MJ MJ Metabolizable Energy Research Articles

The effect of pre- and post-partum energy and protein supply on the performance of single- and twin-suckling beef cows and their calves

AbstractChanges in live weight, body condition, milk production and composition were monitored for single- and twinsuckling cows in two experiments. In experiment 1, all cows were managed for 3 months before calving to achieve condition scores at calving 2·1 (low) and 3·1 (moderate). Subsequently, these animals were placed on a fixed level of energy intake (80 MJ metabolizable energy (ME) per day) for 16 weeks. Post-partum diets contained differing amounts of digestible undegradable protein (DUP), but similar amounts of effective rumen degradable protein (ERDP). In experiment 2, single- and twin-suckling cows were fed to achieve a condition score at calving of around 2·75. These animals were subsequently placed on two levels of energy intake (80 MJ and 130 MJ ME per day) during the first 16 weeks of lactation. The diets providing these energy intakes also contained differing amounts of DUP. Neither the level of DUP in the diet nor the level of feeding significantly altered the digestibility of the dry matter or organic matter in the dry matter of the experimental diets.Body condition at calving had little effect on daily milk yield (9·5 kg) and composition (33·5 g/kg fat; 30-0 g/kg protein) in experiment 1. Cows with higher body condition scores at calving lost 13·5 kg more live weight and 0·26 units more body condition (P < 0·05) during the 1st month post partum but remained in better condition throughout the trial period than cows with lower body condition scores. Cows on 130 MJ ME per day produced higher (P < 0·001) daily yields of milk, milk fat and protein (+2·0 kg; +151 g; +85 g) and lost 57 kg less live weight and 0·52 units less body condition (P < 0·001) than cows on 80 MJ ME per day. Elevated dietary levels of DUP promoted (P < 0·05) daily milk yields (by 1·25 kg) and reduced live-weight and body condition-score loss during the 1st month post partum in both experiments. Twin-suckling cows produced the highest average daily yields of milk throughout the 16-week trial period in both experiments but yields were not significantly higher after early lactation in experiment 1. Cow body condition score at calving and the level of DUP in the post-partum diet of cows had no effect on the post-partum performance of calves. Twin calves had slower growth rates (P < 0·001) than single calves (0·65 and 1·07 kg/day respectively) in experiment 1. However, twin calves sucking cows on 130 MJ ME per day in experiment 2 grew similarly to single sucking calves from week 8 of lactation (0·8 kg/day).

The male effect in the Australian cashmere goat. 3. Enhancement with buck nutrition and use of oestrous females

Exposing seasonally anovulatory does to bucks may result in the synchronous onset of fertile reproductive cycling, the male effect. A current limitation to its use is the variable response obtained during spring and summer. The contribution of bucks to this variation was examined in two experiments. In Experiment 1, seasonally anovulatory does were either isolated from bucks (Isolated; n=30) or exposed to bucks previously fed a high quality diet (17.6% crude protein (CP), 8.3 MJ Metabolisable energy (ME) kg −1) (High n=58) or a low quality diet (6.9% CP, 6.6 MJ ME kg −1) (Low; n=60) quality diet, for 10 days in October. Bucks had been maintained on the respective diets for 67 weeks before the experiment ( n=6 per diet). Experimental units comprised groups of nine to ten seasonally anovulatory does exposed to individual bucks in 100 m 2 outdoor pens 100 m apart. By Day 5 the percentage of does that had ovulated was 7, 38 and 71 for the Isolated, Low and High treatments respectively (Isolated < Low < High, P < 0.05) and by Day 10 it was 33, 72 and 81 (Isolated < Low < > High, P<0.05), By Day 10, 38% and 67% of does had exhibited oestrous in the Low and High treatments ( P<0.05) while 28% and 52% respectively, had conceived ( P<0.05). Buck fertility did not differ between treatments. Buck serving capacity and plasma testosterone concentration following exposure to oestrous females were positively correlated with female response variables ( P<0.05). In Experiment 2, anovulatory does were isolated from bucks (Isolated; n=38), exposed to two oestrous does (Oestrous does, n=18), exposed to two oestrous does and a buck (Oestrous does + buck; n=30), exposed to a vasectomised buck (Buck; n=29) or exposed to a ‘hot’ vasectomised buck (Hot buck; n=29), for 10 days in February. ‘Hot’ bucks were bucks that had been exposed to oestrous does for 2 days prior to use. Experimental units comprised groups of nine to ten does in 100 m 2 outdoor pens, 100 m apart. The percentage of does ovulating by Day 5 was 21, 67, 77, 41 and 79, for the Isolated Oestrous does, Oestrous does+buck, Buck, and Hot buck treatments respectively ( P<0.001), and by Day 10 it was 34, 78, 87, 72 and 97 ( P<0.001). We conclude that: (a) natural and nutritionally induced variation between bucks in serving capacity and testosterone response to oestrous does contributes to variation in the ovulatory response of does to buck introduction; (b) exposing bucks to oestrous does may significantly enhance the ovulatory response of does exposed to them; (c) oestrous does are able to induce an ovulatory response in seasonally anovulatory does independently of bucks; (d) separation of treatments by 100 m is insufficient to prevent a small ovulatory response in control does. These findings are integrated into a model of the factors influencing the male effect in goats.

