Late Weaning Research Articles

Children's height, health and appetite influence mothers' weaning decisions in rural Senegal.

In many developing countries, breastfed children have a lower nutritional status than those weaned from 12 months of age. Reverse causality, that is, earlier weaning of healthy and well-nourished children, is a possible explanation. Maternal reasons for early and late weaning were investigated in a cohort of 485 rural Senegalese children using structured interviews during two rounds at the ages of 18--28 and 23--33 months, respectively. Length, weight and height were assessed, and dates of weaning were monitored. The mean duration of breastfeeding was 24.1 months (quartiles 21.9 and 26.3). Two-thirds of mothers of breastfed children under 2 stated that they would wean at the age of 2, while for breastfed children aged 2 years, a 'tall and strong' child was the most prevalent criterion. The main reasons for weaning prior to 2 years (N = 244) were that the child ate well from the family plate (60%), that the child was 'tall and strong' (46%) and maternal pregnancy (35%). The main reasons for weaning later than the age of 2 were: a 'little, weak' child (33%), food shortage (25%), illness of the child (24%) and refusal of family food (14%, N = 120). Children breastfed above the age of 2 because they were 'small and weak' had lower mean height-for-age and a greater prevalence of stunting than children breastfed late for other reasons (P < 0.0001). The habit of postponing weaning of stunted children very likely explains why breastfed children have lower height-for-age than weaned children in this setting.

Breastfeeding duration in a multiethnic population in Hawaii.

The increasing ethnic diversity in the United States necessitates a study of variations in infant feeding patterns among ethnic groups. This study was conducted as part of Hawaii's surveillance system to identify infant feeding patterns in Hawaii; specifically, to identify factors influencing duration of breastfeeding among ethnically diverse mothers. All women who delivered an infant in Hawaii between January 1 and March 31, 1989, were mailed surveys 14 to 19 months after delivery. Fifty-one percent (n = 2011) of women responded, of whom 1574 (78%) did some breastfeeding and are included in the analysis of prediction of weaning (cessation of breastfeeding). Cox regression (survival) analysis was used to predict weaning. The median duration of breastfeeding was 150 days; 45 percent of infants were still breastfeeding at age 6 months and 16 percent at age 1 year. Factors associated with early weaning were Japanese ethnicity; mother born in a country other than the United States, Japan, or the Philippines; first language other than English, or two languages at home; employed full-time outside the home; introduced formula or fruit before age 6 months; received formula from the WIC program; and stopped breastfeeding for convenience, breast problems, problems getting breastfeeding started, insufficient milk, baby refusing the breast, and a sick baby. Factors associated with late weaning were older maternal age; college education; living on a rural island; previous breastfeeding experience; helpful breastfeeding advice from family or friends; receiving WIC for breastfeeding mothers; introducing the cup before age 6 months; and not giving fruit to the baby. In Hawaii, programs that address how and when to introduce foods, use of formula, and management of outside employment and breastfeeding should be made available to those groups of women at risk for early weaning to lengthen their duration of breastfeeding.

Intestinal parasites in swine in the Nordic countries: multilevel modelling of Ascaris suum infections in relation to production factors.

In Denmark, Finland, Iceland, Norway and Sweden, 413 sow herds were randomly selected for sampling. Faeces from pigs of 7 age groups/categories were examined for helminth eggs (11,233 individual samples), and an accompanying questionnaire was completed at each visit. In total, 1138 pigs on 230 farms were found to be positive for Ascaris suum. Considerable differences in the occurrence of A. suum could be observed directly for several of 20 independent variables at the herd or category level. However, given that univariate analyses may be severely affected by confounding of covariates resulting in spurious inference, additional multivariate analyses were undertaken. An ordinary logistic regression on Ascaris positive/negative farms showed that Denmark had the highest frequency of infected herds, while Iceland and Finland had the lowest frequencies and that herds using 'late weaning' and 'Class 2' drugs (pyrantel, levamisole) were most often infected. Because many herds were found to be totally negative for A. suum, mixed hierarchical logistic-normal regression models (both the penalized quasi-likelihood and the Markov Chain Monte Carlo methods) were developed for both a full (all herds) and a reduced (the 230 infected herds) data set using either a cut-off of > 0 eggs per gram (epg) or > 200 epg to counter for false-positive egg counts. Estimates for identical models, but where the animal level variance was constrained to the binomial assumption, were also calculated. Significant covariates were robust to model development with 'Age group', 'Country', 'Weaning age', 'Water system' and simple interactions between the latter two and 'Age group' being significantly associated with the occurrence of A. suum, while all variables concerning anthelmintic drug, anthelmintic strategy, floor type, bedding, dung removal, washing and disinfection were not. These findings are discussed in the light of the complex relationship between A. suum and its pig host.

