Estrus response and fertility after a single cloprostenol treatment in dairy cows with various ovarian structures

The objective of this study was to determine rates of estrus and conception in lactating multiparous Holstein cows given 500 μg of cloprostenol intramuscularly after detection of the following ≥ 60 d after parturition: a solid corpus luteum (CL), a CL with a nonechodense cavity ≤ 20 mm in diameter (CLcav), a luteal cyst (cavity > 20 mm in diameter and a luteinized wall > 3 mm in diameter), or a follicular cyst (cavity > 20 mm and a luteinized wall ≤ 3 mm in diameter). The estrus rates were 335/419 (80.0%), 183/223 (82.1%), 170/182 (93.4%), and 44/87 (50.6%), respectively (P < 0.0001), and the conception rates 30 to 36 d after insemination among the estrous cows with an apparently normal mucus discharge were 130/285 (45.6%), 44/141 (31.2%), 39/79 (49.4%), and 19/30 (63.3%), respectively (P < 0.002). Compared with a solid CL, a CLcav did not affect the estrus rate but significantly reduced the conception rate (P < 0.05), and the estrus rates were significantly higher and lower in cows with a luteal or follicular cyst, respectively (P < 0.05).     

Effects of a single injection of LHRH on the response of anestrous ewes to the introduction of rams

Two methods of induction of ovulation were examined in Manchega ewes that were in postpartum anestrus during the nonbreeding season. The experiment was of 2 X 2 X 3 factorial design. The methods compared were introduction of rams and this treatment plus an im injection of 50 micrograms luteinizing hormone releasing hormone (LHRH) at the time rams were introduced. Variations in response due to month of treatment (April, May or June) and interval from lambing to treatment (1, 2 or 3 mo) and their interactions with type of treatment were examined. Responses studied were proportions of ewes showing increases in plasma progesterone at (a) 10 d or (b) 17 or 24 d post-treatment, or lambing by 200 d post-treatment, and interval from treatment to lambing for ewes that did lamb by 200 d. The formation of a corpus luteum was determined by concentrations of progesterone in plasma; a positive response was considered to be a concentration greater than .5 ng/ml (baseline values averaged .1 ng/ml). Overall, there was no benefit of LHRH above the response to introduction of males only, in any trait examined. There was a significant interaction of treatment with month of treatment on the proportion of ewes forming corpora lutea by 17 or 24 d after initiation of treatment. This proportion was lower in June (38 vs 66% in April and 82% in May) for ewes receiving LHRH, but did not differ among months (61 to 68%) for ewes exposed to males only.(ABSTRACT TRUNCATED AT 250 WORDS)     

A comparison of Dorset and Finnish Landrace crossbred ewes

Data from 644 exposures and 552 lambings were used to analyze reproductive traits of 1/2-Finnish Landrace, 1/2-Dorset ewes (1/2 Finn); 1/4-Finnish Landrace, 3/4-Dorset ewes, (1/4 Finn) and Dorset ewes. Ewes were exposed to Hampshire or Suffolk rams for spring lambing from 1973 to 1978. The analytical model included fixed effects of ewe birth year (EBY), ewe breed (BR), lambing year within EBY and EBY X BR interaction and random effects of ewe within EBY and BR. Conception rate differed (P less than .01) for 1/2-Finn (.94), 1/4-Finn (.88) and Dorset (.80) ewes. Litter size was highest (P less than .01) for 1/2-Finns (1.97), followed by 1/4-Finns (1.74) and Dorsets (1.44). The 1/2-Finn ewes ranked first for number and weight of lambs weaned, and for number and weight marketed as feeder lambs. Birth weights were heavier (P less than .001) for lambs with Dorset dams (3.88 kg) than for lambs with 1/4-Finn (3.24 kg) or 1/2-Finn (3.08 kg) dams. Preweaning average daily gains and adjusted 90-d weights were also larger (P less than .001) for lambs with Dorset dams (.26 kg/d and 28.3 kg, respectively) than for lambs with 1/4-Finn (.24 kg/d and 25.4 kg) or 1/2-Finn (.24 kg/d and 25.1 kg) dams. However, Dorset ewes lambed an average of 10.5 d later than Finn-cross ewes, and actual weaning weights (unadjusted for age) did not differ significantly among lambs from Dorset (27.2 kg), 1/4-Finn (26.9 kg) and 1/2-Finn ewes (26.7 kg).(ABSTRACT TRUNCATED AT 250 WORDS)     

