Genetic and non-genetic factors influencing KLH binding natural antibodies and specific antibody response to Newcastle disease in Kenyan chicken populations

This study aimed at investigating the influence of genetic and non-genetic factors on immune traits to inform on possibilities of genetic improvement of disease resistance traits in local chicken of Kenya. Immune traits such as natural and specific antibodies are considered suitable indicators of an individual's health status and consequently, used as indicator traits of disease resistance. In this study, natural antibodies binding to Keyhole Limpet Hemocyanin (KLH-NAbs) was used to measure general disease resistance. Specific antibodies binding to Newcastle disease virus (NDV-IgG) post vaccination was used to measure specific disease resistance. Titers of KLH-NAbs isotypes (KLH-IgM, KLH-IgG and KLH-IgA) and NDV-IgG were measured in 1,540 chickens of different ages ranging from 12 to 56 weeks. A general linear model was fitted to determine the effect of sex, generation, population type, phylogenetic cluster, line, genotype and age on the antibody traits. A multivariate animal mixed model was fitted to estimate heritability and genetic correlations among the antibody traits. The model constituted of non-genetic factors found to have a significant influence on the antibody traits as fixed effects, and animal and residual effects as random variables. Overall mean (±SE) concentration levels for KLH-IgM, KLH-IgG, KLH-IgA and NDV-IgG were 10.33 ± 0.04, 9.08 ± 0.02, 6.00 ± 0.02 and 10.12 ± 0.03, respectively. Sex, generation and age (linear covariate) significantly (p < 0.05) influenced variation across all the antibody traits. Genotype effects (p < 0.05) were present in all antibody traits, apart from KLH-IgA. Interaction between generation and line was significant (p < 0.05) in KLH-IgM and NDV-IgG while nesting phylogenetic cluster within population significantly (p < 0.05) influenced all antibody traits, apart from KLH-IgA. Heritability estimates for KLH-IgM, KLH-IgG, KLH-IgA and NDV-IgG were 0.28 ± 0.08, 0.14 ± 0.06, 0.07 ± 0.04 and 0.31 ± 0.06, respectively. There were positive genetic correlations (0.40–0.61) among the KLH-NAbs while negative genetic correlations (−0.26 to −0.98) were observed between the KLH-NAbs and NDV-IgG. Results from this study indicate that non-genetic effects due to biological and environmental factors influence natural and specific antibodies and should be accounted for to reduce bias and improve accuracy when evaluating the traits. Subsequently, the moderate heritability estimates in KLH-IgM and NDV-IgG suggest selection possibilities for genetic improvement of general and specific immunity, respectively, and consequently disease resistance. However, the negative correlations between KLH-NAbs and NDV-IgG indicate the need to consider a suitable approach that can optimally combine both traits in a multiple trait selection strategies.     

Characterisation of smallholder dairy production systems using animal welfare and milk quality

The aim of the current study was to characterise and evaluate production system of smallholder dairy farmers using an index based on combined score of animal welfare and milk quality. Farms were grouped into three categories, tier 1, tier 2 and tier 3. To test the robustness of the characterisation, milk yield (MY), calving interval (CI) and body condition scores (BCS) were used. In the study area, the majority (66.3%) of smallholder dairy farmers practiced cut-and-carry as compared to 15.3% who grazed their cows. The rest combined cut-and-carry and grazing. Cows of farmers in tier 1 had the lowest mean MY (5.4?kg/day, SE?=?0.4), lowest mean BCS (2.1?kg/day, SE?=?0.09) and longest mean CI (603?days, SE?=?27) than farmers in tier 3, mean MY (10.8?kg/day, SE?=?0.6), mean BCS (2.6, SE?=?0.06) and mean CI (404?days, SE?=?17). The study demonstrated that a simple and yet novel method based on farm level indicators can be developed and could assist to timely identify specific problems on the farm.     

