Ovarian follicular dynamics in Nelore breed (Bos indicus) cattle

The most common beef cattle raised in Brazil is the Nelore breed (Bos indicus). Information obtained by ultrasonography on follicular growth in Bos taurus cattle has been accumulating rapidly. However, there are few publications to date on follicular development in Bos indicus breeds. The follicular dynamics in Nelore heifers and cows during natural or prostaglandin (PG)-induced estrous cycle were studied. From the detection of estrus onward, all animals were examined daily by ultrasonography for one (n = 35) or two (n = 10) consecutive estrous cycles. The follicular dynamic in Nelore cattle was characterized by the predominance of 2 follicular waves in the cows (83.3%, n = 18, P < 0.05) and 3 waves in the heifers (64.7%, n = 16, P < 0.05). Most of the cattle observed over 2 consecutive estrous cycles presented the same pattern of follicular waves in the first and second cycle, and only 30% showed variation in the number of waves from one cycle to the other. Most of the follicular parameters analyzed were not affected by PG treatment or age but were altered by follicular waves. Consequently, data on cows and heifers were combined according to the number of follicular waves. The ovulatory follicle was larger than the other dominant follicles (P < 0.05), and the ovulatory wave was shorter than the preceding waves (P < 0.05). The interovulatory interval was longer in animals showing 3 waves than those exhibiting 2 waves (P < 0.05). Maximum diameter of the dominant follicle (around 11 mm) and of the corpus luteum (CL, approximately 17 mm) were smaller than those reported for European breeds. In conclusion, the results demonstrate that although the dominant follicle and corpus luteum are smaller than in European breeds, the follicular dynamics in Nelore cattle were similar to those observed in European breeds and were characterized by 2 or 3 follicular waves for cows and heifers, respectively, during the natural or prostaglandin-induced estrous cycle.     

Trace Element Distribution in Selected Edible Tissues of Zebu (Bos indicus) Cattle Slaughtered at Jimma,SW Ethiopia

The amount of trace elements present in edible bovine tissues is of importance for both animal health and human nutrition. This study presents data on trace element concentrations in semitendinosus and cardiac muscles, livers and kidneys of 60 zebu (Bos indicus) bulls, sampled at Jimma, Ethiopia. From 28 of these bulls, blood samples were also obtained. Deficient levels of copper were found in plasma, livers, kidneys and semitendinosus muscles. Suboptimal selenium concentrations were found in plasma and semitendinosus muscles. Semitendinosus muscles contained high iron concentrations. Trace elements were mainly stored in the liver, except for iron and selenium. Cardiac muscles generally contained higher concentrations of trace elements than semitendinous muscles except for zinc. A strong association was found between liver and kidney concentrations of copper, iron, cobalt and molybdenum. Liver storage was well correlated with storage in semitendinosus muscle for selenium and with cardiac muscle for cobalt and selenium. Plasma concentrations of copper, selenium, cobalt were well related with their respective liver concentrations and for cobalt and selenium, also with cardiac muscle concentrations. The data suggest multiple trace element deficiencies in zebu cattle in South-West Ethiopia, with lowered tissue concentrations as a consequence. Based on the comparison of our data with other literature, trace element concentrations in selected edible tissues of Bos indicus seem quite similar to those in Bos taurus. However, tissue threshold values for deficiency in Bos taurus cattle need to be refined and their applicability for Bos indicus cattle needs to be evaluated.     

MspI Allelic Pattern of Bovine Growth Hormone Gene in Indian Zebu Cattle (Bos indicus) Breeds

The MspI allelic variation in intron III of the bovine growth hormone (bGH) gene was explored using PCR-RFLP in 750 animals belonging to 17 well-recognized breeds of Indian zebu cattle (Bos indicus) reared in different geographic locations of the country. Restriction digestion analysis of a 329-bp PCR fragment of the bGH intron III region with MspI restriction enzyme revealed two alleles (MspI− and MspI+) and two genotypes (−/− and +/−) across the 17 cattle breeds studied. The allelic frequency varied from 0.67 to 0.94 for MspI (−) and from 0.06 to 0.33 for MspI (+) across the 17 breeds, with a combined average frequency of 0.87 and 0.13, respectively. No animal with +/+ genotype was detected across the samples analyzed. The chi-square test showed that the difference in MspI allelic frequency was not significant (p > 0.05), regardless of the geographic origin, coat color, or utility of the cattle breed. The high MspI (−) allele frequencies obtained for Indian zebu cattle in this study are in sharp contrast to those reported for taurine breeds from northern Europe, Mediterranean countries, and America. Findings of this study further substantiate the hypothesis that the MspI (−) allele has an Indian origin.     