Resistance of Santa Ines and crossbred ewes to naturally acquired gastrointestinal nematode infections

This trial was carried out in Piracicaba, São Paulo State, Brazil, to comparatively evaluate the degree of resistance to naturally acquired gastrointestinal nematode infections in sheep of the following genetic groups: purebred Santa Ines (SI), SI crossbred with Dorper (DO × SI), Ile de France (IF × SI), Suffolk (SU × SI), and Texel (TE × SI). Fifteen ewes from each group were raised indoors until 12 months of age. At this age, they were moved to pasture that was naturally contaminated by nematode infective larvae and were evaluated from December to May, 2007. Rainfall ranged from 267 mm in January to 37 mm in April. Maximum and minimum mean temperatures ranged from 32.5 °C to 19.0 °C in March and from 25.9 °C to 12.8 °C in May. There was an increase in the mean number of eggs per gram of feces (EPG) after animals were placed on pasture with significant difference between the SI (80 EPG) and IF × SI (347 EPG) groups in January; and the DO × SI (386 EPG) and TE × SI (258 EPG) groups in May. The highest mean fecal egg count (FEC), 2073 EPG, was recorded for the TE × SI group in February. All groups showed a progressive reduction in body weight throughout the experiment of 12.0% (TE × SI) to 15.9% (SU × SI). In general, the animals with the highest FEC presented the lowest packed cell volumes (PCV); the highest correlation coefficient between FEC × PCV occurred in the SU × SI sheep in January (r = −0.70; P < 0.01). Similarly, there was an inverse relationship between FEC and blood eosinophil values, with the highest correlation coefficient in the TE × SI sheep in February (r = −0.64; P < 0.05). Immunoglobulin G (IgG) levels against Haemonchus contortus antigens increased in all groups as a result of the exposure to parasites and remained relatively constant until the end of the study, with the exceptions of SU × SI and TE × SI, which showed a rise in IgG levels during the last sampling that coincided with a reduction in mean FEC. In conclusion, crossbreeding Santa Ines sheep with any of the breeds evaluated can result in a production increase and the maintenance of a satisfactory degree of infection resistance, especially against H. contortus and Trichostrongylus colubriformis, the major nematodes detected in this flock.     

Comparison of Finnish landrace crossbred ewes with Columbia, Rambouillet and Targhee ewes on western range

The objective of this study was to compare reproductive efficiency and wool production of 1/4 Finn crossbred ewes with straightbred Columbia, Rambouillet and Targhee ewes. In Phase I, white-faces ewes (WF; Columbia, Rambouillet and Targhee) were bred to either rams of their own breed or Finnish Landrace X Rambouillet rams (F X R) to produce 821 lambs from 563 lambings. Ewes bred to F X R had similar average litter size and individual lamb weights at birth, 60 d and weaning as those bred to WF. Lambs sired by F X R had 7% higher (P less than .01) lamb weaned per ewe lambing for ewes bred to F X R rams. For Phase II, approximately equal numbers of F X R-sired (1/4Fx) and WF-sired female lambs produced in Phase I each year were exposed to Suffolk rams at yearly intervals beginning at 7 mo of age. At 1 yr of age, 1/4Fx had higher fertility (P less than .01) than WF (37.7% vs 1.3%), resulting in 14.0 kg more lamb weaned per ewe exposed to breeding. Mature (ages 2 to 6 yr) 1/4Fx ewes had similar fertility to mature WF ewes, but litter size, number of lambs at 60 d and weaning was .36, .24 and .22 lambs higher (P less than .01), respectively, for mature 1/4Fx. Progeny of 1/4Fx were lighter at birth (P less than .01), but not different (P greater than .05) at 60 d and weaning than those of WF. Survival to 60 d unadjusted and adjusted for birth weight was 4.6% (P less than .05) and 7.6% (P less than .01) higher, respectively, for 1/4Fx progeny than for WF progeny.(ABSTRACT TRUNCATED AT 250 WORDS)     

