Azage Tegegne

Fertility of Bos indicus and Bos indicus × Bos taurus crossbreed cattle after estrus synchronization

Ninety-five cows (79 Boran and 16 Boran-Brahman crossbreeds) and 107 heifers (55 Boran and 52 Boran x Friesian F1 crossbreeds) were used to determine estrus response, estrus response interval and pregnancy rate following synchronization with prostaglandin (PGF(2)alpha), a progesterone-releasing intravaginal device (PRID) and Synchro-mate B (SMB). The proportion of cattle responding to synchronization treatment was 62.5, 43.5 and 57.7% for cows and 85.7, 68.0 and 81.5% for heifers using PGF(2)alpha, PRID and SMB, respectively. The overall mean response was 59 and 81.8% for cows and heifers, respectively. The estrus response of the control animals over a 45-d breeding period was 72.7 and 90% for cows and heifers, respectively. The estrus response interval for cows was 31.8, 22.1 and 18.0 h and it was 51.1, 38.0 and 21.6 h for heifers with PGF(2)alpha, PRID and SMB treatment, respectively. Mean pregnancy rate for cows was 50.0, 34.8, 46.2 and 68.8% and for heifers it was 60.7, 40.0, 55.6 and 77.8% in the PGF(2)alpha, PRID, SMB and control groups, respectively. Based on these findings, it was concluded that both PGF(2)alpha and SMB produce a satisfactory estrus response and pregnancy rate in the cattle studied.

Effects of supplementary feeding and suckling intensity on postpartum reproductive performance of small East African Zebu cows

Small East African Zebu cows (n = 120) which calved during the dry season were used to determine the effects of postpartum nutritional supplementation and suckling intensity on body weight, body condition score, reproductive performance and on calf mortality and preweaning growth performance. Cows were allocated based on calving body weight to either receive a supplementary feed of molasses blocks containing 10% urea or to serve as controls and to be grazed only. Within nutritional groups, cows were further assigned either to continuous suckling or to restricted suckling twice daily. Intact bulls were introduced 21 days after the first cow had calved, and data were collected for 8 months. Calving body weight and body condition score of dams ranged from 186 to 192 kg and from 3.8 to 4.2 and did not differ among the treatment groups. Supplementary feeding significantly (P<0.05) reduced calf mortality from 40 to 20%, while restricted suckling reduced mortality by 13% from 36 to 23%. Body weight and body condition score did not vary between groups during the supplementation period. Over the 8-month period, 65% of supplemented and 53% of control cows exhibited estrus (P>0.05). A significantly (P<0.05) karger percentage of restricted suckled cows showed estrus than of continuously suckled cows (74 vs 42%). The postpartum estrus interval was shorter by 54 days in supplemented than in control cows and by 13 days in restricted than in continuously suckled cows. The pregnancy rate was higher in supplemented than in control cows (37 vs 33%; P>0.05) and in restricted than in continuously suckled (46 vs 22%; P>0.05) cows.

Effects of dry season nutritional supplementation on growth, onset of puberty and subsequent fertility in Boran and Boran × Friesian heifers in Ethiopia

Shortly after weaning at 8 months of age, 43 Boran and 46 Boran x Friesian crossbred heifers were randomly divided to either receive a supplementary feed containing 16% crude protein during the dry season or to serve as controls. Heifers were examined monthly, and data on body weight, wither height and body condition score were recorded. Ovarian size and structures were determined per rectum and heifers were kept under continuous observation for standing estrus. Blood samples were collected at 10-day intervals every month for determination of plasma progesterone levels. All heifers were exposed to intact bulls for 4 months after they attained 18 months of age. Average daily weight gain to puberty was significantly (P<0.01) higher in heifers given supplementation than in the controls (360 vs 326 g/day). The average daily weight gain in Boran heifers (296 g/day) was significantly (P<0.01) lower than in crossbred (392 g/day) heifers. Mean age at puberty differed significantly (P<0.001) between heifers given supplementation (573 days) and the controls (627 days). Boran heifers attained puberty at a significantly later age (660 vs 540 days; P<0.001) than crossbred heifers. Body weight at puberty did not differ between supplemented and control heifers (226 vs 222 kg); while the difference between Boran and crossbred heifers was significant (216 vs 232 kg; P<0.01). Pelvic size and body condition score were not influenced by supplementation but differed significantly between genotypes. Pregnancy rate after 4 months of breeding was higher in supplemented (79%) than in control (64%) heifers. Boran heifers had a significantly (P<0.001) lower pregnancy rate than crossbred heifers (52 vs 91%). Mean age and body weight at conception were not affected by supplementation but differed significantly (P<0.05) between genotypes. The results indicate that prepubertal supplementary feeding during the dry season increased growth rate, reduced age at puberty and improved fertility in both Boran and Boran x Friesian heifers.

