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Increasing early (<3 mo) nutrient feeding levels and growth rate of dairy calves has been found to increase their milk production potential. The objective of this study was to compare the effect of offering milk diets with or without added carbohydrates and amino acids on calf growth, weaning age, and subsequent growth and milk yield of dairy heifers in their first lactation. Friesian calves born at Massey University (n = 57) were selected at random, weighed, and allocated to receive 1 of 3 diets. All calves were fed colostrum from 1 to 3 d of age, followed by 4 L of whole milk (WM) per head per day and probiotics between 3 and 18 d of age. At 18 d of age, calves were weighed to ensure mean body weight (BW); then, at 19 d of age, calves changed diets to 1 of 3 treatments, which reached full treatment rate at 21 d of age. The diets were 4 L/ head per day of WM (M); 4 L/head per day of WM plus 200 g of plant carbohydrates (MP); and 4 L/head per day of WM plus 200 g of plant carbohydrates with amino acids (MPA). Calves were weaned upon reaching a BW of 90 kg. During this period, BW, body condition, and hip height and width were measured. The heifers were commingled and grazed on ryegrass and white clover pastures until calving at 23 mo of age, when BW, body condition, and hip height and width were measured again. Milk yield and composition were measured throughout first lactation. At weaning, calves fed MPA had greater mean BW gain, a lower number of days to target BW, and a greater mean hip width gain compared with calves in the M group, although mean gain in hip height did not differ among treatments. Total calf starter intake during the milk period was lower for MPA-fed calves compared with those offered M, mainly due to a shorter milk feeding period required to attain the 90-kg weaning weight, whereas mean daily starter intake and straw intake did not differ. No difference was observed in the calving rate or calving age of heifers in any of the dietary feeding groups. First lactation fat-corrected milk yield, milk fat percentage, and total milk fat and protein yields were greater for animals reared on MP and MPA compared with M. Body weight, hip height and width at parturition, milk protein percentage, somatic cell count, or days in milk did not differ among treatments. Increasing nutrient intake, during the milk feeding period, improved the BW gain of calves and milk production of dairy heifers during first lactation. [ABSTRACT FROM AUTHOR]

Claw horn disorders are one of the main causes of lameness in dairy cows globally. This study aimed to develop material testing techniques to assess changes in the mechanical properties of bovine claw horn (BCH) and to compare these mechanical properties with existing methods of assessing claw horn disorders during lactation. Lameness was also measured through locomotion scoring to assess the clinical significance of changes observed in the scoring for lesions. Experiment 1 used 8 claws collected from four 12 to 18 mo old beef heifers, to develop BCH sample storage methods and techniques to test the mechanical properties of BCH (puncture resistance and elastic modulus). The increase in the moisture content of BCH had a significant negative exponential effect on the elastic modulus of the sole and white line claw horn and a linear reduction in the puncture resistance of BCH. Placing BCH samples in sealed plastic bags and storing them either at 2°C or by freezing samples at -22°C did not alter the dry matter content and, consequently, the mechanical properties of the claw horn tissue. In experiment 2, BCH was collected from 36 lactating dairy cows and mechanical properties were tested using puncture resistance. Puncture resistance of the sole area of the claw horn decreased significantly when hemorrhages in the tested area increased. The puncture resistance of the sole and white line areas decreased at d 160 postpartum when the cows exhibited higher lesion scores and was lower in hind claws that had higher lesion scores when compared with the fore claws. The highest puncture resistance was found at 270 d postpartum, when the animals were at pasture. Puncture resistance was found to be an effective technique for assessing the effect of period of lactation and increasing hemorrhage levels on the mechanical properties and structural strength of bovine claw horn. It was found to be a good method of comparing changes and differences in mechanical properties and structural strength of BCH from the sole and white line areas within each claw and differences between claws. White line BCH consistently had significantly lower puncture resistance compared with the sole. Bovine claw horn with greater levels of hemorrhage or lower puncture resistance, or both, may provide less protection and increase the risk of foreign body penetration, trauma, and secondary infection of the corium of the claw. [ABSTRACT FROM AUTHOR]

