Holstein-Friesian bull calves, although bred for dairy traits, are available at low cost as a potential resource for the beef industry. Finishing of these cattle on intensive feeding regimes has become more attractive in recent years reflecting, inter alia, the reduction in cereal prices and availability of subsidy payments. However, in the future, market-driven economy, production systems must become more efficient if they are to remain viable. The objective of the present study was to evaluate the effect of slaughter weight on production characteristics of Holstein-Friesian bulls offered cereal-based diets, whilst also evaluating the effects of sexual status on performance attributes.

Post Mid Term Review of the Common Agricultural Policy, beef production must survive in a subsidy-free, market led environment. It is essential that producers increase final carcass value by achieving cost effective performance from birth to slaughter. The aim of the present study was to evaluate the effects of plane of nutrition during the growing and finishing indoor feeding periods, and stocking rate and concentrate supplementation at pasture on the performance of steers and heifers from weaning to finishing.

The continuing trend for increased use of Holstein genetics in dairy herds has resulted in a large number of Holstein-Friesian bull calves becoming available, at low cost, as a potential resource for the beef industry. However, whilst these calves have been bred for dairy traits, which are negatively correlated to many important beef traits (e.g. carcass conformation), it is important to determine the potential yield of boned out joints from these animals, in order to facilitate an assessment of commercial carcass value. The objective of the present study was to evaluate the effect of slaughter weight on yield of boned out joints from Holstein-Friesian bulls and steers offered a cereal-based diet.

Performances traits like live weight gain, feed conversion ratio or carcass quality were in the past the main objectives in beef meat production. Nowadays consumers attach an increasingly large importance to technological and nutritional qualities. In terms of dietetic, a low fat content associated with a high polyunsaturated fatty acids content and a low n-6/n-3 ratio is required. In this context, the present work was undertaken to compare performances and meat characteristics in young fattening bulls of 3 beef breeds offered 2 different diets.

Traditionally cereals have been dried or treated with propionic acid and processed prior to feeding to finishing beef cattle. However this process is labour intensive, particularly as it involves rolling or milling the grain prior to feeding. Currently labour is an expensive and scarce resource on many beef units. Recently new techniques have been developed for storing and feeding grain to beef cattle which reduce the need to process grain immediately prior to feeding. The objective of the current study was to evaluate the effects of grain storage and processing method, and grain feed level on performance of beef cattle offered two contrasting feed value grass silages.

Cereal silages are used extensively in the diets of feedlot cattle all over western Canada. Plants are generally harvested at dough stage as this stage is believed to represent the best compromise between feeding value and dry matter yield. However, under the growing conditions of eastern Canada, where cereals are grown as cover crops, it has been argued that harvesting at the boot stage would be beneficial to the establishment of the under sown crop and could improve yields of digestible dry matter. Previous experiments have suggested that cereal silages harvested at boot stage vs soft dough stage (Acosta et al., 1991), although the former were more digestible, resulted in no benefit in terms of animal performance. Our work with grass silages (Berthiaume et al, 1996) showed that this could be due to the highly degradable nature of protein in immature silages, and that protein supplements would be beneficial. This study evaluated the effect of harvesting oats for silage at boot vs milk stage with or without the addition of a protein supplement on nitrogen utilisation and growth of calves.

Adulthood of a dairy cow is reached when she is about 60 months old, but cows first calve at a much younger age. Therefore, most heifers are still growing during their first lactation and part of the energy and protein intake will be assigned to this purpose. As the cow grows closer to mature body weight and is able to use more energy and protein for the milk production, milk production will increase from 1st to 2nd to 3rd lactation, but the amount of increase differs among cows. A gradual production increase is believed to be found in trouble-free cows (i.e. cows with good fertility and high disease resistance), and is a measure of the maturity rate (MR), where maturity is defined as reaching mature body weight. Genetic variance for this production increase exists (Krogmeier et al., 2003). The aim of this study was to define MR in a way that enables selection, and to estimate genetic correlations with functional traits.

In classical quantitative genetic models, phenotypic value depends on genotype, but phenotypic variation among individuals of the same genotype is assumed to be the same for all genotypes. ANOVA and other statistical tests are underpinned by the assumption of a multivariate normal distribution with homogenous variances and independent normally distributed deviations. Heterogeneity of phenotypic or environmental variance has been estimated in dairy cattle (Brotherstone and Hill, 1986). Models and analyses developed by SanChristobal et al. (1998) and Sorenson and Waagepeterson (2003) provide strong evidence for litter size in pigs of heterogeneity of residual variance under genetic control. Environmental sensitivity dependent upon genotype has implications for livestock production, and may explain phenomena such as plasticity and canalisation. The aim was to calculate variability in within family variance among large half sib broiler families, in order to test for the presence of and quantify heterogeneity in residual variation amongst genotypes.

The major selection criterion in the turkey breeding industry is increased breast muscle and body weight in order to adapt to market demands. In female lines a dual selection for both body weight and egg production is performed. However, most published estimates indicate a variable correlation between growth and egg number (Nestor et al., 1996) and so the challenge posed is how to best to select for those opposing goals. The objective of this study was to investigate the effects of simultaneous selection for body weight and egg number by estimating the genetic parameters for a research population held by a commercial company in two different locations.

