Sodium discharge from dairies in California has been identified as an important contributor to soil and water pollution. The Waste Discharge Requirements General Order For Existing Milk Cow Dairies (2007) aims to minimize the amount of fixed solids, including Na, that are discharged from dairies, aiming to maximise the useable lifespan of water resources. As sodium bicarbonate (SB) contains 270 g/kg Na, SB supplementation can substantially increase Na discharge from dairies. The aim of this study was to determine the effects of SB and a potentially alternative buffer that does not contribute to Na discharge and related negative impacts on soil and water quality, (i.e., calcium magnesium carbonate (CMC)), on the performance of high producing California dairy cows. This could help establish if CMC could substitute for SB while maintaining potential benefits of SB. It is well known that SB is a rumen buffer, but research indicates that its benefits are limited mainly to corn silage-based diets. Californian dairies use a wide range of forages, and tend not to base their diets solely or mainly on corn silage. Therefore, typical Californian lactation diets do not always conform to those reported in research publications involving SB. In addition, research parameters such as milk yield, DM intake and dietary ADF often differ substantially between reported studies and conditions present on commercial California dairies, and results are therefore not always practically applicable. Apart from its rumen buffering capacity, SB also has an influence on dietary cation anion difference (DCAD), and can therefore elicit a response via a change in blood acid base balance of cows. The experiment was a Latin square design with 3 treatments (i.e., control (C), SB and CMC), 3 pens of ~310 early lactation cows each, and 3 periods of 28 d. Sodium bicarbonate supplemented cows had elevated milk fat proportion, but a reduced milk yield, resulting in similar milk fat yield between SB supplemented and C cows. Based on a tendency for elevated faecal and in vitro rumen fluid pH, SB had a buffering effect on the gastrointestinal tract GIT, most likely in the rumen. However, it is likely that the difference in DCAD between the C and SB diets played a role in affecting milk yield and milk fat proportion, and a high intake of Na may have been the cause for a reduction in milk yield resulting in passive increase in milk fat proportion. There were no differences between C and CMC treatments, except for an elevated faecal pH of CMC cows. As CMC is not generally soluble at normal rumen pH, buffering likely occurred in the abomasum and small and large intestines. However, a lack of difference in productivity indicates that the buffering effect on the hindgut was not physiologically required. While there were no productive benefits of SB use, it likely substantially increased Na discharge, resulting in an increase in soil and water sodicity and the associated deterioration in soil and water quality. While CMC did not improve productivity or efficiency of cows, it also did not increase Na discharge from the dairy and therefore did not contribute to soil or water sodicity. It can be concluded that SB or CMC supplementation is not advisable for diets and conditions comparable to those present in this study, i.e., high producing dairy cows fed a diet with ‘normal’ aNDF levels and relatively low proportions of corn silage and starch (334.0, 104.0 and 160.3 g/kg DM, respectively, in our study). Copyright / Dissertation (MSc(Agric))--University of Pretoria, 2012. / Animal and Wildlife Sciences / unrestricted

Thirty high-producing multiparous Holstein cows were used in a completely randomized block design to compare a lysine deficient total mixed ration, which was sufficient in methionine, to the same diet supplemented with a rumen protected lysine product. The CPM-Dairy prediction model was used to estimate the nutrient requirements and adequacy or deficiency of amino acids. During the 21-day prepartum transition period, cows were fed 4 kg (dry basis) of the lysine deficient diet plus Eragrostis curvula hay ad lib. After calving, cows were fed the lysine deficient diet for the first three weeks and were then blocked according to the average production from day 19-21. Fifteen cows were allocated to each treatment and blocked into 15 groups of two each. Data on production parameters were analyzed for all cows and also separately for cows in the 10 highest production blocks. The experimental period was from day 22 to 120 postpartum. Lysine supplementation resulted in an optimal dietary lysine : methionine ratio in metabolisable protein of 7.2 : 2.4. Lysine supplementation did not affect dry matter intake, milk production, milk fat percentage, milk protein percentage, milk urea nitrogen, body weight or body condition score; but decreased the non-casein nitrogen and whey content of milk. Furthermore, milk casein, which is the milk nitrogen fraction most sensitive towards increased duodenal supply of lysine and methionine, was not affected. The rumen protected lysine product evaluated did not improve cow productivity, probably because the product was either unprotected from rumen degradation, or overprotected to the extent that the lysine was not available for absorption in the small intestine; or absorbed but could not be metabolised. Copyright / Dissertation (MSc(Agric))--University of Pretoria, 2009. / Animal and Wildlife Sciences / unrestricted