Providing adequate and balanced amino acid supply increases nitrogen capture from animal feed into human food products, creating greater food security while lowering environmental impact. New processing techniques allow the extraction of specific protein (SP) from distiller's dried grains and solubles (DDG) resulting in greater rumen un-degradable amino acid (RUAA) supply. The degradation rate and residual RUAA content of two SP extracted from corn (cDDGS) were compared with cDDGS, soya bean meal (SBM) and RUAA processed from SBM and RSM. A Cornell model was applied to thirty-three dried and ground (1 mm) samples of; cDDGS, SBM, RUAA SBM, RUAA RSM, and two SPs (SP2 and SP50), that were combined with a partial mixed ration (PMR), buffered, flushed with CO2 and incubated for 16 h at 39°C to measure in vitro gas production (IVGP) using Ankom-RFS. Feed composition was analysed pre and post incubation and RUAA profile was estimated using gas liquid chromatography. Data was analysed using general linear modeling, applying feed as a fixed effect and all other factors as random effects, using a confidence interval of 0.95 and differences using Tukey's test (P value <0.05). Gas production was highest from cDDGS and lowest from Hiprosoya, but similar in RUAA from SBM and RSM, SP2 and SP50. RUAA was greatest from SBM, but similar from Hiprosoya, SP2 and SP50 and lowest from RUAA RSM. Liquor pH did not differ. SP50 had the highest total VFA and lowest A:P ratio, while SP2 was similar to RUAA from SBM and/or RSM. In conclusion, results demonstrated the potential of SP2 and SP50 to increase the RUPAA from cDDGS to similar amounts provided by RUAA SBM. [ABSTRACT FROM AUTHOR]

The objective of this experiment was to compare the mechanical strength and lesion score of hoof horn in dairy cows over the postpartum period when housed in a cubicle system. Mechanical tests were completed on sole horn taken from a total of 36 live cows at 50 (p1), 100 (p2) and 160 (p3) days postpartum (pp). Simultaneously, all claws were assessed for lesions score (LS) of the sole (S) and white line (WL) areas of the hoof. Horn samples were collected from all claws and analysed for elastic modulus (EM) and punch force (PR). Each measurement was repeated 8 times on the S and WL areas of each claw. Horn samples were scored for haemorrhage levels, using a 6 point scale (0- no haemorrhage and 5- severe). PR was significantly (P<0.001) lower in samples with high haemorrhage scores, demonstrating a lower structural integrity (8.72a, 8.53a, 8.06b, 7.75b, 6.08c and 4.99d N for scores 0 to 5 respectively). Total LS of the S area increased significantly at day 160 (p1- 1241b, p2-1295b, p3- 1676a) and the WL at day 100 pp (p1- 1042b, p2- 1448a, p3-1710a) (P < 0.001). The S and WL areas of the hind outer (HO) claws had significantly higher lesion scores than other claws (sole HO- 340.2a, other- 149.4 to 184.2b; WL HO- 267.5a, other- 168.4 to 228.9b) (P < 0.001). PR of the sole area was significantly lower in the HO claws, which had higher lesion scores, when compared to other claws (HO- 7.2Na, other- 8.0a to 9.2Na) (P < 0.001). PR decreased as day pp increased and lesion scores increased (p1- 9.0a, p2- 8.6ab, p3- 8.2bN) (P < 0.001). PR of the WL area was significantly lower in the hind left (HL) claws compared to other claws (HL- 4.9Nb, other- 5.5 to 6.2Nb) and was significantly lower (P < 0.01) at day 160 pp(p1- 7.1a, p2- 6.2a,b, p3- 5.6b). EM of the sole and WL areas decreased (P < 0.01) at day 100 pp (S p1- 48.8a, p2-17.7b, p3- 18.2b N/mm2; WL p1- 32.2a, p2-17.8b), p3-19.7b N/mm2), but did not differ between claws. Mechanical tests accurately reflect changes in claw horn lesions following parturition. [ABSTRACT FROM AUTHOR]

