Metabolic Live Weight Research Articles

Animal factors that affect enteric methane production measured using the GreenFeed monitoring system in grazing dairy cows

Similar to all dairy systems internationally, pasture-based dairy systems are under increasing pressure to reduce their greenhouse gas (GHG) emissions. Ireland and New Zealand are 2 countries operating predominantly pasture-based dairy production systems where enteric CH4 contributes 23% and 36% of total national emissions, respectively. Ireland currently has a national commitment to reduce 51% of total GHG emissions by 2030 and 25% from agriculture by 2030, as well as striving to achieve climate neutrality by 2050. New Zealand's national commitment is to reduce 10% of methane emissions by 2030 and between 24% and 47% reduction in methane emissions by 2050. To achieve these reductions, factors that affect enteric methane (CH4) production in a pasture-based system need to be investigated. The objective of this study was to assess the relationship between enteric CH4 and other animal traits (feed intake, metabolic liveweight, energy corrected milk yield, milk urea concentration, and body condition score [BCS]) in a grazing dairy system. Enteric CH4 emissions were measured on 45 late lactation (213.8 ± 29 d after calving) grazing Holstein-Friesian and Holstein-Friesian × Jersey crossbred cows (lactation number 3.01 ± 1.65, 538.64 ± 59.37 kg live weight, and 3.14 ± 0.26 BCS) using GreenFeed monitoring equipment for 10 wk. There was a training period for the cows to use the GreenFeed of 3 wk before the 10-wk study period. The average enteric CH4 produced in the study was 352 g ± 45.7 g per day with an animal to animal coefficient of variation of 13%. Dry matter intake averaged 16.6 kg ± 2.23 kg per day, while milk solids (fat plus protein) averaged 1.62 kg ± 0.29 kg per day. A multiple linear regression model indicated that each one unit increase in energy corrected milk yield, metabolic liveweight and milk urea concentration, resulted in an increase in enteric CH4 production per day by 3.9, 1.74, and 1.38 g, respectively. Although each one unit increase in BCS resulted in a decrease in 39.03 g CH4 produced per day. When combined, these factors explained 47% of the variation in CH4 production, indicating that there is a large proportion of variation not included in the model. The repeatability of the CH4 measurements was 0.66 indicating that cows are relatively consistently exhibiting the same level of CH4 throughout the study. Therefore, enteric CH4 production is suitable for phenotyping.

Residual Feed Intake and Rumen Metabolism in Growing Pelibuey Sheep.

This study was carried out to evaluate the residual feed intake (RFI), volatile fatty acid (VFA) production and enteric methane (CH4) from growing Pelibuey sheep. In this case, 12 non-castrated Pelibuey with an initial average live weight (LW) of 21.17 ± 3.87 kg and an age of 3 months, were housed in individual pens and fed a basal diet with 16% of crude protein and 11 MJ ME for 45 days. Dry matter intake (DMI) was measured and the daily weight gain (DWG) was calculated using a linear regression between the LW and experimental period. Mean metabolic live weight (LW0.75) was calculated. RFI was determined by linear regression with DWG and LW0.75 as independent variables. Lambs were classified as low, medium, and high RFI. Feed efficiency was determined as DWG/DMI. For determining rumen pH, ammonia nitrogen concentration NH3-N), and VFA, ruminal fluid was obtained using an esophageal probe on day 40. Feed intake of low RFI lambs was approximately 16% lower (p < 0.05) while growth rate was not significantly different. Their average energy loss, expressed as CH4 production per kilogram of metabolic weight, was 17% lower (p < 0.05).

Performance and parasitological parameters of steers sequentially grazed with lambs