Parental barriers to weaning infants from the bottle.

Optimal bottle weaning should occur between 12 and 15 months of age. We hypothesized that high-risk populations have different parental attitudes, learned behaviors, and knowledge of weaning practices. To determine whether high-risk populations are less likely to wean their children by 15 months of age than low-risk populations. A cross-sectional survey using a convenience sample of parents was conducted at 3 community-based pediatric clinics. Spanish- and English-speaking parents with weaned and unweaned children 12 to 36 months of age were included in the study. A self-administered questionnaire was completed at a clinic visit. The questionnaire addressed aspects of parents' sociodemographic characteristics and included feeding history; weaning practices; sources of information about weaning; and parental behaviors, attitudes, and knowledge of age at which the child should be weaned. One hundred eighty questionnaires were completed. Marital status was related to weaning behavior. Seventy-six percent of single mothers had weaned their children in a timely manner, whereas 48% of married mothers had done so (chi2 = 7.70; P = .008). Parental education, race, and income were not significantly related to the timeliness of weaning. When respondents rated the helpfulness of multiple sources, only the health clinic was found to be significantly more important for the timely weaning group (t = -2.13; P = .04). Parents with timely weaned children stated that the mean +/- SD optimal age for weaning is 13.6 +/- 3.2 months. Parents with unweaned and late-weaned children stated that the mean +/- SD optimal age is 19.9 +/- 6.6 months. Bedtime bottle feedings were reported in more than 87% of the unweaned group. Sixty-nine percent reported poor dental development associated with delayed weaning. Married parents are at risk of late weaning. Parents continue to allow their children to sleep with milk bottles in their mouths in bed at night. Parents are not aware of the medical problems associated with late weaning. Late-weaning parents are not knowledgeable about current weaning recommendations. Current approaches are not effective in altering set patterns of inappropriate weaning habits. Additional interventions and innovative parental education methods are needed to improve age-appropriate weaning practices.

Colonic fermentation capacity in vitro: development during weaning in breast-fed infants is slower for complex carbohydrates than for sugars

Fresh feces from 27 healthy infants-12 breastfed (complete, exclusive breast-feeding), 7 in early weaning (partial, high breast-feeding), and 8 in late weaning (partial, low breast-feeding)-were cultured with simple and complex carbohydrates in vitro to test the hypothesis that colonic fermentation capacity for carbohydrates increases during weaning. Infants in all three groups were able to ferment sugars, with no significant differences in median total short-chain fatty acid (SCFA) concentrations (mmol/L): preweaning, 56.4(range: 0-77.6); early weaning 68.5(range: 57.9-98.8); late weaning, 61.3(range: 28.6-120.4) for glucose. Preweaned infants were less able to ferment oligosaccharides and complex carbohydrates than were weaned infants (P < 0.05). Ability to ferment raftilose was higher in early weaning; median total SCFA concentrations (mmol/L) were as follows: preweaning 31.0 (range: 3.6-48.9), early weaning 57.1 (range: 2.5-70.6), late weaning 68.6 (range: 22.0-113.4) (P < 0.05). Ability to ferment complex carbohydrates did not develop until late weaning; median total SCFA concentrations for guar gum (mmol/L) were as follows: preweaning 6.4 (range: 0.1-57.3), early weaning 18.4 (range: 0.0-40.5), late weaning 45.4 (range: 15.6-62.1) (P < 0.05, preweaning and early weaning compared with late weaning). Development of the ability to ferment complex carbohydrate was slow. Cultures of feces from preweaned infants produced eight times more SCFAs with glucose than with complex carbohydrates, at early weaning there was a threefold difference and by late weaning the difference was only 25%, but this was still only 42% of the SCFAs produced by cultures of adult feces. These data suggest that for the complex carbohydrates tested, colonic fermentation is likely to contribute only a small proportion of daily energy needs of weaning infants.

