The widespread increase in use of maize-based feedstuffs in California dairy cow rations has raised concerns of reduced efficiency of CP utilization due to the low lysine content of maize and maize by-products. The objectives of this research were to determine the impact of increased dietary maize CP levels on animal performance using three metabolic models of dairy cows in order to predict limiting AA’s in California dairy rations to identify a ruminally protected AA package to supplement similar rations. Since lysine was the most consistently predicted limiting AA among dairies, and metabolic models, the dairy with the ration calculated to be the most limiting in lysine was chosen to determine effects of feeding an RPL product on milk production and composition, as well as on N balance. Nutrient profiles of 16 high multiparity cow rations were evaluated and limiting AA predicted by the metabolic models Amino Cow, CPM Dairy and Shield. Higher inclusion levels of maize products in rations increased the contribution of maize CP to the total CP content of the TMR, to between 20 – 40%, but had no impact on cow performance. Even though the lysine to methionine ratio decreased as more maize CP was included in the TMR, it did not have a major impact on the final predicted AA profile of MP, or milk component levels, but, according to Shield, it had an effect on milk yield. Methionine, isoleucine and lysine were predicted to be most limiting according to Amino Cow, CPM Dairy and Shield respectively. The models suggested three dramatically different AA packages but the high degree of consistency within model in predicting the limiting AA sequence among dairies, suggest that there may be sufficient consistency in the nutrient profiles among rations to support production of a ruminally protected AA complex. The second experiment used a double (i.e., early and mid-lactation multiparity dairy cows) 2 x 2 factorial with 28 day experimental periods. Feeding the RPL, with estimated rumen escape of lysine between 18 and 23% suggesting an increased intestinal absorption of lysine between 8 and 22 g/d/cow, did not influence DMI or milk, true protein and lactose yields. Milk fat yield and concentration decreased, while MUN percentages increased when RPL was fed. Blood plasma levels of almost all AA’s, except lysine, decreased when RPL was fed, suggesting that lysine was the limiting AA and that its supplementation led to increased absorption and utilization of other AA. The lack of response in milk protein synthesis and the decrease in plasma 3-MH concentrations when RPL was fed suggests that muscle protein synthesis was stimulated, and degradation reduced, with RPL feeding. It is possible that lysine had an effect, either directly or indirectly, on muscle protein turnover and energy metabolism that, impacted intakes, metabolism and absorption of AA and milk production in mid lactation cows, but it had no major impact on early lactation cows. Copyright / Dissertation (MSc(Agric))--University of Pretoria, 2009. / Animal and Wildlife Sciences / unrestricted

The GnRH vaccine may offer an alternative to the current immunocontraceptive method in elephant cows which uses native porcine zona pellucida proteins derived from abattoir slaughtered pigs as the immunogen, greatly limiting its availability. The pZP vaccine is stored at -20 °C and must be mixed with an adjuvant before use. The GnRH vaccine Improvac® is commercially available, already contains the adjuvant and can be stored at 4 °C. The aim of this study was to evaluate the efficacy of the gonadotrophin releasing hormone (GnRH) vaccine Improvac® (Pfizer Animal Health, Sandton, South Africa) in the induction of anoestrus in elephant cows. The Improvac® was administered to eight adult, female, healthy, free-ranging elephants, located in Entabeni Private Game Reserve in the Limpopo Province, South Africa. Another four cows were left untreated and served as controls. The monitoring of the experimental population was conducted over a twelve-month observation period via non-invasive faecal steroid analysis. Progesterone metabolites in extracted samples were measured by Enzyme Immunoassay (EIA) to determine luteal activity and thus the effect of the GnRH