In the majority of mixed or sequential gazing studies with sheep, cattle performance remained unaffected. However, the treatment regime of the sheep in these studies was often intense and this may have limited cross-transmission of nematodes from sheep to cattle. We conducted a sequential grazing trial with cattle and sheep with moderate anthelmintic intervention. Twenty first season grazing steers were stratified to 10 couples according to their origin, egg excretion per gram faeces (EPG), metabolic weight and previous weight gain record. Thirty naturally infected ewe lambs were stratified to 5 groups according to metabolic live weight and EPG. Five pairs of the steers were sequentially grazed with the 5 groups of lambs whereas another five pairs of steers served as control. Grazing duration was 70 days with a subsequent indoor period of additional 35 days for the steers. Weight and EPG was recorded 3 days before and 27, 49, 70 and 105 days after trial start. The recorded live-weight of the sequentially grazed steers was 182 ± 14, 191 ± 11, 205 ± 15, 219 ± 15 and 236 ± 18 and the live-weight of the control steers was 180 ± 18, 193 ± 19, 203 ± 21, 217 ± 24 and 234 ± 24 kg respectively. The EPG of the sequentially grazed steers 3 days before grazing start and at day 27, 49, 70 and 105 was 94 ± 100, 95 ± 48, 49 ± 42, 58 ± 41 and 140 ± 73 EPG respectively. The EPG of the control steers at the same dates was 96 ± 82, 98 ± 24, 104 ± 77, 98 ± 71 and 270 ± 287 EPG respectively. The sequentially grazed steer groups did not differ from the control groups with regard to EPG, live weight and daily weight gain. However, the sequentially grazed steers showed elevated pepsinogen levels compared to the control steers (e.g. 3.34 ± 1.05 units tyrosine and 1.29 ± 0.50 units tyrosine after 70 days of grazing, respectively). Larval samples from individual steer coprocultures of both groups were tested PCR-positive for Cooperia oncophora, Ostertagia ostertagi and Haemonchus contortus. We conclude that short term sequential grazing of first season grazing steers with lambs excreting mainly eggs of Haemonchus spp. did not adversely affect steer performance despite increased pepsinogen values. However, hot and dry conditions may have had a suppressive effect on larval development, migration and finally uptake by the steers.

Genetic variability in the feeding behavior of crossbred growing cattle and associations with performance and feed efficiency.

The objectives of the present study were to estimate genetic parameters for several feeding behavior traits in growing cattle, as well as the genetic associations among and between feeding behavior and both performance and feed efficiency traits. An additional objective was to investigate the use of feeding behavior traits as predictors of genetic merit for feed intake. Feed intake and live-weight data on 6,088 growing cattle were used of which 4,672 had ultrasound data and 1,548 had feeding behavior data. Feeding behavior traits were defined based on individual feed events or meal events (where individual feed events were grouped into meals). Univariate and bivariate animal linear mixed models were used to estimate (co)variance components. Heritability estimates (± SE) for the feeding behavior traits ranged from 0.19 ± 0.08 for meals per day to 0.61 ± 0.10 for feeding time per day. The coefficient of genetic variation per trait varied from 5% for meals per day to 22% for the duration of each feed event. Genetically heavier cattle, those with a higher daily energy intake (MEI), or those that grew faster had a faster feeding rate, as well as a greater energy intake per feed event and per meal. Better daily feed efficiency (i.e., lower residual energy intake) was genetically associated with both a shorter feeding time per day and shorter meal time per day. In a validation population of 321 steers and heifers, the ability of estimated breeding values (EBV) for MEI to predict (adjusted) phenotypic MEI was demonstrated; EBVs for MEI were estimated using multi-trait models with different sets of predictor traits such as liveweight and/or feeding behaviors. The correlation (± SE) between phenotypic MEI and EBV for MEI marginally improved (P < 0.001) from 0.64 ± 0.03 to 0.68 ± 0.03 when feeding behavior phenotypes from the validation population were included in a genetic evaluation that already included phenotypic mid-test metabolic live-weight from the validation population. This is one of the largest studies demonstrating that significant exploitable genetic variation exists in the feeding behavior of young crossbred growing cattle; such feeding behavior traits are also genetically correlated with several performance and feed efficiency metrics. Nonetheless, there was only a marginal benefit to the inclusion of time-related feeding behavior phenotypes in a genetic evaluation for MEI to improve the precision of the EBVs for this trait.

Evaluation of high-concentrate diets that vary in physically effective neutral detergent fibre for finishing lambs

The objective of this research was to evaluate lamb diets with a high proportion of concentrate and various levels of physically effective neutral detergent fibre (NDF) using tropical ingredients. Four diets were formulated: D1 with 16.5% physically effective NDF (peNDF), D2 with 21.4% peNDF, D3 with 23.3% peNDF, and D4 with 24.6% peNDF. Twenty male Santa Inês lambs at four months old with an average liveweight (LW) of 18.6 ± 3.4 kg were fed for 49 days. There were no differences (P &gt;0.05) among the diets in dry matter (DM) intake. Crude protein (CP) intake, relative to either LW or metabolic live weight (LW0.75) or LW, was greater (P ≤0.05) for D2 and D3 than for D1 or D4. Lower (P ≤0.05) NDF intake, relative to LW0.75 or LW, was lower for D1 than for the other diets. Selection indexes (SIs) were similar (P &gt;0.05) among diets. Animals that consumed D1 had less (P ≤0.05) rumination time per bolus. Meaningful variations were not observed in performance and efficiency of finishing lambs that were related to differences in peNDF among the diets. Santa Inês lambs were able to adapt to diets with low levels of peNDF by increasing rumination time as a consequence of increased fibre consumption and greater particle size selection.

