Summer Lactation Research Articles

Robust Responses of Female Caribou to Changes in Food Supply.

AbstractUngulates can respond to changes in food supply by altering foraging behavior, digestive function, and metabolism. A multifaceted response to an environmental change is considered robust. Short seasons of plant growth make herbivores sensitive to changes in food supply because maintenance and production must be accomplished in less time with fewer options in a more fragile response. Caribou live at high latitudes where short summers constrain their response to changes in food supply. We measured the ability of female caribou to resist and tolerate changes in the quality and quantity of their food supply during winter and summer. Caribou resisted changes in food abundance and quality by changing food intake and physical activity with changes in daily temperature within each season. Peak food intake rose by 134% from winter pregnancy to summer lactation (98 vs. 229 g kg-0.75 d-1), as digestible requirements to maintain the body increased by 85% for energy (1,164 vs. 2,155 kJ kg-0.75 d-1) and by 266% for N (0.79 vs. 2.89 g N kg-0.75 d-1). Caribou required a diet with a digestible content of 12 kJ g-1 and 0.8% N in pregnancy, 18 kJ g-1 and 1.9% N in early lactation, and 11 kJ g-1 and 1.2% N in late lactation, which corresponds with the phenology of the wild diet. Female caribou tolerated restriction of ad lib. food intake to 58% of their energy requirement (680 vs. 1,164 kJ kg-0.75 d-1) during winter pregnancy and to 84% of their energy requirement (1,814 vs. 2,155 kJ kg-0.75 d-1) during summer lactation without a change in stress level, as indicated by fecal corticosterone concentration. Conversely, caribou can respond to increased availability of food with a spare capacity to process digestible energy and N at 123% (2,642 vs. 2,155 kJ kg-0.75 d-1) and 145% (4.20 vs. 2.89 g N kg-0.75 d-1) of those respective requirements during lactation. Robust responses to changes in food supply allow caribou to sustain reproduction, which would buffer demographic response. However, herds may decline when thresholds of behavioral resistance and physiological tolerance are frequently exceeded. Therefore, the challenge for managing declining populations of caribou and other robust species is to identify declines in robustness before their response becomes fragile.

Biochemical composition of sheep milk of different breeds during the summer lactation period.

The article presents the results of the study of biochemical composition of sheep milk in the summer lactation period for 4 sheep breeds. According to research results, 18 amino acids were found in sheep milk. During the summer lactation period, the amount of polyunsaturated fatty acids, both the Ordabasy breed and the South Kazakh merino exhibit higher levels (ranging from 6349 to 6989) compared to the Kazakh fine-fleeced and meat Merino breeds (ranging from 5835 to 5500). When analyzing sheep milk, a tendency towards a higher content of vitamin A (59.91 μg/100 g) and B6 (73.0 μg/100 g) was noted. The highest calcium content was found in the milk of the Kazakh fine-fleeced sheep, while the lowest was observed in the South Kazakh merino breed. Better milk productivity, along with increased fat and protein content, has been noted in sheep of the Ordabasy and South Kazakh merino breeds.

33. Effects of betaine supplementation in summer lactation and weaning-to-remating interval on subsequent reproductive performance of sows

33. Effects of betaine supplementation in summer lactation and weaning-to-remating interval on subsequent reproductive performance of sows

Characteristics of lactation of cows of Red steppe and Simmental breeds under the economic conditions of Yakutia

In order to increase the gross milk production and increase the number of breeding cattle in the farms in the Republic of Sakha (Yakutia), dairy cattle of Red steppe breed have been imported. Getting into the new climatic and economic conditions of housing and feeding, the body of imported cattle undergoes deep physiological and biochemical changes, goes through the process of adaptation. The purpose of the work was to study the nature of lactation of cows of Red steppe and local Simmental breeds under the economic conditions in Central Yakutia. The intensity and uniformity of lactation during the year has an important role in determining the value of dairy productivity of cows. The ability of cows to give evenly or sharply decreasing milk yields during lactation tends to be inherited, so it should be taken into account in breeding work. The lactation curve provides additional information about the potential of dairy productivity of cows and the impact of feeding, housing and operation conditions on the lactation process. It has been found that the winter ration of lactating cows contained 9,4 EFU and 1139 g of digestible protein, which amounted to 89,9 and 107,0 % of the feeding norm. In the structure of the ration, the proportion of bulky feed occupied 36 %, succulent feed 24 % and concentrated feed 40 %. The sugar-protein ratio was 0,43, which indicated a deficiency in the carbohydrate ration. It was found that under the same conditions of feeding and housing, the cows under study showed a two-vertex level of the lactation curve. In cows of both breeds the peak of the lactation curve occurred during the summer lactation period with the release of animals for summer pasture maintenance. Then, in cows of both breeds the lactation curve began to gradually decrease. Valuable are those animals whose leveled type of lactation and milk yield are housed at a fairly constant level. The indicator of lactation usefulness in cows of Red steppe breed was equal to 68,24 %, in Simmental breed 64,24 %.