The objective was to measure forage maize (FM)composition (DM, CP, NDF, ADF, ADL, starch, water soluble carbohydrates (WSC), ash) and degradability (dg) for qualitative trait loci (QTL) mapping. Near isogenic lines (NILs) of FM (n=350) were produced from 3 parent varieties and grown in randomised block design in 3 EU countries. UK FM was harvested in mid October (27 % DM). Data from parental varieties (ANT, NKB) with 8 NILs (A to H) (in g/kg DM unless stated otherwise) were analysed (ANOVA) and compared (Tukey's test). DM: A 281.1, B 284.8, C 250.2, D 299.5, E 292.9, F 288.5, NKB 270.9, ANT 294.5, G 295.8, H 284.6 (sed 2.11, P<0.001). NDF: A 483.3, B 485.7, C 490.7, D 455.7, E 455.3, F 398.3, NKB 489.7, ANT 410.3, G 471.3, H 452.3 (sed 31.73). ADF, A 289.7, B 271.33, C 320.0, D 253.3, E 238.3, F 307.3, NKB 275.7, ANT 241.7, G 255.0, H 311.3 (sed 16.56, P,0.05). ADL: A 20.0, B 19.3, C 46.7, D 26.7, E 32.0, F 38.7, NKB 44.3, ANT 13.3, G 32.3, H 33.3 (sed 16.06). Ash: A 42.9, B 39.3, C 53.1, D 31.4, E 39.4, F 37.6 NKB 43.0, ANT 39.9, G 37.9, H 115.9 (sed 5.15, P<0.001). CP: A 73.5, B 63.0, C 72.1, D 67.7, E 57.7, F 57.5, NKB 59.2, ANT 63.5, G 55.3, H 59.2 (sed 1.22, P<0.001). Starch: A 159.5, B 247.7, C 98.3, D 201.8, E 507.0, F 324.0, NKB 122.0, ANT 434.9, G 464.9, H 148.7 (sed 88.69, P<0.001). WSC (mg/ml DM): A 5.00, B 13.3, C 15.0, D 10.0, E 9.8, F 5.0, NKB 2.9, ANT 8.1, G 4.1, H 17.8 (1.30, P<0.001). FM dg; quickly (a), slowly (b) and total dg rates, starch development, structure and relationship with protein varied significantly between NILs, pectin and amylopectin did not. Starch levels increased as DM increased, while NDF, ADF, ADL, CP and ash decreased. Genotype affected starch, ash and crude protein levels, starch and fibre degradability, starch structure and relationship with protein (P<0.001), but did not affect pectin and amylopectin. Distinct QTL were involved in FM composition, degradability and starch characteristics. QTL mapping can be used in genetic selection and breeding of FM to increase forage utilization efficiency and sustainability. [ABSTRACT FROM AUTHOR]

The regulation of mammary gland involution occurs through multiple levels including environmental factors, hormones, and local intramammary signals. Primary cilia (PC) are signaling organelles that sense biochemical and biophysical extracellular stimuli and are vital for cellular and tissue function. The aim of this study was to examine the distribution, incidence, and orientation of PC. Furthermore, we determined changes in expression levels of the signal transducer and activator of transcription (STAT)6 at the onset of bovine mammary gland involution. Mammary tissue was collected from pasture-fed, primiparous, nonpregnant Friesian dairy cows at mid lactation (n = 5 per group) killed 6-h after milking (lactating controls) and during involution after 7 and 28 d of nonmilking (NM). Fluorescent immunohistochemistry and confocal microscopy of tissue sections showed that PC were present on luminal secretory epithelial cells (SEC), myoepithelial cells (MEC), and stromal fibroblast cells (SFC). Furthermore, in all 3 experimental groups, different PC positions or orientations relative to the cell surface were identified on SEC and MEC, which projected toward the lumen and were either straight, bent, or deflected against the apical cell surface, whereas PC in SFC were confined to the interalveolar space. However, by 28-d NM, fewer PC projected into the luminal space and most appeared deflected or projected toward the interalveolar space. Furthermore, by 28-d NM, with the increase in stromal connective tissue, more PC were detected within the interalveolar and interlobular stroma. At 28-d NM, we observed a decrease in luminal cilia relative to the total number of cilia. The number of ciliated cells in the total fraction (SEC, MEC, and SFC) was the same for all 3 groups, although in the luminal fraction (SEC and MEC), PC per nuclei increased by 28-d NM relative to lactation. At all 3 stages, we detected variations in shape and orientation of PC within the same alveolus, with some PC projecting directly into lumen, whereas others appeared to be bent or deflected flat against the cell surface. Within each treatment, the average number of bent cilia was low, whereas the average number of deflected cilia was higher than the average number of cilia projecting directly into the lumen. Quantitative real-time reverse transcription PCR analysis showed that expression levels of milk protein genes (aS1-casein, a-lactalbumin, and ?-casein) declined and that of lactoferrin increased in the involuted mammary tissue following NM, compared with lactating controls. Although STAT6 mRNA levels did not change following NM, STAT6 protein levels did increase following 28-d NM compared with the control lactation group. In conclusion, PC were detected in all cell types in the mammary gland, and changes in orientation during involution suggest the potential for PC to play a role in signal transduction through both mechanosensation and chemosensation. Furthermore, the STAT6-mediated signaling pathway may have a role during involution of the mammary gland. [ABSTRACT FROM AUTHOR]

