MJ Metabolizable Energy Research Articles

The influence of energy and protein intake on the reproductive performance of the breeding boar: A review

Reproductive performance of a boar can be described by three characteristics: libido, number of sperm cells produced per time unit, and fertilizing capacity of the sperm cells. The influence of energy and protein intake on reproduction in boars has not been studied very thoroughly. The scarce literature indicates that libido is normally not affected by protein or energy intake, although it has been shown that an extremely poor condition as a result of prolonged undernutrition results in reduced libido. From the literature on rams and bulls it is concluded that energy intake at or below the defined maintenance requirement reduced the number of sperm cells produced. For boars, only experiments with very few animals or with feeding levels well above maintenance are available, and they showed no effect on semen production. Data in the literature on the influence of protein intake on the number of sperm cells produced are contradictory. Some authors state that 280 g of crude protein, 11.6 g lysine and 7.2 g methionine plus cystine is enough when feeding 30 MJ metabolizable energy, while other authors state that this should be 743 g of crude protein, 54 g lysine and 37 g methionine plus cystine. It is argued that ejaculation frequency, age and weight of the boar can greatly influence protein requirements. The effect of energy and protein intake on semen quality seems to be very small.

Responses of sexually-maturing pullets to self-selection feeding under different temperature and lighting regimens.

1. Pullets allowed to self-select nutrients from a protein concentrate and either a separate complete diet or cereal-based, energy-rich mixture showed preferences for protein and energy which varied in relation to the time of their onset of lay. 2. The selected protein:metabolisable energy (ME) intake ratio increased from 14 g protein per MJ of ME 2 to 3 weeks before sexual maturity to approximately 19 g protein per MJ of ME at and after sexual maturity. 3. This response to self-selection feeding was consistent with different temperatures, lighting patterns and dietary manipulations. 4. Egg mass output was improved by self-selection feeding at hot (25 degrees to 35 degrees C) temperatures in experiments 1 and 2 and at ambient temperatures in experiment 3. No beneficial response in egg mass from self-selection feeding was observed at cold (6 degrees to 16 degrees C) temperatures in experiment 1. 5. Providing 2 h of additional light during the dark (cool) part of the day, with or without 2 h of darkness in the middle of the extended light (hot) period, had no effect on the egg mass output of pullets at hot (25 degrees to 35 degrees C) temperatures.

The influence of the thermal environment on the voluntary food intake of pigs

AbstractThe thermal components of the environment, through their effects on the animals' heat exchange, influence growth, metabolism and voluntary food intake. The environmental components considered include air temperature, either constant or fluctuating, air movement, relative humidity, group size, stocking density and atmospheric concentrations of various gases and dusts. For the growing pig, it has been calculated that each 1°C change in temperature is associated with a 0.65 MJ metabolizable energy (ME) per day change in energy intake; for the other environmental components the variation was between 0.36 and 0.65 MJ ME per day. From the relation between environmental temperatures, food intake and growth, it was shown that for young pigs the optimum temperature range was between 20 and 25°C; for older animals it was between 10 and 20°C. Knowledge of the extent to which food intake changes with the environmental circumstances, both cold and hot, allows feeding and managemental strategies to be developed to ensure optimum growth and efficiency of food utilization.

The effects of body condition at calving and dietary protein content on dry-matter intake and performance in lactating dairy cows given diets of low energy content