Compensatory feeding during early gestation for sows with a high weight loss after a summer lactation increased piglet birth weight but reduced litter size.

Sows mated in summer produce a greater proportion of born-light piglets (<1.1 kg) which contributes to increased carcass fatness in the progeny population. The reasons for the low birth weight of these piglets remain unclear, and there have been few successful mitigation strategies identified. We hypothesized that: 1) the low birth weight of progeny born to sows mated in summer may be associated with weight loss during the previous summer lactation; and 2) increasing early gestation feed allowance for the sows with high lactational weight loss in summer can help weight recovery and improve progeny birth weight. Sows were classified as having either low (av. 1%) or high (av. 7%) lactational weight loss in their summer lactation. All the sows with low lactational weight loss (LLStd) and half of the sows with high lactational weight loss received a standard gestation feeding regime (HLStd) (2.6 kg/d; day 0-30 gestation), whereas the rest of the sows with high lactational weight loss received a compensatory feed allowance (HLComp) (3.5 kg/d; day 0-30 gestation). A comparison of LLStd (n = 75) versus HLStd sows (n = 78) showed that this magnitude of weight loss over summer lactation did not affect the average piglet or litter birth weight, but such results may be influenced by the higher litter size (P = 0.030) observed in LLStd sows. A comparison of HLStd versus HLComp (n = 81) sows showed that the compensatory feeding increased (P = 0.021) weight gain of gestating sows by 6 kg, increased (P = 0.009) average piglet birth weight by 0.12 kg, tended to reduce (P = 0.054) the percentage of born-light piglets from 23.5% to 17.1% but reduced the litter size by 1.4 (P = 0.014). A subgroup of progeny stratified as born-light (0.8-1.1 kg) or -normal (1.3-1.7 kg) from each sow treatment were monitored for growth performance from weaning until 100 kg weight. The growth performance and carcass backfat of progeny were not affected by sow treatments. Born-light progeny had lower feed intake, lower growth rate, higher G:F, and higher carcass backfat than born-normal progeny (all P < 0.05). In summary, compensatory feeding from day 0 to 30 gestation in the sows with high weight loss during summer lactation reduced the percentage of born-light progeny at the cost of a lower litter size, which should improve growth rate and carcass leanness in the progeny population born to sows with high lactational weight loss.

The Count of Lactic Acid Bacteria in White Cheese

The aim of the study was to investigate the effect of pH and the temperature on the lactic acid bacteria during 45 day cheese making time because they have the most important effect in taste and aroma as final product. The determination of the presence of lactic acid bacteria counted in milk and cheese is important because they have the most important effect in taste and aroma as final product. Raw material for white soft cheese production was bulk cow milk (summer lactation) from the terrain of the whole Pcinja region in Serbia. The samples for microbial and physical-chemical testing were monitored from: raw milk, milk before making cheese, whey, coagulate before production, after self pressure and pressure, cheese after moulding and dry salting and cheese after the 1 st , 10 th , 20 th , 30 th and 45 th day of brine. During the cheese making, the number of lactic acid bacteriaa in the milk prepared for making cheese was decreasing in comparison to their number in the raw milk, which proves that the total number of microorganisms is less after pasteurization. During the further production, the number of lactic acid bacteria came up the maximum in the phase of pressing or self-pressing, forming end salting. The number of lactic acid bacteria decrease during the cheese ripening in the pickle. The biggest fails of number cover with the biggest fail of pH. At the end of salting, the number of lactic acid bacteria moves from 2.4x10 5 – 5.8x10 5 /g of cheese.