vaccine on the endocrine correlates. This study started with a three-month control period prior to vaccination when faeces were collected from each study animal, as soon as possible after defecation to ensure positive identification of the individual with its sample. The three-month period was followed by the immunization protocol. The elephants all received a primary, followed by a booster vaccination dose five weeks later. Each dose of 3 ml contained 600 ìg of RnRF-protein conjugate; both treatments were applied via remote delivery. Monitoring continued until the end of the twelve-month observation period. Observations of oestrous behaviour during the twelve-month period were also recorded. The results showed no statistical difference between treated and control females. There was, however, marked individual variation in response to GnRH immunization. This was possibly influenced by physiological and environmental factors such as age, where the youngest cows showed a better response in terms of reduced progestagen secretion; as well as season, where progestagen levels increased 1.3 times during the rainy season compared to the dry season. There was no association between average progestagen concentration and social hierarchy ranking. A high percentage (86.48%) of behaviours that could be related to oestrus coincided with the onset of the luteal phase and a subsequent rise in progestagen concentrations. All the females (treated and control) showed some evidence of ovarian cyclicity during the study, although 75% of the cycles did not fall within the normal 13-17 week oestrous cycle range reported, suggesting that abnormal cycles are a common reproduction irregularity inherent to non-pregnant wild African elephants. Further research to determine the optimal vaccination protocol is indicated in order to obtain consistent responses to the vaccine that will provide an efficient and safe contraceptive for use in female African elephants. Copyright / Dissertation (MSc)--University of Pretoria, 2011. / Production Animal Studies / unrestricted

Hierdie studie het ten doel gehad om die effekte van Se en β-karoteentoediening op vit A, vit E, konsepsietempo en progesteroonvlakke tydens embrio-oorplasings in ontvangerkoeie te ondersoek. Die effekte van die verskillende faktore op mekaar sou ook bepaal word. In Totaal van 142 multipare koeie wat in vier groepe verdeel is, was as ontvangers vir die studie gebruik. Die groepe was as volg behandel: Groep 1 (35 koeie), 50 mg Se en 1500 mg vit E intramuskulêr 6 en 3 weke voor die oorplasings; Groep 2 (36 koeie), 300 mg l1-karoteen per os per bees per dag vanaf 6 weke voor die oorlasings; Groep 3 (36 koeie), vit E/Se en β-karoteen soos in Groepe 1 en 2 respektiewelik; Groep 4 (35 koeie) negatiewe kontrole groep met geen behandeling nie. Elke ontvanger het 6 weke voor oorplasing vit ADE oraal ontvang. Embrios is na 20, 19, 19 en 18 ontvangers van Groepe 1, 2, 3 en 4 onderskeidelik oorgeplaas. Bloedmonsters is van elke dier vir ontledings in die middel van die oorplantingsperiode getrek. Die toediening van Se was hoogs betekenisvol met RBS GSH-Px aktiwiteit gekorreleer R2 = 0,32960, (n = 136, P = 0,0000). Die toediening van β-karoteen was ook hoogs betekenisvol gekorreleer met die RBS GSH-Px aktiwiteit, R2 = 0,18950, (n=136, P< 0,0000). Die RBS GSH-Px aktiwiteit was 7,49,6,61,10,75 en 4,5 EE 11x1010 RBS vir Groepe 1, 2, 3 en 4 onderskeidelik. Groepe 1 en 3,1 en 4, 2 en 3, 2 en 4, en 3 en 4 het betekenisvol van mekaar verskil maar nie Groepe 1 en 2 nie. Daar was geen verband tussen β-karoteen plasmavlakke en RBS GSH¬Px aktiwiteit nie. Die orale toediening van β-karoteen het plasmavlakke duidelik laat styg en was betekenisvol met die β-karoteen plasmavlakke gekorreleer R2 = 0,09296, (n = 134, P=O,0003). Die groepe wat β-karoteen ontvang het, Groepe 2 en 3, se plasmavlakke was merkbaar hoër as die van Groepe 1 en 4 wat niks ontvang het nie. Die groep se waardes was 8,72, 10,13, 9,53 en 8,50 µmol/l vir Groepe 1, 2, 3 en 4 respektiewelik. Groepe 1 en 2, 2 en 4, en 3 en 4 het betekenisvol van mekaar verskil (P=0,0021) maar nie Groepe 1 en 3, en 1 en 4 nie. Daar was 'n positiewe korrelasie tussen die toediening van vit E/Se en die a¬tocoferol plasmavlakke, R2 = 