ABSTRACTFour groups of six cows were fed from 12 weeks before calving to achieve condition scores at calving of 3·15 (F) and 2·15 (T). For the first 20 weeks of lactation all cows were given 8 kg concentrate (13·93 MJ metabolizable energy (ME) per kg dry matter (DM), 200 g crude protein (CP) per kg DM) which contained either a high or a low dietary concentration of undegradable dietary protein (UDP) (70 g/kg DM, H, and 49 g/kg DM, L) and 3 kg sugar-beet pulp. Hay was also offered ad libitum.There was no significant effect of treatment on milk yields over the first 20 weeks of lactation (overall mean yield 27·3 (s.e. 3·65) kg/day) but cows in group FL tended to produce less (P > 005). Milk composition was similar for all groups (48·8 (s.e. 5·12) g fat per kg, 27·2 (s.e. 1·48) g protein per kg and 49·0 (s.e. 2·52) g lactose per kg). DM intakes for groups FH, FL, TH and TL were 18·1, 16·9, 17·5 and 18·2 (s.e.d. 0·58) kg/day, respectively (TL v. FL, P < 0·05; FH v. FL, P < 0·05). Mean condition scores for groups FH, FL, TH and TL respectively, were 3·T7, 3·13, 2·21 and 2·08 (s.e.d. 0·18) at calving; 2·25, 2·50, 2·21 and 1·83 (s.e.d. 0·27) in week 10; and 2·46, 2·83, 2·46 and 1·96 (s.e.d. 0·35) in week 20, of lactation. Groups FH, FL, TH and TL lost proportionately 0·09, 0·02, 0·01 and 0·04 (s.e.d. 0·035) of their calving live weights, respectively, over 20 weeks of lactation.It is concluded that increasing the supply of UDP to cows which are fat at calving results in a greater negative energy balance and a small though non-significant increase in mobilization of body fat reserves. At the dietary ME and protein concentrations used, the thin cows could not respond to increased UDP supply and their intake was limited by physical restriction.

The effects of live weight at weaning on growth rate and carcass composition at different stages of maturity in Scottish Blackface lambs fed on two different diets

ABSTRACTThe effects of live weight at weaning on carcass composition were studied with 104 Scottish Blackface lambs offered two diets differing in protein: energy ratio. Groups of lambs were slaughtered at initial live weights of 24·1 (s.e. 1·48) kg (LL) and 28·9 (s.e. 1·67) kg (IL) and at 33 kg, 38 kg, 43 kg, 53 kg and mature live weight.Lambs were offered two diets — low protein: energy ratio (LP, 122 g crude protein (CP) per kg dry matter (DM): 10·4 MJ metabolizable energy (ME) per kg DM) and high protein: energy ratio (HP, 176 g CP per kg DM: 10·4 MJ ME per kg DM). The LP diet was offeredad libitumand the HP diet was restricted to a similar mean level. Muscle, fat and bone tissues in the carcass were separated and weighed and the carcass and non-carcass component tissues were analysed for chemical fat, protein and ash.Daily live-weight gain (DLWG) of HP lambs (148 (s.e. 8·1) g/day) was significantly higher than that of LP lambs (118 (s.e. 8·1) g/day;P< 0·05) and food conversion ratios were lower up to a live weight of 43 kg (P< 0·05). There were no differences in intake or DLWG between LL and IL lambs. Mature live weight (73·3 (s.e. 1·79) kg) was not related to weaning weight or post-weaning diet.There was no effect of diet on carcass composition at any slaughter weight but LL lambs had a higher fat proportion than IL lambs, which was significant (P< 0·05) at 33 kg only. During the feeding period, the increment of fat tissue per unit increase in live weight (348 (s.e. 15·8) g/kg LW) was not affected by live weight at the start of the diet. The difference between LL and IL lambs in fat proportion was directly related to the difference in weight gain required to reach slaughter weight. The difference was not a function of stage of maturity but only of weaning weight, itself largely determined by pre-weaning nutrition. At higher slaughter weights the relative difference decreased and became non-significant. Hence lambs lighter at weaning would be less suitable than heavier lambs for the production of light-weight lean carcasses.