Nitrogen retention in hair sheep lambs with a gradient of Haemonchus contortus infection

The impact of Haemonchus contortus infections on nitrogen retention (NR) of hair sheep lambs is unknown. This study estimated the feed intake, digestibility, NR, haematocrit (HT), and their relationship with the gradient of H. contortus infection in hair sheep lambs. Twenty-four hair sheep lambs, 3–4 months old, reared parasite-free were used (live weight (LW) 16.7 ± 1.7 kg). Six lambs were kept parasite-free, nine lambs received a dose of 300 H. contortus infective larvae (L3)/kg LW, and the remaining nine lambs received 500 H. contortus L3/kg LW. Infection doses ranged from 3870 to 9,500 L3. Lambs were individually fed for an average daily gain (ADG) of 100 g. On days 1 (P < 0.01) and 7 (P < 0.001) post-infection (PI), the L3 doses were positively associated with HT, possibly due to platelet recruitment. On week 1 PI, the infection (L3) reduced the crude protein (CP) intake (g/kg metabolic LW) (P < 0.05). A reduction of 1% HT corresponded to 1200 eggs per gram of faeces (EPG) for day 21 PI (P < 0.05), 2300 EPG for day 28 PI (P < 0.001), 2400 EPG for day 35 (P < 0.001), and 1300 EPG for day 41 PI (P < 0.001). However, the HT levels were never lower than 21 %. A lower CP digestibility was associated with EPG only on week 5 PI (P < 0.05). There was no significant association between EPG, Total egg in faeces, or worm burden (WB) with intake, dry matter digestibility (DMD), ADG or NR. The NR of lambs was positive along the different weeks of study irrespective of infection level. The WB was negatively associated only with HT on day 41 PI (P < 0.001), where a 1 % HT reduction was estimated for every 257 worms hosted. In conclusion, no relationship was found between H. contortus infection and DMD, ADG or NR in hair sheep lambs. The cost of H. contortus infection resulted only from the HT reduction and depended on the gradient and stage of the infection.

Genome-wide association study for residual concentrate intake using different approaches in Italian Brown Swiss

Residual feed intake (RFI) is the most used measure of feed efficiency. However, considering the importance of concentrates in the ration, a new index, the residual concentrate intake (RCI), was here defined. RCI aims to measure the individual efficiency in converting the concentrate into animal products. Brown Swiss young bulls (N = 736) were genotyped at 41,183 loci. Animals were housed in pens equipped with an automatic feeding system able to recognise the animal and record the concentrate intake. The diet consisted of concentrate and hay (ad libitum). The new RCI index was calculated as the residuals of the linear regression of concentrate intake on metabolic live weight and average daily gain. Animals were ranked according to their corrected RCI and divided into low (LRCI) and high phenotypes (HRCI). A low heritability (0.06 ± 0.03) was estimated using only genomics for this new index. Results from multivariate (M-GWAS) and Bayesian (B-GWAS) approaches were combined to identify SNP associated with RCI. The M-GWAS selected 698 SNPs potentially associated, whereas no significant markers were obtained in B-GWAS. Markers in the last approach were ranked according to their posterior inclusion probability and the first 698 were retained. Only SNPs in common between sorted B-GWAS and M-GWAS (N = 11) were considered associated with RCI. A total of 48 candidate genes were retrieved near these SNPs. Most of them were previously reported to be associated with feed efficiency and RFI. The combined use of multivariate and Bayesian techniques allow to identify SNPs associated with the investigated trait. Highlights RCI could be promising to select animals 48 candidate genes were found associated with RCI Multivariate technique allowed to identify significant SNPs

Feed efficiency and carcass metrics in growing cattle1.

