Reproductive behavior in hair sheep rams under tropical conditions

The reproductive efficiency of sheep herds depends to a great extent on the ram. Male reproductive evaluation allows to select for the best and eliminate those with reproductive problems. The objective was to evaluate the effect of breed and age group on the reproductive behavior of hair sheep rams in the tropics of Mexico. Pelibuey (n?=?42), Blackbelly (n?=?30), Dorper (n?=?44), and Katahdin (n?=?30) rams of two age groups: young (n?=?74, 1–1.5 years old) and adult (n?=?72, 2–4 years old) were evaluated. Serving capacity (10-min duration) and breeding soundness evaluation (BSE) tests were carried out in each ram. In the first test, rams were classified as suitable and unsuitable, and in the BSE test, they were classified as satisfactory, questionable, or unsatisfactory. The response variables were analyzed using chi-square test or analyses of variance (ANOVA). ANOVA included the fixed effects of breed, age group, and their interaction. In the serving capacity test, 79.5% of the rams were considered suitable, with no breed differences (P?>?0.05). Adult rams (90.3%) had the highest proportion of suitable rams (P?<?0.05). In the BSE test, 80.2% of the rams were satisfactory; only breed being significant (P?<?0.05). Pelibuey breed had the highest proportion of satisfactory rams (91.4%). Breed × age interaction was no significant for any trait. After serving capacity and BSE tests, a high proportion of rams was found not suitable for reproduction (36.3%), which is expected to cause low fertility in the flock.

     

Reproductive seasonality in Saanen goats kept under tropical conditions

Tropical Animal Health and Production - This study aimed to verify the reproductive seasonality in Saanen goats from distinct parity orders (nulliparous, primiparous, and pluriparous) throughout an...     

Reproductive techniques in sheep.

This article reviews current methods of evaluating reproductive performance in the sheep industry. The reproductive technologies of breeding soundness examination, reproductive ultrasonography, estrus manipulation, artificial insemination, and embryo transfer are also extensively discussed. The veterinarian's current and future role in the application of these technologies is discussed.     

Reproductive seasonality in the mare: neuroendocrine basis and pharmacologic control

Reproductive seasonality in the mare is characterized by a marked decline in adenohypophyseal synthesis and secretion of LH beginning near the autumnal equinox. Thus, ovarian cycles have ceased in most mares by the time of the winter solstice. Endogenous reproductive rhythms in seasonal species are entrained or synchronized as a result of periodic environmental cues. In the horse, this cue is primarily day length. Hence, supplemental lighting schemes have been used managerially for decades to modify the annual timing of reproduction in the mare. Although a full characterization of the cellular and molecular bases of seasonal rhythms has not been realized in any species, many of their synaptic and humoral signaling pathways have been defined. In the mare, neuroendocrine-related studies have focused primarily on the roles of GnRH and interneuronal signaling pathways that subserve the GnRH system in the regulatory cascade. Recent studies have considered the role of a newly discovered neuropeptide, RF-related peptide 3 that could function to inhibit GnRH secretion or gonadotrope responsiveness. Although results that used native peptide sequences have been negative in the mare and mixed in all mammalian females, new studies that used an RFRP3 antagonist (RF9) in sheep are encouraging. Importantly, despite continuing deficits in some fundamental areas, the knowledge required to control seasonal anovulation pharmacologically has been available for >20 yr. Specifically, the continuous infusion of native GnRH is both reliable and efficient for accelerating reproductive transition and is uniquely applicable to the horse. However, its practical exploitation continues to await the development of a commercially acceptable delivery vehicle.     

Reproductive efficiency of Iceland sheep

Iceland sheep are found to be relatively early maturing and the level of reproductive efficiency in the flock is raised by breeding from ewe lambs. Ram lambs are normally used for mating. Ewe prolificacy is progressively being increased by genetic selection for a higher lambing rate in conjunction with improvements in feeding. Lamb mortality is kept at a relatively low level by close supervision at lambing and disease control.     

