During spring kikuyu-ryegrass pasture has a low dry matter (DM) content (10-12%), is highly digestible and has high levels of soluble carbohydrates. Low rumen pH values have been recorded for cows grazing these pastures even when supplemented with low levels of concentrate. The rumen environment and extent of rumination may therefore be sub-optimal. Supplementation of the pasture with dry roughage may improve rumination, the rumen environment and therefore also milk production performance. The aim of the study was to determine if strategic supplementation of lucerne hay will improve milk production, milk composition and the rumen environment of cows grazing high quality kikuyu/ryegrass during spring and receiving low levels of concentrate. Forty eight high producing Jersey cows were blocked and randomly allocated to one of the following treatments: control (no supplemental roughage), supplementation of 1.0 kg lucerne hay and supplementation of 2.0 kg lucerne hay after morning milking. Cows received 5 kg of dairy concentrate per day during milking. Cows grazed as one group and pasture was allocated to ensure a post grazing height of 10-12 on the rising plate meter (5-6 cm). The average post grazing pasture height for the experimental period was 10.83±1.68 (n=73) on the RPM (5.42 cm). There were no differences (P >0.10) between the treatments for 4% fat corrected milk production, which were 22.2 kg/d for the control, and 22.5 kg/d and 22.9 kg/d for the 1 kg and 2 kg lucerne treatments respectively. Milk fat and protein percentage was not affected (P >0.10) by supplementation of lucerne hay. The milk lactose content of cows receiving the control and 1 kg lucerne hay treatments were higher (P <0.05) than those of cows receiving the 2 kg lucerne hay treatment. Eight rumen cannulated Jersey cows were randomly allocated to either the control or the 2 kg lucerne hay treatment in a cross-over design. These cows grazed together with the cows of the production study and received the same dairy concentrate. Rumen pH was measured for 48 hours with 10 minute intervals using an automated pH logging system. Rumen samples were taken at 08:00, 14:00, 20:00 and 02:00 and were analysed for ammonia-nitrogen (NH3-N), volatile fatty acids (VFA) and pH. An in sacco study was conducted to determine DM and neutral detergent fibre (NDF) disappearance of ryegrass. There were no differences (P >0.10) between treatments in overall mean pH, measured with either the logging systems or with the portable pH meters averaging 6.18 and 6.11 for cows receiving the control and the 2 kg lucerne treatment respectively. The mean rumen NH3-N did not differ (P >0.10) between treatments. The mean concentration of acetic acid and the total VFA concentration was higher (P <0.05) for cows receiving the 2 kg lucerne treatment compared to the control. There were no differences (P >0.10) between treatments in the DM or NDF disappearance of ryegrass after 24 hours. Supplementation of lucerne hay to cows grazing well managed kikuyu-ryegrass pasture during spring did not improve milk production, milk composition, rumen pH or in situ NDF disappearance of ryegrass Results suggest that cows grazing kikuyu/ryegrass pastures supplemented with low levels of concentrate consume sufficient eNDF to maintain a favourable rumen environment and normal milk composition. Copyright / Dissertation (MSc(Agric))--University of Pretoria, 2012. / Animal and Wildlife Sciences / 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

