Intramuscular fatty acid composition of lambs given a tanniniferous diet with or without polyethylene glycol supplementation

The aim of this trial was to investigate the effects that dietary tannins have on lamb intramuscular fatty acids. Twenty-seven lambs were divided into three homogeneous groups: control group, receiving commercial concentrate based on maize; tannin group, fed a diet based on carob pulp (45% as fed basis); PEG group, receiving the same diet as the latter with addition of 42 g/kg of polyethylene glycol (PEG, a binding agent that eliminates the effects of condensed tannins). The duration of the trial was 45 d. Intramuscular fatty acids were measured in the longissimus dorsi muscle. The isomer cis-9 trans-11 of linoleic acid (conjugated linoleic acid or CLA) and linolenic acid were higher in the longissimus muscle fat from animals fed the control diet compared to the other groups (P < 0.0005); these fatty acids were higher in the fat from animals fed the carob diet supplemented with PEG compared to those fed the same diet without PEG (P < 0.05). trans-Vaccenic acid (C18:1 trans-11) was found at higher concentration in fat from control and PEG lambs compared to tannin lambs (P < 0.01); the CLA/C18:1 trans-11 ratio was lower in lambs fed control and PEG diets than in tannin-fed animals (P < 0.05).     

Meat quality of cryptorchid lambs grazing either dryland or irrigated perennial pasture with some silage supplementation

The meat quality of lambs grazed on perennial pasture (ryegrass Lolium perenne, cocksfoot, Dactylis glomerata and white clover Trifolium repens) was examined in three treatments; group 1 (S) lambs were grazed on dryland pasture for 30 days and then offered a supplement of pasture silage ad libitum until slaughter, 30 days later (n = 21). Lambs in group 2 (P) were grazed on dryland pasture throughout (n = 28) and those in group 3 (IP) on irrigated pasture (n = 28). Lambs in group IP had a significantly (p < 0.001) heavier pre-slaughter liveweight and hot carcass weight than lambs in the other two groups. There was no significant difference (p < 0.05) infatscore between groups or in GR when adjusted to a common carcass weight. For cold carcass weight (reduced sample) IP lambs were still significantly heavier than those from group P, but no different to those from group S (n = 15, 15 and 10, respectively). There was no significant difference between groups for measures of fatness or for m. longissimus thoracis et lumborum (LL) area when adjusted to a common carcass weight of 23.6 kg. There was a significant difference between (p < 0.001) treatments for pH, group P carcasses having higher pH values for the LL muscle, with no treatment effect on m. semimembranosus (SM) pH. Differences between groups for meat colour values (L (?), a (?), b (?)) showed no consistent trend and there was no significant difference (p > 0.05) between groups in tenderness of the LL and SM muscles as indicated by shear force values. Aroma of the loin meat from pasture-fed lambs (P) was considered significantly (p < 0.05) stronger than from lambs in groups S and IP (n = 6, all groups) and the flavour of samples from lambs in group P was significantly (p < 0.05) stronger than from lambs in group IP. Overall there was no significant (p < 0.05) difference in acceptability between groups. The results indicate that consumers would be unlikely to detect the differences identified by the panel and that pasture silage will not have an adverse effect on lamb eating quality.     

Carcass traits and meat quality of male lambs fed monensin or lasalocid

Male lambs, crossbred Merino × Ille de France, were fed a diet supplemented with 31 mg monensin or 32 mg lasalocid per kg of feed dry matter from an initial body weight of 23·6–23·9 kg to the slaughter weight of approximately 40 kg.

Carcass traits and meat quality were evaluated after slaughter; the values obtained were compared with those of the control group fed the same diet without the ionophore supplement.

There were few significant differences among the individual groups in carcass value, sensoric and technological properties of meat and of its composition. However, the lasalocid-fed group seemed to be somewhat better in muscling and in the composition of meat.     