Some definitions of feed efficiency such as residual energy intake (REI) and residual gain (RG) may not truly reflect production efficiency. The energy sinks used in the derivation of the traits include metabolic live-weight; producers finishing cattle for slaughter are, however, paid on the basis of carcass weight, as opposed to live-weight. The objective of the present study was to explore alternative definitions of REI and RG which are more reflective of production efficiency, and quantify their relationship with performance, ultrasound, and carcass traits across multiple breeds and sexes of cattle. Feed intake and live-weight records were available on 5,172 growing animals, 2,187 of which also had information relating to carcass traits; all animals were fed a concentrate-based diet representative of a feedlot diet. Animal linear mixed models were used to estimate (co)variance components. Heritability estimates for all derived REI traits varied from 0.36 (REICWF; REI using carcass weight and carcass fat as energy sinks) to 0.50 (traditional REI derived with the energy sinks of both live-weight and ADG). The heritability for the RG traits varied from 0.24 to 0.34. Phenotypic correlations among all definitions of the REI traits ranged from 0.90 (REI with REICWF) to 0.99 (traditional REI with REI using metabolic preslaughter live-weight and ADG). All were different (P < 0.001) from one suggesting reranking of animals when using different definitions of REI to identify efficient cattle. The derived RG traits were either weakly or not correlated (P > 0.05) with the ultrasound and carcass traits. Genetic correlations between the REI traits with carcass weight, dressing difference (i.e., live-weight immediately preslaughter minus carcass weight) and dressing percentage (i.e., carcass weight divided by live-weight immediately preslaughter) implies that selection on any of the REI traits will increase carcass weight, lower the dressing difference and increase dressing percentage. Selection on REICW (REI using carcass weight as an energy sink), as opposed to traditional REI, should increase the carcass weight 2.2 times slower but reduce the dressing difference 4.3 times faster. While traditionally defined REI is informative from a research perspective, the ability to convert energy into live-weight gain does not necessarily equate to carcass gain, and as such, traits such as REICW and REICWF provide a better description of production efficiency for feedlot cattle.

Is low-input dairy farming more climate friendly? A meta-analysis of the carbon footprints of different production systems

The global warming potential of milk production is a key aspect in the assessment of its eco-efficiency. The carbon footprint summarises the climate-relevant emissions of the production cycle, with this study focussing on the emissions from cradle to farm gate as boundaries. Numerous life cycle assessments were published in recent years, presenting the carbon footprint for different regions, production systems and management scenarios. However, despite the obvious high scientific interest in this topic, general conclusions on the climate-friendliness of contrasting production systems can hardly be drawn and there is no clear answer to the question of whether or not grazing systems provide an overall more climate-friendly alternative to confinement systems.To resolve this discussion, a meta-analysis was applied to a dataset, created with data from a selection of 30 published life cycle assessments, comprising in total 87 carbon footprint values from 15 different countries. After a standardisation process, three production system categories (pasture-based, mixed and confinement) were defined based on feeding parameters. Aside from the comparison of the production systems, the effects of various production variables (pasture and concentrate intake, milk yield per cow, milk yield per kg of metabolic live weight, mineral nitrogen fertilisation, feed efficiency and replacement rate) were analysed. Therefore, linear and level-log mixed models were developed and analyses of covariance performed. As the dataset used for the analysis covered a large range of different intensities per production system, the results are based on a robust analysis and can be extrapolated to any milk production system with known in- and outputs.The results show that increases in milk yield, pasture intake and feed efficiency decreased the carbon footprint of milk significantly, independent of the production system. However, the mitigation potential is limited across production systems with regard to their productivity thresholds. The comparison of the systems without consideration of other production parameters did not reveal any significant differences. When controlling for milk yield, however, the pasture-based system achieved lower carbon footprints compared to the other production systems. Thus, irrespective of the importance of milk yield for emissions and the generally lower milk yields of the pasture-based production system, this system still offers a competitive climate impact.

Studies on drinking water intake of fallow deer, sheep and mouflon under semi‐natural pasture conditions

AbstractThe aim of the investigation was to determine the water requirements of adult fallow deer (Dama dama), Skudde sheep (Ovis ammon) and mouflon (Ovis orientalis musimon) kept under the same conditions. This study was intended to allow the development of basic principles and recommendations for improving drinking water management in the production of fallow deer, sheep, and mouflon, taking into account the different reproductive statuses of these three species. At a fen, the water intake of the animals was recorded for three consecutive years (2011–2013) during the grazing period (1 May–31 October). The results were based on the regular measurement of the animals’ water intake under pasture management. Three herd repetitions were carried out per species during early and late summer and autumn. Each test group consisted of 10 adult female animals. To enable a comparison of the drinking water consumption among species of different weights, the water intake of each animal was converted into the water intake per kg of metabolic live weight (W0.75). During the early summer fallow deer and sheep consumed a similar amount of water. The mouflon had relatively low water consumption; in the late summer and autumn (September and October), these animals drank only sporadically. All three species consumed more water in the first 3 months of the grazing period than in the last 3 months. Daily water consumption by sheep and deer increased with heat stress caused by higher temperatures and relative humidity, whereas mouflon were relatively immune to such environmental influences. It is recommended that the small ruminant species investigated should be offered a constant supply of drinking water when under pasture management.