Measurement of enteric methane from ruminants using a hand-held laser methane detector

Abstract

This study investigated the effectiveness of the proprietary laser methane detector (LMD) in enteric methane monitoring from individual dairy cows and sheep. Three experiments were carried out. First, the relationship between LMD and indirect open-circuit respiration calorimetric chamber measurements was tested. Sensitivity and specificity for cows were 95.4% and 96.5%. For sheep, sensitivity was 93.8% and specificity was 78.7%. Second, the effect of cow's activity on enteric methane emissions was investigated. During drinking and feeding, cows produced significantly more (p<0.001) methane emissions than when idle. Third, effect of different micrometeorological factors on LMD measurements under outdoor grazing conditions was investigated. Wind speed, relative humidity, pressure and wind direction relative to methane point-source had significant effect on methane measurements (p<0.001) under outdoor conditions. With further validation, the LMD has potential to provide reliable estimates from ruminants and hence provide a useful technique for on-farm monitoring and decision support for greenhouse gas mitigation strategies.     

Multi-country investigation of factors influencing breeding decisions by smallholder dairy farmers in sub-Saharan Africa

Tropical Animal Health and Production - Artificial insemination (AI) and selective bull mating are considered as robust methods for dairy cattle breeding. Globally, these methods have been used to...     

Smallholder dairy production in Northern Malawi: production practices and constraints

Milk production in Malawi is still unsatisfactory despite efforts by different stakeholders to boost the dairy sector. To investigate the roots of the problem, a survey on the current production practices and constraints on smallholder dairy farming was conducted in the Northern Region of the country. A total of 210 farmers were interviewed. The results revealed that farmers had small herd sizes in the region with an average of 2.2 ± 0.6 cattle per farmer. Average herd size was larger in male-managed farms than in female-managed farms (2.6 ± 2.8 vs. 1.8 ± 1.3), farmers with more than 5 years of dairy farming experience had larger herds than those with less experience (2.6 ± 2.8 vs. 1.9 ± 1. 2) and farmers who grazed their animals tended to have larger herds than those that stall-fed their animals (4.4 ± 5.1 vs. 1.9 ± 1.3). Average milk production was 8.2 ± 6.5 l per cow per day. Higher average daily milk production was observed in farmers with above primary school education (10.3 ± 8.3 vs. 7.7 ± 5.6), those with dairy farming as main activity (9.3 ± 6.6 vs. 6. 5 ± 6.1) and farmers with more than 2 years of experience in dairy farming (9.3 ± 6.3 vs. 6.1 ± 6.4). Unreliable supply of improved animal genetics, poor animal health, feed shortage and poor prices for milk were considered to be the most important constraints to smallholder dairy farming in descending order.     

A comparison of milk yields and methane production from three contrasting high‐yielding dairy cattle feeding regimes: Cut‐and‐carry,partial grazing and total mixed ration

There have been reductions in grazing cattle and corresponding increases in mixed diets across many regions. Mixed diets consist of silage, grains, legumes and other herbaceous plants (termed total mixed ration, TMR). TMR has been associated with increased milk yields but has also been linked to increased enteric methane production. We measured milk yields and methane production from high‐yielding Holstein‐Friesian cattle after substituting 29%–36% of a TMR diet with grass. Two feeding treatments were compared with a diet of TMR: grass grazed at pasture and grass cut in the field and delivered to housed cattle (termed cut‐and‐carry). Each feeding treatment was fed to 15 cattle, and the experiment was conducted in South‐west Scotland. Using a laser methane detector, we measured a twofold and fourfold decline in enteric methane production for the cut‐and‐carry and grazing groups, respectively, when the animals consumed grass. TMR was consumed by both grass‐fed groups overnight, so daily values were adjusted to include elevated methane production during this period. This revealed that methane production for the cut‐and‐carry and grazing groups was 17% and 39% lower than for the TMR‐fed group respectively. Milk yields were maintained for all three groups, and the efficiency of milk production per unit of methane was substantially greater for the two grass‐fed groups. A shift away from exclusively feeding TMR by adding fresh grass to the diets of cattle could contribute to meeting emissions targets and could also represent an economically sustainable climate change mitigation strategy.     

