An evaluation of reproductive performance of horro cattle in Ethiopia

[摘要] English: A study consisting of 2 phases was undertaken to evaluate the reproductiveperformance in female and male Horro (Bos indicus) cattle at the BakoAgricultural Research Center, Ethiopia. In the first part of the study the femalereproductive indicators such as age and weight at puberty, age at firstconception and first calving, post partum anoestrous interval, post partumperiod, intercalving period, growth from birth to 24 months of age, abortion rateas well as the herd mortality rate were evaluated using herd records collectedbetween 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, theseasonal changes in bull semen, testicular characteristics and testosteroneprofiles were recorded in tests conducted between February 2001 and January2002 at the same center. General linear model (GLM) procedures of SAS(SAS, 1994) were used to analyse the data. The least square means wereseparated using Duncan's multiple range test. The overall least square meanage and weight at puberty, 1st conception and I calving for heifers was 39.4months, 202.9 kg, 50.1. months, 226.7 kg, 58.7 months and 259.2 kgrespectively. The age at puberty, l conception and 1st calving was notaffected by season of birth and birth weight. The age at 1st conception and 1stcalving significantly (P<0.05) affected the year of birth. Differences wererecorded for age at 1st conception and 1st calving between the years monitored.The mean weight at puberty, conception and calving rates were not affected bythe season of birth and birth weight. The year of birth did not affect the weightat puberty, but significantly (P<0.05) affected the weight at I conception and1st calving. Differences were recorded for body weight between theobservation years for weight at 1st conception and 1st calving. The overall leastsquare means for the post partum anoestrous interval and post partum periodwere 77.2 and 117.5 days respectively. The season (P<0.05) and year ofcalving (P<0.01) significantly affected the post partum anoestrous interval.The shortest post partum anoestrous interval (72.5 ± 3.4 days) was recordedduring 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 wererecorded between years for the post partum anoestrous interval from 1977 to2001. The season of calving, calf birth weight and sex of the calf did not affectthe 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 1977to 2001. Sex of the calf significantly (P<0.05) affected the post partumanoestrous interval with dams bearing male calves demons,trating a longerperiod. The overall least square mean intercalving period and gestation lengthrecorded, were 472 and 283 days respectively. Intercalving period was notaffected 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 affectedthe intercalving period. Differences were recorded between years forintercalving period. The longest intercalving period (503.7 ± 8.8 days) wasrecorded 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) forgestation length. Sex of the calf significantly (P<0.05) affected gestationlength with cows bearing bull calves having a longer gestation period.Post partum live weight changes and serum progesterone concentrations in cowsindicated that cows that calved during the dry season lost more weight. Fromthe total number of cows that calved during the dry season only 20% of thembecame pregnant within 90 days post partum, compared to 60% for cows thatcalved during the wet season. The overall least square mean serumprogesterone (dry and wet season) concentration was 6.1 ng/ml and this wassignificantly (P<0.01) affected by season of calving and the cow body weight atcalving. The mean progesterone level during the wet season (May toSeptember) 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 monthof 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 birthweight 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 weregenerally 11.6% heavier than their female counterparts at birth. Differences onbirth weight were recorded between years. The 3 and 6 month weights werenot 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 thewet season recorded the highest body weight at 3 months of age, compared tothose born in the dry season. Differences were recorded between years from1977 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 agescompared to their male counterparts. Heavier calves at birth and those born inthe 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 monthsweight from 1977 to 2000.The pre-weaning ADG was not influenced by the sex of the calf or the season ofbirth, but was influenced by the year of birth. Differences were recordedbetween years in pre-weaning ADG. Post weaning ADG was not affected bysex of the calf, but season of birth significantly (p< 0.05) affected post weaningADG. Calves born in the wet season recording the highest post weaning ADG.In the second part of this study the male reproductive performance and sexualcharacteristics of Horro (Bos indicus) (n=32) bulls, with an average initial bodyweight of 211 kg and age of approximately 6 years were evaluated. The bullswere divided into two treatment groups. One group was given a supplementaryconcentrate at a rate of 1.5 kg/day and the second group served as the controland received no supplementation. The observation period lasted for 50 weeks.Semen was collected every two weeks by means of electric stimulation with theaid of an electro-ejaculator. General linear model (GLM) procedures of SAS(SAS, 1994) were used to analyse the data. Semen and testicularcharacteristics, body weight and serum testosterone concentration were recordedduring this period. The following semen parameters were evaluated: semenvolume, semen color, mass motility, sperm concentration, percentage livesperm, percentage abnormal sperm and semen pH. Other male sexualcharacteristics evaluated were serum testosterone concentration, scrotalcircumference, testis volume, scrotal skin thickness and libido as well as bodyweight every second week, concurrent with semen collection.In general the bulls from the supplemented group tended to have higher qualitysemen characteristics. Three colour types of ejaculates were observed, namely,creamy, milky and watery. Semen from the supplemented group tended tohave a more creamy colour, when compared to the non-supplemented group.There was a general tendency for the bulls from the supplemented group tomaintain 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 tothat of the bulls in the non-supplemented group. The percentage of abnormalsperm (total abnormalities, head, mid-piece and tail) remained lower in thesupplemented group than the non-supplemented group. Semen pH remainedconstant around 6.8 for most of the observation period. Libido score for bothsupplemented and control group remained constant (1.5 ± 0.3 to 3.8 ± 0.2 and1.4 ± 0.2 to 3.8 ± 0.2, respectively). The scrotal circumference measuredduring the trial period for the supplemented and control group was 28.8 ± 0.5 to32.8 ± 0.2 cm and 28.9 ± 0.5 to 32.9 ± 0.2 cm respectively. Scrotalcircumferences were not influenced by nutritional supplementation. Scrotalskin 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 thescrotum increased. Testis length increased similarly in both treatment groups.A minimal increase in testis length was recorded over the 50 week period. Thetestis volume in both supplemented and control group increased gradually fromthe onset of the trial (week 0) to the end of the observation period (week 50).Significant differences were observed between the supplemented and controlgroup regarding testis volume during certain weeks only. The mean bodyweight in both groups (supplemented and control) increased steadily from theonset of the trial to the end of the experiment. Bulls from the supplementedgroup gained on average more compared to the non-supplemented group.Serum testosterone levels of bulls collected during the dry season (October toApril) were higher (911 ± 35.3 ng/dl) than during the wet season (May toSeptember) (768.6 ± 30.9 ng/dl). Although not significant, bulls from thesupplemented group recorded higher serum testosterone levels.Overall, the productive and reproductive performance of Horro cattle (femalereproductive and growth) at Bako Research Center has not improved much overthe years. Inadequate nutrition and poor management in the herd have beenimplicated. It is suggested that efforts need to be made to improve themanagement. The introduction of a limited breeding season to induce earlysummer, calving is warranted. Calving during the summer (wet) season hasadvantages in both the reproductive and productive performance of the cows.From the bull reproduction evaluation, it can be concluded that the semen andsexual characteristics observed during the trial are markedly influenced by thetime (season) in which semen was collected. In general, the animals on thesupplemented group tended to record higher serum testosterone levels and bettersemen and testicular characteristics compared to the control animals. It wouldseem that supplementation of breeding bulls is advantageous to their fertility.Further studies on the reproductive and productive characteristics of the Horrobreed were recommended.

[发布机构] University of the Free State