Ovarian function in Nelore (Bos taurus indicus) cows after post-ovulation hormonal treatments

Maternal recognition of pregnancy in the cow requires successful signaling by the conceptus to block luteolysis. Conceptus growth and function depend on an optimal uterine environment, regulated by luteal progesterone. The objective of this study was to test strategies to optimize luteal function, as well as prevent a dominant follicle from initiating luteolysis. Nelore (Bos taurus indicus) beef cows (n=40) were submitted to a GnRH/PGF(2alpha)/GnRH protocol. Cows that ovulated from a dominant ovarian follicle (ovulation=Day 0) were allocated to receive: no additional treatment (G(C); n=7); 3000IU of hCG on Day 5 (G(hCG); n=5); 5mg of estradiol-17beta on Day 12 (G(E2); n=6); or 3000IU of hCG on Day 5 and 5mg of estradiol-17beta on Day 12 (G(hCG/E2); n=5). Ultrasonographic imaging of the ovaries, assessment of plasma progesterone concentration, and detection of estrus were done daily from Day 5 to the day of subsequent ovulation. Treatment with hCG induced an accessory CL, increased CL volume, and plasma progesterone concentration throughout the luteal phase (P<0.01). Estradiol-17beta induced atresia and recruitment of a new wave of follicular growth; it eliminated a potentially estrogen-active, growing ovarian follicle within the critical period for maternal recognition of pregnancy, but it also hastened luteolysis (Days 16 or 17 vs. Days 18 or 19 in non-treated cows). In conclusion, the approaches tested enhanced luteal function (hCG) and altered ovarian follicular dynamics (estradiol-17beta), but were unable to extend the life-span of the CL in Nelore cows.     

Zebu (Bos indicus) ovarian preantral follicles: morphological characterization and development of an efficient isolation method

Preantral follicles are a major source of oocytes, and their utilization as an important tool to store large number of female gametes for future use in reproductive programs has been investigated. The increasing importance of studies in this subject, together with the important role of Zebu cattle in the economy of tropical and subtropical countries as well as their well-known differences from European cattle, led to this research. The present study aims to determine the best size interval for sectioning ovarian tissue to isolate preantral follicles from Zebu cows using a tissue chopper and to evaluate the follicular quality after isolation. Furthermore, it aims to provide information about the Zebu cow preantral follicle population and use this data (as a control) to evaluate the effectiveness of the tested isolation method. Testing eight different tissue sectioning size intervals, it was possible to conclude that the 125-microm-section interval is shown to be better than the intervals of 25, 50, 175 and 200 microm to isolate preantral follicles from Zebu cow ovaries. The 125-microm interval allowed the recovery of 26,050+/-1611 (mean +/- S.E.M.) preantral follicles per one-half ovary, while the number of preantral follicles in situ estimated by evaluation of histological sections was 35,288+/-2342 per one-half ovary. Thus, the mean (+/-S.E.M.) recovery rate (=[number of preantral follicles isolated/number of preantral follicles in situ in the same ovary] x 100) was 74.3+/-4.3%. The morphometrical analysis showed that Bos indicus preantral follicles are similar to B. taurus preantral follicles based on previous reports. In conclusion, this study showed that a simple, mechanical method can be used effectively to isolate a large number of intact preantral follicles from Zebu cow ovaries, with a high recovery rate.     

Characterization of service intervals and frequency of short oestrus cycles in Zebu (Bos indicus) cows in Ethiopia.

Data collected over a 10-yr period on 1,778 service intervals in 1,111 Arsi (Bos indicus), cows at the Ethiopian Ministry of Agriculture ranch were analyzed. Conception rate to first service was 48%, cows calving from June to February being more likely to conceive at first oestrus. Overall interval between services in animals returning for insemination averaged 53 +/- 40 (SD), range 6-262 d. There were (6%) "short" cycles of less than 17 d, mostly during the first (69%) and second (30%) intervals (P less than 0.01). A quarter of service periods (24%) were within the normal length of 18-24 d, 52% were its multiples while 18% were abnormal and probably indicative of embryonic mortality. First oestrus cycle length was affected by year (P less than 0.01) and season of calving (P less than 0.05). Second oestrus cycle length was influenced by season of calving and first oestrus onset (P less than 0.05). It is concluded that the low frequency of normal cycles is to a large extent due to heats which remained undetected by visual observation in Arsi cows under artificial insemination programmes.     

