Lactation Food Intake Research Articles

Limits to sustained energy intake. XXX. Constraint or restraint? Manipulations of food supply show peak food intake in lactation is constrained.

Lactating mice increase food intake 4- to 5-fold, reaching an asymptote in late lactation. A key question is whether this asymptote reflects a physiological constraint, or a maternal investment strategy (a 'restraint'). We exposed lactating mice to periods of food restriction, hypothesizing that if the limit reflected restraint, they would compensate by breaching the asymptote when refeeding. In contrast, if it was a constraint, they would by definition be unable to increase their intake on refeeding days. Using isotope methods, we found that during food restriction, the females shut down milk production, impacting offspring growth. During refeeding, food intake and milk production rose again, but not significantly above unrestricted controls. These data provide strong evidence that asymptotic intake in lactation reflects a physiological/physical constraint, rather than restraint. Because hypothalamic neuropeptide Y (Npy) was upregulated under both states of restriction, this suggests the constraint is not imposed by limits in the capacity to upregulate hunger signalling (the saturated neural capacity hypothesis). Understanding the genetic basis of the constraint will be a key future goal and will provide us additional information on the nature of the constraining factors on reproductive output, and their potential links to life history strategies.

Glucogenosis Hepática. Características clínicas, laboratoriales e imagenológicas en pacientes pediátricos menores de 15 años

Antecedentes: La glucogenosis (GSD) hepática es una enfermedad hereditaria autosómica recesiva caracterizada por la alteración del depósito de glucógeno en los tejidos. La enfermedad se presenta con hepatomegalia, debilidad muscular y retraso del crecimiento. Esta patología usualmente se diagnostica clínicamente a partir de los 6 meses de edad cuando la ingesta de alimentos del lactante es más espaciada y puede debutar con sintomatología de hipoglicemia. Debido a la inespecificidad de la presentación clínica de la enfermedad es muy importante la sospecha diagnóstica desde los centros de primer nivel de atención y su derivación oportuna a centros de especialidad. Objetivo: Evaluar y describir el perfil nutricional y clínico en pacientes menores de 15 años con Glucogenosis Hepática. Método: Se describe una serie de casos de 14 pacientes menores de 15 años con diagnóstico clínico de GSD hepática, atendidos en la consulta de Gastroenterología y Nutrición Pediátrica del Hospital Carlos Andrade Marín entre 2016 y 2018. El diagnóstico se lo realizó de acuerdo a la clínica que presentó cada paciente como la presencia de distensión abdominal, hepatomegalia, adinamia, retraso en el crecimiento y datos laboratoriales como niveles de glicemia en sangre periférica, transaminasas, y realización de elastografía entre los principales. Se analizaron datos sociodemográficos, antropométricos, de laboratorio (transaminasas, glicemia periférica) y elastografía hepática. Para el análisis de datos se creó una base de datos en Microsoft Excel 2013 y se procesó con el programa Epi Info 7. Resultados: En este grupo de casos, los tipos específicos de GSD hepática fueron tipo IX, 57,14% (8), tipo III, 28,57% (4) y tipo Ia-b, 14,29% (2) pacientes. La prevalencia de características clínicas ante la sospecha de la GSD hepática fueron: hepatomegalia 100% (14), y retraso en el crecimiento el 64,3% (9). De acuerdo a los exámenes de sangre periférica los valores promedio de transaminasas hepáticas (AST/TGO U/L) (ALT/TGP U/L) y glucosa, fueron de 364±384, 302±255 y 61±15 mg/dL, respectivamente. La elastografía con la que se evaluó el nivel de fibrosis hepática al momento del diagnóstico arrojó los siguientes resultados: F0 (no fibrosis hepática) en el 28,57% (4), F1 con el 28,57% (4), F2-F3 con el 35,71% (5), y F4 7,14%. Conclusión: La Glucogenosis es una patología que debería ser sospechada a tiempo en centros del primer nivel de salud para luego referir oportunamente los casos a los centros de referencia. La hepatomegalia y el retardo en el crecimiento son signos cardinales de alerta para la sospecha de esta patología.