Relationship of post-partum interval in mature beef cows with nutritional environment, biological type and serum IGF-1 concentrations

AbstractMature cows of nine breeds were fed (four cows per level within breed) at either 0·55, 0·71, 0·88 or 1·05 MJ metabolizable energy (ME) per kg initial body weight0·75 per day during non-lactational periods for an average of 4 years. During lactation, energy allowances were increased by 0·17 MJ ME per kg body weight0·75 per day. Breeds represented four biological types: moderate genetic potential for milk yield and growth (Angus, Hereford, Red Poll), moderate milk and high growth (Charolais, Eimousin), high milk and moderate growth (Braunvieh, Pinzgauer) and high milk and growth (Gelbvieh, Simmental). The objective was to test the effects of biological type and nutritional environment on length of post-partum interval as determined from serum progesterone levels. The potential of serum insulin-like growth factor-1 (IGF-1) level at 3 weeks post partum for predicting the length of the post-partum interval was also evaluated. Non-parametric statistical analyses appropriate for right-censored survival data were used to test effects on post-partum interval because collection of serum was terminated prior to ovulation in some cows.Energy availability × biological type effects on post-partum interval were significant. Increased energy availability tended to decrease post-partum interval in all biological types with high potential growth types exhibiting the greatest positive response to increased food. Post-partum interval for types with high growth potential was shorter within food level when associated with high rather than moderate potential for milk yield. Serum IGF-1 was related to post-partum interval at lower energy availability but appeared to have limited usefulness for identifying cows with extended intervals. Inherent direct and maternal production potential interact with available food resources to influence the post-partum interval of mature beef cows.

The effects of dietary protein level during food restriction on carcass and non-carcass components, digestibility and subsequent compensatory growth in lambs

