Modelling the lactation curve of dairy cows using the differentials of growth functions

Descriptions of entire lactations were investigated using six mathematical equations. comprising the differentials of four growth functions (logistic. Gompertz, Schumacher and Morgan) and two other equations (Wood and Dijkstra). The data contained monthly milk yield records from 70 first, 70 second and 75 third parity Iranian Holstein cows. Indicators of fit were model behavior, statistical evaluation and biologically meaningful parameter estimates and lactation features. Analysis of variance with equation, parity and their interaction as factors and with cows as replicates was performed to compare goodness of fit of the equations. The interaction of equation and parity was not significant for any statistics, which showed that there vas no tendency For one equation to fit a given parity better than other equations. Although model behaviour analysis showed better performance of growth functions than the Wood and Dijkstra equations in filling the individual lactation curves, statistical evaluation revealed that there was no significant difference between file goodness of fit of the different equations. Evaluation of lactation features showed that the Dijkstra equation was able to estimate the initial milk yield and peak yield more accurately than the other equations. Overall evaluation of the different equations demonstrated the potential of the differentials of simple empirical growth functions used in file Current study as equations for fitting monthly milk records of Holstein dairy cattle

Effect of fibrolytic enzyme products at different levels on in vitro ruminal fermentation of low quality feeds and total mixed ration

This study aimed to evaluate the effects of cellulase and xylanase plus enzymes on in vitro ruminal fermentation of Eragrostis curvura hay, maize stover and a total mixed ration (TMR) at six levels of application. The feed samples were incubated for 2, 12, 24, 32, 48, 72, h in an in vitro batch culture with buffer and ruminal fluid, and the fibrolytic enzymes associated with the six levels of application. Gas production was measured using a pressure transducer connected to a data tracker. Degradability of fiber was measured after 48 hrs of incubation. Increased level of enzyme inclusion increased the volume of gas, the total volatile fatty acid (VFA) production and fibre disappearance, but the rate of increment associated with each mg of additional enzyme application was reduced beyond 1-2mg/g DM. Considering the enzymes cost and their efficiency at different rates on gas production and NDF degradability the medium levels of applications (1-2mg/g DM) were found to be the most efficient.The project was financed partly byIAEA through grant received by University of Pretoria as part of research contract No. SAF 16326. Additional funding was provided by the National Research Foundation, South Africa.http://www.thejaps.org.pk/hb201

Effects of Exogenous Cellulase Source on In Vitro Fermentation Characteristics and Methane Production of Crop Straws and Grasses

In vitro fermentation experiments were conducted to investigate the effects of 3 sources of exogenous cellulase products (EC) at 4 dose rates (DR) (0, 12, 37 and 62 IU/g of DM) on degradation of forage and methane production by mixed rumen micro-organisms of goats. The maximum gas production (Vf) of grasses was higher (P<0.001) in Neocallimastix patriciarum (NP) group than those in Trichoderma reesei (TR) and Trichoderma longibrachiatum (TL) groups. Quadratic increases in dry matter degradation (DMD) of forage and neutral detergent fiber (NDFD) of straw were observed for all EC, with optimum DR in the low range. Supplementation of EC originated from TR and NP increased (P<0.001) DMD of forage compared to that from TL. Addition of EC originated from TR and NP also decreased pH value, ammonia nitrogen (NH3-N) and methane (CH4) production compared to that from TL. Quadratic decreases in pH value, NH3-N and CH4 of forage were noted for EC of TR and NP, and with optimum DR in the low range. For short chain fatty acid, the EC of NP increased total volatile fatty acid (TVFA) and acetate concentration and the ratio of acetate to propionate of forage compared with EC of TL and TR, and with optimum DR in the low to medium range. It was concluded that the source of EC differed in fiber degradation and methane emission, and with optimum DR of TR in the low range (from 12 to 37 U/g DM) in improving fiber degradation and decreasing methane emission

