This experiment investigated the effect of feeding grass silage alone or supplemented with additional energy and/or protein on the partitioning of nutrients between fat and lean deposition in cattle grown from approximately 140 to 550 kg. The distribution of total body fat between the main fat depots was also assessed. Ninety-two Hereford ✕ Friesian steers (140±18•8 kg initial live weight) were allocated to one of four dietary treatments; grass silage offered either alone (diet S) or supplemented with fish meal (diet FM; 150 g/kg silage dry matter (DM) intake but offered at equal estimated metabolizable energy (ME) intake to silage) or forage-concentrate diets of silage and a barley/soya (80: 20) concentrate at ratios of 70: 30 or 30: 70 on a DM basis (diets 30C and 70C, respectively). Eight animals were slaughtered at the start of the trial to determine initial carcass composition. Of the remaining 21 animals per diet, three were slaughtered at each of seven live weights ranging between 250 and 550 kg, at 50-kg intervals. Animals were given food individually and diets were offered ad libitum (except for FM) along with 100 g/day of a commercial vitamin/mineral pre-mix. At slaughter, half carcasses were minced for the determination of fat and protein content and visceral fat depots, perirenal, mesenteric and omental were removed and weighed. The relationships between chemical composition and empty body weight (EBW) at slaughter were assessed using allometric equations (loge y = loge a + b loge EBW). The composition of the silage was 271•9 g/kg toluene DM with a total nitrogen and estimated ME of 26•5 g/kg DM and 11•8 MJ/kg DM, respectively. DM intakes increased (P < 0•001) with increasing level of concentrate and this generated the expected differences in both energy and protein intake. Live-weight gains increased by proportionately about 0•1, 0•18 and 0•34 on the FM, 30C and 70C treatments, respectively, compared with the S alone. Carcass protein deposition (kg) was relatively linear across the slaughter weights 250 to 550 kg, except for the 70C treatment where the slope (shape or curvature parameter, b) was lower compared with S (P = 0•007). Carcass fat (kg) was similar between S and FM. However, at 350 kg EBW and above, the carcasses of animals given concentrate contained more fat (P < 0•01) compared with those on silage. Carcass fat deposition (kg) showed significant curvature between 200 and 500 EBW (kg) and this was most pronounced for the concentrate treatments with the slopes of the 30C and 70C (P = 0•072, P = 0•003 respectively) differing from the silage. Similar responses were observed for the visceral fat depots. Feeding concentrates resulted in a lower proportion of the total fat being deposited as carcass fat (and hence more as non-carcass fat), proportions averaging 0•65 and 0•61 for S and 70C, respectively; P = 0•066). The proportion of mesenteric fat decreased substantially with increasing total fat (P < 0•001). The relative contribution of intramuscular fat (g/kg total fat) in the longissimus dorsi muscle increased with total fat (P = 0•007) and this was particularly apparent for the S, FM and 30C and less so for 70C. It is concluded that good quality grass silage will support high levels of performance without the need for additional concentrate supplementation. The latter may contribute towards increased fat deposition within the animal.

Results are presented of an investigation in which 10 bull calves were subjected to heat stress in a climatic chamber from 26 weeks of age to the age of puberty. A similar group of 8 calves sired by the same bull were simultaneously subjected to ambient temperatures in another chamber. Maximum temperature in the hot chamber was 35–36° C. for 8 hours daily and maximum temperature in the temperate chamber was 27° C.

Observations were made on weight and age at puberty and characteristics of the first five ejaculates obtained from each bull. Post-mortem examinations included: carcass weight, weight of all genital organs, measurement of sperm reserves in testicles and epididymides and histological observations of the seminiferous tubules. The results indicated that the hot temperature exposure retarded fertility but that libido was exhibited at essentially the same intensity by both groups. The quality of semen obtained and the concentration of the spermatozoa were much lower in the bulls subjected to the hot environment during their growth period prior to puberty. The poor quality of semen was associated with impaired spermatogenesis.

