The physical state and metabolic status of lambs of different birth rank soon after birth

RNA-Seq reveals miRNA role in thermogenic regulation in brown adipose tissues of goats

BACKGROUND

MicroRNAs (miRNAs) are a family of short non-coding RNA molecules and play important roles in various biological processes. However, knowledge of the expression profiles and function of miRNAs on the regulation of brown adipose tissue (BAT) thermogenesis remains largely unknown.

RESULTS

In this study, we found that brown adipose tissue (BAT) existed within the perirenal fat at 1 day after birth (D1) and transferred into white adipose tissue (WAT) at 30 days after birth (D30) by UCP1 protein expression and immunohistochemistry analysis. After that, we performed RNA sequencing on six libraries of goat BAT and WAT. A total of 238 known miRNAs and 1834 goat novel miRNAs were identified. Moreover, 395 differentially expressed miRNAs including 167 up-regulated and 228 down-regulated miRNAs were obtained in BAT. For the known BAT enriched miRNA, 30 miRNAs were enriched in goat BAT but not in mouse BAT. In addition, miR-433 was enriched in goat BAT but not in mouse BAT. Gain- and loss-of-function experiments reveal that miR-433 reduced the lipid accumulation of brown adipocytes and decreased the expression of BAT marker and mitochondrial related genes. However, miR-433 had no effect on lipid accumulation and thermogenesis in white adipocytes. In addition, miR-433 inhibited the expression of MAPK8 by targeting to the 3'UTR of MAPK8 gene. These data demonstrate that miR-433 acts as a negative regulator in controlling brown adipocytes differentiation and thermogenesis.

CONCLUSION

The present study provides a detailed miRNAs expression landscape in BAT and WAT. Furthermore, we found that miR-433, which was highly expressed on BAT had a negative regulatory function on the thermogenesis and adipogenesis in goat brown adipocytes. This study provides evidence for understanding the role of miRNAs in regulating BAT thermogenesis and energy expenditure in goats.

Long term genetic selection for reproductive success affects neonatal lamb vitality across cold stress conditions

Adverse weather conditions are important contributors to mortality in new-born lambs. Previous studies have shown variation between lambs in their ability to cope with circumstances of cold stress, and genetic selection could be a viable option for improving animal robustness. The Elsenburg Merino flock was divergently selected on number of lambs weaned (NLW). This resulted in divergent responses in reproduction and lamb survival. This study evaluated lamb vitality and mortality of positively selected H-Line relative to the negatively selected L-Line in response to cold stress. Traits included lamb rectal temperature (RT), surface temperature (ST), shiver score (SS), lamb vigor score (LVS), breaths per minute (BPM), mortality to three days of age (M3) and to weaning (TM). Cold stress was described by a chill index derived from daily rainfall, wind speed and ambient temperature, and represented as the mean of the one (CI), two (CI-2) or three (CI-3) days since parturition. Overall, H-Line lambs had a higher neonatal RT and were less likely to succumb than L-Line contemporaries. In a significant (P < 0.05) interaction, the predicted RT of L-Line showed a non-linear decline with increased levels of CI-2, while H-Line lambs better maintained their core temperature. M3 was also affected by a significant interaction between CI-3 and selection line, further suggesting that observed lower mortality rates in the H-Line depends on H-Line lambs' improved ability to cope with stressful environments. Long term selection for NLW in the H-Line led to improvements in both adaptations associated with lower lamb losses. The continued recording of viability traits to produce larger datasets amenable to genetic analysis is recommended, specifically for rectal temperature.

Invited review: impact of specific nutrient interventions during mid-to-late gestation on physiological traits important for survival of multiple-born lambs

To improve production efficiency, the sheep meat industry has increased flock prolificacy. However, multiple-born lambs have lower birth weights, increased mortality and reduced growth rate compared with single-born lambs. Lamb mortality is a major issue for livestock farming globally and solutions are required to increase survival to realise the value of increased flock fecundity. Nutrition during gestation can influence maternal-foetal placental nutrient transfer and thus foetal growth and organ/tissue development, as well as improve postnatal productivity. This review covers the challenges and opportunities associated with increased prolificacy, highlights gaps in our knowledge and identifies some opportunities for how targeted intervention with specific nutrients during mid-to-late pregnancy may influence lamb survival and productivity with a specific focus on pasture-based systems. This time frame was selected as intervention strategies in short-time windows post-pregnancy scanning and before lambing to improve lamb survival in high-risk groups (e.g. triplets) are likely to be the most practical and economically feasible options for pasture-based extensive farming systems.

