This study assessed the efficacy of the n-alkane technique to estimate intake and diet composition in animals given single foods or a choice of two. In the first experiment intakes of pelleted ryegrass and lucerne, given either alone or as a choice, were measured in lambs housed indoors in individual pens. Each of the three feeding treatments was given to 12 lambs at two degrees of maturity (0·30 and 0·45 of estimated mature sizes). The 12 lambs were constituted as three replicates of the two sexes of each of two breeds. The measured intakes were compared with those estimated using the n-alkanes C31 and C33, found naturally in the foods, and C32, which was given as a dose. On the choice treatment diet composition was estimated using a non-negative least squares procedure and data on C31 and C33 alone. The agreement between actual and predicted intake was good: R2 of 0·938 for log-linear regression with a residual standard deviation of 0·0845. Intake of lucerne when offered alone was slightly yet significantly over-predicted. The proportion of ryegrass in the diet was also accurately predicted (R2 of 0·950 and residual s.d. of 0·0398). Using the data on C27 and C29, in addition to that on C31 and C33, gave a poorer agreement with the observed diet compositions. The low and similar levels of C27 in the two foods meant that this n-alkane provided little extra information that could be used to estimate diet composition. In a second experiment faecal samples were collected every 4 hours over a 24-h period in six lambs on ad libitum, and in six lambs on a restricted quantity, of pelleted ryegrass. There was no significant diurnal variation in the ratios of either C31 or C33 to C32 on either ad libitum or restricted feeding. The time of faecal collection within a day should not therefore affect the reliability of the predictions. The study confirmed the value of using n-alkanes in methods to determine the intake of forages by sheep, and that the time of faecal collection within the day does not affect the reliability of these predictions. The results also confirm the utility of the n-alkane method for estimating diet choice, at least with two-component mixtures.

Crossbred gilts were offered rapeseed press cake (RSP) as follows: control (no RSP in diet during growth/ pregnancy/lactation), M-RSP (medium RSP levels: 100/50/100 g/kg RSP) and H-RSP (high RSP levels: 150/80/ 150 g/kg RSP). Plasma concentrations of free thyroxine (FT4), tri-iodothyronine (T3), luteinizing hormone (LH), prolactin (PRL), progesterone (P4) and androstenedione (A4), weights of thyroid gland, ovaries and uterus, length of uterine horns, and number of corpora lutea (CL) were measured in gilts during the mid-luteal phase of their first oestrous cycle. Serum concentrations of FT4, T3, LH and PRL, weights of thyroids, ovaries, uteri, adrenals, kidneys, liver and spleen were measured in female piglets on 2nd and 28th day of lactation. RSP diets, affected thyroid weights, number of CL, uterine horn length, mean concentrations of plasma FT4, T3, PRL, and P4 in gilts. Changes of weights of ovaries in 2-day-old piglets and weights of uterus, adrenal gland and kidneys in 28-day-old piglets from RSP groups were observed.

Four groups of eight primiparous ewes and their single lambs were grazed for 2 weeks on pasture containing one of four novel grass species – perennial ryegrass, timothy, cocksfoot and red fescue. When subsequently grazed in a field with randomized plots of the four species, both ewes and lambs spent longer grazing the species to which they had been accustomed than was spent by ewes and lambs accustomed to other species. This effect was proportionately greater for the lambs than the ewes, and the lambs responded most to experience of cocksfoot and red fescue. Both ewes and lambs spent most time grazing perennial ryegrass and timothy, and least time grazing red fescue, with cocksfoot intermediate. It is concluded that perennial ryegrass and timothy are grazed by ewes and lambs in preference to cocksfoot and red fescue, but that a two week period of experience will increase the attractiveness of the less-preferred species, particularly to lambs.

