utilization in gaining one kg body weight was higher (p<0.05) in lambs fed a pelleted diet. Feeding pelletized ration was more economical to gain one kg body weight. The bulk density was highest for block-based ration followed by pellet, mash, and conventional rations, and the carrying capacity of truck was highest with the least transport cost in block-form of rations.Conclusion:Physical processing (mash, pellet, and block) of sorghum stover-based complete rations increased the nutrient utilization and growth performance of sheep compared to conventional chopped form. Pelleting the mash with expander-extruder procedure was found to be more profitable. Nevertheless, the cost economics revealed blocks as more preferable forms for transporting the complete rations to larger distances.

Variation in phenotypic resistance to gastrointestinal nematodes in hair sheep in the humid tropics of Mexico.

The objective of the study was to evaluate phenotypic resistance against gastrointestinal nematodes in Blackbelly, Pelibuey and Katahdin ewes before pregnancy in the humid tropics of Mexico. Individual faecal and blood samples were taken in 59 Pelibuey, 69 Blackbelly and 73 Katahdin ewes. The egg count per gram of faeces (EPG) of gastrointestinal nematodes (GINs) was determined. The percentage of packed cell volume (PCV) and body condition score (BCS) of each animal were also recorded. The ewes were segregated as susceptible, intermediate or resistant based on the EPG using the quartile method. The data were analysed using the general linear method, and the means between breeds were compared by Tukey's test. The relationships between the EPG, PCV and BCS were evaluated by Spearman correlation. The Katahdin ewes showed the highest EPG counts (3613.6 ± 5649) compared to the Blackbelly and Pelibuey ewes (576.1 ± 1009 and 56.8 ± 187, respectively, P < 0.01). The PCV values between breeds were similar (P > 0.05). The susceptible ewes had the highest EPG counts and the lowest PCV percentage (5069 ± 6404 and 22.8% ± 8.1% respectively) compared to the resistant ewes (P < 0.01). A higher percentage of Katahdin ewes were susceptible compared to the other breeds (P < 0.05). The main GIN species were Haemonchus contortus, Trichostrongylus colubriformis and Cooperia curticei. In conclusion, Katahdin ewes showed susceptibility to GIN compared to Blackbelly and Pelibuey ewes before the pregnancy period in the humid tropics of Mexico.

MTNR-1A Gene Polymorphism in Two Tropical Sheep breeds of South India

The present study was carried out to evaluate the genetic polymorphism in Ovine MTNR1A of two tropical breeds ie., highly prolific NARI Suwarna sheep and Mandya sheep from southern peninsular region of India with respect to differential fertility. Fifty animals from each breed were randomly selected and subjected to RsaI-RFLP analysis of exon-2 of Ovine MTNR1A. The study revealed monomorphic patterns in all the animals for both the breeds. PCR amplicon of 824 bp fragments with four cut sites at 53 bp, 320 bp, 343 bp and 754 bp, resulted in 411 bp, 267 bp, 70 bp, 53 bp and 23 bp. Only presence of CC genotypes at rs406779174 SNP of Ovine MTNR1A in both the breeds supports non-seasonality in breeding of these animals and no association of SNP with increased fecundity of NARI Suwarna sheep over Mandya sheep.

Prevalence, intensity and population dynamics of hard ticks (Acari: Ixodidae) on sheep in the humid tropics of Mexico.

Hard ticks are a perennial problem in livestock systems throughout Mexico. No data are currently available on tick prevalence, infestation intensity and population dynamics for sheep in the humid tropics of Mexico. Blackbelly sheep (n=30) in Tabasco state, Mexico, were examined every 3weeks for 1year, and all Ixodidae ticks were counted and removed for analysis. Tick species were identified, infestation prevalence and intensity calculated per animal, and infestation per body zone determined. Overall infestation on the studied animals was 51.9%. Four tick species were identified (Amblyomma mixtum, A. imitator, Rhipicephalus microplus and R. annulatus), the most abundant being A. mixtum (94.9%). Prevalence was highest during the northwinds season (61.9%), followed by the dry (48.5%) and rainy (47.3%) seasons; however, the intensity (2.01-2.07 ticks/sheep) did not differ between seasons. Infestation was most frequent in certain zones including the axilla, crotch, udder, abdomen, thorax and rib area. Sheep in the humid tropics of Tabasco, Mexico, are parasitized by four hard tick species and prevalence is highest in the northwinds season. The present data constitute an important baseline for developing sustainable tick control programs for sheep in the humid tropics of Mexico.