Inter-relationships among alternative definitions of feed efficiency in grazing lactating dairy cows

International interest in feed efficiency, and in particular energy intake and residual energy intake (REI), is intensifying due to a greater global demand for animal-derived protein and energy sources. Feed efficiency is a trait of economic importance, and yet is overlooked in national dairy cow breeding goals. This is due primarily to a lack of accurate data on commercial animals, but also a lack of clarity on the most appropriate definition of the feed intake and utilization complex. The objective of the present study was to derive alternative definitions of energetic efficiency in grazing lactating dairy cows and to quantify the inter-relationships among these alternative definitions. Net energy intake (NEI) from pasture and concentrate intake was estimated up to 8 times per lactation for 2,693 lactations from 1,412 Holstein-Friesian cows. Energy values of feed were based on the French Net Energy system where 1 UFL is the net energy requirements for lactation equivalent of 1kg of air-dry barley. A total of 8,183 individual feed intake measurements were available. Energy balance was defined as the difference between NEI and energy expenditure. Efficiency traits were either ratio-based or residual-based; the latter were derived from least squares regression models. Residual energy intake was defined as NEI minus predicted energy to fulfill the requirements for the various energy sinks. The energy sinks (e.g., NEL, metabolic live weight) and additional contributors to energy kinetics (e.g., live weight loss) combined, explained 59% of the variation in NEI, implying that REI represented 41% of the variance in total NEI. The most efficient 10% of test-day records, as defined by REI (n=709), on average were associated with a 7.59 UFL/d less NEI (average NEI of the entire population was 16.23 UFL/d) than the least efficient 10% of test-day records based on REI (n=709). Additionally, the most efficient 10% of test-day records, as defined by REI, were associated with superior energy conversion efficiency (ECE, i.e., NEL divided by NEI; ECE=0.55) compared with the least efficient 10% of test-day records (ECE=0.33). Moreover, REI was positively correlated with energy balance, implying that more negative REI animals (i.e., deemed more efficient) are expected to be, on average, in greater negative energy balance. Many of the correlations among the 14 defined efficiency traits differed from unity, implying that each trait is measuring a different aspect of efficiency.

Towards an improved estimation of the biological components of residual feed intake in growing cattle1

Residual feed intake (RFI) is the difference between observed and predicted feed intake. It is calculated as the residuals from a multiple regression model of DMI on the various energy expenditures (e.g., maintenance, growth, activity). Residual feed intake is often cited to be indicative of feed efficiency differences among animals. However, explaining a large proportion of the (phenotypic and genetic) interanimal variation in RFI remains difficult. Here we first describe a biological framework for RFI dwelling on similarities between RFI and energy balance. Alternative phenotypic and genetic statistical models are subsequently applied to a dataset of 1,963 growing bulls of 2 British and 3 Continental breeds. The novel aspect of this study was the use of a mixed model framework to quantify the heritable interanimal variation in the partial regression coefficients on the energy expenditure traits within the RFI equation. Heritable genetic variation in individual animal regression coefficients for metabolic live weight existed. No significant genetic variation in animal-level regression coefficients for growth or body fat level, however, existed in the study population. The presence of genetic variation in the partial regression coefficient of maintenance suggests the existence of interanimal variation in maintenance efficiency. However, it could also simply reflect interanimal genetic variation in correlated energy expenditure traits not included in the statistical model. Estimated breeding values for the random regression coefficient could be useful phenotypes in themselves for studies wishing to elucidate the underlying mechanisms governing differences among animals in RFI.