Cumulus-oocyte complexes with surrounding granulosa cells (COCGs) in early antral follicles (0·5 to 0·7 mm in diameter) were surgically collected from sections of bovine ovarian cortex under a dissection microscope and subsequently cultured in vitro using follicle stimulating hormone (FSH), epidermal growth factor (EGF), insulin-transferrin-selenium (ITS) and hypoxanthine, singly or in combination, to obtain fully grown matured oocytes. Oocytes cultured in the presence of FSH + hypoxanthine increased (P < 0·05) in diameter from 93 µm on the day of commencement of culture to 106·37±0·34 µm on day 5. Oocytes cultured in the presence of FSH, hypoxanthine or hypoxanthine + ITS + FSH increased (P < 0·05) to mean diameters of 105·40 (s.e. 0·47) µm, 105·50 (s.e. 0·39) µm and 105·35 (s.e. 0·55) µm, respectively. By day 11 of culture, oocyte diameters 110·50 (s.e. 0·35) µm, 110·13 (s.e. 0·39) µm, 109·49 (s.e. 0·46) µm, 109·53 (s.e. 0·58) µm and 109·16 (s.e. 0·43) µm were recorded for treatments FSH + hypoxanthine, hypoxanthine + ITS + FSH, FSH, hypoxanthine and FSH + EGF + hypoxanthine + ITS, respectively. The proportions with COCGs which formed an antrum while cultured in vitro; were categorized as morphologically normal following recovery from the gel; matured in vitro; showed germinal vesicle break down and reached metaphase II were highest (P < 0·05) for the FSH + hypoxanthine treatment (49/60 (81·7%), 48/60 (80·0%), 47/60 (78·3%), 45/60 (75·0%) and 15/60 (25·0%), respectively, followed by hypoxanthine + ITS + FSH (47/60 (78·3%), 44/60 (73·3%), 41/60 (68·3%), 41/60 (68·3%) and 12/60 (20%), respectively), FSH (43/60 (71·7%), 42/60 (70%), 40/60 (66·7%), 39/60 (65·0%) and 9/60 (15%), respectively) and hypoxanthine (41/60 (68·3%), 38/60 (63·3%), 36/60 (60%), 35/60 (58·3%) and 8/60 (13·3%), respectively). In experiment II, the in vitro fertilization and cleavage rates of COCGs were highest (P < 0·05) for FSH + hypoxanthine treatment (17/60; 28·3%) followed by hypoxanthine + ITS + FSH (13/60; 21·6%), FSH (12/60; 20%) and hypoxanthine (11/60; 18·3%) treatments. The results of this study show that COCGs from early antral follicles can be isolated, cultured and grown in vitro. Furthermore, supplements like FSH and hypoxanthine can be used singly or in combination(s) in culture medium to enhance the growth of COCGs.

The introduction of legumes in grass-based swards provides some economic and agronomic advantages, often allowing an increase in the performance of grazing ruminants. The aim of this study was to obtain a better quantification of the nutritional benefits to dairy cows after introducing white clover into swards of perennial ryegrass (PRG), using two ages of regrowth. Four treatments were studied in a 2 ✕ 2 factorial design with two sward types and two ages of regrowth. The swards were either a pure perennial ryegrass sward with nitrogen (N) fertilization, or a perennial ryegrass/white clover mixture (GC) with no N fertilization. The regrowth ages were 19 and 35 days (treatments: PRG19, PRG35, GC19 and GC35). The proportion of clover in the GC swards was on average 420 g/kg dry matter (DM). Twelve late-lactation Holstein cows, fistulated at the rumen and duodenum, were used according to a 4 ✕ 4 Latin-square design with four 11-day periods. The pasture was strip-grazed with 12 kg DM per cow of herbage above 5 cm offered daily in all the treatments.

The effects of sward type and regrowth age were often additive, in particular for herbage intake and milk yield. Herbage organic matter (OM) intake, duodenal non-ammonia N (NAN) flow and milk yields were higher on the GC swards and lower on the older regrowths. Finally, the performance of the cows was similar on the PRG19 and GC35 treatments. The OM digestibility of the selected herbage as well as the duodenal nitrogen flux per kg digestible OM intake was not affected by the sward type. Ruminal fermentations were more intense with mixed swards and the youngest regrowths. The daily grazing time and the daily pattern of grazing activities were modified by the type of sward and by regrowth age. The average OM intake rate was higher on the GC swards than on the PRG swards. In this study, the nutritional advantage of introducing white clover into swards of perennial ryegrass was related to an increase in herbage intake and not to any improvement in the nutritive value of the sward.

Peripheral concentrations of melatonin in the neonatal mammal are low and the diurnal rhythm is not apparent during the first days or weeks of life. Maternal milk provides a rhythmic although low source of melatonin to the newborn. Diurnal rhythm of serum melatonin was monitored in Friesian calves from birth to 4 weeks of age. Some of the calves under 1 week of age had no clear nocturnal elevation of serum concentrations of melatonin. Thereafter the nocturnal melatonin elevation was apparent in all calves and of the same amplitude as in adult cattle. The effect of oral intake of night-time milk or milk supplemented with low doses of synthetic melatonin was studied during day-time in a group of Ayrshire calves aged 1 to 5 weeks. Two and a half or 3 litres of night-time milk with a mean melatonin concentration of 40 pg/ml, providing 01 to 012 μg melatonin, did not cause any change in the day-time serum concentrations of melatonin, neither did addition of melatonin in doses up to 10 μg per animal. Only the highest dose of melatonin 200 μg in 2 l of milk (01 μg/ml) caused an elevation of day-time serum concentrations of melatonin. These studies show that the pineal gland of a very youg calf is functional and that the concentration of melatonin in blood does not reflect the concentration in milk at the time of feeding. The presence of melatonin in milk suggests, however, its potential significance for the neonate.