Effect of vitamin E supplementation and diet on fatty acid composition and on meat colour and lipid oxidation of lamb leg steaks displayed in modified atmosphere packs

Groups of 8 lambs were allocated to one of five concentrate diets supplemented with all-rac-α-tocopheryl acetate containing 30 (C30), 60 (C60), 120 (C120), 250 (C250) and 500 (C500) mg/kg dry matter. Two other groups were fed grass silage and 400 g/day concentrate with 60 (S60) or 500 (S500) mg α-tocopheryl acetate/kg dry matter. Within diet, vitamin E level did not affect growth performance or carcass characteristics. Basal diet did not affect final live weight, conformation and fatness scores. M. semimembranosus from S lambs contained more α-tocopherol than that of C lambs on the same intake and by day 6 in MAP (75%O2/25%CO2) chroma and a* were below acceptable levels in C30 lambs. TBARS were higher in C30 and C60 muscle than in other treatments (P < 0.001) after 3 and 6 days display. Muscle fatty acid composition varied with basal diet but lipid oxidation depended more on vitamin E concentration with an initial concentration of 1.9 μg/g muscle preventing significant lipid oxidation.     

Performance of growing–fattening lambs fed whole cotton seed

Effects of diets containing increasing levels of whole cotton seed (WCS) on feed intake, liveweight gain, feed conversion, feeding margin and carcass characteristics were studied. Diets contained 0, 5, 10, 15, 20 and 30% WCS and were fed ad libitum to growing lambs for 54 days. All diets were approximately isonitrogenous (163–186 g crude protein kg⁻¹ dry matter) and isocaloric (19–20 MJ gross energy kg⁻¹ of dry matter). During the first 28 days, four groups of 10 Karagouniko male lambs with initial liveweights of approximately 17·6 kg were fed diets containing 0, 5, 10 and 15% WCS and then, for the next 26 days, diets containing 0, 10, 20 and 30% WCS, respectively. Lambs fed the 15–30% WCS diet ingested about 20 mg kg liveweight⁻¹ day⁻¹ of free gossypol. At 54 days and liveweights of approximately 34·7 kg, five lambs from each treatment were slaughtered and carcass data were collected. There were significant differences in feed intake, liveweight gain, cooler shrink, rumen contents, intestinal fat and liver weight among the lambs fed these diets. Cooler shrink and intestinal fat, and perirenal fat and the combined weight of intestinal and perirenal fat, were significantly (P < 0·05) correlated. Pelleting of the WCS diets reduced the concentration of free gossypol in these diets. It was concluded that WCS was satisfactory as a feed ingredient for growing sheep and can be incorporated into ruminant diets as a source of energy and protein. No indication of gossypol toxicity was detected. © 1998 Society of Chemical Industry     

Effect of transient early hyperthyroidism on onset of puberty in Suffolk ram lambs

The thyroid function and sexual development of eight 6-week-old Suffolk ram lambs were studied. The lambs were divided into either control or treatment groups and housed indoors. From 6 to 12 weeks of age, four lambs in the treatment group received 15 mg kg(-1) body weight per day of 6-propyl 2-thiouracil orally to suppress normal thyroid function. During the same period, thyroxine and tri-iodothyronine were injected s.c. at the rate of 8 and 16 microg kg(-1) body weight per day, respectively, to induce a hyperthyroid state. Four control lambs received sham injection and oral excipient. Concentrations of thyroxine, tri-iodothyronine, FSH, testosterone and insulin-like growth factor I were determined in blood collected by indwelling jugular catheters once a week, every 20 min from 09:00 to 15:20 h. Scrotal circumference was recorded each week. Semen collection was attempted by electro-ejaculation between weeks 17 and 36. Lambs were castrated at week 36 and testicular histology was examined. During the treatment period only, the concentration of thyroid hormones was higher in treated lambs than in controls (P < 0.05). From week 6 to week 9 only, concentrations of FSH in treated lambs were lower than in controls (P < 0.05). Insulin-like growth factor I concentrations were lower in treated lambs than in controls from week 10 to week 13 (P < 0.05). Frequency of testosterone pulses was higher (P < 0.01) in the treated lambs but concentrations were similar in the control and treated lambs throughout the experiment. Scrotal circumference was greater in treated lambs from week 26 to week 36 (P < 0.05). Treated lambs produced viable spermatozoa earlier than did control lambs. At week 36, sperm concentration in treated lambs was higher than in controls (P < 0.01) but semen volumes were similar (P > 0.1). Diameter of the seminiferous tubules in treated lambs was larger than in controls (P < 0.05). In conclusion, transient neonatal hyperthyroidism decreased FSH and insulin-like growth factor I concentrations temporarily, increased testosterone pulses and sperm production and advanced puberty in Suffolk ram lambs.     

