Clinical and subclinical mastitis in smallholder dairy farms in Tanzania: Risk, intervention and knowledge transfer

In a cross-sectional study of 400 randomly selected smallholder dairy farms in the Tanga and Iringa regions of Tanzania, 14.2% (95% confidence interval (CI) = 11.6-17.3) of cows had developed clinical mastitis during the previous year. The point prevalence of subclinical mastitis, defined as a quarter positive by the California Mastitis Test (CMT) or by bacteriological culture, was 46.2% (95% Cl = 43.6-48.8) and 24.3% (95% Cl = 22.2-26.6), respectively. In a longitudinal disease study in Iringa, the incidence of clinical mastitis was 31.7 cases per 100 cow-years. A randomised intervention trial indicated that intramammary antibiotics significantly reduced the proportion of bacteriologically positive quarters in the short-term (14 days post-infusion) but teat dipping had no detectable effect on bacteriological infection and CMT positive quarters. Other risk and protective factors were identified from both the cross-sectional and longitudinal included animals with Boran breeding (odds ratio (OR) = 3,40, 95% CI = 1.00-11.57, P < 0.05 for clinical mastitis, and OR = 3.51, 95% CI = 1.299.55, P < 0.01 for a CMT positive quarter), while the practice of residual calf suckling was protective for a bacteriologically positive quarter (OR = 0.63, 95% Cl = 0.48-0.81, P <= 0.001) and for a CMT positive quarter (OR = 0.69, 95% Cl = 0.63-0.75, P < 0.001). A mastitis training course for farmers and extension officers was held, and the knowledge gained and use of different methods of dissemination were assessed over time. In a subsequent randomised controlled trial, there were strong associations between knowledge gained and both the individual question asked and the combination of dissemination methods (village meeting, video and handout) used. This study demonstrated that both clinical and subclinical mastitis is common in smallholder dairying in Tanzania, and that some of the risk and protective factors for mastitis can be addressed by practical management of dairy cows following effective knowledge transfer. (c) 2006 Elsevier B.V. All rights reserved.

Clinical and subclinical mastitis in smallholder dairy farms in Tanzania: Risk, intervention and knowledge transfer

In a cross-sectional study of 400 randomly selected smallholder dairy farms in the Tanga and Iringa regions of Tanzania, 14.2% (95% confidence interval (CI) = 11.6-17.3) of cows had developed clinical mastitis during the previous year. The point prevalence of subclinical mastitis, defined as a quarter positive by the California Mastitis Test (CMT) or by bacteriological culture, was 46.2% (95% Cl = 43.6-48.8) and 24.3% (95% Cl = 22.2-26.6), respectively. In a longitudinal disease study in Iringa, the incidence of clinical mastitis was 31.7 cases per 100 cow-years. A randomised intervention trial indicated that intramammary antibiotics significantly reduced the proportion of bacteriologically positive quarters in the short-term (14 days post-infusion) but teat dipping had no detectable effect on bacteriological infection and CMT positive quarters. Other risk and protective factors were identified from both the cross-sectional and longitudinal included animals with Boran breeding (odds ratio (OR) = 3,40, 95% CI = 1.00-11.57, P < 0.05 for clinical mastitis, and OR = 3.51, 95% CI = 1.299.55, P < 0.01 for a CMT positive quarter), while the practice of residual calf suckling was protective for a bacteriologically positive quarter (OR = 0.63, 95% Cl = 0.48-0.81, P <= 0.001) and for a CMT positive quarter (OR = 0.69, 95% Cl = 0.63-0.75, P < 0.001). A mastitis training course for farmers and extension officers was held, and the knowledge gained and use of different methods of dissemination were assessed over time. In a subsequent randomised controlled trial, there were strong associations between knowledge gained and both the individual question asked and the combination of dissemination methods (village meeting, video and handout) used. This study demonstrated that both clinical and subclinical mastitis is common in smallholder dairying in Tanzania, and that some of the risk and protective factors for mastitis can be addressed by practical management of dairy cows following effective knowledge transfer. (c) 2006 Elsevier B.V. All rights reserved.

