Dietary starch can increase milk protein and reduce milk fat content, but when fed in single meals may cause problems with rumen stability. To overcome the risk of acidosis, complete diet feeding or reducing the rate of starch degradation (by feeding sodium hydoxide treated whole wheat rather than ground wheat) may provide solutions. In addition, there is evidence to suggest that feeding high levels of cereals alters fatty acid composition of body fat (Garton et al 1972), and similar changes may occur in milk fat.

Ninety six multiparous Holstein cows were fed grass silage to appetite and supplements designed to provide increasing amounts of wheat starch either as wheat ground to pass through a 3 mm screen (GW) or as sodium hydroxide treated whole wheat (STW), prepared by adding 30 kg sodium hydroxide per tonne of wheat plus water to bring the total dry matter to 700 g/kg, and stored for 5 days before feeding.

The study was conducted to examine the response of dairy cows to changes in sources of dietary starch and to investigate whether ‘root’ starch sources are comparable to cereal starch sources in terms of the performance of lactating dairy cows.

Thirty multiparous British Friesian/Holstein lactating diary cows, in a randomised block experiment, were allocated to one of five dietary treatments containing different proportions (1.00:0.00, 0.75:0.25, 0.50:0.50, 0.25:0.75 and 0.00:1.00), respectively, of two dairy concentrates (C or R) which were formulated to the same crude protein (180 g/Kg), ME (11.5 MJ/Kg FM) and starch (300 g/Kg) levels but differing only in the principal sources of starch. Barley and wheat were the principal sources of starch in the ‘cereal’ starch source concentrate (concentrate ‘C’) whilst cassava was the main ingredient in the ‘ root ’ starch source concentrate (concentrate ‘ R ’). All cows were offered the concentrate diet on a flat rate (10 Kg FM/day) with grass silage fed to appetite.

Environmental pressures on the agricultural industry to reduce the use of nitrogenous mineral fertiliser combined with a trend to more extensive systems of production has led to renewed interest in white clover for dairy systems. An EEC funded research project was initiated to investigate whole systems implications with regard to nitrogen efficiency. As part of the project the potential of barley grain or fodder beet as home-grown concentrates to supplement grass/clover silage was investigated.

Thirty early lactation muciparous Holstein Friesian cows were used in a 16 week continuous design experiment lasting from 13 December 1993 to 3 April 1994. The animals were allocated to three treatments on the basis of milk yield, liveweight and days calved. The treatments consisted of ad-libgrass/clover silage supplemented with 5 kg DMd-1 barley grain (B), 2.5 kg DM d-1 of barley grain and 2.5 kg DMd-1 of fodder beet (B/FB) or 5 kg DMd-l fodder beet (FB) daily. All animals received additionally a protein supplement consisting of 3 kg DMd-1 of soya bean meal. The silage was made from the primary growth of grass/white clover sward containing 12% white clover in the DM. The grass/clover herbage, barley and fodder beet were all produced without the use of nitrogenous mineral fertiliser.

Whole crop wheat (WCW) appears to offer an attractive alternative forage to grass silage for dairy cows, particularly in those areas where maize silage cannot be grown. However in previous feeding trials the inclusion of WCW with grass silage has increased food intake but has not led to a corresponding increase in milk yield (Phipps et al,1993). As part of a programme to try to overcome the low efficiency of diets containing WCW, the present experiment was designed to examine the effects on feed intake and digestibility and milk production of the step-wise replacement of GS by urea-treated WCW.

Winter wheat (cv Hussar), harvested at 620g DM/kg fresh weight and preserved with 20 or 40 g urea/kg DM (WCW-2, WCW-4) was compared with first-cut perennial ryegrass silage (GS). Six multiparous Holstein-Friesian cows in mid-lactation were offered six diets over three 4-week periods in an incomplete change-over design. Diets were 6kg DM concentrates daily with forages ad lib. Treatments (DM basis) were GS alone, 2:1 GS:WCW-2 or WCW-4, 1:2 GS: WCW-2 or WCW-4, and WCW-4 alone. Feed intake and milk production were measured in weeks 3 and 4 and digestibility in week 4.

The acreage of maize grown for silage in Ireland has increased in the last few years. This study is concerned with determining it's feeding value relative to grass silage. If energy content is used as the indicator of feeding value, net energy values must be used to allow valid comparisons between feedstuffs. Therefore relative net energy values were calculated for grass and maize silage. However maize silage has very good intake characteristics and this needs to be taken into account in assessing it's value. Relative intake values were calculated for the grass and maize silage's and these were combined with the net energy values to give an overall feeding value.

