Subspecies and body size allometry affect milk production and composition, and calf growth in red deer: comparison of Cervus elaphus hispanicus and Cervus elaphus scoticus

Physicochemical, Microbiological and Technological Properties of Red Deer (Cervus elaphus) Milk during Lactation

Simple Summary

Milk from red deer is richer in fat and proteins than that of cow or other ruminants. The semi-captive breeding of this species has traditionally focused on meat, velvet or hunting purposes, but recent studies suggested that the high level of nutrients, the promising content of bioactive peptides and the better digestibility than that of milk from other species could open innovative alternatives for the dairy industry. As for other non-commercial mammalian species that are gaining technological interest for the elaboration of dairy products, it is necessary to understand the aptitude and performance of milk from red deer to be used for the production of cheese, fermented milks or other products. Our study aims to assess some chemical, physical, microbiological and technological properties of red deer milk during a lactation period of 18 weeks. The results show that milk from this species is similar to that of other ruminant species whose milk is commercialized. In addition, our results indicate the best period to industrialize the milk during lactation. To the best of our knowledge, this is the first study to explore the benefits of using red deer milk with a technological approach.

Abstract

This study describes chemical, physical, microbiological and technological characteristics of red deer milk and the effect of lactation on these parameters in order to know their potential aptitude to elaborate dairy products. During 18 weeks, milk from five hinds was monitored for composition, bacteriology, somatic cell count (SCC), physical properties and rennet coagulation. Mean values (g/100 g) for fat, protein, lactose and dry matter were 10.4, 7.1, 4.3 and 24.2, respectively, and for urea, 265 mg/100 mL. Except for lactose, a significant increase in these components was observed (p < 0.01) as lactation progressed. The average values for bacteriology and SCC were 5.3 log cfu/mL and 4.7 log cells/mL, respectively. Regarding physical properties, conductivity (mean: 2.8 ms/cm), viscosity (3.1 Cp), coordinates L* (89.9) and a* (−3.1) and milk fat globule diameter (D_4,3: 6.1 µm) increased along with lactation while density (1.038 g/mL) decreased (p < 0.01). The pH (6.7), acidity (22.9° Dornic), coordinate b* (8.4) and ethanol stability (66.6% v/v) were stable during the study period. The stage of lactation also has a significant impact on milk coagulation properties and mean curd yield was 3.29 g/10 mL. These results suggest that red deer milk could be a potential innovative source of milk for the dairy industry.

Maternal effects shape offspring physiological condition but do not senesce in a wild mammal

In vertebrates, offspring survival often decreases with increasing maternal age. While many studies have reported a decline in fitness-related traits of offspring with increasing maternal age, the study of senescence in maternal effect through age-specific changes in offspring physiological condition is still at its infancy. We assessed the influence of maternal age and body mass on offspring physiological condition in two populations of roe deer (Capreolus capreolus) subjected to markedly different environmental conditions. We measured seven markers to index body condition and characterize the immune profile in 86 fawns which became recently independent of their known-aged mothers. We did not find striking effects of maternal age on offspring physiological condition measured at 8 months of age. This absence of evidence for senescence in maternal effects is likely due to the strong viability selection observed in the very first months of life in this species. Offspring physiological condition was, on the other hand, positively influenced by maternal body mass. Between-population differences in environmental conditions experienced by fawns also influenced their average body condition and immune phenotype. Fawns facing food limitation displayed lower values in some markers of body condition (body mass and haemoglobin levels) than those living in good quality habitat. They also allocated preferentially to humoral immunity, contrary to those living in good conditions, which allocated more to cellular response. These results shed a new light on the eco-physiological pathways mediating the relationship between mother's mass and offspring condition.