It is recommended that in all fertility studies conducted with exotic breeds in the tropics, semen of known uniform quality be used. Natural service should not be used.

To determine how weaning date affected productivity in deer farming systems, calf growth rate, hind conception date, and hind condition were monitored on 10 New Zealand deer farms located in Otago and Southland, from February/March until August/September in 1999 (no. = 551 hind-calf pairs) and 2000 (no. = 414 pairs). On each farm, in both years, half of the hind-calf pairs were separated for early weaning (mean date 11 March; range 25 February to 17 March), while the other half remained together for late weaning (mean date 28 May; range 12 May to 10 June). Deer in both treatments on each farm were of similar age and genotype and stags were added to hind groups on the same day in March. Calves were weighed in February/March, May/June and August/September. Scanning of hinds to determine date of conception was carried out in June.

Climatically the 2 years were very different with a summer drought preceding observations in 1999, nevertheless similar effects of weaning date were observed in both years. Calves weaned early gained less weight than the late-weaned calves (142 v. 210 g/day in 1999, and 131 v. 166 g/day in 2000) between February/March and May/June (P < 0·001). However mean conception dates were earlier in the early-weaned hinds compared with the late-weaned hinds (by 12 days in 1999 and 7 days in 2000,P < 0·001). Hind condition scores in May/June were higher for the early-weaned hinds compared with the late-weaned hinds (by 0·5 score units in 1999 and 0·3 score units in 2000, P < 0·001). For all measures the effects of weaning date varied between farms (P < 0·001). It was concluded that farmers weaning early could expect a positive effect on hind conception date and winter hind condition and a negative effect on calf growth rate, but management could override negative effects of weaning early or late.

1. Two experiments are described in which the consequences of variation in grazing intensity were studied during the subsequent period of winter feeding from 12 months of age to slaughter at 18 months. The cattle were loose-housed and fed on silage ad libitum, together with allowances of rolled barley. Individual organic-matter intake was measured periodically, chromic oxide being used to estimate faecal output. The digestibility of the diet was estimated with stall-fed steers.

2. Groups of 12 steers were grazed at different intensities over five-month periods, so that those grazed at the higher intensity were 38 and 16 kg lighter at the start of the 1966 and 1967 winter feeding periods respectively. They did not make significant compensatory growth over the subsequent winter feeding periods, although they had a significantly higher intake of feed organic matter per 100 kg live weight than the control steers.

3. With supplements of 3·63 and 1·81 kg/head per day of barley, live-weight gains were 0·77 and 0·50 kg/head per dayin the first half of the winter, but in the second half, when barley allowances were raised to 4.54 and 2·72 kg/head per day, both groups gained weight at the same rate (0·94 kg/head per day).

4. The higher level of barley feeding reduced silage intake by 0·4 kg OM/kg barley OM at all stages of the winter, and the additional 306 kg of barley was associated with the production of 21 kg more carcass weight at slaughter. This higher yield of carcass was reflected in a higher weight of fat in a three-rib sample joint.

Utilization of long-chain alcohols (LCOH) as diet composition markers in horses and cattle was assessed in a study conducted with 12 mature crossbreed mares (385±47 kg BW) and six adult non-lactating cows (499±36 kg BW) of Asturiana de los Valles breed. The LCOH data were combined with alkane and long-chain fatty acid (LCFA) data to test the applicability of combining these markers to estimate diet composition. Animals were randomly divided into groups of three animals and received a daily total amount of 1.0 kg dry matter/100 kg BW of diets composed of different proportions of ryegrass (Lolium perenne) and woody species (Ulex gallii and heather). Diet composition was estimated from even-chain LCOH (C20-OH to C30-OH) combined or not with alkane (C25-C31 and C33) and/or LCFA (C22-FA to C28-FA, C30-FA, C32-FA and C34-FA) concentrations in diet components and faeces by least-squares procedures, using marker faecal concentrations uncorrected for incomplete faecal recovery (FR0) or corrected using mean recoveries across diets within animal species (FR1). Results showed large differences between plant species in their LCOH profiles, and that these markers offered additional discriminatory information to that provided by alkanes and LCFA. The LCOH markers were incompletely recovered in the faeces of both animal species. In cattle, LCOH FR tended to increase with carbon-chain length in a linear manner in both diets (P<0.001), whereas in horses overall data showed a curvilinear relationship between these variables. Combination of LCOH, LCFA and alkanes resulted in more accurate diet estimates. Correction of faecal LCOH concentrations to incomplete FR led to more accurate diet composition estimates in both animal species. Results obtained in this study suggest the usefulness of LCOH markers combined with alkanes and LCFA to estimate diet composition of horses and cattle grazing mixed grassy–woody plant communities.

