It is considered that the rate of glucose uptake by the mammary gland is the main regulator of lactose synthesis (Threadgold and Kuhn, 1984) and hence the main factor determining milk production (Faulkner and Peaker, 1987). GLUT1 is the only glucose transporter that has been found in lactating mammary tissue (Burnol et al, 1990). The aim of this experiment was to determine whether GLUT1 mRNA could be detected in sow mammary tissue, to investigate how abundance of GLUT 1 mRNA in mammary tissue changed between late gestation, early lactation and established lactation, and to establish whether this was correlated with milk output and/or feed intake.

Previous work at ADAS Bridgets aimed at evaluating the Metabolisable Protein (MP) system (AFRC 1992) has indicated that the efficiency of MP use for milk production may be too high, or that the amount of MP required for maintenance may be too low (Newbold et al 1994). This experiment was designed to indicate the true efficiency of MP use for milk protein production when metabolisable energy (ME) and MP supplies were balanced.

It has often been observed that increasing silage DM through wilting increases DM intake, although digestibility and efficiency of utilisation of nutrients tends to decrease, resulting in poor responses in terms of milk yield. Rapid solubilisation of nutrients in the rumen may give rise to rapid nutrient absorption, activating satiety mechanisms and resulting in shorter meals. In the present trial the difference in DM content of the silages was high (>200g/kg). Supplements based on different energy sources were fed to determine whether synchronisation of release of nutrients from the silage and the supplement modified DM intake and feeding behaviour.

Several studies with barley straw (e.g. Wahed et al, 1990) and sorghum stover (e.g. Osafo, 1993) have shown improvements in intake with increasing ‘ad libitum’ amounts offered. Furthermore, these studies have demonstrated that sheep and goats offered barley straw or sorghum stover in long, unprocessed form, increase intake by selecting for leaf and leaf sheath, and against stem. This phenomenon offers a simple feeding strategy to use selective feeding behaviour to improve intake and hence production. The aim of the present experiment was to study the effect of offering increasing amounts of long maize stover on intake and selection by dairy cows.

Six, early- to mid-lactation Ayrshire and Friesian cows (live weight, M, 430 kg) were used in a double 3x3 Latin square design with 24-day (d) feeding periods. Cows were offered long (unchopped) maize stover at low, medium or high ‘ad libitum’ rates, i.e. 31, 59 or 87 g dry matter (DM)/kg M.d. Cows also received 3.2 kg DM/d of cotton seed cake (339 g/kg DM crude protein) in two meals at milking (0700 h and 1800 h). Stover was offered in one meal daily, at 0700 h, after collecting refusals from the previous day. Amounts of stover offered and refused were weighed daily. Samples of offered stover (0.5 kg) and refused stover (0.5 kg) were analysed for DM daily. All refused stover and 4.0 kg samples of offered stover were botanically fractionated, daily, into stem (S), leaf (L), sheath (Sh) and husk (H). Milk yield was recorded daily and cows weighed at the start and end of each period.

Replacement of high starch with high digestible fibre ingredients in the concentrate has resulted in inconsistent effects on silage intake and milk yield and composition of lactating dairy cattle. These differences in animal performance may reflect effects of concentrate energy source on energy utilisation. The present study was undertaken to examine the effect of concentrate energy source on energy utilisation in lactating dairy cows offered a diverse range of grass silages.

Three silages were harvested from perennial ryegrass swards after 39 day regrowth intervals. Silages A and C were produced from primary regrowths and Silage B from a secondary regrowth. Silages A, B and C were ensiled after 24, 0 and 0 h wilting intervals, treated with an inoculant, untreated or an inoculant respectively. Concentrates containing starch concentrations of 50, 209 and 385 g/kg DM, were prepared using barley, wheat, maize gluten, sugar beet pulp and citrus pulp as energy sources. The concentrates were formulated to contain similar concentrations of crude protein, effective rumen degradable protein, digestible undegradable protein, metabolisable energy and fermentable metabolisable energy and were offered at 10 kg/head/d in four equal feeds accounting for 0.57 of DM intake. The diets (3 silages x 3 concentrates) were offered to 18 lactating dairy cows, in a completely randomised experiment, for a minimum period of 28 days prior to the main recording period. Prior to entering open circuit respiration chambers, described by Gordon et al. (1995), cows were housed in individual stalls during a 6 day diet digestibility and nitrogen utilisation study.