Effect of early and late weaning on the growth of female kids

An attempt was made to develop a feeding system that would produce female kids able to start breeding early, at 7–8 months, with average body weight (BW) of 30 kg . A second objective was to measure dry matter intake (DMI) to calculate the cost of the rearing process. Two weaning ages were tested: one with an abrupt early weaning at 10 kg; the other with late partial weaning until BW reached 15 kg. The first group (48 goats) reached 25.9 ± 2.9 kg in 120 days, with a daily weight gain of 98 ± 35 g on average. These kids achieved 30 kg at 210 days and their reproductive weight at 9 months of age. Group 2 (28 animals) was first to reach the objective (180 days), and that time added to 60 days nursing gave a total of 8 months (30.3 ± 2.9 kg BW), with a daily gain of 120 ± 35 g on a diet of 26.5 kg extra milk during partial weaning. Total DMI of goats in Group 1 was 175 kg (103 kg alfalfa and 72 kg concentrate), while Group 2 DMI was 230 kg (135 kg forage and 95 kg supplement). The total cost per goat to achieve 30 kg was US$26.39 for early weaning and US$39.54 for late weaning, which showed a 33% higher cost for late weaning. Feeding systems represented between 67 and 86% of the total cost of rearing, but that would be recovered if the kids were sold for meat at local prices. It was concluded that faster growth could be obtained if milk was supplied for a longer period than the usual abrupt weaning at 10 kg. However, in both systems, animals could be available for breeding at 8–9 months of age, to kid at 13–14 months of age.

Der Einfluß des Pansenstoffwechsels auf zyklische N‐Verbindungen im Blutplasma von Wiederkäuern

The purpose of this paper was to study the effect of rumen metabolism on the concentration of certain cyclic N-compounds in blood plasma. The plasma from two groups of lambs in the phase of rumen development during early and late weaning was used. As a second model, samples from steers fed at maintenance and after emptying of the rumen via cannula were used. Plasma samples were obtained from the jugular vein in regular intervals. The HPLC-technique was employed as analytical method. The plasma levels of allantoin and of hippuric acid increased about 2.2-3.7 fold and 2.4-6.4 fold in lambs during rumen development. They decreased to about 43% and 13% after emptying the rumen of steers. These metabolites appear to reflect rumen protein synthesis and fibre breakdown and are considered useful estimators of rumen function. Cytidine, uridine, uric acid and hypoxanthine were only influenced in part by rumen metabolism. Plasma pseudouridine was decreased and creatinine was increased in lambs in relation to body mass and remained unaffected in steers.

Ontogeny of la messenger RNA in the mouse small intestinal epithelium is modulated by age of weaning and diet

Background: Exogenous antigenic peptides are presented to T cells by class II major histocompatibility complex (la) molecules on the surface of antigen-presenting cells. Class II-associated invariant chain (li) is also required for effective antigen presentation. Because messenger RNAs (mRNAs) for li chain and for class II l-Aβ chain appear in the mouse intestinal epithelium after weaning, experiments were conducted to test the effect of age of weaning and diet on the appearance of la and li mRNA. Methods: Four litters were split at day 17; one half was weaned and the other remained with the mother until day 24. On day 23, 25, 27, and 29, enterocytes were isolated from full-length small intestine by vascular perfusion with 30 mmol/L ethylenediaminetetraacetic acid, and the RNA was extracted. Results: Appearance of li and l-Aβ was significantly delayed by late weaning, as judged by RNA hybridization blots (li chain) and complementary DNA amplification (l-Aβ chain). In mice on elemental diets, the appearance of li and l-Aβ chain was delayed compared with littermates reared on standard chow, li mRNA failed to appear in mice maintained on the elemental diet by day 40, despite normal growth. Conclusions: Appearance of mRNA for both la and li depends on the introduction of a complex diet and not the “stress” of weaning or elimination of breast milk. Introduction of foreign dietary antigens or development of an altered intestinal flora may contribute to this process.

Marine Fish Larvae Feeding: Formulated Diets or Live Prey?