In experiments based on ruminants’ individual dry matter intake (DMI) assessment, several external markers can be used to estimate faecal output when total faeces collection is not possible. However, preparation of the markers to be administered and analytical procedures used for marker content determination are time-consuming thus strongly limiting the number of animals involved in the experiments. In this paper, polyethylene glycol (PEG, molecular weight 6000 da) was tested as a faecal marker. Four trials were conducted on dry, non-lactating ewes kept in digestibility crates that allowed individual measurements. The overall experiment was designed to assess the major factors that could lessen the effectiveness of this method, assuming that the use of grab samples of faeces is sufficient. Trial 1 was designed to test two levels of PEG (20 and 40 g/day) administered in two equal amounts. Trial 2 was designed to test the effect of either a single morning (0800 h) dose (20 g/day) or a twice daily administration (0800 and 1600 h) of the same fractionated dose. Trial 3 was designed to test a 20 g/day dose of PEG administered once daily to ewes fed with hays of different qualities: medium (MH) and low (LH). In trial 4, a lower dose of PEG (10 g/day) was administered once a day to ewes fed with fresh oat–vetch forage. It was demonstrated that PEG could be precisely estimated (average prediction error = 3.47 g/kg) with near-infrared reflectance spectroscopy (NIRS). On the basis of the four trials, it has been proved that PEG administration (20 and 40 g/day) did not significantly affect the DMI of ewes fed dry diets (trials 1, 2 and 3), whereas there was an unexpected increase of DMI for ewes fed exclusively with green feed (trial 4) without DM digestibility modification. Providing PEG as a single dose (0800 h) or split into two equal parts (0800 and 1600 h) did not alter the estimated DMI. Considering the interest of grab sampling, there were clear variations of PEG in faeces with higher concentrations observed at 0800 and 1600 h and lower concentrations at 1400 h. Consequently, with PEG (measured with NIRS) administered once and using the grab sampling procedure (morning collection), it is possible to estimate the DMI of dry feeds with good accuracy. For green feeds, more research is needed as the estimated results are still highly variable.

Rusitec fermenters are in vitro systems widely used to study ruminal fermentation, but little is known about the microbial populations establishing in them. This study was designed to assess the time evolution of microbial populations in fermenters fed medium- (MC; 50% alfalfa hay : concentrate) and high-concentrate diets (HC; 15 : 85 barley straw : concentrate). Samples from solid (SOL) and liquid (LIQ) content of fermenters were taken immediately before feeding on days 3, 8 and 14 of incubation for quantitative polymerase chain reaction and automated ribosomal intergenic spacer analysis analyses. In SOL, total bacterial DNA concentration and relative abundance of Ruminococcus flavefaciens remained unchanged over the incubation period, but protozoal DNA concentration and abundance of Fibrobacter succinogenes, Ruminococcus albus and fungi decreased and abundance of methanogenic archaea increased. In LIQ, total bacterial DNA concentration increased with time, whereas concentration of protozoal DNA and abundance of methanogens and fungi decreased. Diet×time interactions were observed for bacterial and protozoal DNA and relative abundance of F. succinogenes and R. albus in SOL, as well as for protozoal DNA in LIQ. Bacterial diversity in SOL increased with time, but no changes were observed in LIQ. The incubated diet influenced all microbial populations, with the exception of total bacteria and fungi abundance in LIQ. Bacterial diversity was higher in MC-fed than in HC-fed fermenters in SOL, but no differences were detected in LIQ. Values of pH, daily production of volatile fatty acids and CH4 and isobutyrate proportions remained stable over the incubation period, but other fermentation parameters varied with time. The relationships among microbial populations and fermentation parameters were in well agreement with those previously reported in in vivo studies. Using 15N as a microbial marker or quantifying total microbial DNA for estimating microbial protein synthesis offered similar results for diets comparison, but both methods presented contrasting results for microbial growth in SOL and LIQ phases. The study showed that fermentation parameters remained fairly stable over the commonly used sampling period (days 8 to 14), but shifts in microbial populations were detected. Moreover, microbial populations differed markedly from those in the inocula, which indicates the difficulty of directly transposing results on microbial populations developed in Rusitec fermenters to in vivo conditions.

