Isolation of Aerobic Bacterial Species Associated with Palpable Udder Defects in Non-Dairy Ewes.

The objectives of these studies were to identify associations between udder half defects (hard or lump) and bacteria isolated from milk or mammary tissue swabs, to compare with samples from normal udder halves at different physiological time points and to compare bacterial species isolated via milk and swabs of mammary tissue from within the same udder halves. A total of 1054 samples were aseptically collected from each udder half of 199 non-dairy breed (Romney) ewes from three different studies (Study A, n = 77; Study B, n = 74; and Study C, n = 48). Conventional bacterial culture and MALDI-ToF mass spectrometry were used for bacterial identification. Of the 225 samples from which bacteria were isolated, Mannheimia haemolytica and Streptococcus uberis were the dominantly identified species from defective udder halves, whereas coagulase-negative staphylococcus (CNS) species, mostly Staphylococcus simulans and Staphylococcus chromogenes, were more frequently isolated from normal udder halves. The ongoing presence of bacterial species over time was variable, although less frequently identified species showed less stability over time. A very high agreement (91.5%) of bacterial species identified was observed between the mammary tissue swab and udder half milk samples during post-weaning. In summary, palpable udder half defects were associated with bacterial positivity, and the ongoing presence of the bacteria over time was dependent on the species involved. Hence, culling ewes with palpable udder half defects that had more stable bacterial species could contribute to reducing the recurrence of palpable defects or mastitis.

Assessment of Changes in Udder Half Defects over Time in Non-Dairy Ewes.

A total of 1039 non-dairy breed (Romney) ewes were enrolled in two studies to assess the changes in udder half defect status (hard, lump, or normal) over time and to predict the risk of future udder half defect occurrence. In the first study (study A), udder halves of 991 ewes were assessed utilizing a standardized udder palpation method and scored four times a year, for two successive years (pre-mating, pre-lambing, docking, and weaning). The second study (study B) assessed the udder halves at pre-mating, and at six weekly intervals in the first six weeks of lactation in 46 ewes that had defective and normal udder halves. Udder half defect change over time was visualized via lasagna plots, and multinomial logistic regression was used to predict the risk or probability of udder half defect occurrence. In the first study, the highest occurrence of udder halves categorised as hard was observed at either pre-mating or docking. Udder halves categorised as lump had their highest occurrence at either docking or weaning. Udder halves detected with a defect (hard or lump) at pre-mating were more likely (RRR: 6.8 to 1444) to be defective (hard or lump) at future examinations (pre-lambing, docking, or weaning) within the same year or pre-mating the following year, compared to udder halves categorised as normal. In the second study, the change of udder half defect type over the first six weeks of lactation was variable. However, it was observed that the udder half defects, particularly udder halves categorised as hard, decreased during lactation. Failure to express milk in udder halves in early lactation was associated with a higher occurrence and persistency of udder half defects. In conclusion, the occurrence of diffuse hardness or lumps in an udder half changed over time, and the risk of future occurrence of a defect was higher in udder halves previously categorised as either hard or lump. Hence, it is recommended that farmers identify and cull ewes with udder halves categorised as hard and lump.

In Vitro Fermentation of Browsable Native Shrubs in New Zealand.

Information on the nutritive value and in vitro fermentation characteristics of native shrubs in New Zealand is scant. This is despite their potential as alternatives to exotic trees and shrubs for supplementary fodder, and their mitigation of greenhouse gases and soil erosion on hill-country sheep and beef farms. The objectives of this study were to measure the in vitro fermentation gas production, predict the parameters of the in vitro fermentation kinetics, and estimate the in vitro fermentation of volatile fatty acids (VFA), microbial biomass (MBM), and greenhouse gases of four native shrubs (Coprosma robusta, Griselinia littoralis, Hoheria populnea, and Pittosporum crassifolium) and an exotic fodder tree species, Salix schwerinii. The total in vitro gas production was higher (p < 0.05) for the natives than for the S. schwerinii. A prediction using the single-pool model resulted in biologically incorrect negative in vitro total gas production from the immediately soluble fraction of the native shrubs. However, the dual pool model better predicted the in vitro total gas production and was in alignment with the measured in vitro fermentation end products. The in vitro VFA and greenhouse gas production from the fermentation of leaf and stem material was higher (p < 0.05), and the MBM lower (p < 0.05), for the native shrubs compared to the S. schwerinii. The lower in vitro total gas production, VFA, and greenhouse gases production and higher MBM of the S. schwerinii may be explained by the presence of condensed tannins (CT), although this was not measured and requires further study. In conclusion, the results from this study suggest that when consumed by ruminant livestock, browsable native shrubs can provide adequate energy and microbial protein, and that greenhouse-gas production from these species is within the ranges reported for typical New Zealand pastures.

Growth and Body Composition of Artificially-Reared Lambs Exposed to Three Different Rearing Regimens.