The control of ovarian function in cattle involves the complex interaction of local and systemic feedback mechanisms. This control system ensures that in greater than 96% of cows only one follicle will ovulate each oestrous cycle. A better understanding of the mechanisms involved should lead to improved synchronisation of oestrus in herds, thereby increasing the success rate of artificial insemination, improve the effectiveness of superovulation regimes and provide opportunities for the induction of twinning. It has been estimated that modest improvements in these areas would benefit the UK cattle industry by at least £200 million per year.

Follicular growth in cattle occurs in a wave-like pattern with usually three waves, sometimes two waves but rarely four waves, of follicles growing and regressing each oestrous cycle. This follicle wave pattern is also present during periods of anoestrus. Each follicle wave, which is usually preceeded by a rise in peripheral FSH concentrations, is characterized by the emergence, from the pool of growing follicles, of a large ‘dominant’ follicle.

Everyone “knows” that stressors have a deleterious effect on fertility. The aim of our work has been to provide definitive evidence for such a statement, and examine the endocrine mechanisms involved. For example, the chronic stressors of periparturient diseases or lameness increase,the intervals from calving to first service or conception, and the number of inseminations required per conception (Table 1).

The economic and biological significance of embryo mortality in cattle is well recognised. About 90% or more ova are fertilised at oestrus but only about 55% of dairy cows calve to first insemination (reviewed by Sreenan and Diskin, 1985). Of this 35% post fertilisation loss, most (25-30%) occurs within a cycle length therefore not affecting the time of return to the subsequent oestrus. It is also accepted that the maintenance of early pregnancy requires the secretion of progesterone by a viable corpus luteum and that premature luteolysis is the major cause of embryonic loss during these early days of pregnancy.

The corpus luteum forms after ovulation from the cells of the granulosa and theca interna layers of the ovarian follicle. These are thought to differentiate into the large and small luteal cells respectively (Smith et al., 1994). The large cells secrete progesterone and oxytocin and are responsive to prostaglandin E whilst the small ones secrete progesterone and are responsive to LH (reviewed by Wiltbank, 1994).

Genetic and phenotypic relationships between performance test and reproduction traits were estimated in a population of Large White pigs, after five generations of divergent selection for components of efficient lean growth rate. The parameters are required to evaluate alternative selection strategies in pig breeding programmes.

Near infrared spectroscopy has been used in a wide range of agricultural sciences as an analytical tool to replace traditional wet chemistry. The current study was designed to investigate its possibilities for use as a technique in determining fatty acid profiles of pig fat.

This study was carried out as part of a larger study examining influences of dietary fat sources on pig carcass and meat quality. Samples of the outer layer of pig fat from 52 animals was freeze dried then extracted with petroleum ether (40-60) for eight hours in a Soxhlet apparatus. This known quantity of fat was dissolved in 50 ml chloroform and a sub sample scanned in to the NIRS (Figure 1 shows a typical spectra). A sample of this chloroform solution was also methylated and the fatty acid profile determined by gas liquid chromatography. Values for each sample were determined for; total weight of fat, weight of: myristic, palmitic, palmitoleic, stearic, oleic, linoleic and linolenic fatty acids, as well as the total weight of saturated fatty acids (myristic + palmitic + stearic), total weight of monounsaturated fat (palmitoleic + oleic) and total weight of polyunsaturated fat (linoleic + linolenic).

The main factors contributing to pork eating satisfaction are considered to be tenderness, juiciness and flavour. Tenderness has been identified as being the most important of these factors in terms of variability and perceived deterioration over recent years. Previous research has shown that the eating quality of meat may be influenced by the balance between the rates of lean tissue growth and fat deposition respectively, and this in turn may be influenced by dietary manipulation and/or genotype and sex of animal. It has been suggested that lean tissue growth rate (LTGR) - influenced by daily liveweight gain - fundamentally affects meat tenderness in pigs (Warkup and Kempster, 1991). In beef cattle studies, faster growing animals have been shown to produce more tender meat (Whipple et al, 1990). Previous work has demonstrated that meat from ad libitum fed pigs tends to be more tender and juicy than restrictively fed pigs (MLC, 1988; Ellis et al, 1990). The objectives of this study were to evaluate the relative importance of lean and fat tissue growth on pork eating quality.

Rates and sites of fat deposition were measured in a population of Large White pigs, after six generations of divergent selection on lean growth rate with ad-libitum (LGA) and restricted (LGS) feeding, lean food conversion (LFC) and daily food intake (DFI).