An analysis of the length of productive life in the Bruna dels Pirineus beef breed was performed with a non-parametric approach giving an average value of 9 years of productive life, and a corresponding replacement rate of 11%. Using a proportional hazards model stratified by herd, the influence of calf birth weight and weight gain until weaning, calving difficulty, calving interval and age at first calving on length of productive life were studied. Two models were explored: the first one included time-dependent variables taking the current value of the covariate at each calving date, while the second one also comprised time-dependent interactions between the value of the covariate of the current calving and its mean value during the last (up to) three previous calvings. Results from the first model showed that the risk of culling increases with very high ages at first calving, increasing calving difficulties, very large calf birth weights, very small weight gains until weaning and very long calving intervals. Furthermore, results from the second model showed that these increases also depend upon a sequence of values for the same covariate in previous calvings. Finally, these higher risks of culling implied lower survival functions that increased replacement rates but only slightly decreased average performances.

Performance, water intake and feeding behaviour of two groups of 30 (trial 1), 40 (trial 2) or 50 (trial 3) weaned pigs offered either pellets or meal of the same formulation were compared.

Average daily weight gains (ADG) were higher for pigs given pellets rather than meal in trials 2 (413 v. 363 g/day,

P < 0·001) and 3 (356 v. 324 g/day, P < 0·05). Mean daily water intake (DWI) was higher with meal than with pellets but only during trial 1 (2·31 v. 1·65 I/day, P < 0·01).

The occupation time (ОT) and the number of animals using the feeder simultaneously (N) were higher when pigs were given meal rather than pellets, whatever the animal density: trial 1: 82·6 v. 69·9% (P = 0·05) and 3·8 v. 2·3 (P < 0·01); trial 2: 90·9 v. 77·9% (P > 0·05) and 5·2 v. 3·1 (P < 0·01); trial 3: 96·2 v. 83·6% (P < 0·05) and 5·9 v. 3·8 (P < 0Ό1). When using pellets, ОT and N were always significantly lower during the night than during the day but when using meal in groups of 40 and 50, ОT during the night was almost as high as during the day.

The greater the group size, the lower were ADG (both diets) and DWI (only with meal) and the higher were ОT and N (both diets). Furthermore, significant linear and curvilinear regressions of DWI, ОT and N according to time were calculated.

In conclusion, pigs need more time to eat meal than to eat pellets. Thus the number of pigs per feeder has to be adapted to the food presentation. Too high a number of pigs per feeder impairs feeding behaviour and eventually welfare, by preventing preferential diurnal feeding activity and this may affect productivity.

The effect of age on incidence of susceptibility to halothane anaesthesia in pigs was studied on animals that were repeatedly exposed to the anaesthetic. In three trials, 232 Piétrain/Hampshire and 201 Landrace pigs were given three 3-min halothane tests, at 19, 35 and 54 days of age. In a fourth trial 253 Landrace pigs received four 5-min tests, at 21, 35, 49 and 63 days. All pigs were offspring of positive × positive matings. Maximum-likelihood estimates of the probability of positive reactions were 0·47, 0·73 and 0·88 at the three ages in Pietrain/Hampshire; 0·20, 0·63 and 0·60 in the first Landrance trial; and 0·64, 0·86, 0·84 and 0·90 in the second Landrace trial. Thus, in all trials, the incidence of halothane positive reactions increased with age. In both breeds and at all ages, the incidence was lower in males than in females.