AbstractThe effect of proportion of dietary rumen non-degradable protein during food restriction on the weight of components of the digestive tract, carcass and subsequent growth was investigated in 37 Scottish Blackface wether lambs (initial live weight, 25 kg). Lambs were given individually ad libitum for 4 weeks a complete pelleted diet containing 150 g/kg white fish-meal (HP, 10·4 MJ metabolizable energy (ME) per kg dry matter (DM), 195 g crude protein (CP) per kg DM). Seven lambs were then slaughtered and 15 were switched to a diet containing no white fish-meal (LP, 10·4 MJ ME per kg DM, 122 g CP per kg DM) offered at 18 g DM per kg M per day, i.e. sufficient to maintain constant live weight. A further 15 continued to receive the HP diet at the same rate as the lambs given LP. After 6 and 12 weeks, five lambs on each diet were slaughtered. At 12 weeks the remainder received the HP diet ad libitum for a further 7 weeks before slaughter. During food restriction on both diets, the proportion of live weight formed by the carcass, the dissected components and the chemical composition remained the same as in the initial slaughter group. The relative weight of the non-carcass components fell during food restriction on both diets. There was a significant (P &lt; 0·05) interaction between slaughter date and dietary treatment for reticulo-rumen weight as a proportion of empty body weight (EBM); it was smaller in lambs on the HP diet after 12 weeks of restriction (HP: 0·022, LP: 0·026). A similar pattern was observed for the small intestine and the total digestive tract. During the 7 weeks of realimentation, lambs previously on HP and LP diets had similar intakes (1343 and 1208 g DM per day) and digestive tract components, body components and chemical composition of carcass and non-carcass components were all unaffected by previous treatment. The apparent digestibility of CP of the HP diet was greater than that of the LP diet although it was overall less degradable in the rumen. When both groups of lambs were realimented on the HP diet, there were no differences in the apparent digestibility of any of the dietary components. A high dietary protein: energy ratio during restriction reduced the weight of some of the components of the digestive tract but did not significantly affect carcass composition. The effect did not persist following realimentation and did not significantly influence subsequent performance.

Effects of high rates of inclusion of palm kernel meal in broiler chick diets

The effects of palm kernel meal (PKM) on broiler chicks at dietary inclusion rates above 300 g kg −1 were examined. In Experiment 1, a meal with 142 g crude fibre kg −1 from Sierra Leone (PKM1) was included at 0 (control) and 500 g kg −1 diet (5PKM1) on the basis that PKM1 provided 9.74 MJ metabolisable energy (ME) kg −1. In Experiment 2, a meal with 211 g crude fibre kg −1 from Malaysia (PKM2) was included at 0 (control), 300, 400 and 500 g kg −1 (5PKM2) diet on the basis that PKM2 provided 8.35 MJ ME kg −1. The 5PKM1 diet, containing 63 g supplemental maize oil kg −1 depressed the food intake, growth rate and efficiency of food utilisation of chicks, with 5 week food intakes and body weights being 19 and 22% lower, respectively, than in controls. The 5PKM2 diet, containing 114 g supplemental maize oil kg −1, produced a slightly higher food intake than controls, the body weights of chicks being 3.6% lower at 5 weeks, but similar to those of controls at 7 weeks. The results indicate that PKM is a useful ingredient for broiler chick diets, but at high inclusion rates the texture of PKM-based diets may need to be improved by additional fat to facilitate an adequate level of food intake.

Energiebedarf gravider und laktierender Sauen

The energy requirement of pregnant and lactating sows is derived on the basis of extensive experimental studies of the energy metabolism (indirect calorimetry, slaughtering) according to the factorial method. For the first reproduction cycle (RC) 0.41 MJ metabolizable energy (ME) or 0.29 MJ net energy fat, pig (NEFpig) resp. were necessary for energy maintenance requirement for pregnant and lactating sows and, depending on age, 0.44 MJ ME or 0.31 MJNEFpig in the second or third RC and 0.47 MJ ME/kg LW0.75.d or 0.33 MJ NEFpig/kg LW0.75.d in the 4th-8th RC. A linear increase of up to 6% of the energy requirement caused by pregnancy between the 85th and 115th day of pregnancy is taken into consideration. Energy requirement per 1 MJ retention both in pregnancy and lactation is 1.45 MJ ME or 1.03 MJ NEFpig, per 1 MJ milk yield it is 1.33 MJ ME or 0.91 MJ NEFpig. 1 MJ body energy for milk yield corresponds to 1.20 MJ ME or 0.82 MJ NEFpig. Equations describing energy retention in the products of conception, uterus and udder are established as well as equations characterizing the connections between live weight gain or loss and energy content of the gain or loss.

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 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&lt; 0·05) and food conversion ratios were lower up to a live weight of 43 kg (P&lt; 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&lt; 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.

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.

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.