Oxidative costs of reproduction: Oxidative stress in mice fed standard and low antioxidant diets

Lactation is one of the most energetically expensive behaviours, and trade-offs may exist between the energy devoted to it and somatic maintenance, including protection against oxidative damage. However, conflicting data exist for the effects of reproduction on oxidative stress. In the wild, a positive relationship is often observed, but in laboratory studies oxidative damage is often lower in lactating than in non-breeding animals. We hypothesised that this discrepancy may exist because during lactation food intake increases many-fold resulting in a large increase in the intake of dietary antioxidants which are typically high in laboratory rodent chow where they are added as a preservative.We supplied lactating and non-breeding control mice with either a standard or low antioxidant diet and studied how this affected the activity of endogenous antioxidants (catalase, superoxide dismutase; SOD, and glutathione peroxidise; GPx) and oxidative damage to proteins (protein carbonyls, PC) in liver and brain tissue. The low antioxidant diet did not significantly affect activities of antioxidant enzymes in brain or liver, and generally did not result in increased protein damage, except in livers of control mice on low antioxidant diet. Catalase activity, but not GPx or SOD, was decreased in both control and lactating mice on the low antioxidant diet. Lactating mice had significantly reduced oxidative damage to both liver and brain compared to control mice, independent of the diet they were given.In conclusion, antioxidant content of the diet did not affect oxidative stress in control or reproductive mice, and cannot explain the previously observed reduction in oxidative stress in lactating mammals studied in the laboratory. The reduced oxidative stress in the livers of lactating mice even under low antioxidant diet treatment was consistent with the ‘shielding’ hypothesis.

Limits to sustained energy intake. XI. A test of the heat dissipation limitation hypothesis in lactating Brandt's voles (Lasiopodomys brandtii)

The maximum rate of sustained energy intake (SusEI) may limit reproductive effort, thermoregulatory capability and other aspects of an animal's energy expenditure. Consequently, factors that limit SusEI are of interest. The ;heat dissipation limitation hypothesis' suggests that maximum SusEI during lactation is limited by the capacity to dissipate body heat generated as a by-product of processing food and producing milk. In the present study, we tested the heat dissipation limitation hypothesis in lactating Brandt's voles (Lasiopodomys brandtii). Female voles were mated and pregnant at 21(+/-1) degrees C. A random sample of animals was transferred into a hot room 30(+/-1) degrees C on the day of parturition. The energy intake of lactating voles at 30 degrees C was always lower than that at 21 degrees C. At peak lactation food intake was 3.3 g day(-1) lower at 30 degrees C than at 21 degrees C. There was no significant difference in digestibility. With similar mean litter sizes (7.26+/-0.46 pups at 21 degrees C and 7.78+/-0.39 pups at 30 degrees C at the beginning of parturition, 6.83+/-0.51 pups at 21 degrees C and 7.73+/-0.50 pups at 30 degrees C at weaning), the milk energy output of mothers, evaluated from the difference between metabolizable energy intake and daily energy expenditure measured by doubly labelled water, at 30 degrees C was 23.3 kJ day(-1) lower than that at 21 degrees C on days 14-16 of lactation. As for reproductive performance, there was a difference in the response to the higher temperature between mothers raising large and those raising small litters. For small litters (<7) there was no significant change in litter mass, but for large litters (<or=7) there was a significant decrease at the higher temperature. On average, in larger litters the pups were 15.5 g heavier on day 12 of lactation when raised at 21 degrees C. Our data from Brandt's voles support the suggestion that SusEI at peak lactation is limited by heat dissipation capacity, particularly for those voles raising large litters. In smaller litters the peripheral limitation hypothesis may be more relevant. The importance of heat dissipation limits in species raising exclusively small litters needs to be investigated.