Mineral requirements of hair sheep in tropical climates

In this study, we evaluated the requirements of calcium (Ca), phosphorus (P), magnesium (Mg), sodium (Na) and potassium (K) for sheep hair growth. Experimental diets contained different levels of metabolizable energy [ME; 0.96, 1.28, 1.72, 2.18 and 2.62 Mcal/kg of dry matter, (DM), corresponding to 4.23, 5.64, 7.58, 9.61 and 11.55 MJ/kg DM]. The lambs' hair (n = 48) at 2 months of age presented an average body weight (BW) of 12.05 ± 1.81 kg. At the beginning of the experiment, eight animals were slaughtered as a reference group to estimate the initial empty body weight and body composition. Net mineral requirements (g/day) ranged from 0.73 to 0.71 g of Ca, 0.51 to 0.49 g of P, 0.026 to 0.026 g of Mg, 0.16 to 0.19 g of Na and 0.15 to 0.13 g of K for animals with a BW ranging from 15 to 30 kg and a daily gain of 100 g. The results of this study indicate that the net macromineral requirements for weight gain in Morada Nova lambs are different from the values commonly recommended by the Agricultural and Food Research Council.     

Selenium toxicosis in a flock of Katahdin hair sheep

Selenium supplementation by injection is a common practice. Acute toxicosis from dosaging errors may occur. In this report, 23 of 56 ewes and all 24 lambs injected with selenium died. Tissue, whole blood, and serum concentrations aided in the diagnosis. Caution should be taken when supplementing selenium by injection.     

Performance of three tropical hair sheep breeds.

The performance of three hair sheep breeds (Brazilian Somali, Morada Nova, and Santa Ines) was evaluated in the production environment of northeastern Brazil. Data from a total of 524 lambs sired by 21 rams and out of 190 ewes were analyzed. These data were collected from 1980 to 1983 at Sobral, Brazil from an experiment designed to compare performance of the three breeds. The traits included weights of lambs at birth, weaning, 8 mo, 10 mo, and yearling ages and ewe characters of weight at lambing (EWT), total lamb weight born (LWB), total lamb weight weaned (LWW), and prolificacy rate (PR). Differences (P < .01) among breeds were found for all characters. The Brazilian Somali, the smallest and slowest-gaining breed, was less sensitive to yearly variation than were the other breeds. The Santa Ines, the largest and fastest-gaining breed, was superior in LWB and LWW per ewe lambing. Averaged over the 4-yr period, the Morada Nova had the highest PR (1.82), and the Brazilian Somali and Santa Ines had similar PR (1.39 and 1.31, respectively). Environmental effects on PR due to yearly rainfall quantity and distribution pattern influenced lamb growth up to weaning and ewe reproduction performance. Breed x year (P < .05) interaction effects on PR were largely attributable to the Somali breed's exhibiting higher PR than the Santa Ines and Morada Nova breeds during the relatively wet years of 1981 and 1982.     

Reproductive seasonality in female goats adapted to a subtropical environment persists independently of food availability

The aim of this study was to determine whether the seasonal change in food availability provides a predictive cue that synchronizes the breeding season in goats adapted to the subtropical conditions of Northern Mexico. Groups of multiparous intact (n = 7) and ovariectomized does bearing a subcutaneous implant constantly releasing estradiol-l7β (OVX+E; n = 12) were allocated in two pens and received a constant amount of feed. Another group of OVX+E does (n = 10) was incorporated into a flock raised under natural grazing conditions with seasonal fluctuations in food availability. Blood samples were taken twice weekly. Ovulation of intact goats was inferred from plasma progesterone levels. In OVX+E does plasma levels of LH were measured. Intact does displayed seasonal variations in ovulation and the breeding season lasted from September to February. OVX+E goats displayed large seasonal variations in LH secretion regardless of whether they were fed constantly indoors or kept under natural grazing conditions (P < 0.0001). The mean date of increase in LH secretion varied between years (P < 0.0001) but did not differ between groups (naturally grazed: August 13 ± 10 days; constantly fed: August 26 ± 10 days). In contrast, the seasonal decline in LH secretion differed between groups: it was consistently delayed in constantly fed animals compared to those feeding naturally (naturally grazed: January 28 ± 4 days; constantly fed: February 24 ± 6 days, group effect, P < 0.01). These results show that local female goats from subtropical Mexico display large reproductive seasonality independently of food availability.     

