Canadian Journal of Animal Science

Antimicrobial use and misuse in the agricultural sector are driving causes of the ongoing antimicrobial resistance public health crisis. To enact meaningful on-farm stewardship and best-practice discussions, we need more research that provides in-depth understandings of producers' beliefs, values, practices, and challenges surrounding the use of antimicrobials. Through a discussion of the experiences of twelve cow-calf operators in Ontario, we demonstrate how qualitative research methods can be mobilized to gain insights into the priorities and concerns that shape farmers’ use of antimicrobials, as well as barriers to their effective use.

The objective was to measure the effect of temperature-humidity index (THI) on egg laying and hatching parameters. Quails were randomly transferred to two cage blocks at 20.55 ± 0.05ºC and 52.25 ± 0.68% relative humidity (RH), accepted as 66 THI group. One cage block was transferred to the next room at 16.15 ± 0.13ºC and 70.77 ± 0,38 % RH considered as 61 THI group. In the second stage of the study, the cage block previously accepted as 61 THI group, was considered as to 69 THI group by rising up the temperature to 21.97 ± 0.18 ºC. The group previously considered as 66 THI group was accepted as 76 THI group by rising up the temperature to 28.06 ± 0.02 ºC. Feed consumption and egg weight were significantly decreased, in 69 and 76 THI groups. Daily egg production was lower in 61 and 66 THI groups than that in 69 THI group. In 76 THI group, shell weight and yolk height, were decreased. High THI caused negative effects on feed consumption, egg weight, egg quality and feed conversion ratio.

This study investigated the effects of melatonin implants in pregnancy on milk production and composition, and the quality of colostrum in dairy goats. Thirty days before kidding, 92 goats (group MEL) received one melatonin implant, and the remaining 177 goats (group CON) did not. Three monthly milk evaluations included milk yield (MY, kg/d), composition (%Fat, %Protein, % Lactose), daily yield (Fat, g/d Protein, g/d Lactose). A sample of colostrum was obtained from 165 goats, from which its composition, IgG concentration were measured. MEL had a significantly (P<0.01) higher MY in the second month (3.16 ± 0.10 kg/d) than CON (2.78 ± 0.07 kg/d). In the three milk samplings, fat concentrations were significantly higher (P<0.05) in the MEL than in the CON does. In the second milk sampling, does that had received a melatonin implant produced higher (P<0.05) daily milk yield components than did non-implanted (Fat: 144 ± 6.0 vs 115 ± 3.4; Protein: 104 ± 3.4 vs 91 ± 2.5; Lactose: 148 ± 5.8 vs 131 ± 4.3 g/d). In conclusion, melatonin implants administered 30 d before kidding increased milk production, the amounts of milk daily components in the second month of lactation, and the concentration of fat milk.

The study examined the effects of a microencapsulated complex of biofactors and antioxidants [P(BF+AOx)] on growth and health status of broiler chickens challenged with cold stress. Day-old broilers were allotted to 4 treatments in a 2x2 factorial design with 2 dietary treatments:1)Control (CON;corn-wheat-soybean-based), and 2)CON + 0.015% P(BF+AOx) and 2 thermal treatments:1)Thermoneutral (TN; 29°C±1 on d8-10, 54h), and 2)Cold stress (CS; 20°C on d8-10, 54h). Treatments were allocated to 6 replicates, with 8 chicks/replicate. Growth performance was measured weekly from d 0-21. On d14, 2birds/cage were euthanized. Cold stress reduced (P<0.05) total antioxidant capacity (TAC), serum IgM, jejunal villus height (VH), villus width (VW) and VH:crypt depth (VH:CD). Irrespective of CS, P(BF+AOx) improved (P<0.05) FI (631vs.592 g/bird), BW (383vs.349 g/bird), BW gain (337 vs. 301 g/bird) up to d 14, and plasma TAC. Regardless of the challenge model, P(BF+AOx) increased (P<0.05) duodenal VW, VH:CD, jejunal and ileal VH:CD, and the relative abundance of cecal Intestinimonas and Colidextribacteria, compared to the CON. In conclusion, CS altered broiler blood parameters and gut morphology, but 0.015% P(BF+AOx) improved early life growth performance, TAC, and gut health, irrespective of CS, suggesting that it could be an effective strategy to support overall health and performance.