Sixteen sheep which had previously eaten wheat only (eaters) were offered wheat, barley, oats and maize separately in a Latin-square design with two sheep per cell and two replicates of the Latin square. Another 16 sheep which had never previously been offered wheat (non-eaters) were offered the same cereal grains in two more Latin squares with two sheep per cell.

The total intake of wheat for the eaters was significantly greater than for the other cereal grains (P < 0·01) and it took 7 to 9 days for other cereals to be eaten. There was virtually no consumption of cereal grains by the non-eaters until days 10 to 12 when some wheat but little other cereal was being eaten.

The results indicate that sheep learn to eat each type of cereal grain separately but if they know how to eat wheat they learn to eat other cereal grains more rapidly.

Four models for in vitro embryo production traits in Guzerá cattle were compared: Gaussian (untransformed variable – LIN and transformed in logarithmic scale – LOG), Poisson (POI) and zero-inflated Poisson (ZIP). Data consisted of 5716 ovum pick-up and in vitro fertilization records performed in 1205 cows from distinct regions of Brazil. Analyzed count traits were the number of viable oocytes (NOV), number of grade I oocytes (NGI), number of degenerated oocytes (NDG), number of cleaved embryos (NCLV) and number of viable produced embryos (NEMB). Heritability varied from 0.17 (LIN) to 0.25 (POI) for NOV; 0.08 (LOG) to 0.18 (ZIP) for NGI; 0.12 (LIN) to 0.20 (POI) for NDG; 0.13 (LIN) to 0.19 (POI) for NCLV; 0.10 (LIN) to 0.20 (POI) for NEMB depending on the considered model. The estimated repeatability varied from 0.53 (LOG) to 0.63 (POI) for NOV; 0.22 (LOG) to 0.39 (ZIP) for NGI; 0.29 (LIN) to 0.42 (ZIP) for NDG; 0.42 (LIN) to 0.59 (POI) for NCLV; 0.36 (LIN) to 0.51 (POI) for NEMB. The goodness of fit, measured by deviance information criterion and mean squared residuals, suggested superiority of POI and ZIP over Gaussian models. Estimated breeding values (EBV) obtained by different models were highly correlated, varying from 0.92 for NOV (between LIN-POI) and 0.99 for NGI (between POI-ZIP). The number of coincident animals on the 10% top EBV showed lower similarities. We recommend POI and ZIP models as the most adequate for genetic analysis of in vitro embryo production traits in Guzerá cattle.

1. Thirty-two individually-fed pigs were used to determine the effects of soaking their daily meal ration in either water or in liquid skim milk and water for approximately 24 hr. before feeding. The experimental period continued from about 10 weeks of age to bacon weight.

2. Neither soaking procedure had any significant effect on the rate of growth, efficiency of food utilisation, dressing percentage, carcass length, backfat thickness or commercial grading results of the pigs.

3. The growth rate and efficiency of food utilisation of the pigs given meal plus skim milk were significantly better than for those given the all meal diet. The dressing percentage of the former was also significantly higher than the latter, but there were no significant differences between the two groups in carcass length or backfat thickness.

