Our objective was to provide basic information that can be used to direct sheep production to produce meat, which meets consumer demands. Here, we present the results of a series of studies that were designed to assess the effect of different production systems on carcass quality characteristics of lambs from Greek dairy breeds of sheep.

The Δ9 -desaturase system (steroyl-CoA desaturase) involves the addition of a cis double bond between carbons 9 and 10 of fatty acids. The conversion of stearic acid (C18:0) to oleic acid (cis-9 C18:1) is the predominant precursor:product of this enzyme system; conversion of saturated fatty acids (SFA) to mono-unsaturated fatty acids (MUFA) is important in determining the fluidity of milk. In previous studies (Lock & Garnsworthy 2001), we have shown that more than 50% of the oleic acid occurring in milk is produced in the mammary gland via Δ9 -desaturase. We also found that the conversion of trans-11 C18:1 to cis-9, trans-11 conjugated linoleic acid (CLA) accounted for ~80% of milk fat CLA. Increasing the activity of Δ9 -desaturase offers the opportunity of increasing the MUFA content of milk, especially oleic acid, while decreasing its SFA content, as well as increasing the CLA content of milk. Lock & Garnsworthy, (2001) also reported that there were significant differences between individual cows with regard to milk fat CLA content. In an earlier study (Lock & Garnsworthy, 2000) we found that the CLA content of milk varied throughout the year, with highest values occurring when cows received fresh pasture. In view of the significant contribution of Δ9 -desaturase to the CLA and MUFA content of milk, the objective of the work reported here was to investigate individual animal and dietary variation in Δ9 -desaturase activity in the mammary gland of lactating dairy cows.

Conjugated linoleic acids (CLA) occur in the milk and tissues of ruminants. Although cis-9, trans-11 CLA is an intermediate in the biohydrogenation of linoleic acid in the rumen, duodenal flows of CLA are very low (Scollan et al, 2001) and most CLA appears to be synthesised in tissues from trans-11 C18:1 (vaccenic acid) (Griinari et al, 2000). Trans C18:1 isomers are also produced in the rumen and their amounts are increased when the levels of dietary unsaturated fatty acids are raised. We have investigated the relationship of tissue levels of CLA and trans C18:1 in three breeds of lambs fed supplements of linseed or fish oil to increase trans C18:1.

Conjugated Linoleic Acid (CLA) is a mixture of isomers of linoleic acid implicated with numerous health promoting properties. These include anti-carcinogenicity (cis -9, trans -11 isomer), anti-atherogenicity and increasing the lean:fat ratio (trans -10, cis -12 isomer). CLA is produced naturally by all ruminant animals through the incomplete biohydrogenation of linoleic acid within the rumen. Alternatively, it can be made endogenously by stearoyl coenzyme A desaturase (SCD) from vaccenic acid (VA) (Griinari et al, 2000). It has been well documented that cows fed on a grass diet produce more cis -9, trans -11 in milk than those fed on a concentrate based regime (Kelly et al, 1998) but to date, little work would appear to have been undertaken to determine if this is the case with sheep tissues. In the present study, a grass based diet was compared with a concentrate diet in order to determine whether the CLA content of adipose tissue differed and if so, which isomer and what mechanisms may be involved.

The odour/flavour of beef from animals raised on cereal concentrates differs from that of forage fed animals and this is thought to be caused, at least in part, by differences in fatty acid composition (cereals, high in linoleic acid, C18:2; grass, high in linolenic acid, C18:3). During cooking, the thermal oxidation of fatty acids produces aroma volatiles and intermediates (Mottram, 1991) that modify the Maillard reaction between amino acids and reducing sugars. In this study, we have investigated the reactions that naturally occur in the muscle during cooking by heating together a sugar (ribose), a sulphur amino acid (cysteine) and several unsaturated fatty acids to evaluate the organoleptic contribution of fatty acids to meat aroma development.

Supplementation of animal diets with supranutritional levels of vitamin E is nowadays considered advisable because it extends shelf life by delaying myoglobin and lipid oxidation. However, vitamin E absorption and deposition in ruminants fed on concentrate based diets is reported to be variable. This work examines the effect of concentrate or grass silage based diets on vitamin E concentrations in plasma, muscle and liver and meat quality in lambs.

Boar taint is an offensive odour and flavour in the meat from some (perhaps 0.05) entire male pigs. It occurs when high concentrations of skatole and androstenone are reached in fat tissue. Boar taint is more common in some breeds than others and as part of an investigation into its genetic basis (Doran et al., 2001), we have studied skatole, androstenone and testosterone relationships in Large White and Meishan cross bred pigs.

