Short Lactation Period Research Articles

Pre-pubertal and postpartum anestrus in tropical Zebu cattle

Bos indicus breeds, commonly known as Zebu cattle, have spread from their center of origin in Western Asia into large areas of Asia (including the Asia-Pacific basin), Africa, South and Central America (including the Caribbean islands). The original Zebu genotype, however, has been modified by planned and unplanned cross-breeding programs involving many native and Bos taurus breeds in their new habitats. Though accurate estimates are not available, more than half of the world’s cattle population includes a proportion of B. indicus germ plasm. B. indicus native breeds have developed by natural selection over centuries for their ability to survive in rough, harsh tropical environments. Most of these non-descript breeds still exhibit high fertility, in terms of calving rates, and disease resistance but they grow very slowly and take well over 3 years to reach puberty and produce only a few liters of milk over a short lactation period. Selection has been carried out in some areas and distinct Zebu breeds have been developed that have moderately high growth rate and milk production. However, they are slow breeders and have extended pre-pubertal and postpartum anestrous periods, compared to their temperate counterparts exposed to similar environment and management. The reproductive biology of B. indicus is similar to that of B. taurus. Most of the proven management, nutritional, hormonal and biotechnological interventions developed through experimentation with B. taurus breeds are equally applicable to B. indicus and their crosses. Zebu breeds predominate in most tropical countries where the majority of the human population lives. If meat and milk production are to be increased in the tropics, Zebu cow productivity, in terms of number of calves produced per lifetime or per unit area of land, must be increased and the time from birth to slaughter must be reduced. This goal could be achieved either by selection within local Zebu populations or through planned cross-breeding with B. taurus breeds. Because the productive and reproductive potentials of Zebu cattle are relatively low, worthwhile gains could only be achieved by selection over many generations. This would require substantial investment in labor, feed and drugs that may not be economic since the return from such investment is relatively low. However, many studies have shown that cross-breeding with B. taurus, which combines additive, dominance and epistatic effects of the two genotypes, ensures high productive and reproductive performance. Therefore, planned cross-breeding with suitable B. taurus breeds, although demanding additional investment in labor, feed and drugs, will still be economic because the return far exceeds the costs.

Mammary gland growth in the lactating sow

The short lactation period of the modern sow is critical for determining the success of piglet survival and growth. Increases in milk production during early lactation may result from increases in secretory cell numbers, enhancement of functional differentiation of cells, or both mechanisms. The porcine mammary gland undergoes substantial growth during lactation. Mammary tissue wet weight can increase by more than 50% and total mammary gland DNA by 100% during a 21-day lactation. Postpartum mammary growth parallels the increase in milk production observed during lactation. Mammary growth during lactation is affected by litter size, dietary intake, and gland location, as well as by a number of other factors. A primary factor influencing postpartum mammary growth is removal of milk from the gland. A suckled mammary gland, in combination with the piglet that suckles it, form an interdependent growing unit. Mammary glands which are underdeveloped at parturition can still grow rapidly in response to suckling. The sow’s mammary gland has tremendous potential for growth during early lactation. Approaches for enhancing mammary gland growth during early lactation offer substantial potential for enhancing milk yield and piglet growth.

Early development of climbing skills in harvest mice

The tiny harvest mouse, Micromys minutus , is skilled at climbing among grasses. Owing to the short lactation period of 15–16 days, young harvest mice need to achieve this climbing skill very rapidly. We examined the early development of five components of climbing behaviour and the final climbing pattern of harvest mice from birth to weaning. During the lactation period, the pups’ climbing ability developed rapidly and they were able to climb a vertical bar by the time they first emerged from their nest. Climbing skills were acquired in the following order: hand grasping at 3–7 days; foot grasping at 6–9 days; quadruped stance at 6–11 days; tail prehension at 10–11 days; and righting at 10–12 days. The ratio of foot digit length to foot length was greater in harvest mice than in laboratory mice, Mus musculus , indicating a better grasping ability in the former.