Performance of growing–fattening lambs fed diets containing different proportions of cotton seed meal

A lamb feedlot study was conducted to evaluate the nutritional value of cotton seed meal (CSM) as compared with that of sunflower meal as protein supplements for growing lambs. Forty-five Karagouniko male lambs immediately after weaning, having an average liveweight of approximately 14.7 kg, were assigned randomly to one of three growing lamb rations. CSM substituted for sunflower meal in a growing–finishing feedlot diet at levels of 0, 10 and 20% to provide 0, 50 and 100% of supplemental protein requirement, respectively. Diets were fed ad libitum and water was offered freely. All diets were approximately isonitrogenous and isocaloric. After being fed for 61 days and having reached a liveweight of approximately 27.6 kg, five lambs from each treatment were slaughtered and carcass data were collected. No significant differences (P > 0.05) in feed intake or the weight increase of lambs were found among groups given the 0, 10 and 20% treatments, indicating that lambs utilized CSM as effectively as sunflower meal when fed on an equal crude protein and crude fibre basis. The dressing percentage of the cold carcass, but not the warm carcass, and intestinal content weight were significantly influenced (P < 0.05) by the diet. Cooler shrink and intestinal fat, and perirenal fat and the combined weight of intestinal and perirenal fat were significantly (P < 0.05) correlated. Feeding margin was highest for the control diet, intermediate for the 10% CSM diet and lowest for the 20% CSM diet. It was concluded that CSM is accepted readily by growing sheep and can be incorporated into diets as a source of supplemental protein for growing–fattening lambs. No evidence of gossypol toxicity was noted. © 1999 Society of Chemical Industry     

Ensiled diet containing processed municipal garbage and sorghum forage for heifers.

Diets of similar proximate analysis formulated with a base of sorghum forage and primarily supplemented with equivalent dry matter of 18.4% of aerobically digested municipal garbage (garbage diet) or 17.5% of cottonseed hulls (control diet) were ensiled for 52 days and then individually and group fed to 16 dairy heifers for 56 and 35 days. Apparent digestibility of dry matter, crude protein, ether extract, crude fiber, and nitrogen-free extract in garbage and control diets averaged 54.2 and 47.4, 50.0 and 41.3, 62.0 and 65.1, 53.1 and 42.3, and 61.8 and 54.5% as determined by chromium oxide technique. Potential advantages from digestibility of the garbage diet appeared to be nullified by a 12% depression of dry matter intake and a consequent deterioration of feed efficiency. Dry matter intakes of garbage and control diets during the 56-day comparison were 1.98 and 2.25% of body weight and daily gains of .42 and .57 kg required 13.9 and 11.8 kg dry matter per kilogram of gain. Over the 91 days of combined comparison feeding, the .62 kg of average daily gain from control diet was 32% above the .47 kg from the garbage diet.     

