Forage-based Diets Research Articles

A universal equation to predict methane production of forage-fed cattle in Australia

The methods for estimating methane emissions from cattle as used in the Australian national inventory are based on older data that have now been superseded by a large amount of more recent data. Recent data suggested that the current inventory emissions estimates can be improved. To address this issue, a total of 1034 individual animal records of daily methane production (MP) was used to reassess the relationship between MP and each of dry matter intake (DMI) and gross energy intake (GEI). Data were restricted to trials conducted in the past 10 years using open-circuit respiration chambers, with cattle fed forage-based diets (forage >70%). Results from diets considered to inhibit methanogenesis were omitted from the dataset. Records were obtained from dairy cattle fed temperate forages (220 records), beef cattle fed temperate forages (680 records) and beef cattle fed tropical forages (133 records). Relationships were very similar for all three production categories and single relationships for MP on a DMI or GEI basis were proposed for national inventory purposes. These relationships were MP (g/day) = 20.7 (±0.28) × DMI (kg/day) (R2 = 0.92, P < 0.001) and MP (MJ/day) = 0.063 (±0.008) × GEI (MJ/day) (R2 = 0.93, P < 0.001). If the revised MP (g/day) approach is used to calculate Australia’s national inventory, it will reduce estimates of emissions of forage-fed cattle by 24%. Assuming a global warming potential of 25 for methane, this represents a 12.6 Mt CO2-e reduction in calculated annual emissions from Australian cattle.

A meta-analysis and meta-regression of the effect of forage particle size, level, source, and preservation method on feed intake, nutrient digestibility, and performance in dairy cows

A meta-analysis of the effect of forage particle size (FPS) on nutrient intake, digestibility, and milk production of dairy cattle was conducted using published data from the literature (1998–2014). Meta-regression was used to evaluate the effect of forage level, source, and preservation method on heterogeneity of the results for FPS. A total of 46 papers and 28 to 91 trials (each trial consisting of 2 treatment means) that reported changes in FPS in the diet of dairy cattle were identified. Estimated effect sizes of FPS were calculated on nutrient intake, nutrient digestibility, and milk production and composition. Intakes of dry matter and neutral detergent fiber increased with decreasing FPS (0.527 and 0.166kg/d, respectively) but neutral detergent fiber digestibility decreased (0.6%) with decreasing FPS. Heterogeneity (amount of variation among studies) was significant for all intake and digestibility parameters and the improvement in feed intake only occurred with decreasing FPS for diets containing a high level of forage (>50%). Also, the improvement in dry matter intake due to lowering FPS occurred for diets containing silage but not hay. Digestibility of dry matter increased with decreasing FPS when the forage source of the diet was not corn. Milk production consistently increased (0.541kg/d; heterogeneity=19%) and milk protein production increased (0.02kg/d) as FPS decreased, but FCM was not affected by FPS. Likewise, milk fat percentage decreased (0.058%) with decreasing FPS. The heterogeneity of milk parameters (including fat-corrected milk, milk fat, and milk protein), other than milk production, was also significant. Decreasing FPS in high-forage diets (>50%) increased milk protein production by 0.027%. Decreasing FPS increased milk protein content in corn forage-based diets and milk fat and protein percentage in hay-based diets. In conclusion, FPS has the potential to affect feed intake and milk production of dairy cows, but its effects depend upon source, level, and the method of preservation of forages in the diet.

Effects of grass forage species and long-term period of low quality forage diet feeding on growth performance, nutrient utilization and microbial nitrogen yield in growing wether lambs.

Six growing lambs were used to evaluate the feeding value of two forage-based diets in a long-term feeding period by measuring body weight (BW) gain, digestibility, nitrogen (N) retention and microbial N (MBN) yield. The animals were fed imported low-quality timothy hay (TH) with concentrate diet (THD) or imported low-quality Italian ryegrass straw (IR) with concentrate diet (IRD) for 9 months. The forages were offered at 2% BW, and concentrate was fed at 40% of forage intake. The BW gain averaged 82.6 and 66.2 g/day for THD and IRD, respectively, without showing significant difference. Average forage intake (% BW) was significantly greater for IR than for TH, although it was not affected by feeding periods. The digestibility did not differ between diets or periods. The numerically greater (P = 0.06) ratio of retained N to absorbed N for IRD than that for THD was prominent. Neither diet nor period had significant effect on MBN supply and efficiency of MBN synthesis. The results suggest that the IR-based diet can be also used for long-term periods of feeding to growing ruminant animals as a grass hay-based diet without any detrimental effects on nutrient utilization and growth performance.