216 Genomic regions and pathways associated with resistance to gastrointestinal parasites in tropical sheep breed

216 Genomic regions and pathways associated with resistance to gastrointestinal parasites in tropical sheep breed

Effect of available space and previous contact in the social integration of Saint Croix and Suffolk ewes.

Reproduction in tropical sheep is not affected by season, whereas the reproductive cycle of temperate-climate breeds such as Suffolk depends on the photoperiod. Close contact with tropical ewes during the anestrous period might induce Suffolk ewes to cycle, making the use of artificial light or hormonal treatments unnecessary. However, the integration of both breeds within the social group would be necessary to trigger this effect, and so the aim of the experiment was to determine the speed of integration of 2 groups of Saint Croix and Suffolk ewes into a single flock, according to space allowance and previous experience. For this, 6 groups of 10 ewes (half from each breed) from both breeds, housed at 2 or 4 m/ewe (3 groups/treatment) and with or without previous contact with the other breed, were monitored for 3 d. Each observation day, the behavior, movement, and use of space of ewes were collected during 10 min at 1-h intervals between 0900 and 1400 h. Generalized linear mixed models were used to test the effects of breed, space allowance, and previous experience on behavior, movement, and use of space. Net distances, interbreed farthest neighbor distance, mean interbreed distance, and walking frequencies were greater at 4 m/ewe ( < 0.05). Intrabreed nearest neighbor, mean intrabreed neighbor, and interbreed nearest neighbor distances and minimum convex polygons at 4 m/ewe were greatest for Saint Croix ewes, whereas the opposite was found for lying down ( < 0.05). Experienced ewes showed larger intrabreed nearest neighbor distances, minimum convex polygons, and home range overlapping ( < 0.05). Experienced ewes at 4 m/ewe showed longest total distances and step lengths and greatest movement activity ( < 0.05). Experienced ewes walked longer total distances during Day 1 and 2 ( < 0.05). Lying down frequency was greater for Day 3 than Day 1 ( < 0.05), and Suffolk ewes kept longer interindividual distances during Day 1 ( < 0.05). After 3 d of cohabitation, Suffolk and Saint Croix ewes did not fully integrate into a cohesive flock, with each breed displaying specific behavioral patterns. Decreasing space allowance and previous experience resulted in limited benefits for the successful group cohesion. Longer cohabitation periods might result in complete integration, although practical implementation might be difficult.

Relative expression analysis of IL-5 and IL-6 genes in tropical sheep breed Pelibuey infected with Haemonchus contortus.

Haemonchus contortus is a parasitic nematode of Pelibuey sheep, a meat breed used in tropical regions. Due to anthelmintic problems, the identification of hosts resistant to H.contortus is another option of control. The aim of this study was to analyse the relative expression of IL-5 and IL-6 genes in Pelibuey sheep after H.contortus infection. Nineteen lambs infected with H.contortus and three more lambs without infection were studied. The haemonchosis was determined by the number of eggs per gram of faeces (epg) and by the estimation of the percentage of the packed cell volume (%pcv). Peripheral blood mononuclear cells (PBMCs) were obtained to extract RNA at 0, 1, 2, 7, 14, 21 and 28days after infection to quantify the relative expression of IL-5, IL-6 and GAPDH by real-time PCR. Five lambs were classified as low responders (lr) to haemonchosis with averages of 1519±315·3 epg and 31·49±5·13%pcv, and 14 lambs were identified as high responders (hr) with averages of 530±132 epg and 34·88±3·75%pcv. The expression ratio of IL-5 was significantly different compared with control lambs at 2, 7 and 14days post-infection (PI), and IL-6 was significantly different after 14days. The highest level of relative expression for IL-5 and IL-6 genes was 9·9-fold and 12-fold after 2 and 14days for hr hosts (P<0·05) compared with control group, respectively. In conclusion, the Pelibuey breed in grazing areas exhibited different expression of IL-5 and IL-6 obtained from PBMCs against H.contortus, suggesting the importance of these cytokines in regulating the nematode infection.

Melatonin Receptor 1A (MTNR1A) gene sequence characterization and SNP identification in Tropical sheep breeds of India

Sheep is considered to be short day seasonal breeder. Sheep does show varying behavior in terms of seasonal reproduction between temperate and tropical latitudinal regions. MTNR1A gene has been studied widely for being linked to seasonality in sheep. Recently, through our studies we have characterized the MTNR1A gene in Tropical arid sheep breeds and could find out that the GG and CC genotypes are having higher prevalence in the tropical arid breed populationwith reference to two SNP markers ‘ ‘G612A’ and C606T’ respectively.