Growth, carcass and meat characteristics of Karayaka growing rams fed sugar beet pulp, partially substituting for grass hay as forage

Twenty-one growing male Karayaka sheep were divided into three groups of seven at 12 months of age. All groups received a commercial feed (60%) and roughage (40%). One group received grass hay as roughage (control, C), the other two groups received a mixture in which 40 (0.40SBP) or 60% (0.60SBP) sugar beet pulp (SBP) was used in partial replacement of grass hay in the C group during 56 days. Dry matter (DM) intake and DM conversion index (kg DM per kg weight gain) of the C group were higher (P<0.01) than that of the 0.40SBP and 0.60SBP groups. While the 0.60SBP increased (P<0.05) the L* of meat from the Karayaka young rams, the 0.40SBP or 0.60SBP decreased the ultimate pH (P<0.05) and cooking loss (P<0.01) compared to the C group. Means for redness (a*), yellowness (b*), Hue (H*) and Chroma (C*) and sensory characteristics indicated that there were no significant differences between dietary treatments. Inclusion of 60% SBP increased the palmitic (P<0.02) and linoleic (P<0.01) acid contents of the meat, it decreased (P<0.01) stearic, oleic and arachidonic acid contents compared to the C group. The 0.40SBP also increased (P<0.01) the linoleic acid content of the meat, but it decreased (P<0.01) stearic and arachidonic acid contents compared to the control. Although meat from young rams fed 0.60SBP diet had a higher value of lightness and linoleic acid, and a lower value of cooking loss than those from animals fed the C diet, sensory evaluation did not discriminate the meat from young rams fed with control and/or SBP diets. Therefore, grass hay can be replaced by 60% of SBP in the growing diet for Karayaka rams without a reduction in meat quality.     

The effects of live yeast supplementation to dairy cows during the hot season on production, feed efficiency, and digestibility

The current study examined the effects of live yeast (LY) supplementation to dairy cows during the summer season on milk production, feed efficiency and ration digestibility. Forty-two dairy cows (14 primiparous and 28 multiparous) were fed either a control lactating diet or supplemented with 1 g of LY (Saccharomyces cerevisiae, Biosaf, Lesaffre) per 4 kg of dry matter consumed. The LY amounts were adjusted twice a week. Four rumen samples were taken from 30 cows in 2-h periods and ammonia concentrations were determined. Fecal grab samples from 30 cows were collected during 3 consecutive days, to determine the apparent digestibility of diets. The daily dry matter intake in the LY group was 2.5% greater compared with the control group (24.7 and 24.1 kg, respectively). The daily average milk yield of the LY group was greater by 1.5 kg (4.1%) compared with the control group (37.8 vs. 36.3 kg, respectively). There were no significant differences in the milk fat and protein percentages, but fat yield was greater in the LY group than in the control. The fat-corrected milk 4% was 2.0 kg (6.1%) greater in the LY group than in the control group (34.8 vs. 32.8 kg, respectively). The efficiency of using dry matter to produce 4% fat-corrected milk was 3.7% greater in the LY group compared with the control group. The ruminal ammonia concentrations after feeding were greater in the control group than in the LY group (151.9 vs. 126.1 mg/l, respectively). No differences were observed among groups in the total tract apparent digestibility of dry matter and other diet components. The pH values in the rumen that were determined in a companion trial using 4 fistulated cows tended to be higher in cows that were supplemented with LY than in the control (6.67 vs. 6.54, respectively). It may be concluded that LY supplementation to dairy cows during the hot season improved the rumen environment in a way that increased the dry matter intake and in consequence enhanced the productivity and efficiency.     

Meat quality of wether lambs grazed on either saltbush (Atriplex nummularia) plus supplements or lucerne (Medicago sativa)

The meat quality of 42, 8 month-old cross-bred wether lambs that had been grazed on either predominantly saltbush (Atriplex nummularia) and supplemented with pasture hay (n=14) or oat grain (n=14) for 68 days was compared to lambs grazed predominantly on lucerne (Medicago sativa; n=14). The lambs used in the study ranged in un-fasted liveweight from 44.5 to 63.6kg pre-slaughter. There was no significant (p>0.05) difference between the treatments for liveweight, but there was a significant (p<0.05) treatment effect on hot carcass weight with those from the saltbush/hay group (SH) being lighter than those from the lucerne group. When the carcass measures of fatness or m. longissimus thoracis et lumborum area were adjusted to a common carcass weight of 22.4kg there was no difference between groups. There were no significant differences (p>0.05) between groups for pH or colour values (where L* indicates relative lightness, a* indicates relative redness and b* indicates relative yellowness). There was no significant difference (p>0.05) between groups for b(2)* values of subcutaneous fat. Treatment had a significant effect on aroma strength (p<0.05), samples from lambs in the SH group (n=10) and those in saltbush/grain (SG) group (n=10) having a stronger aroma than those from lambs grazed on lucerne (L; n=10). No treatment effect for liking of aroma was found. Flavour strength was not significantly (p>0.05) stronger for samples from groups SH and SG than for samples from group L. There was no effect of treatment on tenderness or juiciness and overall panellists ranked the samples similarly for acceptability. Finishing lambs on saltbush and either supplemented with hay or grain as used in this experiment did not present any apparent meat quality problems compared to lucerne fed lambs.     