Gonadal and extragonadal sperm reserves and testicular histometric characteristics in Zebu and crossbred bulls: Effect of dry season nutritional supplementation

Abstract A total of 64 bull calves, composed of 27 Boran and 37 Boran X Friesian, were weaned at 6 months of age and divided into supplement or control groups within breed. All bulls were kept in one paddock and grazed on natural pasture. Supplement groups received 1.5 kg per head day−1 of a diet containing 16% crude protein and 8 MJ kg−1 dry matter for two dry seasons until castrated at 21 months of age. Testes weight was heavier in supplemented than in control bulls (285 vs. 242 g) and in Boran X Friesian than in Boran bulls (300 vs. 215 g). Epididymal weight differed between supplemented and control bulls (30.4 vs. 25.1 g) and between Boran and Boran X Friesian (22.1 vs. 31.9 g) bulls. Supplemented bulls had 27% greater daily sperm production (2.65 × 109vs.2.08 × 109) and 36% greater epididymal sperm reserves (4.05 × 109vs.2.99 × 109) than control bulls. Sperm reserves in the caput and cauda segments were also greater in supplemented than in control bulls. Boran X Friesian bulls had 32% greater daily sperm production (2.63 × 109 vs. 1.99 × 109) than Boran bulls, but epididymal sperm reserves did not differ between the two breeds. Seminiferous tubule diameter was larger by 9% in supplemented than in control and by 14% in Boran X Friesian than in Boran bulls. Supplementary feeding to young Boran and Boran X Friesian bulls during dry seasons resulted in heavier testes and epididymis weights, larger seminiferous tubule diameter and higher gonadal and extragonadal sperm reserves.

A quantitative histological study of testicular and epididymal development in Boran and Boran × Friesian bulls in Ethiopia

Quantitative histological techniques were used to characterize the pattern of testicular and epididymal development in 42 Boran and 49 Boran x Friesian bulls aged between 6 and 23 mo. Bulls were divided into five age groups having four-month intervals. Between 6 and 23 mo of age, body weight increased from 124 to 293 kg and 179 to 267 kg (P<0.01) in Boran and Boran x Friesian bulls, respectively. Scrotal circumference measurements increased from 6 to 23 mo by 10.2 and 8.9 cm in Boran and Boran x Friesian bulls. Paired testes weight increased significantly (P<0.001) over the same period from 29 to 304 g and 59 to 291 g in Boran and Boran x Friesian bulls, respectively. Both caput and cauda epididymal segment weights also increased significantly (P<0.001) with age. There were significant (P<0.05) genotype differences in seminiferous tubule diameter, which increased by 137 and 90 microm with increasing age in Boran and Boran x Friesian bulls, respectively. Patent seminiferous tubules were first observed at 206 and 188 d of age in Boran and Boran x Friesian bulls, respectively. The appearance of elongated spermatids and spermatozoa in the seminiferous tubules and epididymal tubules occurred at later ages in Boran than in Boran x Friesian bulls.

Superovulatory response, embryo recovery and progesterone secretion in Boran (Bos indicus) cows after treatment with either Pergovet or Pluset