The relationship of food intake during growth and food intake at maturity with lactation food intake in a mouse model

Selection for increased leanness and improved food efficiency in pigs has resulted in a decreased voluntary food intake. It has been argued that voluntary food intake during lactation should be considered in sow breeding programmes. The aim of the present study was to investigate the phenotypic correlation of food intake during growth and food intake at maturity with maximum lactation food intake in a mouse model. A total of 179 records were available on female mice selected for litter size at birth (S-line) and non-selected control females (C-line) from 3 weeks of age to 21 days in lactation. Half of the litters were standardized to eight pups per litter (s) and half were not standardized (ns). Growth intake was measured as the average intake between 21 and 42 days of age, mature intake was measured from a linear regression of food intake against age between 42 and 69 days of age, and lactation intake was measured as a linear regression of food intake against days in lactation between 5 and 14 days in lactation. In both lines, females with a higher growth intake also had a higher mature intake ( r = 0.63 to 0.75, P < 0.0001). Lactation intake was related with growth intake and mature intake in Sns females ( r = 0.50 and 0.46, P < 0.01) and with growth intake in Ss females ( r = 0.32, P < 0.05). In both lines, lactation intake was highly correlated with litter weight ( r = 0.48 to 0.94, P < 0.001). Sns and Ss females with higher growth intake supported larger litter weights during lactation ( r = 0.32 and 0.30, respectively, P < 0.05) and Sns females with higher mature intakes tended to support larger litter weights ( r = 0.28, P = 0.060). It is suggested that lactating C-line females eat to support a given litter size, while S-line females support the maximum litter weight that is allowed for by their intake capacity, and still produce at high levels when litters are standardized. Since lactating sows mobilise body reserves, the relationship of food intake during growth with that during lactation may be reflected in the relationship between growth intake and body condition.

The effect of feeding salmon oil to sows throughout pregnancy on pre-weaning mortality of piglets

AbstractSalmon oil (16·5 kg /t), a source of long-chain polyunsaturated n-3 fatty acids, was included in diets offered to multiparous sows during pregnancy and lactation to measure responses in pre-weaning mortality and performance of piglets in two studies. The first study, carried out under commercial conditions, included 196 sows which were offered salmon oil and control diets from immediately post service until weaning. The same diets were also offered to 10 sows per treatment from day 58 of pregnancy in a controlled nutritional study which measured the effects of salmon oil on piglet tissue fatty acid composition. Offering salmon oil to the sow significantly increased gestation length and decreased individual piglet birth weight but had no effect on litter size at birth. Overall, salmon oil reduced pre-weaning mortality from 11·7% to 10·2% mainly by reducing the incidence of deaths from crushing by the sow. More detailed analysis of mortality using a general linear mixed model and 2294 piglet records, demonstrated that the incidence of pre-weaning mortality was significantly decreased with increasing individual piglet birth weight and by inclusion of salmon oil in the diet; the incidence of mortality increased with average piglet birth weight in a litter. Salmon oil inclusion had no effect on weight of litter weaned, sow lactation food intake or subsequent reproductive performance. In both studies, dietary salmon oil increased the proportions of long-chain n-3 polyunsaturated fatty acids in colostrum to a similar extent. In the nutritional study, inclusion of salmon oil reduced the proportions of 20: 4 n-6 in piglet liver and brain at birth and increased the proportions of long-chain n-3 polyunsaturated fatty acids. Therefore, despite reducing piglet birth weight, offering sows salmon oil reduced pre-weaning mortality of piglets. The nutritional study showed that the amount and type of marine oil used may not have been optimal.

Increasing food intake in late gestation improved sow condition throughout lactation but did not affect piglet viability or growth rate

AbstractIncreasing sow food intake in late gestation prevents loss of sow fatness prior to farrowing. However, this may result in reduced food intake and greater overall fat loss during lactation and has also been associated with increased incidence of agalactia. In this experiment 78 Camborough sows (parities 1 to 3) were given food at one of two levels: either 1·15×maintenance energy (normal-N sows, 2·3 (s.e. 0·03) kg/day) or 2·00×maintenance energy (high-H sows, 3·9 (s.e. 0·04) kg/day) from day 100 of gestation until farrowing. Lactation food intake, changes in sow live weight and backfat thickness and piglet growth rates were then measured. Diet digestibility in early lactation was measured using a chromium III oxide marker in the food. There was no change in backfat thickness in late gestation in H sows (0·2 (s.e. 0·25) mm), whereas N sows lost backfat during this period (1·6 (s.e. 0·23) mm,P&lt;; 0·001). There was no difference in lactation food intake between the two groups (6·5 (s.e. 0·13) kg/day) and differences in backfat thickness at parturition were maintained through to weaning. H sows did not show increased incidence of agalactia compared with N sows. There was no difference in diet digestibility between the two treatment groups. Food intake level in late gestation did not affect piglet birth weights, growth rates or mortality. It is concluded that the main benefit of increasing sow food intake in late gestation was to reduce sow backfat loss during the reproductive cycle.