VITAMIN E SUPPLEMENTATION EFFECTS ON COLOR AND LIPID STABILITY OF WHOLE AND GROUND LAMB

Crossbred wethers averaging 44.1 kg were fed a diet supplemented with 2000 IU α-tocopheryl acetate/day for 49 days. The controls received the same diet without supplement. Muscles from lambs supplemented with vitamin E contained higher concentrations of a-tocopherol than the controls (P<0.05). There were no differences between control and supplemented animals for myoglobin stabiliry of two muscle slices stored at 4C (P>0.05). Ground semimembranosus (SM)from supplemented animals exhibited higher "a" values and lower Hue angle values (P < 0.05) than meat from control animals at 6 days of storage and longer indicating enhanced color stability due to vitamin E. Vitamin E supplementation decreased lipid oxidation of ground SM at 3, 6, 9, and 12 days of storage at 4C (P < 0.05) and it partially stabilized color of ground lamb. Color stability of whole lamb slices was not affected by vitamin E supplementation.     

Effect of Quillaja saponaria dietary administration on colour, oxidative stability and volatile profile of muscle longissimus dorsi of Barbarine lamb

Eighteen Barbarine lambs were assigned during 77days to three dietary treatments (n=6): control, oat hay ad libitum and 400g of concentrate; QS60 and the QS90 control diet supplemented with 60mg and 90mg Quillaja saponaria (QS) bark extract/kg dry matter, respectively. The analysis of pre-frozen longissimus dorsi muscle showed that the QS90 treatment reduced meat redness (a*) and saturation (C*) measured after 2h of blooming. It also reduced the rate of decrease in a* values (P=0.02) during 14days of refrigerated storage. Supplementation with QS extended meat colour stability by reducing (P<0.05) the rate of increase in hue angle (H*) values. Neither the rate of metmyoglobin accumulation at the meat surface nor lipid peroxidation over storage duration differed between treatments. The overall meat volatile compound profile was similar between the groups. We conclude that supplementing QS affects meat colour development at the meat surface and extends its stability without producing detrimental effects on meat volatile compounds.     

Effect of concentrate level and slaughter body weight on growth performances,carcass traits and meat quality of Barbarine lambs fed oat hay based diet

This study was conducted to evaluate concentrate level (CL) and slaughter body weight (SW) effects on growth performances, carcass traits and meat quality of Barbarine lambs. Twenty-four weaned male lambs (23.1 kg), receiving an oat-hay based diet, were allotted into two groups. The LCL group received low concentrate level (300 g) and the HCL group received high concentrate level (600 g). Lambs were slaughtered at two prefixed weights (35 and 42 kg). For each group and each weight, six lambs were slaughtered. Lambs from HCL group had higher ADG, carcass yields, carcass compactness and subcutaneous fat thickness, and lower carcass meat proportion. CL increase did not affect meat pH, meat and fat color, chemical and fatty acid composition. Late slaughtering improved carcass yields and increased carcass adiposity. However, it did not affect carcass meat proportion and shoulder tissue composition. SW had effect on meat color and fatty acid composition.     