This study was based on research to identify particular pig breeds, which produce high quality eating pork. Duroc in particular is thought to improve meat quality of progeny when crossed with Large White/Landrace (LW/Lr) hybrid dams by altering the intra-muscular fat (IMF) content of the lean, which is positively related to eating quality (McGloughlin et al., 1988). The extraction of IMF is slow and laborious with harmful solvents involved. Eichinger and Beck (1991) have successfully used NIRS to measure IMF ranging from 1-11% in 39 beef carcases. Ground beef and pork samples have also been predicted for fat, water and protein by NIRS, with prediction errors of 0.82-1.49%, 0.94-1.33% and 0.35-0.70% respectively (Togersen et al.,1999). Instrumental measurements of pork are accepted as indicators of tenderness. Sensory variables such as juiciness, tenderness and flavour are important characteristics for the consumer. Therefore the objective of this study was to explore the potential of NIRS to estimate the chemical, physical and sensory parameters of homogenized fresh pork eye muscle.

Many cases of food-borne illness in the UK are related to the consumption of contaminated meat products. This has highlighted the importance of adopting hygienic procedures throughout the meat production chain, including the farm and abattoir environment (Pennington, 2000). Many factors are known to affect the hygienic condition of finished cattle (Davies et al., 2000) and various husbandry practices may be used to improve cleanliness at slaughter. However, the extent to which abattoir practices contribute to the contamination of cattle hides is not known. Overnight lairage of cattle prior to slaughter is a common practice in the UK, but the extent to which this affects bacterial contamination of the hide remains to be determined. This study investigated the effects of providing additional straw bedding during lairage on the microbiological cleanliness of cattle during overnight lairage.

The use of test day models has increasingly become of interest in genetic evaluation of dairy cattle. Traditionally, in most dairy cattle breeding programmes genetic evaluation of dairy sires and cows has been primarily based on using 305-day lactation yield. Since in this system of evaluation many incomplete lactation records have to be extended to complete lactations this could result in biased prediction of breeding values due to any over or underestimation of total lactation yields. In genetic evaluation of dairy cattle, test day models have many advantages over the traditional method (Lactation Animal Model) because of the fact that they can account for the lactation curve of individual cows and take more accurate account of the effects of environmental factors influencing test day milk yield over the course of lactation. The main aim of this study was to use a Covariance Function Test day Animal Model (CFTAM) in genetic evaluation of first parity Iranian Holsteins.

Milk production is the most important trait in dairy cattle breeding. Measures of additional traits are also important. Traits of lactation curve are important in their relation to production characteristics. The two major reasons for which dairy cows are disposed are fertility problems and low milk yield (Hansen et al.,1983). The objectives of this study were 1) To evaluate effects of some environmental factors on some measures of yield and fertility, and 2) To estimate genetic parameters for these traits applying REML procedures under sire model.

The shape of the lactation curve (description of milk production through lactation) which is relevant in order to predict past, current and future lactations. Curves type I show fast increment during early lactation, followed by a slow decline. However, continuous decreasing curves, named type II (Landete-Castillejos and Gallego, 2000) are frequent in tropical diary cattle, maybe due to low nutritional status (Contreras and Rincon, 1979). Curves type II could not be accurately described by Wood (1967) model. In addition, Wood’s model do not describe the inner processes in the udder. Recently, Pollot (2000) presented a mechanistic model, with 3 components and an inherent biological meaning on its parameters. The objective of the present work was to compare the ability of Wood (1967) and Pollot (2000) models to describe dual purpose cattle lactation curves and provide a first description and analysis of the B. taurus x B. indicus typical lactation curve using Pollot’s (2000) model.

Improvements in management (including health care, preventative strategies and housing design) are one way to decrease the incidence of diseases. However, susceptibility to diseases is heritable and there is interest in selection for disease resitance. Genetic parameters of diseases, such as mastitis and lameness, are required so that these traits can be included in selection programmes. Phenotypes for mastitis and lameness are not expressed on a continuous scale and Gianola (1982) suggested that threshold models are more suitable for such binary traits. Whilst threshold models have been reported as appropriate for the analysis of binary traits they demand more time and greater computing power (Kadarmideen et al., 2000). The objectives of the current analyses were to estimate heritability and repeatability of mastitis and lameness where these traits were treated as binary traits, and to compare the estimates to those obtained in analyses that assumed the traits were continuous (i.e. that ignored the fact that they were “all or nothing” traits).

Pedigree beef cattle breeders who record with the Signet Beefbreeder service have their records analysed by a Best Linear Unbiased Prediction (BLUP). BLUP uses the records (weights and measurements) that have been recorded, for the individual and related animals, to determine the likely performance of an individual’s progeny. The analysis calculates Estimated Breeding Values (EBVs) for several traits of economic value, which are the assessments of genetic merit of the animal. EBVs are calculated for 200 day weight, 400 day weight, fat depth, muscle depth and muscle score. An economic assessment, or index, is calculated using this data, called the Beef Value. The objective of this experiment was to compare the performance of dairy-bred beef calves sired by bulls with either a high (top 10% of breed) or below average (bottom 25%) Beef Value.

