Reproductive characteristics of Ethiopian highland sheep. I. Genetic parameters of testicular measurements in ram lambs and relationship with age at puberty in ewe lambs.

A study was conducted to estimate heritabilities of, and genetic correlations among, body weight (WT) and testicular measurements - scrotal circumference (SC), testicular diameter (TD), testicular length (TL) and epididymal diameter (ED) - in ram lambs between 6, 9 and 12 months old, and relationship of the testicular traits with age at puberty in ewe lambs (AP). Two fat-tailed sheep breeds, the Horro and Menz, indigenous to the Ethiopian highlands were studied. Experimental lambs were produced by mating 250 oestrus-synchronized ewes of each breed to 10 sires in a single-sire mating system over three mating periods which produced, for this study, a total of 361 ram lambs and 148 ewe lambs, with substantial pedigree information, in two dry seasons (October/November 1992 and 1993) and one wet season (June/July 1993). Mean AP was 322.7 days. Breed was not significant (P0.05) for all testicular measurements, except ED at 9 months for which the Horro had a higher (P<0.01) value (20.6, s.e. 0.38 versus 19.3 s.e. 0.30). Horro ewe lambs had their first oestrus 28 days earlier (P<0.05) than the Menz. Heritability estimates were obtained from a sire model (M1) and from an individual animal model with additive direct and maternal effects (M2). The maternal effect was not fitted in M2 for AP. Repeatability and heritability estimates were also obtained by analysing records at the three ages in a repeated measures model (M3). M1 and M2 heritability estimates were generally low to moderate but were associated with large standard errors. Heritability estimates for testicular measurements were generally similar to those for WT. Among the testicular measurements, SC had the highest heritability estimates at 6 (0.45, s.e. 0.24 for M1) and at 12 months (0.41, s.e. 0.21 and 0.41, s.e. 0.20 for M1 and M2, respectively). Model 3 heritability estimates were 0.29 (s.e. 0.14), 0.24 (s.e. 0.12), 0.09 (s.e. 0.07), 0.11 (s.e. 0.08) and 0.12 (s.e. 0.08) for WT, SC, TD, TL and ED, respectively. Only repeatability estimates for WT (0.34, s.e. 0.02) and SC (0.25, s.e. 0.03) were significant. Heritability of AP was estimated at 0.16 (s.e. 0.21) by M1 and 0.14 (s.e. 0.19) by M2. Genetic correlations of AP with testicular measurements, especially with SC (-0.57, s.e. 0.38 and -0.78, s.e. 0.33, at 9 and 12 months, respectively) and TD (-0.72, s.e. 0.33 and -0.83, s.e. 0.48), were desirable and generally high. Adjustment of testicular measurements for liveweight consistently resulted in a reduction in estimates of heritability and genetic correlations. SC was suggested as the most appropriate selection candidate for the genetic improvement of both male and female reproductive performance in these breeds.

Breed and season effects on the peri-parturient rise in nematode egg output in indigenous ewes in a cool tropical environment.

A study was carried out at the International Livestock Research Institute (ILRI) Debre Berhan Research Station in Ethiopia from 1992 to 1995 to compare the peri-parturient rise (PPR) in faecal nematode egg counts (FEC) in ewes of two indigenous sheep breeds. A total of 1439 Menz and 1347 Horro ewes were single sire mated following oestrus synchronization to lamb in the wet and dry season. Three ewe treatment groups were constituted as mated/lactating/undrenched; mated/lactating/drenched; unmated/undrenched for three wet and three dry lambing seasons. All ewes grazed naturally contaminated pasture. Levels of faecal egg output were monitored at mating, 3 months after mating, 2 weeks before lambing, 4, 8 and 12 weeks post-lambing. A significant PPR in FEC occurred 2 weeks before lambing and peaked at 4 weeks post-parturition in ewes lambing just before the beginning of the dry season (October/November). There was no significant increase in FEC when lambing occurred before the onset of the long rainy season (May/June). The PPR in this study was associated with both lactation and seasonal availability of third-stage infective larvae on pasture. There was no consistent breed difference in FEC during the six sampling periods from mating to weaning. Faecal cultures and worm counts from both breeds confirmed the presence of Longistrongylus (Pseudomarshallagia) elongata, Trichostrongylus spp.and Haemonchus contortus. The role of the peri-parturient rise of FEC in ewes in gastrointestinal nematode transmission is discussed.

The epidemiology of nematode infections in sheep in a cool tropical environment.