This study was designed to investigate the influence of pellet fibre level, milk replacer composition and age at weaning on growth and body composition of lambs reared artificially. Romney ram lambs were randomly allocated to one of three rearing treatments; HFP57: commercial milk replacer to 57 days of age, and high fibre concentrate pellets; HFP42: commercial milk replacer with early weaning at 42 days of age, and high fibre concentrate pellets; LFP42: high protein milk replacer from 2-16 days of age followed by commercial milk replacer with early weaning at 42 days of age, and low fibre concentrate pellets. Lambs were slaughtered at 57 days of age. Overall average daily liveweight gain of lambs did not differ (p > 0.05) between treatments. Dressing out percentage, carcass weight, empty small intestine and omental fat were higher (p < 0.05) in HFP57 than in both HFP42 and LFP42 lambs. HFP42 and LFP42 lambs had heavier (p < 0.05) empty rumen weights. Whole body protein content was higher (p < 0.05) in HFP42 lambs compared to both HFP57 and LFP42 lambs. Fat content and daily fat deposition were greater (p < 0.05) in HFP57 lambs than HFP42 and LFP42 lambs. Weaning lambs at 42 days of age with provision of either low or high fibre concentrate pellets, resulted in similar growth rates, reduced whole body fat deposition and was a more cost-effective rearing regimen.

Rumen Development of Artificially-Reared Lambs Exposed to Three Different Rearing Regimens.

The objective of this study was to examine the effect of three different rearing regimens on rumen development in lambs reared artificially. Romney ram lambs were randomly allocated to one of three treatments: commercial milk replacer fed to 57 d of age and high fibre concentrate pellets (HFP57); commercial milk replacer, high fibre concentrate pellets, and early weaning from milk replacer at 42 d of age (HFP42); high protein milk replacer from 2-16 d of age followed by commercial milk replacer, low fibre concentrate pellets, and early weaning from milk replacer at 42 d of age (LFP42). Lambs were slaughtered at 57 d of age. Volatile fatty acid content in rumen fluid at slaughter was analysed and rumen tissue samples were collected for histological examination. The rumen n-butyric content was greater (p < 0.05) in both LFP42 and HFP42 treatment lambs compared to HFP57 lambs. The n-valeric content was greater (p < 0.05) in LFP42 lambs compared to both HFP57 and HFP42 treatment lambs. Thickness of the rumen dorsal wall determined by ultrasound scanning at 49 d was greater (p < 0.05) in both HFP42 and LFP42 lambs compared to HFP57 lambs. There was an interaction (p < 0.05) between treatment and site of rumen tissue sampling on papillae width, density, and rumen muscular layer thickness. Collectively, early weaning and the provision of a low fibre pellet leads to improved rumen function and physical development.

Effect of Palpable Udder Defects on Milk Yield, Somatic Cell Count, and Milk Composition in Non-Dairy Ewes.

In non-dairy ewes, udder defects hinder the survival and weight gain of their pre-weaned lambs. The objectives of this study were to determine the effects of palpable udder defects on milk yield, somatic cell count (SCC), and milk composition in non-dairy Romney ewes. Ewes with a history of udder defects or normal udders were selected for the study. Of a total of 48 ewes that lambed, 30 ewes reared at least one lamb, and were milked six times, once weekly, for the first six weeks of lactation. Udder halves were palpated and scored at each milking event. Multivariate linear mixed models examined the impacts of udder defects on udder-half and whole-udder milk yield, SCC, and milk composition (fat, protein, lactose, total solids, and solids non-fat (SNF)). Across the six examinations, 24.7% of the total 352 udder-half examinations were observed to be defective. Udder halves that were defective at least once produced on average 57.9% less (p < 0.05) milk than normal udder halves, while normal udder halves with a contralateral defective half yielded 33.5% more (p < 0.05) milk than normal udder halves. Successive occurrence of both hard and lump udder defect categories in an udder-half, udder defect detection early in lactation, and a high frequency of udder defect detection were all associated with udder-half milk yield loss (p < 0.05). At the whole-udder level, no differences in milk yield (p > 0.05) were observed between those with one udder-half defective and both normal udder-halves. However, udders in which one udder half was categorised as hard but progressed to lump and remained as lump until 42 days of lactation produced less (p < 0.05) milk compared with normal udders. With the exception of SNF, there were no significant associations (p > 0.05) between milk composition parameters and udder defect. Overall, these findings emphasise the importance of udder health in non-dairy ewes and the potential effect of udder defects on their lambs.

Timing of exogenous progesterone administration is critical for embryo development and uterine gene expression in an ovine model of maternal constraint.

