An evaluation of reproductive performance of Horro cattle in Ethiopia

English: A study consisting of 2 phases was undertaken to evaluate the reproductive performance in female and male Horro (Bos indicus) cattle at the Bako Agricultural Research Center, Ethiopia. In the first part of the study the female reproductive indicators such as age and weight at puberty, age at first conception and first calving, post partum anoestrous interval, post partum period, intercalving period, growth from birth to 24 months of age, abortion rate as well as the herd mortality rate were evaluated using herd records collected between 1974 and 2001 at the Research Center. In the second part of the study, post partum live weight changes of cows, their serum progesterone profiles, the seasonal changes in bull semen, testicular characteristics and testosterone profiles were recorded in tests conducted between February 2001 and January 2002 at the same center. General linear model (GLM) procedures of SAS (SAS, 1994) were used to analyse the data. The least square means were separated using Duncan's multiple range test. The overall least square mean age and weight at puberty, 1st conception and I" calving for heifers was 39.4 months, 202.9 kg, 50.1. months, 226.7 kg, 58.7 months and 259.2 kg respectively. The age at puberty, l" conception and 1st calving was not affected by season of birth and birth weight. The age at 1st conception and 1st calving significantly (P<0.05) affected the year of birth. Differences were recorded for age at 1st conception and 1st calving between the years monitored. The mean weight at puberty, conception and calving rates were not affected by the season of birth and birth weight. The year of birth did not affect the weight at puberty, but significantly (P<0.05) affected the weight at I" conception and 1st calving. Differences were recorded for body weight between the observation years for weight at 1st conception and 1st calving. The overall least square means for the post partum anoestrous interval and post partum period were 77.2 and 117.5 days respectively. The season (P<0.05) and year of calving (P<0.01) significantly affected the post partum anoestrous interval. The shortest post partum anoestrous interval (72.5 ± 3.4 days) was recorded during the wet season (May to September), while the longest (81.7 ± 2.9 days) period was recorded in the dry season (October to April). Differences were recorded between years for the post partum anoestrous interval from 1977 to 2001. The season of calving, calf birth weight and sex of the calf did not affect the post partum period, but year of calving (P<0.01) played a significant role. Differences were recorded between years for the post partum period from 1977 to 2001. Sex of the calf significantly (P<0.05) affected the post partum anoestrous interval with dams bearing male calves demons,trating a longer period. The overall least square mean intercalving period and gestation length recorded, were 472 and 283 days respectively. Intercalving period was not affected by the season of calving, sex of the calf and calf birth weight. However the year of calving (P<0.01) and parity (P<0.05) significantly affected the intercalving period. Differences were recorded between years for intercalving period. The longest intercalving period (503.7 ± 8.8 days) was recorded during the second parity, compared to 3rd, 4th, 5th and 6th parities (469.0 ± 9.7, 449.2 ± 11.2, 468.6 ± 13.3 and 456.8 ± 16.4 days, respectively). Significant differences were recorded between years regarding gestation length, but no significant differences were observed between season (wet or dry) for gestation length. Sex of the calf significantly (P<0.05) affected gestation length with cows bearing bull calves having a longer gestation period. Post partum live weight changes and serum progesterone concentrations in cows indicated that cows that calved during the dry season lost more weight. From the total number of cows that calved during the dry season only 20% of them became pregnant within 90 days post partum, compared to 60% for cows that calved during the wet season. The overall least square mean serum progesterone (dry and wet season) concentration was 6.1 ng/ml and this was significantly (P<0.01) affected by season of calving and the cow body weight at calving. The mean progesterone level during the wet season (May to September) was higher (8.5 ± 0.8 ng/ml) and that during the dry season (October to April) was lower (2.8 ng/ml) . For the progeny, the overall least square mean birth, 3, 6, 12, 18 and 24 month of age body weights, pre- and post weaning ADG for Horro cattle were 18.4, 48.9, 68, 87.5, 109.7 kg, 275 g/day and 130.9 g/day, respectively. The birth weight of the calves was not affected by season of birth, but sex of the calf (P<0.01) and year of birth (P<0.05) affected birth weight. Male calves were generally 11.6% heavier than their female counterparts at birth. Differences on birth weight were recorded between years. The 3 and 6 month weights were not affected by the sex of the calf, but season (P<0.05) and year of birth (P<0.01) significantly affected body weight at 3 months. Calves born in the wet season recorded the highest body weight at 3 months of age, compared to those born in the dry season. Differences were recorded between years from 1977 to 2001 regarding the weight at 3 months of age. The body weights at 12, 18 and 24 months were significantly (P<0.05) affected by the sex of the