Status of dairy cow management and fertility in smallholder farms in Malawi

A review of the smallholder dairy production in Malawi was conducted using livestock annual reports and other literature that was supplemented with primary data from a baseline survey conducted in December 2009. Smallholder dairy farming in Malawi operates with support from institutions that facilitate access to initial stock and dairy production technologies. Most farmers (94%) keep the animals in pens where feed is provided throughout the year. Results indicated unsatisfactory feeding, housing and health management practices, which negatively impact cow fertility. Dairy population trends suggest low replacement rates, which could be associated to low cow fertility and inadequate management skills. There are challenges related to access to breeding and health services, which further contribute to low productivity. Low fertility is evidenced by low calving rates (22–61%) and long calving interval (405–549 days). Existence of programmes on farmer capacity building provides an opportunity for improved management skills and cow productivity. It is concluded that dairy cow management and fertility have challenges and opportunities that are influenced by the extent to which farmers have access to important services such as extension, health, breeding and finance.     

Farmer-preferred traits in smallholder dairy farming systems in Tanzania

Decisions of breeding schemes in many countries in sub-Saharan Africa tend to be either government or project driven, with a focus on upgrading local breeds. However, there is scant information on the individual animal traits that smallholder farmers prefer. The aim of this study was to examine farmers’ preferences of dairy cattle traits using a discrete choice experiment methodology. The study was conducted through visits to 555 randomly selected dairy farms in the sub-humid Eastern coast and temperate Southern highlands of Tanzania. Choices of animal traits were presented to farmers who were asked to evaluate choice alternatives based on attribute levels and finally select the alternative with the highest utility. The choice experiment data were analysed using a conditional logit model. Coefficients for milk yield, fertility, feed requirement, temperament and diseases resistance were overall statistically significant (p?<?0.05). In order of perceived importance, farmers were willing to keep a cow with high milk yield (coefficient?=?1.43?±?0.059), good fertility (0.85?±?0.050), easy temperament (0.76?±?0.066), low feed requirement (??0.56?±?0.092) and enhanced tropical disease resistance (0.48?±?0.048). The purchase price coefficient was negative (??0.001?±?0.0003), indicating that farmers would prefer improved dairy cattle at affordable prices. Farmers’ preferred traits were influenced by agro-ecological zone and type of production system (extensive vs intensive). The study provides an opportunity for breeding programme designers to take farmers’ preferred dairy traits into serious consideration.

     

Current situations of animal data recording,dairy improvement infrastructure,human capacity and strategic issues affecting dairy production in sub-Saharan Africa

An online survey on the state of existing dairy data, dairy improvement infrastructure and human capacity in sub-Saharan Africa (SSA) was undertaken with the aim of assessing whether the state of existing animal recording, dairy improvement methods and key issues facing dairy production together with means of addressing the issues differ among countries and regions of SSA. Respondents comprised experts and practitioners in livestock production and genetic resources from research institutes, animal breeding companies, universities, non-governmental organisations and government agricultural ministries. The main dairy farming system in which the respondents were involved was mixed crop-livestock system (30.2%), and this was mainly practised in the private land tenure system (46.3%). Data were analysed using linear model and paired Student t test in R software package. Respondents identified key issues affecting dairy production as poor genetic assessment of imported exotic breeds and crosses in Africa (62.3%), fluctuations in milk prices within both the formal and informal markets (50.9%), no comprehensive sire ranking systems (39.6%), housing and health management regimes which adversely affect milk yield (32.1%), poor market networks for dairy products (25.5%), poor feeding (13.3%), inadequate genetic technologies (9.4%) and poor animal performance recording systems (9.4%). Respondents emphasised the need for updated breeding policies, sire ranking systems, adequate farm management systems, capacity building, across-country collaborations and joint genetic assessments of dairy breeds found in sub-Saharan Africa. The current situation of dairy production though similar for the different countries, differed in order of emphasis and magnitude across the countries and regions in sub-Saharan Africa.