Caprinos e Ovinos Adaptados aos Trópicos

This review aimed to discuss the relevant aspects concerning the evaluation of the adaptability of goats and sheep in tropics. Based on the results, the best breeds of goats and sheep adaptaded to the tropics, and more specifically in the semiarid, are indicated for creation of this region.

Growth of sheep fed tannin-rich Albizia gummifera with or without polyethylene glycol.

Twenty-four intact male Bonga lambs were studied in a 100-day experiment to evaluate the effect of feeding tannin rich leaves of Albizia gummifera (AG) on nutrient utilization, growth performance, and carcass composition. The dietary treatments consisted of hay alone (T1, control), AG at 30% of control diet + T1 (T2), and T2 + polyethylene glycol 6000 (PEG) (T3, 40mg PEG, 1kg AG/head on a dry mass (DM) basis. The lambs were individually fed at 50gDM/kg live weight. In the last 10days of the experiment, all animals from each treatment were harnessed with feces collection bags. At the end of the experiment, lambs were slaughtered after overnight fasting for measurements of carcass characteristics. Crude protein, neutral detergent fiber, and condensed tannin contents of AG were 300, 586, and 108g/kg DM, respectively. Lambs fed AG with PEG had higher (P < 0.001) feed intake, digestibility, carcass weight, and weight gain compared with other treatments. Although lambs fed diet T2 were able to utilize AG, the efficiency of its utilization was lower (P < 0.001) than the PEG-treated groups. The improvement in nutrient intake and digestibility, carcass weight, and growth performance of lambs supplemented with PEG emphasizes the negative effect of tannins on livestock performance. Leaves of AG enhance digestibility and performance in tropical hay-fed sheep, and the addition of PEG further improves this effect, likely due to the binding of tannins.

“By endurance we conquer”: fat tailed sheep in the twenty-first century

In the temperate world, sheep are usually classified under two categories: wool and hair, where the latter are, in most cases, considered a relic of medieval times and not suitable for contemporary commercial sheep production. Additionally, in temperate countries, the sheep world is usually in black and white, as no other colors or mixing are commonly found. Interestingly, hair breeds are very adaptable to harsh environments like the churra breeds of the Iberian Peninsula or the Scandinavian hair breeds that thrive respectively in cold mountain ranges and sub-arctic islands. In the Tropics, however, the ovine world changes considerably: sheep have often (short) hair that tends to shed with changing seasons, and wool sheep are indeed a rare oddity. Additionally, tropical sheep are present in a vast array of coat-color patterns that eclipse the monochromatic nature of their relatives of temperate (mostly European) relatives. Besides these features, tropical sheep have a very distinctive and particular trait: the fat tail and/or fat rump, and are generally described as fat-tailed sheep (see Fig. 1). This morphological feature is characterized by an accumulation of fat mainly at the level of the hind quarters in varied shapes and volumes, and it is assumed to have similar physiological roles as those of the zebu or camel humps. Fat-tailed sheep distribution encompasses vast areas of the globe. They are the main ovine genetic resource in the Middle East and North Africa, Iran, Pakistan, Central Asian Republics, China and Mongolia, East and Southern Africa, and have important populations in agricultural export giants like Brazil or Australia. Interestingly, as to the best of our knowledge, in temperate countries, namely the European Union territory, there is only one autochthonous fat-tailed sheep breed: the Chios breed from the homonymous Greek Island near the Turkish coast. Regarding international diffusion, only two fat-tailed breeds may be classified as having acquired such preponderance: the Awassi breed original from several Middle East countries, improved in Israel and from there widespread to the entire world as a selected dairy breed and the Karakul (Astrakhan) breed form the former Soviet Union Republics of Central Asia that gained importance in the pelt production industry, curiously in fat-tailed sheep home range: Southern Africa and that nevertheless has lost the importance of the 1960s and 1970s. The wide distribution of fat-tailed sheep breeds may be explained by one particular trait: adaptability or endurance. In fact, these animals are able to thrive under extremely harsh conditions; they are able to tolerate hot weather, cope with dry environments with low pasture availability, able to walk long distances in search for pastures and drinking water, tolerate diseases and parasites, and even have gregarious and defense instincts that enable them to defend the flock from predators like jackals or foxes, similarly, to A. M. Almeida IICT–Instituto de Investigacao Cientifica Tropical & CIISA– Centro Interdisciplinar de Investigacao em Sanidade Animal, Lisbon, Portugal