Maternal effects on reproduction in the precocial European hare (Lepus europaeus)

In female mammals, reproduction, and in particular lactation, is the energetically most exigent life-history phase. Reproduction is strongly controlled by body reserves and food availability, so females with better body condition or food supply are believed to have higher reproductive output. Additionally, the growth and mortality of young mammals depends on their postnatal development. Therefore, the degree of precociality affects energetic demands for both mothers and young. To study the reproductive performance of the precocial European hare (Lepus europaeus), we analysed relationships between six predictor variables describing maternal and environmental effects and nine response variables relating to reproduction from 217 captive females. We compared the data with those of precocial and altricial mammal species from an extensive literature search. For hares, we found: (1) Heavier females had heavier litters at birth. (2) In summer and spring, total litter mass was larger than in winter. (3) At the end of lactation, the litters of multiparous females were heavier than those of primiparous females. (4) Both older females and females giving birth for the first time had relatively high leveret mortality during lactation. Comparing our results with the literature for other mammals revealed that the body condition (i.e., body mass) of females before birth is predictive of reproductive parameters in both precocial and altricial species. In the precocial hare, female body condition is no longer predictive of reproductive parameters at the end of lactation, whereas in altricial species, female body condition remains predictive of reproduction (litter mass at the end of lactation, offspring mortality) until the end of lactation. We conclude that these effects are caused by precocial offspring feeding on solid food soon after birth and, thus, being less dependent on the mother's body condition during lactation than altricial offspring. In line with this, precociality might have evolved as a way of buffering offspring against maternal effects.

Offspring beg more toward larger females in a burying beetle

Offspring of many animals beg for food from parents. Begging is often costly, and offspring should seek to reduce such costs to maximize their returns on begging. Whenever multiple adults provide care for a joint brood, as in species where multiple females breed communally, offspring should beg toward the parent that provisions the most food. Here, we investigate whether larvae spend more time begging toward larger females in the burying beetle Nicrophorus vespilloides. Prior work on this species shows that larger females provision more food than smaller ones, suggesting that larvae would benefit by preferentially begging toward larger females. To test for such a preference, we provided experimental broods with a simultaneous choice between two dead females: a smaller and a larger one. Larvae spent more time begging toward larger females. We next examined the behavioral mechanism for why larvae begged more toward larger females. Larvae spent more time in close contact with larger females over smaller ones, whereas there was no evidence that larvae begged more when in close contact with larger females. Thus, larvae begged more toward the larger female simply as a consequence of spending more time close to larger females. Our findings have important implications for our understanding of parent–offspring communication by showing that offspring can choose between parents based on parental attributes, such as body size, reflecting how much food parents are likely to provision.

Short communication: Red deer (Cervus elaphus) colostrum during its transition to milk

We studied changes in chemical composition, somatic cell count, and immunoglobulin G (IgG) and M (IgM) content in red deer (Cervus elaphus) colostrum during the transition to milk at different times after parturition (<5 h, 24 h, 48 h, 2 wk, and 4 wk). The production level was higher at 2 and 4 wk of lactation than during the first day after parturition, with intermediate values at 48 h postpartum. Fat content did not vary during the study period. However, total protein and casein contents were particularly high in the initial 5 h after parturition, decreasing to approximately 50% after 24 h postpartum. Conversely, lactose concentration was low in the beginning (<5 h), increasing gradually throughout the study. Similarly, dry matter dropped during the first 24 h and then remained constant throughout the study. Urea content decreased during the study, showing a slight recovery at 4 wk. Somatic cell count was higher during the first hours after parturition and gradually decreased throughout the study period. The IgG content was higher before 5 h postpartum than at 24 h postpartum. After 5 h, the level of IgG decreased progressively until it reached 0.18 mg/mL at 4 wk of lactation. We observed a similar pattern for IgM content, but it decreased more quickly than IgG and was not detected after 2 wk. In the case of deer, milk should be considered transitional from 24 to 48 h after parturition, and samples collected after 2 wk can be considered mature milk.

Old and young female voices: effects of body weight, condition and social discomfort on the vocal aging in red deer hinds (Cervus elaphus)

In female terrestrial mammals, vocal aging has only been studied in humans and pandas. In cervids displaying convergent sex dimorphism of vocal apparatus with humans, vocal aging is only investigated in males. This cross-sectional study examined acoustic variables of nasal (closed-mouth) and oral (open-mouth) contact calls of 32 farmed Iberian red deer hinds (Cervus elaphus hispanicus) aged of 4-18 years and their relationships with caller´s age, weight, social discomfort score (bites of other hinds on hind pelt) and body condition score (fat reserves). Decrease of fundamental frequency was associated with age in both oral and nasal calls, but more prominently in the nasal calls. An increase in call duration, peak frequency and power quartiles was associated with a higher degree of bites due to social aggression. Weight and body condition weakly influenced acoustic traits. We discuss that vocal aging of hinds parallels that of vocal aging in human females.