Production efficiency of crossbred ewes and that of their daughters and granddaughters

Ewes of eight crossbred groups, born in 1973 and 1974, were maintained under two pasture management systems for five and four production years, respectively. After that experiment terminated, those crossbred ewes produced Polypay-sired lambs in 1979 and were then sold. Ewe lambs from those three-bred crosses were backcrossed to Polypay rams to produce lambs from 1980 to 1983. Five ancestor-descendant data sets (three involving dams and daughters and two involving granddams and granddaughters) were examined to study relationships between production efficiency of ancestor ewes and similar traits measured on their descendants. Ancestor cumulative prolificacy was positively but not significantly associated with cumulative prolificacy in the descendants. Regressions of descendant net revenue on ancestor net revenue were predominantly negative but generally were not significant. There was a tendency for prolific ancestors to produce costly but less profitable descendants. These results may be due to economic conditions (high feed costs and low lamb values) that persisted during the course of the experiment.     

Ovulation rate and litter size of Barbados, Targhee and crossbred ewes

Ovulation rate was measured in Barbados Blackbelly (United States strain; B), Targhee (T), Barbados X Targhee (B X T) and Barbados X Dorset-Targhee (B X DT) ewes at first and second estrus following synchronization of cycles early in the breeding season. Body weight at sponge removal differed (P less than .001) between B (30.9 kg) and T ewes (54.9 kg) and was intermediate for B X T (44.9 kg) and B X DT (43.5 kg) ewes. Ovulation rate was higher (P less than .01) at first and second estrus for B (1.86, 2.04), B X T (1.93, 2.04) and B X DT (1.72, 1.80) than for T (1.29, 1.40) ewes. Regressions of ovulation rate on body weight within the breed groups did not differ significantly from each other and the average was significant (b = .049 +/- .014 CL/kg at first estrus and b = .046 +/- .011 CL/kg at second estrus, where CL = number of corpora lutea), but differences between the groups in body weight did not explain the differences in ovulation rate. Litter size for B, B X T, B X DT and T groups was 1.71, 1.84, 1.84 and 1.28, respectively. The B X T ewes were superior to the average of the B and T ewes for ovulation rate (P less than .05) and litter size (P less than .01); there was no direct estimate of embryo survival, but the results indirectly indicate superiority of the crossbreds for this component also.(ABSTRACT TRUNCATED AT 250 WORDS)     

Milk yield of Chios-Ossimi crossbred ewes in relation to the yield of the parental breeds

Summary A study was carried out at Mallawi Research Station, 300 km south of Cairo, in which 16 Chios (CC), 31 Ossimi (OO) and 21 of their F₁ crossbred ewes (50% Chios- 50% Ossimi (CO)). The CO crossbred ewes were mated to CC rams, whereas OO and CC ewes were mated to rams of the same breeds. The study included only ewes having single lambs in 2 lambing seasons; summer and winter. In the summer, total 8-week milk yield (suckling period) averaged 128·9, 53·4 and 77·1 kg in CC, OO and the crossbred ewes, respectively (P<0·01). Total milk yield averaged 201·6, 65·0 and 110·2 and days of lactation were 151·1, 79·6 and 106·7, respectively (P<0·01). In the winter, total 8-week milk yield averaged 138·6 (P<0·01), 55·0 and 59·5 kg for CC, OO and the crossbred ewes, respectively. Total yield averaged 209·1 (P<0·01), 65·9 and 76·5 kg and days of lactation were 153·3, 79·8 and 93·4, respectively (P<0·01).