Microsatellite Analysis of Genetic Population Structure of Zebu Cattle (Bos indicus) Breeds from North-Western Region of India

The present study aims to understand the existing genetic diversity and structure of six native cattle breeds (Rathi, Tharparkar, Nagori, Mewati, Gir, and Kankrej) adapted to the north-western arid and semi-arid region of India based on microsatellite loci. Various diversity estimates, mean number of alleles (12.84); effective number of alleles (5.02); gene diversity (0.769), and observed heterozygosity (0.667) reflected the existence of substantial within-breed diversity in all the investigated cattle breeds. Mean estimates of F-statistics: F_IT = 0.144 ± 0.023, F_IS = 0.071 ± 0.021, and F_ST = 0.078 ± 0.014 were significantly different from zero (P < 0.05). The interbreed relationships indicated moderate level of breed differentiation between the six cattle breeds with least differentiation between Kankrej-Mewati pair. The phylogeny structuring further supported close grouping of Kankrej and Mewati breeds. Correspondence analysis plotted Rathi, Tharparkar, and Gir individuals into three separate areas of multivariate space; whereas, Kankrej, Mewati, and Nagori cattle showed low breed specific clustering. This reflected the existence of discrete genetic structure for Tharparkar, Rathi, and Gir, the prominent dairy breeds of the region; whereas, admixture was observed for Kankrej, Mewati, and Nagori individuals.     

Ovarian follicular dynamics in suckled zebu (Bos indicus) cows monitored by real time ultrasonography

The pattern of follicular growth was studied in 17 suckled zebu cows with average body condition and under extensive management in a tropical environment (23 degrees C, 78% humidity; 2200 mm annual rainfall; 1000 m altitude). The study covered the period from parturition to weaning at 12 months postpartum (PP). Data were collected by transrectal ultrasonography (7.5 MHz) at 48 h intervals, and progesterone (P4) measurements were performed by RIA. The sequential development of ovarian follicles greater than 4 mm was followed until regression or ovulation. Ovarian activity as characterized by growth and regression of follicles of 4 to 6 mm, with sporadic dominance, and a long interdominance interval was observed in every cow and from as early as 26 +/- 2 days PP. This follicular pattern was highly variable during the first 6 months: cows presented 2 to 20 follicular waves (FW) in which a dominant follicle (DF) grew to 8 +/- 1 mm with daily growth rates of 1.1 +/- 0.5 mm/day. The duration of dominance varied from 2 to 8 days and the interdominance time interval was 0 (overlapped waves) to 60 days. Neither behavioural oestrus nor ovulation was observed during this period. From 6 to 12 months PP, cows presented 7 to 20 FW, some with ovulation and/or corpora lutea (CL) formation. The ovulation was preceded by oestrus in some cases (43%). The mean (+/- sem) diameter of DF was 9 +/- 2.7 mm, their mean growth rate 1.4 +/- 0.2 mm/day, their duration of dominance was 2 to 8 days and the interdominance interval was 0 to 14 days. Progesterone concentrations (P4) from 1.0 to 13 ng/ml were found when a CL was present. Once cyclicity re-commenced at 217 to 278 days PP, the cows presented either normal (21 +/- 3 days), short (10 +/- 2 days), or long (50 +/- 4 days) cycles. The resumption of cyclicity was characterized by an increased frequency of emerging follicular waves. Under the conditions of this study, the suckled Bos indicus cows re-commenced ovarian follicular activity as early as described in B. taurus breeds, but the establishment of cyclicity was substantially later. These data add further to the panorama of postpartum reproductive physiology in tropical cattle.     