0,06344, (n = 134, P=0,0033). Daar was egter geen aanduiding van 'n verband tussen RBS GSH-Px aktiwiteit en α-tocoferol plasmavlakke nie. Daar was wel In betekenisvolle korrelasie tussen α-tocoferol en β-karoteen plasmavlakke (P=0,0001). Die groepswaardes was 11,90, 10,59, 11,67 en 10,56 vir Groepe 1, 2, 3 en 4 onderskeidelik. Groepe 1 en 2, en 1 en 4 het betekenisvol van mekaar verskil (P=0,0334) maar nie die ander groepe, Groepe 1 en 3, 2 en 3, 2 en 4, en 3 en 4 nie. Die korrelasie tussen die toediening van Se en die retinol plasmavlakke was nie statisties betekenisvol nie (P=0,0671) maar tussen RBS GSH-Px aktiwiteit en retinol plasmavlakke was dit wel betekenisvol R2 = 0,03086, (n = 133, P=0,0431). Daar was ook In waarskynlike korrelasie tussen die toediening van β-karoteen en die retinol plasmavlak (P=0,0835) maar geen korrelasie tussen β-karoteen plasmavlakke en retinol plasmavlakke nie. Die groepwaardes was 1,068, 1,065, 1,154 en 1,026 µmol/l vir Groepe 1, 2, 3 en 4 onderskeidelik. Die dragtigheidstempo na die oorplasing van embrios was 50,0%, 47,4%, 31,5% en 27,8% vir Groepe 1, 2, 3 en 4 onderskeidelik. Die verskille was nie betekenisvol nie. Daar was 'n negatiewe korrelasie tussen die β-karoteen plasmavlakke en progesteroon plasmavlakke vir die eerste 5-9 dae van die estrussiklus. Retinol plasmavlakke en progesteroon plasmavlakke was wel positief gekorreleer (P=O,0317). Die groepswaardes was 5,67, 2,90, 4,28 en 5,60 µmol/l vir Groepe 1, 2, 3 en 4 onderskeidelik. RBS GSH-Px was betekenisvol gekorreleer met corpus luteum grootte maar corpus luteum grootte was nie met progesteroon waardes gekorreleer nie. Daar was geen statistiese verskille tussen die groepe ten opsigte van estruslengte en die tydsduur tussen prostaglandientoediening en estrus nie. Op individuele basis was daar wel In betekenisvolle korrelasie van β-karoteen plasmavlak met beide estruslengte (P=O,0298) en die tydsduur tussen prostaglandientoediening en estrus (P=0,0130). Estruslengte en die tydsduur tussen prostaglandien en estrus was ook betekenisvol met mekaar gekorreleer (P < 0,0000). / This study addressed some of the effects that selenium and β-carotene administration have on vit A, vit E, conception rates, progesterone levels, oestrus length, interval from PG to oestrus and corpus luteum size in embryo recipients. A total of 142 multiparous cows asigned to 4 test groups, were used as recipients in this study. Group 1 (35 cows) received 50 mg Se and 1500 mg vit E intramuscularly 6 and 3 weeks before transfer, Group 2 (36 cows) received 300 mg β-carotene orally per cow per day starting 6 weeks prior to transfer, Group 3 (36 cows) received both vit ElSe and β-carotene as per Group 1 and 2 and Group 4 (35 cows) was a negative control, with no treatment. All recipients received vit ADE orally 6 weeks before transfers. Embryos were transferred to 20, 19, 19, and 18 recipients of the Groups 1, 2, 3 and 4 respectively. Blood for analysis was drawn from all the recipients in the middle of the transferal week, being day 3 of the 5-day period. The administration of selenium was highly significantly correlated with the corresponding RBS GSH-Px activity R2 = 0,3290, (n = 135, P < 0,0000). The β-¬carotene administration was also highly significantly correlated with the RBS GSH¬Px activities R2 = 0,18950, (n = 136, P < 0,0000). However, there were no correlation between the β-carotene plasma levels and that of the RBS GSH-Px activities. The RBS GSH-Px were 7,49, 6,61, 10,75 and 4,5 Enzyme Units 11x1010 RBS for Groups 1, 2, 3 and 4 respectively. Groups 1 and 3, 1 and 4, 2 and 3, 2 and 4, and 3 and 4 differ significantly from each other but not Groups 1 and 2. There were no connection between B-carotene plasma levels and RBS GSH-Px activities. The treatment of β-carotene itself was succesful and was significantly correlated with the resulting β-carotene plasma levels R2 = 0,09296, (n = 134, P = 0,0033). The β-carotene plasma levels of the groups that received β-carotene, Groups 2 and 3, were noticeably higher than those of Group 1 and 4, which did not receive β-carotene. The values were 8,72, 10,13, 9,53 and 8,5 µmol/l for Groups 1, 2, 3 and 4 respectively. Groups 1 and 2, 2 and 4, and 3 and 4 differed significantly from