The effect of a high protein intake on sperm production in boars at two semen collection frequencies

A protein rich diet was fed to half of 97 Yorkshire boars maintained at two semen collection frequencies in two experiments measuring sperm production and semen quality. The boars were fed a control diet (12.56 MJ metabolizable energy (ME) per kg, 14.5% crude protein, 0.68% lysine and 0.44% methionine plus cystine) or an isocaloric diet with increased protein content (12.56 MJ ME per kg, 22.2% of crude protein, 1.20% lysine and 0.81% of methionine plus cystine). The sperm collection occurred either three to four or six times in two weeks (low or high collection frequency). None of the parameters were influenced by amino acid supply. The semen collection frequency influenced the number of ejaculated sperm cells ( P < 0.0001). The number of ejaculated sperm cells per day was increased if the semen collection frequency increased. Sperm quality was not influenced by semen collection frequency. The control diet contained enough protein to ensure good sperm production of a boar used for Artificial Insemination.

Blood and tissue lipid composition and lipase activity in wether lambs treated with trenbolone acetate combined with oestradiol-17 β at two different live weights

AbstractThirty-two Border Leicester ♂ × Scottish Blackface ♀ wether lambs aged about 5 months, were divided on the basis of live weight such that group G1 contained the 16 lightest lambs and group G2 the 16 heaviest lambs. Lambs in group G1 were subdivided equally at random to be either sham-implanted controls (group C1) or to be implanted with 35 mg trenbolone acetate (TBA) + 5 mg oestradiol-17β (OE) (group T1) at 24 kg initial live weight. Lambs in group G2 were also subdivided into two groups (C2 and T2) and similarly treated approximately 1 month later at 37 kg initial live weight. Animals were offeredad libitum, a diet containing an estimated 12·5 MJ metabolizable energy and 140 g crude protein per kg dry matter. The experimental treatments lasted for 60 days.Samples of pre-heparin plasma were analysed for free fatty acid (FFA) and triglycerides (TG). Post-heparin plasma was analysed for lipoprotein lipase (LPL) activity. Samples of subcutaneous (SCAT), perinephric (PNAT), mesenteric (MAT) and intermuscular (IMAT) adipose tissue, liver and muscle, taken immediatelypost mortem, were analysed for total lipid concentration and fatty acid composition. Comparisons were made for the main effects of hormonal treatment and live weight.Plasma FFA concentrations in heavier lambs (group G2) were significantly higher than in group G1 from week 1 pre-implantation to week 3 post implantation. Compared with group G1, animals in group G2 had significantly higher plasma TG concentrations at weeks 1, 2, 5 and 8 when data was analysed using pre-implantation values as covariates. The lipid concentration was lower in group G1 than in group G2. In group G1 compared with group G2 there were greater proportions of C12:0 and C18:2 in SCAT and C16:1 in PNAT and lesser proportions of C18:0 in SCAT and PNAT.Significant effects due to hormonal treatment were recorded for plasma TG at weeks 1, 5, 6, 7 and 8 mainly due to increases in group T1 compared with group C1. Hormonal treatment increased the proportions of C12:0, C15:0, C16:1 and C18:1 in SCAT and C16:1 and C18:1 in IMAT; reduced the proportions of C16:0 and C18:0 in SCAT and C18:0 in MAT and IMAT and reduced the ratio of saturated to unsaturated fatty acids in SCAT and IMAT and to a lesser extent in MAT.

Growth performance and body composition of wether lambs implanted at two different initial live weights with trenbolone acetate combined with oestradiol-17β

