To investigate the extent to which enteric methane (CH4) emissions from growing lambs are explained by simple body weight and diet characteristics, a 2 × 2 Latin square changeover design experiment was carried out using two sheep breeds and two fresh pasture types. Weaned lambs of two contrasting breed types were used: Welsh Mountain (WM, a small, hardy hill breed) and Welsh Mule × Texel (TexX, prime lamb) (n = 8 per breed). The lambs were zero-grazed on material cut from recently reseeded perennial ryegrass and extensively managed permanent pasture. In each experimental period, individual ad libitum dry matter intake (DMI) was determined indoors following an adaptation period of 2 weeks, and CH4 emissions were measured individually in open-circuit respiration chambers over a period of 3 days. Although total daily CH4 emissions were lower for the WM lambs than for the TexX lambs (13·3 v. 15·7 g/day, respectively) when offered fresh forage, the yield of CH4 per unit DMI was similar for the two breed types (16·4 v. 17·7 g CH4/kg DMI). Total output of CH4 per day was higher when lambs were offered ryegrass compared with permanent pasture (16·1 v. 12·9 g/day, respectively), which was probably driven by differences in DMI (986 v. 732 g/day). Methane emissions per unit DMI (16·4 v. 17·7 g CH4/kg DMI) and proportion of gross energy intake excreted as CH4 (0·052 v. 0·056 MJ/MJ) were both higher on the permanent pasture. No forage × breed type interactions were identified. The results indicate that forage type had a greater impact than breed type on CH4 emissions from growing weaned lambs. It can be concluded that when calculating CH4 emissions for inventory purposes, it is more important to know what forages growing lambs are consuming than to know what breeds they are.

Animal production is a fundamental component of the food supply chain, and with an increasing global population production levels are set to increase. Ruminant animals in particular are valuable in their ability to convert a fibre-rich forage diet into a high-quality protein product for human consumption, although this benefit is offset by inefficiencies in rumen fermentation that contribute to emission of significant quantities of methane and nitrogenous waste. Through co-operation between plant and animal sciences, we can identify how the nutritional requirements of ruminants can be satisfied by high-quality forages for the future. Selective forage plant breeding has supported crop improvement for nearly a century. Early plant breeding programmes were successful in terms of yield gains (4% to 5% per decade), with quality traits becoming increasingly important breeding targets (e.g. enhanced disease resistance and digestibility). Recently, demands for more sustainable production systems have required high yielding, high-quality forages that enable efficient animal production with minimal environmental impact. Achieving this involves considering the entire farm system and identifying opportunities for maximising nutrient use efficiency in both forage and animal components. Forage crops of the future must be able to utilise limited resources (water and nutrients) to maximise production on a limited land area and this may require us to consider alternative plant species to those currently in use. Furthermore, new breeding targets will be identified as the interactions between plants and the animals that consume them become better understood. This will ensure that available resources are targeted at delivering maximum benefits to the animal through enhanced transformation efficiency.

Twenty-four twin-bearing mature Mule ewes were used to evaluate the effects of feeding ensiled red clover (Trifolium pratense), lucerne (Medicago sativa) or perennial ryegrass (Lolium perenne) during late pregnancy on subsequent ewe and lamb performance. Eight weeks prior to lambing the ewes were individually penned and offered one of the treatment forages ad libitum (no. = 8 per silage). All ewes were supplemented with molassed sugar-beet shreds to avoid dietary energy being a limiting factor and to ensure the responses were primarily attributable to the forage protein content. Individual intakes of the ewes were determined daily and weekly measurements of ewe live weight and body condition score were made. The ewes were also scanned weekly for depths of subcutaneous fat and longissimus dorsi (LD) muscle. Blood samples were taken at 6, 4, 2, and 1 week(s) before lambing, 24 h after lambing and at 3 weeks after lambing and were analysed for serum concentrations of total protein (TP), albumin, urea, beta-hydroxybutyrate (BHB) and plasma concentrations of glucose and non-esterified fatty acid (NEFA). After lambing all ewes and their lambs were turned out to graze together on a ryegrass sward. The lambs were weighed at birth and at weekly intervals thereafter until 12 weeks post partum. The lucerne silage offered had a higher dry matter (DM) content than the red clover and ryegrass silages (367, 305 and 314 g DM per kg fresh matter, respectively; P < 0·001). Forage type significantly affected crude protein (CP) concentration (240, 215 and 182 g CP per kg DM for lucerne, red clover and ryegrass silages, respectively) and metabolizable energy (ME) density (11·1, 11·6 and 10·8 MJ ME per kg DM respectively). Ewes offered the legume silages had higher intakes of DM, CP and ME than ewes offered ryegrass silage (P < 0·05), which was reflected in higher ewe live-weight gain (P < 0·05) but not in litter birth weight (P > 0·05). Silage treatment affected serum concentrations of TP, albumin, globulins and urea during the last 4 weeks of pregnancy (P < 0·05). Lambs born from ewes offered lucerne and red clover silages prior to lambing had higher growth rates from birth to 3 weeks of age than those from ewes offered ryegrass silage (320, 323 and 282 g/day, respectively; P < 0·05). Lamb live weight at 12 weeks of age was higher for lambs from ewes that had been offered the red clover silage, at 29·1 kg compared with 26·7 and 27·1 kg for lambs from ewes previously offered lucerne and ryegrass silages (P < 0·05). In conclusion, the results showed that red clover and lucerne silages are better able to meet nutrient requirements of ewes in late pregnancy than grass silage.

