Venancio Edward Imbayarwo-Chikosi

Estimation of Genetic and Phenotypic Parameters for Production Traits and Somatic Cell Count for Jersey Dairy Cattle in Zimbabwe

Genetic and phenotypic parameters for production traits and somatic cell count (SCC) for Jersey dairy cattle in Zimbabwe were estimated. A total of 10986 lactation records were obtained from Zimbabwe Livestock Identification Trust, with cows calving in the period from 1996 to 2008. An ASReml program fitting an animal model was used for the analyses. Heritability estimates for milk yield, fat yield, protein yield, fat percentage, protein percentage, and Log10SCC were 0.30, 0.32, 0.33, 0.42, 0.44, and 0.08, respectively. The corresponding repeatability estimates were 0.39, 0.38, 0.39, 0.49, 0.51, and 0.16, respectively. The genetic and phenotypic correlations between different production traits ranged from −0.86 to 0.95 and from −0.88 to 0.98, respectively. The genetic and phenotypic correlations between production traits and Log10SCC were weak almost nonsignificantly differentl from zero. The results imply that milk traits for Jersey dairy cattle in Zimbabwe are more heritable. Therefore, these traits may be preferred by breeders as selection criteria for development of effective genetic improvement programme.

The potential of replacing conventional dairy supplements with forage legume-based diets in Zimbabwe’s smallholder dairy sector

The effect of replacing commercial supplements with isoenergetic and isonitrogenous velvet bean-, cowpeaand lablab-based supplements on milk yield, milk quality and economic returns in smallholder crossbred dairy cows was investigated in the 2013 and 2014 dry seasons. Using 3 × 3 Latin square designs, nine multiparous Red Dane, Guernsey and Holstein-Friesian crosses in mid-lactation (130 ± 19 d) were offered forage legume-based supplements for 63 d at 0.5 kg per litre of milk produced. Milk quantity and quality were significantly (P < 0.05) different among supplements in both seasons. Cows fed commercial supplements had higher milk yield than cows fed forage legume supplements. Milk fat content was significantly (p < 0.05) higher in cows fed lablab-based supplements than cows fed other supplements. Milk protein, total solids and lactose content of cows fed commercial supplements was significantly (p < 0.05) higher than those fed forage legume-based supplements, although protein content was similar to cows fed lablab-based supplements. Dietary gross margins were higher for cows fed velvet beanand lablab-based supplements by 17% and 16.5%, respectively. Based on supplement, production costs per litre of milk was higher by 28% and 23% using commercial supplements compared to velvet bean and lablab supplements, respectively.

A Proposed Selection Index for Jersey Cattle in Zimbabwe

A multitrait selection index (I T) for Zimbabwean Jersey cattle was constructed. The breeding objective was defined in terms of production and functionality traits. The production component of the index included milk yield (M), butterfat yield (F), protein yield (P), butterfat percent (F%), and protein percent (P%), while the functional component included the somatic cell count (SCC). The index was termed as I T = 0.0004M + 0.0109F + 0.0313P + 1.0004F% + 2.4491P% − 0.1905SCC. The accuracy of the index was 91.1%, and the correlation between this index and the aggregate breeding objective was 0.954. A selection index is more important in the selection of sires and cows. This leads to the greatest genetic progress and hence productivity in the dairy sector. Therefore, the application of the selection index developed is necessary if the dairy cattle industry is to maximise the exploitation of genetics and to improve its relative competitive position.

A Comparative Evaluation of Carcass Quality, Nutritional Value, and Consumer Preference of Oreochromis niloticus from Two Impoundments with Different Pollution Levels in Zimbabwe

The objective of the study was to determine the quality and consumer preferences of Nile tilapia (Oreochromis niloticus) from two water bodies with different pollution levels and trophic states. Water quality assessment of the two impoundments was carried out. Fish were sampled from hypereutrophic Lake Chivero and oligomesotrophic Lake Kariba for proximate analysis, carcass quality, and sensory evaluation. Conductivity, dissolved oxygen, transparency, ammonia, total phosphates, reactive phosphates, and chlorophyll a were significantly different (P<0.05). Fish from Lake Kariba had significantly higher condition factors and lower fillet yields, while fish of length 10-20 cm, from Lake Chivero had significantly more fat. Lake Chivero fish were darker, greener, and less red while Lake Kariba fish were lighter, less green, and less red. Raw fish from Lake Kariba were significantly firmer, were less green and redder, had a stronger typical fish odour, and were more acceptable than Lake Chivero fish. Lake Chivero fish had a stronger foreign fish odour than their counterparts. No statistical differences were observed on fillet cooking losses, cooked fish sensory parameters, and acceptability. The fish could, however, not be safe due to possibility of toxins in water and feed (algae) which may bioaccumulate and ultimately affect other attributes of fish quality.