AbstractIn the rearing of larval marine fish, any diet that reduces dependance on live prey production is of technical and economic interest. Weaning juveniles with a completely developed digestive tract to a conventional diet, (i.e., “late weaning”) can be successful in any marine fish species. For example, weaning one‐month‐old sea bass (20 mg) to the study's reference diet, Sevbar, resulted in over 85% survival (40% from hatching) and 1.25 g fish at day 90 (at 19 C)In contrast, “early weaning” of larvae to special microdiets during the first month is still difficult. The best way to reduce live prey utilization in sea bass is to wean larvae at about 3–4 mg in size (day 20). If weaning could be accomplished 15 days earlier, Artemia savings could be as high as 80%. However, this introduces risks relative to growth retardation (30% weight loss) and lower juvenile quality, including greater size variability and skeletal abnormalities. Similar results have been obtained with commercial microparticles (Fry Feed Kyowa) and experimental microbound diets (MBD) made from raw materials (alginate MBD) or preferably from freeze‐dried protein sources (zein MBD).Total replacement of live prey is still impossible in marine fish. Sea bass larvae fed formulated diets exclusively from first feeding (0.3 mg larval wet weight), or even from their second week of life onwards, exhibited low survival and poor growth. Better results can be obtained when formulated diets are used in combination with live prey from first feeding, although the optimal ratio of live prey to formulated diet is still to be specified.

A path analysis of some determinants of infant growth in Khartoum.

The interrelationships between some socioeconomic and behavioural characteristics of mothers and the growth and illness experience of their infants in poor Khartoum townships have been examined by path analysis. For both infant body weight and supine length it is shown that weaning age and illness experience are important determinants of growth. It is also shown that greater maternal income has disadvantageous effects through encouraging early weaning. Most importantly the infants of housewives have later weaning, less illness and greater weight and length at 1 year of age than the infants of mothers with jobs, showing the value of time for caring in the prevailing environmental circumstances.

Changes in activities of lipogenic enzymes in adipose tissue and liver of growing goats.

The lipogenic capacity of omental adipose tissue and liver was measured in vitro from samples obtained at slaughter from 33 young male goats. The animals were slaughtered either on the day of weaning (d 0) or 2, 14, or 56 d after weaning. Ages at weaning were 4 wk (early weaning) or 6 or 8 wk (late weaning). Blood samples from the jugular vein were taken before slaughter to measure the concentrations of plasma glucose and nonesterified fatty acids. There was a 30% decrease in glucose concentration after weaning. Nonesterified fatty acid concentration increased fourfold between d 0 and 2 after weaning. By d 14 after weaning, nonesterified fatty acids returned to basal concentration. The lipoprotein lipase (LPL) activity of adipose tissue declined markedly (90%) on d 2 after weaning. Lipoprotein lipase activity returned to preweaning values by d 56 after weaning in those goats that had ad libitum access to feed. In adipose tissue, nicotinamide adenine dinucleotide phosphate (NADP)-malate dehydrogenase activity fell by only 17% by d 2 after weaning and to 63% by d 14 after weaning. Lipoprotein lipase activity was closely related to metabolizable energy intake the day before slaughter. Acetyl-coenzyme A carboxylase activity was low in adipose tissue and it increased only slightly by d 56 after weaning. The data indicated that LPL played a preponderant role in the restoration of lipid stores after weaning. High NADP-malate dehydrogenase activity together with a high concentration of plasma glucose by d 56 after weaning suggested that this enzyme activity could be enhanced by high glucose availability in goat kids. Activities of lipase, acetyl-coenzyme A carboxylase, NADP-malate dehydrogenase, and glucose-6-phosphate dehydrogenase in liver were essentially unaffected by weaning. The extent and rapidity of change of lipogenic enzymes of goat kids was much more pronounced in adipose tissue than in liver.

Dietary Regulation of Intestinal Glycosyl-Transferase Activities: Relation between Developmental Changes and Weaning in Rats