The epidemiology of nematode infections in Menz sheep was studied in the highlands of Ethiopia at the International Livestock Research Institute (ILRI), Debre Berhan Research Station, using a series of tracer lambs grazing contaminated pasture for either 4, 16, 32 or 48 weeks from July 1992 to June 1994. The basic nematode seasonal infectivity pattern was expressed in terms of relative numbers of third-stage larvae (L3) available on pasture for different months. Data from faecal nematode egg counts, pasture larval recoveries and worm counts from the tracer lambs were used to investigate the infectivity pattern. Four nematode species of economic importance: Longistrongylus (Pseudomarshallagia) elongata, Trichostronglylus colubriformis, Haemonchus contortus, and Dictyocaulus filaria, were recovered from sheep. The largest numbers were recovered during the wet season (i.e. July to November) with peaks in late August and early September. During this 2 year study period, the seasonal pattern of sheep gastrointestinal nematodes was clearly defined. An important finding was that conditions during the short rainy season (i.e. March-May) were not conducive to the development and survival of nematode eggs and the free-living stages, hence little or no transmission occurred. Rainfall and humidity seemed to be the most important factors for the development of eggs and free-living stages. The period of acquisition of third-stage larvae from pasture was found to be relatively short, suggesting that a strategic control programme is feasible with minimal anthelmintic use. Results from the studies are discussed in relation to control strategies.

Semen characteristics of Ile-de-France rams of different age and physical condition.

A breeding soundness examination (BSE) involving animal physical examination, scrotal circumference (SC) and semen evaluation was undertaken on 80 Ile-de-France rams at a government breeding farm, 32 km south-west of Casablanca (Morocco) from March to May 1988. A large percentage of rams (21.4%) was found to be unfit for breeding due to physical and genital abnormalities; 11 and 5% had disorders of the feet and respiratory system; upon genital palpation, 17.5, 13.8 and 7.5% of animals had orchitis, epididymitis and posthitis, respectively. The SC increased with age from 28.8+/-3.2 cm at

[Livestock diseases in periurban dairy systems of sub-Saharan Africa: ILCA's approach]. / Maladies d'élevage dans les systèmes laitiers périurbains d'Afrique sub-saharienne: l'approche du CIPEA.

Dairy production to supply African urban centers is one of the dynamic livestock sectors in sub-Saharan Africa (periurban dairy farms). There is a modification in the relative impact of economically important diseases: these farms have an increased capacity to control the major traditional African diseases through genetic or health interventions, hence favouring the emergence of diseases of intensification, which affect dairy production. In this framework, the International Livestock Centre for Africa is starting a research programme which aims, by an ecopathological approach, to judge the true existence of this pathology as opposed to the major African diseases, and to compare its economic importance in various agroecological zones.

Seasonal variation in ovarian and oestrous activity of tropical Menz sheep as affected by plane of nutrition.

Forty-eight mature Ethiopian Menz ewes were used to investigate the effect of nutrition on oestrous and ovarian activity in tropical sheep. A control group was fed on hay alone and a high nutrition group received an additional 400 g per ewe per d of a concentrate feed providing 263 g crude protein/kg dry matter and 10.5 MJ metabolisable energy/kg dry matter. Half the ewes in each group interacted with harnessed vasectomized rams to detect oestrus, which was also verified by weekly plasma progesterone assays. Ram presence did not depress feed intake or liveweight gain (P > 0.05). The mean percentage of ewes showing oestrus at least once a month was very high (95%) and there was a marked reduction in sexual activity from June to September, the wet season. Only 79% of ewes cycled in August and the number of heats per ewe per month dropped to 1.3 during this wet season in contrast to 1.9 the rest of year. Ewes came into oestrus 21 times (range 18-23) a year with no significant effect of level of nutrition. Mean cycle duration was 17.9 +/- 8.7 d; 22% of cycles were short (< or = 13 d), 56% normal (14-19 d), 11% long (20-26 d), 8% silent or missed (27-40 d) and 3% represented anoestrus (> or = 40 d) with no major difference due to nutrition level. Individual animal progesterone profiles revealed that ewes failing to show oestrus had experienced increased silent ovulations. Forty percent of undetected heats were from the same animals. We concluded that, although Menz ewes are year-round breeders, they experience an apparent reduction in sexual activity from June to September, which appears to be independent of the level of nutrition, but might influence their breeding activity and flock production.

Factors affecting morbidity and mortality on-farm and on-station in the Ethiopian highland sheep.

Factors affecting morbidity and mortality of the Ethiopian highland sheep were studied both on-farm and on-station at Debre Berhan between 1989 and 1990. Primary causes of infectious origin resulted in high proportional morbidity (88.4% on-farm) and mortality (72.9% on-farm and 71.8% on-station) rates. Nutritional and managemental factors were also responsible for mortalities in lambs. The most frequent secondary causes of morbidity and/or mortality were ectoparasites and nasal myiasis. Health management interventions on-station were not high enough to produce performance improvements above the on-farm levels. However, the occurrence of gastrointestinal parasites significantly (P < 0.05) differed between the two management systems. The frequency of some of the major causes of morbidity and mortality such as pneumonia, fasciolasis and enteritis were significantly (P < 0.01) affected by season and age of an animal. In order to alleviate the major health constraints identified in this study, a proper health management intervention involving vaccination, strategic anthelmintic treatment and feeding management are suggested.