Forty single lambs were either artificially reared indoors or were at pasture with their mothers until weaning at 3 months of age, after which one half of each group were joined by five adult, dry ewes, to examine the effects of grazing experience and presence of adult ewes on the response to the introduction of novel grass species. Lamb groups sequentially grazed paddocks with one, two, three and then four grass species in four 1-week periods, and grazing and ruminating times and pasture biting rates were recorded during daylight hours. In the first period the lambs grazed only perennial ryegrass, then timothy, cocksfoot and finally red fescue were introduced in periods 2 to 4 respectively. The total time that lambs spent grazing and ruminating were both increased (P < 0·001) by grazing experience and to a lesser extent by the presence of adult ewes. Pasture biting rate was considerably increased by experience, and to a lesser extent adult presence, with a synergistic effect between these two factors (P < 0·001). Timothy and to a lesser extent perennial ryegrass were the most preferred species, and lambs spent less time grazing cocksfoot than either of these two, and even less time grazing red fescue (P < 0·001). Experience of grazing particularly increased the time spent grazing cocksfoot and red fescue (P < 0·001), but the presence of adult ewes did not increase the time lambs spent grazing novel species (P = 0·59). The pasture biting rate was greater on species that the lambs preferred grazing (P < 0·001), but neither experience nor ewe presence increased the biting rate on novel species in the period of their introduction. It is concluded that although both grazing experience and, to a lesser extent adult presence, increased the total time spent grazing and the pasture biting rate, only grazing experience increased the acceptability of novel species.

An experiment involving a feeding trial and a comparative slaughter was conducted to assess the body chemical composition and patterns of nutrient utilization in pre-ruminant Saanen goat kids. Thirty male kids weighing about 6 kg were divided into five equal groups, one of which was slaughtered as the reference group (G0). The remainder were randomly assigned to four feeding levels of 250, 290, 330 and 370 g goats’ milk per kg M0·75 per day and named as groups GI, GII, GIII and GIV, respectively up to about 15 kg live weight, after which they were slaughtered. Mean milk consumption per unit live-weight gain (LWG) (kg/kg), and daily LWG (g/day), for GI, GII, GIII, GIV respectively were: 13·5 and 110; 10·5 and 160; 10·2 and 180; and 10·3 and 200. Empty body weight (EBW) as a proportion of final live weight was 0·95 in the reference animals, and ranged from 0·80 to 0·88 in the treatment groups. The dry matter (DM) concentration in the empty body of kids increased as their age advanced, from 277 g/kg EBW (G0) to between 308 and 326 g/kg EBW (GI to GIV). The protein and fat concentration of LWGs increased with the level of feeding from GI (142 g crude protein (CP) and 75·5 g fat per kg LWG) to GIV (155 g CP and 109 g fat per kg LWG). Regression of energy retention (ER) on metabolizable energy (ME) intake resulted in an efficiency of ME utilization for body retention (k) of 0·72(± 006). ME requirement for maintenance was estimated as 458 kJ/kg M0·75 per day. Efficiency of nitrogen (N) utilization for growth and N requirement for maintenance were estimated as 0·66(±011) and 0·47 g/kg M0·75 per day, respectively.