AbstractThirty-two Border Leicester ♂ × Scottish Blackface ♀ wether lambs, aged about 5 months, were divided into two groups on the basis of live weight, such that group G1 contained the 16 lightest lambs and group G2 the 16 heaviest. Lambs in group G1 were subdivided equally at random either to be sham-implanted controls (Group C1) or to be implanted with 35 mg trenbolone acetate (TBA) + 5 mg oestradiol-17β (OE) (group T1) at 24 kg initial live weight. The lambs in group G2 were also subdivided into two groups (groups C2 and T2), and similarly treated approximately 1 month later at 37 kg initial live weight. The lambs were offered ad libitum a diet containing an estimated 12·5 MJ metabolizable energy (ME) per kg dry matter (DM) and 140 g/kg DM crude protein. Comparisons were made for the main effects of hormonal treatment and initial live weight. Both hormonal treatment and initial live weight gave increases for DM intake, gut fill, empty body weight, carcass weight and, in the half carcass side weight, weights of dissected lean tissue, bone and intermuscular fat and chemically determined DM, crude protein and lipid. Weights of mm. semitendinosus, longissimus dorsi, supraspinatus and gastrocnemius were also increased due to hormonal treatment and in group G2 lambs compared with those in group G1. When expressed as a proportion of carcass side weight, hormonal treatment effects were not significant for individual muscles and dissected carcass lean, bone and fat and chemically determined lipid and ash. Variable effects on other body components were recorded for both treatments in the absence of any significant interactions. The responses to hormonal treatment were essentially similar in groups G1 and G2. The question is raised as to the contribution of the greater food intake in implanted lambs to the maintenance of fatness in these animals.

Rapeseed meal in the diet of pubertal heifers during early pregnancy

AbstractThe 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 &gt; 0·05). Foetuses from heifers given rapeseed meal were slightly smaller than those from control heifers; the difference was significant in year 2 (P &lt; 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 &lt; 0·001; year 2, P &lt; 0·05). Plasma thiocyanate was elevated in rapeseed meal heifers in both years (P &lt; 0·001) compared with values for control animals.

Nitrogen kinetics in cattle fed a mature subtropical grass hay with and without protein meal supplementation

Ammonia kinetics in the rumen, and the rates of urea synthesis, excretion, and recycling to the rumen and post-ruminal digestive tract were estimated by means of tracer dilution methods in eight 12-monthold Hereford steers, all given free access to a mature, subtropical grass (Axonopus spp.) hay (7.8 g N and 5.8 MJ of metabolizable energy (ME)/kg dry matter). These estimates were made towards the end of a 45-day study, including a 12-day adjustment period, and 33 days in which four steers were supplemented with pelleted protein meal and minerals; the other four were supplemented only with minerals. After 10-20 days of supplementation (days 23-32 of the experiment), the voluntary intake of hay was 19% higher (P &lt; 0.05) in supplemented compared with non-supplemented steers, and from days 33 to 42 was 23% (P &lt; 0.01) higher. Therefore, during the period between days 22 and 42 of the experiment when ammonia and urea kinetics were estimated, total ME and N intakes were higher (30 v. 22 MJ/day and 71 v. 29.5 g N/day), and liveweight gain was also higher (P &lt; 0.01) in supplemented steers (800 v. 200 � s.e.d. 88 g/day). Ammonia and volatile fatty acid concentrations in rumen fluid were higher (P &lt; 0.05) in supplemented steers (55 v. 7 mg N/l and 93 v. 77 mmol/l respectively). The rate of synthesis of urea in the body, and the concentrations of urea in plasma and saliva, predominantly of parotid origin, were also higher (P &lt; 0.01) in supplemented steers. Non-supplemented steers appeared to conserve nitrogen, excreting only 0.41 g urea N/day in urine, which was less than 3% of their daily urea synthesis compared with 9 g N/day or 21% of the daily urea synthesis in supplemented steers. More urea N (P &lt; 0.01) was recycled to the digestive tract in supplemented than in non-supplemented steers, but in either case c. 60% of the total amount recycled was transferred to the rumen. A model summarizing N transactions in the body is presented for steers on the basal hay diet and when supplemented with the pelleted meal.