The relationship of residual feed intake and visceral organ size in growing lambs fed a concentrate- or forage-based diet

We hypothesized that a portion of the individual differences observed for feed efficiency in ruminants can be attributed to gastrointestinal tract (GIT) size, which would vary based on diet type. The objective of this study was to determine GIT and visceral organ size in high and low efficiency growing lambs fed either a concentrate or forage-based diet. Growing wethers (n=82; 51.3±1.2kg body weight [BW]) were fed a concentrate (CONC; 12.1% crude protein [CP], 17.6% neutral detergent fiber [NDF], 2.98Mcal/kg metabolizable energy [ME]) or forage-based pelleted diet (FOR; 16.2% CP, 36.3% NDF, 2.31Mcal/kg ME) for 49d. Individual intake was measured with the GrowSafe System to determine residual feed intake (RFI). The 20% highest efficiency (low RFI, n=8) and 20% lowest efficiency (high RFI, n=8) lambs from each diet were slaughtered (66.6±2.3kg BW; n=32 total), and the viscera was dissected and weighed. Data were analyzed as a 2×2 factorial with RFI class (high efficiency vs. low efficiency), diet type (FOR vs. CONC), and their interaction in the model. Organ masses were not affected (P>0.10) by the RFI class x diet type interaction. High efficiency lambs tended to have greater (P=0.09) pancreas and spleen actual mass than low efficiency lambs, although RFI class did not affect (P>0.15) other organ actual (g) or relative (g/kg BW) mass. Lambs fed FOR had greater (P≤0.01) actual and relative reticulum, omasum, large intestinal, and kidney mass and tended to have greater (P≤0.09) actual and relative small intestinal masses compared with lambs fed CONC. However, lambs fed CONC had greater (P≤0.05) actual rumen, heart, liver, and relative rumen mass than lambs fed FOR. All other visceral organ masses were unaffected (P>0.11) by diet type. Diet type, RFI class, and their interaction did not affect small intestinal length (P>0.10). Results of this study suggest that visceral organ size in growing lambs is more affected by diet type than individual feed efficiency. Based on this data, pancreas and spleen sizes may play a role in efficiency of feed utilization in lambs, however.

Enteric methane production, rumen volatile fatty acid concentrations, and milk fatty acid composition in lactating Holstein-Friesian cows fed grass silage- or corn silage-based diets

The objective of this study was to determine the effects of replacing grass silage (GS) with corn silage (CS) in dairy cow diets on enteric methane (CH4) production, rumen volatile fatty acid concentrations, and milk fatty acid (FA) composition. A completely randomized block design experiment was conducted with 32 multiparous lactating Holstein-Friesian cows. Four dietary treatments were used, all having a roughage-to-concentrate ratio of 80:20 based on dry matter (DM). The roughage consisted of either 100% GS, 67% GS and 33% CS, 33% GS and 67% CS, or 100% CS (all DM basis). Feed intake was restricted (95% of ad libitum DM intake) to avoid confounding effects of DM intake on CH4 production. Nutrient intake, apparent digestibility, milk production and composition, nitrogen (N) and energy balance, and CH4 production were measured during a 5-d period in climate respiration chambers after adaptation to the diet for 12 d. Increasing CS proportion linearly decreased neutral detergent fiber and crude protein intake and linearly increased starch intake. Milk production and milk fat content (on average 23.4kg/d and 4.68%, respectively) were not affected by increasing CS inclusion, whereas milk protein content increased quadratically. Rumen variables were unaffected by increasing CS inclusion, except the molar proportion of butyrate, which increased linearly. Methane production (expressed as grams per day, grams per kilogram of fat- and protein-corrected milk, and as a percent of gross energy intake) decreased quadratically with increasing CS inclusion, and decreased linearly when expressed as grams of CH4 per kilogram of DM intake. In comparison with 100% GS, CH4 production was 11 and 8% reduced for the 100% CS diet when expressed per unit of DM intake and per unit fat- and protein-corrected milk, respectively. Nitrogen efficiency increased linearly with increased inclusion of CS. The concentration of trans C18:1 FA, C18:1 cis-12, and total CLA increased quadratically, and iso C16:0, C18:1 cis-13, and C18:2n-6 increased linearly, whereas the concentration of C15:0, iso C15:0, C17:0, and C18:3n-3 decreased linearly with increasing inclusion of CS. No differences were found in short- and medium-straight, even-chain FA concentrations, with the exception of C4:0 which increased linearly with increased inclusion of CS. Replacing GS with CS in a common forage-based diet for dairy cattle offers an effective strategy to decrease enteric CH4 production without negatively affecting dairy cow performance, although a critical level of starch in the diet seems to be needed.