Commercial sheep flocks--fatty acid and fat-soluble antioxidant composition of milk and cheese related to changes in feeding management throughout lactation.

Fatty acids (FAs), tocopherols and retinoids were analysed in raw milk and cheese from six commercial sheep flocks monitored from early lactation in winter to late lactation in summer. In winter, animals received concentrate and forage indoors; in early spring, animals grazed part-time on cultivated or natural valley grasslands; and from mid spring on, animals were kept outdoors constantly on mountain natural pastures. Mountain grazing in late lactation significantly increased the amount of healthy desirable unsaturated FAs such as C18:1t11 (VA), C18:2c9t11 (RA), C18:2t11c13, C18:3c9c12c15 (ALA) and C20:5c5c8c11c14c17 (EPA), and those of α-tocopherol and α-tocotrienol of milk and cheese. Stepwise discriminant analysis was applied to classify cheese samples according to seasonal feeding management. The multivariate approach was able to discriminate beyond doubt mountain cheeses from those of indoor feeding and part-time valley grazing.

Prescribed fire affects female white-tailed deer habitat use during summer lactation

Prescribed fire commonly is used to manage habitat for white-tailed deer (Odocoileus virginianus). Although the effects of fire on forage availability for deer have been studied, how female deer use burned areas is not well known, particularly as it relates to fire season and the years-since-fire. We used GPS tracking data from 16 adult female white-tailed deer to assess the effects of fire season and years-since-fire on habitat use during summer lactation. Females selected unburned drainages and older (>1yr-since-fire) burned areas, and avoided recently burned areas. Individuals with a greater percentage of their summer core area burned expanded the size of their summer home range but did not change summer core area size. Furthermore, summer core area site fidelity (i.e., % overlap between 2011 and 2012 core areas) decreased as the percentage of the 2011 summer core area burned in 2012 increased. Female deer increased selection of burned areas as years-since-fire increased, likely because there was a temporary loss of cover immediately following fire with plants slowly regenerating the subsequent growing seasons. Likewise, to avoid areas depleted of cover, females shifted their core areas away from recent burns when possible but increased their core area size when burned areas were unavoidable (i.e., a large portion of their home range was burned). Burning large contiguous areas may initially have a negative effect on female deer during lactation because of the depletion of cover.

Short communication: Jenny milk production and qualitative characteristics

The aim of this research was to study the influence of lactation stage and foaling season on some qualitative aspects of milk in South Italian jenny rearing. Milk samples were collected monthly from 23 jennies, that foaled in 2 different periods: spring and summer. On milk, the following parameters were measured: pH and titratable acidity; protein, fat, lactose, dry matter, and ash contents; and somatic cell count. Analysis of variance showed the effect of foaling season and of lactation stage. Milk production was highest in summer at 30 d and 60 d (1.58 and 1.78L, respectively), and in spring at 120 d (1.25L). The total protein content was highest in summer lactation at 30 d and 90 d (14.8 and 13.9g/L). Lactose, dry matter, and ash contents (g/L) were highest in summer lactation at 30 d (54.0, 78.1, and 5.0 respectively). Jenny milk was shown to be poor in protein and fat and rich in lactose. Producing jenny milk could be an interesting, profitable, and alternative activity for farmers, mainly in southern marginal areas.

Lying patterns of high producing healthy dairy cows after calving in commercial herds as affected by age, environmental conditions and production

An animal expresses its physiological and well-being status by its behaviour. Changes in behaviour can be associated with health, production or well-being problems and therefore with the profitability of the farm. The objectives of the present study were to analyse lying patterns of healthy cows, collected with a commercial behaviour sensor, in early lactation in relation to environmental conditions, age of the cow and production performance. In future, these results may be used as a ‘baseline’ for detection of alterations in behaviour that indicate health problems. The study involved 210 healthy multiparous Israeli Holstein cows in three commercial dairy farms. Only healthy cows during the first 28 days after calving were included in this study. Data were analysed in relation to calving season, age of cows and correlation between milk production and lying time. The results show that lying time increased significantly with age and is significantly ( P < 0.05) higher in winter than in summer (summer lactation 2: 491 ± 17 min/day (mean ± SD), summer lactation 3 and more: 520 ± 25 min/day, winter lactation 2: 531 ± 25 min/day, winter lactation 3 and more: 579 ± 38 min/day). The proportion of positively and negatively milk production and lying time correlated cows is affected by calving season. This study indicates that behaviour variables in early lactation are affected by calving season, lactation number and type of correlation between milk production and lying time.