Fertility on synchronized estrus in crossbred (Bos taurus x Bos indicus) heifers

This study was performed in Western Maharastra (India). The 272 crossbred heifers were randomly allocated within herds to one of the four following groups: 1) silastic coils, 10 days treatment (n = 65); 2) Norgestomet implants, 10 days treatment (n = 71); 3) prostaglandin F(2alpha) two injections 11 days apart (n = 70); and 4) control (n = 66). Almost all heifers in the treated groups were detected in heat during the four days following treatment (88-100%) vs 26% in the control group in the first 21 days. Mean conception rates at first AIs were respectively 62,48 and 60% in groups 1,2 and 4 (p > 0.05) and only 29% in group 3. By 90 days after treatment, 66, 59, 46 and 33 per cent of the females were pregnant for groups 1 to 4, respectively (p < 0.001). In conclusion, progestogen treatments seemed to be highly satisfactory both in terms of conception rates and intervals from treatment to pregnancy.     

Biostimulatory effects of estrous cows and bulls on resumption of ovarian activity in postpartum anestrous Zebu (Bos indicus) cows in the humid tropics

Suckled postpartum Zebu (Bos indicus) cows were exposed either to estrous females alone or together with bulls to determine if this regimen would stimulate the resumption of ovarian activity. The study was carried out on 60 Zebu cows. The animals were allocated at parturition to 1 of 3 treatment groups. Group FB cows (n = 14) were exposed to progestogen treated females (approximately 3 cows per progestogen treated cow) and a bull for 42 d. Group F cows (n = 31) were exposed to progestogen treated females and after 21 d a bull was introduced and remained with the group until the end of the experiment 21 d later. Estrus was induced with Syncro Mate B treatment and the cows were in estrus when introduced into Groups FB and F. Group N cows (n = 15) were introduced to a bull 21 d after the treatments had begun in Groups FB and F, and the bull remained with these cows until the end of the study. On average, resumption of ovarian activity occurred in 57% (8/14), 19% (6/31) and 7% (1/15) of the cows in Group FB, F and N, respectively, within 21 d after the start of treatments. The difference was significant between Group FB and Groups F and N (P < 0.05). During the second part of the experiment, in which the bull was introduced to Groups F and N, an additional 32% (10/31) of the cows in Group F and 33% (5/15) in Group N resumed ovarian activity. No cows in Group FB resumed ovarian activity during this period. There were significant differences in body condition between cows that resumed ovarian activity and those that remained in anestrus (P < 0.05). We conclude that biostimulation effectively enhanced resumption of ovarian activity in anestrous suckled Zebu cows. This technique offers a potentially useful and practical way to improve reproductive efficiency in anestrous Zebu cattle in the tropics.     

Effects of scrotal insulation on sperm production,semen quality,and testicular echotexture in Bos indicus and Bos indicus x Bos taurus bulls

The objectives of the present study were to evaluate the effects of scrotal insulation on sperm production, semen quality, and testicular echotexture in Bos indicus and Bos indicus x Bos taurus crossbred bulls. In one experiment, B. indicus bulls (n=12) were allocated to control and whole-scrotum insulation groups, while in a second experiment, crossbred bulls (n=21) were allocated into control, whole-scrotum, and scrotal-neck insulation groups. Insulation was applied for 4 days (start of insulation = Day 0) and semen collection and testicular ultrasonographic examinations were performed twice weekly until Day 35. Sperm concentration and total sperm output during the post-insulation period were greater in control groups, but significant differences were observed only in B. indicus bulls. Overall, sperm motility in scrotal-insulated B. indicus bulls was lower (P<0.05) than in the control group. After whole-scrotum insulation in crossbred bulls, sperm motility was lower (P<0.05) than pre-insulation levels between Days 21 and 31, and lower than control levels on Day 24. The proportion of normal sperm after whole-scrotum insulation was lower than pre-insulation and control values from Day 11 to the end of the experiment in B. indicus bulls (P<0.05 from Days 14 to 21 and on Day 27), and from Days 14 to 25 in crossbred bulls (P<0.05 on Days 14 and 18). Insulation of the scrotal neck in crossbred bulls did not significantly affect semen quality. Loose sperm heads (Day 11), midpiece defects (Days 11 and 14), and acrosome defects (Days 27 and 31) increased (P<0.05) in insulated B. indicus bulls, while proximal cytoplasmic droplets (Days 14, 18 and 27 in B. indicus; Days 24 and 27 in crossbred bulls) and sperm vacuoles (Days 18 and 21 in B. indicus; Day 18 in crossbred bulls) increased (P<0.05) in whole-scrotum insulation groups in both experiments. There was considerable variation among bulls in the incidence of specific sperm defects. The timing of appearance of sperm defects after insulation provided insights into the pathogenesis of specific abnormalities. Neither whole-scrotum nor scrotal-neck insulation affected testicular echotexture in either experiment. In conclusion, whole-scrotum insulation resulted in decreased sperm production and semen quality in B. indicus and B. indicus x B. taurus bulls, but those changes were not associated with changes in testicular echotexture.     