Boran (Bos indicus) cows (n = 24) were allocated, based on body weight, to be treated with either a human menopausal gonadotropin (Pergovet) at doses of 1050 or 1350 IU or a porcine gonadotropin (Pluset) at doses of 500 or 1000 IU. The cows were arranged in a balanced crossover design, and each cow was superovulated 3 consecutive times, which resulted in a total of 72 superovulations. Superovulatory treatment started on Day 10±1 of the estrous cycle, and cows were treated for 5 consecutive days. Estrus was induced with PGF2α (2 ml, im) at 72 h after initiation of treatment. Cows were inseminated at 12 and 24 h after the onset of estrus using 2 doses of semen each from a Friesian bull. Daily blood samples were collected from the beginning of superovulatory treatment to the onset of estrus for determination of progesterone concentrations. The mean (±SEM) estrus response interval after PGF2α and estrus duration were 33.1±4.1 and 9.3±0.5 h, respectively, and did not vary between treatment groups. Similarly, the mean numbers of palpable corpora lutea and follicular cysts were 7.8±0.7 and 3.0±0.4, with no treatment effect. The number of superovulations which yielded embryos/ova was 50 (69.4%) and was higher (P>0.05) in cows treated with Pergovet (75%) than with Pluset (63.9%). The mean number of embryos/ova recovered per superovulation was not affected by treatment and averaged 4.0±0.4, with a range from 3.2±0.9 to 4.6±1.0 in the 4 treatment groups. There was no treatment effect on the mean number of transferable embryos per superovulation, which averaged 3.1±0.3. The mean numbers of embryos/ova and transferable embryos per embryo yielding superovulation were 5.6±0.4 and 4.3±0.4, respectively. Return to natural estrus after the induced estrus averaged 43.3±6.1 d (range 37.2±11.8 to 56.4±12.2 d), with no apparent treatment effect. The mean numbers of embryos/ova, transferable embryos and interval to return to natural estrus did not vary between consecutive superovulations. Mean plasma progesterone concentrations dropped from 7.6±0.3 ng/ml on the first day of superovulatory treatment to 1.3±0.1 ng/ml on the day of induced estrus and did not differ between treatment groups and between cows which yielded different numbers of embryos/ova. Progesterone concentration on the day of estrus was negatively correlated with the number of embryos/ova (−0.29) and the number of transferable embryos (−0.26), suggesting that progesterone concentration on the day of induced estrus can help to predict embryo yield and quality in Boran cows. It was concluded that both Pergovet and Pluset can be used to superovulate Boran cows with no residual effect of repeated treatment on embryo yield and return to natural estrus. However, treatment with Pergovet tended to increase the proportion of cows which yielded embryos. Moreover, Pergovet given at 1050 IU and Pluset at 1000 IU resulted in the production of 19.4 and 39.0% more number of transferable embryos than at 1350 and 500 IU, respectively.

Nutritional influences on growth and onset of puberty in Boran and Boran × Friesian bulls in Ethiopia

Twenty-seven Boran and 37 Boran x Friesian crossbred bulls were weaned at 6 months of age and randomly assigned to either a dry season supplementary feed containing 16% crude protein or control groups. Data were collected on body weight, wither height and scrotal circumference (SC) at monthly intervals. Bulls were also challenged with 100 mug of gonadotropin releasing hormone (GnRH) at 2-month intervals and plasma testosterone responses were determined. Semen was collected at monthly intervals by electroejaculation. Post weaning average daily weight gain was significantly (P<0.001) higher in supplemented than in control groups (302 vs 208 g/day). Scrotal circumference growth rates were also significantly (P<0.001) higher in supplemented than in control bulls (0.38 vs 0.31 mm/day). Bulls fed supplemented diets were younger (430 vs 473 days; P<0.001) and heavier (217 vs 203 kg; P<0.05) and had better semen quality at puberty than the control bulls. There was a trend for larger SC at puberty in supplemented than in control bulls (P=0.06). There were no significant differences in wither height or in testosterone response to GnRH at puberty between supplemented and control bulls. Body and SC growth rates to puberty for Boran and Boran x Friesian bulls were 189 and 321 g/day (P<0.001) and 0.27 and 0.42 mm/day (P<0.01), respectively. Boran bulls were older (513 vs 406 days; P<0.01) and lighter (201 vs 215 kg; P<0.05), and had smaller SC (23.9 vs 26 cm; P<0.01) at puberty than Boran x Friesian bulls. Testosterone responses to GnRH increased (P<0.001) with age and were significantly higher (P<0.05) in supplemented and in Boran x Friesian bulls than in control and Boran bulls. Wither height, testosterone response to GnRH and semen quality at puberty did not differ between breeds. Dry season supplementation improved growth rate and enhanced sexual development and maturity in both Boran and Boran x Friesian bulls, and would be a useful management strategy for enhancing fertility in bulls in the tropics.