O experimento conduzido na Fazenda Rancho Santa Zelina, em Júlio de Castilhos, RS, entre julho de 2014 a setembro de 2015, analisou o desempenho reprodutivo de 42 vacas mestiças Angus primíparas aos 24/25 meses de idade postas no pós-parto em pastagem cultivada de aveia (Avena strigosa Schreb) e azevém (Lolium multiflorum Lam.). Aos 80 dias pós-parto foram distribuídas conforme peso (PC) e escore de condição corporal (ECC) em dois sistemas alimentares: SS – mantidas por 23 dias na pastagem cultivada e sete dias em pastagem natural; CS – mantidas por 23 dias na pastagem cultivada e sete dias em pastagem natural com a suplementação diária de 0,8% do PC de suplemento contendo 14% proteína bruta (PB) e 70% de nutrientes digestíveis totais (NDT). O método de pastoreio foi o contínuo com massa de forragem (MF) média de 1450 kg/ha de matéria seca (MS) em pastagem cultivada e 2150 kg/ha/MS em pastagem natural. O delineamento experimental foi o inteiramente casualizado, com dois sistemas alimentares e vinte e uma vacas por sistema alimentar, sendo cada vaca considerada uma unidade experimental. Para comparar os sistemas alimentares, as variáveis que apresentaram normalidade foram avaliadas utilizando o procedimento MIXED do SAS. A variável taxa de prenhez foi avaliada pelo teste do qui-quadrado. A suplementação não influenciou o peso (PCFT) e condição corporal final (ECCFT) das vacas, porém a variação de peso diária média das vacas do CS foi superior a das em SS durante os sistemas alimentares (0,465 kg e 0,227 kg, respectivamente). Os bezerros do CS nesse período apresentaram maior ganho médio diário, 0,829 kg comparado com aqueles do SS de 0,644 kg e maior peso final (130,86 kg e 117,29 kg, respectivamente). As vacas do CS tiveram a significativa maior taxa de prenhez de 80,95%, enquanto as do SS tiveram 57,14%. Aos 42 dias de acasalamento 80,95% das vacas do CS estavam prenhes, enquanto do SS apenas 28,57% já tinham concebido. Vacas primíparas aos 24 meses de idade e que irão conceber têm maior peso e escore de condição corporal ao início do acasalamento do que as futuras falhadas. / The experiment was conducted at the Farm Rancho Santa Zelina in Julio de Castilhos, RS, from July 2014 to September 2015, examined the reproductive performance of 42 crossbred cows Angus gilts to 24/25 months old put postpartum in cultivated pasture oat (Avena strigosa Schreb) and ryegrass (Lolium multiflorum Lam.). After 80 days postpartum were distributed as weight (BW) and body condition score (BCS) in two food systems:SS – 23 days in a cultivated pasture (Avena strigosa Schreb. e Lolium multiflorum Lam.) and 7 days in a natural grassland; CS – 23 days in the same cultivated pasture and 7 days in a natural grassland receiving 0,8% BW supplement with 14% crude protein (CP) and 70% total digestible nutrients (TDN). The grazing method was continuous with herbage mass (MF) average of 1450 kg/ha of dry matter (DM) in cultivated pasture and 2150 kg/ha/DM in natural pasture. Treatments were arranged in a completely randomized design with two food systems and twenty-one cows for feeding system, where each cow was considered an experimental unit. To compare the food systems, variables with normal distribuition were assessed using the SAS MIXED procedure. The pregnancy rate was evaluated using the chi-square test. Supplementation did not affect cows‟ final body weight (FBW) and final body condition (FBC), but the daily average weight variation of cows in CS was higher than in SS (0.465 kg and 0.227 kg, respectively). The CS calves this period had higher average daily gain, 0.829 kg compared to those of the SS 0.644 kg and higher final weight (130.86 kg and 117.29 kg, respectively). The 80.95% pregnancy rate of the CS cows was higher than the 57.14 % of SS cows. After 42 days of mating, 80.95% of the CS primiparous cows had conceived, against just 28.57% from the SS. Primiparous cows at 24/25 months old and that will get pregnant have higher BW and BCS at beginning of the mating than the open ones.

