Decreasing the Roughage: Concentrate Ratio of a Diet to Determine the Critical Roughage Part for Beef Cattle

The critical roughage part (CRP) of 2 diet types was determined in a cross-over design with 6 double-muscled and 6 normally conformated Belgian Blue bulls fitted with rumen cannulae. The roughage:concentrate ratio was lowered weekly until signs of a lack of physical structure were observed. For diet 1, consisting of maize silage and concentrates, the initial proportion of maize silage was 25% of DM but it decreased weekly with 5% units of DM. For the second diet, consisting of wheat straw and concentrate, 12% straw (DM basis) was provided during the first week and thereafter the proportion of straw decreased weekly with 3% units of DM. Several directly observable parameters (rumen pH, feed intake, bloat, faecal consistency) were evaluated weekly for each bull. Apart from these direct indicators of acidosis, also other parameters, whose results were only available after the end of the trial, were determined (volatile fatty acid profile, lactic acid concentration, chewing time). The roughage part between the part fed when signs of a lack of physical structure was first observed and the part that was fed the week before, was considered as the CRP. Most animals showed no acute signs of clinical acidosis (directly observable parameters) and finished the trial on a 100% concentrate diet. However, in sacco rumen DM-degradabilities of maize silage, grass silage and wheat grain was depressed considerably when low roughage diets were fed. Based on all observed parameters, the mean CRP was calculated to be 14.7% for diet 1 and 8.1% for diet 2. The beef type (double-muscled or not) had no influence on the CRP.     

Could cholesterol bound to haemoglobin be a missing link for the occasional inverse relationship between superoxide dismutase and glutathione peroxidase activities?

The concept of an anti-oxidant defence system as a means to prevent oxidative cell damage implies balanced activities of anti-oxidant defence enzymes. As well as positive correlations between anti-oxidant enzyme activities in human erythrocytes, it has been observed that sometimes when glutathione peroxidase activity is increased, CuZn-superoxide dismutase activity is decreased. In our current study we have examined the plasma lipid profile and the anti-oxidant defence enzymes in erythrocytes from humans, pigs, and bulls. We found that a negative correlation existed between CuZn-superoxide dismutase and glutathione peroxidase activities in human erythrocytes when the concentrations of both plasma triglycerides and total cholesterol were high. This correlation was also found in pig erythrocytes, but not in bull erythrocytes. We propose that cholesterol could affect membrane lipid peroxidation and superoxide generation in erythrocytes via the recently found fraction of cholesterol bound to haemoglobin, termed haemoglobin-cholesterol.     

The amino acid composition of meat and bone meals and its predictability

Für den vorliegenden Versuch wurden Jungbullen der Rasse Deutsches Fleckvieh ab einer Lebendmasse von 200 kg entweder mit hoher Energiezufuhr (Zunahmeniveau etwa 1200–1500 g täglich) oder mit begrenzter Energiezufuhr (Zunahmeniveau etwa 900 g täglich) versorgt. Bei 200 kg Lebendmasse (‐Versuchsbeginn), 350 kg, 500 kg, 575 kg und 650 kg wurden je neun Tiere der Schlachtung zugeführt und eine Schlachtkörperhälfte nach DLG‐Schnittführung in 13 Teilstücke zerlegt. Anschließend erfolgte eine grobgewebliche Trennung der Teilstücke in Muskel‐, Knochen‐ und Fettgewebe sowie Sehnen und eine Gesamtfett‐, Rohprotein‐ und Rohaschebestimmung in den Geweben der Teilstücke.

Die Unterschiede in der Rohnährstoffzusammensetzung der Gewebe aller Teilstücke spiegeln sich am deutlichsten in einer fütterungs‐ und masseabhängig differierenden Gesamtfetteinlagerung wider. Der mittlere Fettgehalt des Muskelgewebes aller Teilstücke erhöht sich bei den intensiv voersorgten Bullen deutlich von 1,8% (200 kg Lebendmasse) auf 3,5% (650 kg Lebendmasse), während der Anstieg bei begrenzter Enerigezufuhr sehr gering ist (2,3 %, 650 kg Lebendmasse). Dabei unterscheiden sich die fettreicheren Teilstücke (z.B. Dünnungen, Brust, Spannrippe, Bug oder Hochrippe) etwas stärker als die weiteren, fettärmeren Teilstücke. Dagegen ist der Rohprotein‐ und Rohaschegehalt mit mittleren Werten von 21,9 % bzw. 1,2 % des Muskelgewebes aller Teilstücke relativ unbeeinflußt von Fütterungsintensität und Mastendmasse.

Aber auch der Fettgehalt des Fettgewebes der Teilstücke erhöht sich von etwa 46 % (200 kg, Mastbeginn) auf knapp 70 % (Fütterung intensiv) bzw. 60 % (Fütterung begrenzt) bei Mastende (650 kg Lebendmasse) deutlich. Demgegenüber bleibt der mittlere Fettgehalt des Knochengewebes der Teilstücke mit etwa 15 % Fett von den Untersuchungsfaktoren weitgehend unbeeinflußt, jedoch differiert der mittlere Fettgehalt zwischen den Teilstücken von etwa 21 % (Keule, Vorder‐, Hinterhesse, Bug) bis 9 % (Dünnungen, Brust, Spannrippe) erheblich. Der Rohproteingehalt des Knochengewebes (im Mittel 21%) nimmt unbeeinflußt von der Fütterungsintensität mit zunehmender Lebendmasse etwas, der Rohaschegehalt deutlicher von knapp 21 % auf etwa 31 % zu. Die Unterschiede in den Rohaschegehalten des Knochengewebes zwischen den Teilstücken sind gering.     