Study on environmental indices and heat tolerance tests in hair sheep

The ability to predict the effects of climatic factors on animals and their adaptability is important for livestock production. The aim of the present study was to analyze whether existing indices are suitable for evaluating heat stress in Santa Ines and Morada Nova sheep, which are locally adapted hair sheep breeds from northeastern Brazil, and if the limits used to classify thermal stress are suitable for these breeds. Therefore, climatic, physiological, and physical parameters, as well as thermographic images, were collected in 26 sheep, 1 1/2 years old, from two genetic groups (Santa Ines 12 males and 4 females; Morada Nov. 7 males and 3 females) for 3 days in both morning (4:00 a.m.) and afternoon (2:00 p.m.) with six repetitions, totalizing 156 repetitions. Statistical analysis included correlations and broken-line regressions. Iberia and Benezra indices were the tolerance tests that best correlated with the assessed parameters. High correlations between environmental indices and rectal or skin surface temperatures was observed, which indicates that these indices can be used for Santa Ines and Morada Nova sheep raised in central Brazil. However, some indicative values of thermal discomfort are different from the existing classification. Therefore, in order to classify appropriately, the model used needs to be carefully studied, because these classifying values can vary according to the species and model. Further research is necessary to establish indicators of thermal stress for sheep breeds raised in the region.     

A comparative study of feeding behavior and digestive function in dairy goats, wool sheep and hair sheep

An intake and digestibility study was conducted with three groups (six animals per group) of yearling wether dairy goats (four Toggenburg, two Alpine), wool sheep (Targhee X Dorset) and hair sheep (St. Croix). Body weight (BW) ranged from 42 to 52 kg, averaging 47 kg. All animals were penned individually and given ad libitum access to a mixture of alfalfa-smooth bromegrass hay in pelleted, chopped or long form. Each group contained three ruminally cannulated animals. There were no apparent differences in the composition of feed consumed among goats, wool sheep and hair sheep, and no significant animal type X forage form interactions for any of the variables evaluated. Significant differences were observed in dry matter intake (DMI) between wool sheep, hair sheep and goats: 3.17%, 2.66% and 2.23% of BW, respectively (P less than .05). Daily water intake (WI) was greatest for wool sheep (P less than .05), but not different between hair sheep and goats. Total digestibility of dry matter (DM) and all fiber fractions were similar among animal types. For the cannulated animals, ruminal content weight and total ruminal volume were greatest for wool sheep (P less than .05). Ruminal acid detergent lignin (ADL) turnover was greater in wool and hair sheep than goats (P less than .05), but no differences were apparent for dry matter or neutral detergent fiber (NDF) turnover. For all animals, DMI, DMI/BW, digestible DMI and WI were greater for pelleted than chopped and long hay (P less than .05). Total ruminal volume, contents weight (on an absolute or BW basis) and fluid volume were lower in the cannulated animals consuming pelleted hay (P less than .05). Ruminal DM turnover rate was faster on pelleted than long hay, while DM turnover rate on chopped hay was intermediate. Turnover of ADL was faster on pelleted than chopped or long hay (P less than .05), but there were no differences among forage forms in NDF turnover rate. Fluid turnover rate was faster on pelleted and chopped than on long hay (P less than .05). Under the conditions of this study, no apparent differences were observed among animal types in the nutrient composition of feed consumed, ruminal or total tract digestibilities or rate of passage for dry matter. However, feeding behavior or selectivity differences under natural grazing conditions may deviate from what has been observed in confinement.     