In dairy cows, short-term changes in milking frequency (MF) in early lactation have been shown to produce both an immediate and a long-term effect on milk yield. The effect of MF on milk yield is controlled locally within mammary glands and could be a function of changes in either number or activity of secretory mammary epithelial cells (MEC). Insulin-like growth factor I (IGF-I) signaling is one candidate factor that could mediate these effects, as it can be controlled locally within mammary glands. Both MEC number and activity can be affected by IGF-I signaling by activating the phosphoinositide 3-kinase (PI3K)/Akt and extracellular-signal-regulated kinase (ERK)1/2 pathways. To investigate the relationship between MF and IGF-I signaling, udder halves of 17 dairy cows were milked either 4 times a day (4x) or once a day (1x) for 14 d in early lactation. On d 14, between 3 and 5 h following milking, mammary biopsies were obtained from 10 cows from both udder halves, and changes in the expression of genes associated with IGF-I signaling and the activation of the PI3K/Akt and ERK1/2 pathways were measured. The mRNA abundance of IGF type I receptor, IGF binding protein (IGFBP)-3, and IGFBP-5 were lower following 4x milking relative to 1x milking. However, the mRNA abundance of IGF-I was not affected by MF. Both IGFBP3 and IGFBP5 are thought to inhibit IGF-I; therefore, decreases in their mRNA abundance may serve to stimulate the IGF-I signal in the 4x-milked mammary gland. The activation of PI3K/Akt pathway was lower in response to 4x milking relative to 1x, and the activation of the ERK1/2 was unaffected by MF, suggesting that they do not mediate the effects of MF. [ABSTRACT FROM AUTHOR]

Prolactin (PRL) is important in the regulation of milk synthesis in mammary epithelial cells (MEC). In cattle, circulating levels of PRL are not limiting, suggesting the possible involvement of other factors that may control the response to PRL at the cellular level. The effects of milking frequency (MF) on milk synthesis are controlled locally within mammary glands and involve PRL signaling. To further investigate this relationship between MF and PRL signaling, udder halves of 17 dairy cows were milked either 4 times a day (4x) or once a day (1x) for 14 d in early lactation. Mammary biopsies were obtained 3 to 5 h following milking from both udder halves of 10 cows, and changes in PRL and associated pathways were measured. The abundance of STAT5A mRNA was higher after 4x milking, whereas that of the PRL receptor (PRLR) and STAT3 were lower relative to that after 1x milking. In 4x mammary tissues, the protein levels of STAT5, activated STAT5, and β1-integrin were higher, whereas the those of the long isoform of PRL receptor and activated STAT3 were lower than 1x tissues. The activation of STAT5 correlated strongly with major milk protein mRNA abundance (r = 0.86 to 0.94) and β1-integrin protein levels (r = 0.91). These results confirm that major milk protein gene expression is associated with STAT5 activation and suggests that the STAT5 and β-integrin signaling pathways are linked. Modulation of β1-integrin abundance in response to changes in MF may be a mechanism that controls the MEC ability to respond to PRL and therefore its secretory activity. [ABSTRACT FROM AUTHOR]