This study examined the impact of a low crude protein (CP) diet incorporating meat and bone meal (MBM) as an alternative (AD) to standard diet, on broiler performance, nitrogen intake, excretion, and meat quality. A total of 846 male Ross 308 chicks were assigned to two diets in a randomized complete block design with 9 replicates of 47 birds/replicate. The diets were a plant-based control (20.4 and 19.5% CP) and an AD diet (-2.0% CP, +2.5% MBM) in the grower and finisher phases. Compared to the control, the AD diet reduced nitrogen intake (P = 0.01) and excretion (P < 0.01) while improving nitrogen retention efficiency (P < 0.001) without affecting body weight, feed conversion, or carcass yield. Breast yield was higher in the AD group (P < 0.001). In the AD group, the ultimate pH of breast meat increased slightly (P = 0.07), cooking loss decreased (P = 0.002), sarcoplasmic protein solubility tended to increase (P = 0.09), while muscle protein emulsifying properties remained unchanged. Breast meat proximate composition was not affected by the AD diet. In conclusion, the AD diet can reduce nitrogen loss and emissions without negatively impacting broiler production, provided that amino acid requirements are met.

This study evaluated the effects of corncob as a source of insoluble fibre and xylanase enzyme on broiler chicken performance, ileal digestibility, intestinal morphology, gastrointestinal pH, and serum biochemical traits. 256-one-day-old (Ross 308) broiler chicks were randomly given six diets for 24 days: a control diet with 0%, 2.5%, or 5% corncob, with or without xylanase, in a 3 × 2 factorial arrangement. Then, chicks were given the control diet with or without xylanase until they reached 42 days. Adding corncob to diets reduced performance during the grower phase (P≤0.05), but when removed, the performance did not differ from the control (P≥0.05). Corncob reduced ash digestibility and cholesterol levels (P≤0.05) while increasing the relative weight of the heart, gizzard, and duodenum and improving the ileal villus high-to-crypt depth ratio (P≤0.05). The feed conversion ratio increased due to corncob inclusion in diets at the starter and grower phases (P≤0.05) but did not differ from the control at the finisher phase. Xylanase supplementation improved performance, nutrient digestibility, intestinal histomorphology, and reduced cecum weight with digestive tract pH (P≤0.05). Therefore, adding corncob with xylanase enzyme to broiler chickens' diet does not negatively impact their performance. On the contrary, it improves the broilers' health and reduces production costs.

Feeding high-grain diets is a common practice in intensive ruminant production systems to meet animal energy requirements and maximize feed efficiency. One of the consequences of these diets is trans (t)10 shifted ruminal biohydrogenation, which includes increased formation of t10-18:1 and t10, cis (c)12-conjugated linoleic acid (t10, c12-CLA) at the expense of t11-18:1 and c9, t11-CLA. In dairy cows, the t10 shift has been associated with milk fat depression. In beef cattle, the t10 shift has not been associated with negative effects on animal performance or marbling fat deposition; however, it may negatively impact meat fat eating quality by decreasing its cis monounsaturated fatty acid to saturated fatty acid ratio. Finally, the t10 shift increases t10-18:1 accumulation in ruminant-derived foods (dairy, beef, and lamb), which at high enough levels may compromise the nutritional quality of these foods. The present review will cover our current understanding of the rumen microbes involved in the t10 shift and its implications for milk fat synthesis and beef fat quality.