Nutritional requirements of sheep, goats and cattle in warm climates: a meta-analysis

The objective of the study was to update energy and protein requirements of growing sheep, goats and cattle in warm areas through a meta-analysis study of 590 publications. Requirements were expressed on metabolic live weight (MLW=LW0.75) and LW1 basis. The maintenance requirements for energy were 542.64 and 631.26 kJ ME/kg LW0.75 for small ruminants and cattle, respectively, and the difference was significant (P<0.01). The corresponding requirement for 1 g gain was 24.3 kJ ME without any significant effect of species. Relative to LW0.75, there was no difference among genotypes intra-species in terms of ME requirement for maintenance and gain. However, small ruminants of warm and tropical climate appeared to have higher ME requirements for maintenance relative to live weight (LW) compared with temperate climate ones and cattle. Maintenance requirements for protein were estimated via two approaches. For these two methods, the data in which retained nitrogen (RN) was used cover the same range of variability of observations. The regression of digestible CP intake (DCPI, g/kg LW0.75) against RN (g/kg LW0.75) indicated that DCP requirements are significantly higher in sheep (3.36 g/kg LW0.75) than in goats (2.38 g/kg LW0.75), with cattle intermediate (2.81 g/kg LW0.75), without any significant difference in the quantity of DCPI/g retained CP (RCP) (40.43). Regressing metabolisable protein (MP) or minimal digestible protein in the intestine (PDImin) against RCP showed that there was no difference between species and genotypes, neither for the intercept (maintenance=3.51 g/kg LW0.75 for sheep and goat v. 4.35 for cattle) nor for the slope (growth=0.60 g MP/g RCP). The regression of DCP against ADG showed that DCP requirements did not differ among species or genotypes. These new feeding standards are derived from a wider range of nutritional conditions compared with existing feeding standards as they are based on a larger database. The standards seem to be more appropriate for ruminants in warm and tropical climates around the world.

Effect of sainfoin (Onobrychis viciifolia) and faba bean (Vicia faba) on the periparturient rise in ewes infected with gastrointestinal nematodes

Previous research has demonstrated the potential of tanniniferous feed sources to reduce the faecal egg count (FEC) of sheep and lambs infected with gastrointestinal nematodes (GIN). The present study investigates the use of sainfoin (Onobrychis viciifolia, cv. Perly) and faba bean seeds (Vicia faba, cv. Scirocco), either as single condensed tannin sources or in combination, to reduce the periparturient rise in the faecal egg count of GIN-infected ewes. Seventy-eight periparturient Red Engadine ewes (PP ewes) and fifteen ewes of the same breed in early gestation (EG ewes) were used for the study. All animals experienced an artificial infection with 1500 infectious larvae of Haemonchus contortus 33 days prior to lambing. For a feeding period of 25 days, PP ewes were allocated to four groups that were balanced with regard to FEC, number of foetuses and age. PP ewes were fed with either (i) a ryegrass-clover forage, C (n=21); (ii) a sainfoin forage, S (n=19); (iii) a combined condensed tannin feed consisting of sainfoin forage and faba bean pellets, SB (n=19); or (iv) faba bean pellets and ryegrass-clover forage, B (n=19). The diets of PP ewes were supplemented with commercial concentrates to balance the protein and energy intake between groups. EG ewes were used to determine the dimension of the periparturient rise in groups i–iv. During the 25 day feeding period, faecal sampling took place every third or fourth day. Individual FECs were expressed per gramme faecal dry matter (FECDM). Compared to the control group (C), the differences in FECDM over the entire feeding period were −54.7% (S), −40.0% (SB), +7.8% (B) and −41% (EG). A mixed model analysis revealed significant differences between the C and S groups (p<0.001) and between the C and SB groups (p<0.001) but revealed no difference between the C and B groups (p=0.766). The mean daily ingestion of condensed tannins in groups S, SB, and B per kg metabolic live weight was 3.50±0.91g, 3.61±0.89g and 0.43±0.06g, respectively. We conclude that condensed tannins originating from sainfoin prevented periparturient egg rise, whereas those from faba beans did not produce such an effect.

Consumo alimentar e sua predição pelos sistemas NRC, CNCPS e BR-Corte, para tourinhos zebuínos confinados