Individual trans 18:1 isomers are metabolised differently and have distinct effects on lipogenesis in 3T3-L1 adipocytes.

The objective of this research was to study the metabolism of individual trans fatty acids (FAs) that can be found in ruminant fat or partially hydrogenated vegetable oils (PHVO) and determine their effects on FA composition and lipogenic gene expression in adipocytes. Differentiated 3T3-L1 adipocytes were treated with 200 µM of either trans-9-18:1, trans-11-18:1, trans-13-18:1, cis-9-18:1 or BSA vehicle control for 120 h. Trans-9-18:1 increased total cell FA content (µmole/well) compared to other FA treatments, which was mainly related to the accumulation of trans-9-18:1 in the cells. Adipocytes were able to desaturate a significant proportion of absorbed trans-11-18:1 and trans-13-18:1 (~20 and 30% respectively) to cis-9,trans-11-18:2 and cis-9,trans-13-18:2, whereas trans-9-18:1 was mostly incorporated intact resulting in a greater lipophilic index (i.e. decreased mean FA fluidity) of adipocytes. Trans-9-18:1 up-regulated (P < 0.05) the expression of lipogenic genes including acetyl-CoA carboxylase (1.65 fold), FA synthase (1.45 fold), FA elongase-5 (1.52 fold) and stearoyl-CoA desaturase-1 (1.49 fold), compared to the control, whereas trans-11-18:1 and trans-13-18:1 did not affect the expression of these genes compared to control. Our results suggest that the metabolism and lipogenic properties of trans-11-18:1 and trans-13-18:1, typically the most abundant trans FA in beef from cattle fed forage-based diets, are similar and are different from those of trans-9-18:1, the predominant trans FA in PHVO.

Short communication. Effect of concentrate supplementation and prolificacy on the productive and economic performance of autochthonous sheep breeds fed forage-based diets

Sheep farming systems in Spain are experiencing an intensification process, characterised by a general selection criteria of enhancing prolificacy in ewes, and by increasing indoor feeding with concentrates to the detriment of grazing. This study evaluated the effects of concentrate supplementation and prolificacy on productive and economic performance of a local sheep breed in different price scenarios. Ewes were fed forage hay ad libitum, without (in pre-partum period, PRE-HAY; and in post-partum period, POST-HAY) or with concentrates (300 g/d in pre-partum period, PRE-CON; and 750 g/d in post-partum period, POST-CON). The inclusion of concentrate during the pre-partum period (last 10 weeks of pregnancy) had no effect on the productive performance of the ewes. In contrast, the inclusion of concentrate in the post-partum period (6 weeks), resulted in greater milk yield (1009 vs. 1275 ± 89 g/d), lamb average daily gain (151±12 vs. 225±19 g/d) and lamb output (kg of lamb LW weaned). However, the greater productivity thanks to the use of concentrates did not always turn into greatest profitability, since the economic margin was highly influenced by the cost of the diet and extremely subjected to variability in price of concentrates. Hence, the inclusion of concentrates in sheep meat production was not always justified in economic terms. In conclusion, the use of concentrates should only be considered as long as prices of commodities remain low, and inadvisable when prices reach a certain threshold or are subject to certain volatility in markets.

Fatty Acid Profile Differences among the Muscle Tissue of Three Rodents (&lt;i&gt;Hydrochoerushydrochaeris&lt;/i&gt;, &lt;i&gt;Cuniculuspaca&lt;/i&gt; and &lt;i&gt;Caviaporcellus&lt;/i&gt;) and Onelagomorph (&lt;i&gt;Oryctolaguscuniculus&lt;/i&gt;)

The consumer demand for functional food with nutraceutical properties has increased in recent years, and the food’s fatty acid profile is one of the factors that define its potential value asa functional food. The aim of the present study was to compare fatty acids composition of semitendinosus muscle in two native rodents, the capybara (<i>Hydroahoerus hidrochaeris</i>) and lowland paca (<i>Cuniculus</i><i> </i><i>paca</i>) and two domesticated species, one rodent, the guinea pig (<i>Cavia</i><i> </i><i>porcellus</i>) and one lagomorph, the common rabbit (<i>Oryctolagus</i><i> </i><i>cuniculus</i>). The animals were fed with forage-based diet. The fatty acid composition in lyophilized tissue was determined by gas chromatography. The capybara, lowland paca and guinea pig had the highest levels of omega-3 (n-3) fatty acids, predominantly α-linolenic acid (p<0.05). The guinea pig and common rabbit showed a higher content of linoleic acid (18:2 n-6) (p<0.05). The n-6: n-3 fatty acids ratio was higher to the common rabbit (p<0.05) with 8.9, in contrast, capybara and lowland paca had the lowest ratio, with lower than zero values indicating a predominance of n-3 fatty acids. These results were presented without any diet manipulation. The guinea pig meat contained an adequate balance of n-6 to n-3 fatty acids (< 4) whereas in rabbit meat there was an excess of n-6 fatty acids. The capybara and lowland paca can be considered as sources of n-3 fatty acids, represented by α-linolenic acid (18:3 n-3). These results confirm that native species not subjected to genetic selection and intensive feeding, showed higher content of n-3 fatty acids.

