Beef cattle producers continuously search for nutritional management options that provide flexibility to production scenarios. Due to its positive effects on maternal productivity, early weaning is one such alternative strategy that has received considerable interest. To better understand the effects of early weaning on calf productivity, an extensive literature review and three experiments were conducted to evaluate the effects of early weaning on finishing feed efficiency, marbling development and retail product quality of beef steers. In experiment I, which included 90 Angus-sired steers from four calving seasons, early weaning followed by a short ad libitum concentrate-feeding and pasture-backgrounding phase reduced finishing residual feed intake (RFI) by 7 % (P < 0.0001) and increased carcass marbling score (MS) by 10 % (P < 0.01) when compared to conventionally weaned (CW) contemporaries. Similar effects were observed in experiment II, which included 28 Angus and Simmental-sired steers, as early weaning reduced RFI (P < 0.01) and increased carcass MS (P < 0.01). Lung mass of early weaned (EW) steers was greater than their CW contemporaries (P < 0.05), and was inversely related to RFI (R2 = 0.17; P < 0.05). Finishing treatments in this experiment included a high corn ration and an alternative low corn ration that iso-calorically replaced 50 % of the DM from corn with dried corn gluten feed. Iso-caloric replacement of corn reduced lung mass (P < 0.01), and when combined with the observed increase of EW steers suggests that lung development is affected by dietary energy type at various stages of growth. In experiment III, objective analyses of ribeye steaks obtained from steers included in experiment two revealed that early weaning increased cross-sectional muscle fiber area by 28 % (P < 0.001) and tended to increase (P = 0.08) Warner-Bratzler shear force by 36 %. Nonetheless, these effects were not great enough to alter un-trained consumer perception of texture (P ≥ 0.65), juiciness (P ≥ 0.55), flavor (P ≥ 0.25) or overall acceptability (P ≥ 0.34). Collectively, these results indicate that early weaning enhances finishing feed efficiency and carcass marbling without affecting un-trained consumer sensory perception. / Ph. D.

A dieta pode regular a proliferação e diferenciação no epitélio gástrico de ratos durante o período pós-natal. Avaliamos o efeito tardio do desmame precoce na massa corpórea, proliferação (imunomarcação para Ki-67) e diferenciação celular (immunoblot de Mist 1 e pepsinogênio C) aos 15, 18, 30 e 60 dias. Ratos Wistar foram divididos nos grupos: desmame precoce (DP) aos 15 dias e desmamados aos 21 dias (A). Os resultados mostraram: massa corpórea aos 18 (p<0,01) e 21 (p<0,05) dias no grupo DP menor do que no A. Aos 60 dias, os valores se equiparam, porém há diferença entre machos e fêmeas. O índice de proliferação, a espessura da mucosa e profundidade da glândula foram superiores aos 18 dias no grupo DP (p<0,05), havendo resultado oposto aos 30 dias e nenhuma resposta aos 60 dias; houve variação no conteúdo de Mist 1 (p<0,05) e pepsinogênio C (p<0,01) nos animais DP aos 18 dias. Assim, O DP alterou o ganho de peso corporal e crescimento do estômago logo após o início da ingesta de ração, e tal reposta foi compensada na idade adulta. / Diet can regulate proliferation and differentiation in gastric epithelium of rats during the postnatal period. We evaluated the late effects of early weaning on body mass, cell proliferation (Ki-67 immunolabeling) and differentiation (Mist 1 and pepsinogen C by immunoblot) at 15, 18, 30 and 60 days. Wistar rats were divided into groups: early-weaned (EW) at 15 days, and suckling and weaned at 21 days (S). The results showed that: at 18 (p<0,01) and 21 (p<0,05) days, body mass was lower in EW than in S. At 60 days, values were similar between S and EW, however we registered a difference between males and females. The proliferation index, mucosal thickness and gland depth were higher in EW (vs. S) at 18 days (p<0,05), being reversed at 30 days, whereas no change detected at 60 days. We found a variation in Mist 1 (p<0,05) and pepsinogen C (p<0,01) at 18 days. Thus, EW altered body weight gain and stomach growth soon after its onset, and part of responses were compensated in adulthood.