Factors associated with average pig weight at weaning on farms using early weaning

AbstractThe objective of this study was to investigate the effect of various factors on average pig weight at weaning on farms using early weaning. Farms were selected based on average weaning age and whether they recorded lactation food intake and litter weights at weaning. The database contained 9834 litter weights and 8903 food intake records. Average pig weight at weaning, litter size at weaning, weaning age, and average daily food intake during lactation (ADFl) were 4·9 (s.d. 1·0) kg, 9·3 (s.d. 1·6) pigs, 16·8 (s.d. 2·8) days, and 4·9 (s.d. 1·1) kg, respectively. Litter size, weaning age, parity, farrowing season, and ADFl groups influenced average pig weight at weaning (P &lt; 0·01). Three two-way interactions between parity and season, weaning age and farrowing season, and weaning age and ADFl groups were found fP &lt; 0·01). Average pig weights for litter sizes between six and 10 were higher than those between litter sizes one and four, and 11 and 22. Parity 1 sows produced lighter pig weights than any other parity group during any other season (P &lt; 0·01). Average weights of weaned pigs farrowed during the summer in all parities groups were lighter (P &lt; 0·01) than those during the autumn. Pig weights for weaning ages between 22 and 21 days during the summer tended to be lighter than those during the autumn. Pigs weaned between days 16 and 22 of age in the high ADFI group (&gt;5·6 kg) were heavier (P &lt; 0·01) than those in the low ADFl (&gt; 4·2 kg) group.

Additive effects of lactation and food restriction to increase hypothalamic neuropeptide Y mRNA in rats.

Neuropeptide Y (NPY) is the most powerful appetite stimulant known, and rates of synthesis and release in the hypothalamus correlate closely with nutritional status. Pregnancy and lactation provide an excellent model of physiological hyperphagia. In this study the authors measured food intake, plasma glucose, insulin and luteinizing hormone (LH) and hypothalamic NPY mRNA in rats during pregnancy and in early and late lactation. The effect of food restriction (to 80% of control) during lactation was also studied. Pregnancy resulted in a modest increase in daily food intake over non-lactating controls (controls: 15.6 +/- 0.6 g, pregnant: 19.8 +/- 1.1 g, P < 0.01). During lactation food intake increased dramatically to 355% of non-lactating levels by the 12th day. Insulin and glucose levels were unchanged in lactation, except in the food-restricted animals, when insulin levels were reduced to 49.5 +/- 18.4 pmol/l compared with 215 +/- 55 pmol/l (P < 0.01) in lactating, non-restricted animals, and glucose was reduced to 3.7 +/- 0.2 mmol/l compared with 5.1 +/- 0.2 mmol/l in non-restricted lactating animals. Hypothalamic NPY mRNA was unchanged in pregnancy, moderately increased after 5 days lactation (130 +/- 6.2% of control, P < 0.01) and increased further at 14 days lactation (179 +/- 14%, P < 0.001). The greatest changes occurred in the animals who were food-deprived during lactation, when hypothalamic NPY mRNA levels reached 324 +/- 44% (P < 0.001) of non-lactating levels. Increases in hypothalamic NPY synthesis may be partly responsible for the increase in food intake seen in lactation, but unlike in food deprivation, the increase is not related to circulating insulin, suggesting involvement of other regulatory factors.