Effects of duration of moderate increases in grain feeding on endotoxins in the digestive tract and acute phase proteins in peripheral blood of yearling calves

Effects of duration of grain feeding on the concentration of endotoxic lipopolysaccharide (LPS) in digesta throughout the digestive tract and on acute phase proteins and LPS in peripheral blood were determined in Holstein yearling calves. Twenty-five Holstein yearling steer calves received either a forage-based diet containing 92% hay and 8% of a mineral and vitamin pellet on a dry matter basis (CON) or a moderate-grain diet, obtained by replacing 41.5% of the hay in the forage-based diet with barley grain, for 3 (MG3), 7 (MG7), 14 (MG14), or 21 d (MG21) before slaughter. Immediately before slaughter, blood samples were collected from the jugular vein. Immediately after slaughter, digesta samples were collected from the rumen, jejunum, ileum, cecum, colon, and rectum. Rumen liquid digesta, digesta from the intestines, and peripheral blood plasma were analyzed for LPS. Peripheral blood plasma and serum were analyzed for the acute phase proteins amyloid A, haptoglobin, and LPS-binding protein. Feeding the grain diet increased the LPS concentration in rumen fluid linearly from 15,488 endotoxin units (EU)/mL for CON to 70,146 EU/mL for MG7. Concentrations of LPS in rumen fluid in MG14 and MG21 were 61,944 and 56,234 EU/mL, respectively, and did not differ. The LPS concentrations in jejunal digesta were much lower than that in digesta elsewhere in the digestive tract, which suggests that ruminal LPS is broken down in the abomasum or proximal jejunum. The concentration of digesta LPS in the ileum was higher than that of digesta elsewhere in the intestines and similar to that in rumen fluid. The duration of grain feeding increased the LPS concentration in digesta in the ileum and cecum and tended to increase that in the colon cubically. Concentrations of LPS in this part of the digestive tract were highest in the MG3 and MG21 groups. The highest concentrations of LPS in digesta in the cecum, colon, and rectum were 3.7, 3.8, and 5.6 times higher than that in CON, respectively. Grain feeding and the increase in LPS in digesta were not accompanied by an acute phase response or a detectable concentration of LPS in peripheral blood. The absence of LPS in peripheral blood and the lack of increase in acute phase proteins indicated that the grain feeding protocol used in the current study and the accompanying changes in LPS concentrations of the digesta did not result in systemic inflammation.

A meta-analytical evaluation of the regulation of voluntary intake in cattle fed tropical forage-based diets.

The objective of this work was to use a meta-analytical approach to evaluate the regulation of voluntary intake in cattle fed tropical forage-based diets using dietary digestibility and bulkiness. Treatment mean values were collected from 53 studies with lactating dairy cows and 126 studies with feedlot growing and finishing cattle that were published in Brazil from 1990 to 2012. In all studies animals were fed ad libitum with diets based on tropical forages. The dataset was analyzed according to meta-analysis techniques, using linear and nonlinear mixed models. The main independent variables were the D-value and the B-value of the diets. The D-value corresponds to the dietary content of digested OM and is associated with energy content of the diet. The B-value is defined as the undigested fraction of NDF and indicates bulkiness of the diet. The DMI presented significant associations with both D-value and B-value. In the first case, DMI intake responded quadratically to the D-value (P = 0.042). On the other hand, DMI decreased linearly as the B-value of the diet increased (P = 0.004). Two new variables called Di and Bi were created to express the intake in terms of D-value and B-value units. A conceptual explicative model was developed from Di and Bi. This model showed that DMI is simultaneously regulated by both physical constraints and metabolic feedbacks. There were differences in the intake pattern of lactating cows and growing cattle.