The small intestinal mucosal apical hydrolases are essential to the terminal digestion of enteral nutrients such as carbohydrates, proteins, fats and phosphates, and non-immune defense. Weaning results in the complete replacement of fetal enterocytes with mature adult-type enterocytes and is typified by mucosal atrophy, crypt hyperplasia and compromised digestive and defensive functions. Given these severe physiological changes, we hypothesize that the major apical small intestinal hydrolases will be differentially expressed, allowing for reprogramming and adaptation, in the early-weaned piglet. Therefore, the objectives of this study were to examine changes in the digestive capacity, the catalytic kinetics, and abundances of protein and mRNA of the small intestinal hydrolases, including alkaline phosphatase (IAP), lactase phlorizin hydrolase (LPH), sucrase-isomaltase (SI), maltase-glucoamylase (MGA) and aminopeptidase N (APN), in the early-weaned pigs in comparison with suckling pigs. A total of 20 Yorkshire piglets, 10 suckling (SU) and 10 early-weaned (WN) with an average initial body weight of about 3 kg at the age of 10 d, were used in this study. Weanling piglets were fed a corn and soybean meal-based diet for 12 d. Proximal jejunal samples from both groups were collected. Hydrolase kinetic experiments were conducted using the substrates of lactose (0-75 mM), sucrose (0-75 mM), maltose (0-75 mM), amylose (0-100 mM), p-nitrophenyl phosphate (0-10 mM), and L-alanine-p-nitroanilide hydrochloride (0-16 mM). Abundances of the target gene hydrolase protein and mRNA were analyzed by Western blotting and quantitative real time reverse transcription- polymerase chain reaction (RT-PCR), respectively, using ß-actin as a control. Results from this study demonstrate that early weaning down-regulated (P < 0.05) the digestive capacity and expression of LPH while simultaneously increasing (P < 0.05) the digestive capacity and expression of SI and MGA. Furthermore, weaning decreased (P < 0.05) the digestive capacity and expression of APN and IAP by 35 and 50%, respectively. Thus, the early-weaning process differentially affected the expression of the apical membrane-bound hydrolases of the small intestine. The down-regulation of IAP highlights the reduced microbial detoxifying capacity of the newly weaned piglet and provides some insight into the cascade of immune related events that occur during the post-weaning transition period. The reduced expression of LPH and the simultaneous up-regulation of SI, maltase, and MGA indicate the unique nature of the small intestinal reprogramming that occurs during weaning. These results imply that the early weaning events help the small intestine adapt to the transition to starch digestion. Meanwhile, the down-regulation of the APN expression may be partially responsible for the reduced efficiency of whole body protein utilization, and the pervasive localized immune responses observed in the small intestine of early-weaned piglets. / Natural Sciences and Engineering Research Council (NSERC) of Canada Discovery Program, and the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA)-the University of Guelph Partnership Research Program.

Master of Science / Department of Animal Sciences and Industry / Michael E. Dikeman / Vitamin A (VA) restriction during finishing has been shown to increase marbling in cattle. However, little work has been done to look at the effects that VA restriction might have on color shelf-life and sensory traits of beef. This study involved 48 calves either early-weaned at 137 + 26 d or traditionally-weaned at 199 + 26 d and supplemented with either 15,400 IU/kg dry matter of VA or restricted to no supplemental VA during the finishing phase. Cattle were harvested in two groups, and carcass data were obtained after chilling. Strip loins and shoulder clods were retrieved, vacuum packaged, and cut into steaks after 14 d of aging. Visual and instrumental color scores for 7 d of retail display, thiobarbituric acid reactive substances (TBARS) values, trained sensory panel scores, and Warner-Bratzler shear force (WBSF) values were obtained. The only differences associated with weaning group were that L* values were lower (P < 0.05) on d 4 to 6 for Triceps brachii (TB) steaks from traditionally-weaned calves restricted in VA than early-weaned calves supplemented with high VA. Both Longissimus lumborum (LL) and TB steaks from calves supplemented with high VA had darker, more tan (P < 0.05) color scores after 4 d of display in PVC packaging than steaks from calves restricted in VA. Also, a*, b* and saturation index values were lower (P < 0.05) in LL steaks for the high VA treatment than those from the no supplemental VA treatment. There was less lipid oxidation (P < 0.05), as reported by TBARS, in both muscles from calves restricted in VA than muscles from calves supplemented with high VA. No treatment effects were found for WBSF values for either muscle, and no differences existed in sensory panel traits of the TB steaks. Sensory panel scores were less desirable (P < 0.05) for myofibrillar tenderness and connective tissue amount in LL steaks from calves fed high VA than steaks from calves restricted in VA. Dietary VA restriction during finishing has potential to increase color shelf-life and reduce lipid oxidation, with no negative effects on cooked meat sensory attributes.