Influence of food intake on plasma LH concentrations in multiparous sows

Nutrition may influence reproductive processes by a number of mechanisms including a direct effect on gonadotrophin secretion. The level of energy intake during lactation in multiparous sows may therefore have important consequences for luteinising hormone (LH) secretion after weaning. An experiment was carried out with 19 crossbred sows to investigate the effect of food intake in lactation and from weaning to day 6 post coitum on the pulsatile characteristics of LH on days 2 and 4 after weaning and on the preovulatory LH surge characteristics. During a 28 day lactation, sows were either offered 1.8 kg day −1 plus 0.55 kg per piglet suckled day −1 (H-high) of a commercial sow diet or 1.8 kg day −1 plus 0.25 kg per piglet suckled day −1 (L-low). After weaning, the sows from each lactation feeding regime were given either 1.5 kg day −1 (L-low) or 3.5 kg day −1 (H-high) until day 6 post weaning. The four treatment groups that comprised the 2 × 2 factorial design were thus HH, HL, LH and LL. Sows were mated at the appearance of oestrus. There were no significant differences between any of the treatment groups in episodic release of LH at either day 2 or day 4 post weaning. Also, there were no apparent effects of either food intake in lactation or between weaning and service on the timing and characteristics of the preovulatory surge of LH. The time intervals from the onset of the LH surge to peak LH concentrations for treatments LL, LH, HL and HH were 8.3 h, 8.7 h, 12.7 h and 11.3 h respectively and these differences approached significance ( P ⇒ 0.05). There were no significant correlations between liveweight loss during lactation and either the time to the onset of the LH surge or the time at which peak LH concentrations were observed.

Relationships between hypothalamic neuropeptide Y and food intake in the lactating rat.

NPYergic neurons in the hypothalamic arcuate nucleus (ARC) that project to the paraventricular nucleus (PVN) are postulated to regulate food intake and energy balance. This projection is overactive in lactation and is thought to drive hyperphagia in this condition. We have explored further the relationship between hypothalamic NPY and food intake in lactation and tested the hypothesis that hypoinsulinemia is the stimulus to NPY neuronal activity. Compared with nonlactating controls (n = 10), freely fed lactating rats (n = 9) showed significantly increased (p < 0.05) NPY levels in the ARC and medial preoptic area (MPO), but there was no significant increase in whole hypothalamic NPY mRNA levels. Lactating rats (n = 8) that were restricted to control rats' food intake for 3 days showed generally higher hypothalamic NPY levels, with significantly higher concentrations than controls (p < 0.05) in the ARC, MPO, PVN, and lateral hypothalamic area (LHA); NPY mRNA levels were also significantly increased (p < 0.05). Across all three experimental groups, there was a significant inverse correlation between plasma insulin concentration and hypothalamic NPY mRNA levels (r = -0.39, p < 0.01). We conclude that the ARC-PVN projection is overactive in lactation and that this is not a consequence of hyperphagia. Hypoinsulinemia may stimulate these neurons, as it is thought to do in other conditions of energy deficit.

Abstracts of Communications

Neuropeptide Y (NPY), a thirty-six amino acid peptide, is a potent centrally-acting appetite-stimulating agent which is believed to regulate eating behaviour and body weight (Williams et al. 1991). Lactation in rodents is associated with increased nutrient requirements which are met by extraordinary increases in food intake (Vernon, 1989). The aim of the present study was to investigate whether hyperphagia in lactating rats is associated with increased hypothalamic NPY levels, as in the case of other hyperphagic states such as starvation and diabetes. Twenty female Wistar rats, initially matched for age and weight, were studied. The experiment began when the lactating group (n 10) was on average at day 16 of lactation (range, 13-17). The lactating rats’ food intake was over 330% that of the controls (P 0.05). Four of the eight hypothalamic areas showed significantly increased NPY levels in the lactating rats compared with controls, namely: the arcuate nucleus-median eminence (+41%; P<0.001); the paraventricular nucleus (+35%; P<0.00l); the ventromedial nucleus (+66% ; P=0.003); the dorsomedial nucleus (+78%; P<0.00l). Other hypothalamic regions showed no differences between the two groups. Increased NPY levels in the arcuate nucleus (its principal hypothalamic site of synthesis) and in the paraventricular and dorsomedial nuclei (NPY-sensitive sites to which the arcuate nucleus projects) suggest increased activity of the NPY-ergic system in lactation. NPY may therefore mediate the markedly increased food intake in lactation.