Activities of rat intestinal fucosyl-transferase (GDP-fucose: glycoprotein fucosyl-transferase; EC 2.4.1.68) and sialyl-transferase (N-acetylneuraminyl-transferase; EC 2.4.99.1) respectively exhibited a significant increase following weaning and a steady decrease between birth and weaning. The variations of the two glycosyl-transferase activities with age could not be explained by the presence of inhibitory factors in microsomes or cytosol, nor were they due to a natural modification of the milk composition at the end of lactation. The increase in fucosyl-transferase activity that followed weaning was prematurely induced by early weaning. Prolonged nursing prevented the normal increase in fucosyl-transferase activity, and late weaning delayed the increase. The sensitivity to the modification of the time of weaning indicated a major effect of dietary changes, related to the introduction of a solid carbohydrate-rich diet, on the developmental pattern of this enzyme. However, a stress response could not be excluded after early weaning since the corticosterone level of the early weaned rats was enhanced as compared to that of suckling rats. For sialyl-transferase, early weaning caused a slightly greater than normal decrease in the activity, whereas prolonged nursing only weakly diminished the normal decrease in the activity. Moreover, late weaning had no effect on the sialyl-transferase activity. The age-related variations of this enzyme likely are due to factors independent of diet. Thus, the developmental variations of the fucosyl- and sialyl-transferases appear to be differently regulated.

Changes in Blood Glucose, Nonesterified Fatty Acids, and Ketones in Response to Weaning and Feed Intake in Young Calves

Effects of weaning age on blood glucose, ketones, and nonesterifid fatty acids were examined using 16 Holstein heifer calves. Animals entered the study at 6±3.5 d of age and were fed 1.8kg of milk twice daily to 28 (early weaning) or 56 d (late weaning) and a commercial pelleted calf starter from 0 (early) or 28 d (late). Blood was sampled once weekly for 14wk and analyzed for β-hydroxybutyrate and acetoacetate. Plasma was analyzed for glucose and nonesterifid fatty acids. Blood β-hydroxybutyrate increased with increasing grain intake and was greater during wk 0 to 4 and 5 to 8 in calves weaned early than in those weaned late. Blood acetoacetate followed trends similar to β-hydroxybutyrate and averaged 23.8 and 16.1 μM in calves weaned early and late, respectively. Plasma glucose and nonesterifid fatty acids declined with age and were lower during 5 to 8wk in calves weaned early. Data suggest that ketone concentrations resulted from alimentary ketogenesis, which increased rapidly after weaning.

Changes in Plasma Volatile Fatty Acids in Response to Weaning and Feed Intake in Young Calves

Effects of weaning age on plasma VFA were examined using 16 Holstein heifer calves. Animals entered the study at 6±3.5 d of age and were fed 1.8kg milk twice daily to 28 (early weaning) or 56 d (late weaning) and a commercial pelleted calf starter from 0 (early) or 28 (late) d. Blood was sampled once weekly for 14 wk Total blood concentrations of VFA, acetate, propionate, and butyrate were higher in calves weaned early. Difference between treatments was greatest during wk 5 to 8, after early calves had been weaned. Total VFA and acetate were both highly correlated with grain intake (r = .77), whereas propionate (r = .47) and butyrate (r = .56) were less highly correlated. Data indicate that blood VFA responded rapidly to dry feed intake, and adaptation to high grain diets was complete by 1 to 2wk postweaning.

Effects of different weaning strategies on postweaning growth rate, mortality and fertility of Bos indicus cross cattle

Three drafts of Brahman cross calves (phenotypically half to three-quarters Bos indicus) were either early weaned (EW) in April (mean age 5 months) or late weaned (LW) in July (mean age of 8 months). Their postweaning performance on native pastures in the dry tropics of North Queensland was monitored through to 2.5 years of age for females and 3.5 years for males. At late weaning, LW calves of both sexes were significantly (P&lt;0.01) heavier than EW calves. Mean liveweight differences over the 3 drafts were 53.8 kg for males and 54.4 kg for females. From late weaning until final liveweight, EW animals partially compensated in growth and were on average 13.6 kg lighter at 3.5 years for males and 20.3 kg lighter at 2.5 years for females than LW animals. In draft 2, pregnancy rate at 2.5 years favoured LW heifers (P&lt;0.05) by 38% units. Mortalities occurred only in the first dry season postweaning with 0, 5 (11.1%) and 5 (8.9%) deaths from poverty in the EW group in drafts 1 to '3 respectively but none in the LW group. Pooled data across treatment groups showed that older calves at weaning had lower growth rates during the first dry season but still had heavier final liveweights. Age at weaning did not influence subsequent growth rate in the first wet season or males in year 2 or year 3 postweaning.