Performance of indigenous and exotic×indigenous sheep breeds fed different diets in spring and the efficiency of feeding system in crop–livestock farming

SUMMARYGenetic variation in feed efficiency may have a significant impact on sheep production in integrated crop livestock farming systems in dry areas, where the shortage and poor quality of feed is widespread. Thus, the present study was carried out to investigate the effects of sheep genotype and feed source on liveweight gain, feed conversion efficiency and dry matter (DM) intake in feedlot lambs finished on diets based on low-cost forages or a high-cost concentrated feed as a means of assessing the efficiency of this feeding system. Early weaned lambs of the purebred fat-tailed Akkaraman breed were compared with synthetic Anatolian Merino (0·80 German Mutton Merino×0·20 Native Akkaraman) breed. The lambs were kept in individual pens for 8 weeks and fed four diets: daily harvested forages of triticale (T), Hungarian vetch (HV), a triticale-Hungarian vetch mixture (T+HV), and a concentrate-based feed (CF). Lamb liveweight gain (LWG) was monitored during the early (18 April–16 May) and late (17 May–13 June) spring periods. Diet×period and diet×breed interactions were detected in LWG of the lambs. Lambs from both genotypes on the concentrate-based diet had higher liveweight gains, DM intakes and better feed conversion ratios compared with lambs finished on the forage-based diets. The LWG of lambs offered triticale forage decreased from 177 g/head/day in the early spring to 95 g/head/day in the late spring period, as plant maturity increased. Liveweight gains did not change for the other forage rations during the same period. The LWG of Akkaraman lambs were similar for both the early (189 g/head/day) and the late (183 g/head/day) spring periods, whereas Anatolian Merino lambs gained 41 g/head/day less LW and had 3·8 higher feed conversion rate for the late spring period compared with the early spring period. The present study showed that fat-tailed Akkaraman lambs were better able to utilize forages with low nutritive value compared to Anatolian Merino lambs, and may be better suited to semi-arid areas, where crop and livestock are highly integrated in the farming system.

Energy efficiency of growing ram lambs fed concentrate-based diets with different roughage sources

Poor-quality roughages are widely used as fiber sources in concentrate-based diets for ruminants. Because roughage quality is associated with the efficiency of energy use in forage-based diets, the objective of this study was to determine whether differing the roughage source in concentrate-based diets could change the energy requirements of growing lambs. Eighty-four 1/2 Dorper × 1/2 Santa Inês ram lambs (18.0 ± 3.3 kg BW) were individually penned and divided into 2 groups according to primary source of dietary roughage: low-quality roughage (LQR; sugarcane bagasse) or medium-quality roughage (MQR; coastcross hay). Diets were formulated to be isonitrogenous (2.6% N) and to meet 20% of physically effective NDF. After a 10-d ad libitum adaptation period, 7 lambs from each group were randomly selected and slaughtered (baseline). Twenty-one lambs in each diet group were fed ad libitum and slaughtered at 25, 35, or 45 kg BW. The remaining 28 lambs (14 from each diet group) were submitted to 1 of 2 levels of feed restriction: 70% or 50% of the ad libitum intake. Retentions of body fat, N, and energy were determined. Additionally, 6 ram lambs (44.3 ± 5.6 kg BW) were kept in metabolic cages and used in a 6 × 6 Latin square experiment designed to establish the ME content of the 2 diets at the 3 levels of DM intake. There was no effect of intake level on diet ME content, but it was greater in the diet with LQR than in the diet with MQR (3.18 vs. 2.94 Mcal/kg, respectively; P < 0.01). Lambs fed the diet with LQR had greater body fat (g/kg of empty BW) and energy concentrations (kcal/kg of empty BW) because of a larger visceral fat deposition (P < 0.05). Using a low-quality roughage as a primary source of forage in a concentrate-based diet for growing lambs did not change NEm and the efficiency of ME use for maintenance, which averaged 71.6 kcal/kg(0.75) of shrunk BW and 0.63, respectively. On the other hand, the greater nonfibrous carbohydrate content of the diet with LQR resulted in a 17% better efficiency of ME use for gain (P < 0.01), which was associated with a greater partial efficiency of energy retention as fat (P < 0.01). This increased nutritional efficiency, however, should be viewed with caution because it is related to visceral fat deposition, a nonedible tissue.

Methane emissions of dairy cows cannot be predicted by the concentrations of C8:0 and total C18 fatty acids in milk

Methane (CH4) emissions from dairy cows are technically difficult and expensive to measure. Recently, some researchers have found correlations between the concentrations of specific fatty acids in milk fat and the CH4 emissions from cows that could obviate the need for direct measurement. In this research, data on individual cow CH4 emissions and concentration of caprylic acid (C8:0) and total C18 fatty acids in milk were collated from eight experiments involving 27 forage-based diets and 246 Holstein-Friesian dairy cows. Linear regressions between CH4 and both C8:0 and total C18 in milk were produced for published data and used to calculate 95% prediction regions for a new observation. The proportion of observed methane emissions from eight experiments that fell outside the 95% prediction region was 27.6% for the C8:0 model and 26.3% for the total C18 model. Neither model predicted CH4 emission well with Lin’s coefficient of concordance of less than 0.4 and the Nash–Sutcliffe efficiency coefficient of approximately zero for both the C8:0 and total C18 models. In addition, general linear model analysis showed significant differences between experiments in their intercepts (P &lt; 0.001) and slopes (P &lt; 0.001). It is concluded that the relationships tested cannot be used to accurately predict CH4 emissions when cows are fed a wide range of diets.