O experimento conduzido na Fazenda Rancho Santa Zelina, em Júlio de Castilhos, RS, entre julho de 2014 a setembro de 2015, analisou o desempenho reprodutivo de 42 vacas mestiças Angus primíparas aos 24/25 meses de idade postas no pós-parto em pastagem cultivada de aveia (Avena strigosa Schreb) e azevém (Lolium multiflorum Lam.). Aos 80 dias pós-parto foram distribuídas conforme peso (PC) e escore de condição corporal (ECC) em dois sistemas alimentares: SS – mantidas por 23 dias na pastagem cultivada e sete dias em pastagem natural; CS – mantidas por 23 dias na pastagem cultivada e sete dias em pastagem natural com a suplementação diária de 0,8% do PC de suplemento contendo 14% proteína bruta (PB) e 70% de nutrientes digestíveis totais (NDT). O método de pastoreio foi o contínuo com massa de forragem (MF) média de 1450 kg/ha de matéria seca (MS) em pastagem cultivada e 2150 kg/ha/MS em pastagem natural. O delineamento experimental foi o inteiramente casualizado, com dois sistemas alimentares e vinte e uma vacas por sistema alimentar, sendo cada vaca considerada uma unidade experimental. Para comparar os sistemas alimentares, as variáveis que apresentaram normalidade foram avaliadas utilizando o procedimento MIXED do SAS. A variável taxa de prenhez foi avaliada pelo teste do qui-quadrado. A suplementação não influenciou o peso (PCFT) e condição corporal final (ECCFT) das vacas, porém a variação de peso diária média das vacas do CS foi superior a das em SS durante os sistemas alimentares (0,465 kg e 0,227 kg, respectivamente). Os bezerros do CS nesse período apresentaram maior ganho médio diário, 0,829 kg comparado com aqueles do SS de 0,644 kg e maior peso final (130,86 kg e 117,29 kg, respectivamente). As vacas do CS tiveram a significativa maior taxa de prenhez de 80,95%, enquanto as do SS tiveram 57,14%. Aos 42 dias de acasalamento 80,95% das vacas do CS estavam prenhes, enquanto do SS apenas 28,57% já tinham concebido. Vacas primíparas aos 24 meses de idade e que irão conceber têm maior peso e escore de condição corporal ao início do acasalamento do que as futuras falhadas. / The experiment was conducted at the Farm Rancho Santa Zelina in Julio de Castilhos, RS, from July 2014 to September 2015, examined the reproductive performance of 42 crossbred cows Angus gilts to 24/25 months old put postpartum in cultivated pasture oat (Avena strigosa Schreb) and ryegrass (Lolium multiflorum Lam.). After 80 days postpartum were distributed as weight (BW) and body condition score (BCS) in two food systems:SS – 23 days in a cultivated pasture (Avena strigosa Schreb. e Lolium multiflorum Lam.) and 7 days in a natural grassland; CS – 23 days in the same cultivated pasture and 7 days in a natural grassland receiving 0,8% BW supplement with 14% crude protein (CP) and 70% total digestible nutrients (TDN). The grazing method was continuous with herbage mass (MF) average of 1450 kg/ha of dry matter (DM) in cultivated pasture and 2150 kg/ha/DM in natural pasture. Treatments were arranged in a completely randomized design with two food systems and twenty-one cows for feeding system, where each cow was considered an experimental unit. To compare the food systems, variables with normal distribuition were assessed using the SAS MIXED procedure. The pregnancy rate was evaluated using the chi-square test. Supplementation did not affect cows‟ final body weight (FBW) and final body condition (FBC), but the daily average weight variation of cows in CS was higher than in SS (0.465 kg and 0.227 kg, respectively). The CS calves this period had higher average daily gain, 0.829 kg compared to those of the SS 0.644 kg and higher final weight (130.86 kg and 117.29 kg, respectively). The 80.95% pregnancy rate of the CS cows was higher than the 57.14 % of SS cows. After 42 days of mating, 80.95% of the CS primiparous cows had conceived, against just 28.57% from the SS. Primiparous cows at 24/25 months old and that will get pregnant have higher BW and BCS at beginning of the mating than the open ones.