Comparative analysis of GDF 8 (myostatin) in Bos indicus and Bos taurus.

We report the myostatin gene sequence of Bos indicus cattle in comparison to Bos taurus. B. indicus genomic sequence was obtained by overlapping PCR amplification of genomic DNA. Exon splice sites were confirmed by mRNA sequencing. There were 5 exonic single nucleotide polymorphisms (SNP) only one of which was a non-synonymous mutation that resulted in a serine to asparagine (S214N) amino acid substitution. The B. indicus gene has two insertions of 16 and 12 bases in the first intron. In addition, SNPs in the 3' UTR and intronic regions are also reported.     

Accuracy of genomic predictions in Bos indicus (Nellore) cattle

Background

Nellore cattle play an important role in beef production in tropical systems and there is great interest in determining if genomic selection can contribute to accelerate genetic improvement of production and fertility in this breed. We present the first results of the implementation of genomic prediction in a Bos indicus (Nellore) population.

Methods

Influential bulls were genotyped with the Illumina Bovine HD chip in order to assess genomic predictive ability for weight and carcass traits, gestation length, scrotal circumference and two selection indices. 685 samples and 320 238 single nucleotide polymorphisms (SNPs) were used in the analyses. A forward-prediction scheme was adopted to predict the genomic breeding values (DGV). In the training step, the estimated breeding values (EBV) of bulls were deregressed (dEBV) and used as pseudo-phenotypes to estimate marker effects using four methods: genomic BLUP with or without a residual polygenic effect (GBLUP20 and GBLUP0, respectively), a mixture model (Bayes C) and Bayesian LASSO (BLASSO). Empirical accuracies of the resulting genomic predictions were assessed based on the correlation between DGV and dEBV for the testing group.

Results

Accuracies of genomic predictions ranged from 0.17 (navel at weaning) to 0.74 (finishing precocity). Across traits, Bayesian regression models (Bayes C and BLASSO) were more accurate than GBLUP. The average empirical accuracies were 0.39 (GBLUP0), 0.40 (GBLUP20) and 0.44 (Bayes C and BLASSO). Bayes C and BLASSO tended to produce deflated predictions (i.e. slope of the regression of dEBV on DGV greater than 1). Further analyses suggested that higher-than-expected accuracies were observed for traits for which EBV means differed significantly between two breeding subgroups that were identified in a principal component analysis based on genomic relationships.

Conclusions

Bayesian regression models are of interest for future applications of genomic selection in this population, but further improvements are needed to reduce deflation of their predictions. Recurrent updates of the training population would be required to enable accurate prediction of the genetic merit of young animals. The technical feasibility of applying genomic prediction in a Bos indicus (Nellore) population was demonstrated. Further research is needed to permit cost-effective selection decisions using genomic information.     

Influence of the breed of bull (Bos taurus indicus vs. Bos taurus taurus) and the breed of cow (Bos taurus indicus, Bos taurus taurus and crossbred) on the resistance of bovine embryos to heat