Effect of diet inclusion of Tithonia diversifolia on feed intake, digestibility and nitrogen balance in tropical sheep

Feed intake and digestibility were evaluated in sheep fed low quality Taiwan grass supplemented with Tithonia diversifolia. Four wether hair sheep were housed in metabolic cages and fed with either Control concentrate 20%, Tithonia 20, 35 or 50% in a Latin Square design. Adaptation and, feces and urine collection periods were 14 and 7 days, respectively. Feed intake was increased (P 0.1) among sheep fed Tithonia, but different (P < 0.05) from control. Inclusion of Tithonia foliage at 20% of the DM diet of hair sheep improved their intake of low quality Taiwan grass and nitrogen retention. Higher levels of Tithonia in the diet, however, increase nitrogen loss in feces and urine.

Endogenous circannual rhythm in luteinizing hormone secretion: insight from signal analysis coupled with mathematical modelling

In sheep, as in many vertebrates, the seasonal pattern of reproduction is timed by the annual photoperiodic cycle, characterized by seasonal changes in the day length. The photoperiodic information is translated into a circadian profile of melatonin secretion. After multiple neuronal relays (within the hypothalamus), melatonin affects gonadotrophin-releasing hormone (GnRH) secretion, which in turn controls ovarian cyclicity. The pattern of GnRH secretion is mirrored by that of luteinizing hormone (LH) secretion, whose plasmatic level can be easily measured. We addressed the question of whether there exists an endogenous circannual rhythm in a tropical sheep (Blackbelly) population that exhibits clear seasonal ovarian activity when ewes are subject to temperate latitudes. We based our analysis on LH time series collected in the course of 3 years from ewes subject to a constant photoperiodic regime. Owing to intra- and interanimal variability and unequal sampling times, the existence of an endogenous rhythm is not straightforward. We have used time-frequency signal processing methods, and especially the smooth pseudo-Wigner-Ville distribution, to extract possible hidden rhythms from the data. To further investigate the low-frequency (LF) and high-frequency (HF) components of the signals, we have designed a simple mathematical model of the LH plasmatic level accounting for the effect of experimental sampling times. The model enables us to (i) confirm the existence of an endogenous circannual rhythm as detected by the LF signal component, (ii) investigate the action mechanism of the photoperiod on the pulsatile pattern of LH secretion (control of the interpulse interval), and (iii) conclude that the HF component is mainly due to the experimental sampling protocol.

Efficiency of estrous synchronization in tropical sheep by combining short-interval cloprostenol-based protocols and “male effect”

This study assessed the efficacy of a protocol combining short-interval cloprostenol-based protocols and “male effect” for estrous synchronization in hair sheep. In Experiment 1, 24 ewes were randomly assigned to three groups ( n = 8) and treated with cloprostenol on Days 3, 5 and 7 after ovulation, respectively. Estradiol secretion during the follicular phase was similar among groups. Onset of estrus ( P < 0.001) and the timing of maximum LH concentration ( P < 0.01) were earlier in group D3 than in D5 and D7 groups. During the subsequent cycle, the number and size of corpora lutea were higher ( P < 0.05) in ewes of the groups D3 (1.9 ± 0.3 and 115.1 ± 14.3 mm 2) and D5 (1.8 ± 0.2 and 100.2 ± 11.2 mm 2) than in group D7 (1.3 ± 0.2 and 75.6 ± 6.4 mm 2) group. In Experiment 2, 24 ewes were treated with two cloprostenol injections (7 days apart). Twelve ewes were exposed to “male effect” previous to an isolation period (ME group), whereas the remaining ewes were controls without male exposure (CTR group). Male effect induced earlier preovulatory LH surge ( P < 0.05) and ovulation ( P < 0.001) than CTR group. In Experiment 3, the estrus was synchronized in 68 ewes. Nineteen of them (group FGA) were treated using intravaginal sponges impregnated with fluorogestone acetate for 12 days and inseminated at 55 h. Forty-nine females (group ME) were treated like ME group. Twenty-four (ME48 group) and 25 ewes (ME55 group) were inseminated at 48 and 55 h after treatment, respectively. The fertility rate was numerically higher in ME48 than ME55 and FGA groups (62.5, 44.0 and 47.4%, respectively). In conclusions, the combined use of short-interval cloprostenol treatment and “male effect” may be an adequate alternative for synchronizing estrus and applying artificial insemination in hair sheep throughout the entire year.