Diet Alters Both the Structure and Taxonomy of the Ovine Gut Microbial Ecosystem

We surveyed the ruminal metagenomes of 16 sheep under two different diets using Illumina pair-end DNA sequencing of raw microbial DNA extracted from rumen samples. The resulting sequence data were bioinformatically mapped to known prokaryotic 16S rDNA sequences to identify the taxa present in the samples and then analysed for the presence of potentially new taxa. Strikingly, the majority of the microbial individuals found did not map to known taxa from 16S sequence databases. We used a novel statistical modelling approach to compare the taxonomic distributions between animals fed a forage-based diet and those fed concentrated grains. With this model, we found significant differences between the two groups both in the dominant taxa present in the rumen and in the overall shape of the taxa abundance curves. In general, forage-fed animals have a more diverse microbial ecosystem, whereas the concentrate-fed animals have ruminal systems more heavily dominated by a few taxa. As expected, organisms from methanogenic groups are more prevalent in forage-fed animals. Finally, all of these differences appear to be grounded in an underlying common input of new microbial individuals into the rumen environment, with common organisms from one feed group being present in the other, but at much lower abundance.

Effects of concentrate supplementation on forage intake, metabolic profile and milk fatty acid composition of unselected ewes raising lambs

The physiological response to concentrate supplementation in low milk potential ewe breeds has been scarcely studied. The aim of this experiment was to evaluate the effects of concentrate inclusion on feed intake, blood metabolites and milk yield and milk fatty acids (FA) composition of ewes raising lambs under forage-based diets. During the last 10 weeks of pregnancy (pre-partum period) and the 6 weeks of lactation (post-partum period), ewes were fed forage hay ad libitum with or without concentrate (inclusion of 300g/day in pre-partum period and 750g/day in post-partum) in a 2×2 factorial arrangement. The inclusion of concentrate did not affect the forage intake in pre-partum period (P>0.05), whereas during the post-partum feed intake was similar between treatments during weeks 1 and 2 of lactation, but thereafter it was greater in ewes receiving concentrate supplementation (P<0.05). The replacement rate was steady during the pre-partum period and it was not affected by concentrate supplementation or the number of carried foetuses (average 9.1±2.0%, P>0.05). During lactation, ewes supplemented with concentrate showed a replacement rate between 16% and 31%, being greatest during the first 3 weeks of lactation than afterwards (P<0.05). Concentrate supplementation during pregnancy did not affect subsequent milk yield (P>0.05) but this practice increased milk yield during lactation (P<0.05). The main milk FA groups did not differ between treatments (P>0.05) except PUFA n-3 content (P<0.001), which was greater in purely forage-fed ewes than in their concentrate-supplemented counterparts especially during early lactation (P<0.05). Likewise, the inclusion of concentrate in the diet hardly affected the blood energy metabolites concentration (P>0.05), except plasma β-hydroxybutyrate during the pre-partum period, which was greater in purely forage-fed ewes (P<0.05). In conclusion, the inclusion of concentrate in forage-based diets fed to unselected sheep breeds hardly affected forage intake but increased milk yield. During the last third of pregnancy, concentrate supplementation (300g/day) improved blood ketone status, whereas concentrate supplement (750g/day) during the 6 weeks of lactation did not improve the ewe nutritional status. A mild decrease in milk polyunsaturated fatty acids n-3 was observed due to concentrate feeding. In this context, concentrate supplementation should only be recommended to improve the nutritional status before lambing but this practice failed to counteract lactation demands during the post-partum period.

Effects of diet on casein and fatty acid profiles of milk from goats differing in genotype for αS1-casein synthesis