The effect of food intake on prolificacy and plasma progesterone concentrations in multiparous sows

Eighty crossbred multiparous sows were allocated to one of 4 treatment groups which consisted of 2 levels of food intake in lactation and 2 levels of food intake in very early gestation. HH (High-High) and HL (High-Low) sows were offered 1.8 kg +0.55 kg per piglet suckled per day in lactation (26 days) wheras LH (Low-High) and LL (Low-Low) sows were given 1.8+0.25 kg per piglet per day. HH and LH sows in early pregnancy were offered 3.5 kg per day and HL and LL sows received 1.5 kg per day. For treatments HH,HL,LH and LL; the bodyweight changes from parturition to service were: −10.1, −14.6, −28.4 and −33.6 kg respectively, the P2 backfat changes over the same period were: −1.6, −2.2, − 4.0 and −3.8 mm respectively, the bodyweight changes in early pregnancy were: +9.5, +0.05, +13.7 and +0.01 kg respectively, the P2 changes were +2.1, +0.73, +1.65 and +0.81 mm.and, the mean litter sizes (total born) were: 10.8, 12.0, 11.1 and 12.1 piglets per litter. (NS) There were no significant differences in plasma progesterone concentrations in early pregnancy but there was a significant correlation ( P<0.01) between plasma progesterone concentration on day 20 post coitum and litter size born. ( r=+0.35) The results have demonstrated that different patterns of food intake in either lactation or in early pregnancy have no significant effect on plasma progesterone concentrations in early pregnancy or on the subsequent litter size in multiparous sows.

Reproductive performance, body weight and body condition of breeding sows with differing body fatness at parturition, differing nutrition during lactation, and differing litter size

ABSTRACTOne hundred and two Large White × Landrace Fl hybrid sows were allocated over four parities in a factorial design to two levels of target P2 backfat thickness at parturition (20 mm, F v. 12 mm, T), two levels of lactation feeding {ad libitum, H v. 3 kg/day, L), and two sizes of sucking litter (six v. 10). Sows attained 13 mm P2 when first mated at 126 kg live weight. Fatness (P2, mm) at weaning was significantly influenced by target fatness at parturition (14·2 v. 9·3), lactation feeding level (13·7 v. 10·0), and litter size (12·7 v. 11·0). Changes in backfat (P2, mm) during 28-day lactation were significantly influenced by target fatness at parturition (—5·0 v. —2·5), lactation feeding (-2 0 v. —5·4), and litter size (—2·9 v. -4·6). Sow live weight (kg) at weaning was significantly influenced by target fatness at parturition (211 v. 192), lactation feeding (218 v. 186), and litter size (208 v. 196). Changes in live weight (kg) during 28-day lactation were significantly influenced by target fatness at parturition (—26 v. — 12), lactation feeding (—5 v. —31), and litter size (—12 v. —25). With multiparous sows only, total food intake during 28-day lactation was negatively related to total food intake in pregnancy. Change in backfat (P2, mm) during 28-day lactation = -0·28 - 0·27 P2 at parturition + 0·04 lactation food intake — 0·50 litter size. Change in live weight (kg) during 28-day lactation = -3·8 — 0·15 live weight post partum + 0·36 lactation food intake — 3·3 litter size. Sows with target fat levels of 20 mm P2 at parturition had better food conversion efficiencies than sows with target fat levels of 12 mm. Target fatness at parturition, and especially lactation food intake, but not litter size, significantly influenced the interval (days) from weaning to oestrus in parity 1 (9·1 v. 14·2 and 7·8 v. 15·3, but 11·6 v. 11·5), while n i subsequent parities only litter size influenced the interval (days) from weaning to oestrus (6·0 v. 8·0). Birth weight (kg) of piglets was influenced only marginally by target fatness at parturition (1·4 v. 1·2) in parity 1, and not by the other factors, or in subsequent parities. Piglet growth rate was affected by both target fatness at parturition and litter size, but by lactation feeding level only in the last week of lactation. The relationship between fatness at weaning (mm) and the weaning to oestrus interval (days) for primiparous sows can be expressed as 26·6 — 1·28 P2. High level feeding in lactation imparted production and efficiency benefit in both primiparous and multiparous sows, while pregnancy feeding to a target of 20 mm rather than 12 mm at parturition was of benefit for primiparous sows.