Objetivou-se avaliar a predição de consumo de matéria seca (CMS) pelos sistemas CNCPS 5.0, NRC e BR-CORTE, bem como o consumo de nutrientes por tourinhos zebuínos confinados. Foram utilizados 44 animais em delineamento experimental inteiramente casualizado, sendo: 19 Nelore PO, 7 Nelore LA, 10 Tabapuã PO e 8 Guzerá PO, com peso vivo inicial médio de 394 ± 39; 348 ± 33; 346 ± 28 e 340 ± 30 kg, respectivamente, e idade inicial média de 13 meses. O período experimental foi de 84 dias. O consumo alimentar individual foi obtido com o uso dos indicadores LIPE®, óxido crômico e fibra em detergente ácido indigestível (FDAi). Para comparação do CMS predito pelos sistemas com o observado utilizou-se análise de regressão linear. Os animais Nelore LA apresentaram os menores valores observados para CMS (kg d-1). Ao avaliar o CMS em porcentagem do peso vivo (%PV) e em gramas por quilo de peso vivo metabólico (g kg-1 PM), foi detectada diferença entre os grupos genéticos, sendo que os maiores valores ocorreram para os animais Tabapuã PO e Guzerá PO. Os sistemas NRC, CNCPS 5.0 e o BR-CORTE apresentaram subpredição do CMS. Conclui-se que os sistemas estudados não se mostraram adequados para predizer o consumo de matéria seca em tourinhos zebuínos confinados.

Development of mathematical models to predict dry matter intake in feedlot Santa Ines rams

Mathematical models to predict the dry matter intake (DMI) of feedlot Santa Ines rams were developed and evaluated in this study. The available database had 100 experimental units from 13 studies. Study effect was integrated and random effects of their interactions as components of a hybrid model. The independent variables were initially adjusted to a model which included fixed effects for y-intercept and slope and random effects in y-intercept and slope study, using unstructured covariance model (e.g.: UN-unstructured). Study effect on database was verified, and then a meta-analysis procedure to develop DMI prediction equations was performed. For validation and comparisons between existing prediction equations in the national and international literature, independent data from one survey with 21 animals were used. Validation methods of the observed and predicted DMI were based on linear regression model adjustment of the observed values over predicted values. The following variables: average live weight (ALW), metabolic live weight (MLW0.75), average daily gain (ADG) and average daily gain2 (ADGsq) presented positive correlation with DMI. In contrast diet concentrate level showed a negative correlation. Among eight models examined, the following resulting equation [DMI (g/day)=238.74±114.56 (0.0398)+31.3574±4.2737 (<0.0001)×MLW+1.2623 ±0.2128 (<0.0001)×ADG−5.1837±0.7448 (<0.0001)×CON] has been found as the best fit model to predict DMI in feedlot Santa Ines rams.

Effect of barley and oats on feed intake, live weight gain and some carcass characteristics of fattening lambs

The influence of whole, crushed and ground barley and oats on intake, performance and carcass characteristics of lambs was examined. A comparison of diets was conducted with individually-fed male and female lambs in six groups. The study was repeated in three successive years (1995–1997) using the same experimental design. A total of 192 lambs of a mean initial age of 74 days (SD 13.0) and live weight 20.6kg (SD 4.54) were daily fed their respective concentrates, 72g dry matter (DM)/kg metabolic live weight (kgW0.75), for 98 days from weaning to slaughter. Hay was provided ad libitum.The lambs adapted more quickly to diets containing barley than to those containing oats. Compared to oats, the total daily DM intake was higher on barley (1162 vs. 990g DM/lamb, 89 vs. 78g DM/kgW0.75, P<0.001). Hay consumption was significantly lower on oats than on barley (182 vs. 344g DM/day, P<0.001). On oats the lambs experienced energy and protein deficiencies with their energy and protein intakes being 20% below feeding recommendations. On the barley diets the energy and protein requirements of the lambs were satisfied. When processed cereals were offered, there was no increase in the total DM, energy or protein intakes. Processing did not improve the organic matter digestibility of barley or oats.The growth rate (P<0.01), carcass weight (P<0.001) and slaughter percentage (P<0.001) were higher on a barley diet than on oats. A barley diet resulted in more kidney fat (P<0.01) and fattier carcasses. Processing had no positive influence on the live weight gain. On the contrary, lambs receiving crushed or ground barley or oats had a lower final live weight than those receiving whole grains (P<0.001). The utilisation of whole grain was more efficient than that of processed grain. There were no advantages in processing barley and oats for the feeding of lambs.