This study investigated the interactions between nutrition and the genotype at αS1-CN loci (CSN1S1) in goats, evaluating the impact of fresh forage-based diets and an energy supplement on the casein and fatty acid (FA) profiles of milk from Girgentana goats. Twelve goats were selected for having the same genotype at the αS2-CN, β-CN, and κ-CN loci and differing in the CSN1S1 genotype: homozygous for strong alleles (AA) or heterozygous for strong and weak alleles (AF). Goats of each genotype were divided into three groups and, according to a 3 × 3 Latin square design, fed ad libitum three diets: sulla fresh forage (SFF), SFF plus 800 g/day of barley (SFB), and mixed hay plus 800 g/day of barley (MHB). The SFB diet led to higher-energy intake and milk yield. The energy-supplemented diets (SFB, MHB) reduced milk fat and urea and increased coagulation time. The fresh forage diets (SFF, SFB) increased dry matter (DM) and crude protein (CP) intake and milk β-CN. Diet had a more pronounced effect than CSN1S1 genotype on milk FA profile, which was healthier from goats fed the SFF diet, due to the higher content of rumenic acid, polyunsaturated, and omega-3 FAs. The AA milk had longer coagulation time and higher curd firmness, higher short- and medium-chain FAs (SMFA), and lower oleic acid than AF milk. Significant diet by genotype interactions indicated the higher milk yield of AA goats than AF goats with the higher-energy SFB diet and the lower synthesis of SMFA in AF than in AA goats with the SFF diet.

Short-term digestible energy intake in captive moose (Alces alces) on different diets

Moose (Alces alces) are regularly described as problematic animals in captivity, mainly because of their particular digestive physiology and resulting feeding demands. According to the literature, moose regularly reject non-browse forages offered in captivity, which may indirectly lead to an overproportional ingestion of easily digestible feeds and thus chronic acidosis, which may in turn be the cause of their low life expectancy in captivity. By feeding experiments in four animals, this study aimed at testing whether maintaining moose on roughage-only diets appears feasible. The diets used consisted of the typical zoo ration with mixed feeds (including alfalfa hay), and exclusive diets of alfalfa hay, combinations of alfalfa hay and grass hay, alfalfa hay and grass hay and dried browse leaves, and dried browse leaves only. Whereas results confirmed that moose do not ingest grass hay in relevant amounts, digestible energy (DE) intake on alfalfa hay was, at 0.67 ± 0.15 DE MJ kg(-0.75) day(-1), above the estimated maintenance requirement of 0.6, and higher on the browse diets. At least for short-time periods, results contradict previous reports in the literature that alfalfa hay only is not a suitable maintenance diet for moose. At the same time the results promote feeding moose in captivity forage-based diets.

Effect of dietary potassium and anionic salts on acid–base and mineral status in periparturient cows

Dry cow diets based on grassland forage from intensive production contain high amounts of K and could be responsible for a reduced ability to maintain Ca homoeostasis. The aim of this study was to determine whether a moderate anionic salt supplementation to a forage-based pre-calving diet with varying native K content affects the mineral and acid-base status in transition cows. Twenty-four dry and pregnant Holstein cows, without antecedent episodes of clinical hypocalcemia, were assigned to two diets during the last 4 weeks before estimated calving date. Twelve cows were fed a hay-based diet low in K (18 g K/kg DM), and 12, a hay-based diet high in K (35 g K/kg DM). Within each diet, six cows received anionic salts during the last 2 weeks before the estimated calving day. After calving, all cows received the high K diet ad libitum. Blood samples were taken daily from day 11 pre-partum to day 5 post-partum. Urine samples were taken on days 7 and 2 pre-partum and on day 2 post-partum. The anionic salt did not alter feed intake during the pre-partum period. Serum Ca was not influenced by the dietary treatments. Feeding pre-partum diets with low K concentrations induced a reduced metabolic alkalotic charge, as indicated by reduced pre-partum urinary base-acid quotient. Transition cows fed the low K diet including anionic salts induced a mild metabolic acidosis before calving, as indicated by higher urinary Ca, lower urinary pH and net acid-base excretion. Although serum Ca during the post-partum period was not affected by dietary treatment, feeding a low K diet moderately supplemented with anionic salts to reach a dietary cation-anion difference close to zero permitted to obtain a metabolic response in periparturient cows without altering the dry matter intake.

Effects of feeding algal meal high in docosahexaenoic acid on feed intake, milk production, and methane emissions in dairy cows