Best Linear Unbiased Prediction (BLUP) estimates of breeding values (EBVs) have been routinely used for selection decisions in the UK Meatlinc (ML) population since the early nineteen nineties. This has enabled accurate selection and has allowed higher genetic gains for traits of economic relevance than in other terminal sheep breeds (MLC, 1999). However, concerns regarding increased rates of inbreeding (ΔF) by selecting exclusively on BLUP-EBVs have arisen in this small population. Dynamic rules to maximise genetic merit while ΔF is constrained to a pre-defined level using BLUP EBVs are currently available (e.g. Grundy et al 1998). They found higher gains than standard BLUP selection at the same ΔF by using these rules. The objective of this study was to investigate the potential of these procedures for optimising selection decisions under constrained inbreeding in the UK ML sheep population.

With increasing emphasis in the meat sector on better and more consistent quality, carcass leanness and conformation is now an important issue for sheep breeders. In 1999, only 47% of all carcasses in the UK met the target specifications for weight, fat and conformation (MLC, 2000), highlighting the potential for improvement. In the current stratified crossbreeding system, crossbred wether lambs are a by-product of the production of dam line ewes for the lowland sector. If their carcass quality is sufficient, they can give a valuable boost to the economics of the breeding programme. Genetic improvement of carcass quality in crossing sire breeds would benefit the crossbred wethers, as well as filter through to the terminal sire cross lambs produced by the crossbred ewes. This work aims to assess the influence of selection index and live conformation score of crossing sires (in this case Bluefaced Leicesters) on growth and carcass quality traits of their crossbred progeny, as a first step towards designing a genetic improvement programme for crossing sire sheep.

Recent reviews highlight the importance of the liver in the coordination of nutrient fluxes in support of pregnancy and lactation (e.g. Drackley et al., 2001). Mobilisation of body fat reserves in the late dry period and early lactation leads to an increase in uptake of non-esterified fatty acids (NEFA) by the liver. Their metabolic fate is either oxidation or esterification into triacylglycerides (TAG) that are either exported in very low density lipoproteins (VLDL) or accumulated within liver cells. Recent evidence indicates that TAG accumulation impairs ureagenic and gluconeogenic capacity of the liver, with consequent reductions in feed intake and milk yield, increased incidence of disease and decreased reproductive performance (Overton and Piepenbrink, 1999).

LiFTTM (NuTec Ltd.) is a proprietary mixture of B-group vitamins and methyl group donors (rumen protected choline, niacin, vitamin B12, biotin, folic acid and thiamine) designed to reduce the accumulation of TAG in the liver and accelerate VLDL export. The objective of this experiment was to evaluate the effect of LiFT on milk yield and composition and concentrations of metabolites in blood.

Through the dry period to early lactation the cow goes through a dramatic change in her metabolism. To supply the high energy requirement in early lactation fat supply from the diet and body mobilisation increases substantially. As a result, the liver accumulates fat, the rate of detoxification slows down, ammonia accumulates and there’s a reduced supply of fat, glucose and protein to the udder. This trial was designed to evaluate the response of dairy cows to product called ABN-LiFT a proprietary mixture of B-group vitamins and methyl group donors (rumen protected choline, niacin, vitamin B12, biotin, folic acid and thiamine) designed to reduce the accumulation of triglycerides in the liver and accelerate VLDL export.

The pregnant uterus has a requirement for glucose that rises rapidly towards the end of pregnancy (Robinson et al., 1977). Despite this, the dry matter (DM) intake of the ewe is often depressed during this period causing excessive mobilisation of adipose tissue and an increased concentration of plasma ketones. Propylene glycol resists fermentation in the rumen and following absorption is converted to glucose and glycogen (Andrews, 1982). There is little data available on how in feed inclusion of propylene glycol affects the productivity and energy metabolism of late pregnant and lactating ewes.

Lameness has been identified as an extremely painful condition (Manson and Leaver, 1988). Studies have found increased locomotion score (LS) and lameness to reduce productivity, while other have found no such reduction (Manson and Leaver, 1988; Kelley et al., 1990; Phillips et al., 1994). Changes in time spent feeding have been associated with changes in LS (Manson and Leaver, 1988) and less time lying down (Hassall, 1993). However, while lame cows change their feeding and general behaviour there is little information regarding the extent and mode of these changes. The objective of this study was to measure the effect of locomotion score on behavior and feed intake.