A total of 1,488 pigs were transported to slaughter using a mechanically-ventilated vehicle in the winter in Canada. On each of six journeys, a sub-sample of 78 pigs were randomly assigned to two space allowances (0.46 or 0.53 m2/pig), distributed across six compartments, in two positions (near-front and near-rear) and three deck levels (top, middle, and bottom). Compartment ambient conditions (e.g., T°C and RH%) were monitored during transport and pig behaviour was recorded during lairage. Blood lactate, hematocrit, creatine kinase (CK) concentrations and meat quality in the longissimus (LM), semimembranosus (SM), and adductor (AD) muscles were assessed on a total of 108 pigs. Pigs transported at 0.53 m2/pig had greater blood hematocrit levels (P = 0.05), but lower blood CK concentrations at slaughter (P = 0.01). The top deck was colder during all transport events (P < 0.001), and pigs transported in this location stood less in lairage compared to those transported on the bottom deck (P = 0.05). Pigs from the top deck showed lower L* values in the LM and SM muscle (P = 0.02 and P = 0.04, respectively). Overall, animal location had a greater impact than space allowance on animal welfare and meat quality of pigs.

This study aimed at assessing the effects of space allowance on microclimate and pig stress during transportation in a mechanically-ventilated vehicle. On each journey (6), 114 pigs were randomly assigned to different space allowances (0.46, 0.49 or 0.59 m2/pig) tested in the near-front, middle and near-rear compartments and on the top, middle and bottom decks. In each compartment, ambient conditions (e.g., T°C and RH%) were monitored. Behaviour was recorded during lairage. A total of 162 pigs were selected for the analysis of blood hematocrit proportion and lactate, and creatine kinase (CK) concentrations, and the evaluation of meat quality in the loin and ham muscles. The bottom deck was more humid before and during transport (P ≤ 0.05) and pigs from this location stood and drank more in lairage (P < 0.001). Pigs transported on the top deck had greater blood lactate and CK concentrations (P < 0.05) than those transported on the bottom deck, and when transported at 0.49 m2/pig produced paler loins (P < 0.05) than those transported at 0.46 m2/pig. The within-trailer location had a greater impact on the microclimate, collected animal welfare measures, and meat quality of pigs transported in an actively ventilated trailer than space allowance.

The objective of the study was to determine the effect of time of feeding pre-farrow on farrowing time and duration. Two hundred and ninety-eight (298) mixed parity sows were assigned to morning (0700 h) or evening (1900 h) feeding upon entry into the farrowing room until farrowing. More sows from the morning-fed group farrowed between 0700 and 1500 h than the evening-fed group (51.43 vs. 21.95%, P < 0.001). There were no differences (P > 0.10) in farrowing duration. Number of piglets born alive, stillborn, and mummies did not differ (P > 0.10) among treatments. Evening-fed sows had an increased number of pigs weaned, resulting from reduced preweaning mortality compared to the morning-fed sows (P < 0.05). Morning feeding may be beneficial for maximizing the number of farrowing events that start during working hours and evening feeding may improve litter outcomes.

The impact of complete replacement of maize with raw or heat-treated sweet cassava (Manihot esculenta) tuber meal (CTM) on productive performance and egg quality of Jumbo quail hens was determined. A total of 240, six-week-old hens were randomly allocated to 60 cages (4 birds/cage) and assigned to five experimental diets with 12 replicates each. The diets were a standard layer mash diet without CTM (CON) and a standard layer mash diet in which 100% maize was replaced with raw (CTMR), boiled (CTMB), autoclaved (CTMA) and oven-dried CTM (CTMO). The highest overall feed intake, body weight gain and final body weight (P < 0.05) was observed from the CON group while the lowest was from the CTMB group. Overall FCR and mortality were not significantly influenced by the diets. Fourteen-week-old hens on CON had a higher (P < 0.05) rate of lay than CTMR. Eggs from CON had the brightest yolk colour values than all the treatment groups. Moreover, eggs from CON had the least shape index than those from CTMO. Diet CTMA promoted heavier (P < 0.05) eggshells than CTMR. Jumbo quail hens reared on maize-based diet showed better performance followed by autoclaving treatment, whereas boiling treatment compromised performance traits.