Voluntary food intake of sows and gilts

AbstractThe lactating sow requires 5 to 7 kg food daily if it is to maintain body weight and condition in lactation but even on ad libitum intake sows fail to achieve the required food consumption and so lose both weight and tissue. The problem is most acute in primiparous sows and low lactation food intake is recognized as a major factor in post-weaning anoestrus and impaired reproductive performance. Studies of sows from the Moorepark herd are reported. Older animals, those with high suckling load and thin animals all tend to eat more with maximum daily intake occurring at 4 to 5 weeks of lactation. Although intake reduces at high environmental temperatures, this has been alleviated by wet feeding, offering a high energy-density diet or a high-protein diet. Other factors observed to influence voluntary food intake are breed, lighting pattern, dietary calcium and phosphorus levels.

Responses of lactating sows to food level

ABSTRACTEighty crossbred sows, following a standard feeding regime in pregnancy, received daily either 2·0, 3·5. 5·0 or 6·5 kg diet containing 130 g digestible crude protein, 8·0 g lysine and 13·1 MJ digestible energy per kg over a 28-day lactation to produce variation in body fatness and live weight. Sows on the highest level of feeding gained 13 kg and lost some 3 mm backfat between farrowing and weaning; corresponding changes on the lowest level of feeding were –31 kg and –9 mm backfat. Live weight of the litter at weaning was positively related to sow daily food allowance in lactation, but the major benefit of increasing lactation food allowance was in reducing the rate of maternal body weight and fatty tissue loss. These effects were described by the regression equations: maternal live-weight change in lactation (kg/day) = —1·7+0·34 lactation food intake (kg/day); maternal backfat change in lactation (mm LJSP2) = —0·40+0·05 lactation food intake fkg/day). Sows ingesting less food in lactation catabolized proportionately more body tissue to maintain milk yield and piglet growth, although they achieved this imperfectly, having lighter litters at weaning. Calculation of an overall net balance, taking into account the need subsequently to replenish tissues catabolized in lactation and ensuring efficient rebreeding of the sow, favoured a lactation feeding strategy towards ad libitum.

The effects of energy intake during pregnancy in doe rabbits on pup birth weight, milk output and maternal body composition change in the ensuing lactation

SUMMARYA study was made in rabbits on the effects of energy intake during pregnanoy on pup birth weight and survival, and on doe body composition and milk output in the ensuing lactation. In addition the experiment examined the effects of varying crudeprotein intakes during lactation on the rate of fat loss of does and the resultant energetic efficiency of milk production.Forty-seven multiparous cross-bred does were used. They were offered one of two diets in pregnancy, either diet HE (14·8 MJ digestible energy (DE)/kg D.M.) to appetite or diet LE (12·9 MJ DE/kg D.M.) at maintenance levels. After parturition seven does on each treatment were slaughtered and their body composition analysed (control groups). In lactation the remaining does were evenly allocated to receive either diet LE (195 g crude protein (CP)/kg D.M.) or diet HP (240 g CP/kg D.M.) to appetite. Litter sizes were standardized to six pups and litter growth rates were used as an indirect estimate of milk production. Does were then killed, at random, on day 9 or day 18 of lactation to give an estimate of changes in body composition as lactation progressed.Does offered diet HE during pregnancy had higher carcass fat levels at parturition than their counterparts offered diet LE (496 cf. 370 g/kg carcass D.M. respectively). Litter size was unaffected by dietary treatment during pregnancy but litter weights at birth were significantly greater in HE does (442 cf. 398 g respectively). Pup mortality at birth, however, was also much higher in these animals (28 cf. 9% respectively). Voluntary food intake in early lactation (day 1—9) was depressed by feeding diet HE during pregnanoy. Milk composition was affected by pregnancy diet, with does offered diet HE producing milk containing significantly higher fat levels (HE 123 g fat/kg milk cf. LE 105 g fat/kg milk).Doe carcass composition changes revealed that fat was usually mobilized in early lactation and gained as lactation progressed independent of dietary treatment. The protein content of the fat-free dry matter appeared to be relatively unaffected by the dietary treatments imposed. The data were used to derive an estimate of the partial efficiency of dietary energy utilization (fc) for milk output and maternal tissue gain. The line of best fit was described by the equation ER = 0·65 (±0·17) MEI-1–25, where ER = milk energy output + carcass energy change and MEI = metabolizable energy intake in MJ.