In vitro studies have shown that Bos taurus indicus (B. t. indicus) embryos submitted to heat shock at early stages of development are better able to survive as compared to Bos taurus taurus embryos. Embryo genotype influences resistance to heat shock thus leading to the question as to whether embryos sired by thermo-tolerant breeds exhibit the same resistance to heat shock. In the present study the influence of both oocyte and semen, on the resistance to heat shock (HS) at early stages of in vitro development, was assessed in B. t. indicus [Nelore (N) breed], B. t. taurus [Holstein (H) and Angus (A) breeds] and crossbreds. In Experiment 1, Nelore and crossbred oocytes were collected from slaughterhouse ovaries and fertilized with spermatozoa from Nelore and Angus bulls. Presumptive embryos were collected and randomly assigned to control (39 degrees C) or HS at 12, 48 or 96 h post insemination (hpi; 41 degrees C for 12h) treatments. The cleavage rates and proportion of embryos developing to the blastocyst and hatched blastocyst stages were recorded on Days 2, 8 and 10, respectively. Heat shock treatment decreased development of both Nelore and crossbred embryos. There was a significant interaction between time (12, 48 or 96 hpi) and temperature for blastocyst rates, i.e., the embryos became more thermotolerant as development proceeded. In Experiment 2, oocytes from Nelore and Holstein cows were fertilized with semen from bulls of either Nelore or Angus breeds, and subjected to 12 h HS at 96 hpi. Heat shock at 96 hpi, decreased embryo development. Additionally, cowxtreatment and bullxtreatment interactions were significant for blastocyst rates, i.e., both breed of cow and breed of bull affected the decline in blastocyst rate caused by heat shock treatment. In conclusion, the present results indicate that Nelore embryos (indicus) are more resistant to heat shock than Holstein (taurus) at early stages of in vitro development, and that embryos become more thermo-tolerant as development proceeds. Additionally, the resistance to heat shock was a result of the genetic contribution from both oocyte and spermatozoa.     

Analysis of Genetic Variation at the Prolactin-RsaI (PRL-RsaI) Locus in Indian Native Cattle Breeds (Bos indicus)

This study assessed the distribution pattern of allelic variants at the prolactin-RsaI locus in 23 Indian native cattle breeds (Bos indicus). PCR-RFLP genotyping of a 156?bp fragment of prolactin (PRL) in exon 3 revealed the predominance of the heterozygous AB genotype (mean frequency 0.58) irrespective of utility type (dairy, dual, draft), geographic region (northern, central, southern), and coat color (red, gray) of the breeds analyzed. The overall frequencies of homozygous AA (0.22) and BB (0.20) genotypes were in a similar range. The PRL (A) and PRL (B) alleles exhibited similar gene frequencies (means 0.52 and 0.48, respectively). The existing profile of the PRL-RsaI gene locus in a large set of Indian native cattle breeds was different from that of Bos taurus and cattle breeds of other countries, where either the BB genotype and PRL (B) allele or the AA genotype and PRL (A) allele have been reported to be more prevalent.     

Studies on purine turnover in the camel (Camelus dromedarius) and zebu (Bos indicus)

Significantly higher hypoxanthine over uric acid ratios were found in camel plasma and urine, with respect to those of zebu. Enzyme levels of purine catabolism were markedly lower in camel than in zebu liver. Oxidation of hypoxanthine appears to be the limiting step of purine metabolism in camel liver. Any hepatic hypoxanthine appears to be actively converted into IMP in camel liver, rather than oxidized to uric acid.     

Effects of lowered temperatures and media on short-term preservation of zebu (Bos indicus) preantral ovarian follicles

The maintenance of follicle quality during the transportation of ovaries is essential for the successful cryopreservation and in vitro development of preantral follicles. The objective of this study was to evaluate the effect of cooling ovarian tissue on the conservation of zebu cow preantral follicles. Ovarian pieces were immersed in saline or coconut water (CW) solutions and maintained at 4 or 20 degrees C for 6, 12, or 18 h. Preantral follicles were evaluated by histology and transmission electron microscopy. Storage of ovarian pieces at 20 degrees C for 12 or 18 h significantly reduced the percentage of morphologically normal follicles compared to controls. In contrast, conservation at 4 degrees C for up to 18 h and at 20 degrees C for up to 6 h kept the percentage of normal follicles similar to controls. However, the type of solution that the ovaries were immersed in had little effect on the results. Decreased cellular metabolism probably accounted for better preservation of preantral follicles at 4 degrees C. In conclusion, zebu cow ovaries were successfully stored at 4 degrees C for up to 18 h with no morphological damage to preantral follicles. However, at 20 degrees C, ovaries could only be stored for 6 h.     