The goal of a cow-calf producer is to produce a calf each year per cow. Research suggests that first year heifers struggle breeding back with their second calf because of the adjustments to new range/main herd conditions and the partitioning of nutrients between gaining weight, milk production, and gestation. This study was conducted at the V-V ranch at the University of Arizona for five years and looked at the effects on young cows when calves were weaned from first year heifers at 80 days rather than 205 days. Early weaning allows for gestational benefits because they are given the opportunity to adapt to herd conditions by applying feed resources to the in utero fetus and their own body condition rather than lactation. All first year heifers were included over three years, and were randomly assigned to two groups, normal weaning (NW) or early weaning (EW). This resulted in 122 heifers in the group whose calves were EW and 119 heifers in the group whose calves were NW. Heifers that were in the EW group bred back at a 27% higher rate in their second year, and had 15% greater longevity in the herd. Calves that were in utero when the nursing calves were early weaned were 16.4 kg heavier at weaning. Part of this was due to the age of the calf and part to gestational health. Early weaning was an effective strategy for improving reproductive performance of first year heifers as well as their survival rate in the herd to 5 years of age. It also resulted in improved performance for their in utero calves.

Breastfeeding offers significant benefits to the breastfed infant as well as the breastfeeding woman. The World Health Organization now recommends exclusive breastfeeding until six months, followed by supplementation and continued breastfeeding to two years or more. Around the world, public health programs endeavour to promote breastfeeding through educational programs. In Brazil, such programming is widespread, and yet less than 30% of women in São Paulo breastfeeding exclusively even to four months post-partum. This study uses a qualitative-quantitative bio-experiential approach to explore the way that stressful experiences and circumstances in the lives of low-income women from the Eastern Zone of São Paulo, Brazil, influence their decision to wean or supplement their infant before 12 weeks post-partum. Sixty-five first-time mothers participated in a 12-week longitudinal study of life stressors and breastfeeding practice. Participants were asked to complete one pre-partum and six post-partum interviews. Narrative and biological data were collected from each participant at each interview. Statistical analysis revealed that among these participants the breastfeeding hormone oxytocin did not mediate breastfeeding duration. Oxytocin appeared to act as a biomarker of stressful experience, while Epstein-Barr Virus antibody titre, a commonly used biological measure of psychosocial stress, did not. Unplanned pregnancy, older age and higher mean oxytocin level were statistically associated with weaned outcome at 12 weeks. Unplanned pregnancy, older age, higher mean oxytocin level, higher mean satisfaction score regarding financial situation and lower mean satisfaction score regarding interpersonal factors were associated with decreased duration of any breastfeeding. Unplanned pregnancy, older age and lower mean satisfaction score regarding interpersonal factors were associated with decreased duration of exclusive breastfeeding. Ethnographic analysis revealed that the effect of unplanned pregnancy may be connected to the discourse of the self-sacrificial, child-centric “good mother.” Exclusive breastfeeding was seen as a hallmark of this idealised maternal type. Single women with unplanned pregnancies expressed a great deal of ambivalence towards their own maternity and toward the somewhat unobtainable good mother ideal, especially with relation to the physical and psychological challenges breastfeeding. Women’s ambivalence appeared to influence their decisions to supplement or wean their infants by or before 12 weeks post-partum.

No description available.