This study aimed to quantify the relationship between residual feed intake (RFI) measured in 500 heifers and subsequently as mid-gestation cows at the Roy Berg Kinsella Research Station (KIN; n = 227) and Lacombe Research and Development Centre (LRDC; n = 273). Heifers were initially tested for RFI adjusted for end of test rib fat (RFIfat) at 8–12 months of age and then again as 3-year-old first-calf heifers at KIN and as 4–13-year-old cows at LRDC. Heifer RFIfat measured in drylot on a forage diet was associated (R² > 0.53; P < 0.001) with RFIfat measured again as older cows. Each 1 kg DM day⁻¹ change in heifer RFIfat equaled 0.48 ± 0.10 and 0.75 ± 0.19 kg DM day⁻¹ change in cow RFIfat for KIN and LRDC, respectively. Linear effects were also reported for RFIfat component traits, where DMI (P < 0.001), ADG (P < 0.060), mid-test metabolic weight (P < 0.001), and end of test rib fat (P < 0.001) measured as heifers were related when measured again as older cows. In addition, the linear effects of heifer RFIfat on cow RFIfat were constant across cow age groups from 4–10 years of age. These results show that selection for RFI in heifers will result in cows that are also more feed efficient.

This study aimed to evaluate the ruminal degradation and intestinal digestion of nutrients of two cultivars of oat grains (CDC Nasser and CDC Seabiscuit) in comparison with a barley grain (CDC Meredith that was considered the control treatment) in dairy cows. Nasser showed higher rumen undegradable protein (RUP; P < 0.01) and intestinal digestible protein (P < 0.01) than Seabiscuit or control. However, the total digestible protein was not different among grain varieties (P = 0.25). The in vitro intestinal digestibility of RUP (dIBP) for Nasser was higher than control (P = 0.02); however, the dIBP in Seabiscuit did not differ from other cultivars. The intestinal digestible rumen bypass starch and total digestible starch were lower in the oat grain varieties than in the control (P < 0.01). The truly absorbed protein supplied to the small intestine (DVE) was highest for control, intermediate for Seabiscuit, and lowest for Nasser (P < 0.01). Moreover, control showed a higher estimated feed milk value than oat varieties (P < 0.01). In conclusion, Seabiscuit shared similar rumen degradation and intestinal digestibility with control suggesting that Seabiscuit oat grain could in some extension replace barley grain in diets for dairy cows.

This study investigated factors influencing heifer replacement and cow–calf profitability using 361 cows (born 2011–2018) at the Lacombe Research and Development Centre, Alberta, Canada. Profitability was measured by marginal returns (MR) incorporating feed costs, heifer opportunity cost, calf and cull revenues, and a premium for cows retained in the herd. The study evaluated the linear effects of lifetime productivity, feed efficiency (residual feed intake adjusted for off-test backfat thickness; RFIfat), and genomic retained heterozygosity, an indicator of heterosis, on MR, feed costs, total costs, and net revenue (NR). Lifetime productivity, defined by the cumulative weight of calves weaned, was positively associated with MR and NR (P < 0.01). RFIfat influenced total cost, MR, and NR (P < 0.05), with MR improved by $168.50 cow⁻¹ year⁻¹ for each unit decrease in RFIfat, although regression and group mean comparisons were not fully consistent. Genomic retained heterozygosity positively impacted MR and NR, with a 10$21.80 and $20.50 cow⁻¹ year⁻¹, respectively. Cow breed type did not affect longevity, MR, or NR. In conclusion, RFIfat and genomic diversity were important factors to consider in heifer replacement decisions when lifetime DMI was estimated as described in the present study.

This study measured the digestibility of crude protein, crude fat, and dry matter in three protein sources: poultry by-product meal (PBPM), poultry viscera, and crushed mealworms using diatomaceous earth as an indicator. A control diet was made, and test diets were mixed in a 70:30 control diet:test ingredient ratio. Forty-four female mink housed in individual cages were fed experimental diets for 5 days, and fecal samples were collected and analyzed for nutrient residues compared to the diet composition to determine digestible nutrient levels. Mealworms had a greater dry matter digestibility (P < 0.01; 96.26%) than poultry viscera (77.29%) and PBPM (86.76%). PBPM had a lower fat digestibility (P < 0.01; 84.64%) than mealworms (94.78%) and poultry viscera (98.15%). There was no significant difference among treatments for protein digestibility. Using a standard nitrogen-to-protein conversion factor of 6.25, the crude protein content of the mealworms was 51.74%, although with an apparent digestibility coefficient of 0.77, this ingredient had an available crude protein composition of 39.70 ± 2.95. A nitrogen-to-protein conversion factor of 4.80 would be more accurate than 6.25 when using mealworms as a feed ingredient for monogastric animals.

