Maize distillers grains (MDG) is a high quality by-product feed containing 317 g crude protein (CP)/kg DM and 13.5 MJ metabolisable energy/kg DM, and as such is a valuable traceable feed resource. An earlier study conducted at the Centre for Dairy Research (Sutton et al. 2000) with cows in late lactation using a total mixed ration (TMR) based on maize silage, compared the protein value of MDG with that of soyabean meal (SB). The study showed that MDG could be used to replace SB on a total nitrogen (TN) basis without effecting feed intake or nutrient digestion in the rumen, or flow of non-ammonia nitrogen to the duodenum. The aim of the current study was to determine the effect of replacing SB with MDG on a TN basis, on DM intake and milk production in high yielding lactating dairy cows.

Traditional options to increase the energy intakes of lactating dairy cows include raising the level of concentrate feeding and/or improving the quality of grass silage. However, each of these options have limited potential to increase total ME intake (Ferris et al., 2000). The inclusion of an additional dietary component, such as whole crop cereal silage or fodder beet constitutes an alternative approach to increase energy intake (Phipps et al., 1995). An experiment was designed to examine the potential of fodder beet to increase the energy intake and performance of lactating dairy cows across a range of levels of concentrate feeding.

The aim was to estimate the influence of genetic merit (£PIN95) and level of concentrate feeding (Cgrp) on predicted total dry matter intake (tDMI) of individual cows, using records collected from commercial farms. The method described by Wicks & Leaver (2000) was used to estimate individual daily dry matter intakes from seven farms, totalling 4282 monthly records over a two-year period. The method was based on milk production records supplemented by body condition scores and height at withers, which were used to calculated the ME requirements of individual animals. All the records were collected, from autumn and winter (July to March) calving cows during the housed period (August to March).

Diets with low ratios of effective rumen degradable protein (ERDP) to fermentable metabolizable energy (FME) are often offered to dairy cows in Portugal, because they are based on maize silage and protein sources are very expensive. It seems likely that this will restrict microbial protein synthesis and voluntary intake and, consequently, lead to reduced milk yields. The objective of this study was to examine the production response of dairy cows offered diets differing in ERDP/FME ratio.

In Iran, the availability of high quality forages is restricted. The use of wheat straw, which is accessible in a huge amount, is limited due to its low nutritional value. Recently, biological method using white-rot fungi to improve the nutritional value of straw have been reported (Zadrazil 1997). However, the data available have been obtained from in vitro works. Additionally, little information is available on the utilization of fungal treated straw fed to dairy cow. Therefore, this experiment was carried out to assess the effect of fungal treated wheat straw on the performance of lactating cows.

The high intake characteristics of red clover silage has been recognised for many years (e.g. Thomas et al., 1985). Our previous study (Dewhurst et al., 2000) demonstrated the considerable intake and milk production potential of clover silages made using a new approach based on preparation of big-bales from wilted material with the use of biological inoculant additives. The objective of this study was to verify the positive results obtained with red and white clover silages using material taken from a further series of cuts taken in a subsequent year and to evaluate the legume silages with low levels of concentrate feeding.

Lucerne (Medicago sativa) is a major, high protein forage fed to dairy cattle. However, during ensiling, much of the CP in lucerne silage (LS) is broken down to nonprotein N (NPN); high levels of NPN in LS depress protein utilisation in lactating dairy cows. Red clover (Trifolium pratense) is a high quality legume forage that can be grown in Britain and Northern Europe. Polyphenol oxidase, an enzyme system in red clover, converts plant phenols into quinones that react rapidly with forage proteins in the silo and result in red clover silage (RCS) having less NPN than LS. Earlier (Broderick et al., 2000), we reported that replacing LS with RCS lowered milk yield but improved feed efficiency and apparent digestibility. Our objective was to compare the production of dairy cows fed equal amounts DM as LS or RCS, with or without maize silage (MS) and supplemental protein added to the diet.

Concentrate supplementation at grass enables the higher genetic merit cow to perform closer to her production potential (McGilloway and Mayne, 1996). Responses to concentrate supplementation are usually greater in late summer and autumn as availability and quality of grazing declines. The objective of this study was to quantify milk production responses when early lactation, high yielding dairy cows at grass, were supplemented with high levels of concentrates, over the late summer period.

Our earlier studies with dry cows have highlighted a number of factors that affect performance in the subsequent lactation, including forage intake in the peri-parturient period, body condition at calving and supply of Metabolisable Protein (MP) (Moorby et al., 1996; Dewhurst et al., 2000). There is now increased interest in making more use of grazed grass, as a cheap feed, particularly through extending grazing into the late-autumn and winter. Dry cows are suited to extended grazing because they do not need to be brought in for milking each day. The high voluntary intakes of grass may be beneficial for dry cows, though the low MP supply from autumn-grass might be a disadvantage. This experiment evaluated the effects of extended grazing, compared with housing and silage-feeding of dry cows.

Considerable effort has recently been directed to better defining protein requirements of dry dairy cows. Early efforts (Moorby et al., 1996) suggested substantial increases in milk and milk protein yield of multiparous cows to a small amount of a high undegradable dietary protein (UDP) supplement in the late dry period. Recent studies have not consistently supported these findings. The objective of this experiment was to define the impact of supplementation of a high UDP supplement in the late dry period of multiparous dairy cows on production of milk and its components.