Anti‐predator behaviour, space use and habitat selection in female roe deer during the fawning season in a wolf area

AbstractThis study investigated the anti‐predator strategies adopted by 19 radio‐collared female roe deer during the fawning season by monitoring their spatial behaviour and habitat selection by means of radio‐tracking. The study was carried out in a forest area of the Apennine Mountains (central Italy), where wolves are natural predators of roe deer and in summer fawns are more frequently predated than adult roe deer. The presence of fawns was monitored by means of direct observations. Roe deer fawns are known to adopt the hiding strategy during the lactation period, when they lie concealed for long periods waiting for their mothers' milk. As a consequence of this, the home‐range sizes of mothers were significantly smaller than those of non‐mothers during the summer lactation only. In contrast, no significant difference was found in spring, when fawns were absent, or autumn, when they were already weaned. In order to increase the success of the hiding strategy adopted by their fawns against wolf predation, mothers selected denser habitats (deciduous coppice forests) that provided denser undergrowth vegetation and limited visibility. In doing so, mothers traded open areas for forests throughout the fawning season. Indeed, mothers made significant habitat selection throughout the monitored period, and this was marked after the birth of fawns. In contrast, non‐mothers generally used habitat types according to their availability. During lactation, the correlation between habitat use by mothers and habitat visibility (assessed using the form of a standard‐sized roe deer) was inversely significant. These results taken together highlight the importance of anti‐predator strategies adopted by roe deer mothers during the critical phase for fawn survival.

Determinants of Survival and Fecundity Through a Population Bottleneck in Pronghorn (Antilocapra americana)

The long-term viability of small, isolated populations has been questioned in light of stochasticity and bottlenecks. Following a drought in northwestern Montana in 2003, the pronghorn (Antilocapra americana )o f the National Bison Range experienced a demographic bottleneck. We used information theoretic approaches to examine the influence of sex, age, genetic variation, summer lactation, mate-search effort by females, and mating effort by males on subsequent winter survival and spring fecundity. Survival of males was influenced by age, whereas survival of females was influenced by prior energy expenditure and genetic variation, implicating inbreeding depression as the mechanism. Fecundity of females also was influenced by prior energy expenditure and genetic variation, with heterosis as the apparent mechanism. Our results agree with those of other studies that have emphasized the need to maintain genetic variation and limit inbreeding in small, isolated populations, and to account for stochasticity in population viability assessments and long-term management planning.

Inestabilidad de la leche asociada a componentes lácteos y estacionalidad en vacas a pastoreo

El objetivo de este trabajo fue caracterizar rebaños lecheros que presentaban muestras de leche positivas a la prueba de alcohol sin estar ácidas, y compararlos con predios negativos a esta prueba, considerándose el efecto de la estacionalidad. Se estudiaron cuatro rebaños (tres positivos a la prueba de alcohol y uno negativo). En dos años, se muestreó leche durante tres meses en lactancias de invierno (época 1) y tres meses en lactancias de verano (época 2). En la dieta, se realizó análisis proximal relativo a EM, Ca, P, Mg y K. En leche, se determinó proteína, lactosa, Ca, P, Mg, K, pH, prueba de alcohol, acidez titulable y actividad proteásica. En casos negativos a la prueba de alcohol, se observó alta correlación entre proteína cruda láctea, proteína cruda en alimento, fósforo lácteo y lactosa. Los predios positivos a la prueba de alcohol se correlacionaron fuertemente con la menor concentración de materia seca y el alto contenido de fibra cruda, además presentaron menor concentración de proteína láctea. Ello indicaría que existió un efecto del manejo alimentario sobre la inestabilidad de la leche. Las lactancias desarrolladas durante la sequía estival sufren de un stress alimenticio, por lo cual podrían presentar inestabilidad láctea.