4. Possible reasons for the difference in performance of the all meal and meal plus skim milk-fed pigs are discussed.

Rumen fill may be a strong intake constraint for dairy cows fed on pasture, even though pasture is highly digestible in the grasslands of temperate climates. This constraint may also depend on the cows’ maturity. Moreover, indoor feeding of fresh herbage may not always be a good model for the study of intake regulation at grazing. To test these hypotheses, four mature (6.3 ± 0.72 year old) and four young (3.8 ± 0.20 year old) dairy cows were offered fresh perennial ryegrass indoors or at grazing. The impact of rumen fill on intake was evaluated by addition of rumen inert bulk (RIB; coconut fiber, 15 l) compared to a control. The experimental design was a double 4 × 4 Latin square with four 14-day periods and a 2 × 2 factorial arrangement of two feeding methods (indoor feeding v. grazing), combined with the addition, or not, of RIB (RIB v. control), repeated for four mature and four young cows. Digestibility of offered herbage was 0.81. The average ytterbium measured dry matter intake (Yb DMI) was 19.0 and 15.5 kg/day for mature and young cows respectively (P = 0.019). The effect of RIB on predicted Yb DMI interacted with feeding method and cow age (P = 0.043). The presence of RIB decreased Yb DMI by 4.4 kg/day in mature cows at grazing and by 3.4 kg/day in young cows indoors, whereas it did not affect the Yb DMI of mature cows indoors or grazing young cows. Both grazing and young age constituted a clear constraint on the feeding behavior of the cows. Grazing cows had fewer ingestion and rumination sequences, which were longer and less evenly distributed throughout the day and night. Young cows had lower intake rates that were less adaptable to the feeding method and the presence of RIB. Mature cows clearly decreased their daily intake rate at grazing compared to indoor feeding, and with RIB compared to control, whereas the intake rate of young cows did not vary. These results indicate that rumen fill can represent a constraint on intake in grazing cows, even when highly digestible perennial ryegrass is offered. The study also shows that the impact of RIB on intake is highly dependent upon other constraints applied to the chewing behavior, which in this experiment were methods of offering herbage and cow age.

Survival or longevity is an economically relevant trait in cattle. However, it is not currently included in cattle selection criteria because of the delayed recording of phenotypic data and the high computational demand of survival techniques under proportional hazard models. The identification of longevity-correlated traits that can be early registered in lifetime would therefore be very useful for beef cattle selection processes. The aim of this study was to estimate the genetic correlation of survival (SURV) with: growth – birth weight (BW), weight at 120 days (W120), weight at 210 days (W210); carcass – cold carcass weight (CCW), conformation (CON), fatness (FAT) and meat colour (COL); teat morphology – teat thickness (TT), teat length (TL) and udder depth (UD); leg morphology – forward (FL) and backward legs (BL); milk production (MILK) and docility (DOC). In the statistical analysis, SURV was measured in discrete-time intervals and modelled via a sequential threshold model. A series of independent bivariate Bayesian analyses between cow survival and each recorded trait were carried out. The posterior mean estimates (and posterior standard deviation) for the heritability of SURV was 0.05 (0.01); and for the relevant genetic correlations with SURV were 0.07 (0.04), 0.12 (0.05), 0.10 (0.05), 0.15 (0.05), −0.18 (0.06), 0.33 (0.06) and 0.27 (0.15) for BW, W120, W210, CCW, CON, FAT and COL, respectively.

Three experiments were conducted to investigate the effect of bag incubation sequence on the degradation of food components in situ in the caecum of mature, caecally fistulated Welsh-cross pony geldings (mean live weight 278 kg) offered hay ad libitum. In experiment 1 a fibre-based commercial horse concentrate was incubated in situ using a forward (3, 5, 16, 8, 24, 48 h) or reverse (48, 24, 8, 16, 5, 3 h) incubation sequence. Dry matter (DM), crude protein (CP), neutral-detergent fibre (NDF) and acid-detergent fibre (ADF) degradation coefficients and calculated effective degradability (ED) values were determined. In experiment 2 unmolassed sugar-beet pulp (USBP), hay cubes (HC), soya hulls (SH) and a 2: 1 mixture of oat hulls: naked oats (OHNO) were incubated in situ as for experiment 1. In experiment 3 unprocessed barley (UB), micronized barley (MB), extruded barley (EB) and dehydrated grass (DHG) were incubated in situ according to slightly different forward or reverse incubation sequences of (2, 4, 6, 12, 8, 24, 48 h) and (48, 24, 8, 4, 12, 6, 2 h) respectively. In experiments 2 and 3 only DM degradation parameters were studied.