The objective of this study was to identify potential genetic variants and positional candidate genes associated with growth and feed efficiency traits in American mink. Genome-wide association studies (GWAS) were performed using deregressed estimated breeding values of 1037–1872 individuals (as pseudophenotypes), genotyped with the Affymetrix Mink 70K single nucleotide polymorphism (SNP) array. A total of 42 SNPs located on 11 different chromosomes were significantly (false discovery rate < 0.01) associated with six growth and feed efficiency traits. Furthermore, 153 genes were identified within 1-Mb windows flanking these significant SNPs. Several positional candidate genes such as TUBB, CDKN1A, SRSF3, GPRC6A, RFX6, and KPNA5 were previously associated with feed efficiency and growth traits in other livestock species. The Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses revealed that these genes were involved in lipid metabolism, hormone signaling and regulation, and muscle development. To our knowledge, this is the first GWAS to identify genetic variants and biological mechanisms associated with growth and feed efficiency traits in American mink. These findings provide a biological foundation for improving these traits using genomic selection programs to select more efficient mink.

The objective of this in vitro study was to assess the effects of high-carvacrol oregano oil (ORE; 50 g/kg oregano oil, 800–802 g/kg carvacrol), on microbial fermentation and CH4 production. In the experiment (a complete randomized block design), treatments included a negative control (CTL, no additive), a positive control (monensin, MON, 10 mg/L of culture fluid), and ORE (20, 40, 80, 120, 200, 160, and 1000 mg/L of culture fluid). Compared with CTL, MON shifted (p < 0.05) volatile fatty acid (VFA) profile from acetate and butyrate to propionate production, thereby reducing (p < 0.05) CH4 production (−26%). Monensin decreased (p < 0.05) NH3 and branched-chain VFA concentrations. Of the doses evaluated, only the highest dose (1000 mg/L) affected ruminal microbial fermentation and CH4 production. At this dose, ORE reduced (p < 0.05) gas production, total VFA, acetate, propionate and NH3 concentrations, and CH4 production (−22%). The reduced gas production and total VFA is an indication of feed digestion inhibition. These results suggest that ORE may decrease CH4 production and improve ruminal N utilization. However, these findings need to be validated in vivo to determine the optimal dose to benefit from the positive effects while avoiding the negative impact of ORE on feed digestion.

Focus remains on reducing the excretion of surplus zinc (Zn) from pigs through manure due to environmental and public health concerns. Growing–finishing pigs may need less dietary Zn than current EU legislation allows and what is typically applied on farms. The aim of this study was to evaluate the effect of three dietary Zn levels on productivity, Zn homeostasis, and health status in growing pigs fed a grain and soybean meal-based diet with a high inclusion of phytase (1000 phytase units). Ninety pigs were offered a diet with 1431 and 83 ppm total Zn from weeks 0–2 and 2–6 post-weaning, respectively, followed by one of three dietary Zn levels (31 (unsupplemented), 69, or 102 ppm total Zn, n = 30/Zn level) from weeks 6–16 post-weaning (30–110 kg). Productivity and health were unaffected by dietary Zn level. Despite differences in serum Zn according to dietary Zn level in week 10, serum Zn remained above the assumed sufficient level following all dietary Zn levels through the experiment. No signs of parakeratosis were observed, and we conclude that growing–finishing pigs produce and stay healthy without added Zn to a phytase supplemented grain–soybean meal-based diet when optimal dietary Zn levels are applied up to 30 kg.