The effect of cholecystokinin, bombesin and calcitonin on food intake in virgin, lactating and postweaning female rats

During lactation food intake increases greatly without an accompanying large increase in body weight; therefore, this physiological state is an excellent example of non-obese hyperphagia. In the present study, we found that cholecystokinin (CCK-8) decreased food intake in lactating and virgin female rats. However, female rats were more resistant to the effect of CCK on eating following weaning of the pups. Bombesin (BB) suppressed food intake in virgin female rats and in lactating rats during early and mid lactation. Rats were resistant to its satiating effect during late lactation and during the postweaning period. Calcitonin potently suppressed food intake in virgin, lactating and postweaning rats. The present findings suggest that CCK and bombesin decrease food intake more effectively in virgin female rats and during earlier phases of lactation than during late lactation or postweaning.

Efficiency and performance of genetically high and low milk-producing British Friesian and Jersey cattle

ABSTRACTGenetic lines for high and low liquid milk production were established within the British Friesian and British Jersey breeds by random matings of experimental dams to the ‘best’ and ‘worst’ nationally available progeny-tested sires. Some Friesian dams could also be classified as either high or low for genetic potential for milk yield on the basis of previous, but less rigorously controlled, matings to high-or low-production sires. The dams and their high and low potential-production female progeny were reared indoors, and given a single complete pelleted diet ad libitum from weaning until leaving the experiment after their third calving. Height at withers and width at hooks were recorded monthly, cumulate food intake and body weight fortnightly and milk yield, fat and protein concentration weekly, throughout life in the experiment. Measures of lactation production, food intake and efficiency of conversion of food to milk product during the whole calving-to-calving interval were obtained. Yields were about 0-8 times national average yields. Differences between high and low genetic lines appeared similar for the two breeds. High potential-production progeny produced more liquid milk, fat and protein but at a lower fat and protein concentration than did low-potential progeny. High-potential progeny consumed more food from calving to calving and had higher food conversion efficiencies to liquid milk, fat and protein. The response in efficiency accompanying a given change in production was close to that predicted by phenotypic regression of efficiency on yield with a 0-75% increase in efficiency for every 1% increase in yield. The likelihood of smaller returns in efficiency at higher yields is discussed. High potential-production progeny lost more body weight than did low during lactation, suggesting a greater withdrawal of energy from body reserves. High-potential progeny were neither heavier nor taller but were marginally narrower at the hooks than were low-potential progeny, suggesting the possibility of increased calving difficulties as selection for increased yield continues.Friesians produced 50% more liquid milk, 13% more milk fat and 29% more milk protein and consumed 22% more food from calving to calving than did Jerseys. As a consequence Friesians were markedly more efficient at producing liquid milk (+23%) but essentially no more efficient at producing milk energy (+2%) than were Jerseys. In terms of both biological and commercial application of the results, any biases in the experiment probably operated against the Jersey relative to the Friesian.Predictions of food intake using accepted feeding standards underestimated observed total food intake during lactation by a factor of 0-8. Linear regression indicated underestimation of maintenance requirement as a likely explanation.

The effects of body condition at calving, food intake and performance in early lactation on blood composition of dairy cows given complete diets

ABSTRACTIn each of two trials, three groups of eight cows, with condition scores of 1-5 to 2, 2-5 to 3 and 3-5 to 4 at calving, were given a complete diet for the first 16 weeks of lactation. Food intake, milk yield, live weight and condition score were measured, and related to levels of plasma glucose and free fatty acids, serum insulin, prolactin and progesterone in weekly blood samples, in an attempt to explain differences in food intake.In both trials, levels of plasma free fatty acids were high after calving for all cows and declined rapidly until week 8, after which they were fairly constant. Glucose and insulin levels increased after calving, producing curves similar to that for dry-matter intake in the first 8 weeks of lactation. Prolactin levels fluctuated too markedly to provide useful information. Progesterone levels increased until week 7 and then fluctuated at 3-week intervals coincident with oestrus. Dry-matter intake was negatively correlated with free fatty acid levels and positively correlated with insulin in trial 1, and with glucose and progesterone in both trials.