Maternal zinc intakes and homeostatic adjustments during pregnancy and lactation.

Zinc plays critical roles during embryogenesis, fetal growth, and milk secretion, which increase the zinc need for pregnancy and lactation. Increased needs can be met by increasing the dietary zinc intake, along with making homeostatic adjustments in zinc utilization. Potential homeostatic adjustments include changes in circulating zinc, increased zinc absorption, decreased zinc losses, and changes in whole body zinc kinetics. Although severe zinc deficiency during pregnancy has devastating effects, systematic reviews and meta-analysis of the effect of maternal zinc supplementation on pregnancy outcomes have consistently shown a limited benefit. We hypothesize, therefore, that zinc homeostatic adjustments during pregnancy and lactation improve zinc utilization sufficiently to provide the increased zinc needs in these stages and, therefore, mitigate immediate detrimental effects due to a low zinc intake. The specific questions addressed are the following: How is zinc utilization altered during pregnancy and lactation? Are those homeostatic adjustments influenced by maternal zinc status, dietary zinc, or zinc supplementation? These questions are addressed by critically reviewing results from published human studies on zinc homeostasis during pregnancy and lactation carried out in different populations worldwide

Changes in back fat thickness during late gestation predict colostrum yield in sows

Directing protein and energy sources towards lactation is crucial to optimise milk production in sows but how this influences colostrum yield (CY) remains unknown. The aim of this study was to identify associations between CY and the sow’s use of nutrient resources. We included 37 sows in the study that were all housed, fed and managed similarly. Parity, back fat change (ΔBF), CY and performance parameters were measured. We obtained sow serum samples 3 to 4 days before farrowing and at D1 of lactation following overnight fasting. These were analysed for non-esterified fatty acids (NEFA), urea, creatinine, (iso) butyrylcarnitine (C4) and immunoglobulins G (IgG) and A (IgA). The colostrum samples collected 3, 6 and 24 h after the birth of the first piglet were analysed for their nutrient and immunoglobulins content. The technical parameters associated with CY were parity group (a; parities 1 to 3 =value 0 v. parities 4 to 7 =value 1) and ΔBF D85-D109 of gestation (mm) (b): CY (g) =4290–842a–113b. ( R2=0.41, P<0.001). The gestation length ( P<0.001) and the ΔBF between D109 and D1 of lactation (P=0.050) were identified as possible underlying factors of the parity group. The metabolic parameters associated with CY were C4 at 3 to 4 days before farrowing (a), and 10logC4 (b) and 10logNEFA (c) at D1 of lactation: CY ( g) =3582–1604a+1007b− 922c ( R2=0.39, P=0.001). The colostrum composition was independent of CY. The negative association between CY and ΔBF D85-D109 of gestation could not be further explained based on our data. Sows that were catabolic 1 week prior to farrowing seemed unable to produce colostrum to their full potential. This was especially the case for sows with parities 4 to 7, although they had a similar feed intake, litter birth weight and colostrum composition compared with parities 1 to 3 sows. In conclusion, this study showed that parity and the use of body fat and protein reserves during late gestation were associated with CY, indicating that proper management of the sow’s body condition during late gestation could optimise the intrinsic capacity of the sow’s CY

Mechanistic target of rapamycin (mTOR) activation during ruminant mammary development and function : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Animal Science at Massey University, Palmerston North, New Zealand