The power of oral and nasal calls to discriminate individual mothers and offspring in red deer, Cervus elaphus

BACKGROUND

In most species, acoustical cues are crucial for mother-offspring recognition. Studies of a few species of ungulates showed that potential for individual recognition may differ between nasal and oral contact calls.

RESULTS

Vocalizations of 28 hinds and 31 calves of farmed Iberian red deer (Cervus elaphus hispanicus) were examined with discriminant function analyses (DFA) to determine whether acoustic structure of their oral and nasal contact calls encodes information about the caller's identity. Contact calls were elicited by brief separation of individually identified animals by a distance over 10 m or by a bar fence. Both oral and nasal calls of both hinds and calves showed high potential to discriminate individuals. In hinds, individuality was significantly higher in the oral than in the nasal calls, whereas in calves, individuality was equally well expressed in both oral and nasal calls. For calves, the maximum fundamental frequency was higher and the duration was longer in oral calls than in nasal calls. For hinds, the maximum fundamental frequency and the duration were indistinguishable between oral and nasal calls. Compared to the pooled sample of oral and nasal calls, separate oral or nasal call samples provided better classifying accuracy to individual in either hinds or calves. Nevertheless, in both hinds and calves, even in the pooled sample of oral and nasal calls, the degree of individual identity was 2-3 times greater than expected by chance. For hinds that provided calls in both years, cross-validation of calls collected in 2012 with discriminant functions created with calls from 2011 showed a strong decrease of classifying accuracy to individual.

CONCLUSIONS

These results suggest different potentials of nasal and oral calls to allow the discrimination of individuals among hinds, but not among red deer calves. The high potential of individual recognition even with the pooled sample of oral and nasal calls allows mother and young to remember only one set of acoustic variables for mutual vocal recognition. Poor between-year stability of individual characteristics of hind oral and nasal calls would require updating keys to individual recognition each calving season.

Milk composition during lactation suggests a mechanism for male biased allocation of maternal resources in the tammar wallaby (Macropus eugenii)

Recent research has found empirical evidence in support of the Trivers-Willard Hypothesis that offspring sex allocation is correlated with maternal investment. Tammar wallabies birthing sons have higher investment ability; however a mechanism for sex specific differential allocation of maternal resources in wallabies remains elusive. In metatherians the majority of maternal investment is during lactation. To examine if differential allocation occurs during lactation, we measured total milk protein, lipid and carbohydrates, from mothers with male and female pouch young, during phase 2B (100–215 days post partum) and phase 3 (215–360 days post partum) of lactation. Mothers of sons allocated significantly higher levels of protein than mothers of daughters during phase 2B of lactation, however no sex specific difference in maternal allocation was found for lipids, carbohydrates, or any milk component during phase 3 of lactation. We were unable to measure milk production to establish any differences in the amount of milk allocated. However, with the production of more milk comes a dilution effect on milk components. Given that we find no apparent dilution of milk components may suggest equality in milk production. Offspring body weight at 14 months of age was related to protein allocation during phase 2B of lactation, providing a maternal mechanism for differential allocation with fitness consequences. We believe collection of earlier phase 2A (0–100 days post partum) milk may yield important results given that differential investment in metatherians may be most apparent early in lactation, prior to any significant maternal investment, when a decision on termination of investment can be made with very little energetic loss to the mother. Interestingly, small mothers did not birth sons and better maternal condition was associated with raising sons. These data are in support of TWH and demonstrate a potential mechanism through which condition dependent and sex specific maternal investment may occur.

Is mother condition related to offspring condition in migratory caribou (Rangifer tarandus) at calving and weaning?