EFFECT OF SUPPLEMENTARY HAY FED TO NON-LACTATING COWS OFFERED TWO ALLOWANCES OF PASTURE

The objective of this study was to measure the effects of giving hay as a supplement to cows grazing at two different daily herbage allowances. Pregnant, non-lactating Friesian cows were allocated to four treatments: low herbage allowance with hay (LA+) or wthout hay (LA); and high allowance with hay (HA+) 01 without hay (HA). Hay was fed at 5 kg DM/cow daily, and the two herbage allowances were 9 or 14 kg DM/cow daily. Supplementing with hay increased total dry matter (DM) intake, but decreased herbage DM intake at both allowances. The decreases in herbage intake were 0.26 and 0.40 kg herbage OM eaten per kg hay DM eaten, at the lower and higher allowances respectively. The corresponding values, expressed as MJ metabolisable energy (ME), were decreases of 0.44 and 0.65 MJME from herbage per MJME eaten as hay. The decreases in herbage intake resulted in increases in residual herbage yield at both allowances. The implications of these results for grazing management during the winter are brlefly discussed. Keywords: supplementary feeding, hay, substitution rate, condition score, dairy cattle.

Voluntary food intake of cattle differing in breed size in a time-controlled feeding system

ABSTRACTSix breeds differing widely in body size and milk yield were compared for growth and food intake between 24 and 120 weeks of age in a time-controlled feeding system based on Calan-Broadbent electronic feeding gates activated by time clocks to give six meals a day of length 4, 5 or 6 min. The breeds were South Devon, Charolais × British Friesian, British Friesian, Hereford, Aberdeen Angus and Jersey. Each breed was represented by 12 animals, with four allocated to each meal length.At every age, voluntary food intake was strongly determined by meal length. For each meal length, and after adjustment for breed size, most breeds closely followed the same intake curve. Thus, when intake was restricted (either slightly or severely) by uniformly limiting the time available for eating, the reduced voluntary daily intake of a breed, like its ad libitum intake, was largely genetically determined by breed size. A time-controlled feeding system thus allowed acceptable breed comparisons under conditions of restricted nutrition.The mean growth rates resulting from a wide variety of different time-controlled voluntary intakes were all adequately explained by a linear equation based on a constant maintenance efficiency and a partial efficiency of growth that declined linearly with degree of maturity in body weight.Eating rate was surprisingly similar for the three different meal lengths. When averaged over breeds, it increased from 1 MJ metabolizable energy (ME) per min between 6 and 12 months of age up to about 2 MJ ME per min at 2 years of age. Over this range, eating rate could be expressed as an allometric function of degree of maturity in body weight. In consequence, time-controlled daily intakes could be predicted from eating rate within ad libitum limits, as could the total eating time needed to achieve a given growth rate.

Carcass composition of veal calves dependent on genotype and feeding level

ABSTRACTDutch Friesian purebred and Holstein Friesian-Dutch Friesian crossbred veal calves were used to study effects of genotype and feeding level on carcass composition. Carcass analyses were carried out on a total of 56 calves of two genotypes. Calves were reared for 22 weeks and given food dependent on age. From 1 to 16 weeks calves were given the same amount of milk replacer. At week 16, calves were assigned to either a high or low feeding level. Total energy intakes for the two groups were 5062 MJ metabolizable energy (ME) and 5408 MJ ME, respectively. Carcass weight and carcass composition traits showed no significant interaction between genotype and feeding level. Dutch Friesians had higher lean: bone ratios than Holstein Friesian crossbreds (3·85 v. 3·67). Differences between the two genotypes for fat and lean proportions in the carcass were not significant. Average proportions for lean and fat were 653 and 134 g/kg.Differences between the two feeding levels for carcass composition were significant. Calves on the low feeding level had 655 g lean and 131 g fat per kg, while calves on the high level had 645 g lean and 143 g fat per kg.The influence of the dissection technique on the differences in lean and muscle proportion between groups was studied on 18 carcasses using a standardized butcher's method (the Institute of Animal Husbandry (IVO) standard method) and the European Economic Community (EEC) reference method for beef. Average proportion of lean was 640 g/kg by the IVO method and of muscle was 557 g/kg by the EEC method. The difference between the two genotypes for lean proportion was smaller by the' EEC method due to the more complete separation between muscle and fatty tissue. Dutch Friesians had more intermuscular fat than Holstein Friesian crossbreds. Results of the EEC reference method indicate differences between the two feeding levels for fat as well as for protein deposition.

