Two groups of six male goats were used to assess the effects of rumen-protected supplements offish oil on intake, digestibility and nitrogen (N) balance. The animals were offered a diet consisting of forage and concentrate, the latter fraction supplemented with 0 (control) or lOOg/kg of rumen-protected fish oil supplement (PFO), containing a high proportion of the n-3 series (whole diet contained 0 or 60 g PFO per kg dry matter). No significant differences (P > 0.05) were found between the two groups concerning live-weight gain, food intake, digestibility of DM, organic matter, N, neutral-detergent fibre and energy. In contrast, there were differences (P < 0.05) regarding the digestibility of fat and of acid-detergent fibre, which were higher among the animals given the PFO diet. With respect to the individual fatty acids, we observed higher digestibility (P < 0.05) of C14:0, C16:0, C18:0 and C20:0 among the animals given the PFO diet. The digestibility of C14:0, C18:0 and C20:0 was found to be negative among the animals given the control diet. No significant differences (P > 0-05) were found regarding digestibility of total C18:1. In contrast, the coefficients for C18:2 (n-6) and C18:3 (n-3) were higher (P < 0.05) among the non-supplemented animals. The intake and faecal flow values of C18:0 suggest that the mono- and polyunsaturated fatty acids with 18 atoms of carbon may, in both cases, undergo partial hydrogenation, which would be greater among the control group. The utilization of C20:5 (n-3) and, especially, of C22 : 6 (n-3), which were consumed only by the animals given the PFO diet, was estimated at 1-000. The PFO diet also produced lower levels ofurinary-N excretion (P < 0.05), giving rise to higher N balances (P < 0.05).

A heat balance model was combined with a food intake model and a metabolism model, to form a larger model which estimates a pig’s response to heat stress. The combined model was implemented as a computer program, and used to calibrate, test and validate parts of the heat balance model. Heat transfer modes considered were convection, radiation and evaporation of water at the skin, and heating and humidification of air by breathing. Sensitivity analysis revealed a large effect of air temperature, humidity and velocity on heat loss, especially in a hot environment. It also showed that wetting of the pig’s skin is the most effective means to alleviate heat stress. The calibration procedure confirmed that characteristics related to heat tolerance in pigs must be re-evaluated, due mainly to the changes brought about by genetic improvement (such as reduced backfat thickness). The model was challenged using two different data sets. Although simulated results varied in the same way as measured data, more research is needed to determine more precisely some of the parameters. Long-term predictions were more reliable than those for short (1-day) periods.

Two experiments were carried out to quantify the intake of mineral blocks by ewes in group- and individually fed situations, and to examine the effects of mineral block intake on food and water intake, colostrum production and lambs' immunoglobulin G (IgG) absorption when ewes are individually housed and offered maize or grass silage with a concentrate supplement. In experiment 1, mineral blocks were offered to 359 ewes either when grazing at mating time (no. = 200) or, when indoors in the last 4 or 7 weeks of pregnancy, the latter as either twin-bearing ewes that were group-fed (no. = 18) or individually fed (no. = 27) or single-bearing ewes that were group-fed (no. = 114). Block intake was measured on a weekly basis. In experiment 2,a2X2 X 2 factorial design was used to compare the effects of forage (grass or maize silage), restricted mineral block access and added minerals/vitamins in the concentrate on food and water intakes, colostrum production and immunoglobulin absorption by the lamb using 64 twin- bearing ewes that were individually housed. Grass silage and maize silage were offered ad libitum, concentrates were offered at a flat rate of 400 g per head per day. Mineral blocks were offered to ewes for 3 h/day. Following lambing, the ewes were hand milked at 1,10 and 18 h post partum. Colostrum samples were assayed for immunoglobulin G (IgG) content. Lambs were blood sampled at 24 h old to determine serum IgG value. In experiment 1, mean daily mineral block intake per ewe was lowest at mating time (19 g) and highest when ewes were individually housed (194 g). In experiment 2, intakes of dry matter(DM) and energy were higher (F < 0.05) in the maize silage treatments. Similarly, when ewes had access to mineral blocks they had higher (P < 0.05) intakes of DM, energy and protein in addition to having a higher water intake (2.24 v. 0.771 per ewe per day; s.e. 0.139; P < 0.01). The mean total colostrum yield to 18 h post lambing at 1734 ±98.0 ml was unaffected by any of the treatments. When ewes had access to mineral blocks their lambs had lower (6.8 v. 18.8; s.e. 1.48; P < 0.01) serum IgG values and the efficiency of IgG absorption from the colostrum into the blood stream was reduced (0.097 v. 0.247; s.e. 0.0214; P < 0.01). In conclusion, the data show that there is wide variation in mineral block intake in different situations and that intake of some minerals can exceed toxic values. Additionally, when individually fed pregnant ewes have access to blocks for just 3 h/day, there is a significant increase in water intake and a dramatic reduction in lamb serum IgG concentration and in the efficiency of absorption of colostral IgG into the blood. We suggest that while mineral blocks can confer advantages in specific situations, there is the need to revisit their formulation and to further research the mode of action responsible for the compromised IgG absorption.