Physiological differences between twin and single-born lambs and kids during the first month of life

Abstract. The effects of time after birth and of twinning on rectal temperature (RT), heart rate (HR), respiratory rate (RR) and body weight (BW) values were evaluated in five singleton Comisana lambs (three males and two females), five singleton Maltese Kids (three males and two females), four couples of twin Comisana lambs (four males and four females) and four couples of twin Maltese kids (four males and four females) during the first month of life. For all kids and lambs, RT, HR, RR and BW were recorded after 1 and 24 h from birth and every 2 days until the 30th day of life. The application of two-way repeated measures analysis of variance (ANOVA) showed a statistically significant effect of time (P < 0.0001) on RT, HR, RR and BW values in all lambs and kids during the first month of life. Any significant effect of twinning (P > 0.05) on all studied parameters was found in lambs, whereas statistically significant differences in BW, RT and HR values (P < 0.01) were found between twin and singleton kids throughout the first month of life. The results obtained in this study make a contribution to the knowledge of homeostatic, cardiorespiratory and thermoregulatory adaptations occurring in singleton lambs and kids and in twin lambs and kids during the first 30 days of life. Our findings indicate that the BW, RT, HR and RR values, whose homeostasis is still evolving in newborn, should be interpreted dynamically as a function of the period of postnatal adaptation and also of twinning.

Thermogenesis and physiological maturity in neonatal lambs: a unifying concept in lamb survival

Lamb mortality represents reproductive wastage and an animal welfare concern. While lambs are thought to be at a thermogenic advantage following birth in comparison to other species, death from exposure can still be a major contributor to lamb mortality, largely because of the inclement conditions often prevailing at lambing. For this reason, thermogenesis has been studied extensively in neonatal lambs. Heat is produced in the neonatal lamb by shivering and non-shivering thermogenesis. The latter is heat generated by metabolism of brown adipose tissue (BAT) found largely in the thorax and peri-renal areas of the newborn lamb. Brown adipose tissue differs from normal adipose tissue in that it contains densely packed mitochondria, a high cytochrome c content and a vast vascular network. Heat is generated in BAT by uncoupling of the proton conductance mechanism from ATP production, resulting in heat production instead of stored energy. The ability of lambs to resist cooling differs among individuals and this is likely to be due to both genetic and phenotypic factors. The heritability of cold resistance is moderate-to-high and polymorphic gene markers associated with energy homeostasis and cold-related mortality have been identified. Additionally, several aspects of the phenotype of the lamb have been associated with cold resistance. Most relate to properties of the coat, skin and bodyweight, the latter being particularly important, presumably through effects on surface area to volume ratios and subsequent heat loss. The ability of the neonate to achieve the transition from intra- to extra-uterine life has been termed physiological maturity and is associated with the ability to activate appropriate neuro-endocrinological and behavioural changes that are consistent with homeostasis of energy metabolism. Ways to alter physiological maturity of the lamb, such as nutrition, pharmacology and genetic selection, have been identified, and while these show promising results with regards to thermoregulation, a key limitation of their application has been the lack of a repeatable, representative model of neonatal cold stress. An estimation of the non-shivering component potential of a lamb’s ability to thermoregulate can be derived from norepinephrine challenges, but more useful models of real-world cold stress are climate chambers or controlled water bath tests. Further use of repeatable test models such as these with appropriate neuroendocrine and metabolic metrics will identify key components and markers of physiological maturity associated with lamb thermogenesis and survival.

Supplementation of Merino ewes with cholecalciferol in late pregnancy improves the vitamin D status of ewes and lambs at birth but is not correlated with an improvement in immune function in lambs