Progesterone (P4) administration in early pregnancy enhances embryo growth in sheep but is associated with decreased embryo survival. This study examined the effects of exogenous P4 administered during specific time periods between pregnancy Day 0 and Day 6 to determine the critical time point for advancement of embryo growth without pregnancy loss and to examine Day 6 and Day 19 endometrial gene expression. Suffolk (S) embryos were transferred into Cheviot (C) ewes that received exogenous P4 (CP4) on Days 0-3 (CP40-3), Days 0-6 (CP40-6), Days 2-4 (CP42-4) or Days 3-6 (CP43-6). Additionally, S embryos were transferred to C and S ewes that did not receive P4 (CnP4 and SnP4). Day 19 embryos from CP4 ewes were longer (P<0.05) than those from CnP4 ewes. CP42-4 ewes had embryos of similar size to those of CP40-3 and CP40-6 ewes but had higher pregnancy rates. There was altered expression of genes associated with embryo implantation and histotroph production: diacylglycerol-O-acyltransferase (DGAT2), hepatocyte growth factor (HGF) and prostaglandin endoperoxide synthase 2 (PTSG2) on Day 6 and endometrial galectin 15 (LGALS15) and mucin glycoprotein 1 (MUC1) on Day 19. This suggests that specific timing of P4 administration is critical to the enhanced embryo growth and survival observed. These findings provide a platform for further investigation aimed at advancing embryo development and survival.

Effect of exogenous progesterone on embryo size and ewe uterine gene expression in an ovine 'dam size' model of maternal constraint.

Progesterone (P4), acting via its receptor, regulates uterine function and histotroph production, which are crucial to embryo growth. This study aimed to examine exogenous P4 effects on embryo size and differential endometrial gene expression at Day 19 of gestation using a 'dam size' sheep model of maternal constraint. Purebred Suffolk (S, genotypically large) embryos were transferred into recipient groups of Cheviot (C, genotypically small) or Suffolk ewes that had, or had not, been pre-treated with P4 from Days 0 to 6 of pregnancy. At Day 19S embryos were collected from four experimental groups: P4 pretreated S ewes (SP4; n=5), untreated S ewes (SnP4; n=15), P4 pretreated C ewes (CP4; n=7) and untreated C ewes (CnP4; n=21). Day-19 embryos from CP4 ewes were larger (P<0.05) than those from CnP4 ewes and similar in size (P>0.05) to embryos from SnP4 and SP4 ewes. Expression of mucin 1 (MUC1) and prostaglandin-endoperoxide synthase 2 (PTGS2) was upregulated in uterine horns ipsilateral to the corpus luteum from CP4 ewes. Prostaglandin receptor (PGR), MUC1 and PTGS2 expression was upregulated, whilst cathepsin L (CTSL) and radical S-adenosyl methionine domain-containing 2 (RSAD2) expression was downregulated in the ipsilateral horn of SP4 ewes. This suggests that pretreating ewes with exogenous P4 may alleviate early pregnancy maternal constraint via mechanisms that alter uterine function. However, further research is required to investigate the timing of P4 administration and its impact on conception rates.

Functional development of the adult ovine mammary gland--insights from gene expression profiling.

BACKGROUND: The mammary gland is a dynamic organ that undergoes dramatic physiological adaptations during the transition from late pregnancy to lactation. Investigation of the molecular basis of mammary development and function will provide fundamental insights into tissue remodelling as well as a better understanding of milk production and mammary disease. This is important to livestock production systems and human health. Here we use RNA-seq to identify differences in gene expression in the ovine mammary gland between late pregnancy and lactation. RESULTS: Between late pregnancy (135 days of gestation ± 2.4 SD) and lactation (15 days post partum ± 1.27 SD) 13 % of genes in the sheep genome were differentially expressed in the ovine mammary gland. In late pregnancy, cell proliferation, beta-oxidation of fatty acids and translation were identified as key biological processes. During lactation, high levels of milk fat synthesis were mirrored by enrichment of genes associated with fatty acid biosynthesis, transport and lipogenesis. Protein processing in the endoplasmic reticulum was enriched during lactation, likely in support of active milk protein synthesis. Hormone and growth factor signalling and activation of signal transduction pathways, including the JAK-STAT and PPAR pathways, were also differently regulated, indicating key roles for these pathways in functional development of the ovine mammary gland. Changes in the expression of epigenetic regulators, particularly chromatin remodellers, indicate a possible role in coordinating the large-scale transcriptional changes that appear to be required to switch mammary processes from growth and development during late pregnancy to synthesis and secretion of milk during lactation. CONCLUSIONS: Coordinated transcriptional regulation of large numbers of genes is required to switch between mammary tissue establishment during late pregnancy, and activation and maintenance of milk production during lactation. Our findings indicate the remarkable plasticity of the mammary gland, and the coordinated regulation of multiple genes and pathways to begin milk production. Genes and pathways identified by the present study may be important for managing milk production and mammary development, and may inform studies of diseases affecting the mammary gland.