Gonadal and extragonadal sperm reserves in Boran and Boran × Friesian bulls raised on two planes of nutrition in the Highlands of Ethiopia

Gonadal and extragonadal sperm reserves were determined in testicular and epididymal tissues obtained from Boran (n=10) and Boran x Friesian (n=12) bulls fed either a high or low plane nutrition diet for a 1-year period. The bulls were 32 months of age at castration. Mean (+/-SEM) daily body weight gains over a 1-year period were 776+/-34 and 264+/-34 g/day (P<0.001) for bulls on high and low nutrition, and their respective body weights at castration were 458+/-17 and 276+/-17 kg (P<0.01). Mean body weights did not differ between Boran and Boran x Friesian bulls. Mean scrotal circumference measurements were 32.1+/-0.6 and 28.8+/-0.6 cm for the high and low planes of nutrition (P<0.01) and 31.8+/-0.7 and 29.2+/-0.6 cm for the Boran and the Boran x Friesian bulls (P<0.05). Paired testes and epididymal weights averaged 432+/-22 and 313+/-22 g (P<0.01) and 46.3+/-2.0 and 32.5+/-2.0 g (P<0.001) for bulls on the high and low planes of nutrition, respectively. Boran x Friesian bulls had significantly heavier (P<0.05) testes, but epididymal weithts did not differ between breeds. Although daily sperm production per gram was not influenced by either plane of nutrition or breed, daily sperm production differed between high (5.3 x 10(9)) and low nutrition (2.9 x 10(9)) bulls (P<0.001) and between Boran (4.6 x 10(9)) and Boran x Friesian (3.5 x 10(9)) bulls (P<0.01). Extragonadal sperm reserves were significantly higher in high than in low nutrition bulls (13.1 x 10(9) vs 6.9 x 10(9); P<0.001) and in Boran than Boran x Friesian bulls (12.9 x 10(9) vs 7.1 x 10(9); P<0.01). The cauda epididymis contributed 50 to 54% to the total epididymal sperm reserves. It was concluded that the plane of nutrition influenced growth rates and testes and epididymal weights, and it improved gonadal and extragonadal sperm reserves in young Boran and Boran x Friesian bulls.

Genotype differences in gonadal and extragonadal sperm reserves in mature Zebu bulls in Ethiopia

Gonadal and extragonadal sperm reserves were determined in testicular and epididymal tissues obtained from ten Small African Zebu (SEAZ), ten unimproved Borana and nine improved Boran bulls. Bulls were mature and were between 6 and 8 years of age. Mean (±SEM) body weight was 281±5, 329±9 and 524±12 kg for SEAZ, Borana and Boran bulls, respectively, which had mean scrotal circumference (SC) measurements of 28.7±0.5, 30.9±0.7 and 36.4±0.6 cm. Both body weight and SC differed significantly (P<0.01) among the three genotypes. Paired testes and epididymal weights averaged 322.9±18, 359±25 and 582±20 g and 36.7±1.5, 40.9±1.6 and 64.6±2.0 g for SEAZ, Borana and Boran bulls, respectively, and were significantly (P<0.01) larger in Boran bulls than in the other two genotypes. Daily sperm production (DSP) did not differ between SEAZ (3.2 × 109) and Borana (3.5 × 109) bulls. However, Boran bulls had significantly (P<0.01) larger DSP (4.6 × 109) than the other two genotypes. Epididymal sperm reserves (ESR) differed significantly (P<0.01) between the three genotypes, with SEAZ having the least (16.3 × 109) followed by Borana (22.5 × 109) and Boran (26.9 × 109).

Fertility of and × crossbreed cattle after estrus synchronization

Ninety-five cows (79 Boran and 16 Boran-Brahman crossbreeds) and 107 heifers (55 Boran and 52 Boran x Friesian F1 crossbreeds) were used to determine estrus response, estrus response interval and pregnancy rate following synchronization with prostaglandin (PGF(2)alpha), a progesterone-releasing intravaginal device (PRID) and Synchro-mate B (SMB). The proportion of cattle responding to synchronization treatment was 62.5, 43.5 and 57.7% for cows and 85.7, 68.0 and 81.5% for heifers using PGF(2)alpha, PRID and SMB, respectively. The overall mean response was 59 and 81.8% for cows and heifers, respectively. The estrus response of the control animals over a 45-d breeding period was 72.7 and 90% for cows and heifers, respectively. The estrus response interval for cows was 31.8, 22.1 and 18.0 h and it was 51.1, 38.0 and 21.6 h for heifers with PGF(2)alpha, PRID and SMB treatment, respectively. Mean pregnancy rate for cows was 50.0, 34.8, 46.2 and 68.8% and for heifers it was 60.7, 40.0, 55.6 and 77.8% in the PGF(2)alpha, PRID, SMB and control groups, respectively. Based on these findings, it was concluded that both PGF(2)alpha and SMB produce a satisfactory estrus response and pregnancy rate in the cattle studied.