Investigamos a distribuição de ghrelina e de seu receptor (GHS-R) na mucosa gástrica de ratos durante a terceira semana de vida pós-natal e avaliamos o efeito do desmame precoce sobre estas moléculas. Estudamos também a participação da ghrelina no controle da proliferação celular do epitélio gástrico, e para tanto utilizamos a administração de um antagonista. Detectamos o aumento do número de células imunomarcadas para ghrelina nos animais desmamados precocemente e observamos que nem a expressão de GHS-R nem a concentração proteica deste receptor foram alteradas pela mudança da dieta. O uso do antagonista [D-Lys-3]-GHRP-6 resultou na diminuição do índice de síntese de DNA no epitélio gástrico. Concluímos que a ghrelina e o GHS-R estão distribuídos no estômago durante a terceira semana de vida pós-natal e que o desmame precoce aumenta os níveis de ghrelina no epitélio gástrico, sem comprometer seu receptor. Por fim, sugerimos que esta modulação pode estar envolvida no controle da proliferação celular que é fundamental para o desenvolvimento do estômago. / In the present study, we investigated the distribution of ghrelin and growth hormone secretagogue receptor (GHS-R) in the rat gastric mucosa during the third postnatal week, and evaluated the effects of early weaning on these molecules. In addition, we studied whether ghrelin is part of cell proliferation control in gastric epithelium, and to that we used an antagonist. We detected an increase of ghrelin immunolabelled cells in animals submitted to early weaning and observed that GHS-R expression and protein levels of this receptor were not altered by dietary change. The antagonist [D-Lys-3]-GHRP-6 reduced DNA synthesis index. We concluded that ghrelin and GHS-R are distributed in the gastric mucosa during the third postnatal week and that early weaning increases hormone levels in the gastric epithelium, without changing its receptor. We can suggest that such modulation might be involved in the control of cell proliferation, which is essential for stomach development.

O objetivo do experimento I foi avaliar a interação entre dois ganhos médios diários [GMD - fator nutricional (ganho elevado GA = 0,700 e ganho baixo GB = 0,300 Kg/dia)] e a diferença esperada da progênie (DEP para idade ao primeiro parto - fator genético) na puberdade de novilhas Nelore. Foram utilizadas 58 novilhas desmamadas com 8 meses de idade, filhas de 4 touros [2 precoces (P) e 2 tardios (T)], formando um esquema fatorial 2 x 2, no qual o fator 1 foi o GMD e o fator 2 foi a DEP do touro, constituindo assim quatro tratamentos: Touro precoce com GMD elevado (PGA), touro precoce com GMD baixo (PGB), touro tardio com GMD elevado (TGA), touro tardio com GMD baixo (TGB). Houve efeito dos tratamentos na porcentagem de novilhas púberes durante o experimento (PGA e PGB = 100%; TGA = 83% até 27 meses de idade; TGB = 38% até 3 anos de idade). As novilhas do PGA apresentaram a menor (P = 0,0001) idade na puberdade (18 &#177; 1 meses). Contudo, a nutrição atrasou a puberdade em cerca de 10 meses nas novilhas filhas de touros precoces e tardios (PGA = 18 &#177; 1 vs. PGB = 29 &#177; 1 meses; TGA = 24 &#177; 1 vs. TGB = 34 &#177; 1 meses). Assim podemos concluir que a DEP para IPP foi o fator necessário para o adiantamento da idade a puberdade. No entanto, o GMD foi um fator limitante para o aparecimento da puberdade. O objetivo do experimento II foi avaliar o efeito do imprinting metabólico dos 3 aos 7 meses de idade na puberdade em novilhas cruzadas (Angus x Nelore). Os tratamentos foram arranjados em esquema fatorial 2 x 2, no qual o fator 1 foi GMD elevado e médio dos 3 aos 7 meses de idade (fase 1) e o fator 2 foi GMD elevado e médio dos 7 meses de idade até a puberdade (fase 2). Formando os seguintes tratamentos: CAA Novilhas cruzadas submetidas ao GMD elevado nas fases 1 e 2; CAM - GMD elevado na fase 1 e GMD médio na fase 2; CMA- GMD médio na fase1 e GMD elevado na fase 2; CMM GMD médio nas fases 1 e 2. O GMD médio foi atingido pela restrição do consumo de matéria seca (CMS) no GMD médio. As novilhas dos tratamentos CAA, CAM e CMA apresentaram puberdade na mesma idade (cerca de 12 meses). As novilhas cruzadas submetidas ao GMD elevado na fase 2 foram mais pesadas (P = 0,0379) na puberdade do que novilhas submetidas ao baixo GMD. O GMD elevado dos 3 aos 7 meses de idade não impactou na puberdade das novilhas cruzadas. O objetivo e a metodologia do experimento III foram semelhantes ao