The objective of this trial was to examine the daily herbage requirement and grass dry matter intake (DMI) of dairy cows of different levels of milk production with rotational grazing and optimum grazing conditions. The daily herbage allowance (DHA) that was required was defined as the allowance that permitted the herds to graze to a post-grazing sward height (SHA) of 70 mm. Four herds of 15 primiparous Holstein-Friesian cows were assembled with similar characteristics but different milk production potentials. The herds grazed separately and were offered a DHA such that the SHA was 70 mm for all herds. The daily yield per cow, for the 4 weeks prior to the start of the experiment (PMY), was 17·4, 19·8, 21·8 and 24·3 kg milk (s.e.0·20, P < 0·001), 0·72, 0·78, 0·87 and 0·93 kg fat (s.e. 0·021, P < 0·001), 0·59, 0·66, 0·71 and 0·77 kg protein (s.e. 0·009, P < 0·001) for herds 1 to 4, respectively. The experiment began on 30 June and finished on 16 August. The swards offered were 18-day re-growths following a previous defoliation by grazing. Herbage mass pre- and post-grazing was 2143 (s.e.33·3) and 622 (s.e.18·2) kg dry matter (DM) per ha above 40 mm, respectively and were similar for the four herds. The DHA was 21·2, 21·9, 22·9 and 23·9 (s.e. 0·13, P < 0·001) kg DM per cow above 40 mm. Individual cow grass DMI was determined once during the experimental period using the alkane technique. Experimental milk yield (EMY) was 15·1, 17·4, 18·6 and 20·8 (s.e. 0·33, P < 0·001) kg per cow per day. DMI was 14·5, 15·4, 15·5 and 16·1 (s.e. 0·47, P > 0·05). Variations in DMI were best described by the relationship: DMI = 0·85 (s.e. 3·038) + 0·32 (s.e. 0·082) ✕ EMY + 0·012 (s.e. 0·0054) ✕ experimental live weight + 2·10 (s.e. 0·738) ✕ weight gain + 0·020 (s.e. 0·0085) ✕ days in milk (residual s.d. = 1·477 and r = 0·75). EMY was linked to DMI and PMY according to the expression: EMY = –0·64 (s.e. 1·532) + 0·256 (s.e. 0·0865) ✕ DMI + 0·705 (s.e. 0·0620) ✕ PMY (residual s.d. = 1·204 and r = 0·872). It is concluded that higher yielding herds require higher DHA and this is associated with higher DMI of those herds.

Mechanisms underlying milk fat conjugated linoleic acid (CLA) responses to supplements of fish oil were investigated using five lactating cows each fitted with a rumen cannula in a simple experiment consisting of two consecutive 14-day experimental periods. During the first period cows were offered 18 kg dry matter (DM) per day of a basal (B) diet formulated from grass silage and a cereal based-concentrate (0·6 : 0·4; forage : concentrate ratio, on a DM basis) followed by the same diet supplemented with 250 g fish oil per day (FO) in the second period. The flow of non-esterified fatty acids leaving the rumen was measured using the omasal sampling technique in combination with a triple indigestible marker method based on Li-Co-EDTA, Yb-acetate and Cr-mordanted straw. Fish oil decreased DM intake and milk yield, but had no effect on milk constituent content. Milk fat trans-11 C18:1, total trans-C18 : 1, cis-9 trans-11 CLA, total CLA, C18 : 2 (n-6) and total C18 : 2 content were increased in response to fish oil from 1·80, 4·51, 0·39, 0·56, 0·90 and 1·41 to 9·39, 14·39, 1·66, 1·85, 1·25 and 4·00 g/100 g total fatty acids, respectively. Increases in the cis-9, trans-11 isomer accounted for proportionately 0·89 of the CLA response to fish oil. Furthermore, fish oil decreased the flow of C18 : 0 (283 and 47 g/day for B and FO, respectively) and increased that of trans-C18 : 1 fatty acids entering the omasal canal (38 and 182 g/day). Omasal flows of trans-C18 : 1 acids with double bonds in positions from delta-4 to -15 inclusive were enhanced, but the effects were isomer dependent and primarily associated with an increase in trans-11 C18 : 1 leaving the rumen (17·1 and 121·1 g/day for B and FO, respectively). Fish oil had no effect on total (4·36 and 3·50 g/day) or cis-9, trans-11 CLA (2·86 and 2·08 g/day) entering the omasal canal. Flows of cis-9, trans-11 CLA were lower than the secretion of this isomer in milk. Comparison with the transfer of the trans-9, trans-11 isomer synthesized in the rumen suggested that proportionately 0·66 and 0·97 of cis-9, trans-11 CLA was derived from endogenous conversion of trans-11 C18 : 1 in the mammary gland for B and FO, respectively. It is concluded that fish oil enhances milk fat cis-9, trans-11 CLA content in response to increased supply of trans-11 C18:1 that arises from an inhibition of trans-C18 : 1 reduction in the rumen.

An increased sodium appetite has been demonstrated in cattle following supplementation with sodium in the neonatal period, but it is unclear whether the sodium appetite of calves can be influenced in utero by the dam’s sodium intake during pregnancy. Twenty-two non-lactating, pregnant dairy cows received either a diet of silage and concentrates or the same diet with 70 g NaCl per day added to it for the last 2 months of pregnancy. The sodium supplement increased the birth weight of their calves but after 6 weeks there was no difference between treatments in calf weight. In addition to milk, calves in both treatments were offered a choice of concentrates with normal or high sodium concentrations (5·8 and 10·8 g/kg dry matter, respectively). Calves from the cows that had received supplementary sodium during pregnancy ate more of the high sodium concentrate than calves from cows without the sodium supplement, demonstrating that sodium appetite could be entrained by the sodium intake of the dam during late pregnancy.