Effect of growth path on the tenderness of the semitendinosus muscle of Brahman-cross steers

The growth paths of 36, nine-month-old Brahman-cross steers were modified to determine the effect of their growth history on tenderness of the semitendinosus (ST) muscle. Steers were assigned to one of three treatment groups. One group of steers (uninterrupted group) was grazed on improved tropical pasture for 257 days and had an average weight gain of 0.6 kg day(-1). The other two groups were fed a restricted diet of low-quality grass hay and lost on average ~ 13% of their initial live weight over 100 days. These groups were then regrown for 157 days on either pasture (pasture finished) with the uninterrupted group, or on a grain-based feedlot diet (grain finished). Growth rates of the previously restricted groups during the regrowth phase were indicative of compensatory growth and were significantly different (p < 0.05) at 0.76 (sem 0.03) kg day(-1) and 1.22 (0.05) kg day(-1), pasture and grain finished groups, respectively. Growth rates for both restricted groups were significantly different (p < 0.05) from the uninterrupted group [0.55 (0.02) kg day(-1)]. At slaughter, the grain finished group had heavier carcases, higher dressing percentages and more fat coverage, than either the uninterrupted or pasture finished groups, the latter being significantly lighter than the uninterrupted group. Tenderness was assessed by shear, compression (C) and adhesion (ADH) measurements. Shear peak force (PF) values of cooked ST samples did not differ significantly between groups. However, PF values of pressure-heat treated ST samples from the grain finished group were significantly less (p < 0.05) than comparable values from the uninterrupted group suggesting a reduced contribution of connective tissue to toughness. The pasture finished group mean PF value was not significantly different from either the uninterrupted group or grain finished group means. C and ADH values were significantly less (p < 0.05) in the grain finished group compared to the pasture finished groups values, again indicating a reduced connective tissue contribution to toughness. We conclude that the physical properties of the connective tissue component of the ST muscle may be altered by rapid compensatory growth after a weight loss phase and reduce the connective tissue contribution to toughness which may enhance meat tenderness.     

Effects of milk replacer feeding rate and long-term antibiotic inclusion in milk replacer on performance and nutrient digestibility of Holstein dairy calves up to 4 months of age

The objectives of this study were to evaluate calf performance and diet digestibility when feeding a milk replacer (MR; 25% crude protein, 18% fat, dry matter basis) at a moderate (MOD) and high (HI) rate, along with MOD with neomycin-oxytetracycline inclusion (1.43 each g/kg; NTMOD). Male Holstein calves (n = 48; 45 ± 1.0 kg of body weight; 3 to 4 d of age) were housed in individual pens for 56 d. All calves were initially fed 0.66 kg of dry matter from MR for the first p.m. and following a.m. feeding, then randomly assigned to 1 of 2 feeding programs: (1) 0.66 kg of dry matter/d for first 39 d divided into 2 equal a.m. and p.m. meals and 0.33 kg for 3 d fed once daily in the a.m. feeding only (MOD, NTMOD); (2) 0.85 kg of dry matter/d for the first 4 d divided into 2 equal a.m. and p.m. meals, 1.07 kg of dry matter/d for the next 31 d divided into 2 equal a.m. and p.m. meals, and 0.48 kg for 7 d fed once daily in the a.m. feeding only (HI). Calves were fed a textured starter containing whole grains (20% crude protein, 43% starch, dry matter basis). Fecal samples were collected for 5 individual calves per treatment between d 47 to 51 to estimate digestibility. Calves were moved into groups by treatment (4 calves/pen) at 56 d and fed the same starter blended with 5% hay until d 112. Data were analyzed as a completely randomized design with repeated measures when applicable using mixed models. Milk replacer dry matter intake averaged 27.4 kg for MOD and NTMOD and 40.3 kg for HI per calf. Preweaning starter intake was less for calves fed HI versus MOD. Preweaning calf BCS change was greater for calves fed HI versus MOD. Preweaning medical treatment days were fewer for calves fed NTMOD versus MOD. Postweaning starter intake was less for calves fed HI versus MOD. Postweaning average daily gain was less for calves fed NTMOD versus MOD. Over the 56-d nursery trial, calves fed HI had less starter intake than calves fed MOD. Digestibility of dry matter, organic matter, acid detergent fiber, and neutral detergent fiber were greater for calves fed MOD versus NTMOD or HI during d 47 to 51 postweaning. Additionally, digestibility of fat was greater for calves fed MOD versus HI. During d 56 to 112, hip width change was greater for calves fed MOD versus NTMOD or HI. Over 0 to 112 d, body weight gain was 100, 98, and 102 kg, whereas hip width change was 10.2, 9.0, and 9.2 cm for calves fed MOD, NTMOD, and HI, respectively. Any preweaning improvements from feeding NTMOD or HI over MOD were lost during the postweaning period, which could be partially explained by reductions in diet digestibility.     