experimento II, no entanto foram utilizadas novilhas Nelore (N) ao invés de cruzadas e o experimento terminou aos 19 meses de idade. O tratamento NAA (84%) induziu maior (P = 0,0145) proporção de novilhas púberes do que o NMM (23%), mas não houve diferença na taxa de puberdade entre os tratamentos NAM (60%) e NMA (50%). Além disso, o comportamento das curvas de puberdade dos tratamentos NAM e NMA foram semelhantes, sendo assim não houve efeito de imprinting metabólico nas novilhas Nelore. O GMD elevado dos 3 aos 19 meses idade aumentou a porcentagem de novilhas Nelore púberes aos 19 meses de idade / The objective of experiment I was to evaluate the interaction between two average daily gain (ADG nutritional factor (high gain HG = 0,700 and low gain LG = 0,300 kg/day)] and expected progeny differences (EPD to age at first calving; genetic factor) on puberty attainment of Nellore heifers. Fifth eight heifers weaned at 8 months of age and daughters of 4 sires [2 precocious (P) and 2 later (L)]. A factorial design 2 x 2 was used, where the factor 1 was the ADG and the factor 2 was the EPD of sire, resulting in four treatments: Precocious sire with HG (PHG), precocious sire with LG (PLG), later sire with HG (LHG) and later sire with LG (LLG). There was effect of treatment in the percentage of pubertal heifers (PHG and PLG = 100%; LHG = 83% until 27 month of age; LLG = 38% until 3 years old). Heifers from the PHG treatment were the youngest (P = 0,0001) (18 months of age). However, the nutritional factor delayed puberty achievement by approximately 10 months the age at puberty in precocious and later heifers (PHG = 18 &#177; 1 vs. PLG = 29 &#177; 1 months; LHG = 24 &#177; 1 vs. LLG = 34 &#177; 1 months of age). The EPD to age at first calving was the main factor affecting the age at puberty. However, the ADG was limiting to puberty onset. The objective of experiment II was to evaluate the effect of metabolic imprinting from 3 to 7 months of age on puberty attainment of crossbreed heifers (Angus x Nellore). The treatments were arranged in 2 x 2 factorial design, where the factor 1 was high (H) and medium (M) ADG from 3 to 7 months of age (phase 1) and the factor 2 was high and medium ADG from 7 months of age to puberty onset (phase 2), resulting in the following treatments: CHH crossbreed heifers submitted to high ADG in both phases of experiment; CHM high ADG in phase 1 and medium ADG in phase 2; CMH medium ADG in phase 1 and high ADG in phase 2; CMM Medium ADG in both phases. The medium ADG were targeted by restricting of dry mater intake (DMI) in medium ADG. Crossbreed heifers of treatments CHH, CHM, CMH showed the same age at puberty, about 12 months. Heifers submitted to high ADG on phase 2 were heavier (P = 0,0379) at puberty than heifers submitted to low ADG. The high ADG from 3 to 7 months did not affect puberty onset in crossbreed heifers. The objective and methodology used in experiment III was the same of used in experiment II. However, Nellore heifers (N) were used instead of crossbreed heifers and the experimental period ended at 19 months of age. The NHH treatment (84%) induced higher (P = 0,0145) percentage of pubertal heifers than NMM (23%), but there was not difference in puberty rate between NHM (60%) and NMH (50%) treatments. Furthermore, the comportment of curves of puberty of treatments NHM and NMH were similar, thus there was not effect of metabolic imprinting in Nellore heifers. The high ADG from 3 to 19 months of age increased the percentage of pubertal Nellore heifers at 19 months of age

Na mucosa gástrica, cinco tipos compõe o epitélio gástrico: mucosas superficiais, parietais (CP), mucosas do colo (CMC), endócrinas e zimogênicas (CZ). As CMC originam as células CZ por transdiferenciação e a população de CP é importante para que o processo ocorra.Durante a transdiferenciação observamos células com características de CMCs e CZs, denominadas células em transição (CT) que ocupam o segmento entre o colo e a base da glândula. Essa transição entre células e a presença de CP são essenciais para a homeostase da base da glândula. Porém, estudos mostram que alterações no padrão alimentar influenciam a organização do epitélio gástrico de ratos, e o desmame precoce (DP) modifica a dinâmica de proliferação, migração e maturação das células. Nosso objetivo foi avaliar os efeitos imediatos do DP sobre as populações de CMC, CZ, CT e CP, e investigar se tais efeitos são mantidos até a vida adulta. Para