The lactation cycle of the dairy cow induces large changes in body fat and protein pools, which can be monitored through loin backfat (BF) and longissimus dorsi (LD) measurements. Data from two experiments (exp) using Holstein-Friesian dairy cows (no. = 40 and 32 respectively) were used to study the association of body weight (BW), BF and LD depth with body condition score (BCS) for the last 6 weeks of the dry period (DP) and the first 8 weeks of lactation. Loin and tail BCS were manually assessed (0 to 5 scale) and BF and LD depth were measured by ultrasound at the fifth lumbar process. The BCS data ranged from 1.3 to 3.0 units in the DP, and from about 1.1 to 3.1 units during early lactation in both experiments. Data were analysed by two models: BW, LD or BF = exp + period (DP or lactation) + BCS + interactions + cow + error (model 1); and BCS = exp + period + LD + BF + LD2 + BF2 + exp × LD + exp × BF + exp × LD2 + exp BF2 + period × LD + period × BF + period × LD2 + period × BF2 BF2 + cow + error (model 2).

A first-order autoregressive (AR(1)) covariance structure was employed for the error terms to account for the correlation among repeated measures within cow. Regressions of BW and LD on BCS (model 1) found pre- to post-calving differences (P < 0.001) in intercept for BW and LD, and slope coefficients of 35 (DP) and 21 (lactation) kg BW, and 5.8 mm LD per BCS unit. Regression of BF on BCS (model 1) showed an exp × period interaction (P < 0.001), with 0.4 mm BF (exp 1; P < 0.05) and 2.0 mm BF (exp 2; P < 0.001) per BCS unit. Regression of BCS on LD and BF (model 2) showed intercepts not equal to 0 (P < 0.06), and differences (P < 0.001) between DP and lactation; BCS increased (P < 0.001) by 0.027 units per mm BF and 0.05 units per mm LD, but LD had a quadratic term −0.0004 (P = 0.02). It is concluded that at BCS lower than 3, LD contributes to BCS following a quadratic function, whereas BF causes BCS to increase linearly. Each unit of BCS equated to about 35 and 20 kg BW for DP and lactation periods respectively, to 5.8 mm LD, and to between 0.4 and 2.0 mm BF.

Grazing experiments have shown that using a ryegrass (Lolium perenne L.) variety bred by conventional techniques for high water-soluble carbohydrate (WSC) concentrations can improve liveweight gain in pre-weaned lambs (Lee et al., 2001) and increase milk yields and reduce N excretion in dairy cows (Miller et al., 2001) compared to conventional ryegrass. The aim of this study was to determine the effects of using reseeded upland pastures, sown with either a ryegrass variety bred for elevated levels of WSC or a control ryegrass on the production performance of grazing steers when compared to steers grazing permanent ryegrass/white clover pastures.