Increasing sow milk yield is essential to achieve maximal growth of suckling piglets, and nutrition can stimulate milking capacity. From 90 days of age until puberty, replacement gilts should not undergo major feed restriction as it will inhibit mammary development. Providing phytoestrogens in that period will stimulate mammary hyperplasia. During gestation, feed intake of gilts must ensure that backfat at the end of gestation is above 16 mm to support mammary development. In the last third of gestation, providing 40% more lysine than requirements via the addition of soybean meal increases mammary mass in gilts, but not in multiparous sows. A high nutrient intake during transition is crucial, whereby providing sows 12.6 Mcal metabolizable energy and 22.0 g standardized ileal digestible (SID) Lys daily ensures a high colostrum production and maximizes milk yield in the following lactation. During lactation, there are quadratic effects of energy and protein intakes on the weight of suckled mammary glands and sows should not be restricted-fed to avoid excessive mobilization of body reserves. Furthermore, the provision of adequate lysine is critical to maximize litter growth, with optimum daily intakes between 47.7 and 51.3 g SID Lys for primiparous sows and 51.3–67.2 g SID Lys for multiparous sows.

Plasma and tibia attributes were investigated in broiler chickens raised on three gut health management programs in commercial farms (study 1) and research station settings (study 2). The programs were as follows: (1) conventional antibiotics (CON), (2) raised without medically important antimicrobials (RWMIA), and (3) raised without antibiotics (RWA). Birds had free access to feed and water from placement to harvest; samples of blood and left tibia were collected on day 28 in both studies and further samples were taken on day 41 in study 2. In both studies, there were no program differences (P > 0.05) on plasma metabolites with exception of enzyme concentrations with notably higher levels of circulating plasma alkaline phosphatase (ALP) in birds reared on the RWA program (P ≤ 0.04). Differences were observed among programs for tibia length in both studies (P < 0.05). Birds reared on RWMIA exhibited significantly (P = 0.016) higher tibia ash than CON on day 41. Observed differences in the plasma enzyme concentrations, tibia length, and ash concentration suggest altered metabolism which could be linked to gut health management programs and their ability to support gut integrity and function in the absence of antibiotics.

Behaviour, heart rate (HR), and blood lactate concentration of 144 pigs, equally distributed into lighter (L, 122 kg on average) and heavier (H, 153 kg on average) groups, were assessed to study the effects of slaughter weight on pigs’ response to a simulated loading and unloading procedure using four ramp configurations, i.e., 0° (level ramp), 15° slope and 1.66 m length, 15° slope and 2.71 m length (15°LO), and 25° slope and 1.66 m. No interaction was found between ramp configuration and slaughter weight (P > 0.10). The frequencies of pigs’ slips or falls (P = 0.01) increased on sloped ramps compared to the floor level (Padj < 0.05), and pigs jumped-off more from the 25° than the 15°LO ramp (Padj = 0.05). Pigs negotiating the 25° slope ramp presented a higher concentration of blood lactate than those walking at the floor level (P = 0.02). When compared to L pigs, H pigs were more reluctant to move (P = 0.05), and presented higher increments of HR (ΔHR) during handling (P = 0.03). In conclusion, heavier pigs were more difficult to handle, regardless of the ramp steepness, which alone reduced ease of handling and affected the physiological condition of pigs.

Production practices for first cut alfalfa (ALF), alfalfa-grass (AFG) and grass silages (GRS) were surveyed on dairy farms in four Canadian regions, i.e. British Columbia (BC, n=21), Prairies (PRA, n=32), Central Canada (CEN, n=218), and Atlantic Canada (ATL, n=17). Results are presented as percentages of responses by region; forage type, silo type, wilting method and inoculant use varied among regions. In CEN (93.0%), ATL (88.2%), and PRA (68.8%) AFG was most common. In BC, GRS was most common (66.7%). ALF was only reported in the PRA (28.1%) and CEN (5.6%). Respondents from BC only reported bunkers (52.4%) and baleage (28.6%). Bunkers were most common in PRA (31.3%), followed by baleage (28.1%), piles (18.8%) and tower silos (6.3%). In CEN tower silos were most common (37.2%), followed by bunkers (33.9%), baleage (22.0%), and piles (1.8%). In ATL bunkers (29.4%) and baleage (29.4%) were most common, followed by tower silos (17.7%), and piles (11.8%). Wilting was mostly done in windrows: BC (55.0%), PRA (45.0%), CEN (77.1%), and ATL (71.0%). In BC and ATL, 45% and 17.7%, respectively, of respondents used tedders to enhance wilting. In BC, CEN, ATL, and PRA, 55%, 58.3%, 64.7% and 44.8% respectively of respondents used inoculants.