Virginiamycin (V) and Ionophores, such as Poulcox (active ingredient monensin sodium), are antimicrobial feed additives approved for use in cattle to improve performance. The effect of virginiamycin on Gram positive bacteria is similar to that of monensin (M) although the modes of actions differ. Very little information is available on the potential synergistic effects of V and M, especially in dairy cattle diets. The objectives of this study were to investigate the effect of combinations of V and M on the performance of dairy cows. Forty high producing Holstein cows were blocked according to previous milk production and randomly allocated to one of the following lucerne based total mixed diets: 1) Control, no medication (C); 2) Control plus 20 ppm virginiamycin (V); 3) Control plus 15 ppm monensin (M); 4) Control plus 20 ppm virginiamycin and 15 ppm monensin (V+M). The experimental period was from 21 days prepartum until 60 days postpartum. Data were analysed according to a randomized block design, using the model GLM procedure (SAS, 2001). Dry matter intake varied from 23.6 kg/d to 25.4 kg/d and did not differ between treatments (P>0.10). Milk production was higher (P<0.10) for cows receiving V+M (41.2 kg/d) when compared to cows receiving only V (36.6 kg/d), but did not differ from other treatments (P>0.10). Milk fat % was lower for cows receiving M (3.42 %) and the control (3.62 %) when compared to treatment V+M (3.86 %) (P<0.10). Milk protein and MUN did not differ. Body weight loss for the period from calving until day 60 postpartum, tended (P<0.15) to be less for cows receiving V+M (-8.1 kg) when compared to the control (-34.2 kg) and M (-31.9 kg) treatments. Both treatments M and V respectively, decreased blood BHBA and treatment M increased blood glucose (P<0.10) when compared to the control diet. Results suggest a complementary effect between the two additives monensin and virginiamycin when supplemented to early lactation cows. / Dissertation (MSc(Agric))--University of Pretoria, 2008. / Animal and Wildlife Sciences / unrestricted

The objective of this study was to investigate fatty acid concentrations of homogenized and non-homogenized milk from Jersey and Holstein cows. Twenty-two, lactating Holstein (n=11) and Jersey (n=11) cows were fed the same ration with Calan® gates twice daily. Jerseys were fed 25kg DM and Holsteins were fed 30 kg DM. Feed offered was adjusted daily according to previous day orts amount. Body weight and measurements, blood, and ruminal samples were collected weekly as were feed and orts samples. Ruminal fluid was collected from six Holstein and six Jersey cows weekly (n=42). Milk weights were collected daily and samples were taken at 0300 and 1500 hours and pooled by week. There was no difference in fatty acid concentrations from milk of Holsteins compared to Jersey. There was a tendency (P < 0.08) for greater concentration of linolenate between breeds and of stearate between processes.