Of the three starch-based foods studied in experiment 3 (UB, MB and EB), incubation sequence did not significantly P > 0·05) affect any of the degradation parameters examined. Conversely however, of the six fibre-based foods which were examined across the three experiments, incubation sequence did significantly P < 0·05) affect in situ degradation parameters in the commercial horse concentrate in experiment 1, the SH food in experiment 2 and the DHG food in experiment 3. Depending on the food or food constituent studied (i.e. DM, CP, NDF or ADF) degradation coefficients a, b, c and a + b along with ED values calculated at fractional outflow rates of 0·05 and 0·025 could all be statistically different CP < 0·05) according to whether a forward or reverse incubation sequence was used. It is postulated that this effect is related to the basic digestive physiology of the equine caecum which is small, digesta passage rate through it is fast and digesta volumes can vary considerably. These factors may interact to create a considerable degree of non-uniformity within the caecal digesta pool in which in situ bags are incubated. Consequently, it is recommended that in future in situ experiments in the equine hindgut, animals are offered ad libitum diets in an attempt to minimize variation within the caecum. It is also recommended that in situ experimental protocols incorporate more than one incubation sequence when the degradation parameters of fibrous foods are studied in equids.

The calving interval (CI) can potentially impact the economic results of dairy farms. This study highlighted the most profitable CI and innovated by describing this optimum as a function of the feeding system of the farm. On-farm data were used to represent real farm conditions. A total of 1832 accounts of farms recorded from 2007 to 2014 provided economic, technical and feeding information per herd and per year. A multiple correspondence analysis created four feeding groups: extensive, low intensive, intensive and very intensive herds. The gross margin and some of its components were corrected to account for the effect of factors external to the farm, such as the market, biological status, etc. Then the corrected gross margin (cGMc) and its components were modelled by CI parameters in each feeding system by use of GLM. The relationship between cGMc and the proportion of cows with CI<380 days in each feeding group showed that keeping most of the cows in the herd with CI near to 1 year was not profitable for most farms (for the very intensive farms there was no effect of the proportion). Moreover, a low proportion of cows (0% to 20%) with a near-to-1-year CI was not profitable for the extensive and low intensive farms. Extending the proportion of cows with CI beyond 459 days until 635 days (i.e. data limitation) caused no significant economic loss for the extensive and low intensive farms, but was not profitable for the intensive and very intensive farms. Variations of the milk and feeding components explained mainly these significant differences of gross margin. A link between the feeding system and persistency, perceptible in the milk production and CI shown by the herd, could explain the different relationships observed between the extent of CI and the economic results in the feeding groups. This herd-level study tended to show different economic optima of CI as a function of the feeding system. A cow-level study would specify these tendencies to give CI objectives to dairy breeders as a function of their farm characteristics.

A total of 74 pigs representing three commercially available crossbred types, Landrace (50%), Pietrain (50%) and Meishan (25%), were given food ad libitum over a 25- to 115-kg growth period and serially slaughtered for physical and chemical analysis in five groups at 32, 42, 63, 82 and 114 kg live weight (W). Results are presented in the order of pig type as above. Pig types grew at similar overall rates of live body gain, but the Meishan type ate more food and had greater back fat depth. The Pietrain type was least fat. Dissected fatty tissue grew substantially faster than the carcass as a whole; allometric exponents being 1·64, 1·34 and 1·52 (P < 0·05) for the Landrace, Pietrain and Meishan types respectively. Dissected lean tissue gains were 0·419, 0·427 and 0·308 kg daily (P < 0·01), and dissected fatty tissue gains were 0·251, 0·158 and 0·218 kg daily (P < 0·05); the Meishan type being slowest for lean gain and the Pietrain type slowest for fatty tissue gain. The Pietrain type had the largest cross-sectional area of the longissimus dorsi muscle, and the Meishan type the smallest. The pelvic limb of the Meishan type lost density (as measured by specific gravity) fastest, and that of the Pietrain slowest as the pigs grew. The Meishan type had a lower proportion of its carcass lean and a higher proportion of its carcass fat in the pelvic limb than did the other two types. For each kg of live-weight gain, 0·037, 0·041 and 0·032 kg (P < 0·05) of chemical protein was deposited in the pelvic limb of the three types respectively. Equivalent values for chemical lipid were 0·041, 0·035 and 0·041 (P < 0·05). The Meishan type retained protein at a relatively slower rate in the pelvic limb than in the body as a whole. The Pietrain type had the greatest ultimate protein mass in the pelvic limb. Estimation of whole body protein content as a linear function of pig live weight gives coefficients of 0·154, 0·178 and 0·168 kg (P < 0·05) for the three types respectively. Equivalent values for whole body lipid content were 0·269, 0·214 and 0·274 (P < 0·05). Best estimates of the daily rates of protein retention in the body of the whole live pig were 0·152, 0·197 and 0·142 kg/day for the Landrace, Pietrain and Meishan types respectively.