Grass silage constitutes a major proportion of the food offered to high producing dairy cows in the western regions of the European Union. In order to achieve optimal milk yield and quality from high genetic merit dairy cows, it is common practice to offer concentrates in addition to grass silage at feeding. The aim of the current study was to combine two existing empirical models in order to allow prediction of the response in milk production to offering varying ratios of grass silage and concentrates to high genetic merit dairy cows, allowing for the fact that grass silage quality can vary. Results have demonstrated that it is possible to predict, with reasonable precision, the milk production response to various combinations of grass silage and concentrates in the diet. This will facilitate investigation of production and economic responses of offering increased levels of concentrates in the diet on milk yield, milk quality and milk value.

Three pig trials were done to estimate an objective requirement of young (10 to 20 kg) pigs for leucine (Leu). Within each trial, four or five replicates of five pigs were given ad libitum access to their experimental diet for a period of 21 (trial 1) or 19 days (trials 2 and 3). A Leu-deficient diet (177 g crude protein per kg) based on maize, peanut meal, lactose, sucrose, dried whey, maize starch, soya-bean meal (SBM), and gelatin was used in these trials. Trial 1 showed that the Leu-deficient diet supplemented with Leu produced responses in weight gain and gain/food ratio that were similar (P > 0·10) to that obtained from a maize-SBM-whey positive-control diet containing 213 g crude protein (CP) per kg. Trials 2 and 3 utilized graded levels of crystalline L-Leu to determine the minimal Leu requirement in young pigs. Both trials showed linear increases (P < 0·05) in weight gain and gain/food as a result of Leu supplementation. Closer examination of the data revealed no significant change in gain/food or PUN responses above 11·2 g/kg total Leu in trial 2, or in weight gain or PUN values above 11·5 g/kg total Leu in trial 3. These data indicate that the Leu requirement of young pigs is probably not greater than 11·5 g/kg (10·5 g/kg true digestible), which equates to approximately 0·72 g true digestible Leu per MJ metabolizable energy. The ideal ratio of Leu to Lys appears to be close to 1: 1 for pigs in the weight range of 10 to 20 kg.

Three goats provided with oesophageal and ruminal cannulae were used to determine variations in dry matter (DM) and neutral-detergent fibre (NDF) degradability of the forage consumed when grazing thorn scrubland in the semi-arid region of north Mexico, during two consecutive dry and wet periods. Ingesta samples were incubated intraruminally, the data were fitted to the exponential equation P = a + b (l - e-ct) and statistically analysed using a randomized-block design. Organic matter and crude protein (CP) contents were higher (P < 0.05) in the wet seasons. Values of NDF were similar in dry and wet season of both years whereas higher numerical values of acid-detergent fibre (ADF), lignin and cellulose were registered in the dry seasons. DM and NDF degradabilities after 24 and 48 h of ruminal incubation were higher (P < 0.05) in the wet seasons. Higher values (P < 0.05) in DM and NDF bag losses at zero time (A fraction) were registered in the two wet seasons. The insoluble but fermentable DM and NDF (B fractions) were higher (P < 0.05) in the 1999 wet season and variable in the rest of the studied period. Numerically higher values of DM and NDF c fraction were found in wet periods, whereas DM and NDF potential degradabilities were higher (P < 0.05) in the wet season in 1999 and similar across seasons in 2000. Lowest (P < 0.05) contents of CP in grazed forage, DM and NDF degradabilities after 48 h of ruminal incubation, and A, and B, and c fractions were observed in the dry seasons. Thus, these results may be related to both the lower feeding value of forage consumed by the animals and lower performance of livestock during this period. Then, the DM and NDF degradability after 48 h, together with the insoluble but fermentable matter and the c fraction permit the nutritive value of the forage consumed by grazing goats to be accurately described.