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Produccion De Leche De Cruces Ovinos Chios-Ossimi En Relacion Con La Produccion De Las Razas Progenitoras

Resumen Se llevó a cabo un estudio en la Estación Experimental Mallawi, localizada 300 km al sudoeste del Cairo, con 16 Chios (CC), 31 Ossimi (OO) y 21 de sus cruzas F₁ (50% Chios-50% Ossini (CO)). Las ovejas cruzadas CO fueron cruzadas con machos CC, mientras que las ovejas OO y CC fueron cruzadas con machos de la misma raza. El estudio incluyó solamente ovejas que tuvieron partos sencillos en 2 períodos de pariciones; verano e invierno. En el verano, el total de 8 producciones semanales durante el período de amamantamiento promediaron 128·9, 53·4 y 77·1 kg en CC, OO, y en las ovejas cruzadas, respectivamente (P<0·01). El total de la producción de leche promedió 201·6, 65·0 y 110·2, siendo los días de lactación de 151·1, 79·6 y 106·7, respectivamente (P<0·01). En el invierno, el total de 8 producciones semanales promediaron 138·6 (P<0·01), 55·0 y 59·5 kg para CC, OO y los cruces, respectivamente. El promedio del total producido fue de 209·1 (P<0·01), 65·9 y 76·5 kg, siendo los días de lactación de 153·3, 79·8 y 93·4, respectivamente (P<0·01).

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Rendement Laitier De Brebis Croisees Chios X Ossimi Par Rapport A Celui Des Races Parentales

Résumé Une étude a été réalisée à la station expérimentale de Mallawi, à 300 km au sud du Caire, sur 16 brebis Chios (CC), 31 Ossimi (OO) et 21 croisées de première génération (50% Chios-50% Ossimi (Co). Les brebis croisées (Co) ont été saillies par des béliers CC tandis que les brebis OO et CC étaient saillies par des béliers de mêmes races. L'étude ne concerne que des brebis n'ayant qu'un seul agneau en 2 saisons d'agnelage: été et hiver. Pour la période d'été, le rendement laitier total de 8 semaines (période d'allaitement) était en moyenne de 128,9–53,4 et 77,1 kg chez les brebis CC, OO et croisés, respectivement (P<0,01). Le rendement laitier total atteignait des moyennes de 201,6, 65 et 110,2. Les jours de lactation étaient de 151,1, 79,6 et 106,7 respectivement (P<0,01). En hiver, le rendement laitier total sur huit semaines était en moyenne de 138,6 (P<0,01), 55 et 55,5 kg pour CC, CO et les brebis croisées, respectivement. Le rendement total moyen était de 209,1 (P<0,01), 65,9 et 76,5 kg et les jours de lactation étaient de 153,3, 79,8 et 93,4 (P<0,01) respectivement.

     

Relative resistance of Dorper crossbred ewes to gastrointestinal nematode infection compared with St. Croix and Katahdin ewes in the southeastern United States

A study was conducted to evaluate relative resistance of Dorper crossbred (DO), Katahdin (KA), St. Croix (SC), and Hampshire (HA) ewes to natural and experimental gastro-intestinal (GI) nematode infection over a 20-month period. The objective of Experiment 1 was to evaluate breeds for resistance to infection acquired naturally from mixed grass pastures. In Year 1 (May-December 2000) de-worming of ewes occurred during wet, hot conditions in July and during late pregnancy in December. In Year 2 (January-December 2001), ewes were de-wormed after fecal egg count (FEC) for a breed group rose above 1000 eggs per gram (epg) or after blood packed cell volume (PCV) of an individual ewe fell below 20. FEC was determined every 28 days and PCV every 14-28 days. In both the years, ewes were pastured together, except during the 28-days breeding periods, on tall fescue, bermudagrass, or ryegrass, and rotated among pastures dependent on forage availability. Ewes were in good or excellent condition (body condition score of 3-4 out of 5) throughout the study. The objective of Experiment 2 was to evaluate the breeds for relative resistance to an experimental infection with Haemonchus contortus infective larvae. Both PCV and FEC were determined every 7 days from 14 to 42 days after inoculation with 30000 infective larvae per ewe. In Experiment 1, Year 1, FEC was slightly greater and PCV was lower from July to September in DO ewes (breed x time, P<0.001). In Year 2, de-worming occurred 14 days later in DO ewes compared with other breed types. Otherwise PCV and FEC were similar among the hair breeds and higher and lower, respectively, compared with HA ewes (breed x time, P<0.001). In Experiment 2, FEC and PCV were similar among hair breeds; FEC was lower and PCV higher in hair breeds compared with that of HA ewes (P<0.01). Relative resistance of mature Dorper crossbred ewes was comparable to that of Katahdin and St. Croix ewes and superior to that of Hampshire ewes.     