Functional deficiencies of the immune system are known to predispose human and animal neonates to death. Thus, immune competency may be a significant factor influencing the mortality of lambs. Vitamin D has been recognised to improve immune function and is transferred across the placenta. This study tested the hypotheses that (1) supplementation of Merino ewes with cholecalciferol during late pregnancy will increase the concentrations of vitamin D in the ewe and lamb at birth and (2) supplementation of Merino ewes with cholecalciferol during late pregnancy is correlated with an increase in innate phagocytic and adaptive antibody immune responses in the lamb. Merino ewes (n = 53) were injected intramuscularly with 1 × 106 IU cholecalciferol at Days 113 and 141 of pregnancy. A control group (n = 58) consisted of ewes receiving no additional nutritional treatments. The vitamin D status of ewes and lambs was assessed up until 1 month post-lambing. Lamb immune function was assessed by analysing the functional capacity of phagocytes, and the plasma IgG and anti-tetanus-toxoid antibody concentrations between birth and weaning. Maternal supplementation with cholecalciferol increased the plasma 25(OH)D concentrations of both ewes (137 vs 79 nmol/L; P < 0.001) and lambs (49 vs 24 nmol/L; P < 0.001) at birth compared with the controls. Supplementation with cholecalciferol had no significant effect on the phagocytic capacity of monocytes or polymorphonuclear leukocytes, the concentration of IgG in the colostrum or plasma of lambs, or the vaccine-specific antibody response against tetanus toxoid. Overall, the results support our first hypothesis, but suggest that maternal supplementation with 1 × 106 IU cholecalciferol does not improve innate, passive or adaptive immune function in lambs.

Physiological changes in the peri-partum period and colostral IgG transfer in prolific D'man sheep: effects of parity and litter size

The aim of this work was to assess maternal and neonatal changes in plasma proteins, glucose and cortisol and to quantify the colostral immunoglobulin G (IgG) transfer in the peri-partum period in D'man sheep, a prolific breed, taking into account the parity of the ewe. The concentrations of proteins and glucose were high in the ewes on day 7 and at lambing before decreasing. Likewise, cortisol plasma concentration was maximal during the 6 h following lambing and dropped at 12 h. Protein and glucose concentrations were low in lambs at 1 h of birth after which they increased. By contrast, cortisol level was the highest during the first 12 h of birth and then decreased. The colostral IgG level was high at lambing and dropped by over 87 % from 1 to 48 h post-partum. In the newborn, the plasma IgG concentration was lowest at birth and increased rapidly during the first 24 h of birth. Parity influenced maternal physiology with multiparous ewes having the lowest concentrations of proteins, glucose, IgG and cortisol, but the highest colostrum IgG level. Accordingly, lambs born from primiparous ewes had lower protein, glucose and plasma IgG concentrations than lambs born from multiparous ewes. The main outcome of this study was that lambs born from primiparous ewes are characterized by the lowest physiological indices and this may influence their survival chance.

Dinâmica pré e pós-colostral de parâmetros bioquímicos em cordeiros

O objetivo deste estudo foi verificar a influência do colostro nos parâmetros bioquímicos séricos em cordeiros recém-nascidos. Foram colhidas amostras sanguíneas de 28 cordeiros, determinando-se os indicadores proteicos, energéticos, de função renal, bilirrubinas e as enzimas aspartato aminotransferase (AST), gama-glutamiltransferase (GGT) e creatina quinase (CK), nos momentos pré e pós-colostro. Os dados foram analisados comparando-se a variabilidade dos parâmetros entre os dois momentos. Houve elevação (P<0,001) das concentrações de proteínas totais, em resposta ao forte aumento (P<0,01) dos teores de globulinas totais e ao leve decréscimo (P<0,05) da concentração de albumina, após a ingestão colostral. Também foram observados maiores valores de bilirrubinas total e direta (P<0,001), e variação dos metabólitos renais, com elevação dos níveis de ureia (P<0,01) concomitante à redução dos valores de creatinina (P<0,001), no momento pós-colostro. Houve aumento (P<0,001) da glicemia, de colesterol total e triglicerídeos, bem como das atividades enzimáticas (P<0,001) de AST e GGT, entre os momentos avaliados. Conclui-se que a dinâmica do perfil bioquímico em cordeiros recém-nascidos sofre o efeito da ingestão de colostro e da adaptação das funções fisiológicas à vida extra-uterina. Os valores dos parâmetros variam marcadamente no período pós-natal, sendo recomendável a utilização de valores de referência próprios para esta fase.

Intensive sheep and beef production from pasture--a New Zealand perspective of concerns, opportunities and challenges

This paper details current production trends for sheep and beef cattle production in New Zealand and gives some insight into the opportunities for improvement based on New Zealand research at Massey University. Further it outlines some of the challenges the industries face in the near future. The New Zealand climate favours pasture growth and this is the key to sheep and beef cattle production with over 95% of the diet being grazed pasture or crop. Exports are the focus of the industry with 95% of sheep meat and wool, and 80% of beef exported. There have been considerable gains in production over the last 20 years but there still remains a huge opportunity for further intensification through breeding sheep at an earlier age, increasing the weight of lambs weaned per ewe per year and improving beef production systems. These improvements need to occur within a framework of minimal environmental footprint and produce products that are in demand in the high end international markets.