one another (P = 0,0021) but not those of Groups 1 and 3, and 1 and 4. There was a positive correlation between the administration of Se and the retinol plasma levels (P = 0,0671) and a positive significant correlation between the RBS GSH-Px and the retinol plasma levels R2 = 0,03086, (n = 133, P = 0,0431). There was also a positive correlation between the administration of β-carotene and the retinol plasma levels (P = 0,0835) but no correlation between β-carotene plasma levels and retinol plasma levels. The values were 1,068, 1,065, 1,154 and 1,026 µmol/ for Groups 1, 2, 3 and 4 respectively. The pregnancy rate after embryo transferal were 50%, 47,4%, 31,5% and 27,8% for Groups 1, 2, 3 and 4 respectively. The differences were not significant. There was a negative correlation between β-carotene plasma levels and progesterone plasma levels for the first 5 to 9 days of the oestrus cycle. Retinol plasma levels however were significantly correlated with progesterone plasma levels (P = 0,0317). The progesterone levels were 5,67, 2,90, 4,28 and 5,60 µmol/ for Groups 1, 2, 3 and 4 respectively. The RBS GSH-Px activity was significantly correlated with corpus luteum size (P = 0,0445) but corpus size was not correlated with progesterone values. There were no statistical differences amongst the groups, between oestrus length and the interval from prostaglandin to oestrus. However on an individual basis there was a significant correlation between β-carotene plasma levels and both the oestrus length (P = 0,0298) and the interval from prostaglandin to oestrus (P = 0,0130). Oestrus length and the interval from prostaglandin to oestrus were also significantly correlated with each other (P < 0,0000). / Dissertation (MMedVet)--University of Pretoria, 2000. / Production Animal Studies / MMedVet / Unrestricted

Kikuyu is well adapted to the main milk producing areas of the Southern Cape region of South Africa. The strategic incorporation of different types of temperate grasses into kikuyu pastures can increase the seasonal dry matter production, pasture quality, and milk production attainable from these pastures. To determine whether there is production and economical differences between kikuyu based pasture systems, a trial was conducted on the Outeniqua Research Farm near George. The three pasture treatments, namely italian, westerwold, and perennial ryegrass over-sown into kikuyu, were tested. Forty-five Jersey cows were blocked and cows within blocks were randomly allocated to the treatments. The cows received 9 kilograms of pasture (on a dry matter basis) per cow per day, and four kilograms of concentrate per cow per day. Milk production was recorded daily, and milk composition was determined monthly. The cows were weighed and body condition scored monthly. The perennial ryegrass pasture treatment had a higher milk production per hectare (32288 kg/ha) than the westerwold ryegrass pasture treatment (29761 kg/ha) but did not differ from the italian ryegrass pasture treatment (30446 kg/ha). The italian ryegrass pasture treatment had a higher milk protein percentage than the perennial ryegrass pasture treatment (3.84% vs. 3.64%) but did not differ from the westerwold ryegrass pasture treatment (3.75%). When the three pasture treatments were economically compared, the italian ryegrass pasture treatment had the highest margin over specified costs per hectare (R 36,565.03), followed by the perennial (R 33,889.14) and westerwold (R 29,468.09) ryegrass pasture treatments. From the results it seems that the italian ryegrass pasture treatment is the best choice for a kikuyu based pasture system in the Southern Cape region of South Africa. A high level of concentrate supplementation could increase energy intake of grazing dairy cows, but might also reduce fibre digestion within the rumens of high producing dairy cows. To test this hypothesis, two trials were conducted, one during October and November 2007, and the other during March 2008. In both trials twelve rumen cannulated cows were allocated to four groups. Two groups were allocated to each pasture treatment, namely perennial and westerwold ryegrass over-sown into kikuyu. Within each pasture treatment, one group received 4 kg of concentrate per cow per