Promoting the use of home-mixed supplements as alternatives to commercial supplements in smallholder beef production systems in the subhumid region of Zimbabwe

The economic and performance effect of supplementing smallholder cattle by substituting commercial feed with iso-nitrogenous and iso-energetic diets based on alternative protein sources was investigated in two trials. In trial 1, three diets (commercial concentrate, commercial concentrate partially substituted with mucuna, and commercial concentrate partially substituted with lablab–cowpea) compared with veld grass were allocated to 12 cattle in a complete randomised block design. In trial 2, a double complete randomised block design with 40 cattle assigned to four forage legume-based diets, a poultry-based diet and a commercial beef concentrate was carried out. Diets were offered at 1.5% of body weight daily over 56 d. Average daily weight gain (ADWG) was measured weekly in trial 1 and fortnightly in trial 2. In trial 1, ADWG was significantly (p < 0.05) higher for animals on supplements compared with non-supplemented cattle. In trial 2, ADWG was significantly highest on the groundnut stover-based diet and least on the poultry litter diet. Supplementation had a positive effect on ADWG and economic performance of smallholder beef cattle. Substitution of commercial concentrates with alternative protein sources reduced diet costs and significantly improved gross margins.

Storage quality and marketability potential of bagged silage for smallholder dairy farmers in Zimbabwe

Bagged sole maize and maize–cowpea silages in three bag sizes were assessed at 42 and 282 d post-ensiling for sensory and chemical quality. A survey of dairy farmers on silage use and preferences was conducted in the Chikwaka communal area and Marirangwe small-scale commercial farming area. Only silage dryness changed with time. Percentage neutral detergent fibre significantly changed in 20 kg bags from 58.1 ± 0.75% at 42 d to 52.3 ± 0.86% at 282 d and in 10 kg maize–cowpea bags from 48.6 ± 0.75% to 56.0 ± 0.86%. Percentage crude protein significantly decreased (P < 0.05) for 15 kg (11.8 ± 0.30% to 9.4 ± 0.35%) and 20 kg bags (11.4 ± 0.30% to 8.9 ± 0.35%) for maize– cowpea. All 45 farmers surveyed knew about silage and 90% were feeding it to cows, 53% were making their own and 37% purchased silage. Challenges in making silage included unavailability of forage choppers, lack of requisite resources and inadequate knowledge. Silage unavailability and difficulties in transportation and storage resulted in a low frequency of silage purchases. There was no association (χ2 0.18; P > 0.05) between farming system and farmers’ willingness to buy or sell silage, and larger bags were preferred (χ2 78.96; P < 0.05). Computed silage costs per tonne were farm-produced sole maize US

Comparative evaluation of non-genetic factors affecting milk yield and composition of Red Dane and Jersey cattle in Zimbabwe

57.54, maize–cowpea US

Comparative analysis of hatching rates and clutch sizes of Nile crocodile (Crocodylus niloticus) eggs collected on- and off-farm in Zimbabwe

58.59 and bought-in sole maize US

Production and economic performance of F1-crossbred dairy cattle fed non-conventional protein supplements in Zimbabwe

89.80.

Genetic trends production and somatic cell count for Jersey cattle in Zimbabwe born from 1994 to 2005

A study was carried out to evaluate non genetic factors affecting milk yield and milk composition in Zimbabwean Red Dane and Jersey cattle cattle. A total of 1004 and 10 986 unedited Red Dane and Jersey 305-day lactation records respectively, were obtained from Livestock Identification Trust (LIT) containing 22 herds (1 Red Dane herd and 21 Jersey herds), with Red Dane calving in the period 2004 to 2009 (giving year of birth from 1998 to 2007) and Jersey cows calving in the period 1996 to 2008 (giving year of birth from 1994 to 2005). The General Linear Model (GLM) procedure of the Statistical Analysis System (SAS, 2004) version 9.1.3 was used to determine the genetic parameters and environmental factors. Calving interval, month of calving, parity and quadratic effects of age at calving fitted as covariates significantly (P < 0.0001) affected the milk, fat and protein yields. Milk, fat and protein yields obtained increased with an increase in calving interval. There was a linear and quadratic relationship between the production traits and age at calving of the Jersey cattle implying that milk, fat and protein yields increase with age of the animal. It is thus important to preadjust data for these environmental factors when carrying out genetic evaluations of production traits in dairy cattle.