O experimento conduzido na Fazenda Rancho Santa Zelina, em Júlio de Castilhos, RS, entre julho de 2014 a setembro de 2015, analisou o desempenho reprodutivo de 42 vacas mestiças Angus primíparas aos 24/25 meses de idade postas no pós-parto em pastagem cultivada de aveia (Avena strigosa Schreb) e azevém (Lolium multiflorum Lam.). Aos 80 dias pós-parto foram distribuídas conforme peso (PC) e escore de condição corporal (ECC) em dois sistemas alimentares: SS – mantidas por 23 dias na pastagem cultivada e sete dias em pastagem natural; CS – mantidas por 23 dias na pastagem cultivada e sete dias em pastagem natural com a suplementação diária de 0,8% do PC de suplemento contendo 14% proteína bruta (PB) e 70% de nutrientes digestíveis totais (NDT). O método de pastoreio foi o contínuo com massa de forragem (MF) média de 1450 kg/ha de matéria seca (MS) em pastagem cultivada e 2150 kg/ha/MS em pastagem natural. O delineamento experimental foi o inteiramente casualizado, com dois sistemas alimentares e vinte e uma vacas por sistema alimentar, sendo cada vaca considerada uma unidade experimental. Para comparar os sistemas alimentares, as variáveis que apresentaram normalidade foram avaliadas utilizando o procedimento MIXED do SAS. A variável taxa de prenhez foi avaliada pelo teste do qui-quadrado. A suplementação não influenciou o peso (PCFT) e condição corporal final (ECCFT) das vacas, porém a variação de peso diária média das vacas do CS foi superior a das em SS durante os sistemas alimentares (0,465 kg e 0,227 kg, respectivamente). Os bezerros do CS nesse período apresentaram maior ganho médio diário, 0,829 kg comparado com aqueles do SS de 0,644 kg e maior peso final (130,86 kg e 117,29 kg, respectivamente). As vacas do CS tiveram a significativa maior taxa de prenhez de 80,95%, enquanto as do SS tiveram 57,14%. Aos 42 dias de acasalamento 80,95% das vacas do CS estavam prenhes, enquanto do SS apenas 28,57% já tinham concebido. Vacas primíparas aos 24 meses de idade e que irão conceber têm maior peso e escore de condição corporal ao início do acasalamento do que as futuras falhadas. / The experiment was conducted at the Farm Rancho Santa Zelina in Julio de Castilhos, RS, from July 2014 to September 2015, examined the reproductive performance of 42 crossbred cows Angus gilts to 24/25 months old put postpartum in cultivated pasture oat (Avena strigosa Schreb) and ryegrass (Lolium multiflorum Lam.). After 80 days postpartum were distributed as weight (BW) and body condition score (BCS) in two food systems:SS – 23 days in a cultivated pasture (Avena strigosa Schreb. e Lolium multiflorum Lam.) and 7 days in a natural grassland; CS – 23 days in the same cultivated pasture and 7 days in a natural grassland receiving 0,8% BW supplement with 14% crude protein (CP) and 70% total digestible nutrients (TDN). The grazing method was continuous with herbage mass (MF) average of 1450 kg/ha of dry matter (DM) in cultivated pasture and 2150 kg/ha/DM in natural pasture. Treatments were arranged in a completely randomized design with two food systems and twenty-one cows for feeding system, where each cow was considered an experimental unit. To compare the food systems, variables with normal distribuition were assessed using the SAS MIXED procedure. The pregnancy rate was evaluated using the chi-square test. Supplementation did not affect cows‟ final body weight (FBW) and final body condition (FBC), but the daily average weight variation of cows in CS was higher than in SS (0.465 kg and 0.227 kg, respectively). The CS calves this period had higher average daily gain, 0.829 kg compared to those of the SS 0.644 kg and higher final weight (130.86 kg and 117.29 kg, respectively). The 80.95% pregnancy rate of the CS cows was higher than the 57.14 % of SS cows. After 42 days of mating, 80.95% of the CS primiparous cows had conceived, against just 28.57% from the SS. Primiparous cows at 24/25 months old and that will get pregnant have higher BW and BCS at beginning of the mating than the open ones.

Thesis(M.S.)--Auburn University, 2005. / Abstract. Vita. Includes bibliographic references.