Effects of body condition, food intake and temporary calf separation on the duration of the post-partum anoestrous period and associated LH, FSH and prolactin concentrations in beef cows

ABSTRACTAn experiment was conducted to examine factors affecting the length of the post-partum anoestrous period and associated effects on LH, FSH and prolactin. Forty-six cows (24 Hereford × Friesian and 22 Blue-Grey) ranging in body condition score at calving from 1·50 to 2·75 were used. They were individually fed chopped barley straw and concentrate at either 50 (low) or 91 (high) MJ metabolizable energy per day from calving. At 34 days post partum half the cows were separated from their calves for 48 h. The duration of the post-partum anoestrous period was estimated from progesterone concentrations in thrice weekly blood samples. Blood samples were collected every 20 min for 10 h periods immediately prior to calf separation, during the last 10 h of calf separation and 1 week later. All samples were analysed for LH, and every third sample was analysed for FSH and prolactin.There were no significant effects of genotype, feeding level or calf separation on the length of the post-partum anoestrous period. There was a negative association between body condition score at calving and the length of the anoestrous period, with each unit increase in body condition score reducing the anoestrous period by 43 (s.e. 20) days. There was some evidence that feeding level affected the number of thin cows (body condition score ≤2·25 at calving) which were still acyclic at the end of the experiment, but not the number of fat cows (body condition score ≥2·5 at calving).FSH levels were not affected by any of the factors examined. Prolactin concentrations were higher in fatter cows, in cows on the higher level of feeding and in Blue-Grey cows. Prolactin concentrations decreased during the period of calf separation. Genotype and feeding level had no effect on LH concentration or LH pulse frequency. LH pulse frequency was increased (P &lt; 0·05) during the period of calf separation, but there was no effect 1 week later. There was a significant positive relationship between LH puise frequency and body condition score at calving in two of the three sampling periods.It is suggested that the effect of body condition on the duration of the post-partum anoestrous period i s mediated through effects on LH pulse frequency.

STEAM-HEATED CULLED BEANS: NUTRITIONAL VALUE AND DIGESTIBILITY FOR SWINE

White culled beans were steamed at 80 or 100 °C at various time intervals to determine the conditions necessary to inactivate the trypsin inhibitors and hemagglutinins. Steaming at 100 °C for 30 or 45 min in a covered mixer completely destroyed the hemagglutinating activity and greatly reduced the trypsin inhibitor activity of the beans. The nutritional value of the processed beans was evaluated in two digestion experiments. The inclusion of 34.5% beans steamed at 100 °C for 30 or 45 min in the diet depressed feed intake and induced scours in the pig. On the other hand, beans steamed for 75 min were readily consumed by the animals and did not induce scours. Beans steamed at 100 °C for 75 min supplied 12.9 MJ of digestible energy, 12.6 MJ of metabolizable energy, 103 g digestible protein, 1 g of absorbable calcium and 2.9 g of absorbable phosphorus per kilogram. The processed beans should thus be considered as an energy source for swine. Key words: Beans, digestibility, nutritional value, swine, steam processing