calf, season of birth and calf birth weight. Female calves were heavier at these ages compared to their male counterparts. Heavier calves at birth and those born in the wet season recorded the highest weights at 12, 18 and 24 months of age. Differences were recorded between the survey years in 12 and 18 months weight from 1977 to 2000. The pre-weaning ADG was not influenced by the sex of the calf or the season of birth, but was influenced by the year of birth. Differences were recorded between years in pre-weaning ADG. Post weaning ADG was not affected by sex of the calf, but season of birth significantly (p< 0.05) affected post weaning ADG. Calves born in the wet season recording the highest post weaning ADG. In the second part of this study the male reproductive performance and sexual characteristics of Horro (Bos indicus) (n=32) bulls, with an average initial body weight of 211 kg and age of approximately 6 years were evaluated. The bulls were divided into two treatment groups. One group was given a supplementary concentrate at a rate of 1.5 kg/day and the second group served as the control and received no supplementation. The observation period lasted for 50 weeks. Semen was collected every two weeks by means of electric stimulation with the aid of an electro-ejaculator. General linear model (GLM) procedures of SAS (SAS, 1994) were used to analyse the data. Semen and testicular characteristics, body weight and serum testosterone concentration were recorded during this period. The following semen parameters were evaluated: semen volume, semen color, mass motility, sperm concentration, percentage live sperm, percentage abnormal sperm and semen pH. Other male sexual characteristics evaluated were serum testosterone concentration, scrotal circumference, testis volume, scrotal skin thickness and libido as well as body weight every second week, concurrent with semen collection. In general the bulls from the supplemented group tended to have higher quality semen characteristics. Three colour types of ejaculates were observed, namely, creamy, milky and watery. Semen from the supplemented group tended to have a more creamy colour, when compared to the non-supplemented group. There was a general tendency for the bulls from the supplemented group to maintain a higher sperm motility score during the trial period - ranging from 2.6 ± 0.2 to 3.6 ± 0.2, compared to the 1.7 ± 0.2 to 3.0 ± 0.3 of the control group. Sperm concentration in the supplemented group remained higher compared to that of the bulls in the non-supplemented group. The percentage of abnormal sperm (total abnormalities, head, mid-piece and tail) remained lower in the supplemented group than the non-supplemented group. Semen pH remained constant around 6.8 for most of the observation period. Libido score for both supplemented and control group remained constant (1.5 ± 0.3 to 3.8 ± 0.2 and 1.4 ± 0.2 to 3.8 ± 0.2, respectively). The scrotal circumference measured during the trial period for the supplemented and control group was 28.8 ± 0.5 to 32.8 ± 0.2 cm and 28.9 ± 0.5 to 32.9 ± 0.2 cm respectively. Scrotal circumferences were not influenced by nutritional supplementation. Scrotal skin thickness was also not influenced by nutritional supplementation, but time (weeks) and the time x treatment interaction influenced scrotal skin thickness. As the trial progressed, the bulls increased in age and so the fat deposition in the scrotum increased. Testis length increased similarly in both treatment groups. A minimal increase in testis length was recorded over the 50 week period. The testis volume in both supplemented and control group increased gradually from the onset of the trial (week 0) to the end of the observation period (week 50). Significant differences were observed between the supplemented and control group regarding testis volume during certain weeks only. The mean body weight in both groups (supplemented and control) increased steadily from the onset of the trial to the end of the experiment. Bulls from the supplemented group gained on average more compared to the non-supplemented group. Serum testosterone levels of bulls collected during the dry season (October to April) were higher (911 ± 35.3 ng/dl) than during the wet season (May to September) (768.6 ± 30.9 ng/dl). Although not significant, bulls from the supplemented group recorded higher serum testosterone levels. Overall, the productive and reproductive performance of Horro cattle (female reproductive and growth) at Bako Research Center has not improved much over the years. Inadequate nutrition and poor management in the herd have been implicated. It is suggested that efforts need to be made to improve the management. The introduction of a limited breeding season to induce early summer, calving is warranted. Calving during the summer (wet) season has advantages in both the reproductive and productive performance of the cows. From the bull reproduction evaluation, it can be concluded that the semen and sexual characteristics observed during the trial are markedly influenced by the time (season) in which semen was collected. In general, the animals on the supplemented group tended to record higher serum testosterone levels and better semen and testicular characteristics compared to the control animals. It would seem that supplementation of breeding bulls is advantageous to their fertility. Further studies on the reproductive and productive characteristics of the Horro breed were recommended.