Prevalence of subclinical mastitis and associated risk factors in smallholder dairy cows in Tanzania

A cross-sectional study was carried out on 200 randomly selected farms in each of the Iringa and Tanga regions of Tanzania to estimate the prevalence and risk factors for subclinical mastitis in dairy cows kept by smallholders. Subclinical mastitis was assessed using the California mastitis test (CMT), and by the bacteriological culture of 1500 milk samples collected from 434 clinically normal cows. The percentages of the cows (and quarters) with subclinical mastitis were 75.9 per cent (46.2 per cent) when assessed by the CMT and 43.8 per cent (24.3 per cent) when assessed by culture. Factors significantly associated with an increased risk of a CMT-positive quarter were Boran breed (odds radio [OR]=3.51), a brought-in cow (rather than homebred) (OR=2.39), peak milk yield, and age. The stripping method of hand milking was associated with a significantly lower prevalence Of CMT-positive quarters (OR=0.51). The CMT-positive cows were more likely to be culture positive (OR=4.51), as were brought-in (OR=2.10) and older cows.

Effect of restricted suckling of calves on the productivity of crossbred dairy cattle

An experiment on restricted suckling of crossbred dairy cows was conducted at the Livestock Research Centre, Tanga in north-east Tanzania. The objective of the experiment was to evaluate the comparative productivity of Bos taurus x Bos indicus cows of medium and high levels of Bos taurus inheritance, whose calves were either bucket-reared or suckled residual milk. Lactation milk yield, length and persistency were 1563 L, 289 days, and 1.0, respectively, for the bucket-reared and 1592 L, 289 days and 1.4, respectively, for the suckling group. Days to observed oestrus, first insemination and conception for cows whose calves were bucket-reared were 47, 74 and 115 days, respectively, and 57, 81 and 126 days, respectively, for the suckling cows. The calf weights were similar at 1 year of age. The productivity of the cows, measured as the annual milk offtake, was not significantly higher for those that suckled their calves than for those whose calves were bucket-reared.

Productivity of crossbred dairy cows suckling their calves for 12 or 24 weeks post calving

An experiment on restricted suckling of crossbred dairy cows was conducted at the Livestock Research Centre, Tanga in northeast Tanzania. Thirty-six Bos taurus (Holstein Friesian and Jersey) x Bos indicus (East African Zebu) cows were allocated alternately as they calved to suckling their calves for either 12 or 24 weeks after calving. Cows grazed improved pastures and were offered 4 kg concentrate daily. Milking occurred twice daily by hand; calves were allowed to suck residual milk for 30 min following each milking. Calves were also allowed access to grazing and were offered a maximum of I kg concentrate daily to 24 weeks of age. Weaning age had no significant effect on lactation milk yield for human consumption, the mean (SE) yield being 1806 (102.0) L and 1705 (129. 1) L for 12- and 24-week weaning, respectively. Cows from the two treatments suffered similar losses of live weight and body condition score during lactation and neither group had returned to the original body condition score 40 weeks following calving. Post-partum anoestrous intervals were prolonged. Although not significant, cows suckling calves to 24 weeks had a mean interval to first oestrus extended by 38 days compared with cows suckling calves to 12 weeks. The mean (SE) daily live weight gains of the calves to 52 weeks were 263 (14.1) g/day and 230 (18.1) g/day for calves weaned at 12 and 24 weeks, respectively, such that 12-month weights were 119 (5.6) kg and 110 (7.3) kg, respectively. Twelve-week-weaned calves consumed more concentrate (p < 0.05) from 13 to 24 weeks than did 24-week weaned calves. Calculation of residual milk consumption removed by calves from birth to 12 weeks indicated that it accounted for 28% of total yield. No benefits in cow and calf performance and welfare were found to justify prolonging the suckling period to 24 weeks.