Influence of Restricted Suckling and Level of Feed Supplementation on Postpartum Reproductive Performance of Zebu and Crossbred Cattle in the Semi-Arid Tropics

This study was carried out in central Tanzania on a group of 45 Zebu and 37 crossbred cows which were 4 to 10 years old. At calving time, the animals were allocated to one of the 4 treatment groups. In addition to free access to grazing for all cows in the study, in group H: AR (n = 18), cows were fed a high level of concentrate supplementation (4kg/day) and calves were artificially reared; in group H:RS (n = 24), cows were fed a high level of concentrate supplementation (4kg/day) and calves were only allowed restricted suckling up until the weaning age of 6 months. In group L:AR (n = 23) cows were fed a low level of concentrate supplementation (2kg/day) and calves were artificially reared; and in group L:RS (n = 17) cows were fed a low level of concentrate supplementation (2kg/day) and calves were only allowed restricted suckling up until the weaning age of 6 months. Milk progesterone was used as a means of determining the postpartum resumption interval (PRI) and the interval from parturition to conception (PCI). The overall PRI was 47.4 ± 0.4 days and was significantly affected by breed but not by calving season, with crossbred cows exhibiting a shorter PRI than Zebu cows. The effect of the treatments was significant, with cows in the group H:AR displaying a significantly shorter PRI than those in the other groups, while cows in group L:RS showed a significantly longer PRI than those in the other groups. The overall PCI was 149.5 ±3.7 days, and was not significantly affected by breed or calving season. The effect of the treatments was significant, with cows in the group H:AR having a significantly shorter PCI than cows in the other groups, while cows in group L:RS showed a significantly longer PCI than those in the other groups. Crossbred cows had higher live weights at calving (299.4 kg) than Zebu cows (272.6 kg), while all cows gained weight during the first 3 months after calving. The treatments had a significant effect on weight gain, with cows in the group H:AR gaining significantly more weight than those in the other groups. Cows which had high live weights at calving exhibited significantly shorter PRI and PCI than the lighter cows. Animals which had gained more than 5 kg during the first month after calving, or which had gained more than 8 kg during the first 3 months after calving, showed significantly shorter PRI and PCI than cows which had gained less weight. The results show that the calf rearing system and the level of feed supplementation interact with each other and can influence the postpartum anoestrous period in Zebu and Zebu crossbred cattle. Increasing the level of nutrition in restricted suckling cows tended to improve the postpartum anoestrous period, but the positive effects of supplementation could not completely compensate for the negative effects of suckling.     

Investigation of X- and Y-specific single nucleotide polymorphisms in taurine (Bos taurus) and indicine (Bos indicus) cattle

Initially, domesticated African cattle were of taurine type. Today, we find both African Bos taurus and Bos indicus cattle, as well as their crossbreeds, on the continent of Africa and they all share the same set of African taurine mitochondrial DNA haplogroups. In this study, we report genetic variation as substitutions and insertions/deletions (indels) on both the X and Y chromosomes, and use the variation to assess hybridization between taurine and indicine cattle. Six African cattle breeds (four Sanga breeds, including Raya Azebu, Danakil, Caprivi, Nguni; and two Zebu breeds, including Kilimanjaro Zebu and South Kavirondo Zebu) were screened for six new X-chromosomal markers, specifically three single nucleotide polymorphisms and three indels in the DDX3X (previously DBX ) and ZFX genes, and five previously identified Y-chromosomal markers in the DDX3Y (previously DBY ) and ZFY genes. In total, 90 (57 bulls and 33 cows) samples from the African breeds were analysed. We identify five diagnostic haplotypes of indicine and taurine origins on both the X and Y chromosomes. For each breed, the level of indicine introgression varies; in addition to pure taurine, indicine and hybrid X-chromosome individuals, recombinant X-chromosome variants were also detected. These markers are useful molecular tools for assessing the level of indicine admixture in African cattle breeds.     

Ciliate Protozoa in the Rumen of Kenyan Zebu Cattle,Bos taurus indicus,with the Description of Four New Species1

ABSTRACT. The composition of the fauna of rumen ciliates in zebu cattle in Kenya was surveyed and 13 genera containing 51 species with 19 formae were identified. Four new species were recognized, then described as Diplodinium africanum n. sp., Diplodinium nanum n. sp., Eudiplodinium kenyensis n. sp., and Ostracodinium iwawoi n. sp. In addition, Buetschlia triciliata and Ostracodinium stokyi were found for the second and third times and described as Hsiungia triciliata n. comb. and Enoploplastron stokyi n. stat., with two formae, respectively. The species composition was similar to that of Indian zebu but several species were considered to originate from African native ruminants. In the percentage composition of genera, the numbers of Entodinium, which normally predominate in rumens in other areas, were very low.