The mouse is a widely used model in experimental genetics especially for the genetic dissection of fat and lean tissue deposition in farm animals and humans (Bünger & Hill 2005). The body composition of mice has been recently measured in vivo and using carcasses with newly developed technologies and special equipment such as Dual-Energy X-ray Absorptiometry topographic scanners, like the PIXImus series, or micro computed axial tomography scanners (Medlin 1999). These methods, although accurate, are still relatively expensive. The aim of this study was to assess whether a computerised tomography (CT) scanner designed for scanning of humans, was capable of providing sufficiently accurate estimate of the body composition of mice of different lines, to prepare the ground for studies in mice as model animals to fast-track experiments in farm animals in a cost-effective way.

Small ruminant studies have shown that a reduction in protein scarcity, through either an increase in protein supply or reduction in protein demand, results in reduced nematode egg excretion and worm burdens during the periparturient period (Houdijk and Athanasiadou, 2003). Whilst this reduced degree of parasitism indirectly suggests that such nutritional effects are mediated through changes in host immune responses, there is only limited direct evidence for this. A rodent model may be used for directly assessing immune responses that underlie nutritional control of nematode parasites. There is indirect evidence that lactating rats undergo a breakdown of immunity to the intestinal nematode Nippostrongylus brasiliensis (Houdijk et al., 2003). Provided that this breakdown is sensitive to protein nutrition, this model may be used for elucidating interactions between nutrition and immunity to parasites. Therefore, we assessed whether breakdown of immunity to N. brasiliensis in the lactating rat is sensitive to host protein nutrition.

A recent study carried out by Houdijk et al (2005), used a rodent model to assess whether a reduction in protein scarcity during lactation resulted in a reduced degree of parasitism. Feeding high protein foods resulted in a reduced worm burden, but was confounded with increased food intake per se. Therefore, effects observed on parasitism may not necessarily have been associated with an increased protein supply, but with changes in the gut environment due to the increased food intake. Before this model can be used to assess the underlying immune responses, further work is needed to verify that the effects observed are indeed related to changes in nutrient supply. This experiment aimed to provide further evidence on the nutritional control of parasitism during lactation by manipulating nutrient demand. It was expected that the latter would not be associated with changes in food intake per se and results could therefore be used to exclude the influence of non-immunological changes in the gut environment as a contributing factor of reduced parasitism.

All genetic selection in dairy cattle is applied to traits that are measured during the animal’s productive life, mostly those recorded during early productive life because genetic evaluations are best calculated from unbiased early data. Since body lipid is normally accumulated partly as a function of body protein accretion and in part as a function of degree of maturity (which is also related to protein content), it follows that selection for yield in relatively mature life, and concomitant alteration of body lipid profiles, may have altered early life growth profiles as well. If this is the case, parameters of early life growth may be used to predict later life events such as production and functional traits associated with the degree of maturity when these events occur. The objectives of this study were: 1) to model the growth of dairy cows of average and high genetic merit from birth to the end of third lactation and identify any differences in their growth curves.

Changes in body condition score and other linear type traits can be indicative of changes in body energy balance in dairy cattle (Coffey et al., 2003). As an animal proceeds through her lactation it is expected that body shape and fatness levels will change both with peaks and troughs of lactation as well as changes as the animal grows and matures. Wall et al. (2005) showed that udder support (US) was correlated to fertility; cows with weaker udders had poorer fertility. If there are differences between animals in terms of how their udders grow and mature across the first lactation, this could be indicative of health and fertility problems later in life. The aim of this study was to examine how type traits recorded in the national dairy population change over the first lactation and if there is a difference between sires in the type profiles of their daughters.

Pathogens (parasites, bacteria and viruses), when causing sub-clinical disease, affect the voluntary food intake, VFI kg/d, of animals, with subsequent reductions in rates of growth. However, no general quantitative framework for predicting the effects of different kinds and doses of pathogen on the VFI of animals has been proposed that could be integrated with existing models of growth. The aim here was to develop a general quantitative framework of VFI during exposure to sub-clinical doses of pathogens and to integrate such a framework with a general model of growth (Wellock et al. 2003).

Food intake (FI) can be predicted on the basis of variables that describe food quality and the animal. Live weight (LW) is usually the only variable that is used to describe the animal. Animal fatness, as estimated by condition score (CS), can affect FI at a given LW. Body lipid produces signals (leptin) that affect energy intake and energy expenditure. If fatness acts on intake via its effect on energy expenditure, the effects of body lipid content on food intake can be incorporated into an existing intake model. Our objectives were to construct and test models that predict effects of fatness on intake and performance, using data obtained with ewe lambs to parameterise and test the models.

Productivity in pigs can be improved by continued selection, however the impact of such selection on immune responses and resistance towards infectious challenges is not known. A risk is that this method may lead to a correlated reduction in the immune response and disease resistance. To estimate the effect of selection for performance traits upon immune responses, we compared levels of immune traits between divergent lines of Large White pigs selected for either lean growth under restricted feeding or feed intake.

The accurate prediction of body composition of dairy cows is important for developing appropriate nutritional and management regimes. The objective of the present study was to develop prediction equations for empty body (EB) composition of lactating dairy cows using body weight and other live animal data.

Body condition of lactating dairy cows varies at different stages of lactation. Cows usually mobilise their body reserves to provide energy and protein for milk production in early lactation, and gain weight to deposit energy and protein for pregnancy at a later stage. The objective of the present study was to examine relationships between body condition score (CS) and body concentration of lipid, CP and energy.