Effects of bovine somatotropin on milk yield and composition in Holstein cows in advanced lactation fed low- or high-energy diets

The objective of this study was to evaluate the response of Holstein cows to bovine somatotropin (bST) during advanced lactation and its relationship to energy intake. Twenty-four lactating Holstein cows averaging 21 kg of milk/d, and 292 d in milk were assigned to one of three treatment groups in a randomized block design. Blocks were based on the 14 d of pretreatment milk production, and treatment groups were balanced for days in milk. Treatment 1 was a low-energy diet (1.49 Mcal/kg of dry matter) without bST injection; treatment 2 was the low-energy diet plus injection of 500 mg of bST every 14 d; and treatment 3 was a high-energy diet (1.71 Mcal/kg of dry matter) with bST injections as in treatment 2. Treatment was divided into two periods (1 to 49 and 50 to 98 d) to determine if response to bST and energy changed with time on treatment. Results showed that bST significantly (P < 0.05) increased milk, fat-corrected milk, and fat and protein yields; and feed efficiency (fat-corrected milk per dry matter intake) for both periods. Milk yield responses to bST were greater for cows fed the low-than the high-energy diet in both periods. These data show that bST injections for cows in advanced lactation increased performance, but excessive energy diminished the bST response.     

Effect of feeding restricted amounts of a medium- and high-protein diet on growth and body composition of ducklings

A total of 216 ducklings of mixed sex were fed diets containing either 19.5 or 24.7% crude protein, either to appetite or to 85% of appetite, from 1 to 21 or 24 days of age. There were no significant interactions between dietary protein content and level of feeding. At 21 days ducklings fed the high-protein diet were 28% heavier than those fed the medium-protein diet and birds fed the higher level of intake were 17% heavier than restricted groups. At 24 days the body weight of restricted ducklings was similar to that of those fed the higher level of intake at 21 days. From 1 to 21 days efficiency of food utilisation was better for ducks fed the high rather than the medium protein diet, but similar for the two levels of food intake. Efficiency of the restricted groups in the 1 to 24 days period was slightly worse than that of groups of similar body weight fed the higher level of intake from 1 to 21 days. At 21 days carcasses of ducklings fed the high protein diet contained 31% dry matter, of which 34% was fat and 53% was protein, compared with 34% dry matter in the carcasses from the medium protein groups, of which 41% was fat and 48% was protein. Feed restriction had no effect on carcass dry matter and the reduction in percentage ether extract was only about half the magnitude of the reduction due to dietary protein level. Dietary treatments had no significant effect on percentage protein in fat-free dry matter. At 24 days carcasses of restricted ducklings contained more dry matter but the proportions of ether extract and crude protein were similar to those in younger (21 days) ducklings of similar body weight fed at the higher level of food intake.     