Reproductive Decisions in Female European Ground Squirrels: Factors Affecting Reproductive Output and Maternal Investment

Physiological and behavioural parameters associated with reproductive effort and success were investigated in female European ground squirrels Spermophilus citellus. The proportion of reproductive (lactating) females in the study population was over 90% and was not related to age. Timing of oestrus and ovulation was found to be affected by the female’s emergence date and condition. Females with low emergence mass showed delayed oestrus. Differences in ovulation dates were shown to affect reproductive output in terms of litter size and sex ratio. Early litters were larger and male biased. X‐ray techniques were used to determine intrauterine litter size in individual females. The results indicated that litter size and sex ratio were fixed prenatally. Lactation costs were reflected in the intensity of mass loss and duration of lactation. Mass loss varied with litter size, in that females with large litters showed a more rapid loss than others. The second parental investment parameter, lactation duration, varied among individual females and was dependent on the timing of reproduction and litter size (except yearlings). Early born litters, which were, in most cases, larger than later ones, were nursed longer. Prolonged lactation periods affected female condition in that they started prehibernation fattening later and entered hibernation with a lower mass than individuals that had shorter lactation periods. Yearling females probably could not afford the energetic costs of long lactation, independent of their offspring number. These results indicated that females with higher reproductive output and higher investment were unable to compensate these costs before hibernation. Consequences for these individuals could therefore be lower over‐winter survival or a delayed oestrus in the following season.

Behaviour and energetics of ice-breeding, North Atlantic phocid seals during the lactation period

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 187:265-281 (1999) - doi:10.3354/meps187265 Behaviour and energetics of ice-breeding, North Atlantic phocid seals during the lactation period Christian Lydersen1,*, Kit M. Kovacs1,2 1Norwegian Polar Institute, 9296 Tromsø, Norway 2Department of Biology, UNIS, 9170 Longyearbyen, Norway *E-mail: lydersen@npolar.no ABSTRACT: This review presents a comparative analysis of the behaviour and energetics of the ice-breeding phocid seals of the North Atlantic in relation to their habitat(s). In very broad terms, it suggests that the term 'ice-breeding' is too simplistic and may lead to misconceptions about the actual degree of variability that exists in the breeding habitats of seals that do not give birth on land. The variation that exists within ice habitats is quite remarkable in terms of: temporal and structural stability of the pupping platform; the degree to which animals have access to the water; the risk of predation; and perhaps also the local availability of food. These factors all appear to influence the behaviour of mothers and pups and the allocation of energy during the lactation period of the species studied. Two basically different nursing strategies can be identified that may have evolved, at least in part, as a consequence of variation in these variables. The pattern displayed by grey (Halichoerus grypus), harp (Phoca groenlandica) and hooded (Cystophora cristata) seals involves a short lactation period, during which a large amount of energy is transferred from the mother to the pup through extremely-energy-rich milk. Pups of these species are very inactive and consequently a very high proportion of the received energy can be stored as body tissue, mainly in the form of subcutaneous blubber. The mothers generally feed little or not at all during the nursing period and the pups are weaned abruptly, having not yet entered the water in most cases. The other strategy, found in bearded (Erignathus barbatus) and ringed (Phoca hispida) seals, involves a longer lactation period, where less-energy-rich milk is transferred to very active pups. These pups learn to swim and dive during the nursing period, and are weaned with body compositions that are similar to those of adults. The mothers feed during lactation and weaning is less abrupt, with pups feeding independently, while still receiving milk from their mothers. KEY WORDS: Behaviour · Diving · Lactation · Maternal investment · Ice-breeding seals Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 187. Publication date: October 14, 1999 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1999 Inter-Research.