[Management of reproduction in large dairy herds under Moroccan conditions. III. Resumption of heat and anestrus after natural insemination]. / Conduite de la reproduction en grands troupeaux laitiers dans les conditions marocaines. III. Reprise des chaleurs et anoestrus post-insémination naturelle.

This study aims at determining both the accuracy and the rate of heat detection together with the so-called post-insemination anoestrus incidence in four Moroccan dairy herds under natural or semi-hand mating insemination. 369 females (cows and heifers) were involved from 4 large dairy units in which a herd fertility survey took place on a weekly basis. Heat detection was performed several times a day by the herdsman. Blood was sampled for plasma progesterone (P) determination on the oestrus and the mating day, on day 12 later as well as on day 21 after mating. Accuracy (A) was defined as the ratio of correct oestrus on detected oestrus during the mating days. Heat detection rate (R) was defined as the ratio of oestrus detected on oestrus expected, according to the P values 21 days after mating when the females were confirmed to be cycling. Post-insemination incidence was the complementary ratio to the latter. In the Moroccan dairy unit conditions, A = 91 p. 100, and R = 49 p. 100, the post-insemination anoestrus incidence was therefore just over 50 per cent. The distribution of the non-in-heat but mated females (9 per cent) allows two roughly equal sub-populations to be distinguished: those mated in mid-luteal phase and those with a 1-2 day overlap between the follicular phase and the oestrus. Finally the high incidence of post-insemination anoestrus demonstrates the inadequacy of heat detection for pregnancy diagnosis even under natural or semi-hand mating conditions.(ABSTRACT TRUNCATED AT 250 WORDS)

Natural and induced ovulation rate in prolific and non-prolific breeds of sheep in Ireland, Morocco and New Zealand.

Ovulation rate, in mixed-age groups of prolific and non-prolific ewe breed types, after administration of a range of doses of PMSG (0, 375, 750 and 1500 i.u.) during the follicular phase of the oestrous cycle, were compared in Ireland, Morocco and New Zealand. The ewes in Ireland and Morocco were from the Finnish Landrace and Galway, and D'Man and Timhadite breeds, respectively. In New Zealand Booroola Merino x Romney ewes which had been previously identified as heterozygous carriers (F+) of the Booroola high fecundity gene and purebred Romneys were used to represent the prolific and non-prolific genotypes respectively; in addition a group of Booroola Merino x Romney non-carriers (++) of the major gene were also included for comparison. Ovulation rate at the oestrus which preceded stimulation with PMSG was also measured in all animals. In all 3 locations the ewes of the prolific genotype had a greater ovulation rate after PMSG stimulation than did the non-prolific controls. However, this association between prolificacy and response to PMSG was removed when ovulation rate after PMSG was transformed by dividing by the ovulation rate observed before PMSG administration. Despite the differences in the genetic basis of their high prolificacy the pattern of response to PMSG over the range of dosages used was similar in Finnish Landrace, D'Man and Booroola Merino x Romney (F+) ewes and all breeds had means of about 10 ovulations in response to 1500 i.u. PMSG. Amongst the non-prolific breeds, the Timhadite was the most responsive to PMSG although it had the lowest natural ovulation rate.(ABSTRACT TRUNCATED AT 250 WORDS)

Ovarian follicular growth during the oestrous cycle in two breeds of ewes of different ovulation rate, the D'Man and the Timahdite.

The population of growing follicles of diameter greater than 60 micron was studied in 24 D'Man and 24 Timahdite ewes aged 2-2.5 years. The ovaries of each ewe were removed on Days 1, 2, 3, 4, 5, 7, 9, 11, 13, 15 or 17 of the oestrous cycle. Two ewes from each breed were ovariectomized. The mean ovulation rate was 2.9 in D'Man and 1.1 in Timahdite ewes and the mean numbers of normal follicles were 276 and 230 respectively. The distribution of the various sizes of follicles did not differ significantly between the two breeds. However, the number of follicles of diameter 118 to 462 micron (follicles beginning to develop an antrum) and the number of follicles of diameter greater than 1285 micron (large follicles possessing an antrum) were significantly greater in the D'Man than in the Timahdite ewes (136 and 106, and 7.1 and 4.5, respectively). The mean number of atretic follicles was similar for the two breeds (13.3 in the D'Man; 12.2 in the Timahdite), but in the D'Man there was a lower rate of atresia (54.9 compared with 66.7%) for follicles of 1084-2141 micron diameter. During the first days of the cycle there was a significant decrease in both breeds in the number of follicles of 60-118 micron diameter. During this same period there was a significant decline in the number of follicles of diameter 119 to 462 micron but in the D'Man ewes only. Therefore, the higher ovulation rate of the D'Man breed is due to the greater number of those follicles from which ovulatory follicles are recruited.