Rate of carcass components gain, carcass characteristics, and muscle longissimus tenderness in lambs fed dietary protein sources with a low quality roughage diet

An experiment was conducted to examine the effects of infrequently fed (twice/week) protein supplements on rate of carcass components gain, carcass traits and tenderness of meat in lambs. Forty-three Dorset Horn×Merino wether lambs (aged 4 months) were assigned by stratified randomization (live weight basis) to five dietary treatments to compare the results with lambs fed very low quality (5.1 MJME/day) roughage diet. Lambs on control diet (BAS; treatment 1) and all other dietary treatment groups were offered ad libitum amounts of a mixed roughage diet (oat hay:lucerne hay) at the ratio of 85:15 throughout the 10-week experimental study. Supplements of barley grain with added urea and sulphate (USB, 226 g DM/day; treatment 2); lupins (LUP, 231 g DM/day; treatment 3); cottonseed meal (CSM, 152 g DM/day; treatment 4); fish meal (FM, 97 g DM/day; treatment 5) were offered at isonitrogenous amounts. Final live weight (FLW) and empty body weight (EBW) were greater (P<0.01) with FM, LUP, USB and CSM when compared with BAS. Rates of gain of carcass components observed during the experimental period resulted in lower carcass fatness (P<0.05) and greater muscle content (P<0.01) with FM; and higher (P<0.05) level of fat and muscle in the carcass with LUP compared to those on BAS diet. Other diets (USB and CSM) had less marked effects, but higher rate of daily fat gain in the carcass with LUP and CSM was indicated by greater carcass fat depth (P<0.05; the total tissue depth of muscle and fat at the twelfth rib, 110 mm from the midline; GR) and content of intramuscular fat (P<0.05), respectively. Energy gained as fat in the carcass was lowest with FM (P<0.05), highest with BAS and intermediate with all other treatments. The increase in carcass leanness and reduction in fatness with FM and USB compared to BAS and other treatments affected neither (P>0.1) meat tenderness (Warner-Bratzler shear force) nor sarcomere length of longissimus thoracis muscle. Feeding small amounts of protein supplements to lambs on very low quality forage diets during dry seasons may be a viable path to improve the carcass weight and leanness in lambs without changing the meat tenderness.     

A high dose of monensin does not reduce methane emissions of dairy cows offered pasture supplemented with grain

The primary objective of our research was to determine the effect of a high dose of monensin supplementation on enteric CH₄ emissions of dairy cows offered a ryegrass pasture diet supplemented with grain. An additional objective was to evaluate effects on milk production and rumen function, because a commensurate improvement in milk production could lead to adoption of monensin as a profitable strategy for methane abatement. Two experiments were conducted (grazing and respiratory chambers) and in both experiments monensin (471 mg/d) was topdressed on 4 kg (dry matter)/d of rolled barley grain offered in a feed trough twice daily at milking times. In the grazing experiment, 50 Holstein-Friesian cows were assigned randomly to 1 of 2 groups (control or monensin). Cows grazed together as a single herd on a predominantly ryegrass sward and received monensin over a 12-wk period, during which time measurements of milk production and body weight change were made. The SF₆ tracer technique was used to estimate methane production of 30 of the 50 cows (15 control cows and 15 monensin cows) for 3 consecutive days in wk 3, 5, 8, and 12 of treatment. Samples of rumen fluid were collected per fistula from 8 of the 50 cows (4 per diet) on 2 consecutive days in wk 3, 5, 8, and 12 of treatment and analyzed for volatile fatty acids and ammonia-N. In the metabolic chamber experiment, 10 pairs of lactating dairy cows (control and monensin) were used to determine the effects of monensin on methane emissions, dry matter intake, milk production, and body weight change over a 10-wk period. Methane emissions were measured by placing cows in respiration chambers for 2 d at wk 5 and 10 of treatment. Cows received fresh ryegrass pasture harvested daily. Monensin did not affect methane production in either the grazing experiment (g/d, g/kg of milk) or the chamber experiment (g/d, g/kg of dry matter intake, g/kg of milk). In both experiments, milk production did not increase with addition of monensin to the diet. Monensin had no effect on body weight changes in either experiment. Monensin did not affect volatile fatty acids or ammonia-N in rumen fluid, but the acetate to propionate ratio tended to decrease. Monensin did not improve milk production of grazing dairy cows and no effect on enteric methane emissions was observed, indicating that monensin cannot be promoted as a viable mitigation strategy for dairy cows grazing ryegrass pasture supplemented with grain.