FACTORS AFFECTING MATERNAL EXPENDITURE IN SOUTHERN ELEPHANT SEALS DURING LACTATION

Southern elephant seals Mirounga leonina provide a unique opportunity for examination of parental investment because postpartum pup growth is fueled exclusively by energy from stored reserves in fasting mothers, and the seals are extremely sexually dimorphic as adults. We examined the influence of pup sex, maternal size, and other factors on the variation in postpartum maternal mass change and pup growth. Elephant seals (178 mothers and 445 pups) were weighed during four breeding periods at South Georgia Island. Maternal mass change during lactation increased markedly with the mass of the mother at parturition. Postpartum maternal mass accounted for 75% of the variation in mass loss and 62% of the variation of pup mass at weaning. Size of the pup at birth explained <4% of this variation, and the sex of the pup explained virtually none (<0.1%). The duration of lactation was positively correlated with the pstpartumo mass of mothers, but negatively correlated with the rate of maternal mass loss when corrected for the effect of maternal postpartum mass. Mothers giving birth late in the season had shorter lactation periods than those that gave birth early but seemed to compensate for this by increasing the rate of mass transfer. Average transfer efficiency (pup mass gain/maternal mass loss) was 46±0.5%. Mothers lost, on average, 35% of their postpartum mass during lactation and 40% during the whole breeding period. Females whose postpartum mass increased between seasons increased their expenditure on their pups; females whose postpartum mass decreased, decreased their expenditure. These data from mothers with single pups do not clarify whether differences in investment were controlled by mothers or their offspring. However on three occasions, study females raised two pups in a season. Despite the increased demand, these females did not increase their expenditure, suggesting that levels of investment are maternally controlled. These results show that levels of expenditure in southern elephant seals appear to be determined largely by a single variable: female mass at parturition.

Factors Affecting Maternal Expenditure in Southern Elephant Seals During Lactation

Southern elephant seals Mirounga leonina provide a unique opportunity for examination of parental investment because postpartum pup growth is fueled exclusively by energy from stored reserves in fasting mothers, and the seals are extremely sexually dimorphic as adults. We examined the influence of pup sex, maternal size, and other factors on the variation in postpartum maternal mass change and pup growth. Elephant seals (178 mothers and 445 pups) were weighed during four breeding periods at South Georgia Island. Maternal mass change during lactation increased markedly with the mass of the mother at parturition. Postpartum maternal mass accounted for 75% of the variation in mass loss and 62% of the variation of pup mass at weaning. Size of the pup at birth explained <4% of this variation, and the sex of the pup explained virtually none (<0.1%). The duration of lactation was positively correlated with the pstpartumo mass of mothers, but negatively correlated with the rate of maternal mass loss when corrected for the effect of maternal postpartum mass. Mothers giving birth late in the season had shorter lactation periods than those that gave birth early but seemed to compensate for this by increasing the rate of mass transfer. Average transfer efficiency (pup mass gain/maternal mass loss) was 46±0.5%. Mothers lost, on average, 35% of their postpartum mass during lactation and 40% during the whole breeding period. Females whose postpartum mass increased between seasons increased their expenditure on their pups; females whose postpartum mass decreased, decreased their expenditure. These data from mothers with single pups do not clarify whether differences in investment were controlled by mothers or their offspring. However on three occasions, study females raised two pups in a season. Despite the increased demand, these females did not increase their expenditure, suggesting that levels of investment are maternally controlled. These results show that levels of expenditure in southern elephant seals appear to be determined largely by a single variable: female mass at parturition.

A Phylogenetic Perspective on the Evolution of Reproductive Behavior in Pagophilic Seals of the Northwest Atlantic as Indicated by Mitochondrial DNA Sequences

The ice-breeding (pagophilic) habits and relatively short lactation periods of several species of “true” seals (Phocidae) of the Northwest Atlantic, including the harp seal ( Pagophilus ), bearded seal ( Erignathus ), and hooded seal ( Cystophora ), usually are assumed to have evolved in parallel. Current taxonomy regards Pagophilus and ringed seals ( Pusa ) along with harbor seals ( Phoca vitulina ) as subgenera of Phoca , unites Phoca (sensu lato) together with gray seals ( Halichoerus ) and Erignathus in the subfamily Phocinae, and places Cystophora with elephant seals ( Mirounga ) in a separate subfamily, Cystophorinae. Cladistic analysis of variation in the DNA sequence of the mitochondrial cytochrome b gene identifies three clades among northern seals: Phoca-Pusa-Halichoerus, Cystophora-Pagophilus , and Erignathus. Erignathus is the sister group to the other species examined. Each clade may be regarded as a tribe of the subfamily Phocinae (the Phocini, Cystophorini, and Erignathini, respectively). The phylogeny suggests that the ice-breeding habit and associated brief lactation are ancestral characters for the Phocinae and that instances of fast-ice or terrestrial breeding are convergences on the ancestral condition in other phocid subfamilies.