Maternal characteristics can affect offspring traits, yet they are seldom included when considering density dependence of juvenile traits and population dynamics. We quantified the influence of population size and maternal traits on body condition of migratory caribou ( Rangifer tarandus (L., 1758)) calves at birth and weaning. We contrasted female–calf pairs of the Rivière-George (RG) herd, which has recently declined to low population size, with pairs of the much larger Rivière-aux-Feuilles (RAF) herd. Calves of the RAF herd were lighter, smaller, and leaner than calves of the RG herd at both birth and weaning. Differences between herds, however, were much greater at weaning than at calving, suggesting a combined effect of herd size and summer range conditions on calf growth. Maternal mass was positively related to calf body condition during both periods. The positive influence of maternal mass on calf body condition was greater for RAF than RG calves at birth, but it was similar for the two herds at weaning. Our results show that the negative effect of population size on calf body condition can be modulated by maternal mass at calving, and that the positive effect of maternal mass is greater at weaning.

Effects of ad libitum mineral consumption in Iberian red deer hinds and calves

Minerals are essential nutrients for ungulates because they cannot be synthesised. Lactation is the most mineral-demanding stage for hinds, whereas for calves both the pre- and post-weaning growth periods are important for bone formation, among other processes. Because both physiological effort and hot Mediterranean climate may increase mineral needs even in a situation under an ad libitum high plane of nutrition, we examined the effects of free-choice, single-mineral consumption in red deer hinds and their calves during lactation, and in the calves, from 18 to 56 weeks after lactation. Group M had permanent access to minerals, the control group had no access, whereas the LM and PLM groups of calves had access to minerals only during lactation or after lactation, respectively. Hinds with or without mineral supplements during lactation did not show differences in weight or body condition, neither did female calves of any group during or after lactation. However, after controlling the effect of year, LM male calves achieved greater weight gains during the post-lactation experiment, whereas the PLM and M groups showed negative results in weight at the end of the post-lactation experiment and age of antler growth initiation, respectively. The LM group also achieved higher scores in all the studied first antler variables (length, weight, burr perimeter, and perimeter in the middle of the antler) after controlling the effects of weight and year. The results thus suggest that, under ad libitum access to high-quality food, mineral supplementation is only positive during lactation. However, it cannot be ruled out that minerals may be beneficial in other stages in free-ranging deer.

Direct versus indirect effects of social rank, maternal weight, body condition and age on milk production in Iberian red deer ( Cervus elaphus hispanicus)

Social rank in cervids and other mammals is not entirely predicted by body weight, but in most cases influences access to food directly. Milk provisioning depends on maternal weight and on daily food intake. Usually, body weight, body condition, age and social rank are inter-correlated making it very difficult to discern the relative importance of each variable to milk production. This study used path analysis to assess direct versus indirect effects of these variables on milk production of 62 Iberian red deer hinds (Cervus elaphus hispanicus). Once the known direct effects of body weight and body condition were set as fixed, hind age and social rank did not affect milk production directly. In contrast, they exerted an indirect influence through the correlation both with hind body weight and body condition. Body weight exerted an effect on milk production nearly twice as great as that of body condition. This study shows, for the first time in a wild mammal, the relative importance of social rank, body weight, body condition and age in affecting milk production ability.

Age-related body weight constraints on prenatal and milk provisioning in Iberian red deer (Cervus elaphus hispanicus) affect allocation of maternal resources

Maternal phenotypic characteristics can influence key life history variables of their offspring through maternal effects. In this study, we examined how body size constraints on maternal weight in yearling and subadult compared to adult hinds (age class effects) affected prenatal (calf birth weight, calf to hind weight ratio) and postnatal (milk) provisioning of Iberian red deer calves. Age correlated with all prenatal and postnatal investment traits except calf gains, although correlations were weaker than those with maternal weight. Once the effect of linear increase in weight with age was removed from models, yearlings showed additional reductions in calf birth weight, calf gains, and milk provisioning. The low-calf birth weight might increase the risk of calf mortality during lactation, as this occurs primarily during the first day of life and is strongly related to birth weight. Yearlings showed a greater prenatal allocation of resources in terms of greater calf to hind weight ratio probably as an extra effort by yearling mothers to balance calf neonatal mortality. It might compensate young mothers to produce low-quality calves while still growing rather than waiting for the uncertain possibility of surviving to the next reproductive season.