Quota restricts the volume and butterfat content of milk at farm level. However there is no restriction on milk protein concentration. In a previous study in the present series, sucrose supplementation of cows in late lactation offered grass silage based diets increased milk protein concentration, while supplementation with sucrose and fishmeal increased protein concentration and the yields of milk, protein and fat plus protein equivalent to, or greater than, that obtained from the parent herbage. The present study was undertaken to evaluate the effects of partially replacing a concentrate supplement with sucrose and/or fishmeal, over a range of concentrate feed levels, on forage intake, milk production and composition.

Herbage was harvested from the primary growth of a predominantly perennial ryegrass sward, unwilted, precision chopped and treated with a formic acid based additive (Add-Safe, Trouw Nutrition) at 2.85 l/t. A concentrate was formulated consisting of unmolassed sugar beet pulp, barley, soyabean meal and minerals and vitamins. Four complete diets were prepared consisting of the silage and either concentrate (20 g/kg fresh silage) (SC), concentrate and sucrose (each at 10 g/kg fresh silage) (SCS) concentrate and fishmeal (each at 10 g/kg fresh silage) (SCF) or sucrose and fishmeal (each at 10 g/kg fresh silage) (SSF).

The effect of pregnancy on the rate of decline in milk yield from month 5 of gestation onwards has been documented for some time, (Brody et al., 1923), and has been a key factor in choice of calving interval. There has been renewed interest in the possibility of extending the traditional 365 day calving interval, because of higher genetic merit cows and difficulties over live calf exports. The objective of the current work was to look for an interaction between pregnancy status and concentrate supplementation.

Sixty-five autumn-calving Holstein-Friesian cows (26 non-pregnant (B) and 39 pregnant (P)) were selected for the experiment; prior to the experiment they were managed on a flat-rate concentrate allocation with forage available ad libitum. The pregnancy-status groups were randomly allocated to receive ad libitum grazed grass and either 0 or 3 kg of 18% crude protein dairy concentrate. The animals were grazed and milked together as one group. The non-pregnant cows were deliberately not inseminated for management reasons (e.g. failure to use Calan gates). During the 10 weeks before imposition of the concentrate treatment, there was no significant difference in milk yield between treatment groups (21.9 (s.e.=1.71) kg/day). The main recording period ran from 10 June until 16 September 1996. Milk yield was recorded daily, milk composition, live-weight and condition scores fortnightly. Data were summarised as means (for milk yield and composition) or slopes (rates of change; for live-weight and condition score (CS; 0-5 scale)) over the period from 3 to 13 weeks after the imposition of the concentrate treatment.

Earlier studies at CEDAR established the positive effects on intake and milk production when forages other than grass were incorporated into dairy cows rations. The area of forage maize and its integration in UK dairy rations continues to increase and as a result has generated considerable interest in supplementation of diets based on maize (MS) and grass silage (GS). The aim of the current study was to determine the effect of using starch (S) and fibre (F) based concentrates on feed intake and milk production of Friesian cows offered a forage mixture of MS and GS in a 3:1 DM ratio.

Forty individually fed multiparous Friesian cows were used in a continuous design study. At week 3 of lactation cows were allocated to one of four treatment groups (Table 1), in which all cows were offered ad libitum access to a forage mixture containing on a DM basis 750 g/kg MS and 250 g/kg GS and 10 kg fresh weight/d of either a starch (229 g starch and 58 g NDF kg/DM) or fibre (85 g starch and 124 g NDF/kg DM) based concentrate. Both concentrates contained 237 g CP and 13.1MJ ME/kg DM and were offered twice dairy in equal quantities.