The Effects of Replacing Dicalcium Phosphate with Busumbu Rock Phosphate on Performance and the Mechanical Properties of Bone in Growing Chicks

Three hundred, day-old broiler chicks, with an average initial weight of 41.8±1.79 g, were used in a 15-day study (10 birds per battery cage) to characterize their performance and fluorine status when dicalcium phosphate (DCP) was replaced by Busumbu rock phosphate (BRP) as the source of phosphorus in the chicks' ration. The treatments comprised a standard ration with BRP replacing 0, 25%, 50%, 75% or 100% of DCP. Replacing DCP with BRP significantly reduced the final weight of the chicks (p<0.01), feed intake (p<0.01), weight gains (p<0.01) and dry matter digestibility (p<0.05) but increased (p<0.05) the feed-to-gain ratio. True phosphorus absorption and the percentage of phosphorus in the tibia were not affected by increasing amounts of BRP in the diet. Increasing levels of BRP in the diet linearly reduced (p<0.01) the percentage bone ash, calcium, Ca:P ratio, ultimate breaking force, bending moment, stress, and modulus of elasticity. Leg stiffness, lameness, reduced feed intake, and a decline in general health were recorded in 10–40% of the chicks on 75% and 100% BRP, respectively. These results suggest that excessive ingestion of fluorine from the BRP caused the reduction in the chicks' performance

Effects of Schizochytrium microalgae and sunflower oil as sources of unsaturated fatty acids for the sustainable mitigation of ruminal biogases methane and carbon dioxide

Biogases produced during ruminant production needs to be reduced. The Food and Agriculture Organization (FAO) estimated CH4 production from livestock to contribute about 18% of all greenhouse gas emissions, while carbon dioxide (CO2) accounted for about 9% of the emission (FAO, 2006). Besides, these gases including CH4, CO2, and H2 are produced during ruminal fermentation and cause losses amounting to 2e12% of dietary energy in ruminants (Johnson and Johnson, 1995). Furthermore, these emissions have been implicated in causing climate change. Yeast, organic acids salt, exogenous enzymes, and essential oils have been used as new strategies to mitigate the production of ruminal methane from ruminants (Elghandour et al., 2016, 2017; Hernandez et al., 2017).Mitigation of methane (CH4) and carbon dioxide (CO2) emissions as well as ruminal fermentation parameters of a total mixed ration in the presence of Schizochytrium microalgae (SA) and sunflower oil (SO) or their mixture (SASO) as unsaturated fatty acid sources was investigated. Rumen liquor from two rumen cannulated Holstein steers and two rumen cannulated Creole goats was used as inoculum. Interactions between inoculum source additive type, and inoculum source additive type dose were observed for gas, CH4 and CO2 production and fermentation parameters. Additives affected the fermentation parameters in a dose-dependent manner. With goats’ inoculum, the inclusion of SO (1, 2, 4, 5%), SA (2, 3, 5%) and SASO (1, 3%) increased gas production (GP) and decreased the rate of GP, while with the steer inoculum, SO at 1 and 4% increased GP and the rate of GP. All levels of SA and SASO decreased the asymptotic GP and increased the rate of GP. The goat inoculum decreased CH4 at different doses of SO, SA and SASO whereas the steer inoculum decreased CH4 production. At all doses, additives decreased fermentation pH, protozoal counts, and increased ammonia-N, DM degradability and total bacterial counts. Sunflower oil (i.e., SO) at 1e3%, SA at 1e2%, and SASO at 1e2% were the most efficacious in the nutrition of goats, compared with SO at 1 to 2 in steers. The results suggest that Schizochytrium microalgae and sunflower oil could be a valuable means of sustainably mitigating CH4 and CO2 emissions for improved environmental conditions

The effects of supplementing Napier grass (Pennisetum purpureum) with rock phosphate and steamed bone meal compared with a commercial mineral mix on phosphorus absorption in cattle