This thesis examines the abundance of total and activated mechanistic target of rapamycin (mTOR) pathway components in the developing and functional ruminant mammary gland. mTOR pathway activation is stimulated by a wide range of intra- and extracellular signals, such as amino acids (AA) and hormones, making the mTOR pathway a potential candidate for the development of intervention strategies designed to increase ruminant lactation potential. Tissues from two trials shown to improve lactation potential; dam-fetal nutrition and exogenous growth hormone (GH) administration during lactation, were used to measure changes in total and activated mTOR pathway protein abundance. Results show mammary glands of d 140 fetal lambs carried by maintenance fed dams and dairy cows administered exogenous GH, had increased abundance of total and activated mTOR and mitogen activated protein kinase (MAPK) pathway proteins. Increased abundance was associated with changes in biochemical indices. In the GH study MAPK pathway activation was stimulated by IGF-1 signaling whilst mTOR pathway activation was proposed to be mediated by AA signalling. Data from the GH study shows, L-arginine a known activator of the mTOR pathway, was the only AA reduced in both plasma and the lactating gland. Upstream factors were not identified for the phenotype observed in the dam-fetal nutrition study, but similar mechanisms were proposed. To elucidate the potential regulation of mTOR pathway activation by L-arginine and examine the effect on milk production, in vitro bovine cell culture models were evaluated. Results show that none of the models evaluated produced a lactating phenotype – a pre-requisite to accurately study the lactating gland in vitro. Finally, this thesis shows L-arginine administration from d 100 to d 140 of pregnancy, in twin bearing ewes had no effect on mTOR protein abundance or activation. However, administration from d 100 to parturition improved maternal gland health. In summary, this thesis associates improved lactation potential with increased total and activated mTOR pathway protein abundance, and the administration of L-arginine during late gestation with improved gland health. These findings provide fundamental knowledge that may lead to the development of novel technologies to increase ruminant gland performance and health

Phosphorus in pig diets

Pig feed is mainly based on cereals where phosphorus (P) is mostly present in inositol hexaphosphate (IP6), which is not readily available to monogastric animals. More available P sources are often added to ensure that pigs’ requirements are fulfilled; this results in high excretion levels of P. The digestibility of P depends on phytase activity and amount of IP6 in feedstuffs. The overall aim was to study effects of liquid feeding, P levels and phytase supplementation on digestibility and performance. Effects of soaking and P levels on digestibility were studied by total collection in metabolic cages, and effects on performance were studied in 192 growing pigs. Effects of soaking fermentation and phytase supplementation on ileal and total tract digestibility were studied with indicator technique on pigs surgically fitted with PVTC cannulas. P levels and phytase supplementation were studied in 104 pregnant sows for two reproduction cycles. All diets were cereal based and included wheat. Basic properties of a cereal mix fermented with whey, wet wheat distillers’ grain and water in different temperatures were also studied. Soaking reduced the level of IP6, whereas apparent digestibility of P was not significantly improved. Soaking increased average daily weight gain, carcass weights and improved the energy conversion ratio in pigs fed a low P diet to the same level as pigs fed high P diets. Low P diets resulted in lower femur density than high P diets. However, soaking of a low P diet resulted in increased femur density. Fermentation degraded IP6 efficiently and improved ileal apparent digestibility of P, organic matter, nitrogen, amino acids and total tract apparent digestibility of organic matter. Microbiological and biochemical properties of fermented liquid diets are strongly affected by feed components and temperature used. Phytase supplementation slightly affected apparent digestibility of P. Supplementing a low P gestation diet with phytase did not significantly affect sow performance. The slight effects of phytase supplementations found may depend on high levels of intrinsic phytase in the diets, and possibly suggest that the provided P level in the sows may have been sufficient. Under typical Swedish conditions of sow management, reduced total P level in gestation diets seems not to negatively affect performance

Improved timed-mating, non-invasive method using fewer unproven female rats with pregnancy validation via early body mass increases