Dairy cow genetic merit continues to increase in the dairy herd. These animals require a higher level of nutritional input than lower genetic merit cows if higher performance levels are to be sustained. The high cost of ingredients for ruminant diets highlights the need for greater precision in ration formulation in order to improve the efficiency of feed utilisation. This experiment was carried out to assess the effect of DUP supplementation on the performance of dairy cows with ad libitum access to grass silage.

An experiment was conducted to investigate the response by high genetic merit Holstein Friesian dairy cows (PTA90 fat plus protein = 61 kg) to both source and concentration of protein in the concentrate, given in addition to ad libitum grass silage (metabolisable energy (ME) = 10.9 MJ/kg DM; crude protein (CP) = 166 g/kg DM). Twenty-four cows, including 12 first parity animals (mean days calved 37.5, s.d. 22.3), were blocked according to milk yield, calving date and parity. The experimental design was a balanced changeover with four 4-week periods.

Starchy feeds favour the high protein / low fat milk that the market is increasingly demanding, though they place a considerable acid load on the rumen and there is a danger of acidosis at high levels of inclusion. The objective of the present work was to evaluate the use of maize starch, which is perceived to be more slowly and less extensively fermented in the rumen, when compared with wheat starch, in supplements for grass silage.

Thirty-two autumn-calving multiparous Holstein-Friesian cows were balanced for parity and calving date, randomly allocated to the 2 treatment groups and trained to Calan gates during the dry period. Covariance recording on a standard concentrate, was undertaken in lactation weeks 3 and 4 whilst from lactation weeks 5 to 22 cows received one of the 2 concentrate treatments (‘maize’ or ‘wheat’) in a continuous design experiment. Concentrates were fed through the Calan gates at 10 kg/day until lactation week 12 and 7 kg/day from lactation weeks 13 to 22 inclusive in two equal meals at approximately 09.30 and 16.30 h. The concentrates were formulated to be iso-energetic, iso-nitrogenous and iso-starch and balanced for minerals and vitamins. The principal starch sources were (inclusion levels in g/kg as-mixed): maize gluten (230), maize (200), maize germ (123) and barley (75) for the ‘maize’ concentrate; and wheat (425), maize germ (100) and maize gluten (100) for the ‘wheat’ concentrate.

Manipulation of energy- and protein supply during the dry period can affect milk production and composition in the next lactation (Moorby et al, 1996). These studies also demonstrated considerable between-animal variation in responses which may relate to previous nutritional history. This problem was addressed in the current experiment by (i) developing enhanced assessments of animal condition; and (ii) monitoring performance over successive lactations. The second half of the first lactation is a critical phase, particularly for young heifers, since they have to balance the competing demands of pregnancy, growth and a persistent lactation. Berg and Ekern (1993) showed that underfeeding heifers had a residual effect on milk production and composition in their second lactation.

Forty-five Holstein Friesian heifers, which calved from September to December 1994, were selected for this work; 23 of the animals calved at approximately 3 years of age (‘3’), 22 at approximately 2 years of age (‘2’). Thirty-eight animals completed the experiment (to the end of their second lactation) and data from these animals are used here. The animals were maintained on a complete diet until April 1995 when they were offered 8 kg/day of concentrate with ad libitum grass silage for 3 weeks of covariance recording.

Previous work has shown that dry period protein feeding can have important residual effects on the subsequent lactational performance in dairy cows (Moorby et al., 1996), although the results have been variable. This variability may be due to an animals nutrient requirements during late lactation and its ability to compensate during the dry period for previously inadequate supplies. This experiment was designed to investigate the effects of heifer age and level of concentrate offered during the second half of the first lactation on the second lactation performance. The size of the Longissimus dorsi was monitored as a marker of skeletal muscle use for lactation.

Thirty-eight Holstein-Friesian heifers were treated as described by Dewhurst et al. (1997). Briefly, animals were divided into 4 treatment groups differing in age at first calving (2 or 3 years old) and level of concentrate feeding for the last 18-20 weeks of their first lactation (2 kg/d, ‘L’, or 7 kg/d, ‘H’; n=11, 11, 9 and 7 for treatments 2L, 2H, 3L and 3H respectively). Six weeks before predicted calving date, animals were dried off and offered a relatively low quality diet of ad libitum access to a grass silage:straw mix (40:60 on a DM basis), designed to offer them little chance to compensate for previous differences in diet. After calving, animals were offered a diet of ad libitum access to grass silage plus 8 kg/d concentrate to day 120 of lactation, and 5 kg/d thereafter. Live weight was recorded weekly. After calving, milk yields were recorded daily, and milk samples taken weekly, to week 20 of lactation.