Performance of crosses among Hereford, Angus and Simmental cattle with different levels of Simmental breeding: IV. Maternal heterosis and calf production by two-year-old dams.

The performance of 264 contemporary 2-yr-old straightbred and crossbred dams during 1978 to 1981 was studied and maternal heterosis was estimated. Dam breed groups were Hereford (HH), Angus-Hereford (AH), 25% Simmental-75% Hereford (1S3H), 50% Simmental-50% Hereford (1S1H) and 75% Simmental-25% Hereford (3S1H). Differences among dam breed groups were nonsignificant for length of gestation, calving difficulty and late milk production but were important (P less than .01) for calf weights (birth, early and late milking periods and weaning), calf average daily gains during various intervals from conception to weaning, early milk production and other calf traits at weaning (height, weight/height and visual condition score). Dam breed group means (HH, AH, 1S3H, 1S1H and 3S1H, respectively) for representative calf traits were .37, .39, .39, .42 and .42 kg/d for estimated average daily gain the last 3 mo of gestation; 33.6, 34.7, 35.7, 37.6 and 37.1 kg for birth weight; 191, 205, 209, 228 and 228 kg for weaning and 7.5, 8.4, 8.3, 9.5 and 10.0 kg for 24-h early milk production. Therefore, 2-yr-old crossbred dams raised calves that were generally larger for the preweaning gain traits than HH dams. Differences among dam breed groups were significant for traits involving reproduction; means (HH, AH, 1S3H, 1S1H and 3S1H, respectively) were .58, .92, .72, .91 and .79 for proportion calving and 105, 179, 126, 182 and 154 kg for actual calf weaning weight per cow exposed to breeding. Estimates of percentage maternal heterosis were 6.3, 12.9, 9.0 and 7.6% for calf weights at birth, 40 d, 130 d and weaning, respectively; 1.8, 5.7 and 5.7% for calf hip height, height/weight and condition score at weaning, respectively; and 43.1 and 34.6% for proportion calving and actual calf weaning weight per cow exposed to breeding. The dominance model explained most (greater than 95%) of the variation observed among dam breed group means for most traits.

Factors affecting postoperative ventilatory support in patients with cardiac cachexia

Factors affecting early v late weaning from ventilatory support after cardiac surgery were retrospectively compared in 15 patients with cardiac cachexia. These patients were divided into two groups based on the duration of postoperative ventilatory support, group I (n = 7) less than two days (22 +/- 8 hours) and group II (n = 8) over three days (140 +/- 125 hours). Findings in 14 randomly selected patients without cardiac cachexia who underwent cardiac valve replacement were also examined. Comparisons were made between the groups in regards to the following parameters: (1) preoperatively: anthropometric, biochemical, and immunologic parameters of nutritional status, hepatic function, cardiothoracic ratio (CTR) on chest x-ray, and data from cardiac catheterization; (2) intraoperatively and postoperatively: anesthetic drugs, duration of surgery, cardiopulmonary bypass (CPB), aortic cross-clamp, and postoperative use of inotropes. The anthropometric measurements, cell-mediated immunity, and hepatic function were significantly decreased in all patients with cachexia, but with no significant differences between the groups. Serum transferrin levels, which increased in patients with cachexia, showed no significant difference between the groups. The levels of serum albumin were significantly lower in cachectic patients than in patients without cachexia; they were significantly higher in group II than in group I. The durations of surgery and CPB were significantly longer in group II, but there was no significant difference in the duration of aortic clamping between the groups. The postoperative use of inotropes was higher in group II. These results indicate that group II patients were nutritionally as well sustained as group I. However, they had less satisfactory cardiac function, and therefore required a longer duration of postoperative ventilatory support.

Weaning in calves: Its effects on social organization

Two experiments were undertaken in order to determine the effects of late weaning on the social behaviour of calves. Control heifers that were still suckled were compared to heifers that were weaned and kept either alone (Experiment 1) or with other familiar cows (Experiment 2) and to heifers whose dams had cloth on the udders to prevent suckling (Experiment 1). Spatial repartition and social encounters were recorded at pasture from dawn to dusk. Weaned heifers gathered more and engaged in more social encounters between them than controls. These alterations were more striking when the heifers were kept alone after weaning and less striking when only suckling was prevented. Moreover, preventing suckling did not alter dam-young relationships (Experiment 1). Nevertheless, when the dams were returned to their young after a total 3-week separation, their attachment to their young seemed to have declined, whereas that of the calves to their dams had not (Experiment 2). It is concluded that the calf remains attached to its dam even after weaning and that the absence of this preferential social partner makes the young animal strengthen its bonds with other partners.