The Effect of Prepartum Diet on Nitrogen and Major Mineral Balance of Dairy Cows during Parturition in Summer

Proper nutritional management during the dry period is required to prevent metabolic disorders during the time of parturition and for potential increase milk yield during early lactation, especially under the heat of summer. The effect of prepartum diets on partitioning of nitrogen (N), calcium (Ca), phosphorus (P), magnesium (Mg) and potassium (K) during dry period and early lactation in summer was investigated. Nine cows were assigned to two groups and fed either control (group C: four cows) or high concentrate (group H: five cows) diets to meet 110% of their requirements before parturition. The proportion of concentrate in control diet was 35%, and that in the high concentrate diet was 45%. After parturition, all cows were fed the same diets ad libitum during lactation. Balance trials were conducted at 9, 8 and 7 days before parturition and at 12, 13 and 14 days after parturition. Before parturition, dry matter intake (DMI), DM and NFE digestibility in group C tended to be lower than those in group H. The retention of N (p<0.01) and P (p<0.05) in group C during the dry period was significantly lower than those in group H. The retention of Mg in group C during the dry period tended to be lower than in group H. The concentration of plasma NEFA in group C tended to be higher than in group H during dry period. The prepartum diet did not have an apparent effect on DMI and milk yield at 2 weeks after parturition and N, C a , P, Mg and K balance after parturition.

The ratio between dietary rumen degradable organic matter and crude protein may affect milk yield and composition in dairy sheep

The current ruminant protein systems aim at synchronizing the provision of rumen degradable organic matter (RDOM) and degradable crude protein (RDCP) but no specific information on their optimal ratio for dairy sheep is available. We studied the effect of the ratio of RDOM to RDCP on milk yield and composition, during a summer lactation, in 34 confined Assaf sheep managed under farm condition. Individual feed intake was assessed by using PEG (MW 4000) as external marker of fecal output, and indigestible INDF as internal marker of digestibility. Four total mixed rations contained two levels of RDCP (108 and 117 g/kg DM) and two levels of RDOM (510 and 570 g/kg DM). This resulted in one diet featuring high (5.3), one diet featuring medium (4.8) ratio, and two diets featuring low (4.5) ratio of RDOM to RDCP. Individual DM intake, digestibility, and the daily yields of milk components were not affected by RDOM, RDCP or RDOM/RDCP. High RDOM/RDCP tended ( P < 0.10) to be associated with higher milk yield, and lower ( P < 0.05) CP content. The casein/CP ratio and urea-N in milk were lowest when both dietary RDCP and RDOM were low, whereas lactose was highest ( P < 0.05) when both RDOM and RDCP concentrations were high. Our data suggest that RDOM and RDCP interact on milk composition in a way that is not fully encompassed by the RDOM/RDCP ratio and that the use of this ratio to formulate diets for pre-determined milk composition is not warranted.

Use of Lotus corniculatus containing condensed tannins to increase lamb and wool production under commercial dryland farming conditions without the use of anthelmintics