Increases in yields of milk and milk protein have been observed from dairy cows offered a high protein supplement during the dry period (Van Saun, Idleman and Sniffen, 1993; Moorby, Dewhurst and Marsden, 1996). One possible mechanism for this is an accumulation of maternal body protein during late pregnancy and its later release during lactation. This experiment was designed to investigate the effect of diet on the potential of dairy cows to accumulate and release body nitrogen over the course of the dry period and the first 20 weeks of lactation.

Twelve multiparous Holstein-Friesian cows were offered one of three diets for 6 weeks prior to calving, with 4 animals per diet, in an continuous design experiment. Animals were offered ad libitum access to A) grass silage only (medium protein), B) a grass silage/barley straw mix (60:40 on a dry matter basis) (low protein), or C) grass silage plus 0.5 kg/d high protein maize gluten meal (high protein). After calving, all animals were offered a standard lactation diet based on ad libitum grass silage plus 10 kg/d concentrate to week 12 of lactation, with 7 kg/d thereafter. Animals were housed in individual stalls for 6 d N-balance procedures on three separate occasions in two groups of six animals: during the dry period (at approximately 3 to 4 weeks before calving), early-lactation (weeks 7 to 8 after calving) and mid-lactation (weeks 17 to 18).

Ruminants may absorb large quantities of ammonia resulting from microbial fermentation and incomplete capture of rumen degradable protein (Huntington, 1984, 1987). Detoxification of this ammonia by ureagenesis in the liver involves the use of aspartate, and although this can be derived from ammonia via glutamate, it may be drawn from the general body amino acid pool. If the latter occurs, the availability of amino acids for milk production may be reduced, leading to a reduction in the quantity and/or quality of milk produced. This experiment was designed to investigate the effect of infusing ammonia into the duodenum of dairy cows on the quantity and quality of milk produced.

Four multiparous Holstein-Friesian dairy cows fitted with duodenal cannulae were given one of two experimental treatments based on duodenal infusions in a changeover design with three periods (the last period of a four period design was not completed). Duodenal infusions were chosen to avoid direct effects on rumen parameters.

Subclinical laminitis syndrome is associated with the appearance of haemorrhages in the sole and white line (Vermunt 1992). Feeding diets with a high proportion of concentrates to forage has been associated with an increased severity or incidence of sole haemorrhages (Weaver 1979; Livesey and Fleming 1984). It is widely accepted that using high levels of starchy feed ingredients may increase the risk or severity of subclinical laminitis syndrome. This experiment was designed to study the development of subclinical laminitis syndrome by feeding diets which differed in starch and fibre content when animals were bedded on chopped straw or wood shavings.

A total of 40 Holstein heifers were divided into 4 groups in a 2 x 2 factorial experiment. The duration of the study was from shortly before calving until 12 weeks after calving. Heifers were housed in cubicles on rubber mats with either chopped straw or wood shavings as bedding.

Providing high levels of nonstructural carbohydrate (NSC) in ruminant diets tends to change fermentation lowering rumen pH and reduce milk fat content. Balancing readily available N and energy-yielding carbohydrate may enhance microbial growth rate, alter fermentation and fibre digestion in the rumen, which subsequently may have an impact on nutrient supply to host animal. Therefore, the objective of this study was to measure the effects of dietary nonstructural carbohydrate and protein level on intake, ruminal fermentation and performance of dairy cows using cassava as main energy source.