For studies requiring accurate conception-timing, reliable, efficient methods of detecting oestrus reduce time and costs, whilst improving welfare. Standard methods use vaginal cytology to stage cycle, and breeders are paired–up using approximately five proven females with proven males to achieve at least one conception on a specific day. We describe an alternative, fast, consistent, non-invasive method of timed-mating using detection of lordosis behaviour in Wistar and Lister-Hooded rats that used unproven females with high success rates. Rats under reverse-lighting had body masses recorded pre-mating, day (d) 3-4, d8, d10 and d18 of pregnancy. Using only the presence of the oestrus dance to time-mate females for 24-hrs, 89% Wistar and 88% Lister-Hooded rats successfully conceived. We did not observe behavioural oestrus in Sprague-Dawleys without males present. Significant body mass increases following mating distinguished pregnant from non-pregnant rats, as early as d4 of pregnancy (10% ± 1.0 increase cf 3% ± 1.2). The pattern of increases throughout gestation was similar for all pregnant rats until late pregnancy, when there were smaller increases for primi- and multiparous rats (32% ± 2.5; 25% ± 2.4), whereas nulliparous rats had highest gains (38% ± 1.5). This method demonstrated a distinct refinement of the previous timed-mating common practice used, as disturbance of females was minimised. Only the number required of nulli-, primi- or multiparous rats were mated, and body mass increases validated pregnancy status. This new breeding-management method is now established practice for two strains of rat and resulted in a reduction in animal use

Comparison of breed of dairy cow under grass-based spring milk production systems

End of project reportThe objective of this study was to investigate the potential differences among different dairy cow breeds across two feeding systems on milk production, udder health, milking characteristics, body weight, body condition score, hormone parameters, ovarian function, survival and overall reproductive efficiency. The breeds investigated included Holstein-Friesian (HF), Montbéliarde (MB), Normande (NM), Norwegian Red (NRF) and Holstein- Friesian × Montbéliarde (MBX) and Holstein- Friesian × Normande (NMX). Selection within the HF breed has, until recently, been predominantly for milk production with little or no direct selection for functional traits other than those correlated with superior type. The MB and the NM have been simultaneously selected for both milk and beef production in the past. The NRF were imported as calves and come from a more balanced total merit index incorporating production and cow functionality since the early 1970s. The dairy cow breeds were grouped into blocks of two within breed groups and randomized across two spring-calving grass-based feeding systems: low concentrate feeding system (LC) and high concentrate feeding system (HC). Those on LC feeding system were offered approximately 530 kg/cow over the total lactation, while those on HC feeding system were offered approximately 1030 kg/cow

Evaluation and development of animal breeding in Ireland

End of project reportThe primary objectives of this study were: 1) to annually evaluate the pertinence of the Irish dairy cattle breeding index, the Economic Breeding Index (EBI) and where necessary modify, 2) to evaluate the potential of do-it-yourself milk recording as an alternative to current supervised methods of milk recording, and 3) to estimate the level and rate of accumulation of inbreeding in Irish dairy and beef cattle, to quantify its effects on traits of economic importance, and to develop remedial measures to minimise the future accumulation of inbreeding in Ireland

Milk whey protein concentration and mRNA associated with β-lactoglobulin phenotype

Two common genetic variants of β-lactoglobulin (β-lg), A and B, exist as co- dominant alleles in dairy cattle (Aschaffenburg, 1968). Numerous studies have shown that cows homozygous for β-lg A have more β-lg and less α-lactalbumin (α-la) and casein in their milk than cows expressing only the B variant of β-lg (Ng-Kwai-Hang et al. 1987; Graml et al. 1989; Hill, 1993; Hill et al. 1995, 1997). These differences have a significant impact on the processing characteristics of the milk. For instance, the moisture-adjusted yield of Cheddar cheese is up to 10% higher using milk from cows of the β-lg BB phenotype compared with milk from cows expressing only the A variant (Hill et al. 1997). All these studies, however, describe compositional differences associated with β-lg phenotype in established lactation only. No information is available on the first few weeks of lactation, when there are marked changes in the concentrations of β-lg and α-la (Pérez et al. 1990)

The effect of Holstein-Friesian genotype and feeding system on selected performance parameters of dairy cows on grass-based systems of milk production in Ireland

End of project reportThe overall objective of this project was to assess, the effect of strain of Holstein-Friesian dairy cow, pasture-based feed system (FS) and their interaction on animal performance in terms of milk productivity and lactation profile, body weight (BW), body condition score (BCS), feed intake and energy balance (EB), reproductive performance and overall economic profitability