Lameness is the second most prevalent morbidity in North American feedlot cattle and is both an animal welfare and economic concern. Lameness accounts for 30%–40% of all feedlot treatments with greater than 70% being foot-related lameness (FRL). This review focused on foot rot (FR), digital dermatitis (DD), and toe tip necrosis syndrome (TTNS). While there are significant study-to-study differences regarding the prevalence of FR, DD, and TTNS, it is unequivocal that FR is the most prevalent. Poor pen conditions are risk factors for both FR and DD, but the epidemiology of the two diseases is quite different. Whereas FR is diagnosed throughout the feeding period, DD typically occurs after 80 days on feed (DOF). TTNS is the least prevalent of the three FRL, but has the greatest negative effect on animal welfare and production performance. Most TTNS cases occur within 50 DOF with treatment failure leading to a significant loss in production performance and even death. This review provides an overview of the epidemiology of lameness in feedlot cattle with emphasis on the prevalence and risk factors associated with FR, DD, and TTNS.

Relationships between farm and animal factors and the fatty acid (FA) profile and milk amyloid A (MAA) content of milk were determined in 336 Holstein dairy cows on 24 Quebec farms using multiple regression. Cows with a somatic cell count (SCC) above 200,000, and farms feeding palm oil were excluded. Independent factors of the regression models included days in milk (DIM), parity, yield, fat and protein contents of milk, SCC, and the dietary contents of neutral detergent fibre (NDF) and crude fat (CFAT). Non- significant variables with P-values >0.25 were stepwise removed. Models with high fits were those of total short chain FA, medium chain FA, odd- and branched-chain FA (OBCFA), and saturated long chain FA with R2 of 0.33, 0.36, 0.34, and 0.41, respectively. The fat and protein contents and yield of milk did not affect the milk FA profile. Higher NDF increased the milk fat proportions of short chain FA and OBCFA and decreased those of monounsaturated (MUFA) and polyunsaturated FA (PUFA). Higher CFAT reduced this proportion of short chain FA but increased those of MUFA and PUFA. Increasing DIM reduced this proportion of short chain FA and increased that of medium chain FA. Higher SCC increased MAA.

We previously reported that high levels (≥50%) of black soldier fly larvae meal (BSFLM) reduced growth and altered organs morphology in broiler chickens. Herein we further examined gastrointestinal, breast, bone, plasma, and litter attributes in broiler chickens fed partial to complete replacement of soybean meal (SBM) with BSFLM. A total of 1152 day-old Ross × Ross 708 male chicks (n = 8) were allocated to 48 pens and assigned one of six diets: a basal corn-SBM diet (0BSFLM), four diets in which SBM in 0BSFLM was replaced with BSFLM at 12.5%, 25%, 50%, and 100% (12.5BSFLM, 25BSFLM, 50BSFLM, and 100BSFLM) and a final diet (0 + AGP) in which 0BSFLM was fed with coccidiostat and antibiotic. Birds were bled for plasma and necropsied for samples. Litter samples were collected on days 45 to 47. Breast weight, woody breast, and hardness scores and tibia morphometry reduced linearly in response to BSFLM inclusion (P < 0.001). BSFLM linearly increased plasma Lys, Met, Thr, uric acid, creatine kinase and decreased Arg and potassium (P < 0.05). Litter ammonium nitrogen and potassium decreased linearly in response to BSFLM (P < 0.001). In conclusion, the data suggested physiological and metabolic inefficiencies in broiler chickens fed isocaloric and isonitrogenous diets with ≥50% BSFLM replacement of SBM.