Reproductive transfer and variation of body load of organochlorine pollutants with age in fin whales (Balaenoptera physalus)

The body load of tDDT (p,p'DDT + o,p'DDT + p,p'DDE + p,p'TDE) and polychlorinated biphenyls (sum of congeners) was estimated for 169 fin whales to study age and sex-related variation and to calculate the quantity of these compounds transferred to offspring through reproduction. Blubber was the body compartment containing the greatest quantities of organochlorines, but its relative contribution to total load was lower than in other cetaceans because in fin whales muscle and bone are also significant lipid reserve sites. In male fin whales, organochlorine body loads increased with age but tended to reach a plateau in fully grown individuals. In adult females, loads decreased with age because of transfer to offspring cancelling the rise in loads associated with body growth; as a consequence, the amount of organochlorines transferred during a reproductive cycle also declined with age. This transfer is lower than that found for other cetaceans because fin whales have a shorter lactation period. According to the calculations, the first offspring of a female fin whale receives about 1 g of PCB and about 1.5 g of tDDT. These amounts will progressively decrease in subsequent reproductive cycles to reach a minimum of 0.2 g PCB and 0.3 g tDDT in an old female. Therefore, the first calf delivered is the one most likely to be affected by pollutants.

Changes in N-Acetyl-β-D-Glucosaminidase Activities in Relation to Other Milk Components Throughout Normal Lactation in the Guinea Pig

Changes in milk production, NAGase activities, Na, Cl, K, lactose, total N, and fat were followed throughout normal lactation in 26 healthy guinea pigs. Appropriate microassays were used and all determinations were performed on the same small skim milk sample (microhematocrit tube). A very sensitive and rapid spectrofluorimetric determination of NAGase in 10-µl skim milk samples was evaluated.Four days after parturition, daily milk production reached a maximum of about 20ml. Thereafter milk yield decreased progressively to about 7ml on d 15. During the entire course of lactation, a progressive increase in NAGase, total N, fat, Na, and Cl was observed. However, K and lactose decreased. Highly significant positive correlations between NAGase and Na, Cl, fat, and total N were evident, whereas correlations were negative between NAGase and K, lactose, and milk production. These changes can be explained on basis of alterations that occur at the level of the blood-milk barrier. The short lactation period of the guinea pig, the easy handling and milking practices, together with the available sensitive micromethods can lead to the establishment of a convenient guinea pig mastitis model.

Changes in Composition and Energy Content of Harp Seal Milk during Lactation

Milk samples were obtained from stomachs of 26 harp seal pups, Phoca groenlandica, at various stages during lactation. In addition, morphometric data were obtained for these pups and for 20 of their respective mothers. Fat, and hence energy content, of milk increased during lactation; water content declined, whereas protein and ash remained constant. Fat, water, and energy content were significantly correlated with pup age, a measure of the stage of lactation of the female, and with female condition which also declined during the nursing period. Trends observed in milk composition in the present study were similar to those reported for several other phocid seals but differed significantly from an earlier examination of harp seal milk. The high fat content of harp seal milk transfers large amounts of energy to the pup during a short lactation period, facilitating rapid neonatal growth. In addition, the replacement of water with fat in milk as lactation proceeds conserves water, and this may be important in...

Reproductive Efficiency and Viability in two Bos Indicus and two Bos Taurus Breeds in the Tropics of India and Colombia

Records from two herds in India and two in Columbia representing respectively two breeds of Bos indicus (Hariana and Deshi) and two Bos taurus breeds—Blanco Orejinegro (BON) and Costeño Con Cuernos (CCC) were evaluated for breeding efficiency and viability. Average age at first calving was 52.1, 46.3, 39.5 and 40.7 months for Hariana, Deshi, CCC and BON. Season of birth did not influence age at calving. Ranking for calving interval was similar, average 479, 418, 396 and 382 days with season effects significant (P<.05) for only Deshi. BON and CCC had fewer days open but much shorter lactation periods, average 73 and 157, thus days carried calf in lactation were similar for all breeds. Percent of time dry per calving interval was high for all breeds, 44.2, 36.7, 64.1 and 81.0 for Hariana, Deshi, BON and CCC. Average annual mortality of females by 12 months of age was 23.6% for Hariana, 17.0% Deshi and 27.0% BON. In the same herds 46.4%, 51.1% and 49.0% of females born alive lived to first calving and annual losses among cows were 18.0%, 17.0%, and 21.0%; therefore, affording little opportunity for selection among females. Temperament, as determined by response to the milking process with and without the calf present, showed all the breeds were similar in this respect. Environmental effects were most important for all traits but genetic differences were indicated for age at first calving and milk yield. On a theoretical basis little gain could be expected in net dairy merit from crosses between the Columbian and Indian breeds.