day, and the other 8 kg of concentrate per day. Pasture was allocated at 9 kg per day (DM). Cows were adapted for ten days, after which ruminal pH, and ammonia nitrogen and volatile fatty acid concentration data was collected. An in sacco study was conducted to determine the neutral detergent fibre degradability. After the data was collected, the two groups within each pasture treatment swapped concentrate levels; were adapted, and the same data as described above was collected. During both trials reductions in ruminal pH were observed when a higher amount of concentrate was supplemented. During the first trial there was a significant increase in the time that the ruminal pH remained below pH 5.8 on the westerwold ryegrass pasture treatment (from 80 minutes when the cows received 4 kg of concentrate per day, to 375 minutes when it was increased to 8 kg of concentrate per day). A decrease in neutral detergent fibre degradability was also seen. During the second trial, the percentage of NDF disappearance decreased from 8.45% over a twelve hour period when 4 kg of concentrate was fed, to 4.51% when 8 kg of concentrate was fed on the perennial ryegrass pasture treatment. From the results it appears that feeding a higher level of concentrate supplementation to high producing dairy cows grazing kikuyu pasture systems has a negative effect on neutral detergent fibre digestion within the rumen. It appears that feeding a moderate level of concentrate supplementation when cows are on pasture based systems is more beneficial to the rumen environment and decreases the possibility of sub-clinical ruminal acidosis when cows grazed ryegrass dominant pastures, but had a less pronounced effect when the dominant pasture specie was kikuyu. Future research could examine the relationship between the level of concentrate supplementation and pasture specie more closely, as it would be interesting to find the optimal ratios for each pasture specie. Copyright / Dissertation (MScAgric)--University of Pretoria, 2009. / Animal and Wildlife Sciences / unrestricted

Rumen protected methionine has been used in an effort to improve the amino acid composition of metabolisable protein since the early 1960’s. The positive response in dairy cows in terms of milk protein composition and milk production, especially during early lactation has been well documented. Rumen protected methionine supplementation contributes to improving the protein efficiency of the dairy cow which improves the overall productivity of the dairy enterprise. Recently a locally developed liquid rumen protected methionine prototype became available. In our study this product was evaluated through a series of experiments in conjunction with two standard, well known methionnine sources, Smartamine ™ M and unprotected DL-methionine that provided a reference to the relative bioavailability of the liquid rumen protected methionine. In the first of the two studies the effect of methionine supplementation on milk yield, milk composition as well as milk protein composition was evaluated through the milk composition technique. The ability of the liquid rumen protected methionine to elevate blood plasma methionine levels was also evaluated through the blood plasma technique after oral dosing and post ruminal infusion of methionine. The liquid rumen protected methionine prototype induced no response in either milk yield or milk composition. Results suggested that the prototype is either not adequately protected against rumen degradation or it is not available for absorption in the small intestine. The inability of the liquid rumen protected methionine prototype to elevate blood plasma methionine after post ruminal infusion further proved that the product is not available for absorption at this site either. In the event that the product’s mode of action or method of protection caused it not to be detected as pure methionine in the blood, an effect on milk yield would have been expected which was not the case. This product proved to have a very low or no bioavailability in comparison to the well researched and proven Smartamine ™ M. / Dissertation (MSc(Agric))--University of Pretoria, 2012. / Animal and Wildlife Sciences / unrestricted