Thirty-six multiparous Holstein cows were assigned to one of three dietary levels of lasalocid· 0, 180, or 360 mg/hd/d in a completely randomized design Cows were assigned to treatments I wk postcalving and remained on treatment until II wk postcalving Basal diets were composed of ground corn, alfalfa hay, alfalfa haylage, corn silage, and soybean meal, fortified with vitamins and minerals as needed. All ingredients were ground and fed as a total mixed ration Daily rations were fed in two equal portions at 0500 and I 700 h at a rate to allow a 5- 10% refusal. Daily measurements included milk production and dry matter intake (OM 1). Milk composition (fat, protein, and somatic ii cells) was analyzed twice per week on Tuesdays and Fridays. Cow body weight (BW) and visual body condition were measured weekly. Production during previous lactation was used as a covariate in analyzing the data. Although milk production was not affected by dietary treatment, lasalocid tended to increase daily milk production by approximately 2.5 kg/d (P 13) at both the 180 and 360 mg/hd/d levels Percent milk fat and protein were not afl'ected by dietary lasalocid (P 84 and 78, respectively). Somatic cell count of the milk was not affected by dietary lasalocid (/' 17). Dietary lasalocid reduced DMI by approximately I 5 kg/d at both the 180 and 360 mg/hdld levels (P .02). At the 180 and 360 mg/hdld levels, lasalocid increased amount of milk produced per kg of DM consumed by 16 kg (I' 08). either BW (P 89) nor body condition (P = 90) were affected by dietary lasalocid at either level. No effect of treatments was observed on blood metabolites Glucose, nonesterified fatty acids, P-hydroxybutyrate, and cholesterol all tell within the normal ranges of blood serum.

Lactation curves of dairy cows have been studied by dairy scientists for many years. The effects of various hereditary end non-hereditary influences on the lactation curve have been observed. Factors have been developed to standardize production to a common basis, correcting for differences in age, length of lactation, milking per day, gestation and environment.

The relationship of quantity and quality of feed to milk production has been studied for many years. Feeding standards have been developed to systematize feeding of dairy cows according to their requirements. Recently, interest in efficiency of cows in converting feed nutrients into milk has increased.

The thesis deals with analysis the influence to effectiveness of Holstein cows bred on the School farm in Haklovy Dvory. I studied the most frequent reasons of culling cows on the farm and the influence on the cost accounts.

Experiment 1 A survey on the β-Carotene status of Holstein cows in different feeding systems In order to make meaningful recommendations with regard to β-Carotene supplementation is it necessary to know whether cows are deficient in β-Carotene. The objective of this study was to generate data on the β-Carotene status of Holstein cows under three different feeding systems in South Africa, namely; pasture-based, silage-based and hay-based feeding systems. A survey was conducted amongst 30 farms with 10 farms utilizing each of the three systems. Twenty multiparous cows were randomly selected from each farm. Blood samples were taken from the tail vein and analysed for plasma β-Carotene using the iCheck™, a hand held spectrophotometer (BioAnalyt, GmbH, Germany). Cows were then classified as deficient (< 1.5 mg/L), marginal (1.5 to 3.5 mg/L) or optimal (>3.5 mg/L). The average plasma β-Carotene levels differed between feeding systems and concentrations were 5.53, 2.98 and 1.71 mg/L for the pasture based, hay-based and silage-based feeding systems respectively. There was a wide variation in average plasma β-Carotene concentrations in cows on farms within the different feeding systems. Average values per farm ranged between 3.84 and 10.81 mg/L for the pasture based farms, 0.91 and 5.00 mg/L for the hay-based farms and between 0.78 and 3.38 mg/L for the silage-based farms. Results suggest cows on a pasture based feeding system have optimal β-Carotene status and do not need supplementation. Cows on hay-based systems are marginal and on farm testing is recommended. Cows on silage-based systems are generally deficient and β-Carotene supplementation is recommended. Experiment 2 Effect of prepartum β-Carotene supplementation on the postpartum β-Carotene status of Holstein cows. It has been recommended that cows be supplemented β-Carotene when blood plasma levels are deficient (< 1.5 mg/L) or marginal (< 3.5 mg/L) especially during the transition period which is characterised by low intakes and significant losses of β-Carotene through colostrum. The objective of this trial was to determine to what extent prepartum β-Carotene supplementation could maintain postpartum plasma β-Carotene concentrations above 3.5 mg/L in cows fed a lucerne hay-based TMR. Twenty multiparous Holstein cows were blocked into two groups of ten cows each and were fed either 8kg/d of a control TMR (DM) or the control diet supplemented with 1200mg of ROVIMIX® β-Carotene 10%. The experimental period was from 60d pre-partum until 56d postpartum; however the period of the β-Carotene supplementation for the one group was only from 60d prepartum until calving. Blood samples were collected from the tail vein once per week and analysed for plasma β-Carotene using the iCheck™, a handheld spectrophotometer (BioAnalyt, GmbH, Germany). Average plasma β-Carotene concentrations prepartum were higher (6.15 mg/L) (P < 0.05) for supplemented cows compared to the control cows (3.10 mg/L). For the first 5 weeks postpartum, plasma β-Carotene was higher (P < 0.05) for supplemented cows compared to control cows (3.00 mg/L vs. 1.39 mg/L), from weeks 6 to 9 there were no differences (P > 0.05). Overall the average postpartum plasma β-Carotene values were 1.50 mg/L for the control cows and 2.43 mg/L for the supplemented cows and did not differ. Supplemented cows maintained sufficient β-Carotene concentrations only for the first 2 weeks postpartum and were either marginal or deficient for the rest of the experimental period. Results suggest a minor carryover effect of β-Carotene after prepartum supplementation. / Dissertation (MSc Agric)--University of Pretoria, 2013. / gm2014 / Animal and Wildlife Sciences / unrestricted