Twelve Boran steers with a mean live weight of 215.8 ± 13.9 kg were used in an incomplete Latin Square experiment to compare the apparent phosphorus (P) absorption in cattle when Napier grass (Pennisetum purpureum) was supplemented with Busumbu rock phosphate (BRP), Minjingu rock phosphate (MRP), steamed bone meal (SBM) or a commercial mineral mix (CMM). The steers were housed individually and supplemented with P at 0, 4.5 or 17.5 g P/day. Dry matter intake (DMI) and dry matter digestibility (DMD) were not affected (p > 0.05) by the source of Live weight gains (LWG) were different (p 0.05) across periods. The level of P supplementation had no significant effect (p>0.05) on DMI or LWG. However, increasing the level of P supplementation significantly increased (p 0.05) different from each other. These results suggest that BRP has potential as a source of P for ruminants

Aspects of rumen microbiology central to mechanistic modelling of methane production in cattle

Methane, in addition to being a significant source of energy loss to the animal that can range from 0·02 to 0·12 of gross energy intake, is one of the major greenhouse gases being targeted for reduction by the Kyoto protocol. Thus, one of the focuses of recent research in animal science has been to develop or improve existing methane prediction models in order to increase overall understanding of the system and to evaluate mitigation strategies for methane reduction. Several dynamic mechanistic models of rumen function have been developed which contain hydrogen gas balance sub-models from which methane production can be predicted. These models predict methane production with varying levels of success and in many cases could benefit from further development. Central to methane prediction is accurate volatile fatty acid prediction, representation of the competition for substrate usage within the rumen, as well as descriptions of protozoal dynamics and pH. Most methane models could also largely benefit from an expanded description of lipid metabolism and hindgut fermentation. The purpose of the current review is to identify key aspects of rumen microbiology that could be incorporated into, or have improved representation within, a model of ruminant digestion and environmental emissions

Effects of exogenous enzymes on in vitro gas production kinetics and ruminal fermentation of four fibrous feeds

This study was conducted to investigate effects of increasing doses: 0 (control), 6 (low), 12 (medium) and 24 (high) mg/g DM of ZADO® enzyme preparation mixture (ENZ) on in vitro gas production (GP) and some ruminal fermentation parameters of the fibrous feeds Saccharum officinarum (leaves), Andropogon gayanus (leaves), Pennisetum purpureum (leaves) and Sorghum vulgare (straw). Rumen liquor was obtained from two Brown Swiss cows fitted with permanent rumen cannulae fed a total mixed ration of a 500:500 commercial concentrate and alfalfa hay ad libitum. The GP was recorded at 2, 4, 6, 8, 10, 12, 24, 48, 72 and 96 h of incubation. After 96 h, the incubation was stopped and the pH of the mixture was determined and filtrate used to determine dry matter degradability (DMD), partitioning factor (PF96), gas yield (GY24), in vitro organic matter digestibility (OMD), metabolizable energy (ME), short chain fatty acids (SCFA), and microbial crude protien production (MCP). In general, the crude protein (CP) content of the fibrous feeds was low and ranged from 23 g/kg DM (S. officinarum) to 44 (A. gayanus). The fibre contents (i.e., NDFom and ADFom) were highest (P<0.05) in S. officinarum. Increasing ENZ dose linearly increased (P<0.05) GP of all fibrous feeds and had a quadratically increased (P<0.05) asymptotic gas production in P. purpureum and S. vulgare and rate of gas production in S. officinarum and S. vulgare. Addition of ENZ also quadratically increased (P<0.05) GP at all incubation times in S. officinarum and S. vulgare, and A. gayanus, but only at 72 h in A. gayanus. The parameters of ruminal fermentation of OMD, ME, GY24 and SCFA linearly increased (P<0.05) and MCP linearly decreased (P<0.05) with the ENZ addition. Addition of enzyme affected ruminal fermentation of our feeds differently, mainly dependent on their fibre content, although dosage of enzyme was also important as impacts generally increased at higher dosages of ENZ