Effects of weaning and supplementation on performance of Brahman cross cows and their progeny

In a 3-year study in the dry tropics, 2 management practices of dry season supplementation of cows and early weaning of calves were concurrently examined as possible techniques for improving reproductive, liveweight and survival performance of Brahman cross cows (phenotypically 1/2 - 3/4 Bos indicus) grazing native pastures. Cows were either supplemented with a drylick mixture of salt, urea and sulfur (DL) commencing in July for 4-6 months; supplemented with a crisis mixture of salt, urea, grain, molasses, meatmeal and monoammonium phosphate (CM) in the latter part of the dry season; or were not supplemented (C). Mating commenced in January, and calves were either early weaned (EW) at the end of mating in April (mean age of 5 months) or late weaned (LW) in July (mean age of 8 months). Supplements and weaning treatments had little effect on cow liveweight, except between early weaning and late weaning when EW cows gained more or lost less weight (mean advantage of 30.8 kg) than LW cows and were heavier (mean advantage of 44.8 kg) than LW cows at late weaning time. Across all years, 1.4, 2.1 and 4.2% of cows in DL, CM and C groups respectively died from malnutrition or required survival feeding; whereas, in the second and third years, mortality rates due to malnutrition were 0.7 and 2.1% in EW and LW groups respectively. Neither supplement nor weaning treatments had any significant effect on lactating cow pregnancy rates, although data pooled across treatments showed that liveweights at various stages pre-mating were correlated with pregnancy rate. Supplementation or weaning treatments did not influence calving date or birth weight, but LW calves grew significantly faster (mean advantage of 0.52 kg/day) between early weaning and late weaning and were significantly heavier (mean advantage of 57.4 kg) at late weaning than EW calves.

EFFECTS OF EARLY WEANING ON CALF GAIN AND COW PERFORMANCE AND INFLUENCE OF BREED, AGE OF DAM AND SEX OF CALF

A study was conducted to determine the effects of early weaning and preconditioning to feedlot on calf gain and the effects of early weaning on cow weight and reproductive performance. A total of 390 cow-calf pairs in 1982 and 460 in 1983, representing four breed, three age-of-dam groups and two-sex-of-calf groups, were randomly assigned to either an early weaned (EW) or a late weaned (LW) group. In the fall of each year, EW calves were weaned 1 mo before LW calves and fed grain (up to 4.8 kg head−1 d−1) and hay during this period. EW calves gained approximately 0.5 kg d−1 less over the 1 mo fall test period than LW calves in 1982 (0.16 vs. 0.75 kg d−1) and 1983 (0.05 vs. 0.58 kg d−1). EW cows gained 0.32 kg d−1 more during this same period than LW cows in 1982 (0.86 vs. 0.54 kg d−1) and lost 0.21 kg d−1 less in 1983 (−0.10 vs. −0.31 kg d−1). These differences in gain did not result in significant weight differences between EW and LW cows entering the winter feeding period in either year. EW and LW cows lost a similar amount of weight over the winter feeding period in 1982–1983 (−0.13 vs. −0.12 kg d−1) and had the same weight after calving in 1983. However, during the winter feeding period of 1983–1984, EW cows lost less weight than LW cows (−0.22 vs. −0.30 kg d−1) and, thus, weighed 27.3 kg more than LW cows after calving in 1984 (468.3 vs. 441.0 kg). Weaning treatment had no effect on pregnancy rate, calf crop percentage or calving interval. Weaning treatment also had no effect on cow weight and gain, calf birth date and weight, calving interval or calf preweaning gain the following year. Interactions between weaning treatment and breed, age of dam or sex of calf were absent for most weight and weight gain parameters and for calving intervals. Calf weights were affected by breed, age of dam and sex of calf while calf gains over the fall test were affected by age of dam. Cow weights were affected by breed and age, calf crop percentage by breed and calving interval by age. Breed, age of cow and sex of calf effects for all other parameters were not significant. Key words: Beef cattle, beef calves, early weaning, preconditioning