Vacas leiteira de alta produção têm apresentado declínio da eficiência reprodutiva. Essa redução é devido a causas multifatoriais, entre elas a baixa concentração de estradiol (E2) no proestro e a baixa concentração de progesterona (P4) no ciclo estral subsequentente. O objetivo deste trabalho foi comparar o uso de gonadotrofina exógena na dinâmica folicular e na taxa de prenhez de vacas submetidas ao protocolo Ovsynch (Experimento 1) ou a protocolos utilizando P4 e E2 (Experimento 2). No Experimento 1, animais de primeiro serviço foram pré-sincronizados com dois protocolos (Presynch ou Double-Ovsynch). Já os animais de segundo ou mais serviços foram resincronizados com o protocolo Resynch. Os animais receberam GnRH (1&ordm; GnRH), seguido 7 dias depois pela adiministração de prostaglandina F2&alpha; (PGF2&alpha;). Nesse momento os animais foram divididos homogeneamente por paridade e número de inseminação em um de dois tratamentos: sem FSH (Ovsynch, n = 561) ou com FSH (Ovsynch + FSH, n = 571). O segundo GnRH (2&ordm; GnRH) foi administrado 56 horas após a PGF2&alpha; e a inseminação em tempo fixo foi realizada 16 horas após. Amostras de sangue foram colhidas no 1&ordm; e no 2&ordm; GnRH, na PGF2&alpha; e 6 e 13 dias após o 2&ordm; GnRH para dosagem de P4. Ainda, no 2&ordm; GnRH dosou-se também E2 No Experimento 2, os animais foram sincronizados no dia 0 com um dispositivo de P4 associado a 2 mg de benzoato de estradiol. Oito dias após o dispositivo foi removido e os animais receberam uma dose de PGF2&alpha;. Neste mesmo momento, as vacas foram divididas homogeneamente por paridade, número de serviços prévios, escore de condição corporal e presença de CL no inicio do protocolo em três tratamentos: Controle (sem tratamento adicional; n = 232); eCG (400 UI de eCG; n = 232) e FSH (20 mg de FSH; n = 230). Todos os animais receberam GnRH e foram insemados 56h após a retirada do dispositivo. Foram colhidas amostras de sangue a cada 48h do dia 11 ao dia 22. No Experimento 1, não houve efeito do FSH na concetração sérica de E2 no 2&ordm; GnRH (P = 0,88), no tamanho do maior folículo no 2 &ordm; GnRH (P = 0,63), na taxa de ovulação ao 2&ordm; GnRH (P = 0,69) ou na concentração sérica de P4 no 6&ordm; (P = 0,15) e 13&ordm; (P = 0,36) dia após o 2&ordm; GnRH. A taxa de prenhez foi semelhante (P&gt; 0,05) entre os animais tratados com Ovsynch (36,2%) e Ovsynch + FSH (39,1%). No Experimento 2, os tratamentos não alteraram o diâmetro do folículo ovulatório (P = 0,15), o intervalo entre a remoção do dispositivo de P4 e a ovulação (P = 0,30) e a taxa de ovulação (P = 0,44). Não houve efeito de tratamento na concentração sérica de P4 (P = 0,15). A taxa de prenhez foi diferente entre os tratamentos aos 30 dias após a IATF (Controle = 28,0a vs FSH = 18,7b vs eCG = 29,7a %; P = 0,01), mas não aos 60 dias (Controle = 21,6 vs FSH = 16,1 vs eCG = 24,1%; P = 0,08) e na perda de gestacional (Controle = 18,8 vs FSH = 14,0 vs eCG = 18,4%; P = 0,39). Assim, o tratamento com FSH não