Perennial ryegrass varieties bred to express high water-soluble carbohydrate (WSC) concentrations have been shown to improve liveweight gain in pre-weaned lambs of grazing ewes (Lee et al., 2001) compared to conventional ryegrass. Studies have shown that the largest differential in WSC between ryegrass varieties bred for high WSC concentrations and control ryegrasses occurs 5-6 weeks after the plant is allowed to re-grow following cutting or grazing (Miller et al., 2001). Therefore, the benefits, in terms of lamb performance, of using these grasses with high WSC concentrations may be best achieved when they are rotationally rather than continuously grazed. The aim of this experiment was to compare lambs rotationally or continuously grazing either a ryegrass variety bred for high WSC concentrations or a control ryegrass.

To investigate the effect of red clover formononetin concentration on lamb growth rate and carcass characteristics, 20 lambs (10 ewe lambs and 10 wethers) were grazed on each of three forages : red clover with a high formononetin concentration (HF), red clover with a low formononetin concentration (LF) and a control perennial ryegrass. Animals were finished at condition score 3L, at which point half of all animals were slaughtered immediately, while the other half of the animals were moved to a common ryegrass plot for 3 weeks as a 'withdrawal' period. Mean formononetin concentrations were 0-0, 4-7 and 3-3 g/kg dry matter (DM) for grass, HF and LF swards respectively. The clover swards had higher crude protein concentrations and lower fibre and water-soluble carbohydrate concentrations than the control ryegrass sward. Lambs grazing the HF clover gained 40 g/day live weight more (P < 0-1) than lambs on the other two forages without an increase in forage DM intake as estimated using the nalkane technique. There was no difference in the empty body weight, killing-out proportion, carcass fat class or condition score between animals finished on any of the three forages. Following the 3-week withdrawal period on ryegrass, there were significant residual effects of previous grazed forage on carcass weight, with HF lambs producing heavier carcasses than other lambs. Plasma concentrations of growth hormone and insulin-like growth factor-1 were highest in lambs grazing the HF clover, and suggest a physiological mechanism for the increased growth rates of these animals. There were no differences in the equol contents of the meat of lambs finished on the clover, compared with animals finished on grass, suggesting that there would be no implications for human health following consumption of meat produced from lambs grazing red clover, even with a relatively high concentration of formo'nonetin.

Nutritional regime during the dry period (DP) has been shown to affect lactational performance in dairy cows. These responses could be mediated by a variety of mechanisms (e.g. increased labile body proteins, function of the mammary gland or the liver, or modifying endocrine status), which are likely to exert an overlapping function.This study analysed the effect of protein (P) and/or fat (F) supplementation in the DP on plasma metabolite and hormone concentrations, as a complement to studies on body composition (Jaurena et al. 2001b.) and subsequent milk production (Jaurena et al., 2001a.) performance. Other results also associated with this work are presented in Jaurena et al. (2003).

Despite many promising characteristics as a low-input home-grown protein source, red clover (Cv) silage supplies deficient amounts of rumen available carbohydrates to allow an efficient use of the available forms of soluble N. An in vitro experiment was designed in order to determine the optimum rate of inclusion of a rumen degradable carbohydrate source to optimise rumen microbial N yield of Cv silage.

The association among feeding, body fat reserves, plasma leptin concentration and intake has been indicated in many reports, however the characteristics of these associations in late pregnant ruminants is not yet completely clear. As part of a larger experiment concerned with nutrition during the dry period (DP), a study was undertaken to identify the relationship between precalving fat and protein supplementation with plasma leptin concentration and the association of leptin with fat reserves and dry matter intake (DMI) during the periparturient period. Further results associated with this experiment were reported elsewhere (Jaurena et al., 2001a.,b; Jaurena et al., 2003).