This study examined effects on milk yield and composition, milk fatty acid concentrations and methane (CH4) emissions when dairy cows were offered diets containing different amounts of algal meal. The algal meal contained 20% docosahexaenoic acid (DHA) and cows were offered either 0, 125, 250, or 375g/cow per d of algal meal corresponding to 0, 25, 50, or 75g of DHA/cow per d. Thirty-two Holstein cows in mid lactation were allocated to 4 treatment groups, and cows in all groups were individually offered 5.9kg of dry matter (DM) per day of concentrates [683g/kg of cracked wheat (Triticum aestivum), 250g/kg of cold-pressed canola, 46g/kg of granulated dried molasses, and 21g/kg of mineral mix] and ad libitum alfalfa (Medicago sativa) hay. The algal meal supplement was added to the concentrate allowance and was fed during the morning and afternoon milking, whereas the alfalfa hay was fed individually in pens. Cows were gradually introduced to their diets over 7d and then fed their treatment diets for a further 16d. Dry matter intake and milk yield were measured daily, and milk composition was measured on a sample representative of the daily milk yield on Thursday of each week. For the last 2d of the experiment, cows were individually housed in respiration chambers to allow measurement of CH4 emissions. Dry matter intake, milk yield and milk composition were also measured while cows were in the respiration chambers. Cows ate all their offered concentrates, but measured intake of alfalfa decreased with increasing dose of DHA by 16.2, 16.4, 15.1, and 14.3kg of DM/d, respectively. Milk yield (22.6, 23.5, 22.6, and 22.6kg/cow per d) was not affected by DHA dose, but milk fat concentrations (49.7, 37.8, 37.0, and 38.3g/kg) and, consequently, milk fat yields (1.08, 0.90, 0.83, and 0.85kg/d) decreased with addition of DHA. The feeding of algal meal high in DHA was associated with substantial increases in the concentrations of DHA (0.04, 0.36, 0.60, and 0.91g/100g of milk fatty acids) and conjugated linoleic acid C18:2 cis-9,trans-11 (0.36, 1.09, 1.79, and 1.87g/100g of milk fatty acids). Addition of DHA did not affect total emissions of CH4 (543, 563, 553, and 520g/cow per d), nor emissions in terms of milk production (24.9, 22.1, 24.3, and 23.4g of CH4/kg of milk), but emissions were increased with respect to total intake (22.6, 23.5, 24.5, and 24.4g of CH4/kg of DM). These findings indicate that CH4 emissions were not reduced when dairy cows were fed a forage-based diet supplemented with DHA from algal meal.

Relationships among performance, residual feed intake, and temperament assessed in growing beef heifers and subsequently as 3-year-old, lactating beef cows1

Seventy-four beef heifers were used to evaluate relationships among performance, residual feed intake (RFI), and temperament measured as growing heifers (Phase 1) and subsequently as 3-yr-old lactating beef cows (Phase 2) in the same cohort. In both phases, females were housed in a covered facility and fed similar forage-based diets, and individual feed intakes, BW, BCS, chute scores (CS), exit velocities (EV), and pen scores (PS) were collected throughout the 70-d feeding trials. In Phase 2, cows were milked on trial d 14 (lactation d 28 ± 3.5) and trial d 70 (lactation d 84 ± 3.5) to determine energy-corrected milk (ECM) production. Ultrasonic backfat thickness (BF), and ribeye area (REA) were evaluated on d 0 and 70 of the trial in Phase 2. Heifers were ranked by RFI and placed into Low (<0.5 SD mean RFI; n = 27), Medium (within ± 0.5 SD; n = 23), and High (>0.5 SD mean RFI; n = 24) RFI groups. Body weight, BCS, and ADG were similar among all RFI groups; however, daily DMI differed for all groups (P < 0.01) and was greater (10.76 ± 0.24 kg/d) for High, intermediate (9.88 ± 0.25 kg/d) for Medium, and less (8.52 ± 0.23 kg/d) for Low RFI heifers. When cow performance was analyzed based on RFI rank as heifers, BW, BCS, ADG, RFI, d 14 and d 70 ECM, BF, and REA were similar among RFI groups; however, cows that were most efficient as heifers (Low) had decreased (P < 0.05) daily DMI values (10.30 ± 0.41 kg/d) compared with cows that ranked Medium (11.60 ± 0.44 kg/d) or High (11.50 ± 0.43 kg/d) as heifers. The Pearson rank correlation between Phase 1 and 2 RFI was r = 0.13 (P = 0.30), and Pearson rank correlations showed no relationship (P > 0.1) between RFI and temperament. Phase 1 CS was negatively associated with ADG in Phase 1 (r = -0.28; P = 0.02) and 2 (r = -0.32; P = 0.01), and positively associated with d 14 (r = 0.24; P = 0.04) and 70 (r = 0.25; P = 0.03) ECM. Phase 2 CS was negatively associated with Phase 2 ADG (r = -0.29; P = 0.01) and positively associated with d 14 (r = 0.46; P = 0.001) and 70 (r = 0.33; P = 0.004) ECM. Phase 2 PS also tended to be negatively associated with DMI in Phase 1 (r = -0.20; P = 0.096) and 2 (r = -0.20; P = 0.08). In this study, heifers that were most feed efficient subsequently consumed less feed as lactating cows and maintained similar performance. Feed efficiency was not associated with differences in temperament; however, more excitable females had poorer BW gains and tended to have reduced feed intakes but produced more ECM.