An investigation was conducted to test the hypothesis that dietary oil inclusion increases ammonia nitrogen (NH3-N) emission from the manure, due to a negative effect of either unsaturated or saturated oil on microbial activity in the intestine. Dietary oil was included at 45 g/kg, as either crude palm oil (PO), soya oil (SO) or a 50: 50 SO: PO blend (OB), to a basal barley-soya-wheat diet (control) at the expense of dextrose and maize starch. Diets were formulated to contain 13·2 MJ digestible energy per kg and 11·0 g/kg lysine. Four boars were assigned to each dietary treatment, and were transferred to metabolism crates (mean live weight, 74·0 (± 2·89) kg) following 14 days dietary acclimatization. Urine and faeces were collected separately over a 5-day digestibility/nitrogen (N) balance period and a 2-day manure collection period. Inclusion of dietary oil increased apparent digestibility of oil (P < 0·01) and decreased the apparent digestibility of dry matter (P < 0·01) and gross energy (P < 0·05). Dietary oil did not affect the apparent digestibility of nitrogen, acid-detergent fibre, neutral-detergent fibre or hemicellulose. Apparent digestibility of oil was lower when oil was included as PO compared with SO and OB (P < 0·001). The concentration of faecal volatile fatty acid (VFA) was similar in all treatments, although the acetic: propionic acid ratio was lower when oil was included as PO and OB compared with SO (P < 0·05). N balance, manure N concentration and NH3-N emission was not affected by oil inclusion or oil source. In conclusion, dietary oil inclusion reduced apparent dry matter and energy digestibilities, although no effect on fermentation was indicated by digestibility of fibre or faecal VFA content. Consequently, ammonia emission was not affected by dietary oil included at 45 g/kg.

The effects of supplementing a tropical, low-quality grass hay (Brachiaria dictyoneura) with legume foliage (Cratylia argentea) or fruits of the multipurpose tree Sapindus saponaria on ruminal fermentation, methane release and nitrogen (N) utilization were evaluated. Six Swiss White Hill lambs were used in a 6 ✕ 6 Latin-square design with a 3 ✕ 2 factorial arrangement of treatments with measurements of energy metabolism being conducted using open-circuit respiratory chambers. Treatments consisted of three basal diets, either grass alone or legume: grass ratios of 1: 2 or 2: 1. These basal diets were supplemented (1: 3) with a control concentrate or with a concentrate containing 250 g/kg dry matter of S. saponaria fruits. The apparent total tract digestibilities of organic matter (OM) and neutral-detergent fibre (NDF) were reduced and the proportionate crude protein (CP) losses through faeces were increased (P 0·01) by supplementation with S. saponaria, and digestibilities of OM and NDF were linearly reduced (P 0·001) with increasing legume proportion. Body energy retention, however, was similar in all diets. Along with CP intake, the proportionate CP losses through faeces decreased (P 0·001) with increasing legume proportion which was associated with improved (P 0·001) body protein retention and reduced (P 0·1) fat retention. Ruminal fluid ammonia concentration was not significantly affected (P > 0·1) by the inclusion of S. saponaria in the concentrate, but increased linearly (P 0·001) as dietary legume proportion was elevated. Supplementation with fruits of S. saponaria increased (P 0·01) total bacteria count, and decreased (P 0·001) total ciliate protozoa count by more than proportionately 0·50. Daily methane release was reduced (P 0·01) by S. saponaria supplementation in all basal diet types. Although being not clearly affected on a daily basis, methane release relative to body protein retention decreased linearly (P 0·05) with increasing legume proportion. The fact that interactions were mostly non-significant (P > 0·05) indicates that supplementation with S. saponaria fruits is a useful means to reduce methane emission from sheep given both tropical grass-based and grass-legume-based diets. Likewise, including legumes in N-limited tropical diets seems to represent an environmentally friendly way to improve animal productivity.