Short communication: Estrus synchronization using progestogens or cloprostenol in tropical hair sheep

The objective of the experiment was to compare the use of a PGF2α analogue (Cloprostenol) IM, with an intravaginal progestagen sponge, flurogestone acetate (FGA), and equine chorionic gonadotropin (eCG) IM application protocol. A total of 30 cyclical hair ewes (54.07?±?0.5 kg live weight, body condition score 3.5?±?0.5, and age 3?±?1 years) were used. For the control group ewes (n?=?15), intravaginal sponges (IS) impregnated with 20 mg of FGA were inserted for 12 days with 500 IU of eCG IM at sponges withdrawal. For the PG group ewes (Treatment group n?=?15), two injections of Cloprostenol (75 mcg) were given 12 days apart. The presence of estrus was detected using two rams with 8 h interval beginning at the end of the treatment. Progesterone concentrations in blood were measured by solid phase radioimmunoassay. A student’s t test was performed to analyze the duration of estrus and the interval between the ends of the treatment and the onset of estrus (ET-OE) presentation. Progesterone levels were compared with two-way ANOVA, with treatment, and day of menstrual cycle as fixed factors. Treatment costs ratio was calculated by dividing the total costs of FGA IS application between total costs of Cloprostenol application. Significant differences (P?P?相似文献   

Reproductive performance of Finnish Landrace and Suffolk sheep maintained indoors year-round

The reproductive performance (fertility and prolificacy) of Finnish Landrace (Finn) and Suffolk sheep on an accelerated breeding program was evaluated. Both breeds were contained in each of two separate flocks housed indoors year-round on expanded metal floors in windowless buildings. The two flocks were bred alternately at 4-mo intervals in January, May and September. The sheep were exposed to either an abrupt (ALR) or constant (CLR) lighting regimen. Data from nine breedings during a 4-yr period were considered. Fertility was significantly higher for ewes in the ALR lighting regimen. Fertility was lower for ewes bred in September. For ewes that had lambed from breeding 8 mo earlier, fertility was higher for Finn ewes than for Suffolk ewes; however, similar fertility levels were observed in both breeds if the ewes had not lambed following the previous breeding. Higher prolificacy was observed in the Finn ewes than in the Suffolk ewes, but the differences in prolificacy varied with the month of breeding. The probability of a ewe having more than one lamb was significantly higher for Finn ewes than for Suffolk ewes in both January and May breedings, but was similar in September breedings. Incorporating the Finnish Landrace breed into an accelerated breeding program for sheep maintained indoors year-round is a practical way to increase the number of lambs born. Controlling daylength and dividing the flock into smaller flocks are also practical procedures to increase lamb production.     

Polymorphisms of the melatonin receptor 1A gene that affects the reproductive seasonality and litter size in Small Tail Han sheep

Previous researches have shown that MTNR1A plays an essential role in sheep reproduction. However, most researches focused more on the reproductive seasonality of sheep, and few scientists had studied the association of polymorphisms of the MTNR1A gene with ovine litter size and reproductive seasonality. Therefore, we chose MTNR1A gene to detect its novel sequence polymorphisms and population genetics and analyse their association with seasonal reproduction and litter size in ewes. The mRNA expression level in hypothalamus, pituitary and ovary was also detected. In this study, five polymorphisms (g.15118664G > T, g.15118683C > T, g.15118756C > T, g.15118774C > T and g.15118951G > A) were identified in exon 2. Most importantly, the g.15118683C > T and g.15118951G > A were significant difference between year‐round oestrous sheep and seasonal oestrous sheep (p < .01), and g.15118756C > T had a great effect on litter size of Small Tail Han sheep (p < .05). In addition, the mRNA expression level of MTNR1A in the hypothalamus of polytocous Small Tail Han sheep was significantly higher than that in monotocous Small Tail Han sheep (p < .01) and the expression of MTNR1A in the hypothalamus of year‐round oestrous sheep was significantly higher than that in seasonal oestrous sheep (p < .01). Polymorphisms in exon 2 may regulate the reproductive seasonality and litter size of ewes by influencing gene expression to regulate the reproductive seasonality and litter size of ewes. Our studies provided useful guidance in marker‐assisted selection of the litter size in Small Tail Han sheep.     