Nutrition and reproductive performance of dairy cattle 1. The effect of level of feeding in late pregnancy and around the time of insemination on the reproductive performance of first lactation dairy heifers

ABSTRACTOne hundred first lactation Friesian dairy heifers were used to investigate the effect of level of nutrition n i late pregnancy and for a limited period around the time of insemination on reproductive performance. The heifers were housed throughout the period of the trial in cubicle yards and all individuals were given controlled amounts of food.Fifty animals were offered a ‘high’ (H) level of feeding in late pregnancy (for 10 weeks before calving) and 50 were offered a ‘low’ (L) level. After calving, the heifers were re-randomized with half of each pre-calving group being offered either the H or L level of feeding in early lactation (weeks 6 to 18), thus forming four subgroups of 25 heifers: HH, HL, LH and LL. The level of feeding in late pregnancy for all groups increased towards calving. The high plane heifers consumed 83·6 MJ metabolizable energy (ME) per day on average compared with 64·6 MJ ME per day for the low plane heifers, a proportional mean difference of 0·29 (P &lt; 0·001). After calving, heifers consumed an average of 86 MJ ME per day in week 1 rising to 126 MJ ME per day by week 5. Between weeks 6 to 18 of lactation, the high plane group consumed an average of 146·8 MJ ME per day compared with 119·8 MJ ME per day for the low plane group, a proportional mean difference of 0·23 (P &lt; 0001).There were no significant effects of feeding treatments on milk yield. Fat yield in weeks 6 to 18 was increased by the high level of feeding in lactation (P &lt; 0001), while protein yields in weeks 1 to 5 and n i weeks 6 to 18 were increased by high plane feeding in pregnancy (P &lt; 0·05) and lactation (P &lt; 0·05), respectively. Heifers receiving the high level of feeding in late pregnancy gained significantly (P &lt; 0·001) more weight than those on the lower level of feeding. All groups lost similar amounts of weight during the first 5 weeks after calving, but there were marked differences in the rate of live-weight gain between weeks 6 to 11 of lactation (P &lt; 0·05 to P &lt; 0·001). In particular, the HL group had the lowest rate of live-weight gain, and this was significantly lower than that of the HH group (P &lt; 0·01).First ovulation occurred significantly earlier in heifers receiving the high level of feeding in pregnancy P ( &lt; 0·01), but there was no effect of treatment on ovulation detection rate, time to first oestrus, time of first insemination or the proportion of wrongly-timed inseminations. Heifers receiving the high level of feeding in lactation had a successful pregnancy rate to first insemination of 0·42 compared with 0·63 for those on the lower level of feeding (P &lt; 0·05), with the greatest difference observed between the HL group (0·72) compared with the HH group (0·35) (P &lt; 0·01). Embryo loss rate was low in the HL group (008) compared with that in the HH group (0·26; P &lt; 0·l). The net result was that the HH group had a median interval from calving to successful pregnancy of 95 days with an interquartile range of 82 days, whereas the figures for the HL group were 75 and 23 days (P &lt; 0·001). Live-weight change at artificial insemination (AI) and level and change in milk yield at AI had independent effects on reproductive performance and as a consequence net energy output showed the strongest relationship with days to successful pregnancy. Heifers with the highest net energy outputs per day at AI had the longest intervals to successful pregnancy (r = 0·408; P &lt; 0·001).

Nutrition and reproductive performance of dairy cattle 2. Prediction of reproductive performance in first lactation dairy heifers subjected to controlled nutritional regimes