isso, ratos Wistar (CEUA ICB USP 18/2015) foram divididos em dois grupos: amamentado controle (A) (permaneceram com a mãe até 21 dias), e DP (separados das mães aos 15 dias). O estômago foi coletado aos 18, 30 e 60 dias de vida pósnatal. Em cortes histológicos, verificamos que o índice de CP não foi alterado pelo DP, porém a distribuição dessa célula na glândula foi modificada aos 18 e 30 dias. Sob microscopia de fluorescência e confocal, observamos que o DP aumentou a população de CMC (GSIIFITC+) aos 18 dias (A vs DP; P<0,01), e de CZ (Mist1-Cy3+) aos 18 e 60 dias (A vs DP; P<0,05). O número de CT/campo (GSII-FITC+Mist1-Cy3) não se alterou após o DP, evidenciando que o segmento de transição entre o colo e a base da glândula representa um importante controle de tamanho populacional. Para avaliar o comportamento de CT em relação ao seu destino (CZ) e sua origem (CMC), analisamos o índice de CT sobre essas populações. Sobre o destino, devido à ausência de resposta no número de CT/campo e ao aumento de CZ nos animais DP, o índice CT/CZs variou aos 18 e 30 dias. No entanto, o índice de CT/CMC (origem) não foi alterado pelos tratamentos nas diferentes idades. Sob microscopia eletrônica de transmissão, avaliamos as características ultraestruturais das CMC, CT e CZ aos 18 dias, e observamos principalmente as organelas envolvidas na reorganização das células durante a transdiferenciação. Nosso estudo mostrou que o desmame precoce acelera a diferenciação celular e muda a distribuição de células mucosas do colo e zimogênicas na glândula gástrica, porém esse processo ocorre com preservação do tamanho compartimento de transição e do número de células parietais. Assim, podemos sugerir que o desmame precoce aumenta a população de células zimogênicas por meio de uma passagem mais rápida entre a região do colo e da base, na presença de células parietais, e esse mecanismo seria acionado logo após a transição da dieta, podendo manter-se ativo até a vida adulta. / Five epithelial cell types are found in the gastric mucosa: surface mucous, parietal (PC), mucous neck (MNC), endocrine, and zymogenic (ZC). The MNC originates ZC through transdifferentiation, and the presence of PC is important for the process. During transdifferentiation, we observe cells that present characteristics from MNC and ZC that are identified as transition cells (TC). They occupy the area between the neck and base of the gastric gland. The transition between these cells and the presence PC are essential for homeostasis at the base of the gland. However, studies show that changes in dietary pattern influence the organization of rat gastric epithelium, and early weaning (EW) modifies the proliferation, migration and maturation dynamics of these cells. Our aim was to evaluate the immediate effects of EW on the populations of MNC, ZC, TC and PC, and to investigate if such effects are maintained until adult life. To that, Wistar rats (CEUA ICB USP 18/2015) were divided into two groups: suckling control (S) (pups remained with the mother until 21 days), and EW (pups were separated from mother at 15 days). The stomach was collected at 18, 30 and 60 postnatal days. After analyses of histological sections, we verified that PC indices were not altered by EW, but the distribution of this cell was modified at the 18 and 30 days. By fluorescence and confocal microscopy, we determined that EW increased MNC population at 18 days (A vs PD, P <0.01), and ZC at 18 and 60 day (A vs DP; P <0.05). TC number/field did not change after EW, indicating that the transition between neck and gland base is under an important population control. In order to evaluate the behavior of TC regarding its final differentiation (ZC) and origin (MNC), we calculated TC index on these populations. In relation to ZC, we found a variation in TC index at 18 and 30 days, specially because TC number did not change, whereas ZC population increased. However, the TC index on GSII + cells (origin) was not altered by treatments throughout growth and ageing. Finally, under electron microscopy, we studied the ultra structure of MNC, TC and ZC and observed the reorganization of secretory apparatus during transdifferentiation at 18 days. Thus, we can suggest that EW increases ZC population through a rapid traffic through transition compartment between neck and base, in the presence of parietal cells, and such mechanism would be triggered soon after dietary transition and be kept activated until adult life.