Two grazing experiments were conducted for 12 and 13 weeks, respectively, over the spring periods of 2000 and 2001 at Massey University's Riverside farm in the Wairarapa (New Zealand) to compare effects of grazing Lotus corniculatus (birdsfoot trefoil; cv. Grasslands Goldie) or perennial ryegrass ( Lolium perenne)/white clover ( Trifolium repens) dominant pasture during lactation on ewe and lamb live weight (LW), wool production, faecal nematode egg counts (FEC) and dag score. Ewes and their lambs (mainly twins) were rotationally grazed on lotus or pasture ( n = 50) without any anthelminitc treatment at a herbage allowance of 6.5 and 8.0 kg green DM/ewe/days for Experiments 1 and 2, respectively. Total condensed tannins (CT) concentration in the diet selected was 24 to 27 g CT/kg DM for lotus and 1.4 to 1.5 g CT/kg DM for pasture. In vitro organic matter digestibility and metabolisable energy (ME) concentration were higher for lotus than for pasture in both experiments, whilst the concentrations of neutral detergent fibre (NDF) was lower in lotus than in pasture. The LW gain, weaning LW and wool production were consistently higher ( P < 0.001) for lambs grazing lotus, in both Experiment 1 (258 versus 189 g/days; 36.1 versus 30.1 and 1.17 versus 0.98 kg) and in Experiment 2 (247 versus 162 g/days; 31.8 versus 24.1 and 1.17 versus 0.81 kg), respectively. Ewe and lamb dag score were strongly and positively correlated with dag weight ( P < 0.001), and generally increased with time in sheep grazing pasture; while grazing on lotus consistently reduced dag score. FEC in ewes grazing pasture showed a post-parturient rise (PPR) following lambing, whilst ewes grazing lotus had a reduced PPR in FEC. Up to day 70, FEC in lambs grazing lotus was lower than that for lambs grazing pasture, but between day 70 and the end of both experiments (approximately day 90), FEC in lambs grazing lotus increased to similar values as for pasture-fed lambs. FEC was not correlated with dag score or dag weight in ewes or lambs grazing pasture, but these indices were weakly and positively correlated in ewes and lambs grazing lotus, suggesting that lowering FEC on lotus also reduced dag formation. Under dryland farming conditions, the use of Lotus corniculatus (cv. Grasslands Goldie) during the spring/early summer lactation period can be used to increase lamb growth and wool production, whilst eliminating the need for pre-lambing anthelmintic drenching and, probably, reducing the amount of insecticide needed to control flystrike. These effects are probably due to the CT in lotus reducing rumen protein degradability and controlling internal parasites, and to the higher digestibility and voluntary feed intake (VFI) of lotus compared to perennial ryegrass ( Lolium perenne)/white clover ( Trifolium repens) pasture. The absence of endophyte in lotus may also have contributed to these effects.

Influence of nutrition and lactation on ovulation and conception in red deer

Reproduction incurs a high energetic cost and failure to meet nutritional needs results in reproductive failure. In red deer hinds, the interaction between nutrition, summer lactation and subsequent ovulation/conception is of particular interest for farmed deer production in NZ due to climatic constraints to summer pasture production in many areas. However, few studies have focussed on the potential perturbing effects of poor nutrition on lactational outputs and potential flow-on effects on ovulation/conception. As lacta tion in red deer naturally persists well beyond the autumn mating period, lactational anoestrus (through hormonal feedback mechanisms) is not a normal feature of the species reproduction. However, lactation is of high nutritional cost to the hind and can potentially exert considerable influence on the incidence and timing of conception via changes in hind liveweight, lipid depots and general body condition. Supporting evidence for this hypothesis is derived from studies of wild red deer within habitats marginal to species survival (e.g. Isle of Rhum, Scotland), where climatic variables greatly influence annual reproductive success of hinds. Under such conditions, even the differences in maternal investment (via lactation) required to raise male and female calves have been demonstrated to influence the subsequent success and timing of conceptions. Studies of farmed red deer in Scotland also demonstrated that hinds on different levels of pasture nutrition during lactation exhibited significant differences in conception date, with earlier conceptions favouring hinds on higher levels of nutrition. There is a growing body of evidence from monitoring of farmed red deer in New Zealand that the interaction between lactation and hind body condition score (BCS)/ liveweight influences subsequent conception rate and date. Recent studies on pre-rut versus post-rut calf weaning practices demonstrated effects of lactation on hind BCS and liveweight, calf growth rates and hind conception dates. These studies highlight the need to better understand the "costs" of lactation on reproductive performance, particularly under conditions of nutritional constraints. Keywords: lactation, nutrition, red deer, reproduction

Environmental constraints on reproductive performance of farmed deer

Optimum reproductive efficiency of farmed deer is often constrained by apparent maladaptation of wild cervids to a given farm environment or components of that environment. Seasonal breeding amongst forest-fringe species of northern temperate origin (e.g. red deer, fallow deer) benefits the species within its natural range, but often creates misalignment in southern temperate zones between the high nutritional demands of lactation in summer and the earlier peak of pasture production and quality occurring in spring. This can lead to increased calf mortality, decreased calf growth rates and depressed dam liveweights. Much emphasis has been placed on manipulating either pasture production patterns or the timing of birth to create better synchrony between the two. The latter largely involves artificial manipulation of the timing of conceptions (e.g. melatonin treatment), but there may also be options for genetic selection of deer for earlier calving patterns. Tropical cervid species farmed in temperate environments can exhibit either aseasonal reproduction (e.g. chital deer) or autumn-wintering calving patterns (e.g. rusa deer), leading to high mortality of neonates (hypothermia, predation) under uncontrolled breeding management. However, there are simple management options to synchronise and shift calving patterns to better align tropical species to temperate environments.