The effect of the uterine cervical stimulation at postpartum estrus upon the post-weaning fate of the lactational corpora lutea.

Effects of the uterine cervical stimulation applied at the postpartum estrus was examined in the lactating rats whose pups were removed on various days from 0 to 26 day after parturition. The changes of vaginal smear and the secretion pattern of progestins were followed. In the animals either with (experimental group) or without (control group) the stimulation, the continuation of lactation beyond 24 days after parturition caused the appearance of vaginal estrus. With the shorter lactation periods, however, vaginal estrus appeared only after weaning, and the average date of appearance was about day 3 of post-weaning in the control and day 13 in the experimental group. The length of the post-weaning diestrus in the experimental group coincided with that of pseudopregnancy. The secretion pattern of progestins also strongly suggested that pseudopregnancy had initiated at the time of weaning. If this was the case, the effect of the cervical stimulation would be carried over through the lactation period.Contrary to the post-weaning secretion patterns of progestins, those of the lactation period were quite similar in both groups. Terefore, the difference of the post-weaning life span of the corpora lutea between the experimental and control groups could not be attributed to the amount of progesterone secreted at the time of weaning. From the results of the daily inspection of the ovaries and tubal ova, it was concluded that the corpora lutea existing during the post-weaning diestrus were formed at postpartum ovulation and an alternation of corpora lutea was not seemed to take place.

The Damascus Cow—An Unexplored Source of Dairy Germ Plasma

Summary Damascus cattle are an excellent indigenous breed, showing a high potential for milk production, longevity, heat tolerance, and disease resistance. All of these qualities make it highly desirable as a milk producer in areas with hot, arid, or subtropical climates. In spite of many desirable qualities some important defects have crept in and are being accentuated, namely: 1.Short lactation period in some strains. 2.Disproportionate body depth to height. 3.High-set sacro-eoccygeal articulation with the pelvis. 4.Narrow pelvic outlet. 5.Fine bone. None of these defects are characteristic of the breed and a large number of animals are free from such defects. Future development of breed will depend upon a planned and controlled breeding and selection program.

Calculating the Average Production of a Dairy Herd

Summary 1. There is lack of uniformity among methods employed in the United States in calculating the average production of herds in cow testing associations. Some of these methods are inaccurate. A comparison of the results obtained by these methods, has been made on the production records of the N herd of the Sunflower Cow Testing Association in northwestern Kansas. 2. The equivalent average method gives an inflated valuation which is especially increased in herds of cattle yielding a large flow of milk in short lactation periods. 3. The rough average method is too greatly influenced by cows passing only a part of their lactation period in the testing association's fiscal year. 4. The herd average method (unmodified) excludes cows passing only a part of the lactation period during the fiscal year. Yet these cows were an integral part of the producing herd for a part of the year. Modifications of the herd average method introduce an error increasing with the shorter records accepted as full lactation periods. 5. The cow-month method is practically identical with the Danish method. Slightly larger errors may be incurred through use of months rather than exact days. No allowance is made for any dry period with part-time producers, thus slightly overvaluing the herd average. The percentage of error, however, is small by this method. 6. The Danish method bases the number of cows upon feeding days of lactating and dry cows, using 365 days as the standard. It closely approaches accuracy, though tends to over-value part-time cows. 7. The lactation average method is based upon the average length of lactation of the normal cows in the herd, and calculates the remaining part-time producers according to the normal length of lactation of the herd cows. 8. The four last methods named all approach accuracy. Of these, the lactation average method more nearly represents the normal management of the herd, and the true average production.