Role of ovarian progesterone and potential role of prostaglandin F2alpha and prostaglandin E2 in modulating the uterine response to infectious bacteria in postpartum ewes

In sheep and cattle, the postpartum uterus is resistant to bacterial challenge until after corpora lutea develop. A 2 x 2 factorial arrangement of treatments was used to determine whether prostaglandins may mediate the effects of progesterone in transforming the postpartum uterus from resistant to susceptible. On d 14 postpartum, ewes (n = 6/group) were ovariectomized or sham ovariectomized, and the vena cava was catheterized for daily collection of uteroovarian-enriched blood. From d 15 to 20, ewes received twice daily intramuscular injections of progesterone in sesame oil or plain sesame oil. On d 20, each uterus received 75 x 10(7) cfu of Arcanobacterium pyogenes and 35 x 10(7) cfu of Escherichia coli. Uteri were collected on d 25 and examined for signs of infection. For each blood sample, unstimulated and mitogen-stimulated lymphocyte proliferation was measured as [3H]thymidine incorporation, smears were prepared for differential white blood cell (WBC) counts, and progesterone, prostaglandin F2alpha, (PGF2alpha), and prostaglandin E2 (PGE2) were quantified. All 12 progesterone-treated, but only two of the 12 oil-treated, ewes developed uterine infections (P < 0.001). Progesterone treatment increased (P < 0.001; 3.1 vs 1.5 ng/mL) and ovariectomy decreased (P < 0.001; 3.7 vs 0.9 ng/mL) vena caval progesterone. Progesterone treatment reduced (P < 0.01) PGF2alpha, (303.9 vs 801.3 pg/mL), and PGF2alpha was greater (P < 0.05) before than after inoculation (626.4 vs 478.8 pg/mL). The PGE2 concentration was greater in progesterone-treated, ovary-intact ewes than in ewes in the other groups (ovariectomy x progesterone treatment; P < 0.01). Ovariectomy increased (P < 0.005; 4.4 vs 2.9 pmol) and progesterone treatment decreased (P < 0.05; 3.2 vs 4.1 pmol) concanavalin A-stimulated lymphocyte proliferation. Ovariectomy increased lipopolysaccharides-stimulated proliferation (P < 0.05; 2.4 vs 1.9 pmol). For neutrophils per 100 WBC, the ovariectomy x progesterone and progesterone x period interactions were significant (P < 0.01). The ovariectomy x progesterone interaction was significant (P < 0.01) for lymphocytes per 100 WBC. Ovariectomy decreased monocytes (P < 0.001; 10 vs 13) and increased eosinophils (P < 0.001; 10 vs 5) per 100 WBC. Progesterone makes the postpartum uterus in ewes susceptible to infection, but ovariectomy allows ewes to remain resistant; uterine prostaglandins may mediate this change. This model creates opportunities to determine the mechanisms responsible for the shift from resistance to susceptible.     

Genetic, environmental and interaction effects on lifetime production efficiency of crossbred ewes

A total of 399 crossbred ewes born in 2 yr were maintained either on irrigated or dryland hill pastures. The ewes were sired by North Country Cheviot, Dorset, Finnsheep or Romney rams mated to Suffolk or Columbia-type ewes. The crossbred ewes were mated to Hampshire rams throughout the study and had the opportunity for either 4 or 5 yr of production. Annual feed cost was calculated based upon estimated annual metabolizable energy (ME) requirements for maintenance, ewe growth, pregnancy and lactation. Income from weaned feeder lambs and from orphan lambs sold shortly after birth, feed cost and net revenue were analyzed during each ewe's first production year, as well as for the entire period of the experiment. Crossbred group significantly affected income from lambs produced, feed cost and net revenue for the ewes' first production year. Crossbred group and crossbred group X management system interactions generally influenced lifetime income from lambs produced and from orphans sold, gross income, total cost and net revenue per ewe. Finnsheep X Suffolk ewes performed best on irrigated pastures but were below average for lifetime net revenue on hill pastures. Finnsheep X Columbia ewes performed best on hill pastures and, with Dorset X Suffolk and Dorset X Columbia ewes, were well above average for lifetime net revenue on irrigated pastures as well. Suffolk crossbreds consistently performed better on irrigated than on hill pastures. While most ewes with Columbia-type inheritance were more efficient on hill than on irrigated pastures, this result was not always consistent.     