Compensatory extension of gestation length with advance of conception in red deer (Cervus elaphus)

Calving date in many mammals is matched to the time of greatest food availability. Out of season calving results in heavy penalties in terms of own and offspring survival or body condition. This study examined whether gestation length is affected by advancing fertilisation. Thirty-six red deer hinds (of the Iberian and Scottish subspecies) were subjected to a synchronisation treatment of oestrus, ovulation, and artificial insemination on three dates, with remaining non-pregnant females mated with an intact male in a last group. Gestation was longer the more the fertilisation was advanced; gestation lasted 241.5+/-1.3 days (d) in the first group, 237.4+/-1.2 d in the second, 235.1+/-1.3 d in the third, and 231.2+/-1.6 d in the last. Mean gestation lasted 234.2+/-0.7 d. Hinds gained less weight during gestation the more the fertilisation was advanced. The difference was due at least in part to net body weight of the hind after calving compared to that at mating, and calves did not differ in birth weight. As early born calves suffer greater mortality in the field, this enlargening of gestation might be a compensatory response of the hinds to match calving with food availability. Under natural conditions, similar small modifications of gestation length may help hinds to overcome short-term adverse conditions for calving. Because calf mortality is correlated with birth weight, hinds may have kept calf birth weight constant at the expense of greater body weight loss.

Seasonal and Lactational Changes in Mineral Composition of Milk from Iberian Red Deer (Cervus elaphus hispanicus)

Milk minerals are important for calf growth, and they have other roles as well, such as immune regulation. This 2-yr study examined content of Ca, P, Mg, Na, K, Fe, and Zn in milk of 54 Iberian red deer hinds through 18 wk of lactation. Mean mineral composition of fresh milk was ash = 1.168 +/- 0.007%, Ca = 2,330 +/- 20 mg/kg, P = 640 +/- 10 mg/kg, K = 1,100 +/- 10 mg/kg, Na = 385 +/- 3 mg/kg, Mg = 138 +/- 1 mg/kg, Zn = 12.5 +/- 0.2 mg/kg, and Fe = 0.65 +/- 0.03 mg/kg. All minerals except Mg varied by week of lactation, but variation was usually <10% except for Fe (83% variation) and Zn (30% variation); both of those minerals increased as lactation proceeded. Increased concentrations of Fe and Zn in later lactation compensated for the reduction in milk production in mid and late lactation such that daily production was less variable for Fe (55% variation) or Zn (79% variation) than for other minerals (118 to 135% variation). Potassium content of milk decreased across time, but that effect occurred primarily during the last few weeks of lactation. Calving later vs. early in the calving season had variable effects on concentrations of different minerals: P, Mg, and K concentrations were not affected; Ca, Mg, and Na were all lower in milk from later calving hinds; and both Fe and Zn had higher concentrations in milk from hinds that calved later in the season. Lactating hinds seem to maintain a more stable daily yield of the microminerals Fe and Zn in milk compared with more variable concentrations of macrominerals as lactation progresses. Because of the essential role of Fe and Zn in immune function, a more stable supply of those minerals might be important to the health of growing red deer calves.

Effects of Birth Date and Order in Lactation Performance of Iberian Red Deer (Cervus elaphus hispanicus)

This study discriminated between 2 effects (birth date and presence of older calves) assessed jointly in previous studies. Birth date delay produced similar effects to those reported previously: reduced milk and milk nutrient production in late-calving hinds, concentration of milk, substitution of protein by fat, greater body weight losses of dams (hinds), and reduced calf growth. Hinds in a group consisting of early- and late-born calves produced more milk, and calves grew more than their isolated counterparts. Evidence exists for consequences of foster suckling by early-born calves in mixed groups of early- and late-born calves at the end of the standard birth period, because these calves grew more than predicted by the milk production of their dams. In contrast, no detrimental effect was found in late-born calves of this group. Lack of differences might be due to the excess of hind milk production during the first 5 wk of lactation previously recorded in other experiments.