The effects of a short-term increase in supplementation on the reproduction performance in lactating crossbred dairy cows

The hypothesis that dairy cows partially suckling their calves would ovulate following removal of calves when restored to positive energy balance by a short-term increase in supplementation was investigated in 65 crossbred cows. Five treatments (T1, T2, T3, T4, and T5) that differed in the amount of total concentrate fed from calving to week 24 were involved. Calves were allowed to suck residual milk to 12 weeks of age. Energy balance was estimated by measuring intake, milk yield and organic matter digestibility. The occurrence of ovulation was determined by the analysis of milk progesterone (P4) concentration. Four groups that were receiving additional supplementation were restored to positive energy balance, while the control group (T I) remained in negative energy balance. The percentage of cows ovulating was 36%, 58%, 92%, 90% and 60% for T1, T2, T3, T4 and T5, respectively (P = 0.026). Comparison of the timing of ovulation for combined results from T1+T2 and T3+T4+T5 estimated mean time to fail to ovulate as 110 +/- 9.0 and 87 +/- 7.6 days, respectively (p = 0.023). The percentage of the cows showing oestrus was 9%, 8%, 33%, 40% and 40% for T1, T2, T3, T4 and T5, respectively (P = 0.197). Short-term increases in supplementation are unlikely to be an attractive means of reducing calving intervals.

Some factors affecting variation in milk yield in crossbred dairy cows on smallholder farms in north-east Tanzania

A 2-year longitudinal survey was carried out to investigate factors affecting milk yield in crossbred cows on smallholder farms in and around an urban centre. Sixty farms were visited at approximately 2-week intervals and details of milk yield, body condition score (BCS) and heart girth measurements were collected. Fifteen farms were within the town (U), 23 farms were approximately 5 km from town (SU), and 22 farms approximately 10 km from town (PU). Sources of variation in milk yield were investigated using a general linear model by a stepwise forward selection and backward elimination approach to judge important independent variables. Factors considered for the first step of formulation of the model included location (PU, SU and U), calving season, BCS at calving, at 3 months postpartum and at 6 months postpartum, calving year, herd size category, source of labour (hired and family labour), calf rearing method (bucket and partial suckling) and parity number of the cow. Daily milk yield (including milk sucked by calves) was determined by calving year (p < 0.0001), calf rearing method (p = 0.044) and BCS at calving (p < 0.0001). Only BCS at calving contributed to variation in volume of milk sucked by the calf, lactation length and lactation milk yield. BCS at 3 months after calving was improved on farms where labour was hired (p = 0.041) and BCS change from calving to 6 months was more than twice as likely to be negative on U than SU and PU farms. It was concluded that milk production was predominantly associated with BCS at calving, lactation milk yield increasing quadratically from score 1 to 3. BCS at calving may provide a simple, single indicator of the nutritional status of a cow population.

Some factors affecting reproductive success in crossbred dairy cows on smallholder farms in coastal north-east Tanzania

A 2-year longitudinal survey was carried out to investigate factors affecting reproduction in crossbred cows on smallholder farms in and around an urban centre. Sixty farms were visited at approximately 2-week intervals and details of reproductive traits and body condition score (BCS) were collected. Fifteen farms were within the town (U), 23 farms were approximately 5 km from town (SU), and 22 farms approximately 10 km from town (PU). Sources of variation in reproductive traits were investigated using a general linear model (GLM) by a stepwise forward selection and backward elimination approach to judge important independent variables. Factors considered for the first step of formulation of the model included location (PU, SU and U), type of insemination, calving season, BCS at calving, at 3 months postpartum and at 6 months postpartum, calving year, herd size category, source of labour (hired and family labour), calf rearing method (bucket and partial suckling) and parity number of the cow. The effects of the independent variables identified were then investigated using a non-parametric survival technique. The number of days to first oestrus was increased on the U site (p = 0.045) and when family labour was used (p = 0.02). The non-parametric test confirmed the effect of site (p = 0.059), but effect of labour was not significant. The number of days from calving to conception was reduced by hiring labour (p = 0.003) and using natural service (p = 0.028). The non-parametric test confirmed the effects of type of insemination (p = 0.0001) while also identifying extended calving intervals on U and SU sites (p = 0.014). Labour source was again non-significant. Calving interval was prolonged on U and SU sites (p = 0.021), by the use of AI (p = 0.031) and by the use of family labour (p = 0.001). The non-parametric test confirmed the effect of site (p = 0.008) and insemination type (p > 0.0001) but not of labour source. It was concluded that under favourable conditions (PU site, hired labour and natural service) calving intervals of around 440 days could be achieved.