In recent years, the emphasis on reproductive performance in pigs has increased, although the favourable impact of improving reproductive performance on the overall efficiency of production has long been recognised. There is widespread agreement that increasing the number of pigs per sow per year should be a major objective of the pig industry, particularly as limits in fat reduction are approached. The 1994 British Society of Animal Science Braude Scholarship was used to investigate current research in the area of swine reproduction and identify particular areas of concern as perceived by the North American pig industry. The main objectives of the scholarship were to (1) present a paper at the Fifth World Congress on Genetics Applied to Livestock Production (2) visit research establishments in the USA to discuss current research projects in pigs, with particular emphasis on genetic variation in reproduction traits and (3) visit major pig breeding companies in the USA to discuss the application of research results in modern pig breeding programmes and the required future research.

Predictive models for estimating the nutrient requirements of ruminant livestock have become increasingly complex in their approach, and implicitly they have a need for accurate characterisation of feed degradability kinetics (AFRC, 1992; Russell et al., 1992; Sniffen et al., 1992; Fox et al., 1992). The rumen in situ technique has been adopted as the standard method (AFRC, 1992) for the characterisation of nitrogen degradability in feeds for ruminants. Recent ring tests (Madsen and Hvelplund. 1994) and reviews (Huntington and Givens. in press) have highlighted the need for improved standardisation of the procedure. The aim of this experiment was to determine the effect of sample preparation and incubation sequence on dry matter (DM) losses of fresh grass from polyester bags.

Current rationing systems for sheep and cattle aim to balance a deficit in a basal roughage diet by giving group-fed animals a fixed amount of supplementary food. Assumptions are made that both the intake of basal diet and supplementary feed are average values. Coefficients of variation in individual intake of supplementary feeds of 16-36% have however been observed (Foot and Russel, 1973; Foot et al, 1973) and this variation may be larger (67-107%) where supplements are available as feed blocks (Kendall et al, 1983; Ducker et al, 1981).

Recent work on the selection of feed ingredients by sheep (Kyriazakis and Oldham, 1993) and the effect of physiological factors such as parasitism on diet selection (Kyriazakis et al, 1994) suggest that there may be biological mechanisms behind this variation. Estimation of intake of supplements has been difficult in the past, particularly at pasture using chronic oxide and N-alkane indigestible marker systems owing to the need for complete faecal collection procedures and handling procedures that disrupt grazing. A promising new method using lithium as a marker has been developed in Australia (Nolan et al, 1994). This work was undertaken to evaluate the lithium technique for use under UK conditions to elucidate causes of variation in supplement intake of sheep.

Methane production by ruminant animals is an important anthropogenic source of methane to the atmosphere and is considered an important source to more accurately estimate and to control. Large variations in methane production by ruminants have been reported. However very few of these data were obtained using contemporary diets used in the UK, ie grass silage based diets and were also limited to sheep fed at maintenance (M). This has limited the understanding of the dietary factors which may be used to predict methane production. Attempts to predict methane production from either diet chemical composition or digestibility have not been successful (Moss and Givens, 1990; Johnson et al., 1991). Accordingly, different concentrates were used to supplement grass silage at different rates (forage.concentrate, (F:C) ratios) at differing planes of nutrition to study the effects of diet composition on methane production.

The urinary excretion of purine derivatives has been proposed as a non-invasive method of estimating the outflow of rumen microbial protein. Wider application of this technique is hindered by the requirement for a total urine collection, but Chen et al. (1992) suggested the use of urinary Creatinine(C) concentration to account for changes in urine volume. The relative concentrations of Purine Derivatives (PD) and C in spot urine samples could be used as a suitable index of PD output. The following experiment assesses the validity of this approach in lactating Holstein/Friesan cattle.

Efficient production of high quality milk and beef is dependent on dairy cows and beef cattle receiving the correct intake of nutrients. However the intake of grass silage is very variable and consequently an effective method for predicting the voluntary intake of silage is essential if animals are to be allocated the correct amount of concentrates to provide the optimum input of nutrients. Two changeover design experiments have been carried out with the aim of providing an effective method for predicting silage intake by cattle.

Considerable progress has been made recently in improving the accuracy of prediction of silage intake, when offered as the sole food, to growing cattle (Steen et al, 1995). However, in order to incorporate this information into feed rationing programmes, it is essential to obtain information on how silages of differing characteristics interact when offered with a range of levels and types of supplementary feeds. The aim of this study was to examine the effects of concentrate energy source and crude protein concentration, when offered at a range of feed levels, on the voluntary food of a diverse range of grass silages with both growing beef cattle and dairy cows.

Inaccurate prediction of silage intake is a major source of error in ration calculation. New routine methods such as electrometric titration (ET) and near infra-red reflectance spectroscopy (NIRS) have the potential to improve silage intake prediction (Offer et al., 1994). Development of new advisory models is slow because of the need to do large numbers of intake measurements. It is also essential that models are blind-tested (validated) on data not used for calibration. At SAC, sufficient animal intake data is now available for both calibration and validation although it is intended to continue to accumulate data for these purposes.