Adult body weight of indigenous and crossbred ewes under semi-arid conditions in India

Data on adult body weight of ewes belonging to Nali, Chokla breeds and their crosses (F1) with Rambouillet and Soviet Merino raised under semi-arid conditions in India were analysed. The ewes belonged to 5 distinct age groups ranging from 16.5 to 64 months. Nali and Chokla were significant lighter than all the 4 crossbred groups. There were no significant differences in body weight between crossbred groups except in the case of Soviet Merino x Chokla group which was the lightest and differed significantly from all other groups. Rambouillet crosses were heavier than Merino crosses but the difference was statistically significant only on Rambouillet x Chokla and Merino x Chokla. The improvement in body weight in crossbreds over native sheep ranged between 9.3 and 21.88%. The increase in live weight was significant only up to 49 months.     

Androgen and oestrogen response to a single injection of hCG in cryptorchid horses

Androgen (testosterone and androstenedione) and oestrogen (oestradiol -17 beta and oestrone) concentrations were measured by radio-immunoassay in the peripheral plasma of two geldings (five-years-old), three bilateral cryptorchids (two, two and a half, and five-years-old) and three normal intact stallions (four, five and five and a half-years-old) before and after a single injection of 10,000 iu human chorionic gonadotrophin (hCG). In the stallions, hCG administration resulted in an immediate sharp increase of conjugated oestrogens and a more gradual increase of unconjugated androgens. In the cryptorchids, the unconjugated androgens increased following a similar pattern to that observed in the stallions, but reached lower peak values, whereas the conjugated oestrogens showed only a very slight increase. In the stallions and cryptorchids, the maximum oestrogen levels were reached two days after injection, whereas the maximal levels for androgens were reached a day later. In the geldings, hCG injection had no effect on plasma steroid levels. It is suggested that the measurement of unconjugated androgens (testosterone or/and androstenedione) before and three days after intravenous injection of 10,000 iu hCG may prove useful for the diagnosis of cryptorchidism or exploration of testicular function in stallions.     

Fattening performance of purebred and crossbred lambs from fat-tailed Kurdi ewes mated to four Iranian native ram breeds

A crossbreeding experiment was carried out to determine the sire breed effects on fattening performance of fat-tailed lambs. Rams from four Iranian fat-tailed sheep breeds, namely Kurdi (K), Afshari (A), Chaal (C) and Sanjabi (S) were mated to Kurdi ewes producing 454 progeny of four genotype groups (KK, AK, CK and SK). A total of 80 lambs comprising ten female and ten male lambs from each genotype group were used in a fattening experiment during a period of 88 days. Genotype of the lamb had significant effect on average dry matter intake (ADMI) (P < 0.05). SK lambs had the lowest ADMI. Average daily gain (ADG) and food conversion ratio (FCR) were not influenced by genotype of the lamb. Sex of the lamb had significant effect on both ADG and FCR (P < 0.01). Slaughter weight (SLW), hot carcass weight (HCW), cold carcass weight (CCW) and daily carcass gain (DCG) were not affected by lamb's genotype. However, genotype had significant effect on dressing percentage, carcass loss percentage (P < 0.01), carcass length (CL), leg circumference (LC), carcass compactness (CC) (P < 0.01) and carcass density (CD) (P < 0.05). Carcass width (CW) and leg length (LL) were not affected by lamb's genotype. Sex of the lamb had significant effects on CL, CW, LC, CC, CD (P < 0.01) and LL (P < 0.05). The results indicated the existence of sire breed difference for daily dry matter intake and carcass conformation in the fat-tailed sheep.