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

The purpose of this research was to investigate the effects of climatic variations upon the daily activities of grazing cattle. The activities of individual cows on a partially seeded salt desert shrub range were observed and recorded during three grazing periods. Two of the periods were during consecutive winters and the other during the spring. Climatic variations during the second winter period were quantified and compared to changes in the daily activity patterns of the cattle. Distinctly different daily routines of cattle activities were evident for the winter and spring seasons. In the spring, the cattle grazed, traveled, and drank more each day than they did during the winter months. The increase in these activities was attributed to the more temperate climatic conditions and the higher energy demands of lactation. Air temperature, changes in barometric pressure, windspeed, precipitation, snow depth, and radiation all influenced cattle activities in the winter. Decreasing air temperature and rapid fluctuations in barometric pressure both correlated significantly with increased grazing time. Increasing windspeed and greater snow depth caused the cattle to travel less distance daily. The cattle ceased grazing during snowstorms. They oriented themselves at right angles to the sun while standing and lying. The modifications which occurred in daily activity patterns were shown to be apparently directed toward the conservation of energy during periods of climatic stress.

Six nonlactating Holstein cows fitted with rumen and duodenal cannula were used to determine the efficacy of pH sensitive fatty acid polymer encapsulation as a means protecting amino acids from rumen fermentation and as a post-ruminal amino acid delivery system. The cows were arranged in a 2 x 2 factorial in a latin square design. Treatments were 1) the basal ration, and 2) basal ration plus rumen-protected lysine, methionine, and threonine at 10 g each per day. Rumen parameters measured were pH, ammonia, volatile fatty acids, protozoa, liquid, and dry matter rate of passage, total viable bacteria, and viable cellulolytic bacteria. Duodenal parameters measured were crude protein, ammonia, and amino acid concentrations. Total tract apparent digestibility of nutrients was measured. In addition, rumen degradation of the three amino acid products was measured by loss from nylon bags, in the rumen. Loss of product from nylon bags suggested the lysine and threonine products had no significant rumen protection, but that the methionine product had > 50% protection at 12 h in the rumen. None of the rumen parameters measured differed (P>.05) due to treatment. Duodenal crude protein and ammonia concentrations did not differ due to treatment. Duodenal amino acid concentrations were numerically higher for the amino acid supplemented treatment, but the differences were nonsignificant and thought to be confounded by failure of the lysine and threonine products. Total tract apparent nutrient digestibility was not affected by treatment. A second experiment was conducted using 40 post-parturient Holstein cows, and different rumen-protected amino acid products from the first trial. Cows were nesteMwby treatment (control vs rumen-protected methionine 46 g and lysine 22 g) and parity (primiparous vs multiparous). Dry matter intake and milk production were monitored daily, body weight weekly, and milk composition bi-weekly. Total tract apparent nutrient digestibility was measured during the last week of the 10-week trial. There was no significant (P<.05) effect of supplemental rumen-protected lysine and methionine among primiparous animals. Multiparous animals receiving supplemental amino acids had lower dry matter intakes and yield of milk components than control animals.

Artificial insemination of dairy cattle has become a major part of the dairy industry during the past 1.5 years. There has been a steady increase in the number of cows serviced each year since the first artificial breeding association was organized in the United States in 1938. In 1952 there were 4,238,245 cows bred artificially. In 1953 there were 4,845,222 and in 1955, artificially cows bred numbered 5,250,000.

No description available.