On-farm nutrition and management interventions to reduce enteric CH4 (eCH4) emission, the most abundant greenhouse gas from cattle, may also affect volatile solids and N excretion. The objective was to jointly quantify eCH4 emissions, digestible volatile solids (dVS) excretion and N excretion from dairy cattle, based on dietary variables and animal characteristics, and to evaluate relationships between these emissions and excreta. Univariate and Bayesian multivariate mixed-effects models fitted to 520 individual North American dairy cow records indicated dry matter (DM) intake and dietary ADF and CP to be the main predictors for production of eCH4 emissions and dVS and N excreta (g/day). Yields (g/kg DM intake) of eCH4 emissions and dVS and N excreta were best predicted by dietary ADF, dietary CP, milk yield and milk fat content. Intensities (g/kg fat- and protein-corrected milk) of eCH4, dVS and N excreta were best predicted by dietary ADF, dietary CP, days in milk and BW. A K-fold cross-validation indicated that eCH4 and urinary N variables had larger root mean square prediction error (RMSPE; % of observed mean) than dVS, fecal N and total N production (on average 24.3% and 26.5% v. 16.7%, 15.5% and 16.2%, respectively), whereas intensity variables had larger RMSPE than production and yields (29.4%, 14.7% and 14.6%, respectively). Univariate and multivariate equations performed relatively similar (18.8% v. 19.3% RMSPE). Mutual correlations indicated a trade-off for eCH4v. dVS yield. The multivariate model indicated a trade-off between eCH4 and dVS v. total N production, yield and intensity induced by dietary CP content.

The response of Hereford × Friesian heifers to large intakes of two types of high glucosinolate rapeseed meal were studied during two 5-month periods in consecutive years. In year 1, six heifers were given a compound concentrate food containing 250 g/kg extracted rapeseed meal and six control animals were given concentrate containing 210 g/kg soya-bean meal. In year 2, a further six heifers were given concentrate containing 320 g/kg expeller rapeseed meal and six control animals were given the same soya-bean meal compound concentrate. The crude protein (CP): metabolizable energy (ME) ratio of all diets was 14·3 g CP per MJ ME. Barley straw was the only roughage offered.

There were no differences between groups in ovarian activity assessed from plasma progesterone concentrations, nor in behavioural activity around oestrus. The heifers were slaughtered 6 weeks after artificial insemination. Pregnancy rate was proportionally 0·58 (7/12) in the rape-fed and 0·67 (8/12) in the control heifers (P > 0·05). Foetuses from heifers given rapeseed meal were slightly smaller than those from control heifers; the difference was significant in year 2 (P < 0·05).

Thyroid glands of heifers given rapeseed meal showed histological evidence of goitrogenicity but weights of the glands did not reflect this. Plasma thyroxine values were depressed in heifers given rapeseed meal (year 1, P < 0·001; year 2, P < 0·05). Plasma thiocyanate was elevated in rapeseed meal heifers in both years (P < 0·001) compared with values for control animals.