Evaluation of PCR to detect Theileria parva in field-collected tick and bovine samples in Tanzania

The ability of PCR to detect infections of Theileria parva, the cause of East Coast Fever, in field-collected tick and bovine samples from Tanzania was evaluated. PCR-detected infection prevalence was high (15/20, 75%) in unfed adult Rhipicephalus appendiculatus ticks that fed as nymphs on an acutely-infected calf, but low (22/836, 2.6%) in unfed adult R. appendiculatus collected from field sites in Tanzania. Tick infection prevalence was comparable to that in previous studies that used salivary gland staining to detect T parva infection in field-collected host-seeking ticks. Of 282 naturally-exposed zebu calves, seven had PCR-positive buffy coat samples prior to detection of Theileria spp. parasites in stained huffy coat cells or lymph node biopsies. Evidence of Theileria spp. infections was detected in stained smears of lymph node biopsies from 109 calves (38.6%) and huffy coat samples from 81 (28.7%), while huffy coat samples from 66 (23.4%) were PCR-positive for T parva. Implications of these findings for the sensitivity and specificity of the PCR are discussed. (C) 2003 Elsevier Science B.V. All rights reserved.

Risk factors for tick attachment to smallholder dairy cattle in Tanzania

A cross-sectional study was conducted in Tanga and Iringa regions of Tanzania, and a longitudinal study in Tanga, to investigate tick-control methods and other factors influencing tick attachment to the cattle of smallholder dairy farms. Most farmers reported applying acaricides at intervals of 1-2 weeks, most used acaricides that require on-farm dilution and most farmers incorrectly diluted the acaricides. Rhipicephalus appendiculatus and Boophilus spp. ticks were those most-frequently encountered on the cattle, but few cattle carried ticks of any species (only 13 and 4.6% of tick counts of the cattle yielded adult R. appendiculatus and Boophilus spp., respectively). Animals were more likely to carry one or more adult Boophilus spp. ticks if they also carried one or more R. appendiculatus adults (OR = 14.4, CI = 9.2, 22.5). The use of pour-on acaricides was associated with lower odds that animals carried a R. appendiculatus tick (OR = 0.29, CI = 0. 18, 0.49) but higher odds that they carried a Boophilus spp. tick (OR = 2.48, CI = 1.55, 3.97). Animals > 4 months old and those with a recent history of grazing had higher odds of carrying either a R. appendiculatus (ORs = 3.41 and 2.58, CIs = 2.34, 4.98 and 1.80, 3.71), or a Boophilus spp. tick (ORs = 5.70 and 2.18, CIs = 2.34, 4.98 and 1.49. 3.25), but zero-grazing management did not prevent ticks attaching to cattle even when combined with high-frequency acaricide treatments. The odds that animals carried ticks varied amongst the agro-ecological zones (AEZs) and administrative districts where the farms were situated-but there was still considerable residual variation in tick infestation at the farm level. (c) 2004 Elsevier B.V. All rights reserved.

Seasonality of reproduction in sheep

Unlike most domestic livestock species, sheep are widely known as an animal with marked seasonality of breeding activity. The annual cycle of daily photoperiod has been identified as the determinant factor of this phenomenon, while environmental temperature, nutritional status, social interactions, lambing date and lactation period are considered to modulate it. The aim of this paper is to review the current state of knowledge of the reproductive seasonality in sheep. Following general considerations concerning the importance of seasonal breeding as a reproductive strategy for the survival of species, the paper describes the manifestations of seasonality in both the ram and the ewe. Both determinant and modulating factors are developed and special emphasis is given to the neuroendocrine base of photoperiodic regulation of seasonal breeding. Other aspects such as the role of melatonin, the involvement of thyroid hormones and the concept of photorefractoriness are also reviewed. (C) 2003 Elsevier Science B.V. All rights reserved.