Metabolic utilization of energy and maintenance requirements in pregnant sows

Energy and nitrogen balances were measured in two experiments involving 32 Large-White gilts kept in respiration chambers and given a constant diet providing 27.6 MJ metabolizable energy (ME) per day (Experiment 1) or 32.7 MJ ME per day (Experiment 2). Measurements were made on the same animals at mid (Day 50–80) and late (Day 95 to farrowing) pregnancy in both experiments and also during early pregnancy (Days 30–50) in experiment 2. A total of 90 balances were performed. Advancement of pregnancy was associated with an increase in protein deposition and in heat production (67 kJ day −1 for a constant metabolizable energy (ME) intake) which resulted in reduced energy and fat deposition. Maintenance requirements (420–430 kJ ME kg −1 W C.75) were constant over pregnancy. Efficiencies of ME utilization for uterine ( k u) and maternal ( k r) deposition were 40–50% and about 80%, respectively. Efficiencies for protein ( k p) and fat ( k f) deposition were 58–67% and 80–90%, respectively. Additional heat loss with advancement of pregnancy (0.53 kJ kg −1 W 0.75 day −1 of pregnancy) is related to the changes in the composition (protein vs. fat) and localization (uterine vs. maternal tissues) of the energy gain and not due to extra heat production arising from the pregnancy itself.

Studies on reproduction in prolific ewes

SummaryIn Expt 1, 34 individually-penned Finn Dorset ewes of mean live weight 68 kg were synchronized in oestrus and mated to Suffolk rams. From mating until day 28 of pregnancy each received daily 15 MJ of metabolizable energy (ME) and 225 g crude protein (CP). From day 28 to slaughter on days 34, 41, 48 or 55 half of the ewes continued on this feeding regime and half had their daily intake reduced abruptly to 7·5 MJ of ME and 112 g CP. The mean number of ovulations per ewe was 4·03 (range 2–8) and the mean number of viable foetuses at time of slaughter 3·35 (range 2–6). The combined loss of ova (fertilization failure and early embryonic death) was 14·6% and detectable foetal deaths 2·2%. Level of feeding had no significant effect on these measures or on foetal growth. Foetal growth from 34 to 55 days was described by the equationIn w = 0·962–18·613 e-0·0272t–0·00091t(f–3),where w = foetal weight (kg), t = age (days) and f = litter size. Within-litter variability measured as the S.D. of In w (kg) was 0–081 for twins, 0·108 for triplets and 0·106 for quadruplets and higher multiples.In a second experiment Suffolk × Finn Dorset embryos were transplanted at the rate of two per uterine horn into 15 recipient Finn Dorset ewes. Embryo survival was 72% and foetal weights at 60 days varied from 67 to 146% of the mean value of 66 g. Withinlitter variation in foetal size was only about 70% of that expected for foetuses developing from the variable distribution in their initial positioning that occurs naturally. The correlation between foetal weight and placental weight at day 60 was 0·72 (P &lt; 0001) indicating that the association between foetal weight and placental weight in prolific ewes is not confined to late pregnancy.The results of both experiments are consistent with the hypothesis that the greater within-litter variability in birth weight in large litters is controlled by events in early pregnancy.

Untersuchungen zur Energie- und Proteinkonzentration von Broilerrationen in Kuba

A total of 1,900 male broilers of the variety White Plymouth Rock was tested with 4 energy concentrations (10.5, 11.5, 12.6 and 13.6 MJ metabolizable energy/kg) and 4 protein concentrations (15.0, 17.5, 20.0 and 22.5% CP) in their first 56 days of life in 16 test groups. The animals were kept in cages and were directly exposed to the natural Cuban summer temperatures from their 15th day of life onwards. As every test group was run with 6 repetitions, the results could be variance analytically calculated. In a comparison of the behaviour of the male animals in winter and in summer it can be stated that the animals took in between 3.4 and 25% more feed in winter than in summer. In general, a lower body protein and body fat amount could be found in all test groups in summer compared to that in winter. Feed expenditure and the utilization of energy and protein were not as good as in winter. It could be shown that both maximum live weight and live weight gain can be achieved in the 2nd fattening period in the Cuban summer if rations containing 12.6 MJ metabolizable energy and 20% CP are fed in a one-phase feeding system.