Forty-two crossbred cows (60.9% Holstein Friesian, 26.8% Danish Red, 10.2% Red Sindi) at a mean of 71.0 ± 28.5 days in milk (DIM) with a pre-treatment milk yield of 13.2 ± 2.2 kg/d and a BW 373.1 ± 33.4 kg. Cows were tethered in stalls and randomly allocated to receive one of six total mixed ration (TMR) on ad-lib basis. Isocaloric diets (ME 11.2 MJ/kg) were formulated to contain Ruzi grass silage and a concentrate mix (20:80 ratio) containing NSC (30, 35, 40%) in combination with 2 levels of crude protein (15.7, 18.4%).

Cassava (Manihot esculenta, Crantz) is an important root crop in tropical climates for both human consumption and animal feed as a source of energy (ME, R 12.2 MJ/kg). Cassava produces high yields of dry matter and therefore, this study was conducted to evaluate the effects of including cassava as a source of energy replacing to corn on intake, rumen fermentation and animal performance in lactating dairy cows fed a diet based on rice straw.

Thirty-six crossbred cows (˃75% Holstein Friesian) in mid-lactation were randomised to 4 dietary treatments. They were individually tethered and offered ad libitum rice straw together with concentrate twice a day after milking. The diets were iso-nitrogenous (155 g/kg CP). The dietary treatments were concentrate containing 13.5, 27, 40.5 and 54% of cassava replacing corn meal. Milk yield and feed intake were measured daily. Composited milk samples were collected and the components analysed.

A major cause of low silage intake is that some nutrients become available at different times than others i.e. asynchrony of supply. It is possible that, given a choice between foods with different nutrient profiles, animals will take meals at the times that optimise synchrony of supply. The observations reported here examine this concept where lactating cows were given access to concentrates high and low in digestible undegraded protein (DUP).

Six cows in peak lactation and six cows towards the end of lactation were housed in a straw yard where they were offered grass silage ad libitum. Limited access was given to two concentrate feeders containing differently flavoured compounds one high in DUP (28% total protein) and the other low in DUP (18% total protein). Feeders were monitored and controlled according to the LUCIFIR system (Forbes et al., 1986). The two Out of Parlour Feeders (OPFs) were set to dispense 1kg meals.

Slaughter weights for pigs in the United Kingdom have traditionally been much lower than in most other European countries and in North America (Ellis and Avery, 1990). The objective of this experiment was to determine the effect of increasing slaughter weight on growth performance of pigs and on meat quality.

Ninety-six ¾ LR/LW 50 kg live weight pigs were allocated to a 3 x 4 factorial design with eight replicates. The variables were carcass weight which had four levels, 70, 80, 90 and 100 kg (corresponding live weights 92, 103, 114 and 125 kg) and gender with three levels, boars, castrates and gilts. Pigs were individually penned and offered feed ad libitum (DE 13.9 MJ/kg, lysine 10.5 g/kg). Feed intake and live weight gain was recorded over the experimental period and sample joints from the left L. dorsi muscle were obtained at slaughter. Cross sectional area of L. dorsi muscle and fat, lean and bone content of joint was determined and a number of meat quality assessments performed.

Current recommendations for consumers suggest the dietary ratio of n-6 to n-3 polyunsaturated fatty acids should be 5:1. Manipulation of fatty acid profile of pig meat is comparatively straightforward, thus production of pork that approaches the ‘optimum’ is realisable. However, associated with this is a significant risk of deterioration in both keeping and eating quality, following oxidative rancidity. The objective of the trial was to manipulate total n-6 (linoleic, C18:2) and n-3 (linolenic, C18:3) levels of adipose tissue fatty acids, whilst keeping the ratio relatively constant at 5:1, giving levels of 180, 150 and 120g C18:2 /kg adipose tissue with concomitant levels of 36, 30 and 24g C18:3 /kg adipose tissue. Pork (lean) was subjected to physical and biochemical assessment.

Four isocaloric and isonitrogenous diets were formulated. Diets 1 to 3 contained progressively less soya bean oil (42.3, 33.9 and 25.6 g/kg) and linseed oil (8.3, 5.0 and 1.7 g/kg) and progressively more maize starch (0, 30.8 and 61.6 g /kg) with ‘himod’ powder as an inert filler (38.3, 19.1, Og/kg) respectively for diets 1, 2 and 3.