In dairy cows, short-term changes of milking frequency in early lactation have been shown to produce an immediate and a long-term effect on milk yield in stall-fed cows. The effect is controlled locally within mammary glands and could be a function of either secretory mammary epithelial cell number or activity. To resolve this and determine its applicability in other feed management systems, a unilateral milking frequency experiment was conducted with udder halves of 17 multiparous, pasture-fed dairy cows milked either 4 times (4x) or once a day (lx) for 14 d from 5 ±2 d in milk. Mean half-udder milk yield during the treatment period was higher from the 4x compared with lx udder halves and continued to be higher until 200 d in milk once returned to twice a day milking. Mammary biopsies were obtained on d 14 of treatment from both udder halves of 10 cows. Proliferation of mammary cells was higher in 4x udder halves compared with 1x, whereas no difference in apoptosis levels was detected. Abundance of αS1-casein, β-casein, α-lactalbumin, and β-lactoglobulin mRNA was higher in tissue samples from 4x udder halves compared with lx, whereas lactoferrin mRNA abundance was lower in 4x udder halves. In summary, change in milking frequency during early lactation affects proliferation of mammary cells as well as expression of the major milk protein genes, which both contribute to the observed changes in milk yield during and after unilateral milking frequency treatment. [ABSTRACT FROM AUTHOR]

Thin soles are a significant cause of lameness in dairy cattle but in most cases the diagnosis is based on subjective assessment. Ultrasonography has been used to more directly estimate sole thickness, but mostly on a one-off basis or over a short period of time. Data over a longer period of time (such as a lactation period) are lacking and there are no descriptions of the normal changes that occur over time and to show how sole thickness at calving relates to thickness later in lactation. This study measured the distance between the external sole surface and the distal phalanx (DP) in 25 mixed breed (Jersey cross Friesian and Friesian) heifers on five occasions over their first lactation (approximately 10, 60, 110, 160 and 220 days post calving). There was a significant effect of claw (medial/lateral) and of time after calving on DP. Mean DP was highest on day 10 and was lowest on day 110 at the tip of the distal phalanx (SI) and on day 160 25 mm towards the heel from the tip (S2). DP was greater at SI in medial claws and S2 in lateral claws. Although mean DP decreased between days 10 and 110, this change was correlated to DP at day 10. At SI claws with a DP of <7.5 mm tended to increase in thickness between day 10 and 110. Claws which were ≤$8.25 mm at day 10 were 2.43 (95% CI 0.866.89) times more likely to be thin (<7.0 mm) at day 110, but of the 12 thin claws at day 110, six had had an adequate DP (>8.25 mm) at day 10. A single measurement of DP at calving was not an effective method for predicting which claws would became thin during lactation. [ABSTRACT FROM AUTHOR]

The rates of development of 2 tissues in mammary glands, parenchyma (PAR) and the mammary fat pad (MFP), in response to nutrition in early life might have a major bearing on lifetime milk production. Historical studies reported that feeding greater amounts of dietary nutrients from postweaning to puberty increased growth rates of heifers and stimulated the growth of MFP at the expense of PAR, which might suggest compromised mammary development and future milk production. The current study sought to determine if a higher volume of whole milk (8 vs. 4 L/d) offered to calves would increase rates of growth and development of PAR in mammary glands at weaning (1 to 12 wk). To measure these tissues, we developed 2 simple methods to assess the size of PAR and MFP at the time of screening using ultrasound. We report that calves offered 8 L/d of whole milk had greater rates of growth until weaning (0.86 ± 0.06 vs. 0.81 ± 0.09 kg/d), compared with calves offered 4 L/d. Ultrasonography showed that despite the faster rates of growth in calves offered 8 L/d of milk/d, the ratio of PAR:MFP depth was 40% less at weaning in the front glands (34%) compared with calves offered 4 L of milk/d. Rear glands were less impaired. The ultrasound methods developed here might be useful to monitor the development of mammary glands in response to different nutritional regimens during the preweaning period., (Copyright © 2020 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)