Effects of breed and age on the performance of crossbred hill ewes sourced from Scottish Blackface dams

The aim of this study was to evaluate the effects of age and breed on the reproductive performance and lamb output of crossbred hill ewes relative to purebred Scottish Blackface (BF). BF ewes were compared alongside Swaledale (SW) × BF, North Country Cheviot (CH) × BF, Lleyn (LL) × BF and Texel (T) × BF ewes on six commercial hill farms across Northern Ireland, on which all the ewes were born and reared. Ewes were mated to a range of sire breeds, balanced across breeds, for up to five successive breeding seasons. Mature live weight of adult BF, SW × BF, CH × BF, LL × BF and T × BF ewes was 52.8, 54.9, 60.3, 55.6 and 58.6 kg (P < 0.001), respectively. Compared with the pure BF, the number of lambs born per ewe lambed was higher with LL × BF and SW × BF (P < 0.05), whereas the number of lambs weaned per ewe lambed was greater for LL × BF and T × BF (P < 0.01). Total litter weight at birth of all the crossbred ewes was heavier (P < 0.01) than the pure BF, except in primiparous 2-year-old ewes. Lambs born to CH × BF and T × BF dams were 0.24 to 0.35 kg heavier at birth (P < 0.01) than the other ewe breeds, whereas lambs born to CH × BF, LL × BF and T × BF dams were, on average, 1.7, 1.3 and 1.5 kg, respectively, heavier (P < 0.01) at weaning than those from BF dams due to their higher (P < 0.05) average daily gain. Compared with the pure BF, total weaned lamb output per ewe lambed was 3.7, 4.8, 6.7 and 5.4 kg heavier (P < 0.05) for SW × BF, CH × BF, LL × BF and T × BF, respectively. However, as a result of the heavier live weight of the crossbred ewes, production efficiency (lamb output per kilogram live weight (W) and lamb output per kilogram metabolic live weight (W0.75)) was higher (P < 0.001) for LL × BF ewes only. For all ewe breeds, litter size at birth per ewe lambed, total lamb birth weight per ewe lambed and litter size at weaning increased (P < 0.001) with age up to 5 years, but decreased in 6-year-old ewes. Average lamb weaning weight and total weaned lamb output per ewe lambed increased (P < 0.001) with age up to 4 years. Production efficiency of the 6-year-old ewes was lower (P < 0.01) than the younger ewes. This study shows that adopting a flock replacement policy based on crossing BF ewes with LL, SW, T and CH sires can lead to significant improvements in the productivity of hill flocks.

Effect of Cattle Genotype and Variable Feed Supply on Forage Intake and Digestibility

An experiment was carried out to investigate whether a local breed of cattle is better adapted than European breed crosses to low quality feeds and to variations in their supply. Four Red Chittagong (RC) and four Holstein cross Sahiwal (Hx) cattle were used to compare the intake and digestibility of German grass (Echinocloa crusgalli) and rice straw with four regimes of feed supply. These were; a choice of German grass and rice straw each offered ad libitum on the same day (A); German grass and rice straw offered ad libitum on alternate days (B); rice straw offered ad libitum for 5 days followed by German grass ad libitum for 5 days (C); and German grass offered ad libitum for 5 days followed by rice straw ad libitum for 5 days (D). Each breed was offered the treatments in a 4x4 Latin Square design. The German grass intake and total dry matter intake per kg metabolic live weight were significantly higher for the Hx than for RC, but there were no significant effects of genotype on digestibility of nutrients or live weight. Treatment A had the highest proportion of German grass relative to rice straw in the total DM intake, and had the highest total DM intake and apparent digestibility of nutrients compared with treatments B, C and D. It was concluded that there was no significant evidence that the RG cattle were better adapted to a variable supply of low quality feed than Hx cattle, and that the variable feed supply reduced the ability of cattle to select a preferred diet and consequently nutrient intake was depressed.

Comparison of Gayal (Bos frontalis) and Yunnan Yellow Cattle (Bos taurus): Rumen Function, Digestibilities and Nitrogen Balance during Feeding of Pelleted Lucerne (Medicago sativum)

Three male Gayal (Bos frontalis) and three male Yunnan Yellow cattle (Bos taurus) were fed pelleted lucerne and measurements made of digestibility, nitrogen utilisation, rumen fermentation and microbial population and key plasma metabolites. Total actual dry matter intake was similar but when expressed in terms of live weight or metabolic live weight feed intakes were significantly higher (p<0.05) for Gayal than cattle. Apparent digestibilities of dry matter, organic matter, fibre and dietary nitrogen were similar for both Gayal and cattle. Rumen ammonia nitrogen and total volatile fatty acids were significantly higher (p<0.05) for Gayal than cattle and total numbers of viable rumen bacteria, cellulolytic and amylolytic bacteria, but not proteolytic bacteria nor protozoa, were significantly greater (p<0.05) for Gayal than cattle. Although Gayal have a different rumen ecology to cattle, similar digestive parameters were exhibited. Further research is required to establish relationship between rumen ecology and digestive parameters.