Interactions Between Body Condition at Calving and Cooling of Dairy Cows During Lactation in Summer

This study examined the interactions between dietary manipulation for increased body condition during the last trimester of pregnancy (spring) and postpartum cooling (summer lactation). Effects of diet on milk production of Holstein cows were examined to determine whether body stores could compensate for reduced DMI during heat stress. Cows calving between May and July with high (3.8 on a six-point scale) or low (2.7) body condition scores were assigned postpartum to be cooled by sprinkling and ventilation or to serve as uncooled controls. Cooled cows ate 1.6kg more DM/d and consumed 9L less of water/d than uncooled cows. Cooled cows maintained body temperatures below 38.9°C during day hours; peak body temperature for uncooled cows was 39.7°C. For 8 wk postpartum, glucose and insulin concentrations in plasma were unaltered by cooling or body condition. The NEFA were lower, and urea was slightly higher, for cows with low body condition. Milk production increased 1.9 kg/d with cooling, fat production increased with both body condition and cooling, and protein production increased with cooling but not with body condition. Performance was lowest for the uncooled subgroup with low body condition. Among cooled cows, no advantage was attributable to high body condition. An additive effect of high body condition and cooling on milk production in summer was not evident.

Manipulation of reproductive seasonality of farmed red deer ( Cervus elaphus) and fallow deer ( Dama dama) by strategic administration of exogenous melatonin

There is often a poor synchrony between the high energy demands of lactation in summer and the peak of pasture production and quality occurring in spring for red deer ( Cervus elaphus) and fallow deer ( Dama dama) farmed under pastoral conditions in temperate climates. Considerable research within the last decade has investigated either daily administration or constant infusion of exogenous melatonin in order to advance the breeding season and hence the seasonal pattern of births of farmed deer and, therefore, align lactation and feed production. Melatonin is the hormone involved in the transduction of photoperiodic information to the endocrine system leading to precise timing of reproduction. Owing to the absence of pregnancy and lactation, the pubertal hind/doe provides the simplest model for exogenously controlling the seasonality of oestrus, ovulation and conception. All forms of exogenous melatonin delivery initiated in summer (10–12 months of age) are effective in advancing the onset of puberty. However, the degree of advancement relative to control females has been highly variable, reflecting a wide range of treatment protocols. The most significant variables appear to be the time of onset of treatment and the degree of social interaction between treated and control animals. Initiation of treatments less than 100 days after the winter solstice are likely to delay puberty by impinging upon a possible photoperiod entrainment period. Initiation of treatments more than 100 days after the solstice advances puberty, with progressively later initiation dates generally resulting in smaller degrees of advancement. Melatonin-treated red deer hinds and stags appear to influence the timing of puberty of contiguous control hinds. The maximum degree of puberty advancement so far achieved by melatonin treatment has been 54 days for red deer and 56 days for fallow deer. In adult female deer, lactation does not appear to markedly influence the degree of phase shifting by melatonin treatment. However, because melatonin treatment initiated before the end of pregnancy, 140–170 days after the winter solstice, may prevent lactogenesis, the use of melatonin is contra-indicated during pregnancy. Treatment initiation after the onset of lactation does not appear to influence milk yields, as evidenced by calf/fawn growth rates. Treatment of adult male red and fallow deer during summer advances all aspects of reproductive seasonality. Coincident treatment of males and females appears to result in coincident early rutting and oestrous activity, leading to high conception rates. Long-term consequences of treatment of red deer stags include early sexual quiescence and occasional expression of transient testicular cycles, with re-synchronisation of treated and control stags occurring 14–15 months after the initiation of treatment. However, initiation of treatment of red deer stags less than 50 days after the winter solstice delays sexual quiescence and sexual recrudescence, indicating that increasing photoperiod in early spring is important in the entrainment process. While seasonal birth/lactation patterns for red and fallow deer can be advanced by exogenous melatonin treatment, research is needed to elucidate the actual effects on overall productivity, particularly in relation to calf/fawn growth rates and the impact of precocious puberty in early-born animals.