Considerable effort has recently been directed towards better defining protein requirements of dairy cows approaching parturition. Little effort has been directed towards cows entering first lactation, although Van Saun et al., (1993) suggested modest increases in milk protein production to a supplement of high undegradable dietary protein (UDP) in the late dry period. The objective of this study was to define the impact of supplementation of a high UDP protein supplement in the late gestation of cows entering first lactation on production of milk and its components.

Mansbridge (1995) reported that replacing ground wheat with a mix of ground wheat and maize grain increased milk protein concentration, which led the authors to speculate that increased inclusion of maize grain increased rumen by-pass starch. Indeed, de Visser et al (1990) reported that feeding less rapidly degradable starches has led to increased milk protein concentration.

The objective of this study was to examine the effects of starch concentration and source on feed intake, milk yield and milk composition of dairy cows.

The feed intake of high yielding, early lactation Holstein cows is often inadequate to meet the animal’s requirements for energy and a more concentrated energy source is essential. Oil has a high energy content, so feeds containing oil can help increase the overall concentration of energy in the diet. However, high oil inclusions can lower milk fat and protein level.

The objective of this study was to examine the effects of the addition of increasing levels of oil to a molasses blend (4 kg/cow/day) on feed intake, milk yield and milk composition of dairy cows.

It is well recognised that the fat and protein concentration in the milk of dairy cows is influenced by volatile fatty acids (VFAs) produced in the rumen. There has however been little information available on models to predict milk composition from rumen VFAs in the literature. The objective of the present study was to develop empirical relationships to predict milk fat and protein concentration using rumen VFA data.

Reducing the time available for grazing from 20h to 5h daily, and replacing this with access to a maize silage/soyabean meal diet indoors had no significant effect on milk yield in spring (Hernandez-Mendo and Leaver, 1999). Grazing conditions in autumn present additional problems of shorter daylength and accumulated herbage contamination. The objectives were to examine the production and behavioural responses of grazing dairy cows to reducing access to grazing and increasing access to a maize silage/soyabean meal diet offered indoors.

Empirical models relate nutrient inputs and outputs statistically, without considering the intervening metabolism of the animal (France and Thornley, 1984). Current rationing systems (e.g. ARC, 1980; Jarrige, 1988) are based on empirical models of energy and protein utilisation within the animal and do not enable prediction of responses to changes in nutrient inputs (Beever et al., 1991). Rook et al. (1990) had limited success in attempting to develop empirical regression models to describe the effect of nutrient input on milk constituent yields in dairy cows. The aim of the current study was therefore to use data from the literature to develop more appropriate empirical models that would allow the prediction of response in milk output and its constituent, to changes in energy intake.

Grass silage remains the major forage component of winter dairy rations, yet its intake characteristics are particularly variable. Major research projects at SAC and ARINI over the past few years have produced two large datasets on ad libitum intake of grass silage and shown that improved silage characterisation methods (NIRS and electrometric titration) can substantially improve the accuracy of prediction of silage intake as the sole forage (Offer et al., 1994; Steen et al., 1995). The objective of this research programme was to integrate these two datasets to provide a common prediction system which would be appropriate for adoption across the United Kingdom

Analysis of short-term feeding behaviour may improve our understanding of food intake regulation and diet choice. Feeding behaviour of animals consists of feeding events separated by non-feeding intervals. Feeding events are often observed to be clustered into bouts that may be called meals. Determining a meal criterion (the longest non-feeding interval which is accepted as part of a meal) allows feeding events to be grouped into meals. Tolkamp & Kyriazakis (1999) presented a model that described three populations of loge-transformed intervals in the form of three normal distributions (Gaussians). These populations represent intervals within meals, with or without drinking, and intervals between meals. This model predicted that the probability of a meal starting, first increased, then decreased, with time since the last meal. This is in contrast to the satiety concept, which predicts that the probability of an animal starting a meal will increase with time since the last meal. This study aims at developing a model that best describes, biologically and statistically, the distribution of non-feeding intervals, thus leading to a more accurate meal criteria.

The dietary essential fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are predominantly found in fish oil, but fish consumption in the UK is low. Increasing the yield of EPA and DHA in cows’ milk would increase human intakes of EPA and DHA, and this can be achieved by including fish oil in cows’ diets. However, because EPA and DHA are susceptible to rumen biohydrogenation, their transfer efficiency into milk is low. In vitro observations by Gulati et al. (1999) suggested that if the concentration of fish oil in the rumen exceeded 1 mg/ml, EPA and DHA were not hydrogenated. The objectives of this study were therefore to determine the relationships between fish oil intake by dairy cows, and the probable concentrations of fish oil in the cows’ rumen, with the yield of EPA and DHA in their milk.

In a previous study of forage choice (Syed and Leaver, 2000), cows selected a high proportion of grass relative to maize silage (0.87:0.13). Milk production level of cows and protein level in supplement were not influential in the proportion of forage selected. An understanding of forage preferences by cows should lead to the production of forages with improved intake characteristics. This experiment examined how intake of grass and maize silages offered as a choice compared with intake when offered separately with low or high protein supplements.