ABSTRACTOne hundred first lactation Friesian dairy heifers were used to investigate the effect of level of feeding n i late pregnancy (83·6 or 64·6 MJ metabolizable energy (ME) per head daily and around the time of first artificial insemination (AI) (weeks 6 to 18 of lactation: 146·8 or 119·8 MJ ME per head daily) on reproductive performance.Heifers receiving the high level of feeding in lactation had a successful pregnancy rate to first AI of 0·42 compared with 0·63 for heifers receiving the lower level of feeding. Heifers receiving the higher level of feeding in late pregnancy followed by the lower level in lactation had a pregnancy rate of 0·72 o t first AI resulting in a median interval from calving to pregnancy of 75 days compared with figures of 0·35 and 95 days respectively, for heifers receiving the higher levels of feeding throughout the experiment (P&lt; 0·001).Blood samples were taken from all heifers 2 weeks before and on weeks 1, 5, 9, 13 and 18 after calving, and were analysed for 13 components. Of the blood components measured, only p"-hydroxy-butyrate concentrations, particularly at week 9, were affected by the nutritional treatments imposed and consistently related to fertility (P&lt; 0·01 toP&lt; 0·001).Milk yield and live-weight change, individually and as the components of net energy output, showed the strongest relationships with reproductive performance (P&lt; 0·01 toP&lt; 0·001). The three variables which together accounted for the highest proportion (0·30) of the variation in days to successful pregnancy were net energy output at AI, (3-hydroxy-butyrate at week 9, and mean tail score in weeks 10 o t 13. These enabled the calving to successful pregnancy interval for an individual or 100 first lactation heifers to be predicted with a 95% confidence interval of ±58 days or ±8·6 days, respectively.

Observed energy intake of weaned piglets and its effect on temperature requirements

ABSTRACTEnergy intake was recorded for two batches of 12 individually-penned piglets weaned at 5 kg live weight and fed milk-based diets of 18·7 MJ metabolizable energy (ME) per kg up to 8 kg live weight and 15.4 MJ ME per kg thereafter. The piglets were kept within their thermoneutral zone throughout the experiments. Regression equations describing the relationship between energy intake and days after weaning were developed for each piglet and the means of the regression coefficients and constants were incorporated in an equation for estimating energy intakes for piglets of 5 to 15 kg live weight. The lower and upper critical temperatures were calculated for each piglet on every day of the trial. These values were extrapolated to give temperature recommendations for piglets of 5 to 15 kg live weight kept in groups of 20. The temperatures ranged from 30°C at weaning to 19°C, 23 days after weaning. This represented a reduction in temperature equivalent to 0·5°C per day.

Effects of body fatness at lambing and diet in lactation on body tissue loss, feed intake and milk yield of ewes in early lactation

SUMMARYThirty-six mature Finnish Landrace × Dorset Horn ewes, each suckling two lambs, were used in a comparative slaughter experiment to measure changes in body tissues during early lactation. Two levels of body fatness at lambing were established by giving ewes a complete diet containing 10 MJ metabolizable energy (ME) and 139 g crude protein (CP)/kg d.m. either close to requirements orad libitumduring the second half of pregnancy. In lactation half the ewes in each group were given a complete diet containing either 90 (diet A) or 60 (diet B) % milled hayad libitum. These diets contained 7·9 and 9·2 MJ ME and 121 and 132 g CP/kg d.m. respectively.Ewes fed at the two levels in pregnancy contained 8·4 and 19·6 kg chemically determined fat 5 days after lambing but had similar amounts of body protein, ash and water. Over 6 weeks of lactation ewes given diet A lost 60 and 69% of these weights of fat respectively, while ewes given diet B gained 5% and lost 30% respectively. Up to 26 g of body protein was lost daily from ewes given diet A but none from ewes on diet B. During early lactation the weight of the empty digestive tract increased while the weights of most other body components, particularly the carcass, decreased. The ratio of body energy change to live-weight change varied from 24 to 90 MJ/kg. Thus live-weight change did not accurately reflect relative or absolute changes in body energy.Voluntary food intake was greater for ewes given the high-energy diet (B) than for those given diet A and was depressed in the fatter ewes. Differences in intake could be explained by the effects of body fatness and diet on the weight of gut contents. Milk yield was not significantly affected by body fat reserves but was higher on diet B than A. Fat content of milk was higher and protein content lower for ewes with the higher fat reserves at lambing.As the contribution of fat loss to energy available for milk synthesis increased there appeared to be a reduction in the energetic efficiency of milk synthesis. A number of possible reasons for this are discussed.