Concentração de lactato sérico em ovelhas e cordeiros mestiços (1/2 Suffolk) nascidos em eutocia

O objetivo do estudo foi avaliar a concentração de lactato sanguíneo venoso em ovelhas e em cordeiros neonatos imediatamente após o parto eutócico. Foram utilizadas 14 ovelhas, sendo nove da raça Suffolk e quatro mestiças e 20 cordeiros neonatos sadios (machos e fêmeas). O efeito do sexo, da raça e do número de cordeiros por parto foi investigado, bem como a possível correlação entre a concentração de lactato materno e neonatal. Não houve diferença entre machos e fêmeas, em relação à raça (Suffolk e mestiços), contudo a concentração de lactato foi mais elevada em cordeiros gêmeos ou trigêmeos quando comparado a cordeiros uníparos. Houve correlação positiva entre a concentração materna e a neonatal, sendo que quanto maior a concentração de lactato materno, maior a concentração no cordeiro imediatamente após o parto eutócico. Os resultados do presente estudo fornecem um subsídio por meio do qual se podem comparar os níveis de lactato sanguíneo em cordeiros em estado crítico.

Does the physiological status of lambs within a twin- and triplet-born litter differ during the first 12 hours of life?

This study examined the physical and physiological differences from birth until 12 h of age within twin- and triplet-born litters. In 2005 and 2006, the parturition of 75 twin- and 62 triplet-bearing Romney ewes were observed. After parturition lamb blood samples were taken within 5 min of birth and rectal temperature was measured within 5 min of birth and at 1, 3, 6 and 12 h post-birth. Lamb birth weight, crown–rump length and thoracic-girth circumference were measured at 3 h of age. Lamb birth weight, plasma glucose, fructose, lactate, thyroxine and tri-iodothyronine did not differ (P > 0.05) between the heaviest-twin-born, lightest-twin-born and heaviest-triplet-born lamb. The lightest-triplet-born lambs, however, had lighter (P < 0.001) birthweights, greater (P < 0.001) surface-area-to-birth weight ratio, lower (P < 0.05) rectal temperatures, greater (P < 0.1) lactate concentrations and lower (P < 0.1) plasma thyroid hormone concentrations. These characteristics are known to have a negative impact on the ability of the lamb to maintain its body temperature after birth and may therefore provide some evidence as to why triplet-born lambs display a greater mortality rate than twin-born lambs, and why the lightest-triplet-born lambs have the greatest mortality rate within a litter.

Effect of birthweight on survival in triplet-born lambs

Lambing percentage is the main contributor to higher profit on New Zealand sheep farms and has increased from 98% in 1960 to 124% in 2006. As ewe litter size increases so does the proportion of triplet-born lambs and consequently preweaning mortality rate. The purpose of this study was to investigate the effect of birthweight (BWT) on survival in triplet-born lambs within and among litters. Data from a total of 594 triplet crossbreed lambs born to mixed-age ewes was analysed. For the statistical analysis, the lambs were allocated according to their BWT, and within the litter were then allocated to three BWT groups (light, medium and heavy). The following parameters were calculated: total litter BWT (TBWT), percentage of TBWT for each lamb (PBWT = BWT/TBWT), coefficient of variation for BWT within litter and lamb average daily gain from birth to weaning. The mortality rate for the light, medium and heavy lambs was 56, 40 and 28%, respectively, and consequently the lightest lamb in a litter was 3.2 times more likely to die than the heaviest lamb. In the light lamb group, as BWT increased mortality decreased (P = 0.006), for medium lambs BWT did not influence mortality (P = 0.88) and in the heavy group there was a trend of increased BWT associated with increased mortality (P = 0.10). The negative relationship between lamb mortality and PBWT was identical in the three BWT groups (P < 0.0001). The effect of BWT on lamb mortality became non-significant when PBWT was fitted in the same model. This means that, in triplet-born lambs, mortality is not influenced by the BWT of the lamb itself, but by the BWT of its littermates. It can be calculated that a 4-kg lamb has a 24% chance of surviving in a litter of 16 kg, a 60% chance in a litter of 12 kg and an 87% chance of surviving in a litter of 8 kg. It is concluded that reducing the variation in BWT within a litter, or specifically managing the lightest lamb at birth, will increase the competitive ability for survival of each lamb and, therefore, decrease overall mortality and further improve farm profitability.