Breed differences in calving interval in the humid Mexican tropic

The objective of this study was to evaluate the influence of breed, breed and sex of the calf, farm, calving number (CN), type of calving, and their interactions on CI using records from four different beef breeds performing in the humid tropical environment of Mexico. The influence of these factors on CN was also evaluated. CI and CN varied with farm, breed of the dam, and with breed of the dam by calf breed interaction (P<0.001), while CI also varied with CN. Significant differences between Bos indicus and Bos taurus breeds for CI (432 vs. 488 days) and for CN (2.13 vs. 1.92) were observed (P<0.001). The interaction effects observed between breed of the dam by breed of the calf on CI and on CN were due to a favorable F₁ calf effect on CI observed only in Angus cows, although with an apparent unexpected negative impact on CN.     

High mortality and lesions of the central nervous system in trypanosomosis by Trypanosoma vivax in Brazilian hair sheep

Here, we report an outbreak of Trypanosoma vivax-induced trypanosomosis in Brazilian hair sheep on a farm in Paraíba state, a non-endemic region in northeastern Brazilian. Of 306 total sheep, 240 showed clinical signs and 216 died. Clinical signs included anorexia, lethargy, anemia, rough hair coat, weight loss, submandibular edema, abortion, and in some cases, neurological signs such as head pressing, lateral recumbence, paddling movements and muscle tremors. T. vivax was identified by blood smear analysis and polymerase chain reaction (PCR). At necropsy, animals exhibited watery blood, pale tissue coloring, and the presence of liquid in the peritoneal cavity and pericardial sac. Histologically, nonsuppurative myocarditis and meningoencephalitis with areas of malacia were observed. After treatment, no parasites were detected by blood smear analysis or PCR. Cattle and buffalo that remained in the same pasture were also infected but presented with asymptomatic infections. Epidemiological data suggest that T. vivax was introduced to the farm and the susceptible flock by buffalos that were asymptomatic carriers of the infection; T. vivax was most likely transmitted by Tabanus spp. bites and also iatrogenically.     

Simulation of genetic and environmental interaction of three tropical hair sheep breeds.

The Texas A&M Sheep Simulation Model was used to examine genetic-environmental interactions (GEI) among Brazilian Somali, Morada Nova, and Santa Ines breeds and type and level of feed supplement in northeast Brazil. Two sets of simulations were conducted to examine effects of different supplement quality (napier grass vs cunha legume) and quantity (napier grass only). The analyses indicated the benefits from supplementing lambs at weaning during the dry season and from supplementing lactating ewes at the beginning of lambing season when forage is scarce. The cunha legume was an effective supplement, but choosing between cunha legume and napier grass is an economic consideration. Increasing the amount of napier grass supplement per ewe from 200 g/d to 400 g/d resulted in a significant GEI (i.e., different levels of response such as lamb mortality rate, lamb weaning weight, and lambing rate for different breeds). The Brazilian Somali was the least responsive, whereas the Santa Ines was the most responsive to supplementation. It was concluded that the level of supplement should be higher for the Santa Ines and Morada Nova than for the Somali. The amount of supplement should be regulated so that it neither substitutes for nor lowers the utilization of the native caatinga forage. None of the breeds was simulated to be superior in all environments. Thus, considering the wide range of resources of individual farmers, any one of these breeds may be the preferred choice, depending on the individual set of production resources.