Effects on food intake, rumen development and live weight of calves of replacing barley with sugar beet-citrus pulp in a starter diet

ABSTRACTIn three experiments the effects of replacing barley with citrus or unmolassed beet pulp in starter diets for calves was examined. In experiment 1, 40 Friesian bull calves were offered to appetite from 14 to 91 days of age one of four complete pelleted diets, each of which contained 200 g ground straw per kg and n i which the ratio of barley to pulp (citrus and beet pulp in the ratio 1:1) was 100:0 (A); 67:33 (B); 33:67 (C) and 0:100 (D). All diets contained 12·1 MJ metabolizable energy and 187 g crude protein per kg dry matter (DM). Milk replacer containing 200 g fat per kg was offered once daily (0·44 kg/day) until day 49 when the calves were abruptly weaned. Up to weaning (days 14 to 49) and after weaning (days 50 to 91) intake of DM was significantly increased by replacing barley with pulp (P&lt; 0·05). Intakes (kg DM per day) of diets A, B, C and D were 0·31, 0·44, 0·51 and 0·50 before weaning and 2·07, 2·08, 2·23 and 2·38 after weaning. Weight gains (kg/day) of calves given pulp tended to be higher before weaning (0·44v.0·58 for Av.mean of B, C and D) but lower after weaning (0·73v.0·68) than of calves given the cereal-based diet. In experiment 2, 65 calves were given diets similar to A and C except that the pulp was supplied totally by unmolassed beet pulp, they were given only 0·35 kg milk replacer per day and weaned on day 35. The results were similar to those obtained in experiment 1; between days 14 to 84 intake was higher (P&lt; 0·05) and there was a tendency for weight gain to be higher in calves given the diet containing pulp. The DM digestibility of the diets decreased significantly with inclusion of pulp (P&lt; 0·05); digestibility of nitrogen was severely depressed but there was an increase in digestibility of acid-detergent fibre. Growth rate was possibly restricted by the availability of nitrogen in diets containing pulp.

The utilization of wilted and unwilted silages by lactating cows and the influence of changes in the protein and energy concentration of the supplement offered

ABSTRACTTwenty-four lactating British Friesian cows were used in a four-period partially balanced change-over design experiment to evaluate eight treatments consisting of two silage types (wilted and unwilted), each offered in addition to supplements containing both two crude protein (CP) levels (160 and 210 g/kg fresh weight) and two energy levels (10·8 and 12·9 MJ metabolizable energy (ME) per kg fresh weight) obtained by including 100 g spray-dried tallow per kg, in a 2 × 2 × 2 factorial arrangement. All supplements were offered at ttie same rate of 6·8 kg/day and total diet digestibility and food utilization studies were carried out on all animals at the end of the final period of the experiment. A separate two-period change-over design expeximent, using two lactating cows fitted with rumen cannulae, was undertaken to determine the influence of the two silages on volatile fatty acid (VFA) proportions in the rumen and to measure the rates of disappearance of dry matter (DM) and nitrogen in the silages and supplements from the rumen.There were no significant interactions between silage and supplement type in terms of animal performance. Animals offered unwilted silage consumed proportionately 003 less DM but produced 0·03 more milk than those offered wilted silage. Although total diet digestibility was not influenced by silage type because of the higher gross energy concentration of the unwilted silage the ME intake with this diet was higher than with the diet based on wilted silage and the ratios of milk energy output to ME available for production (0·54) were similar with both silages. Silage type had no effect on the rumen VFA proportions but influenced the jates of disappearance of DM and nitrogen from the rumen.Increasing the CP concentratioryof the supplement had no effect on the intake of silage DM but resulted in a significant incrase in milk yield (0·55 kg/day) but due to a reduction in milk fat concentration there was np etfect on yield of either fat-corrected milk or milk energy. The use of the higher energy supplement depressed the intake of silage DM by 0·46 kg/day but resulted in an increase in milk yield of 0·74 kg/day. Neither CP nor energy concentration of the supplement had any effect on DM or energy digestibility of the total diet but there were considerable differences between supplements in the patterns of nitrogen and DM disappearance from the rumen.