Circulating concentrations of oxytocin during pregnancy in ewes.

Oxytocin and progesterone were measured radioimmunologically during a control cycle, early pregnancy and during several time courses until term in 4 ewes of a local Maroccan breed of sheep. Oxytocin concentrations increased in a similar matter after day 3-4 of the control cycle or after mating and decreased on days 13-15 of early pregnancy about 2 days earlier than during the oestrous cycle. After days 18-19 of pregnancy oxytocin concentrations remained low until term at concentrations as observed during the non-luteal phase of the oestrous cycle. Contrary progesterone concentrations remained high throughout gestation. Maternal recognition of pregnancy seems to have only a slight effect on the secretion pattern of oxytocin for few days after day 12. The results indicate a similar unknown mechanism during the cycle and early pregnancy for the vanishing oxytocin secretion and perhaps synthesis.

Plasma gonadotrophin concentrations during the oestrous cycle and after ovariectomy in two breeds of sheep with low and high fecundity.

LH and FSH concentrations were measured during the oestrous cycle in two local Moroccan breeds of sheep with low (Timahdite: 1 CL/cycle) and high (D'man: 3 CL/cycle) ovulation rates. Twenty ewes were used from each breed and blood was collected at 3- or 6-h intervals from 5-4 days before oestrus up to Day 14 of the new cycle, when 4 D'man and 4 Timahdite ewes were ovariectomized. After surgery, blood sampling was continued at 6-h intervals for 2 weeks. (1) The mean basal concentration of LH, the maximum value of the preovulatory LH surge and the area under the curve were significantly higher (P less than 0.05) in Timahdite than in D'man ewes. (2) The pattern of FSH in each breed showed no clear basal level but a periodic succession of peaks with variable amplitudes. The first and highest peak corresponded with the preovulatory LH surge. The 2nd peak followed immediately after the first peak and reached its maximum 24-30 h later. The 3rd peak was flatter and occurred around Day 6 of the cycle. The 4th peak was observed around Day 10 of the cycle and showed the lowest amplitude. The 5th and last peak occurred 66-87 h before the next preovulatory surge. (3) FSH concentrations were higher in the prolific D'man than in Timahdite ewes around the time of oestrus (pro-oestrous peak, preovulatory surge and the 2nd peak). The drop in FSH concentrations observed in D'man ewes before the preovulatory surge was more pronounced and started later.(ABSTRACT TRUNCATED AT 250 WORDS)

Oxytocin concentrations in peripheral blood during the oestrous cycle and after ovariectomy in two breeds of sheep with low and high fecundity.

Oxytocin was measured radioimmunologically during the oestrous cycle in six ewes of each of two local Moroccan breeds of sheep. Concentrations in both breeds approached the lower limit of the assay (3 pg/ml) from 2 days before oestrus, throughout heat and ovulation until day 2 of the cycle. Oxytocin concentrations then increased in both breeds, the resulting highest levels on days 5-7 were, on average, between 30 and 60 pg/ml in the D'man sheep and 13-31 pg/ml in the Timhadite breed. Oxytocin levels then decreased to about 7 pg/ml in the D'man and about 4-5 pg/ml in the Timhadite breed on days 14-15. After ovariectomy oxytocin concentrations remained at about the limit of detection for a further 19-20 days in both breeds.

[Some parameters in reproduction of a Maroccain sheep breed (race d'Man) (author's transl)]. / Einige Parameter zur Reproduktion einer marokkanischen Schafrasse (race d'Man).

The importance of the sheep in Marocco was shown with help of statistical data. As there exist very few scientific work on sheep reproduction in this country, we began to work on local breeds with the race d'Man. The breed is asaisonal and is able to lamb 2 times within 13 months, with mostly 2 or more youngs (1,8 lambs per partum). The delay of gestation was found with 150 days, the duration of a cycle 17 days. The libido shown by the rams is violent. They easily accepted an other male as phantome for the collection of sperm with the easily accepted artificial vagina. The gonads are ovoid formed and are early developed. Remarkable is the tail of the epididymis which is covered in a pocketlike formed structure of the distal scrotum. Its volume is remarkable. Concerning the characteristics of the sperm there is no difference with other breeds. Therefore the conclusion seems reasonable that this apparent development of the epididmymis tail is an organ for thermoregulation for the sperm as the breeds origin are the oasis of the Sahara. The early onset of puberty as well as the violent sexual interest and the high rate of reproduction and asaisonal behavior could be a reference to a "primitive breed".