Eight Hereford ✕ Friesian steers were used to investigate the effect of feeding Lolium perenne (L) forage containing elevated levels of water-soluble carbohydrate (WSC) on rumen metabolism and nitrogen (N) absorption from the small intestine. The steers were offered ad libitum access to one of two varieties with matched heading dates (Ba11353, high WSC, HS; AberElan, intermediate WSC, control) cut at different times of the day to accentuate WSC differentials, zero-grazed for 21 days. This was followed by a 14-day period where the animals were on grass silage to provide a covariate intake. Although the total N concentration was similar for the two grasses, all other measured values were significantly different. The dry matter (DM) concentration of HS was greater than that of the control (202 v. 167 g DM per kg; P 0·01). WSC and in-vitro dry matter digestibility (IVDMD) were 243 and 161 g/kg DM, and 0·61 and 0·56 for HS and control, respectively. In contrast, acid- and neutral-detergent fibre were 251 and 296 g/kg DM and 480 and 563 g/kg DM for HS compared with control, respectively. DM intake was increased (9·3 v. 6·7 kg/day; P 0·001) for HS animals and this contributed significantly towards higher flows of non-ammonia N to the duodenum as well as increased absorption of amino acids from the small intestine. This DM intake response was partly due to the elevation in DM concentration of HS. However fresh weight intake was increased proportionately by ca. 0·15 (P 0·05) in animals on HS compared with control. Rumen ammonia levels were lower (14·0 and 26·4 mg N per l; P 0·001) and concentrations of rumen propionate higher (P 0·01) and acetate lower (P 0·01; increasing the glucogenic: lipogenic volatile fatty acid ratio) in animals on HS compared with control. However, the efficiency of microbial protein synthesis (15·9 and 17·8 g microbial nitrogen per kg organic matter apparently digested) and flow of N to the duodenum per unit N intake (0·84 and 0·93) for HS and control, respectively, were similar across both diets.

Previous results have shown that during late gestation even under conditions of live weight (LW) gain, maternal body protein can be in negative balance due to the highly demanding gravid uterus and udder. It has also been claimed that current feeding standards underpredict dry cow nitrogen (N) requirement. Considering that it is not possible to measure maternal body N status independently of the requirements of the conceptus and the udder, estimation of conceptus and udder N requirements by mathematical models can help to predict maternal N requirement. The aim of this study was to assess cow N requirement during late gestation by predicting maternal N balance through a mathematical model. Previous results related with this study were presented in Jaurena et al, (2001).

Energy and protein supply during the dry period can affect subsequent milk production and composition (Moorby et al., 1996). Grass silage is a common ingredient of dry cow diets, but although it is usually adequate in crude protein concentration (CP), a high proportion is frequently in non-protein forms. Red clover silage has shown interesting characteristics that would increase true protein supply to ruminants (Broderick et al., 2000), which could avoid the use of more expensive concentrate supplements. The objective of this experiment was to compare red clover and ryegrass silage when fed as the sole source of forage to dry cows with a diet comprising ryegrass silage and a protein supplement.

Genetic potential for milk production has increased rapidly in the Holstein-Friesian breed and there is concern that this might be causing an increased incidence of health problems. We have recently (Ingvartsen et al., 2002) reviewed the inter-relationships between lactation performance and health, demonstrating the importance of considering effects on/of body reserves as well as effects on/of milk production. Whilst we identified mechanisms whereby body reserves can have a direct effect on susceptibility to disease, disease also affects body reserves making it difficult to study their inter-relationships. The dry period is a particularly interesting period in this regard, because additional nutrients are directed towards reserves, whilst it is followed by a period (early lactation) of high disease incidence. The objective of this study was to investigate the effects of body condition score (BCS) at calving, as well as the effects of dry period diets designed to alter BCS, on disease incidences in the first 100 days of lactation.

Nutritional manipulation during the dry period can alter subsequent animal responses to feeding in terms of milk yield and composition. Previous research has shown interesting differences in milk production and composition due to energy or protein supply in the dry period (Moorby et al., 1996). The objective of this experiment was to test the interaction between energy and protein supplies during the dry period on subsequent milk production and composition. Effects on live weight gains and condition scores are reported in a separate summary (Jaurena et al., 2001).

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.

There is increasing interest in the use of red clover (Trifolium pratense) as a high protein forage crop to finish growing lambs. Red clover contains the isoflavanoid compound formononetin which is converted to the non-steroidal oestrogen analogue equol by rumen micro-organisms. Equol is absorbed by the animal, and can have significant effects, such as suppressing reproductive cycling in ewes. Very few commercial red clover varieties have been bred with a low formononetin content to prevent this problem. Although human health benefits have been linked to the consumption of oestrogenically active compounds in foods such as soya (Kurzer and Xu, 1997), there is a need to investigate the presence of oestrogenically active compounds in animal products. The objective of this study was to investigate plasma metabolite and hormone concentrations, and the residual levels of equol in meat, of lambs grazing two varieties of red clover differing in their formononetin contents, compared to control animals grazing grass.