Repercussions of growth path on carcass characteristics,meat colour and shear force in Alentejana bulls

The aim of this study was to evaluate the carcass and meat characteristics of eight muscles from bulls with distinct growth paths. A total of 40 Alentejana male calves were allocated to two distinct feeding regimes. In the continuous growth (CG) system, the animals were fed concentrates plus hay and were slaughtered at 18 months of age. On the other hand, in the discontinuous growth (DG) system, the animals were fed hay until 15 months of age; the cattle were then fed the same diet provided to the CG group from 15 to 24 months of age. The DG reduced hot carcass weight, fatness and dressing %, but the proportions of fat, bone and muscle tissues in the leg were not affected. In contrast, there was a positive impact of compensatory growth on supraspinatus, triceps brachii, semitendinosus, biceps femoris muscle tenderness, overcoming the negative effects of age at slaughter. The reasons for such improvement in meat tenderness were not related to intra-muscular fat content or myofibrillar protein degradation values. An association between tenderness and muscle collagen properties was not established. The results indicate that the compensatory growth has a muscle-dependent effect.     

Postpartum resumption of ovarian cycling activity in first-calf suckled beef cows exposed to familiar or unfamiliar bulls

The objective of this experiment was to determine if the proportion of first-calf suckled beef cows that resumed ovulatory cycles and the interval to resumption of ovarian cycling activity differ after exposure to either “unfamiliar” bulls or cows on d 35 postpartum, after exposure to either “familiar” bulls or cows for the first 30–32 d after calving. Fifty Angus × Hereford cows were stratified by calving date, calf BW, and calf sex by d 3 postpartum, and assigned to be exposed to familiar epididectomized bulls (BEF; n = 25) or familiar mature ovariectomized (OVX) cows (CEF; n = 25). On d 35 after calving, 12 BEF cows were assigned to be exposed to unfamiliar bulls (BEU); likewise, 12 CEF cows were assigned to be exposed to unfamiliar OVX cows (CEU). Cows were in their treatments for either 95 d (BEF and CEF) or 60 d (BEU and CEU) during the experiment. Blood samples were collected every third d from the beginning to the end of the experiment. A rise in progesterone concentration of >0.5 ng/mL in consecutive samples was used as the criterion for resumption of ovulatory cycles. Exposing cows to bulls on d 5 after calving and then switching a subset of these cows to be exposed to unfamiliar bulls 30–32 d later did not (P > 0.10) alter: (1) the proportion of cows that resumed cycling activity; and (2) postpartum interval to resumption of ovarian cycling activity compared to cows exposed to familiar bulls. However, 32% more (P < 0.05) cows exposed to bulls (BEF and BEU) resumed cycling activity by approximately 14.8 d before cows that were exposed to OVX cows (CEF and CEU). We conclude that the familiarity of first-calf cows to either bulls or ovariectomized cows, did not affect the postpartum occurrence of cycling activity or the interval from calving to resumption of ovulatory cycles. However, bull exposure, whether familiar or unfamiliar, stimulates first-calf cows to resume ovulatory cycles sooner after calving than if they are not exposed to bulls.     

Effect of cis-9,trans-11 and trans-10,cis-12 isomers of conjugated linoleic acid on the integrity and functionality of cryopreserved bovine spermatozoa

Plasma membranes of sperm subjected to low temperatures undergo changes in their structure and permeability. The addition of fatty acids in semen cryopreservation media may influence the sperm motility after thawing, possibly by maintaining the membrane fluidity due to their incorporation in lipid bilayers. In this work, different concentrations of the isomers cis-9,trans-11 and trans-10,cis-12 of conjugated linoleic acid (CLA) were added in the cryopreservation medium of bovine sperm. Four Jersey bulls were used, and the ejaculates were processed as a pool. The Tris-based extender (Dilutris®) was supplemented with 20% egg yolk (MB). The treatments with CLA (Luta-CLA®), which had oily presentation, were prepared from MB with addition of 1% sodium lauryl sulfate, and denominated MBL. The concentrations of CLA tested were 50, 100, and 150 μM. The motility characteristics of the post-thaw semen were analyzed by computerized analysis system (CASA), and plasma membrane integrity and acrosomal and mitochondrial function assessed by the association of the fluorescent probes propidium iodide, fluorescein isothiocyanate-conjugated Pisum sativum agglutinin (FITC-PSA), JC-1 and Hoechst 33342. No significant differences were observed among treatments, excepting for a decreased mitochondrial potential of cells treated with 150 μM CLA. The addition of CLA, at the concentrations used, showed no advantages on the integrity and functionality of bovine sperm submitted to cryopreservation.     

Feed Intake of Young Double-Muscled Bulls Fed on Grass and Supplemented with Sugar-Beet Pulp

Daily dry matter intake in young growing double-muscled bulls, fed indoors on grass, was estimated based on forty-four intake data from 28 animals, ageing at least five months and weighing up to 400kg live weight. Intake was measured during five consecutive days using one of eighteen cuts of grass. Fresh meadow grass (mainly Lolium perenne ) was fed ad libitum and twokg dried sugar-beet pulp was offered per animal and per day. Animal live weight averaged 278 ± 82kg and mean total daily dry matter intake amounted to 5.05 ± 1.59kg or 73.6 ± 13.7g perkg metabolic weight, while pulp dry matter intake amounted to 1.49 ± 0.50kg per day. Regression analysis showed that animal as well as feed characteristics could explain up to approximately 90% of the variation in daily dry matter intake. The supplementation resulted in an extra daily dry matter intake of 0.68g perg pulp dry matter. Intake of double-muscled animals was considerably lower than previously reported for non-double-muscled cattle. An extra supplementation of young grazing double-muscled animals could be advised from these findings, while extra protein should also be considered.