The effect of paddock size on the response of seasonal anoestrous ewes to the ram effect

Many aspects of the conditions required to maximize the ewe's response to ram introduction in the late anoestrous season remain unclear. The aim of this research was to determine whether grazing space allowances could influence the efficacy of the ram effect. In August 1995, at Reading (latitude 51degrees27'N), following a 3-month isolation period from rams, two groups of nulliparous Mule ewes, aged 15 months, were introduced to four rains in a low (12 ewes/ha; treatment L, n = 124) or in a high stocking rate (84 ewes/ha; treatment H, n = 126). From the beginning of August until the end of August oestrous behaviour was recorded by daily checks of mating marks on ewes. Rams were removed and in October all ewes were scanned (day 50) for pregnancy. No significant differences were found in the parameters investigated. Eighty-two percent of the L and 75.4% of the H ewes exhibited oestrus, with a pronounced peak on day 23 following ram introduction and a compact concentration in the 21-25-day period. The oestrous synchronisation rate in this 5-day period was 69.4 and 68.3%, respectively for L and H. The mean interval from ram introduction to oestrus was 23.17+/-2.4 days in L and 23.0+/-2.2 days in the H group. Conception rates were 84.3 and 87.4% for L and H groups, respectively. These results suggest that the response of anoestrous ewes to the introduction of rams was not affected by grazing space allowances and that yearling Mule ewes respond well to the ram effect in the late anoestrus season. (C) 2003 Elsevier Science B.V. All rights reserved.

The effect of ram replacement and sex ratio on the sexual response of anoestrous ewes

It is accepted that an important source of variation in the response of anoestrous ewes, to the introduction of rams, is the intensity of male stimulation. The aim of this study was to investigate strategies capable of increasing the impact and transmission of the ram stimuli. In Experiment 1, two groups of seven ewes (Bluefaced Leicester male x Swaledale female) were individually penned with one ram and for the next 6 h the rams either remained in the pen or were replaced hourly. Blood samples revealed no difference in the pattern of plasma LH secretion. In Experiment 2, three groups of 16 ewes were either introduced to one ram, individually (H) or in groups of 8 (L), or remained isolated. Ram introduction increased the plasma LH pulsatility (P < 0.001). H ewes displayed more (nine versus six) male-induced LH pulses (pulses occurring within the first 45 min) and more pulses per 8 h intervals than the L group of ewes (1.9 +/- 0.3 versus 1.3 +/- 0.3), but these differences were not significant. It was concluded that (i) frequent replacement of rams within a few hours following ram introduction to ewes does not further improve the response of ewes, especially if the ram:ewe ratio is high; (ii) the characterization of the plasma LH secretion parameters during a period of 6-8 h does not seem to be an effective method to detect small differences in the intensity of stimulation received by the ewes when exposed to rams; (iii) North Country Mule ewes (Bluefaced Leicester male x Swaledale female) in the UK respond to the presence of rams in spring (late oestrous/early anoestrous season) with an elevation in plasma LH secretion. (c) 2005 Elsevier B.V. All rights reserved.

The survival, growth and carcase characteristics of crossbred beef cattle in Tanzania

Sires of seven Bos taurus beef breeds were mated with Bos indicus Boran cows at two sites, one near sea level and the other at about 1000 m altitude, and over three years. Purebred Boran calves provided controls for comparisons between sire breeds for growth to 4 years of age, mortality and carcase characteristics in a range environment where all the animals were kept under a similar management regime. Numerous sire breed x site, sire breed x year of birth and site x year of birth interactions were established. Mortality was high, but there was no significant sire breed effect, although purebred Borans had a higher survival than crossbred calves. There was no significant difference between genotypes in birth weight. Generally, Bos taurus cross steers achieved greater live weight gains and heavier carcase weights at 4 years of age than did purebred Borans. Limousin-cross steers had significantly (p<0.05) less fat in the tenth rib sample joint than any of the other genotypes. A productivity index that combined calf survival and carcase weight indicated that the Chianina crosses were more productive than any other genotype at either site. Purebred Borans were more productive than all the Bos taurus crossbreds with the exception of the Chianina crosses at site 1, but were only superior to the Limousin crosses at site 2, which was at the higher altitude. When lean meat yield was introduced into the productivity index, the Boran purebreds were the least productive at site 2.