estimulou o crescimento folicular final e a função luteínica de vacas leiteiras de alta produção sincronizadas com os protocolos Ovsynch e P4/E2. / Fertility in high-producing dairy cows has decreased over the years, which has been associated with reduced estradiol (E2) concentrations during proestrus and suboptimal progesterone (P4) concentrations during early stages of gestation. The objectives of the present study were to evaluate the effects of exogenous gonadotropins on follicular dynamics and risk of pregnancy per artificial insemination (P/AI) in cows subjected to the Ovsynch protocol (Experiment 1) or to a P4/E2-based timed AI protocol (experiment 2). In experiment 1, cows were enrolled in the Ovsynch protocol (GnRH, 7 d PGF2&alpha;, 56 h GnRH, 16 h IA) either after presynchronization (Presynch or Double-Ovsynch; first AI postpartum) or 32 d after previous AI. At the PGF2&alpha; injection, cows were blocked by parity and number of AI and, within each block, randomly allocated to eitherreceive 20 mg of FSH at the moment of the PGF2&alpha;(Ovsynch + FSH, n = 571) or to remain as untreated control (Ovsynch, n = 561). Blood was sampled at the 1st and 2nd GnRH and PGF2&alpha; injections, as well as on d 6 and 13 after the 2nd GnRH to access P4 and E2 (at the 2nd GnRH only) concentrations. In experiment 2, cows were received a P4 device and 2 mg of estradiol benzoate. The device was removed 8 d later concurrently with an injection of PGF2&alpha;, followed by an injection of GnRH and AI at 56 h.At the PGF2&alpha; injection, cows were blocked by parity, number of AI, body condition score, and presence of a CL at device insertion.Within each block, cows were randomly allocated to receive either 20 mg of FSH (FSH, n = 230), 400 IU of eCG (eCG, n = 232), or no additional treatment at the moment of the PGF2&alpha; (Control, n = 232). Blood was sampled at every 48 h from 1 to 12 d after AI. In experiment 1, there was no effect of FSH on serum E2 at the 2nd GnRH (P = 0.88), follicle diameter at the 2nd GnRH (P = 0.63), ovulatory response to the 2nd GnRH (P = 0.69), or serum P4 on d 6 (P = 0.15) and 13 (P = 0.36) after the 2nd GnRH. Also, P/AI was similar (P &gt; 0.05) between Ovsynch (36.2%) and Ovsynch + FSH (39.1%). In experiment 2, treatment did not affect ovulatory diameter (P = 0.15), interval from P4 device removal and ovulation (P = 0.30), ovulatory response to the 2nd GnRH (P = 0.44), and serum P4 (P = 0.15). Interestingly, treatment with FSH reduced (P = 0.01) P/AI on d 30 (Control = 28.0a vs. FSH = 18.7b vs. eCG = 29.7a %), but not on d 60after timed AI (Control = 21.6 vs. FSH = 16.1 vs. eCG = 24.1%; P = 0.08).The risk of pregnancy loss was not affected by treatment (Control = 18.8 vs. FSH = 14.0 vs. eCG = 18.4%; P = 0.39). In conclusion, treatment with FSH failed to enhance the final growth of the ovulatory follicle and did not improve luteal function after AI in high-producing dairy cows synchronized with either the Ovsynch or P4/E2-based timed AI protocols.